Foramen

magnum

meningiomas

detailed

surgical

approaches

and

technical

aspects

at

Lariboisière

Hospital

and

review

of

the

literature

Foramen

magnum

meningiomas

are

challenging

tumors

requiring

special

considerations

because

of

the

vicinity

of

the

medulla

oblongata

the

lower

cranial

nerves

and

the

vertebral

artery

After

detailing

the

relevant

anatomy

of

the

foramen

magnum

area

we

will

explain

our

classification

system

based

on

the

compartment

of

development

the

dural

insertion

and

the

relation

to

the

vertebral

artery

The

compartment

of

development

is

most

of

the

time

intradural

and

less

frequently

extradural

or

both

intraextradural

Intradurally

foramen

magnum

meningiomas

are

classified

posterior

lateral

and

anterior

if

their

insertion

is

respectively

posterior

to

the

dentate

ligament

anterior

to

the

dentate

ligament

and

anterior

to

the

dentate

ligament

with

extension

over

the

midline

This

classification

system

helps

to

define

the

best

surgical

approach

and

the

lateral

extent

of

drilling

needed

and

anticipate

the

relation

with

the

lower

cranial

nerves

In

our

department

three

basic

surgical

approaches

were

used

the

posterior

midline

the

postero-lateral

and

the

antero-lateral

approaches

We

will

explain

in

detail

our

surgical

technique

Finally

a

review

of

the

literature

is

provided

to

allow

comparison

with

the

treatment

options

advocated

by

other

skull

base

surgeons

Introduction

Meningiomas

are

common

neoplasms

representing

to

of

all

intracranial

tumors

-LSB-

-RSB-

Among

all

the

meningiomas

only

to

arises

at

the

foramen

magnum

-LRB-

FM

-RRB-

level

-LSB-

-RSB-

Nevertheless

meningiomas

are

the

most

commonly

observed

FM

tumors

representing

of

all

benign

tumors

-LSB-

-RSB-

Most

of

the

time

these

are

strictly

intradural

Ten

percent

have

an

extradural

extension

Most

are

intra

and

extradural

and

a

few

may

be

entirely

extradural

-LSB-

-RSB-

The

lesion

is

often

large

when

discovered

because

of

their

slow-growing

rate

their

indolent

development

the

difficulty

of

the

diagnosis

leading

to

a

long

interval

since

the

first

symptom

and

the

wide

subarachnoid

space

at

this

level

-LSB-

-RSB-

The

prerequisite

for

treating

FM

meningiomas

-LRB-

FMMs

-RRB-

is

the

perfect

knowledge

of

the

surgical

anatomy

We

will

then

first

detail

a

comprehensive

review

of

the

relevant

anatomy

of

the

FM

area

with

special

emphasis

on

the

vertebral

artery

-LRB-

VA

-RRB-

and

segments

Second

we

will

describe

our

classification

system

This

classification

system

helps

for

determining

the

best

surgical

approach

and

for

anticipating

the

position

of

lower

cranial

nerves

The

technical

aspects

of

our

surgical

approaches

will

then

be

detailed

extensively

Finally

we

provide

a

summary

of

the

relevant

literature

detailing

surgical

results

and

surgical

approaches

advocated

by

other

skull

base

surgeons

and

discussing

the

extent

of

bone

resection

and

the

need

for

fusion

Surgical

anatomy

Limits

of

the

FM

A

meningioma

is

considered

to

be

located

into

the

FM

region

if

its

insertion

zone

is

mainly

situated

into

the

FM

area

According

to

the

FM

limits

that

we

have

previously

used

the

FM

area

is

defined

by

these

landmarks

-LSB-

-RSB-

-LRB-

Fig.

-RRB-

Anterior

border

lower

third

of

the

clivus

and

upper

edge

of

the

body

of

borders

jugular

tubercles

and

upper

aspect

of

laminasPosterior

border

anterior

edge

of

the

squamous

occipital

bone

and

spinous

processFig

of

the

foramen

magnum

anatomy

through

a

postero-lateral

approach

The

skin

incision

-LRB-

dotted

line

-RRB-

extends

on

the

midline

just

upper

to

the

occipital

protuberance

and

curves

laterally

toward

the

pathological

side

The

right

vertebral

artery

has

been

elevated

from

the

posterior

arch

The

posterior

arch

has

been

resected

on

the

pathological

side

and

a

suboccipital

craniectomy

has

been

performed

The

dura

matter

has

been

opened

CN

IX

X

XI

PICA

CN

XII

vertebral

artery

segment

dentate

ligament

vertebral

artery

segment

The

VA

and

segments

The

VA

and

segments

are

important

vascular

structures

whose

anatomy

must

be

perfectly

known

when

approaching

FMMs

In

fact

after

piercing

the

lateral

aspect

of

the

occipito-atlantal

dura

mater

the

VA

segment

becomes

the

segment

and

then

joins

the

contralateral

one

to

form

the

basilar

artery

-LSB-

-RSB-

The

VA

segment

anatomy

and

techniques

of

approach

exposure

and

transposition

have

been

extensively

described

-LSB-

-RSB-

In

summary

the

VA

segment

also

called

the

suboccipital

segment

extends

from

the

transverse

process

to

the

FM

dura

mater

Its

course

is

divided

in

three

portions

a

vertical

portion

between

the

transverse

processes

of

and

a

horizontal

portion

in

the

groove

of

the

posterior

arch

of

the

atlas

and

an

oblique

portion

on

leaving

this

groove

up

to

the

dura

mater

-LSB-

-RSB-

Along

its

course

this

VA

segment

can

be

at

the

origin

of

small

collateral

branches

in

the

middle

of

the

posterolateral

aspect

of

the

portion

corresponding

to

the

radicular

artery

a

small

muscular

branch

coursing

posteriorly

at

the

upper

exit

of

the

transverse

foramen

the

posterior

meningeal

artery

and

the

posterior

spinal

artery

just

before

its

dural

penetration

This

last

branch

enters

the

dural

foramen

where

the

nerve

root

exits

the

spinal

canal

-LSB-

-RSB-

and

can

also

be

bound

with

the

VA

by

fibrous

dural

bands

The

posterior

spinal

artery

may

also

arise

from

the

initial

intradural

part

of

the

VA

segment

or

from

the

posteroinferior

cerebellar

artery

-LRB-

PICA

-RRB-

-LSB-

-RSB-

Then

this

branch

runs

medially

behind

the

most

rostral

attachment

of

the

dentate

ligament

-LSB-

-RSB-

On

reaching

the

lower

medulla

it

divides

into

ascending

and

descending

branches

providing

respectively

the

vascular

supply

to

a

part

of

the

medulla

oblongata

and

the

spinal

cord

-LSB-

-RSB-

The

VA

segment

is

surrounded

by

a

periosteal

sheath

that

invaginates

into

the

dura

when

piercing

the

FM

lateral

dura

thus

creating

a

double

furrow

for

mm

In

fact

the

periosteal

sheath

is

in

continuity

with

the

outer

layer

of

the

dura

At

this

level

the

VA

is

attached

to

the

periosteal

sheath

and

the

adventitia

is

adherent

to

the

double

furrow

forming

a

sort

of

distal

fibrous

ring

-LSB-

-RSB-

In

such

a

way

despite

being

the

most

mobile

segment

the

VA

segment

is

fixed

at

its

extremities

Anatomical

relations

of

the

VA

are

modified

by

head

movements

of

rotation

as

well

as

during

surgical

positioning

In

neutral

position

the

vertical

and

horizontal

portions

of

the

segment

are

perpendicular

On

the

contrary

after

head

rotation

as

required

during

an

anterolateral

approach

both

segments

are

stretched

and

run

parallel

only

separated

by

the

posterior

arch

of

the

atlas

because

the

transverse

process

is

pushed

anteriorly

by

this

movement

away

from

the

transverse

process

-LSB-

-RSB-

Abnormalities

of

the

VA

segment

are

important

to

know

and

to

identify

preoperatively

In

of

the

subjects

the

VAs

size

is

different

One

side

is

dominant

and

the

other

is

hypoplastic

or

atretic

-LSB-

-RSB-

The

VA

segment

can

end

at

the

PICA

or

at

the

occipital

artery

-LSB-

-RSB-

In

of

the

cases

the

PICA

originates

extracranially

arising

from

the

VA

above

between

and

or

even

in

the

segment

-LSB-

-RSB-

The

VA

segment

can

have

an

intradural

course

that

corresponds

to

a

VA

duplication

One

atretic

portion

follows

the

normal

course

but

the

main

portion

pierces

the

dura

between

and

-LSB-

-RSB-

A

proatlantal

artery

consists

of

a

persistent

congenital

anastomosis

between

the

carotid

artery

and

the

VA

it

is

often

associated

with

an

atretic

proximal

VA

and

an

extracranial

origin

of

the

PICA

-LSB-

-RSB-

Finally

the

groove

of

the

arch

of

the

atlas

can

be

turned

into

a

tunnel

if

the

occipitoatlantal

membrane

is

calcified

or

ossified

raising

some

difficulties

to

expose

the

horizontal

portion

at

this

level

-LSB-

-RSB-

The

VA

segment

ascends

from

the

dura

up

to

the

anterior

aspect

of

the

pontomedullary

sulcus

where

it

joins

the

controlateral

one

to

form

the

basilar

artery

Initially

the

VA

segment

faces

posteriorly

and

medially

the

occipital

condyle

the

hypoglossal

canal

and

the

jugular

tubercle

Later

the

VA

segment

lies

on

the

clivus

and

runs

in

front

of

the

hypoglossal

and

the

lower

cranial

nerves

rootlets

At

the

FM

level

the

VA

segment

is

at

the

origin

of

several

branches

the

PICA

the

anterior

spinal

artery

the

anterior

and

posterior

meningeal

arteries

The

PICA

is

the

main

VA

branch

and

originates

at

above

or

below

the

FM

level

-LSB-

-RSB-

The

anterior

spinal

artery

starts

near

the

vertebrobasilar

junction

Most

of

the

time

the

anterior

spinal

arteries

of

both

sides

joins

together

above

the

FM

level

near

the

lower

end

of

the

olives

before

descending

through

the

FM

and

running

on

the

anterior

midline

-LSB-

-RSB-

In

some

cases

one

artery

is

dominant

or

no

fusion

exists

between

both

arteries

only

one

of

these

arteries

forming

the

anterior

spinal

artery

The

vascular

supply

of

the

FM

dura

originates

from

the

anterior

and

posterior

VA

meningeal

branches

and

the

meningeal

branches

of

the

ascending

pharyngeal

and

occipital

arteries

-LSB-

-RSB-

Infrequently

meningeal

branches

are

coming

from

the

PICA

the

posterior

spinal

artery

and

the

VA

segment

The

anterior

meningeal

branch

arises

from

the

VA

at

the

level

of

the

third

interspace

The

posterior

meningeal

artery

originates

from

the

VA

posterosuperior

aspect

when

turning

around

the

lateral

mass

of

the

atlas

above

the

posterior

arch

of

the

atlas

just

before

penetrating

the

dura

or

just

at

the

beginning

of

the

segment

-LSB-

-RSB-

The

ascending

pharyngeal

artery

a

branch

of

the

external

carotid

artery

gives

meningeal

branches

passing

into

the

hypoglossal

canal

and

the

jugular

foramen

The

meningeal

branch

of

the

occipital

artery

is

inconstant

and

runs

through

the

mastoid

emissary

foramen

-LSB-

-RSB-

Lower

cranial

nerves

The

glossopharyngeal

-LRB-

CN

IX

-RRB-

vagus

-LRB-

CN

X

-RRB-

and

spinal

accessory

-LRB-

CN

XI

-RRB-

nerves

arise

from

rootlets

of

the

postolivary

sulcus

and

join

the

jugular

foramen

passing

ventral

to

the

choroid

plexus

protruding

from

the

foramen

of

Luschka

and

dorsal

to

the

VA

-LSB-

-RSB-

The

accessory

nerve

is

composed

of

rootlets

originating

from

the

spinal

cord

and

the

medulla

Spinal

rootlets

join

together

to

form

the

main

trunk

which

ascends

through

the

FM

running

behind

the

dentate

ligament

and

unites

with

the

upper

medullary

rootlets

Anastomoses

with

the

dorsal

roots

of

the

upper

cervical

nerves

are

frequent

that

with

the

nerve

root

being

the

most

common

and

largest

one

-LSB-

-RSB-

The

upper

medullary

rootlets

penetrate

directly

the

jugular

foramen

-LSB-

-RSB-

The

hypoglossal

nerve

-LRB-

CN

XII

-RRB-

arises

from

rootlets

of

the

preolivary

sulcus

This

nerve

runs

anterolateral

through

the

subarachnoid

space

and

pass

behind

the

VA

to

reach

the

hypoglossal

canal

Rarely

the

VA

separates

the

CN

XII

rootlets

-LSB-

-RSB-

The

dentate

ligament

The

dentate

ligament

is

a

white

fibrous

sheet

that

extends

from

the

pia

mater

medially

to

the

dura

mater

laterally

It

forms

arches

leaving

passage

to

the

VA

for

the

first

one

and

the

second

cervical

nerve

root

for

the

second

one

Our

classification

system

of

foramen

magnum

meningiomas

Meningiomas

are

considered

to

be

located

in

the

FM

area

if

their

base

of

insertion

is

mainly

located

within

the

FM

limits

This

definition

excludes

tumors

invading

secondarily

the

FM

region

-LRB-

Figure

-RRB-

Fig.

of

foramen

magnum

meningiomas

Foramen

magnum

meningiomas

are

classified

according

to

their

compartment

of

development

their

dural

insertion

and

their

relation

to

the

vertebral

artery

The

relation

to

the

vertebral

artery

permits

to

anticipate

the

displacement

of

the

lower

cranial

nerves

Tumors

growing

below

the

vertebral

artery

push

the

lower

cranial

nerves

at

the

superior

aspect

of

the

lesion

On

the

other

hand

tumors

developed

above

or

on

both

sides

of

the

vertebral

artery

displace

the

lower

cranial

nerves

in

all

directions

and

their

position

can

then

not

be

anticipated

Three

basic

surgical

approaches

are

used

The

extent

of

bone

removal

is

delimited

by

the

dotted

lines

The

definitive

objective

of

a

classification

system

is

to

define

preoperatively

the

surgical

strategy

based

on

preoperative

imaging

characteristics

of

the

lesion

The

surgical

strategy

in

cases

of

FMMs

is

the

surgical

approach

but

also

the

anticipation

of

modified

vital

structure

position

In

our

classification

system

FMMs

can

be

classified

according

to

their

compartment

of

development

their

dural

insertion

and

to

their

relation

to

the

VA

-LSB-

-RSB-

According

to

the

compartment

of

development

FMMs

can

be

subdivided

in

IntraduralExtraduralIntra

and

extradural

Intradural

meningiomas

are

the

most

commonly

observed

Extradural

meningiomas

like

at

any

other

locations

are

very

invasive

into

the

bone

the

nerves

and

vessels

sheaths

and

soft

tissues

The

VA

sheath

and

even

its

adventitia

can

also

be

infiltrated

This

raises

some

difficulties

and

explains

the

higher

incidence

of

incomplete

removal

as

compared

to

intradural

meningiomas

-LSB-

-RSB-

According

to

the

insertion

on

the

dura

FMMs

can

be

defined

in

the

antero-posterior

plane

as

Anterior

if

insertion

is

on

both

sides

of

the

anterior

midlineLateral

if

insertion

is

between

the

midline

and

the

dentate

ligamentPosterior

if

insertion

is

posterior

to

the

dentate

ligament

Anterior

meningiomas

push

the

spinal

cord

posteriorly

Therefore

the

surgical

opening

between

the

neuraxis

and

the

FM

lateral

wall

is

narrow

and

the

drilling

must

extend

to

the

medial

part

of

the

FM

lateral

wall

to

improve

the

access

In

almost

every

case

no

drilling

of

the

lateral

mass

of

the

atlas

and

occipital

condyle

is

necessary

Exceptionally

anterior

meningiomas

of

small

size

without

anterior

compartment

enlargement

need

more

bone

resection

but

never

includes

more

than

one

fifth

of

these

elements

On

the

other

hand

lateral

meningiomas

displace

the

neuraxis

posterolaterally

and

widely

open

the

surgical

access

therefore

the

drilling

has

never

to

be

extended

into

the

lateral

mass

of

the

atlas

or

the

occipital

condyle

Finally

surgical

strategies

vary

according

to

the

relation

to

the

VA

FMM

having

the

possibility

to

develop

Above

the

VABelow

the

VAOn

both

sides

of

the

VA

Meningiomas

are

more

often

located

below

the

VA.

In

this

case

the

lower

cranial

nerves

are

always

pushed

cranially

and

posteriorly

There

is

no

need

to

look

for

them

They

will

come

into

view

on

reaching

the

superior

tumoral

part

On

the

other

hand

if

the

lesion

grows

above

the

VA

the

position

of

the

lower

cranial

nerves

can

not

be

anticipated

the

nerves

may

be

displaced

separately

in

any

direction

After

partial

debulking

of

the

tumor

one

has

to

look

for

them

so

as

to

identify

and

protect

them

during

the

tumor

resection

In

case

of

tumoral

development

on

both

sides

of

the

VA

a

similar

problem

may

exist

with

the

position

of

the

lower

cranial

nerves

Moreover

the

dura

around

the

VA

penetration

may

be

infiltrated

by

the

tumor

As

previously

mentioned

the

dura

is

normally

adherent

to

the

adventitia

and

complete

resection

of

the

tumor

at

this

level

is

hazardous

In

this

case

which

is

rarely

observed

it

may

be

safer

to

leave

a

cuff

of

infiltrated

dura

around

the

VA

and

to

coagulate

this

zone

Surgical

aspects

Preoperative

and

perioperative

considerations

Standard

preoperative

workup

includes

magnetic

resonance

imaging

-LRB-

MRI

-RRB-

computed

tomography

-LRB-

CT

-RRB-

scan

and

sometimes

angiography

On

MRI

gadolinium-enhanced

sequences

help

to

precisely

delimit

the

dural

attachment

zone

the

tumor

and

its

relation

to

neural

and

vascular

structures

On

images

the

presence

of

an

arachnoid

plane

between

the

tumor

and

the

neuraxis

is

sometimes

visible

Bone

windows

CT

scan

is

helpful

in

case

of

extradural

extension

to

investigate

bone

erosion

and

to

schedule

preoperatively

the

need

for

fusion

Conventional

angiography

is

generally

useless

There

are

only

two

indications

for

preoperative

angiography

If

a

highly

vascularized

tumor

is

suspected

and

embolization

is

contemplatedTo

perform

a

balloon

occlusion

test

in

case

of

VA

encasement

-LRB-

extradural

or

recurrent

meningioma

and

meningioma

inserted

around

the

VA

-RRB-

In

our

experience

it

has

never

been

necessary

to

occlude

the

VA.

Intraoperative

neurophysiological

monitorings

have

been

used

by

several

surgeons

-LSB-

-RSB-

and

includes

somatosensory-evoked

potentials

brainstem

auditory-evoked

potentials

and

electromyographic

monitoring

of

lower

cranial

nerves

by

recordings

through

an

endotracheal

tube

-LRB-

CN

X

-RRB-

and

with

a

needle

in

the

sterno-mastoid

-LRB-

SM

-RRB-

muscle

-LRB-

CN

XI

-RRB-

and

the

tongue

-LRB-

CN

XII

-RRB-

Surgical

approaches

and

techniques

at

Lariboisière

Hospital

The

midline

posterior

approach

The

midline

posterior

approach

is

indicated

for

posterior

meningiomas

whatever

their

intra

and

extradural

extension

if

they

remain

posterior

to

the

plane

of

the

dentate

ligament

and

medial

to

the

VA

-LSB-

-RSB-

In

such

cases

the

neuraxis

is

pushed

anteriorly

The

patient

may

be

in

the

sitting

ventral

or

lateral

position

To

decrease

venous

bleedings

the

sitting

position

is

preferred

at

Lariboisière

Hospital

as

far

as

there

is

no

contraindication

such

as

a

patent

foramen

ovale

air

embolism

is

prevented

by

hypervolemia

and

G-suit

The

skin

is

incised

on

the

midline

from

the

occipital

protuberance

down

to

the

upper

cervical

region

The

midline

avascular

plane

is

opened

between

the

posterior

muscles

up

to

the

occipital

protuberance

and

down

to

the

spinous

process

of

Bone

opening

is

performed

using

a

drill

and

Kerrison

rongeurs

and

is

always

limited

to

the

lower

part

of

the

occipital

bone

and

the

posterior

arch

of

the

atlas

The

dura

is

then

incised

in

a

T

or

Y-shaped

fashion

and

retracted

with

stitches

Postero-lateral

approach

The

postero-lateral

approach

is

preferred

for

any

intradural

process

located

laterally

and/or

anteriorly

to

the

neuraxis

and

for

extradural

lesions

developed

on

the

posterior

part

of

the

lateral

FM

wall

-LSB-

-RSB-

For

tumors

extending

far

beyond

the

anterior

midline

the

postero-lateral

approach

has

the

advantage

to

allow

a

bilateral

approach

in

the

same

stage

-LRB-

Fig.

and

-RRB-

Fig.

c

Preoperative

MRI

A

large

lateral

foramen

magnum

meningioma

displaces

the

neuraxis

d

e

Postoperative

CT

scan

The

meningioma

has

been

completely

resected

The

spinal

cord

has

regained

a

normal

shape

f

Reconstructed

CT

scan

after

contrast

administration

The

resection

of

the

posterior

arch

of

the

atlas

is

visible

on

the

right

side

The

lateral

mass

of

the

atlas

-LRB-

star

-RRB-

was

left

intact

The

vertebral

artery

-LRB-

arrow

-RRB-

has

been

elevated

from

the

posterior

arch

-LRB-

compare

with

the

left

side

-RRB-

during

the

dissectionFig

b

Preoperative

MRI

A

large

anterior

foramen

magnum

meningioma

severely

compresses

the

neuraxis

which

is

reduced

to

a

crescent

-LRB-

star

-RRB-

c

d

Postoperative

MR

images

confirm

the

complete

resection

of

the

tumorFig

steps

during

a

postero-lateral

approach

a

The

left

vertebral

artery

segment

-LRB-

black

arrow

-RRB-

has

been

elevated

from

the

lateral

part

of

the

posterior

arch

-LRB-

white

arrowhead

-RRB-

The

medial

portion

has

been

resected

up

to

the

midline

-LRB-

black

arrowhead

-RRB-

The

dural

entrance

of

the

vertebral

artery

where

the

segment

becomes

the

one

is

delineated

by

the

dotted

line

b

The

dura

matter

has

been

incised

The

inferior

contraincision

extends

inferiorly

to

the

site

of

entrance

of

the

vertebral

artery

into

the

dura

matter

The

posterior

rootlets

are

identified

-LRB-

black

arrowhead

-RRB-

The

inferior

portion

of

the

meningioma

-LRB-

white

star

-RRB-

severely

compresses

the

spinal

cord

-LRB-

black

star

-RRB-

c

The

vertebral

artery

segment

-LRB-

white

arrow

-RRB-

the

spinal

accessory

nerve

-LRB-

black

arrowheads

-RRB-

and

the

XIIth

cranial

nerve

-LRB-

white

arrowhead

-RRB-

have

been

controlled

Of

note

the

dura

matter

-LRB-

black

star

-RRB-

is

stretched

over

the

left

lateral

mass

by

a

stitch

to

enlarge

the

lateral

access

and

after

the

occipital

craniotomy

the

fall

of

the

left

cerebellum

is

prevented

by

a

blade

-LRB-

white

star

-RRB-

d

After

the

complete

removal

of

the

meningioma

both

vertebral

arteries

are

visible

On

the

left

side

we

observe

the

section

of

a

feeding

vessel

-LRB-

white

arrow

-RRB-

The

right

PICAs

is

visible

-LRB-

black

arrow

-RRB-

as

well

as

the

Xth

-LRB-

black

star

-RRB-

and

the

XIIth

-LRB-

black

arrowhead

-RRB-

cranial

nerves

The

postero-lateral

approach

is

a

lateral

extension

of

the

midline

posterior

approach

The

patient

must

be

carefully

positioned

in

the

same

position

as

during

a

posterior

midline

approach

The

head

must

be

placed

in

neutral

position

Any

flexion

must

be

avoided

because

it

decreases

the

space

in

front

of

the

neuraxis

and

therefore

may

worsen

the

compression

and

the

neurological

condition

The

vertical

midline

skin

incision

is

identical

but

the

incision

is

curved

laterally

on

the

tumoral

side

just

below

the

occipital

protuberance

toward

the

mastoid

process

The

posterior

muscles

are

divided

along

the

occipital

crest

and

retracted

laterally

to

expose

the

occipital

bone

the

posterior

arch

of

the

atlas

and

the

lamina

if

required

The

exposure

may

be

extended

on

a

limited

way

on

the

contralateral

side

VA

exposure

At

this

step

the

VA

running

above

needs

to

be

exposed

to

safely

resect

the

posterior

arch

up

to

the

lateral

mass

The

exposure

of

the

horizontal

segment

of

the

VA

segment

progresses

from

the

midline

of

the

posterior

arch

of

the

atlas

laterally

toward

the

atlas

groove

The

medial

border

of

the

groove

is

clearly

marked

by

a

step

with

a

decrease

in

the

height

of

the

posterior

arch

The

safest

way

to

expose

the

VA

is

to

dissect

strictly

in

the

subperiosteal

plane

The

periosteum

of

the

posterior

arch

needs

to

be

elevated

from

medial

to

lateral

and

inferiorly

to

superiorly

Working

in

this

manner

permits

to

expose

the

posterior

aspect

of

the

posterior

arch

of

the

atlas

to

bring

into

view

the

step

at

the

medial

end

of

the

groove

and

then

to

elevate

the

VA

from

the

atlas

groove

In

fact

the

VA

segment

is

surrounded

by

a

venous

plexus

both

artery

and

veins

are

enclosed

in

a

periosteal

sheath

Both

provide

protection

against

VA

damage

If

tearing

occurs

venous

bleedings

can

be

controlled

by

direct

bipolar

coagulation

on

the

VA

periosteal

sheath

Dissection

at

the

superior

aspect

of

the

VA

is

more

difficult

because

there

is

no

good

landmark

and

the

periosteal

sheath

is

in

continuity

with

the

ligaments

covering

the

occipital

condyle

Cutting

of

the

ligaments

must

proceed

a

few

millimeters

above

the

VA

on

the

occipital

condyle

by

following

the

superior

aspect

of

the

VA

sheath

The

occipitoatlantal

membrane

covering

the

groove

of

the

posterior

arch

of

the

atlas

can

be

calcified

or

ossified

turning

the

groove

into

a

tunnel

raising

some

difficulties

to

expose

the

horizontal

portion

at

this

level

-LSB-

-RSB-

After

being

fully

exposed

the

VA

can

be

gently

displaced

superiorly

to

show

the

lateral

mass

of

the

atlas

Bone

opening

The

posterior

arch

of

the

atlas

is

resected

with

rongeurs

from

the

midline

toward

the

transverse

process

To

obtain

a

decompression

of

the

neuraxis

before

the

tumoral

resection

the

posterior

arch

of

the

atlas

must

also

be

resected

beyond

the

midline

toward

the

controlateral

side

By

this

way

hyperpressure

induced

even

by

gentle

manipulation

during

resection

are

not

transmitted

to

the

neuraxis

The

lower

part

of

the

occipital

bone

is

drilled

or

resected

with

rongeurs

laterally

toward

the

sigmoid

sinus

and

also

beyond

the

midline

The

lateral

extension

of

the

bone

opening

is

established

according

to

the

position

of

the

meningioma

In

case

of

lateral

meningiomas

the

spinal

cord

is

displaced

toward

the

contralateral

side

and

then

any

resection

of

the

FM

lateral

wall

is

not

necessary

In

case

of

anterior

meningiomas

the

spinal

cord

is

pushed

posteriorly

and

the

surgical

corridor

has

to

be

enlarged

laterally

by

drilling

up

to

the

medial

side

of

the

lateral

mass

and/or

the

occipital

condyle

Drilling

further

the

lateral

mass

of

the

atlas

or

the

occipital

condyle

is

exceptionally

necessary

In

the

exceptional

case

where

the

opening

must

be

enlarged

no

more

than

of

the

medial

part

of

the

FM

lateral

wall

has

to

be

drilled

In

such

a

way

stabilization

is

never

required

The

cranio-caudal

bone

resection

is

scheduled

according

to

the

position

of

the

tumor

regarding

to

the

VA.

The

drilling

has

to

be

extended

toward

the

lateral

mass

of

the

atlas

if

the

tumor

grows

below

the

VA

to

the

jugular

tubercle

and

the

occipital

condyle

if

it

grows

above

and

toward

both

parts

of

the

FM

lateral

wall

if

it

encircles

the

VA

on

both

sides

Dura

opening

The

most

adequate

dural

incision

is

a

curvilinear

incision

starting

at

the

inferolateral

corner

then

running

vertically

at

a

paramedian

level

-LRB-

to

mm

from

the

midline

-RRB-

and

curving

toward

the

superolateral

corner

This

type

of

incision

permits

to

take

the

maximum

benefit

of

the

bone

opening

without

contraincision

and

is

generally

easy

to

close

Keeping

the

dura

over

the

neuraxis

provides

protection

during

the

surgical

dissection

Moreover

arachnoid

connections

between

the

dura

and

the

medulla

are

left

undissected

to

prevent

an

anterior

fall

of

the

neuraxis

during

tumor

resection

Intradural

step

Lateral

meningiomas

are

directly

brought

into

view

and

their

dural

attachment

directly

accessible

Contrarily

anterior

meningiomas

are

partially

hidden

by

the

neuraxis

The

first

step

of

the

intradural

stage

before

beginning

tumor

resection

is

to

identify

several

important

structures

and

to

open

the

surgical

access

to

the

lesion

by

completely

releasing

the

neuraxis

Important

structures

are

the

VA

the

accessory

nerve

and

the

dentate

ligament

The

VA

is

identified

by

following

the

course

of

the

segment

where

it

pierces

the

dura

matter

The

first

two

digits

of

the

dentate

ligament

have

to

be

divided

To

further

improve

the

surgical

access

the

first

cervical

nerve

root

can

be

divided

distal

to

its

connections

with

the

accessory

nerve

At

this

step

the

surgical

technique

must

be

individualized

according

to

the

tumor

location

above

below

or

on

both

sides

of

the

VA.

As

previously

mentioned

in

cases

of

tumor

developed

below

the

VA

the

lower

cranial

nerves

are

always

pushed

cranially

and

posteriorly

by

the

tumor

These

nerves

will

then

be

found

at

the

superior

pole

of

the

lesion

at

the

end

of

the

surgery

The

resection

must

start

at

the

caudal

aspect

of

the

meningioma

with

the

goal

to

release

the

dural

attachment

and

to

suppress

the

vascular

supply

first

then

the

tumor

is

debulked

in

a

dry

surgical

field

with

a

sucker

an

ultrasound

aspirator

or

a

laser

according

to

the

tumor

consistency

When

liberating

the

dural

insertion

it

is

important

to

keep

undetached

a

small

part

of

the

base

at

the

side

of

the

neuraxis

to

avoid

free

movement

of

the

lesion

which

can

be

responsible

for

inadvertent

damage

to

the

neuraxis

during

the

remnant

resection

When

hollowing

the

tumor

a

small

layer

is

also

kept

with

its

capsule

against

the

neuraxis

This

part

will

be

resected

at

the

last

surgical

step

and

under

better

conditions

when

the

meningioma

is

completely

devascularized

and

the

surgical

field

widely

open

If

the

tumor

is

developed

above

the

VA

two

special

points

must

be

taken

into

consideration

the

displacement

of

the

lower

cranial

nerves

and

the

dissection

of

the

VA

branches

Indeed

in

such

location

the

displacement

of

the

lower

cranial

nerves

can

not

be

anticipated

To

prevent

damage

the

rootlets

must

be

under

control

on

the

side

of

the

jugular

foramen

and

then

followed

along

their

courses

more

or

less

adherent

to

the

meningioma

With

the

lesion

being

progressively

debulked

the

nerve

rootlets

can

be

more

easily

mobilized

often

inferiorly

to

allow

a

more

confident

tumor

resection

at

some

distance

from

fragile

nervous

structures

The

tumor

dissection

from

the

VA

branches

especially

the

PICA

is

another

difficulty

encountered

only

with

tumors

developed

above

the

VA.

Precise

knowledge

of

the

patient

anatomy

based

on

preoperative

investigation

is

mandatory

If

the

meningioma

encases

the

VA

the

technique

is

identical

as

described

above

Special

consideration

is

nevertheless

required

if

the

meningioma

has

its

insertion

on

the

dura

surrounding

the

VA

penetration

The

dural

resection

is

better

achieved

by

progressing

from

the

extradural

side

toward

the

intradural

aspect

along

the

VA

because

the

VA

invaginates

into

the

dura

with

its

periosteal

sheath

This

furrow

can

be

resected

as

much

as

the

VA

adventitia

is

not

invaded

Dural

closure

A

watertight

dural

closure

is

required

to

prevent

a

postoperative

cerebrospinal

fluid

-LRB-

CSF

-RRB-

leakage

The

closure

is

generally

easy

with

the

curvilinear

incision

If

necessary

a

dural

patch

using

the

suboccipital

aponeurosis

achieves

a

perfect

closure

In

any

case

the

muscular

and

aponeurosis

layers

must

be

tightly

closed

Antero-lateral

approach

The

antero-lateral

approach

is

rarely

used

in

our

department

as

we

consider

that

it

is

a

good

choice

only

in

some

meningiomas

with

extradural

extension

through

the

bony

structures

-LSB-

-RSB-

The

antero-lateral

approach

to

the

craniocervical

junction

has

been

extensively

described

in

the

article

focusing

on

the

surgical

exposure

of

the

VA

segment

and

will

not

be

detailed

again

for

this

reason

-LSB-

-RSB-

Some

points

required

nevertheless

special

consideration

The

head

has

to

be

slightly

extended

with

a

rotation

of

toward

the

opposite

side

Because

of

this

rotation

VA

segments

above

and

below

the

posterior

arch

run

parallel

separated

by

this

bone

Opening

the

transverse

foramen

is

mandatory

for

VA

transposition

Bone

opening

When

completely

liberated

the

VA

can

be

pulled

out

and

transposed

bringing

into

view

the

FM

lateral

wall

as

the

occipital

condyle

the

anterior

and

posterior

arches

of

the

atlas

the

lateral

mass

of

the

atlas

and

the

joint

become

visible

The

exposure

must

now

be

adapted

to

each

case

depending

on

the

location

and

extension

of

the

meningioma

The

odontoid

process

can

be

reached

by

passing

over

the

joint

The

mastoid

process

can

be

resected

and

small

bridging

bone

removed

to

open

completely

the

jugular

foramen

from

the

end

of

the

sigmoid

sinus

to

the

jugular

tubercle

just

underneath

the

junction

with

the

jugular

bulb

up

to

the

beginning

of

the

internal

jugular

vein

Dura

opening

The

dural

opening

is

most

of

the

time

out

of

concern

because

the

antero-lateral

approach

is

mainly

indicated

for

extradural

meningiomas

When

lesions

are

developed

in

both

extradural

and

intradural

compartment

the

dura

is

already

opened

by

the

lesion

and

must

only

be

enlarged

Dural

closure

Dural

closure

can

be

a

considerable

problem

in

cases

where

the

dural

defect

is

anteriorly

located

at

the

level

of

the

clivus

the

anterior

arch

of

the

atlas

and

the

odontoid

process

Postoperative

complications

The

antero-lateral

approach

could

induce

a

transient

dysfunction

of

the

accessory

nerve

by

the

nerve

manipulation

responsible

for

pain

along

the

trapezius

muscle

and

weakness

of

the

trapezius

muscle

and/or

the

SM

muscle

During

this

approach

manipulation

of

the

sympathetic

chain

could

also

be

at

the

origin

of

a

transient

Horner

's

syndrome

VA

damage

has

never

been

observed

In

case

of

tumoral

encasement

a

balloon

occlusion

test

must

be

realized

Preservation

of

the

lower

CNs

can

be

hazardous

If

CN

IX

and

X

are

damaged

postoperative

swallowing

problems

must

be

anticipated

Review

of

the

literature

Published

series

Yasargil

has

reviewed

series

published

from

to

and

counted

cases

of

FMMs

Since

then

more

than

cases

of

FMMs

have

been

reported

in

the

literature

-LSB-

-RSB-

George

et

al.

-LSB-

-RSB-

reported

on

a

series

in

the

French

literature

of

craniocervical

meningiomas

from

hospitals

The

largest

single-center

series

have

been

published

by

Meier

et

al.

-LSB-

-RSB-

in

Samii

et

al.

-LSB-

-RSB-

in

and

George

et

al.

-LSB-

-RSB-

in

Table

summarizes

published

series

over

the

last

years

in

the

English

literature

Table

of

the

literature

of

published

series

of

FMMs

over

the

last

years

in

the

English

literatureAuthorYearNb

ptFMM

location

-LRB-

-RRB-

Recurrence

-LRB-

-RRB-

Va

encasement

-LRB-

-RRB-

ApproachVA

transpResection

JTPartial

mastNb

CR

-LRB-

-RRB-

Extent

CRInstability

-LRB-

-RRB-

Outcome

-LRB-

-RRB-

Resection

-LRB-

-RRB-

Transient

morbidity

-LRB-

-RRB-

Permanent

morbidity

-LRB-

-RRB-

Mortality

-LRB-

-RRB-

FURecurr

-LRB-

-RRB-

Sen

FL

SO

Marin

TO

SO

Y

-LRB-

-RRB-

CR

Condyle

resection

EL

extreme-lateral

FMM

foramen

magnum

meningioma

FL

far

lateral/postero-lateral

FU

follow-up

JT

jugular

tubercle

mast

mastoidectomy

Lat

lateral

Nb

number

pt

patient

Recurr

recurrence

SO

suboccipital

TC

transcond

dylar

TO

transoral

transp

transposition

VA

vertebral

artery

Y

yes

Heterogenicity

of

published

series

A

heterogenous

group

of

patients

constituted

the

published

studies

Several

studies

included

not

only

FMMs

but

also

other

FM

pathologies

such

as

neurofibromas

schwannomas

as

well

as

other

various

lesions

leading

result

analysis

precarious

-LSB-

-RSB-

Table

summarizes

also

the

high

variability

of

tumor

location

rate

of

VA

encasement

rate

of

tumor

recurrence

and

surgical

approaches

The

proportion

of

anterior

FMMs

is

comprised

between

-LSB-

-RSB-

and

-LSB-

-RSB-

The

subdivision

between

anterior

and

lateral

FMM

is

not

always

detailed

in

studies

including

to

of

antero-lateral

FMMs

-LSB-

-RSB-

Posterior

FMMs

were

always

included

in

studies

with

anterior

or

antero-lateral

lesions

with

a

variable

proportion

from

up

to

-LSB-

-RSB-

The

rate

of

VA

encasement

can

be

higher

than

and

the

rate

of

tumor

recurrence

up

to

-LSB-

-RSB-

-LRB-

Table

-RRB-

Surgical

approaches

extent

of

bone

resection

and

need

for

fusion

FMMs

are

undoubtedly

challenging

tumors

requiring

special

considerations

because

of

the

vicinity

of

the

brainstem

medulla

oblongata

lower

cranial

nerves

and

the

VA.

Several

approaches

have

been

advocated

The

definite

goals

are

to

achieve

the

largest

tumor

removal

and

the

lowest

morbidity

rate

as

possible

Minimizing

the

morbidity

is

obtained

by

choosing

the

appropriate

exposure

The

approach

must

allow

adequate

controls

of

important

neurovascular

structures

without

exposing

to

unnecessary

risks

There

is

no

discussion

about

the

best

surgical

approach

of

posterior

FMMs

The

posterior

approach

is

the

best

option

is

well

known

by

neurosurgeons

and

is

associated

with

a

low

morbidity

rate

The

debate

about

the

best

surgical

approach

is

more

open

for

lateral

and

mainly

anterior

FMMs

The

transoral

approach

has

been

reported

sporadically

-LSB-

-RSB-

Despite

providing

access

to

the

anterior

part

of

the

craniocervical

junction

this

approach

has

several

drawbacks

in

case

of

intradural

lesions

increased

risk

of

CSF

fistula

and

meningitis

after

crossing

of

the

contaminated

oral

cavity

poor

access

to

laterally

extending

tumors

resulting

in

a

low

rate

of

complete

resection

and

increased

risk

of

posteroperative

instability

and

velopalatine

insufficiency

-LSB-

-RSB-

The

two

main

surgical

approaches

reported

in

the

literature

are

the

far-lateral

approach

-LSB-

-RSB-

also

called

postero-lateral

approach

or

lateral

suboccipital

approach

and

the

extreme-lateral

approach

also

named

antero-lateral

approach

As

detailed

by

Rhoton

-LSB-

-RSB-

the

far-lateral

approach

is

a

lateral

suboccipital

approach

directed

behind

the

sternocleidomastoid

muscle

and

the

VA

and

just

medial

to

the

occipital

and

atlantal

condyles

and

the

atlanto-occipital

joint

The

extreme

lateral

approach

is

a

direct

lateral

approach

deep

to

the

anterior

part

of

the

sternocleidomastoid

muscle

and

behind

the

internal

jugular

vein

along

the

front

of

the

VA.

In

fact

both

approaches

permit

drilling

of

the

occipital

condyle

but

provide

a

different

exposure

because

of

the

differences

in

the

approach

direction

The

extreme-lateral

transcondylar

approach

for

FMMs

was

first

reported

by

Sen

and

Sekhar

-LSB-

-RSB-

in

Further

publications

of

the

same

experienced

skull

base

surgeons

followed

-LSB-

-RSB-

Salas

et

al.

-LSB-

-RSB-

reported

in

several

variations

of

the

extreme-lateral

approach

based

on

a

series

of

patients

including

meningiomas

The

lesions

were

removed

most

of

the

time

through

a

partial

transcondylar

approach

and

more

rarely

through

transfacetal

retrocondylar

and

extreme

transjugular

approaches

During

the

partial

transcondylar

approach

the

posterior

one

third

of

occipital

condyle

and

superior

facet

of

were

drilled

away

These

authors

also

performed

a

partial

mastoidectomy

-LSB-

-RSB-

Arnautovic

et

al.

-LSB-

-RSB-

published

their

experience

in

on

a

series

of

ventral

FMMs

They

used

also

the

extreme-lateral

transcondylar

approach

The

condyle

drilling

ranged

approximately

from

one

third

to

one

half

of

the

condyle

without

causing

craniocervical

instability

The

extreme-lateral

trancondylar

approach

requires

the

VA

transposition

to

reach

and

drill

the

occipital

condyle

-LSB-

-RSB-

As

others

-LSB-

-RSB-

we

advocate

rather

the

postero-lateral

approach

also

called

far-lateral

approach

even

for

anterior

intradural

FMMs

During

this

approach

the

VA

is

controlled

in

the

horizontal

portion

of

the

segment

above

the

posterior

arch

VA

transposition

is

rarely

performed

and

has

only

been

reported

in

one

series

-LSB-

-RSB-

The

extent

of

FM

lateral

wall

drilling

is

variable

in

fact

directly

proportional

to

the

tumor

extension

to

the

contralateral

side

In

the

literature

the

occipital

condyle

resection

varies

between

and

-LSB-

-RSB-

In

a

recent

publication

Bassiouni

-LSB-

-RSB-

classified

judiciously

surgical

approaches

in

two

groups

transcondylar

or

retrocondylar

if

the

occipital

condyle

is

not

drilled

In

our

review

of

the

literature

-LRB-

Table

-RRB-

we

found

nine

series

in

which

the

retrocondylar

approaches

was

used

to

reach

anterior

or

anterolateral

meningiomas

-LSB-

-RSB-

In

four

of

these

series

a

retrocondylar

approach

was

not

used

in

all

cases

but

in

and

-LSB-

-RSB-

The

five

other

series

are

homogeneous

and

only

included

patients

treated

through

a

retrocondylar

approach

-LSB-

-RSB-

Of

these

three

studies

reported

complete

resection

in

of

the

cases

-LSB-

-RSB-

In

the

two

others

complete

resection

was

noted

in

and

of

the

cases

and

the

remaining

lesions

were

resected

subtotally

-LSB-

-RSB-

Surgical

results

were

good

and

surgical

morbidity

and

mortality

rates

low

-LSB-

-RSB-

Extradural

lesions

can

be

treated

either

by

posterolateral

or

anterolateral

approach

-LRB-

Fig.

-RRB-

The

extent

of

drilling

during

this

procedure

can

be

larger

but

is

only

dictated

by

the

tumoral

invasion

and

must

be

limited

to

the

destroyed

or

invaded

bone

In

such

a

way

the

question

of

instability

is

only

a

preoperative

concern

In

our

experience

of

tumors

located

at

the

craniocervical

junction

we

have

not

observed

any

instability

if

less

than

half

of

the

and

joints

were

resected

-LSB-

-RSB-

In

our

experience

VA

transposition

was

merely

performed

in

selected

cases

of

FMMs

with

extradural

extension

and

never

for

intradural

lesions

Surgical

results

Morbidity

mortality

prognosis

factors

In

the

Yasargyl

's

review

of

the

literature

of

series

published

before

the

overall

mortality

rate

was

approximately

but

could

be

as

high

as

in

some

series

-LSB-

-RSB-

Over

the

last

years

the

overall

mortality

is

The

mortality

rate

is

comprised

between

and

-LRB-

Table

-RRB-

Mortality

rates

higher

than

were

mainly

observed

in

small

series

-LSB-

-RSB-

In

the

Yasargil

's

review

a

good

outcome

was

noted

in

and

a

fair

and

poor

outcome

respectively

in

and

In

series

larger

than

ten

patients

published

over

the

last

years

-LRB-

Table

-RRB-

neurological

improvement

stability

and

worsening

were

noted

respectively

in

and

of

the

cases

The

permanent

morbidity

rate

is

comprised

between

and

The

permanent

morbidity

rate

is

lower

through

a

far-lateral

approach

-LRB-

-RRB-

either

transcondylar

or

retrocondylar

than

through

an

extreme-lateral

transcondylar

approach

-LRB-

considering

series

without

recurrent

tumor

-RRB-

Lower

cranial

nerves

dysfunctions

are

the

most

frequently

encountered

preoperative

deficits

These

deficits

have

the

propensity

to

recover

even

completely

postoperatively

-LSB-

-RSB-

except

in

cases

of

en

plaque

meningiomas

or

recurrent

tumor

-LSB-

-RSB-

Several

factors

lead

the

surgical

procedure

still

more

difficult

then

influencing

negatively

the

morbidity

rate

anterior

tumor

location

-LSB-

-RSB-

tumor

size

-LRB-

smaller

lesions

are

more

difficult

to

resect

because

the

surgical

corridor

is

small

-RRB-

tumor

invasiveness

extradural

extension

-LSB-

-RSB-

VA

encasement

-LSB-

-RSB-

absence

of

arachnoidal

sheath

-LSB-

-RSB-

and

adherences

in

recurrent

lesions

-LSB-

-RSB-

Rate

of

tumoral

resection

Based

on

a

multicentric

study

from

hopitals

George

et

al.

-LSB-

-RSB-

reported

and

respectively

of

complete

subtotal

and

partial

removals

Over

the

last

years

most

of

the

studies

reported

complete

or

subtotal

removal

of

the

tumor

-LSB-

-RSB-

Factors

limiting

the

resection

completeness

are

adherences

of

the

lesion

to

vital

structures

VA

encasement

and

invasiveness

of

the

lesion

Adherences

are

observed

during

repeated

surgery

and

explain

the

lower

rate

of

complete

tumor

resection

-LRB-

of

Simpson

grade

-RRB-

in

surgical

series

in

which

a

high

rate

of

recurrent

tumors

are

included

-LSB-

-RSB-

Eventually

in

recurrent

tumors

some

authors

advocate

leaving

a

small

tumor

remnant

to

preserve

a

low

morbidity

rate

-LSB-

-RSB-

On

the

other

hand

Arnautovic

et

al.

-LSB-

-RSB-

favored

radical

removal

of

recurrent

tumors

with

the

goal

of

providing

a

relatively

long

and

stable

postoperative

course

even

at

the

price

of

frequent

but

transient

morbidity

induced

by

lower

cranial

nerves

dysfunction

Arnautovic

et

al.

-LSB-

-RSB-

have

also

demonstrated

that

the

rate

of

complete

removal

is

higher

at

first

surgery

than

when

treating

recurrence

advising

then

to

be

more

aggressive

at

the

first

surgical

presentation

VA

encasement

was

noted

in

to

in

some

series

-LSB-

-RSB-

This

factor

was

recognized

as

an

independent

factor

of

incomplete

removal

-LSB-

-RSB-

The

location

of

the

meningioma

either

intraextradural

or

extradural

reflects

the

tumoral

invasiveness

These

tumors

are

less

favorable

to

be

completely

resected

than

pure

intradural

lesions

-LSB-

-RSB-

In

the

French

cooperative

study

-LSB-

-RSB-

the

rate

of

complete

removal

of

intradural

extradural

and

intraextradural

meningiomas

was

respectively

and

Our

experience

Our

experience

has

been

published

in

after

the

treatment

of

FMMs

operated

in

the

period

-LSB-

-RSB-

Twenty-four

lesions

were

intradural

two

were

extradural

and

four

were

intraextradural

Eighteen

were

considered

anterior

lateral

and

one

was

posterior

The

tumor

was

above

the

VA

in

four

cases

below

in

cases

and

on

both

sides

in

cases

The

posterolateral

approach

was

used

in

cases

the

anterolateral

one

in

five

cases

and

the

posterior

midline

in

four

cases

The

rates

of

complete

resection

for

intradural

and

extradural

lesions

were

respectively

and

Postoperatively

the

clinical

condition

improves

in

of

patients

remains

stable

in

and

worsened

in

Our

present

experience

over

the

last

years

is

now

based

on

FMMs

-LRB-

unpublished

data

-RRB-

Complete

removal

was

achieved

in

and

subtotal

removal

in

Subtotal

removals

were

due

to

extradural

extension

or

to

recurrent

cases

The

rate

of

complete

removal

increased

up

to

when

selecting

only

intradural

lesions

treated

at

first

presentation

We

mainly

use

the

far-lateral

retrocondylar

approach

for

intradural

FMMs

In

some

cases

the

drilling

of

the

FM

lateral

wall

has

to

be

performed

for

intradural

anterior

meningiomas

but

remains

limited

at

worst

to

the

medial

of

the

FM

lateral

wall

Whatever

this

extent

of

drilling

has

to

be

tailored

according

to

the

tumor

characteristics

We

consider

nevertheless

that

more

bone

resection

is

never

necessary

because

of

the

anatomical

anterior

position

of

the

lateral

mass

of

the

atlas

and

the

occipital

condyle

Our

attitude

has

been

reinforced

by

cadaveric

study

which

has

demonstrated

that

increasing

the

bone

drilling

is

not

associated

with

a

significant

widening

of

the

surgical

corridor

-LSB-

-RSB-

In

fact

resecting

one

third

and

one

half

of

the

occipital

condyle

increases

the

visibility

respectively

by

and

Two

anatomic

reports

have

demonstrated

that

condyle

resection

allows

a

wider

angle

of

exposure

to

gain

the

anterior

foramen

area

-LSB-

-RSB-

However

these

studies

did

not

consider

the

fact

that

in

surgical

approaches

to

anterior

lesions

space-occupying

lesions

can

enlarge

the

surgical

corridor

We

consider

that

the

extreme-lateral

approach

could

be

associated

with

a

higher

morbidity

rate

than

the

far-lateral

approach

The

exposure

allowed

by

the

far-lateral

retrocondylar

or

partial

transcondylar

approach

is

adequate

for

resecting

even

anterior

intradural

FMMs

The

supposed

benefit

in

term

of

exposure

provided

by

the

extreme

transcondylar

approach

is

counterbalanced

by

the

risks

associated

with

the

CN

XI

dissection

the

VA

transposition

and

the

condyle

drilling

Conclusions

FMMs

are

challenging

tumors

in

the

vicinity

of

the

brainstem

the

VA

and

lower

cranial

nerves

Several

surgical

approaches

are

possible

each

one

with

specific

indications

The

drilling

of

the

FM

lateral

wall

required

during

the

approaches

is

always

limited

and

by

itself

should

not

be

at

the

origin

of

any

instability

Postoperative

complications

can

be

dramatic

and

must

be

anticipated

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

foramen magnum
meningioma
surgical approach
tumor
vertebral artery


How long does it take to coil an intracranial aneurysm ? Introduction The change in the treatment of choice for intracranial aneurysms from clipping to coiling has been associated with an important change in logistics . The time needed for coiling is variable and depends on many factors . In this study , we assessed the procedural time for the coiling of 642 aneurysms and tried to identify predictors of a long procedural time . Introduction Coiling of intracranial aneurysms has become the treatment of choice and has partly replaced neurosurgical clipping in most neurosurgical centers -LSB- 1 -- 3 -RSB- . This change in treatment modality has been associated with an important change in logistics : patients are no longer treated in the operating room but in the radiology department . Coiling of intracranial aneurysms has to fit into the program of the angiography suite and an anesthetic team has to leave the operating room complex to assist in coiling . Since many aneurysms are treated acutely after subarachnoid hemorrhage -LRB- SAH -RRB- , planning may be difficult . The time slot needed for coiling is variable and depends on many factors such as complexity of the aneurysm , the number of aneurysms that should be treated , the experience and skills of the treating endovascular team and local preferences . In this study , we assessed the procedural time for coiling of 642 aneurysms and tried to identify predictors of a long procedural time . Patients and methods Patients From January 1998 to September 2005 , 817 aneurysms were coiled . The starting point of the study was chosen because of installation of a new biplane angiographic unit -LRB- Integris 3000 BN Neuro , Philips Medical Systems , Best , The Netherlands -RRB- at the end of 1997 . We excluded 65 patients -LRB- with 146 aneurysms -RRB- with more than one aneurysm coiled in the same session . Of the remaining 671 aneurysms , 642 had complete imaging data available for review . The time of each angiographic run was printed on the images automatically . The procedural time for coiling was defined as the number of minutes between the first diagnostic angiographic run and the last angiographic run after embolization . Thus , induction of general anesthesia and catheterization of the first vessel were not included in the procedural time . In the vast majority of patients , 3-D rotational angiography -LRB- 3DRA -RRB- of the vessel harboring the aneurysm was performed -LSB- 4 -RSB- . Many patients with acute SAH confirmed on CT scan were immediately transferred to the angiography suite and underwent complete diagnostic angiography and coiling of the aneurysm under general anesthesia . Only in patients with unruptured aneurysms , was diagnostic angiography usually available before coiling , and in these patients only 3DRA was performed during the process of coiling . Of the 642 patients , 178 were men and 464 were women with a mean age of 52.9 years -LRB- median 52 years , range 19 -- 83 years -RRB- . Of the 642 aneurysms , 523 had ruptured and 119 had not . Among the 523 patients with a ruptured aneurysm at the time of treatment , clinical condition was Hunt and Hess -LRB- HH -RRB- I/II in 337 , HH IV/V in 68 , and HH III in 118 . The mean aneurysm size was 8.0 mm -LRB- range 2 -- 55 mm -RRB- . The aneurysm was located in the posterior circulation in 154 , in the anterior cerebral artery in 246 , in the middle cerebral artery in 46 , and in the carotid artery in 196 patients . The type of coil used was mostly Guglielmi detachable coils -LRB- GDC ; Boston Scientific , Fremont , Calif. -RRB- , followed by TruFill/Orbit coils -LRB- Cordis Neurovascular , Miami Lakes , Fl. -RRB- and straight coils 50 cm long -LRB- Cook Detach , Cook , Copenhagen , Denmark -RRB- for large and giant aneurysms -LSB- 5 -RSB- . A supportive device was used during coiling in 60 aneurysms , a supportive balloon in 55 , a TriSpan in 4 , and a stent in 1 aneurysm -LSB- 6 -RSB- . In 26 aneurysms a procedural rupture occurred . Complications leading to permanent neurological deficit or death occurred in 40 patients -LSB- 7 , 8 -RSB- . Statistical analysis To assess possible predictors of a long procedural time , we defined a long procedural time as the upper quartile of the procedural times -LRB- 70 -- 158 min -RRB- and performed logistic regression analysis for the following variables : male gender , age greater than the median age of 52 years , ruptured aneurysm , aneurysm size in the upper quartile -LRB- 10 -- 55 mm -RRB- , occurrence of procedural rupture , HH grade III -- V , occurrence of procedural morbidity defined as complications leading to death or permanent neurological deficit -LSB- 7 , 8 -RSB- , use of a supportive device , location on the anterior cerebral artery , carotid artery or middle cerebral artery , and location in the posterior circulation . Subsequently , to identify independent predictors , multiple logistic regression analysis was performed for all significant predictors . To assess whether recent technical developments had influenced procedural time , we compared the mean procedural time of the first 321 aneurysms with the mean procedural time of the last 321 aneurysms using a t-test . In addition , we assessed whether the implementation of 3DRA in October 2000 had influenced procedural time . Results The mean procedural time was 57.3 min -LRB- median 52 min , range 15 -- 158 min -RRB- . More than half of the coiling procedures lasted between 30 and 60 min -LRB- Fig. 1 -RRB- , 49 procedures -LRB- 7.6 % -RRB- lasted less than 30 min , and 68 procedures -LRB- 10.6 % -RRB- lasted more than 90 min . Fig. 1Procedural times in minutes for 642 coiling procedures displayed as number of procedures in 15-min time periods Median and mean procedural times with ranges and standard deviations for aneurysm coiling procedures in relation to patient and aneurysm characteristics are summarized in Table 1 . The predictors of a long procedural time are displayed in Table 2 . The use of a supportive device was the strongest predictor of a long procedural time -LRB- OR 5.4 -RRB- , followed by the occurrence of procedural morbidity -LRB- OR 4.5 -RRB- , a large aneurysm size -LRB- OR 3.0 -RRB- , and patient age -LRB- OR 1.5 -RRB- . A poor clinical condition of the patient , rupture status of the aneurysm , gender , occurrence of procedural rupture , aneurysm location , and implementation of 3DRA had no influence on procedural time . Multiple logistic regression analysis identified the use of a supportive device , occurrence of procedural morbidity , and large aneurysm size as independent predictors of a long procedural time . Table 1Procedural times for all 642 aneurysms in relation to patient and aneurysm characteristicsVariableNo . of aneurysmsProcedural time -LRB- min -RRB- MedianMeanRangeStandard deviationAall aneurysms64257 .352.015 -- 15824.1 Use of supportive device6080 .580.235 -- 15030.7 Procedural morbidity4072 .575.628 -- 15830.7 Aneurysm size in upper quartile -LRB- 10 -- 55 mm -RRB- 1636470.525 -- 15826.4 Age more than median 52 years3215560 .717 -- 15825.0 Hunt and Hess grade III -- V1865459 .218 -- 12222.6 Ruptured aneurysm5235258 .116 -- 15824.6 Male gender1825560 .417 -- 13123.8 Procedural rupture265053 .816 -- 10721.3 Aneurysm location Middle cerebral artery465361 .819 -- 13126.8 Posterior circulation1545461 .722 -- 14627.1 Anterior cerebral artery24653 .557.116 -- 11221.2 Carotid artery1964853 .115 -- 15823.9 Implementation of 3-D angiography Before1675258 .618 -- 15825.5 After4755256 .915 -- 14623.7 Table 2Odds ratios with 95 % confidence intervals for different variables for the upper quartile of procedural times -LRB- 70 -- 158 min -RRB- VariableOdds ratio95 % CIUse of supportive device5 .403.11 -- 9.34 Procedural morbidity4 .492.33 -- 8.64 Aneurysm size in upper quartile -LRB- 10 -- 55 mm -RRB- 3.032.06 -- 4.45 Age more than median age1 .471.02 -- 2.10 Hunt and Hess grade III -- V1 .320.88 -- 1.97 Ruptured aneurysm1 .410.87 -- 2.30 Male gender0 .790.54 -- 1.16 Procedural rupture0 .730.27 -- 1.98 Aneurysm location Middle cerebral artery1 .810.97 -- 3.40 Posterior circulation1 .300.87 -- 1.95 Anterior cerebral artery0 .930.65 -- 1.35 Carotid artery0 .680.46 -- 1.02 Implementation of 3D angiography1 .110.74 -- 1.66 The mean procedural time for the first 321 coil procedures was 56.5 min -LRB- median 51 min , range 18 -- 158 min -RRB- and for the last 321 this was 58.1 min -LRB- median 54 min , range 15 -- 124 min -RRB- . This difference was not significant -LRB- t-test , P = 0.40 -RRB- Discussion In this study , the mean procedural time for coiling was 57 min . Most procedures were performed within 1 h. Procedural time was defined as the time between the first and the last angiographic run , since this time period could easily be assessed from time prints on the images . The time for patient preparation , anesthetic care , insertion of angiographic sheet and catheterization of the first vessel were not included in the procedural time . In our department , this additional time is usually between 30 and 45 min . This means that the typical time needed for coiling of an intracranial aneurysm is around one and a half hours , varying from one to two hours . A long procedural time was associated with the use of a supportive device , occurrence of procedural morbidity and large aneurysm size . Although coiling of middle cerebral artery aneurysms tended to take more time and coiling of carotid artery aneurysms tended to take less time , these differences were just not statistically significant . The strongest predictor of a long procedural time was the use of a supportive device , mostly a supportive balloon -LSB- 6 -RSB- . When the use of a supportive device is not anticipated from the beginning of the procedure , an additional guiding catheter must be placed in the groin and navigated to the vessel harboring the aneurysm , or the guiding catheter has to be changed for a catheter with larger inner lumen . In addition , the balloon catheter has to be prepared and navigated across the neck of the aneurysm and this may be time consuming since 0.010-inch guidewires are usually difficult to steer . Another predictor of a long procedural time was large aneurysm size . In larger aneurysms a higher number of coils can usually be inserted and the accumulated electrolytic detachment time thus increases . The last predictor of a long procedural time was the occurrence of morbidity -LRB- not the occurrence of procedural rupture -RRB- . Most morbidity is caused by thromboembolic complications . Several actions may be undertaken when such a complication occurs , such as mechanical thrombus fragmentation and selective injection of thrombolytic drugs , which both lead to a longer procedural time . It is of note that no difference in procedural time was found between the earlier and later procedures , despite the technical advances in microcatheters and guidewires and increased experience . In both groups , there was no difference in mean aneurysm size -LRB- 8.7 versus 7.2 mm -RRB- , use of a supportive device -LRB- both 30 -RRB- or occurrence of morbidity -LRB- both 20 -RRB- . We did not include the first 3 years of coiling in our hospital because the time was not printed on the images by the angiographic equipment used during that period . The mean procedural time may have been longer on the steep side of the learning curve during those first 3 years . In our high-volume department , logistics have been optimized . In patients scheduled for coiling , an intravenous line and urinary catheter are placed on the ward , the treating endovascular team is experienced , a biplane angiographic unit with 3DRA is available , all catheters and devices needed are available in the angiography room , microcatheters and guidewires are prepared by technicians , and in recent years the puncture site is closed with a dedicated device . For coiling of large and giant aneurysms , we use for the most part mechanically detachable coils 50 cm long . All anesthetists involved in coil procedures were experienced , with no residents in training . Our time slot for anesthesia is in the afternoon from 1300 to 1600 hours with a `` deadline '' at 16.30 , after which time an anesthetist on call has to be notified to take over care . With these logistics we normally plan two patients , and regularly treat three patients within this time slot . Both of the senior authors -LRB- M.S. and W.J.v.R -RRB- have performed many coil procedures in four other hospitals in The Netherlands . The procedural time may differ greatly between centers , depending on many factors such as availability of single - or biplane angiographic equipment and 3DRA , the experience of the operator , supporting technicians and anesthetic team , and local preferences such as liberal or restricted use of supportive devices . Conclusion With optimal logistics , coiling of most intracranial aneurysms can be performed in one to two hours , including patient handling before and after the actual coiling procedure .

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

intracranial aneurysms
coiling
procedural time