Genetic

approaches

to

human

renal

agenesis/hypoplasia

and

dysplasia

Congenital

abnormalities

of

the

kidney

and

urinary

tract

are

frequently

observed

in

children

and

represent

a

significant

cause

of

morbidity

and

mortality

These

conditions

are

phenotypically

variable

often

affecting

several

segments

of

the

urinary

tract

simultaneously

making

clinical

classification

and

diagnosis

difficult

Renal

agenesis/hypoplasia

and

dysplasia

account

for

a

significant

portion

of

these

anomalies

and

a

genetic

contribution

to

its

cause

is

being

increasingly

recognized

Nevertheless

overlap

between

diseases

and

challenges

in

clinical

diagnosis

complicate

studies

attempting

to

discover

new

genes

underlying

this

anomaly

Most

of

the

insights

in

kidney

development

derive

from

studies

in

mouse

models

or

from

rare

syndromic

forms

of

human

developmental

disorders

of

the

kidney

and

urinary

tract

The

genes

implicated

have

been

shown

to

regulate

the

reciprocal

induction

between

the

ureteric

bud

and

the

metanephric

mesenchyme

Strategies

to

find

genes

causing

renal

agenesis/hypoplasia

and

dysplasia

vary

depending

on

the

characteristics

of

the

study

population

available

The

approaches

range

from

candidate

gene

association

or

resequencing

studies

to

traditional

linkage

studies

using

outbred

pedigrees

or

genetic

isolates

to

search

for

structural

variation

in

the

genome

Each

of

these

strategies

has

advantages

and

pitfalls

and

some

have

led

to

significant

discoveries

in

human

disease

However

renal

agenesis/hypoplasia

and

dysplasia

still

represents

a

challenge

both

for

the

clinicians

who

attempt

a

precise

diagnosis

and

for

the

geneticist

who

tries

to

unravel

the

genetic

basis

and

a

better

classification

requires

molecular

definition

to

be

retrospectively

improved

The

goal

appears

to

be

feasible

with

the

large

multicentric

collaborative

groups

that

share

the

same

objectives

and

resources

Introduction

and

definition

Congenital

abnormalities

of

the

kidney

and

urinary

tract

are

frequently

observed

in

the

first

year

of

life

when

they

collectively

represent

a

significant

cause

of

morbidity

-LSB-

-RSB-

and

mortality

Data

from

birth

defects

registries

-LSB-

Metropolitan

Atlanta

Congenital

Defects

Program

-LRB-

MACDP

-RRB-

California

Birth

Defects

Monitoring

Program

-LRB-

CBDMP

-RRB-

-LSB-

-RSB-

indicate

an

overall

frequency

from

three

to

six

per

births

and

the

abnormalities

seriously

impact

life

expectancy

-LRB-

-RRB-

Human

urinary

tract

abnormalities

are

phenotypically

variable

and

may

affect

several

segments

simultaneously

often

aggregating

to

form

complex

phenotypes

Hence

clinical

classification

and

diagnosis

may

be

difficult

As

a

consequence

of

the

overlap

between

anatomical

defects

many

investigators

have

opted

to

group

renal

and

urologic

malformations

under

the

single

label

of

Congenital

Anomalies

of

the

Kidney

and

Urinary

Tract

-LRB-

CAKUT

-RRB-

-LSB-

-RSB-

This

broad

classification

is

supported

by

the

fact

that

a

mutation

in

a

single

gene

can

have

pleiotropic

effects

on

the

development

of

the

urogenital

tract

For

example

mutations

in

the

gene

cause

the

renal-coloboma

syndrome

but

the

clinical

features

of

the

trait

vary

significantly

between

affected

individuals

ranging

from

renal

agenesis/hypoplasia

to

vesicoureteral

reflux

-LRB-

VUR

-RRB-

and

secondary

obstruction

-LSB-

-RSB-

Conversely

mutations

in

different

genes

can

result

in

similar

renal

phenotypes

e.g.

and

mutations

both

can

cause

the

development

of

hypoplastic

kidneys

-LSB-

-RSB-

Hence

improved

classification

of

urinary

tract

malformations

may

require

understanding

of

primary

molecular

defects

A

broad

but

clinically

useful

diagnostic

scheme

consists

of

classifying

malformations

depending

on

whether

the

kidney

the

collecting

system

or

both

are

affected

This

scheme

stems

from

the

fact

that

the

upper

tract

-LRB-

glomeruli

and

tubules

-RRB-

is

derived

from

the

metanephric

mesenchyme

-LRB-

MM

-RRB-

and

the

lower

urinary

tract

-LRB-

collecting

duct

renal

pelvis

ureter

-RRB-

is

derived

from

the

ureteric

bud

-LSB-

-RSB-

Even

if

this

is

in

contrast

with

more

recent

data

about

the

reciprocal

interaction

between

the

ureteric

bud

and

the

MM

-LRB-

see

below

-RRB-

this

classification

can

be

clinically

useful

to

partition

patients

with

different

types

of

urinary

tract

abnormalities

In

this

review

we

focus

on

the

malformations

that

primarily

involve

a

reduction

of

renal

parenchyma

in

the

form

of

renal

agenesis

and/or

hypoplasia/dysplasia

occurring

both

as

isolated

forms

or

in

association

with

other

malformations

of

the

lower

urinary

tract

-LRB-

see

below

-RRB-

Primary

renal

agenesis

Bilateral

renal

agenesis

is

a

rare

and

fatal

event

usually

associated

with

severe

oligohydramnios

which

produces

a

characteristic

clinical

pattern

with

facial

compression

and

pulmonary

hypoplasia

-LRB-

Potter

syndrome

-RRB-

An

estimate

of

the

incidence

of

bilateral

agenesis

is

births

Unilateral

renal

agenesis

is

more

common

although

the

frequency

is

difficult

to

estimate

as

it

is

usually

clinically

silent

and

is

commonly

detected

as

a

chance

observation

by

autopsy

or

by

prenatal

ultrasound

-LSB-

-RSB-

Primary

renal

hypoplasia

and

dysplasia

Strictly

speaking

renal

hypoplasia

is

defined

as

a

small

kidney

which

contains

intact

nephrons

that

are

reduced

in

number

whereas

a

dysplastic

kidney

contains

disorganized

elements

and

maldifferentiated

tissue

Noninvasive

imaging

studies

such

as

ultrasounds

and

dimercaptosuccinic

acid

-LRB-

DMSA

-RRB-

scan

offer

limited

information

to

help

distinguish

a

hypoplastic

kidney

from

a

dysplastic

one

Unequivocal

distinction

between

these

two

entities

therefore

depends

on

histological

examination

of

renal

tissue

obtained

from

kidney

biopsy

or

surgical

nephrectomy

which

are

rarely

performed

A

further

confounding

factor

is

the

reduction

of

kidney

size

due

to

chronic

injury

and

scarring

from

VUR

Most

of

the

time

a

DMSA

scan

helps

differentiate

primary

hypoplasia

or

dysplasia

from

small

kidneys

secondary

to

VUR

However

a

DMSA

scan

has

a

low

negative

predictive

value

in

distinguishing

primary

hypoplasia

or

dysplasia

from

a

secondary

reduction

in

kidney

size

from

VUR

when

scars

or

areas

of

negative

isotope

uptake

are

present

In

practice

the

diagnosis

of

primary

renal

hypoplasia

is

favored

when

the

following

criteria

are

satisfied

-LRB-

a

-RRB-

a

reduction

of

renal

size

by

standard

deviations

-LRB-

SDS

-RRB-

from

the

mean

size

for

the

age

-LRB-

b

-RRB-

exclusion

of

renal

scarring

by

DMSA

scan

and

-LRB-

c

-RRB-

a

presence

of

compensatory

hypertrophy

of

the

contralateral

kidney

In

all

cases

the

exclusion

of

renal

cysts

by

ultrasonography

is

mandatory

to

avoid

confusion

with

primary

renal

hypoplasia

associated

with

fibrosis

and

cysts

nephronophthisis

being

the

most

pertinent

example

The

presence

of

VUR

and/or

ureteropelvic

junction

obstruction

-LRB-

UPJO

-RRB-

does

not

automatically

exclude

the

diagnosis

of

hypoplasia

as

both

conditions

are

frequently

associated

with

primary

renal-size

defects

It

is

clear

that

this

problem

is

difficult

to

resolve

if

the

ureteral

defect

presents

ipsilateral

to

renal

hypoplasia

For

example

severe

antenatal

hydronephrosis

due

to

UPJO

can

determine

the

involution

of

the

renal

parenchyma

and

lead

to

an

erroneous

diagnosis

of

primary

renal

agenesis

after

birth

In

bilateral

cases

syndromic

traits

as

well

as

inherited

disorders

such

as

medullary

cystic

kidney

disease/nephronophthisis

have

to

be

excluded

Unequivocal

exclusion

of

renal

dysplasia

is

usually

not

feasible

except

in

rare

cases

for

which

histology

is

available

It

is

possible

that

in

the

near

future

molecular

genetic

advances

could

modify

our

present

understanding

and

allow

for

a

more

direct

separation

of

the

two

pathological

entities

based

on

laboratory

tests

These

challenges

in

clinical

diagnosis

of

renal

hypoplasia

complicate

studies

attempting

to

discover

new

genes

underlying

this

anomaly

For

research

purposes

we

utilize

a

tentative

classification

scheme

for

categorizing

our

subjects

for

genetic

studies

-LRB-

-RRB-

isolated

bilateral

hypoplasia/dysplasia

-LRB-

-RRB-

isolated

unilateral

hypoplasia/dysplasia

and

-LRB-

-RRB-

hypoplasia/dysplasia

associated

with

lower

tract

abnormalities

such

as

VUR

or

UPJO

Once

the

genetic

basis

of

different

subsets

of

urinary

tract

malformations

is

identified

the

classification

will

likely

be

retrospectively

changed

and

improved

Kidney

development

and

mouse

models

The

development

of

mammalian

kidney

derives

from

reciprocally

inductive

events

between

two

tissue

compartments

of

the

embryonic

metanephros

the

ureteric

bud

-LRB-

UB

-RRB-

an

outgrowth

of

the

nephric

duct

and

the

MM

The

ureteric

bud

invades

the

metanephric

blastema

at

embryonic

day

in

the

mouse

and

in

humans

The

MM

induces

the

ureteric

bud

to

grow

and

branch

while

the

ureteric

bud

induces

the

MM

to

transdifferentiate

and

form

the

nephrons

epithelia

-LRB-

see

recent

reviews

in

kidney

development

in

human

and

mice

-LSB-

-RSB-

-RRB-

In

recent

years

many

factors

specific

for

either

the

UB

or

the

MM

have

been

demonstrated

to

induce

and

regulate

the

epithelial

conversion

in

the

mesenchymal

cells

and

the

UB

branching

leading

to

the

development

of

the

final

structure

and

function

of

the

kidney

Most

data

constituting

the

basis

of

our

current

knowledge

on

the

topic

are

based

on

gene

targeting

studies

in

mice

-LRB-

Table

-RRB-

A

partial

list

of

genes

includes

protooncogenes

RET

and

Wingless-related

-LRB-

-RRB-

that

are

well

recognized

UB-specific

molecules

whereas

glial

cell-line-derived

neurotrophic

factor

-LRB-

GDNF

-RRB-

Wilms

tumor

-LRB-

-RRB-

and

Eyes

absent

-LRB-

-RRB-

represent

important

examples

of

MM-specific

factors

The

paired-box

gene

-LRB-

-RRB-

appears

to

be

expressed

in

both

structures

during

kidney

development

-LSB-

-RSB-

It

is

noteworthy

that

almost

half

of

the

genes

on

the

list

are

transcriptional

factors

or

encode

for

proteins

that

are

involved

in

the

mesenchymal

to

epithelial

conversion

GDNF

signaling

through

the

RET

receptor

is

one

of

the

best

studied

pathways

representing

a

critical

step

in

the

normal

growth

and

branching

of

the

UB

during

kidney

development

-LSB-

-RSB-

Perturbation

of

Gdnf/Ret

signaling

has

been

shown

to

be

the

downstream

mechanism

underlying

impaired

nephrogenesis

in

many

other

mutant

models

-LRB-

e.g.

in

and

mice

-RRB-

Numerous

factors

other

than

the

Gdnf/Ret

pathway

also

participate

in

kidney

and

urologic

development

-LRB-

e.g.

Wnt

signaling

-RRB-

as

evidenced

by

the

long

list

of

mutant

mice

with

malformations

in

the

kidney

and

urologic

tract

-LRB-

Table

-RRB-

Table

genes

targeted

in

mice

leading

to

renal

agenesis

hypoplasia

dysplasiaGeneHuman

homologKidney

fused

undifferentiated

kidneysHatini

et

al.

-LSB-

-RSB-

kidneysJohnson

et

al.

-LSB-

-RSB-

Xu

et

al.

-LSB-

-RSB-

kidneysMiyamoto

et

al.

-LSB-

-RSB-

or

absent

kidneysDavis

et

al.

-LSB-

-RSB-

kidneysShawlot

and

Behringer

-LSB-

-RSB-

or

absent

kidneysTorres

et

al.

-LSB-

-RSB-

kidneysKreidberg

et

al.

-LSB-

-RSB-

urinary

tract

malformationsNishimura

et

al.

-LSB-

-RSB-

ureteric

bud

-LRB-

UB

-RRB-

branchingMiyazaki

et

al.

-LSB-

-RSB-

nephrogenesisDudley

et

al.

-LSB-

-RSB-

kidneysStark

et

al.

-LSB-

-RSB-

RetRETAbsent

kidneys

severe

dysgenesisSchuchardt

et

al.

-LSB-

-RSB-

GdnfGDNFAbsent

kidneys

severe

dysgenesisSanchez

et

al.

-LSB-

-RSB-

Moore

et

al.

-LSB-

-RSB-

Pichel

et

al.

-LSB-

-RSB-

kidneysXu

et

al.

-LSB-

-RSB-

kidneysSelf

et

al.

-LSB-

-RSB-

kidneysNishinakamura

et

al.

-LSB-

-RSB-

kidneysPoladia

et

al.

-LSB-

-RSB-

or

absent

kidneysLiu

et

al.

-LSB-

-RSB-

or

absent

kidneysSchnabel

et

al.

-LSB-

-RSB-

kidneysPerantoni

et

al.

-LSB-

-RSB-

kidneysMendelsohn

et

al.

-LSB-

-RSB-

kidneysKobayashi

et

al.

-LSB-

-RSB-

The

interdependence

between

developmental

pathways

explains

why

defects

in

different

genes

result

in

similar

phenotypes

and

why

morphologic

classification

of

abnormalities

alone

can

not

predict

the

location

or

nature

of

primary

defects

Available

data

thus

suggest

a

large

list

of

candidate

genes

for

human

renal

and

urologic

malformations

highlighting

the

potential

for

genetic

heterogeneity

of

the

trait

Genetic

contribution

to

human

renal

agenesis/hypoplasia

and

dysplasia

A

genetic

contribution

to

the

development

of

renal

hypoplasia/dysplasia

has

been

recognized

for

many

years

For

the

isolated

nonsyndromic

renal

agenesis/hypoplasia

and

dysplasia

only

segregation

studies

have

been

performed

and

no

loci

and/or

genes

have

been

mapped

so

far

Much

more

is

known

about

rare

syndromic

forms

for

which

several

genes

have

been

already

implicated

Syndromic

forms

Syndromic

forms

of

renal

hypoplasia/dysplasia

include

rare

disorders

affecting

extrarenal

organs

such

as

the

eye

the

central

nervous

system

the

skin

the

limbs

and

others

The

list

of

syndromes

that

include

the

renal

agenesis/hypoplasia/dysplasia

phenotype

consists

of

at

least

clinical

conditions

-LRB-

for

more

details

see

Limwongse

and

Cassidy

-LSB-

-RSB-

-RRB-

Several

genes

underlying

these

defects

having

been

identified

-LRB-

Table

-RRB-

Renal-coloboma

syndrome

orofaciodigital

syndrome

branchiootorenal

syndrome

renal

cysts

and

diabetes

syndrome

and

Fraser

syndrome

are

the

most

frequent

syndromes

associated

with

renal

parenchymal

defects

It

seems

clinically

relevant

that

the

renal

abnormalities

may

represent

the

first

manifestation

of

the

disease

thus

requiring

a

detailed

evaluation

of

other

organs

A

list

of

extrarenal

signs

and

symptoms

that

clinicians

should

look

for

to

define

these

syndromes

include

retinal

coloboma

-LSB-

-RSB-

deafness

external

ear

abnormalities

including

cysts

and

fistulas

-LSB-

-RSB-

anus

imperforates

and

limb

and

ear

anomalies

-LSB-

-RSB-

diabetes

and

renal

cystic

dysplasia

-LSB-

-RSB-

and

others

Finally

renal

agenesis/hypoplasia

is

frequently

part

of

chromosomal

disorders

-LRB-

Table

-RRB-

that

must

be

recognized

for

genetic

counseling

Most

common

syndromes

that

should

be

considered

in

the

initial

differential

diagnosis

are

listed

in

Tables

and

and

we

suggest

referring

to

popular

Web

sites

for

further

details

-LRB-

links

provided

at

the

end

-RRB-

Table

of

human

malformation

syndromes

with

kidney

hypoplasia/dysplasiaGeneHuman

syndromeKidney

syndromeMCDK

kidney

dysplasia

kidney

mesangiolipidosis

syndromeRenal

dysplasia

and

calyceal

malformations

syndromeRenal

agenesis/dysplasia

dysplasiaDiverse

renal

malformations

syndromeDiverse

urinary

tract

malformations

George

syndromeRenal

agenesis

dysplasia

VUR

sensorial

deafness

renal

anomalies

-LRB-

HDR

-RRB-

Renal

agenesis

dysplasia

VUR

repairFanconi

anemiaRenal

agenesis

syndromeRenal

agenesis

dysplasia

's

syndromeRenal

agenesis

dysplasia

coloboma

syndromeRenal

hypoplasia

MCDK

VUR

cysts

and

diabetes

syndromeRenal

dysplasia

cysts

syndromeRenal

dysplasia

cysts

syndromeRenal

dysplasia

cysts

syndromeRenal

dysplasia

lower

urinary

tract

malformations

syndromeGlomerulus

malformation

renal

agenesis

de

Lange

syndromeRenal

dysplasia

syndromeRenal

agenesis

syndromeRenal

agenesis

syndromeRenal

dysplasia

cysts

syndromeRenal

agenesis

dysplasia

-LRB-

-RRB-

Beckwith-Wiedemann

syndromeRenal

dysplasia

syndromeRenal

ectopia

with

or

without

fusion

lower

urinary

tract

malformations

syndromeRenal

agenesis

multicystic

dysplastic

kidney

VUR

vesicoureteral

refluxTable

chromosomal

disorders

associated

with

urinary

tract

anomaliesChromosomal

disordersRenal

agenesisHypoplasiaOther

associated

anomaliesPatau

syndrome

-LRB-

trisomy

-RRB-

Holoprosencephaly

midline

anomalies

cleft

lip/palateMiller-Dieker

syndrome

-LRB-

deletion

-RRB-

MR

lissencephaly

microgyria

agyria

typical

facie

seizuresEdward

syndrome

-LRB-

trisomy

-RRB-

deletion

IUGR

CHD

clenched

hands

rocker

bottom

feet

SS

MR

microcephaly

narrow

external

ear

canals

long

handsDown

syndrome

-LRB-

trisomy

-RRB-

MR

hypotonia

CHD

typical

face

clinodactylyCateye

syndrome

-LRB-

tetrasomy

-RRB-

MR

CHD

colobomas

anal/digital

anomaliesVelocardiofacial

syndrome

-LRB-

deletion

-RRB-

Conotruncal

CHD

thymic

aplasia

typical

face

cleft

palateTurner

syndrome

-LRB-

X

or

X

i

-LRB-

Xq

-RRB-

-RRB-

SS

amenorrhea

webbed

neck

cubitus

valgus

hypogonadismMR

mental

retardation

IUGR

intrauterine

growth

retardation

CHD

congenital

heart

disease

SS

short

stature

Nonsyndromic

forms

It

is

well

known

that

nonsyndromic

renal

malformations

may

occur

as

hereditary

traits

and

can

present

with

familial

aggregation

Evidence

in

favor

of

a

genetic

determination

of

the

disease

is

raised

by

an

increased

recurrence

risk

among

first-degree

relatives

and

by

several

reports

of

familial

occurrence

of

multiple

malformations

including

renal

agenesis/hypoplasia

and

dysplasia

The

relative

recurrence

risk

of

bilateral

and

unilateral

agenesis

has

been

estimated

at

-LSB-

-RSB-

For

familial

cases

in

most

of

the

pedigrees

the

suggested

mode

of

inheritance

was

autosomal

dominant

with

reduced

penetrance

estimated

to

range

between

and

-LSB-

-RSB-

For

example

a

large

pedigree

with

an

autosomal

dominant

mode

form

of

nonsyndromic

renal

hypoplasia

and

dysplasia

has

recently

been

described

-LSB-

-RSB-

However

a

Somalian

kindred

in

which

the

trait

was

segregating

in

an

autosomal

recessive

fashion

has

been

reported

-LSB-

-RSB-

Nevertheless

until

recently

no

linkage

studies

in

familial

renal

agenesis/hypoplasia

and

dysplasia

have

been

reported

Incomplete

penetrance

variable

expression

and

the

fact

that

anatomical

defects

in

many

family

members

can

be

clinically

silent

complicate

recruitment

of

large

pedigrees

that

would

be

suitable

for

linkage

analysis

Strategies

for

gene

discovery

Strategies

to

find

genes

causing

renal

agenesis/hypoplasia

and

dysplasia

vary

significantly

depending

on

the

characteristics

of

the

study

population

available

Different

data

sets

of

patients

have

potential

advantages

and

possible

pitfalls

Candidate

gene

studies

So

far

candidate

gene

studies

have

been

the

only

alternative

to

linkage

analysis

to

find

genes

underlying

both

Mendelian

and

complex

traits

Such

studies

have

identified

many

genes

causing

rare

genetic

diseases

-LSB-

-RSB-

-LRB-

The

Human

Gene

Mutation

Database

-RRB-

and

most

of

the

genes

that

are

known

contribute

to

susceptibility

to

common

diseases

-LSB-

-RSB-

Large

cohorts

of

sporadic

cases

or

small

pedigrees

can

be

utilized

in

case-control

association

studies

to

find

common

disease

associated

alleles

Such

cohorts

can

also

be

screened

by

resequencing

of

candidate

genes

to

detect

rare

variants

with

large

effects

that

account

for

disease

in

a

small

proportion

of

the

patients

Selection

of

one

approach

over

the

other

depends

on

the

expected

degree

of

genetic

and

allelic

heterogeneity

of

the

trait

under

investigation

Genetic

heterogeneity

refers

to

the

situation

where

mutations

in

different

genes

account

for

disease

in

different

affected

individuals

Allelic

heterogeneity

refers

to

the

presence

of

many

independent

mutations

in

a

given

gene

For

a

trait

with

high

locus

and

allelic

heterogeneity

the

search

for

common

disease-contributing

alleles

is

problematic

and

resources

would

be

better

directed

toward

comprehensive

resequencing

of

candidate

genes

to

discovery

the

rare

disease-causing

variants

In

practice

the

heterogeneity

parameters

are

difficult

to

predict

a

priori

The

resequencing

approach

has

been

successfully

applied

to

find

several

genes

causing

kidney

developmental

disorders

As

an

example

mutations

in

the

uroplakin

III

gene

which

produce

VUR

in

mice

-LSB-

-RSB-

explain

a

small

fraction

of

human

renal

hypodysplasia

-LSB-

-RSB-

Similarly

results

from

the

ESCAPE

study

recently

provided

the

first

comprehensive

analysis

of

renal

developmental

genes

in

children

affected

by

nonsyndromic

renal

hypodysplasia

showing

a

fairly

high

prevalence

of

and

mutations

-LSB-

-RSB-

Another

success

of

the

candidate

gene

approach

is

the

latest

discovery

of

mutations

in

genes

of

the

renin-angiotensin

system

-LRB-

RAS

-RRB-

in

severe

forms

of

renal

tubular

dysgenesis

-LSB-

-RSB-

The

search

for

common

variants

predisposing

to

nonsyndromic

renal

hypodysplasia

has

not

been

frequently

applied

However

these

common

predisposing

alleles

may

not

be

recognized

until

a

comprehensive

search

is

undertaken

As

an

example

a

common

noncoding

variant

in

a

RET

enhancer

has

recently

been

shown

to

be

a

strong

risk

allele

for

Hirschsprung

disease

explaining

the

paucity

of

coding

mutations

found

in

families

showing

linkage

to

the

RET

locus

-LSB-

-RSB-

Traditional

linkage

studies

and

genetic

isolates

The

genome-wide

linkage

analysis/positional

cloning

approach

is

a

time-tested

method

used

to

identify

disease-causing

mutations

and

it

has

been

extremely

successful

in

the

past

few

decades

for

mapping

genes

that

underlie

monogenic

Mendelian

diseases

-LSB-

-RSB-

This

approach

hinges

on

availability

of

single

uniquely

large

pedigrees

that

segregate

genes

with

large

effect

or

a

large

number

of

small-sized

pedigrees

Mutations

in

genes

underlying

Mendelian

forms

of

disease

usually

account

for

a

fraction

of

sporadic

forms

-LRB-

e.g.

and

-RRB-

For

renal

agenesis/hypoplasia

and

dysplasia

large

pedigrees

amenable

for

linkage

analysis

are

very

difficult

to

ascertain

because

these

traits

have

incomplete

penetrance

-LRB-

due

to

genetic

and

environmental

modifiers

-RRB-

Moreover

many

malformations

such

as

unilateral

agenesis

can

be

clinically

silent

and

will

not

be

detected

without

systematic

screening

of

family

members

As

for

candidate

gene

studies

locus

heterogeneity

is

another

potentially

complicating

factor

that

may

dilute

the

power

of

linkage

studies

Our

previous

data

demonstrated

that

in

the

setting

of

reduced

penetrance

variable

expressivity

and

very

high

genetic

heterogeneity

approaches

based

on

a

limited

number

of

uniquely

large

pedigrees

or

a

very

large

number

of

medium-sized

kindreds

are

more

likely

to

be

successful

to

map

a

disease

gene

-LSB-

-RSB-

As

a

result

of

these

difficulties

no

linkage

studies

of

renal

agenesis/hypoplasia

have

been

published

so

far

These

kinds

of

patient

cohorts

are

very

arduous

to

collect

and

require

multicenter

collaborative

efforts

We

have

been

able

to

collect

seven

multigenerational

extended

pedigrees

segregating

congenital

anomalies

of

the

kidney

and

urinary

tract

including

renal

agenesis/hypoplasia

as

an

autosomal

dominant

trait

with

reduced

penetrance

trait

These

families

allowed

us

to

localize

a

gene

for

this

trait

to

a

Mb

interval

to

chromosome

in

a

setting

of

genetic

heterogeneity

-LSB-

-RSB-

This

work

represents

the

first

step

toward

the

discovery

of

a

new

gene

and

possibly

a

new

pathway

in

kidney

development

Genetic

isolates

represent

a

population

structure

that

can

greatly

facilitate

gene

identification

efforts

The

genetic

isolates

are

populations

that

are

originated

from

a

limited

group

of

founders

with

little

subsequent

immigration

into

the

population

Without

an

inflow

of

genes

a

long

period

of

time

would

be

required

for

spontaneous

mutations

to

rebuild

genetic

diversity

Therefore

genetic

isolates

are

likely

to

harbor

few

disease-contributing

alleles

that

have

been

inherited

identical

by

descent

from

common

ancestors

-LSB-

-RSB-

These

ancestral

mutations

can

be

detected

by

searching

for

a

shared

haplotype

signature

in

affected

individuals

representing

a

powerful

shortcut

to

narrow

down

a

linkage

interval

to

a

handful

of

genes

This

strategy

called

linkage

disequilibrium

-LRB-

LD

-RRB-

mapping

has

allowed

the

identification

of

several

genes

for

Mendelian

disorders

-LSB-

-RSB-

Hence

the

advantages

of

studying

a

genetic

isolate

rely

on

-LRB-

a

-RRB-

a

higher

prevalence

of

certain

diseases

allowing

traits

with

reduced

penetrance

to

express

and

show

their

hereditary

component

-LRB-

b

-RRB-

a

more

uniform

genetic

background

thus

reducing

the

genetic

heterogeneity

-LRB-

c

-RRB-

usually

good

genealogical

records

-LRB-

d

-RRB-

a

more

uniform

environment

and

-LRB-

e

-RRB-

the

possibility

of

speeding

up

gene

discovery

through

linkage

disequilibrium

mapping

We

have

recently

characterized

a

genetic

isolate

in

an

Italian

valley

in

which

different

glomerular

diseases

occurred

at

a

much

higher

prevalence

compared

with

the

general

population

in

apparently

unrelated

individuals

The

genealogical

reconstruction

allowed

us

to

reconnect

most

of

the

patients

to

a

few

founders

up

to

the

sixteenth

century

-LSB-

-RSB-

This

study

is

an

example

of

how

an

isolate

can

allow

traits

that

display

reduced

penetrance

and

variable

expressivity

to

express

their

genetic

component

and

represent

a

first

step

to

find

genes

causing

or

predisposing

to

such

diseases

Further

investigation

of

recognized

population

isolates

for

developmental

disorders

especially

renal

agenesis/hypoplasia

and

dysplasia

might

help

to

accelerate

gene

mapping

Genome-wide

association

studies

The

genome-wide

association

study

is

an

approach

aimed

at

exhaustively

covering

the

genome

to

look

for

causative

variants

Similar

to

genome-wide

linkage

studies

no

assumptions

are

made

about

either

the

location

of

the

causative

variant

or

the

biological

role

of

the

disease

gene

Therefore

this

approach

represents

an

unbiased

method

to

find

disease-causing

genes

with

also

a

very

high

probability

of

discovering

new

genes

thus

unraveling

new

pathophysiological

pathways

Genome-wide

association

studies

were

not

feasible

until

now

because

of

the

lack

of

information

about

the

variability

in

the

human

genome

and

lack

of

low-cost

high-throughput

genotyping

technology

This

situation

has

changed

in

the

past

years

dbSNP

-LRB-

-RRB-

now

contains

about

million

SNPs

including

most

of

the

SNPs

with

a

minor

allele

frequency

higher

than

estimated

to

exist

in

the

human

genome

-LSB-

-RSB-

Moreover

the

HapMap

project

-LSB-

-RSB-

represents

a

fundamental

advance

to

performing

efficient

and

successful

genome-wide

studies

through

the

determination

of

LD

patterns

and

haplotype

blocks

across

the

genome

Another

important

step

has

been

the

tremendous

improvement

in

genotyping

technology

with

the

development

of

platforms

for

fast

high-throughput

low-cost

SNPs

genotyping

Such

platforms

allow

the

simultaneous

genotyping

of

SNPs

in

a

single

assay

allowing

a

dense

coverage

of

the

human

genome

-LSB-

-RSB-

Some

examples

of

success

of

this

approach

have

been

recently

published

For

example

genome-wide

association

studies

on

patients

affected

by

age-related

macular

degeneration

allowed

the

individuation

of

a

common

variant

in

the

complement

factor

H

as

a

major

risk-associated

allele

-LSB-

-RSB-

Similarly

polymorphisms

in

the

transcription

factor

have

been

found

to

confer

risk

to

type

diabetes

in

different

populations

-LSB-

-RSB-

Whether

genome-wide

association

studies

will

lead

to

significant

discoveries

in

renal

agenesis/hypoplasia

and

dysplasia

is

still

unclear

but

certainly

this

approach

represents

a

very

promising

strategy

to

identify

common

variants

conferring

susceptibility

to

more

frequent

complex

traits

Search

for

structural

variations

in

the

genome

A

number

of

urogenital

malformations

are

associated

with

chromosomal

abnormalities

For

example

a

deletion

on

chromosome

has

been

implicated

in

urogenital

development

-LSB-

-RSB-

Similarly

two

distinct

loci

for

renal

malformations

including

VUR

have

been

mapped

to

chromosome

by

deletion

mapping

using

microsatellites

in

a

limited

number

of

affected

individuals

-LSB-

-RSB-

Advances

in

technology

mainly

genome-scanning

array

technologies

and

comparative

DNA-sequence

analyses

have

identified

a

high

prevalence

of

DNA

variations

that

involve

segments

that

are

smaller

than

those

recognized

by

standard

cytogenetics

techniques

-LSB-

-RSB-

These

structural

variations

are

a

common

feature

of

our

genomic

landscape

encompassing

deletions

duplications

inversions

and

translocations

which

range

from

a

few

bases

up

to

hundreds

of

kilobases

These

rearrangements

comprise

benign

polymorphisms

as

well

as

deleterious

mutations

that

can

disrupt

gene

structure

or

affect

gene

regulation

Newer

techniques

now

allow

for

the

identification

of

structural

variation

at

the

genome-wide

level

enabling

examination

of

single

patients

to

rapidly

define

a

chromosomal

region

-LRB-

locus

-RRB-

of

interest

Several

studies

have

already

reported

structural

variations

associated

to

human

disease

leading

in

some

cases

to

a

molecular

definition

of

a

disorder

before

a

recognized

clinical

syndrome

-LSB-

-RSB-

These

technologies

have

also

been

already

successfully

applied

to

developmental

disorders

A

genome-wide

search

for

structural

variations

using

comparative

genomic

hybridization

-LRB-

CGH

-RRB-

array

allowed

the

discovery

of

the

gene

as

a

cause

of

CHARGE

syndrome

a

rare

complex

disorder

in

which

congenital

anomalies

affect

in

a

nonrandom

fashion

several

tissues

including

the

urinary

tract

-LSB-

-RSB-

Careful

clinical

selection

of

patients

and

application

of

genome-wide

methods

for

searching

structural

variation

in

renal

agenesis/hypoplasia

and

dysplasia

can

help

find

new

loci

linked

to

the

disease

confirm

and

narrow

loci

obtained

by

linkage

analysis

and

speed

up

the

discovery

of

causative

genes

Conclusions

Renal

agenesis/hypoplasia

and

dysplasia

still

represents

a

challenge

for

both

the

clinicians

who

attempt

a

precise

diagnosis

and

for

the

geneticists

who

try

to

unravel

the

genetic

basis

Genetic

and

clinical

approaches

are

now

converging

toward

a

common

goal

which

is

the

discovery

of

genetic

markers

to

make

the

diagnosis

of

this

trait

easier

The

final

objective

is

to

improve

classification

to

make

a

reliable

prognosis

and

to

attempt

prevention

Based

on

advances

from

the

last

few

years

the

goal

appears

to

be

more

feasible

with

large

multicentric

collaborative

groups

that

share

the

same

objectives

and

resources

O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O 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O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O

gene mapping
linkage analysis
association studies

renal agenesis/hypoplasia and dysplasia
structural variants


Gender

differences

in

the

ratio

between

humerus

width

and

length

are

established

prior

to

puberty

Summary

On

a

sample

of

children

aged

years

we

developed

a

novel

method

of

measuring

humeral

dimensions

from

total

body

dual-energy

X-ray

absorptiometry

-LRB-

DXA

-RRB-

scans

and

showed

that

gender

differences

in

the

ratio

between

humeral

width

and

length

are

established

prior

to

puberty

Introduction

Traditionally

the

increased

risk

of

osteoporotic

fracture

in

women

compared

to

men

has

been

attributed

to

their

low

bone

mass

as

a

consequence

of

reduced

peak

bone

mass

acquisition

and

increased

rates

of

bone

loss

following

the

menopause

However

more

recent

studies

indicate

that

several

other

factors

influence

fracture

risk

independently

of

bone

mass

such

as

skeletal

geometry

and

the

material

properties

of

bone

-LSB-

-RSB-

Furthermore

there

are

gender

differences

in

skeletal

geometry

that

may

contribute

to

the

greater

fracture

risk

in

women

compared

to

men

For

example

long

bone

cross-sectional

area

is

greater

in

men

which

is

thought

to

reflect

higher

rates

of

periosteal

apposition

from

the

time

of

puberty

onwards

-LSB-

-RSB-

One

study

of

girls

and

boys

aged

years

who

underwent

prospective

peripheral

quantitative

computed

tomography

-LRB-

pQCT

-RRB-

measurements

reported

that

periosteal

growth

was

more

rapid

in

pubertal

boys

compared

to

girls

-LSB-

-RSB-

Skeletal

growth

is

coordinated

to

ensure

that

the

ratio

between

different

skeletal

dimensions

is

maintained

despite

rapid

changes

in

size

-LSB-

-RSB-

Therefore

it

is

possible

that

the

greater

cross-sectional

area

in

boys

compared

to

girls

is

a

reflection

of

their

larger

size

On

the

other

hand

the

ratio

between

periosteal

growth

and

longitudinal

bone

growth

may

be

different

in

boys

compared

to

girls

leading

to

gender

differences

in

bone

shape

However

little

is

known

of

the

inter-relationships

between

longitudinal

and

periosteal

bone

growth

since

investigation

of

possible

gender

differences

in

skeletal

geometry

have

generally

been

confined

to

analysis

of

cross-sectional

area

in

the

absence

of

techniques

capable

of

simultaneous

measurement

of

long

bone

length

it

has

been

difficult

to

accurately

assess

how

the

ratio

between

longitudinal

and

periosteal

growth

is

affected

by

gender

and

other

factors

such

as

puberty

Recently

we

developed

a

novel

method

for

evaluating

long

bone

geometry

based

on

analysis

of

the

humerus

on

total

body

dual-energy

X-ray

absorptiometry

-LRB-

DXA

-RRB-

scans

The

humerus

offers

important

advantages

over

other

long

bones

in

that

its

entire

outline

can

readily

be

traced

on

total

body

DXA

images

and

its

shape

can

be

modelled

as

a

cylinder

with

reasonable

accuracy

To

explore

the

utility

of

regional

DXA

analysis

at

the

humerus

volumetric

bone

density

of

the

humerus

was

derived

by

dividing

humeral

bone

mineral

content

-LRB-

BMC

-RRB-

by

estimated

humeral

cylindrical

volume

and

then

analysed

in

relation

to

fracture

risk

Interestingly

humeral

volumetric

bone

density

obtained

in

this

way

was

indeed

related

to

fracture

risk

as

analysed

in

a

subgroup

of

children

from

the

Avon

Longitudinal

Study

of

Parents

and

Children

-LRB-

ALSPAC

-RRB-

in

whom

total

body

DXA

scans

were

available

at

years

of

age

-LSB-

-RSB-

In

the

present

study

we

aimed

to

characterise

the

influence

of

gender

and

puberty

on

the

ratio

between

longitudinal

and

periosteal

growth

by

exploiting

this

novel

technique

of

humeral

geometric

analysis

In

particular

we

wished

to

determine

whether

in

analyses

combining

fracture

and

non-fracture

controls

from

the

study

described

above

gender

differences

exist

in

the

ratio

between

width

and

length

of

the

humerus

and

if

so

whether

these

differences

are

established

prior

to

puberty

Methods

Study

population

The

Avon

Longitudinal

Study

of

Parents

and

Children

-LRB-

ALSPAC

-RRB-

is

a

geographically

based

cohort

that

recruited

pregnant

women

residing

in

Avon

with

an

expected

date

of

delivery

between

April

and

December

A

total

of

pregnancies

were

initially

enrolled

with

children

born

This

represented

of

the

eligible

population

see

for

further

details

-LSB-

-RSB-

Of

these

births

were

alive

at

months

The

population

from

ALSPAC

used

for

this

study

consisted

of

children

those

who

had

DXA

scans

performed

at

aged

years

had

measures

of

humeral

dimensions

performed

and

had

data

on

pubertal

stage

available

Ethical

approval

was

obtained

from

the

ALSPAC

Law

Ethics

Committee

and

Local

Research

Ethics

Committees

Measure

of

size

at

birth

In

the

immediate

post-partum

stage

whilst

mother

and

child

were

still

in

hospital

trained

ALSPAC

staff

measured

crown-heel

length

with

the

Harpenden

Neonatometer

-LRB-

Holtain

Ltd.

Crosswell

UK

-RRB-

Alternatively

this

measure

was

collected

from

clinical

records

for

babies

who

were

not

captured

by

the

ALSPAC

staff

Measures

of

size

at

age

years

Children

were

seen

in

a

research

clinic

at

age

years

-LRB-

years

-RRB-

Parental

consent

and

child

's

assent

were

obtained

for

all

measurements

made

Height

was

measured

to

the

last

complete

millimeter

-LRB-

mm

-RRB-

using

the

Harpenden

Stadiometer

Weight

was

measured

to

the

nearest

grams

-LRB-

g

-RRB-

using

the

Tanita

Body

Fat

Analyzer

-LRB-

model

TBF

HealthCheck

Systems

New

York

USA

-RRB-

Total

body

less

head

-LRB-

TBLH

-RRB-

bone

area

-LRB-

-RRB-

TBLH

bone

mineral

content

-LRB-

g

-RRB-

TBLH

bone

mineral

density

-LRB-

-RRB-

total

body

-LRB-

TB

-RRB-

fat

mass

-LRB-

kg

-RRB-

and

TB

lean

mass

-LRB-

kg

-RRB-

were

measured

using

a

Lunar

Prodigy

dual-energy

X-ray

absorptiometer

-LRB-

Lunar

Corp.

Madison

WI

USA

-RRB-

on

children

using

the

default

mode

for

all

scans

The

child

was

positioned

carefully

on

the

scanner

and

asked

to

lay

their

hands

flat

on

the

bed

palms

down

Measures

of

humeral

dimensions

The

present

investigation

was

based

on

a

subgroup

of

children

reporting

fractures

for

whom

DXA

scans

were

available

at

age

years

and

an

additional

randomly

selected

group

of

children

giving

a

total

of

children

These

children

had

originally

been

chosen

for

a

study

investigating

the

relationships

between

bone

mass

and

fractures

-LSB-

-RSB-

The

measurer

-LRB-

EC

-RRB-

was

blinded

to

the

fracture

status

of

the

children

Customised

settings

were

available

on

the

Lunar

Prodigy

software

and

these

were

applied

to

the

total

body

DXA

image

on

screen

-LRB-

No

measures

were

performed

during

the

DXA

scan

-RRB-

A

region

of

interest

-LRB-

ROI

-RRB-

was

drawn

around

the

right

humerus

where

possible

-LRB-

in

case

of

movement

artifact

the

left

humerus

was

used

-RRB-

after

enlargement

of

the

image

to

maximum

magnification

The

bone

edge

was

detected

visually

with

ease

for

the

shaft

and

head

of

the

humerus

At

the

distal

end

a

straight

line

was

drawn

across

the

joint

space

from

medial

to

lateral

epicondyle

with

the

head

of

the

ulna

included

within

the

humeral

ROI

Where

arm

positioning

was

not

ideal

-LRB-

such

as

palms

not

flat

on

the

bed

-RRB-

the

ROI

was

fitted

as

accurately

as

possible

The

area

-LRB-

-RRB-

of

the

humeral

ROI

was

recorded

-LRB-

Fig.

-RRB-

Length

of

the

humerus

was

obtained

by

use

of

an

electronic

ruler

positioned

between

its

upper

and

lower

extremities

Average

humeral

width

-LRB-

cm

-RRB-

was

calculated

as

area

divided

by

length

The

humeral

aspect

ratio

-LRB-

AR

-RRB-

was

calculated

as

humerus

width

divided

by

length

and

then

multiplied

by

so

the

AR

is

the

humerus

width

expressed

as

a

percentage

of

humerus

length

Fig.

body

DXA

scan

showing

position

of

the

region

of

interest

-LRB-

ROI

-RRB-

around

the

right

humerus

a

Total

body

scan

image

b

Image

following

maximal

-LRB-

i.e.

fourfold

-RRB-

magnification

which

was

selected

prior

to

placement

of

the

ROI

and

measurement

of

length

by

electronic

ruler

The

precision

of

measurements

of

humeral

geometry

was

calculated

as

the

coefficient

of

variation

-LRB-

CV

-RRB-

based

on

ten

scans

with

the

measures

repeated

five

times

The

CV

was

-LSB-

confidence

interval

-LRB-

CI

-RRB-

-RSB-

for

width

-LRB-

CI

-RRB-

for

length

and

-LRB-

CI

-RRB-

for

humeral

AR

Other

measures

The

mother

's

partner

's

and

grandparent

's

race

and

ethnic

group

and

mothers

highest

educational

qualification

were

recorded

at

weeks

gestation

as

described

elsewhere

-LSB-

-RSB-

Gender

was

obtained

from

birth

notifications

At

the

time

of

the

DXA

scan

and

measurement

of

the

anthropometric

variables

the

child

's

age

was

calculated

from

the

date

of

birth

and

date

of

attendance

at

the

research

clinic

Puberty

was

assessed

by

self-completion

questionnaires

using

diagrams

based

on

Tanner

staging

of

pubic

hair

distribution

for

boys

and

girls

which

we

have

previously

found

to

show

expected

relationships

with

DXA

measures

in

this

cohort

-LSB-

-RSB-

Prepuberty

was

defined

as

Tanner

stage

and

early

puberty

as

Tanner

stage

Statistical

analyses

Results

from

children

reporting

previous

fractures

and

the

randomly

selected

subgroup

were

pooled

Statistical

analyses

were

performed

with

STATA

A

two-tailed

unpaired

t-test

was

used

to

test

the

hypothesis

of

no

difference

in

the

means

for

boys

and

girls

Linear

regression

was

used

to

assess

the

associations

between

gender

and

humerus

dimensions

which

were

adjusted

for

age

on

the

day

of

the

DXA

scan

and

pubertal

status

Additional

analyses

were

performed

following

adjustment

for

TB

fat

mass

and

for

fracture

status

Results

No

differences

in

gender

ethnicity

socio-economic

status

body

composition

or

humerus

dimensions

were

found

between

the

children

with

and

without

fractures

-LRB-

results

not

shown

-RRB-

so

these

results

were

pooled

for

all

further

analyses

Length

at

birth

age

at

DXA

measurement

height

weight

TB

fat

and

lean

mass

and

TBLH

bone

area

of

the

children

in

whom

humeral

dimensions

were

measured

are

shown

in

Table

according

to

gender

and

pubertal

stage

There

was

no

difference

in

age

height

or

weight

between

prepubertal

boys

and

girls

However

boys

had

been

longer

at

birth

-LRB-

by

cm

on

average

-RRB-

even

after

adjustment

for

gestational

age

and

birth

weight

-LRB-

P

-RRB-

Prepubertal

girls

had

a

greater

TB

fat

mass

-LRB-

P

-RRB-

whereas

prepubertal

boys

had

a

greater

TB

lean

mass

-LRB-

P

-RRB-

Puberty-related

differences

in

size

measures

were

also

seen

For

example

girls

in

early

puberty

-LRB-

Tanner

stage

-RRB-

were

on

average

cm

taller

and

kg

heavier

than

prepubertal

girls

-LRB-

Tanner

stage

-RRB-

Boys

pubertal

stage

showed

similar

trends

to

those

observed

in

girls

but

differences

in

size

measures

were

considerably

smaller

Table

age

height

weight

and

DXA-derived

total

body

fat

mass

and

lean

mass

and

total

body

less

head

bone

area

for

boys

and

girls

with

measurements

of

humeral

size

and

dimensionsa

BoysGirls

Prepubertal

N

pubertal

N

value

for

difference

between

boys

in

pre

and

early

pubertyPrepubertal

N

puberty

N

value

for

difference

between

girls

in

pre

and

early

pubertyP

value

for

difference

between

prepubertal

boys

and

girlsP

value

for

difference

between

boys

and

girls

in

early

pubertyMeanSDMeanSDMeanSDMeanSDBirth

length

-LRB-

cm

-RRB-

Age

at

DXA

-LRB-

years

-RRB-

9.80.39.90.30.6159.80.39.80.30.9460.6310.602

Height

-LRB-

cm

-RRB-

Weight

-LRB-

kg

-RRB-

TB

fat

mass

-LRB-

kg

-RRB-

TB

lean

mass

-LRB-

kg

-RRB-

TBLH

bone

area

-LRB-

-RRB-

aResults

are

shown

separately

for

boys

and

girls

who

are

further

subdivided

according

to

results

of

Tanner

stage

self-completion

questionnaire

P

values

shown

are

for

the

difference

between

prepubertal

boys

-LRB-

Tanner

stage

-RRB-

and

boys

in

early

puberty

-LRB-

Tanner

stage

-RRB-

for

the

difference

between

prepubertal

girls

-LRB-

Tanner

stage

-RRB-

and

girls

in

early

puberty

-LRB-

Tanner

stage

-RRB-

for

the

difference

between

prepubertal

boys

and

girls

and

for

the

difference

between

boys

and

girls

in

early

puberty

all

calculated

by

an

unpaired

Student

's

t-test

For

TB

fat

mass

TB

lean

mass

and

TBLH

bone

area

results

are

adjusted

for

age

at

DXA

measurement

by

linear

regression.bBirth

length

adjusted

for

gestational

age

and

birth

weight

by

linear

regression

We

then

examined

relationships

between

dimensions

of

the

humerus

age

height

and

puberty

As

expected

height

was

positively

related

to

humerus

width

and

length

based

on

analyses

in

boys

and

girls

combined

-LRB-

P

-RRB-

In

spite

of

the

relatively

narrow

age

range

of

our

study

population

a

positive

association

was

also

observed

between

age

and

width

and

length

of

the

humerus

-LRB-

P

-RRB-

In

contrast

age

and

height

were

not

related

to

humeral

AR

Similar

results

were

seen

when

boys

and

girls

were

analysed

separately

Girls

in

early

puberty

had

greater

humeral

width

length

and

area

compared

to

prepubertal

girls

but

humeral

AR

in

these

two

groups

was

similar

-LRB-

Table

-RRB-

In

contrast

no

differences

were

observed

in

any

measure

of

humeral

geometry

between

pre

and

early

pubertal

boys

Table

dimensions

in

prepubertal

boys

boys

in

early

puberty

prepubertal

girls

and

girls

in

early

pubertya

BoysGirls

Prepubertal

N

pubertal

N

value

for

difference

between

boys

in

pre

and

early

pubertyPrepubertal

N

puberty

N

value

for

difference

between

girls

in

pre

and

early

pubertyP

value

for

difference

between

prepubertal

boys

and

girlsP

value

for

difference

between

boys

and

girls

in

early

pubertyMeanSDMeanSDMeanSDMeanSDLength

-LRB-

cm

-RRB-

Width

-LRB-

cm

-RRB-

AR

-LRB-

-RRB-

Area

-LRB-

-RRB-

aResults

show

mean

and

standard

deviation

for

humeral

length

width

aspect

ratio

-LRB-

AR

-RRB-

and

area

P

values

shown

are

for

the

difference

between

prepubertal

boys

-LRB-

Tanner

stage

-RRB-

and

boys

in

early

puberty

-LRB-

Tanner

stage

-RRB-

for

the

difference

between

prepubertal

girls

-LRB-

Tanner

stage

-RRB-

and

girls

in

early

puberty

-LRB-

Tanner

stage

-RRB-

for

the

difference

between

prepubertal

boys

and

girls

and

for

the

difference

between

boys

and

girls

in

early

puberty

all

calculated

by

an

unpaired

Student

's

t-test

All

analyses

are

adjusted

for

age

at

DXA

measurement

by

linear

regression

We

then

investigated

the

effects

of

gender

on

measures

of

humeral

geometry

according

to

pubertal

stage

following

adjustment

for

age

of

DXA

scan

The

humerus

of

prepubertal

boys

was

slightly

shorter

-LRB-

on

average

cm

-RRB-

but

of

greater

width

-LRB-

average

of

cm

-RRB-

and

area

-LRB-

on

average

-RRB-

compared

to

prepubertal

girls

as

a

result

of

which

humeral

AR

was

greater

in

prepubertal

boys

-LRB-

an

average

of

greater

P

-RRB-

-LRB-

Table

and

Fig.

-RRB-

Boys

in

early

puberty

still

had

a

shorter

humeral

length

but

a

similar

humeral

width

and

a

smaller

area

than

girls

in

early

puberty

as

a

result

of

which

humeral

AR

remained

greater

in

early

pubertal

boys

-LRB-

an

average

of

greater

see

Fig.

-RRB-

Similar

gender

differences

were

seen

after

adjustment

for

TB

fat

mass

and

fracture

status

-LRB-

results

not

shown

-RRB-

Fig.

between

humeral

geometry

gender

and

puberty

as

determined

in

boys

and

girls

Figure

shows

mean

SD

a

humerus

width

-LRB-

cm

-RRB-

b

humerus

length

-LRB-

cm

-RRB-

and

c

humerus

aspect

ratio

-LRB-

AR

-RRB-

according

to

gender

and

Tanner

stage

of

puberty

P

values

are

for

the

difference

between

boys

and

girls

All

analyses

are

adjusted

for

age

Discussion

Humeral

width

and

length

were

positively

related

to

age

and

height

in

boys

and

girls

combined

and

to

pubertal

status

in

girls

in

this

contemporary

cohort

of

pre

and

early

pubertal

children

These

observations

are

similar

to

those

previously

reported

for

other

DXA-derived

measures

of

bone

size

in

this

cohort

such

as

TBLH

and

spinal

bone

area

-LSB-

-RSB-

In

contrast

age

height

and

pubertal

status

did

not

influence

the

ratio

between

humeral

width

and

length

as

reflected

by

humeral

AR

presumably

reflecting

the

action

of

mechanisms

to

ensure

that

skeletal

shape

remains

constant

as

bones

grow

In

both

pre

and

early

pubertal

boys

humeral

length

was

found

to

be

shorter

compared

with

girls

whereas

humeral

width

was

similar

or

greater

resulting

in

a

greater

humeral

AR

in

boys

Taken

together

these

findings

suggest

that

gender

but

not

puberty

affects

the

balance

between

periosteal

and

longitudinal

growth

Hence

differences

in

overall

skeletal

shape

between

boys

and

girls

appear

to

be

established

prior

to

puberty

However

from

the

present

study

we

are

unable

to

determine

whether

the

AR

changes

during

later

pubertal

stages

or

during

subsequent

ageing

Our

observation

that

Tanner

stage

was

found

to

affect

humeral

geometry

in

girls

but

not

boys

presumably

reflects

the

fact

that

boys

and

girls

in

Tanner

stage

are

not

equivalent

in

terms

of

skeletal

development

The

finding

that

height

and

weight

differences

between

Tanner

stages

and

were

considerably

greater

in

girls

compared

to

boys

is

consistent

with

this

view

Therefore

analyses

of

differences

in

humeral

geometry

between

Tanner

stage

boys

and

girls

may

have

limited

validity

since

these

may

not

have

fully

accounted

for

gender

differences

in

skeletal

maturity

that

are

likely

to

have

been

present

Nevertheless

since

humeral

AR

was

unaffected

by

Tanner

stage

in

the

age

of

children

studied

these

reservations

are

unlikely

to

affect

the

main

conclusion

from

this

study

namely

that

humeral

AR

is

greater

in

boys

compared

to

girls

as

assessed

at

age

years

The

gender

differences

in

skeletal

shape

shown

in

Table

-LRB-

approximately

-RRB-

were

smaller

than

those

observed

in

fat

mass

lean

mass

and

bone

area

as

in

Table

-LRB-

ranging

from

to

-RRB-

The

larger

gender

differences

in

TBLH

bone

area

-LRB-

-RRB-

compared

with

humeral

area

-LRB-

-RRB-

suggest

that

greater

gender

differences

in

bone

area

are

present

at

other

skeletal

sites

Consistent

with

this

conclusion

vertebral

body

size

has

been

reported

to

be

-LSB-

-RSB-

and

-LSB-

-RSB-

larger

in

boys

compared

to

girls

Our

observation

of

an

gender

difference

in

lean

mass

and

difference

in

fat

mass

compared

to

the

gender

difference

in

humeral

length

and

difference

in

width

perhaps

reflects

the

strength

of

association

between

fat

or

lean

mass

and

bone

area

-LSB-

-RSB-

Our

conclusion

that

gender

differences

in

humeral

shape

are

established

prior

to

puberty

is

supported

by

a

previous

study

in

which

greater

humeral

width

was

seen

in

prepubertal

boys

compared

to

girls

based

on

radiogrammetry

-LSB-

-RSB-

In

the

present

study

the

humerus

was

selected

as

the

most

suitable

site

for

providing

an

accurate

measure

of

aspect

ratio

by

analysis

of

total

body

DXA

scans

Although

other

skeletal

sites

were

not

evaluated

we

assume

that

equivalent

gender

differences

in

periosteal

relative

to

longitudinal

growth

are

established

prior

to

puberty

throughout

the

appendicular

skeleton

Consistent

with

this

suggestion

the

metacarpals

and

proximal

radius

have

been

found

to

be

wider

in

boys

compared

to

girls

at

all

stages

of

development

as

assessed

by

analysis

of

radiographs

-LSB-

-RSB-

Furthermore

in

a

recent

study

of

boys

and

girls

boys

had

higher

rates

of

periosteal

expansion

relative

to

girls

as

measured

prospectively

over

months

at

the

radial

midshaft

by

pQCT

and

this

gender

difference

was

similar

in

early

peri

and

postpubertal

children

-LSB-

-RSB-

In

a

recent

analysis

of

males

and

age

height

and

weight-matched

females

long

bone

width

was

found

to

be

greater

at

the

hip

and

distal

tibia

as

measured

by

DXA

and

pQCT

respectively

in

boys

compared

to

girls

-LSB-

-RSB-

Although

our

results

suggest

that

gender

differences

in

long

bone

width

are

due

to

more

rapid

periosteal

apposition

relative

to

longitudinal

growth

in

boys

prior

to

puberty

the

precise

timing

of

this

gender

effect

is

currently

unclear

Review

of

the

literature

shows

no

evidence

of

gender

differences

in

forearm

bone

width

at

birth

-LSB-

-RSB-

but

studies

of

preschool

and

older

children

show

conflicting

results

Specker

et

al.

-LSB-

-RSB-

report

no

gender

differences

in

radius

width

in

children

aged

years

-LRB-

based

on

children

-RRB-

whereas

Tanner

et

al.

-LSB-

-RSB-

found

that

the

humerus

is

wider

in

boys

compared

to

girls

from

age

years

until

the

time

of

pubertal

growth

acceleration

in

girls

-LRB-

based

on

children

aged

years

-RRB-

It

is

also

possible

that

the

method

used

to

measure

bone

size

influences

whether

gender

differences

are

found

For

example

studies

described

above

that

used

radiographs

or

pQCT

identified

gender

differences

-LSB-

-RSB-

whereas

those

that

used

single

photon

absorptiometry

did

not

-LSB-

-RSB-

Prepubertal

gender

differences

in

the

relative

rates

of

longitudinal

and

periosteal

growth

that

we

observed

may

be

mediated

by

alterations

in

endocrine

factors

For

example

prepubertal

girls

have

higher

levels

of

insulin-like

growth

factor

I

estradiol

and

testosterone

concentrations

compared

to

prepubertal

boys

-LSB-

-RSB-

all

of

which

are

known

to

have

effects

on

both

longitudinal

and

periosteal

bone

growth

In

terms

of

the

potential

influence

of

these

differences

on

fracture

risk

according

to

beam

theory

columns

with

larger

aspect

ratios

-LRB-

i.e.

ratio

of

width

to

length

-RRB-

have

a

reduced

fracture

risk

than

columns

with

smaller

aspect

ratios

-LSB-

-RSB-

In

addition

the

ratio

between

periosteal

diameter

to

long

bone

length

provides

an

approximate

estimate

of

critical

buckling

load

such

that

a

lower

aspect

ratio

results

in

a

long

bone

which

is

more

prone

to

failure

by

buckling

-LSB-

-RSB-

Furthermore

in

children

the

majority

of

fractures

occur

at

the

distal

forearm

and

can

be

divided

into

two

main

types

simple

torus

fractures

and

the

greenstick

variety

both

of

which

are

associated

with

buckling

or

bulging

on

the

side

of

the

bone

in

compression

-LSB-

-RSB-

Therefore

theoretically

measurement

of

the

ratio

between

long

bone

width

and

length

from

total

body

DXA

scans

as

described

here

may

provide

an

in

vivo

method

for

evaluating

biomechanical

strength

of

the

skeleton

However

against

this

suggestion

boys

have

a

higher

fracture

risk

than

girls

in

childhood

-LSB-

-RSB-

whereas

girls

have

a

smaller

humeral

AR

Furthermore

we

found

no

relationship

between

humeral

AR

as

measured

in

the

present

study

and

fracture

risk

-LSB-

-RSB-

One

possible

explanation

for

this

lack

of

association

is

that

our

assumption

that

the

humerus

is

cylindrical

ignores

gender

differences

in

shape

at

the

epiphysis

or

metaphysis

which

might

contribute

to

fracture

risk

On

the

other

hand

humeral

AR

may

predict

fracture

risk

in

certain

adult

populations

in

view

of

evidence

that

bone

width

has

previously

been

reported

to

be

related

to

stress

fractures

in

soldiers

-LSB-

-RSB-

In

light

of

our

results

which

suggest

that

humeral

AR

can

be

evaluated

with

relatively

good

precision

further

studies

are

justified

to

determine

whether

this

parameter

represents

a

novel

bone

mineral

density

-LRB-

BMD

-RRB-

independent

risk

factor

for

upper

limb

fracture

The

measure

of

humeral

length

from

which

we

derived

humeral

AR

is

likely

to

be

relatively

accurate

since

the

upper

and

lower

ends

of

the

humerus

are

generally

clearly

visible

on

total

body

DXA

scans

-LRB-

see

Fig.

-RRB-

Alternative

measurement

techniques

such

as

pQCT

offer

advantages

over

the

approach

described

here

by

measuring

bone

diameter

directly

but

do

not

provide

a

measure

of

bone

length

Another

limitation

of

the

present

study

is

that

unlike

girls

age

years

appeared

to

be

too

young

to

evaluate

possible

effects

of

early

puberty

on

skeletal

development

in

boys

In

future

studies

we

plan

to

repeat

these

analyses

in

older

boys

to

confirm

that

as

in

girls

puberty

increases

humeral

width

and

length

whilst

having

no

effect

on

humeral

AR

In

conclusion

we

have

found

that

long

bone

shape

as

reflected

by

humeral

AR

which

we

derived

using

a

novel

technique

from

total

body

DXA

scans

is

unaffected

by

age

height

and

puberty

as

evaluated

in

a

child

cohort

of

relatively

narrow

age

range

and

range

of

Tanner

stages

This

finding

suggests

that

the

ratio

between

longitudinal

and

periosteal

growth

is

controlled

to

ensure

it

remains

constant

during

rapid

growth

However

humeral

AR

was

related

to

gender

suggesting

that

the

greater

periosteal

diameter

of

boys

compared

to

girls

which

is

well

recognised

is

a

consequence

of

gender

differences

in

the

balance

between

longitudinal

and

periosteal

bone

growth

Interestingly

these

gender

differences

in

humeral

AR

were

present

in

prepubertal

children

possibly

resulting

from

prepubertal

differences

in

sex

hormone

levels

Further

studies

are

justified

to

determine

whether

humeral

AR

is

an

important

determinant

of

biomechanical

strength

and

fracture

risk

particularly

in

adult

populations

B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B I O O O O O O O O O O O O O B I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O

epidemiology
growth and development
long bone dimensions
population studies


Superior cerebellar artery aneurysms : incidence , clinical presentation and midterm outcome of endovascular treatment Introduction The aim of this retrospective study was to determine the incidence , clinical presentation and midterm clinical and imaging outcome of endovascular treatment of 34 superior cerebellar artery -LRB- SCA -RRB- aneurysms in 33 patients . Introduction Aneurysms located on the superior cerebellar artery -LRB- SCA -RRB- are uncommon and their presentation , natural history and clinical management are poorly understood -LSB- 1 , 2 -RSB- . Reports about the endovascular or surgical management of SCA aneurysms are rare and are usually incorporated in clinical series of basilar artery or posterior circulation aneurysms -LSB- 3 -- 18 -RSB- . The aim of this retrospective study was to determine the incidence , clinical presentation and midterm clinical and imaging results of endovascular treatment of 35 patients with 36 SCA aneurysms . Methods Patients Between January 1995 and January 2007 , 2,112 aneurysms were treated in our institution . Of the 2,112 treated aneurysms , 324 -LRB- 15 % -RRB- were located in the posterior circulation and 1,788 -LRB- 85 % -RRB- in the anterior circulation . Surgery was performed in 970 aneurysms and endovascular treatment in 1,142 aneurysms . Of the 2,112 treated aneurysms , 36 aneurysms in 35 patients were located on the SCA , resulting in an incidence of 1.7 % of all treated intracranial aneurysms and 11.1 % of treated posterior circulation aneurysms . We excluded one patient with a peripheral SCA flow aneurysm associated with an arteriovenous malformation and one peripheral partially thrombosed SCA aneurysm presenting with trochlear nerve palsy . In one patient with four aneurysms , one aneurysm was located on the proximal right SCA and one aneurysm on the distal left SCA . All 33 proximal SCA aneurysms were primarily based on the basilar artery at the branching point of the SCA with or without incorporation of the SCA origin in the base . All 34 SCA aneurysms in 33 patients were treated by endovascular techniques . There were 6 men and 27 women with a mean age of 50.7 years -LRB- median 49 years , range 29 -- 72 years -RRB- . Of 34 aneurysms , 22 -LRB- 65 % -RRB- had ruptured , 7 -LRB- 20 % -RRB- were additional to another ruptured aneurysm , 4 -LRB- 12 % -RRB- presented with symptoms of a mass effect -LRB- trigeminal neuralgia 2 , oculomotor palsy 2 -RRB- and one -LRB- 3 % -RRB- was an incidental finding -LRB- Fig. 1 -RRB- . The mean size of the 34 SCA aneurysms was 7.3 mm -LRB- median 6 mm , range 2 -- 27 mm -RRB- . Fig. 1Incidentally found SCA aneurysm in a 39-year-old man with vertebrobasilar embolic infarcts . a T1-weighted MR image shows a hyperintense lesion adjacent to the brainstem . b 3-D vertebral angiogram reveals a small SCA aneurysm The clinical condition of the 22 patients with a ruptured SCA aneurysm at the time of treatment was HH I -- II in 16 , HH III in 3 and HH IV -- V in 3 . Seven SCA aneurysms in six patients were additional to another ruptured aneurysm and were coiled in the same session as the ruptured aneurysm . The clinical condition of these six patients was HH I -- II in five and HH IV -- V in one . Of the 33 patients , 14 -LRB- 42 % -RRB- had multiple aneurysms -LRB- Fig. 2 -RRB- for a total of 72 aneurysms : 5 patients had 2 aneurysms , 3 patients had 3 aneurysms , 3 patients had 4 aneurysms , 1 patient had 5 aneurysms , 1 patient had 7 aneurysms and 1 patient had 8 aneurysms . Of the 72 aneurysms in 35 patients , 53 were coiled , 13 were clipped , and 6 were small -LRB- < 2 mm -RRB- and left untreated . Fig. 2Pre - and posttreatment images of two patients with multiple posterior circulation aneurysms . a A 44-year-old man with a ruptured middle cerebral artery aneurysm and four additional aneurysms . 3-D vertebral angiogram reveals right SCA aneurysm -LRB- short single arrow -RRB- , left distal SCA aneurysm -LRB- long single arrow -RRB- and basilar tip aneurysm -LRB- pair of arrows -RRB- . b Complete occlusion after coiling . c A 61-year-old woman with a ruptured middle cerebral artery aneurysm and additional aneurysms on the left SCA and basilar tip . d Adequate occlusion of basilar tip and SCA aneurysms Coiling procedure Coiling of aneurysms was performed on a biplane angiographic unit -LRB- Integris BN 3000 Neuro , Philips Medical Systems , Best , The Netherlands -RRB- with the patient under general anaesthesia and systemic heparinization . Heparin was continued intravenously or subcutaneously for 48 h after the procedure , followed by low-dose aspirin for 3 months orally . Coiling was performed with Guglielmi detachable coils -LRB- GDC , Boston Scientific , Fremont , Calif. -RRB- or TruFill DCS coils -LRB- Cordis , Miami , Fl. -RRB- . The aim of coiling was to pack the aneurysm as densely as possible , until not a single additional coil could be placed . Four wide-necked aneurysms -LRB- 12 % -RRB- were coiled with the aid of a supporting balloon in the basilar artery . One aneurysm was located distal on the SCA and was selectively occluded with coils sparing the parent SCA . Complications of coiling were recorded . Initial angiographic results of coiling were classified as complete occlusion -LRB- 100 % -RRB- , near complete occlusion -LRB- 90 -- 100 % -RRB- and incomplete occlusion -LRB- < 90 % -RRB- . Clinical and angiographic follow-up Patients who survived the hospital admission period were scheduled for a follow-up visit in the outpatient clinic 6 weeks after treatment and for follow-up angiography after 6 and 18 months . Neurological status according to the Glasgow Outcome Scale -LRB- GOS -RRB- was evaluated at every outpatient clinic visit and at every admission for follow-up angiography . The results of follow-up angiography were classified in the same way as for initial angiographic results . Results Initial angiographic results and complications Initial angiographic occlusion was complete or near complete -LRB- 90 -- 100 % occlusion -RRB- in 32 aneurysms and incomplete in 2 aneurysms -LRB- both 80 % occlusion -RRB- . Complications leading to permanent morbidity or death occurred in two patients . The first patient was a 42-year-old woman who presented with a ruptured 2-mm wide-necked SCA aneurysm in HH I . During insertion of a coil with the aid of a supporting balloon , a rupture occurred and the patient died 12 h later -LRB- mortality 1 of 33 , 3.0 % , 95 % CI 0.01 -- 16.65 % -RRB- . The second patient was a 71-year-old woman admitted with a ruptured 10-mm wide-necked SCA aneurysm -LRB- Fig. 3 -RRB- . The SCA itself originated from the sac . The aneurysm was coiled with the aid of a supporting balloon with adequate occlusion and preserved flow in the SCA . However , the patient did not awake from general anaesthesia . Immediate control angiography revealed that the SCA had become occluded . MRI several days later showed infarctions in the vascular territory of the SCA in the brainstem and cerebellum . The patient gradually recovered but remained dependent . At the time of this report almost 4 years later she was still in a nursing home -LRB- procedural morbidity 1 of 33 , 3.0 % , 95 % CI 0.01 -- 16.65 % -RRB- . Fig. 3Ischemic complication of coiling in a 71-year-old woman with a ruptured SCA aneurysm . a Vertebral angiogram demonstrates a wide-necked right SCA aneurysm with the SCA arising from the sac . b , c Balloon-assisted coiling with adequate occlusion and preserved flow in the SCA . The patient did not awake from general anaesthesia . Immediate control angiography revealed that the SCA had become occluded -LRB- not shown -RRB- . d MRI several days later showing brainstem and cerebellum infarctions in the SCA territory Clinical follow-up Clinical follow-up was available for all 33 patients . One patient died of a procedural rupture and another patient died of diffuse vasospasm after subarachnoid haemorrhage -LRB- SAH -RRB- . The remaining 31 patients had clinical follow-up of mean 45 months -LRB- median 44.5 months , range 4 -- 103 months , 118 patient-years -RRB- . Outcome at 6 months follow up of these 31 patients was GOS 5 in 26 -LRB- 84 % -RRB- , GOS 4 in 4 -LRB- 13 % -RRB- and GOS 3 in 1 patient -LRB- 3 % -RRB- . Symptoms of mass effect on cranial nerves in four patients were cured in all . During extended follow up , two patients died of unrelated disease 3 and 6 years after coiling of a SCA aneurysm : pulmonary embolism in one patient and disseminated bronchial carcinoma in the other patient . There were no episodes of -LRB- re -RRB- bleeding during the 118 patient-years of follow-up . Angiographic follow-up Of the 31 surviving patients , 4 refused follow-up angiography . The remaining 27 patients -LRB- with 28 SCA aneurysms -RRB- all had 6 months follow-up angiography and 19 had extended angiographic follow-up of a mean of 31 months -LRB- median 22 months , range 18 -- 84 months -RRB- . Stable complete or near-complete occlusion was apparent in 25 of 28 aneurysms . In one patient , a 66-year-old man with a 27-mm partially thrombosed SCA aneurysm presenting with trigeminal neuralgia , the coils had migrated into the intraluminal thrombus at the 6-month follow-up angiography . However , the trigeminal neuralgia was cured and the aneurysm was not retreated . The patient died 6 years later of disseminated bronchial carcinoma . Two aneurysms in two patients that were initially incompletely occluded -LRB- both 80 % occlusion -RRB- remained so at extended angiographic follow-up . Additional treatment was judged impossible in both patients . Discussion In this study , we found that SCA aneurysms are rare with an incidence of 1.7 % of all treated intracranial aneurysms and 11.1 % of treated posterior circulation aneurysms at our institution . The majority of patients presented with SAH and 42 % of patients also had aneurysms at other locations . This frequent association with multiple aneurysms has not been established before . Endovascular occlusion with detachable coils is feasible with good angiographic and clinical results and with low morbidity -LSB- 3 -RSB- . The proximal SCA has an intimate relation with cranial nerves III , IV and V -LSB- 19 -RSB- . Aneurysms on the SCA may therefore present with palsies of these nerves , as was the case in four of our patients -LSB- 10 , 11 -RSB- . After coiling , symptoms of nerve compression regressed in all four patients . One of 34 SCA aneurysms was located distally on the artery . It was possible to occlude this aneurysm with sparing of the parent SCA . When selective occlusion of such an aneurysm is not possible , simultaneous occlusion of the aneurysm together with the parent artery can be performed . Collateral blood flow may limit ischemic infarctions and outcome is usually good -LSB- 4 , 12 -- 15 -RSB- . Although surgical treatment of SCA aneurysms in experienced hands is associated with good results , access may be challenging needing destructive approaches -LSB- 20 -- 22 -RSB- . The presence of important perforating arteries and adjacent cranial nerves makes clipping of SCA aneurysms difficult and complications may occur . Because SCA aneurysms are rare , not many surgeons will gain experience in the treatment of these aneurysms . In addition , many patients are in bad clinical condition and are not good surgical candidates in the acute phase . While surgery for SCA aneurysms is often difficult , limited to good-grade patients and associated with substantial morbidity , coiling is technically easy and can also be performed in the acute phase of haemorrhage in bad-grade patients . This makes coiling the method of choice to treat SCA aneurysms . Conclusion SCA aneurysms are rare with an incidence of 1.7 % of treated aneurysms at our institution . There is a frequent association with aneurysms at other locations . Most patients present with SAH . Since the SCA is closely related to cranial nerves III , IV and V , some aneurysms present with palsies of these nerves . Endovascular occlusion with detachable coils is feasible with good angiographic and clinical results .

B I I O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O B O O O O O B I I O O O O O O O O O O O O O B I I O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O B O O O O O O O O O O O O O O B O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O B O O O O O O O O O B O O O O O O O O B O O O O O O O O O O B O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O B O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O B O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O B O O O O O O O O O B O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O B O O O O O O O O B O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O

superior cerebellar artery
aneurysm
coiling
outcome