Title: Congenital vertebral anomaly

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'''Congenital vertebral anomalies''' are a collection of malformations of the [[vertebral column|spine]]. Most, around 85%, are not clinically significant, but they can cause compression of the [[spinal cord]] by deforming the vertebral canal or causing instability. This condition occurs in the womb. Congenital vertebral anomalies include alterations of the shape and number of [[vertebra]]e.

==Lumbarization and sacralization==
[[File:Lumbarization of S1.jpg|thumb|130px|Lumbarization of [[sacrum|sacral vertebra 1]], seen as 6 vertebrae that do not connect to [[ribs]].]]

''Lumbarization'' is an [[anatomic variation|anomaly]] in the [[human vertebral column|spine]]. It is defined by the nonfusion of the first and second segments of the [[sacrum]]. The [[lumbar spine]] subsequently appears to have six [[vertebrae]] or segments, not five. This sixth [[lumbar vertebra]] is known as a [[transitional vertebra]]. Conversely the sacrum appears to have only four segments instead of its designated five segments. Lumbosacral transitional vertebrae consist of the process of the last lumbar vertebra fusing with the first [[sacral segment]].&lt;ref name = &quot;A Review of Symptomatic Lumbosacral Transitional Vertebrae&quot;&gt;{{Cite journal | title = A Review of Symptomatic Lumbosacral Transitional Vertebrae: Bertolotti's Syndrome| pmc=4603258 | pmid=26484005 | doi=10.14444/2042 | volume=9 | year=2015 | journal=Int J Spine Surg | pages=42 | last1 = Jancuska | first1 = JM | last2 = Spivak | first2 = JM | last3 = Bendo | first3 = JA}}&lt;/ref&gt; While only around 10 percent of adults have a spinal abnormality due to [[genetics]], a sixth lumbar vertebra is one of the more common abnormalities. &lt;ref name=&quot;Lumbarization&quot;&gt;Dorland's Medical Dictionary&lt;/ref&gt;

[[File:Sacralization of the fifth lumbar vertebra.jpg|thumbnail|left|150px|Sacralization of the L5 vertebra is seen at the lower right of the image.]]
''Sacralization of the fifth lumbar vertebra'' (or ''sacralization'') is a [[congenital anomaly]], in which the [[transverse process]] of the last [[lumbar vertebra]] (L5) fuses to the [[sacrum]] on one side or both, or to [[Ilium (bone)|ilium]], or both. These anomalies are observed in about 3.5 percent of people, and it is usually bilateral but can be unilateral or incomplete ([[ipsilateral]] or [[contralateral]] rudimentary facets) as well. Although sacralization may be a cause of [[low back pain]], it is asymptomatic in many cases (especially bilateral type). Low back pain in these cases most likely occurs due to [[biomechanics]]. In sacralization, the L5-S1 [[intervertebral disc]] may be thin and narrow. This abnormality is found by [[X-ray]].{{cn|date=October 2020}} 

Sacralization of L6 means L6 attaches to S1 via a rudimentary joint. This L6-S1 joint creates additional motion, increasing the potential for motion-related stress and lower back pain/conditions. This condition can usually be treated without surgery, injecting steroid medication at the pseudoarticulation instead. Additionally, if L6 fuses to another vertebra this is increasingly likely to cause lower back pain.&lt;ref name = &quot;The Sixth Lumbar Vertebrae: The Anatomy Behind the Rare Extra Bone&quot;&gt;{{Cite web | url = http://www.spinalcord.com/blog/the-sixth-lumbar-vertebrae-the-anatomy-behind-the-rare-extra-bone | title = Spinal Cord, Inc|website=Spinalcord.com | access-date = November 27, 2016 }}&lt;/ref&gt; The presence of a sixth vertebra in the space where five vertebrae normally reside also decreases the flexibility of the spine and increases the likelihood of injury.&lt;ref name = &quot;The L6 Vertebra&quot;&gt;{{Cite web | url = https://www.laserspineinstitute.com/back_problems/vertebrae/l6/ | title = Laser Spine Institute | access-date = November 27, 2016 | archive-url = https://web.archive.org/web/20161128200724/https://www.laserspineinstitute.com/back_problems/vertebrae/l6/ | archive-date = November 28, 2016 | url-status = dead }}&lt;/ref&gt;

==Hemivertebrae==
Hemivertebrae are wedge-shaped vertebrae and therefore can cause an angle in the spine (such as [[kyphosis]], [[scoliosis]], and [[lordosis]]).
Among the congenital vertebral anomalies, hemivertebrae are the most likely to cause [[neurology|neurologic]] problems.&lt;ref name=Braund&gt;{{cite web|author=Braund, K.G.|year=2003|title=Developmental Disorders|work=Clinical Neurology in Small Animals: Localization, Diagnosis and Treatment|url=http://www.ivis.org/special_books/Braund/braund16/chapter_frm.asp?LA=1#Vertebral_Anomalies|access-date=2007-02-04}}&lt;/ref&gt; The most common location is the mid[[thoracic vertebrae]], especially the eighth (T8).&lt;ref name=Jeffrey&gt;{{cite journal |vauthors=Jeffery N, Smith P, Talbot C |title=Imaging findings and surgical treatment of hemivertebrae in three dogs |journal=J Am Vet Med Assoc |volume=230 |issue=4 |pages=532–6 |year=2007 |pmid=17302550 |doi=10.2460/javma.230.4.532|doi-access=free }}&lt;/ref&gt; Neurologic signs result from severe angulation of the spine, narrowing of the spinal canal, instability of the spine, and luxation or fracture of the vertebrae. Signs include rear limb weakness or paralysis, urinary or fecal incontinence, and spinal pain.&lt;ref name=Braund/&gt; Most cases of hemivertebrae have no or mild symptoms, so treatment is usually conservative. Severe cases may respond to surgical spinal cord decompression and vertebral stabilization.&lt;ref name=Jeffrey/&gt;

Recognised associations are many and include:
[[Aicardi syndrome]],
[[cleidocranial dysostosis]],
[[gastroschisis]] 3,
[[Gorlin syndrome]],
[[fetal pyelectasis]] 3,
[[Jarcho-Levin syndrome]],
[[OEIS complex]],
[[VACTERL association]].&lt;ref&gt;{{Cite web|url=https://radiopaedia.org/articles/hemivertebra|title=Hemivertebra &amp;#124; Radiology Reference Article|first=Yuranga|last=Weerakkody|website=Radiopaedia.org|date=27 April 2011 |access-date=26 April 2022}}&lt;/ref&gt;

The probable cause of hemivertebrae is a lack of blood supply causing part of the vertebrae not to form.
Hemivertebrae in [[dog]]s are most common in the tail, resulting in a [[screw]] shape.{{cn|date=October 2020}}

==Block vertebrae==
Block vertebrae occur when there is improper segmentation of the vertebrae, leading to parts of or the entire vertebrae being fused. The adjacent vertebrae fuse through their intervertebral discs and also through other intervertebral joints so that it can lead to blocking or stretching of the exiting nerve roots from that segment. It may lead to certain neurological problems depending on the severity of the block. It can increase stress on the inferior and the superior intervertebral joints. It can lead to an abnormal angle in the spine, there are certain syndromes associated with block vertebrae; for example, [[Klippel–Feil syndrome]]. The [[sacrum]] is a normal block vertebra.&lt;ref&gt;{{Cite journal |last1=Yì Xiáng J Wáng |last2=Santiago |first2=Fernando Ruiz |last3=Deng |first3=Min |last4=Nogueira-Barbosa |first4=Marcello H |date=2017 |title=Identifying osteoporotic vertebral endplate and cortex fractures |journal=Quantitative Imaging in Medicine and Surgery |language=en |volume=7 |issue=5 |pages=555–591 |doi=10.21037/qim|doi-broken-date=1 July 2025 |doi-access=free |pmid=29184768 |pmc=5682396 }}&lt;/ref&gt;

===Fossil record===
{{Main article|Paleopathology}}
Evidence for block vertebrae found in the fossil record is studied by [[paleopathologists]], specialists in ancient disease and injury. A block vertebra has been documented in ''T. rex''. This suggests that the basic development pattern of vertebrae goes at least as far back as the most recent common ancestor of [[archosaurs]] and [[mammals]]. The tyrannosaur's block vertebra was probably caused by a &quot;failure of the [[resegmentation]] of the [[sclerotome]]s&quot;.&lt;ref name=&quot;molnar-paleopathology&quot;&gt;Molnar, R. E., 2001, Theropod paleopathology: a literature survey: In: Mesozoic  Vertebrate Life, edited by Tanke, D. H., and Carpenter, K., Indiana University  Press, p. 337-363.&lt;/ref&gt;

&lt;gallery&gt;
File:Blockwirbel degenerativ.jpg|Block vertebrae of the cervical spine (vertebrae 4 and 5). Probably based on degenerative or inflammatory changes.
File:Block- und Halbwirbel.jpg|Several congenital block vertebrae in the transition from the thoracic to the lumbar spine and hemivertebrae.
File:Partieller Blockwirbel.jpg|Congenital block vertebra in the lumbar spine (partial vertebrae 3 and 4). The rear portion of the disc still exists.
File:Blockwirbel CT VR frontal.jpg|Congenital block vertebra of the lumbar spine. CT volume rendering.
File:Blockwirbel CT VR seitlich.jpg|Congenital block vertebra of the lumbar spine. CT volume rendering.
&lt;/gallery&gt;

==Butterfly vertebrae==
Butterfly vertebrae have a sagittal cleft through the body of the vertebrae and a funnel shape at the ends. This gives the appearance of a [[butterfly]] on an [[x-ray]]. It is caused by persistence of the [[notochord]] (which usually only remains as the center of the [[intervertebral disc]]) during vertebrae formation. There are usually no symptoms. There are also coronal clefts mainly in skeletal dysplasias such as chondrodysplasia punctata. In dogs, butterfly vertebrae occur most often in Bulldogs, Pugs, and Boston Terriers.&lt;ref name=Ettinger_1995&gt;{{cite book|author=Ettinger, Stephen J.|author2=Feldman, Edward C.|title=Textbook of Veterinary Internal Medicine|edition=4th|publisher=W.B. Saunders Company|year=1995|isbn=0-7216-6795-3}}&lt;/ref&gt;

&lt;gallery&gt;
File:Schmetterlingswirbel.jpg|Butterfly vertebra (red). Normal vertebra for comparison (blue).
File:Volume rendering of CT of butterfly vertebrae.jpg|[[Volume rendering]] of a [[CT scan]] of the lumbar vertebral column, showing butterfly vertebrae at several levels, most typically in L1.
&lt;/gallery&gt;

==Transitional vertebrae==
[[Image:Stummelrippe LWK1.jpg|thumb|right|Short ribs at the first lumbar vertebra, which is thus a transitional vertebra, since lumbar vertebrae normally do not have ribs attached to them.]]
Transitional vertebrae have the characteristics of two types of vertebra. The condition usually involves the vertebral arch or [[transverse processes]]. It occurs at the cervicothoracic, thoracolumbar, or lumbosacral junction. For instance, the transverse process of the last [[cervical vertebra]] may resemble a rib. A transitional vertebra at the lumbosacral junction can cause [[arthritis]], disk changes, or thecal sac compression. Back pain associated with lumbosacral transitional vertebrae (LSTV) is known as [[Bertolotti's syndrome]]. One study found that male [[German Shepherd Dog]]s with a lumbosacral transitional vertebra are at greater risk for [[cauda equina syndrome]], which can cause rear limb weakness and incontinence.&lt;ref name=&quot;Flückiger&quot;&gt;{{cite journal |vauthors=Flückiger M, Damur-Djuric N, Hässig M, Morgan J, Steffen F |title=A lumbosacral transitional vertebra in the dog predisposes to cauda equina syndrome |journal=Vet Radiol Ultrasound |volume=47 |issue=1 |pages=39–44 |year=2006 |pmid=16429983 |doi=10.1111/j.1740-8261.2005.00103.x}}&lt;/ref&gt;

The significance of transitional vertebrae has been questioned by one study finding similar prevalence in the general population as those with low back pain,&lt;ref name=&quot;pmid21951610&quot;&gt;{{cite journal |vauthors=Apazidis A, Ricart PA, Diefenbach CM, Spivak JM |title=The prevalence of transitional vertebrae in the lumbar spine |journal=Spine J |volume=11 |issue=9 |pages=858–62 |date=September 2011 |pmid=21951610 |doi=10.1016/j.spinee.2011.08.005 |url=}}&lt;/ref&gt; but more recent study found a large difference.&lt;ref name=&quot;pmid34791784&quot;&gt;{{cite journal |vauthors=Jin L, Yin Y, Chen W, Zhang R, Guo J, Tao S, Guo Z, Hou Z, Zhang Y |title=Role of the Lumbosacral Transition Vertebra and Vertebral Lamina in the Pathogenesis of Lumbar Disc Herniation |journal=Orthop Surg |volume=13 |issue=8 |pages=2355–2362 |date=December 2021 |pmid=34791784 |pmc=8654657 |doi=10.1111/os.13122 |url=}}&lt;/ref&gt;

==Spina bifida==
[[Spina bifida]] is characterized by a midline cleft in the vertebral arch. It usually causes no symptoms in dogs. It is seen most commonly in Bulldogs and [[Manx (cat)|Manx]] cats.&lt;ref name=Braund/&gt; In Manx it accompanies a condition known as sacrocaudal dysgenesis that gives these cats their characteristic tailless or stumpy tail appearance. It is inherited in Manx as an [[autosomal dominant]] trait.&lt;ref name=Merck&gt;{{cite web | title = Congenital and Inherited Anomalies of the Nervous System: Small Animals | work = The Merck Veterinary Manual | year = 2006 | url = http://www.merckvetmanual.com/mvm/index.jsp?cfile=htm/bc/100416.htm | access-date = 2007-02-04 }}&lt;/ref&gt;

==Associations==
Vertebral anomalies is associated with an increased incidence of some other specific anomalies as well, together being called the [[VACTERL association]]:&lt;ref name=&quot;Solomon 2011 p. 56&quot;&gt;{{cite journal | last=Solomon | first=Benjamin D | title=VACTERL/VATER Association | journal=Orphanet Journal of Rare Diseases | publisher=Springer Science and Business Media LLC | volume=6 | issue=1 | year=2011 | issn=1750-1172 | doi=10.1186/1750-1172-6-56 | page=56| pmid=21846383 | doi-access=free | pmc=3169446 }}&lt;/ref&gt;
* V – Vertebral anomalies
* A – [[Anal atresia]]
* C – [[Cardiovascular anomalies]]
* T – [[Tracheoesophageal fistula]]
* E – [[Esophageal atresia]]
* R – [[Kidney|Renal (kidney)]] and/or [[Radius (bone)|radial]] anomalies
* L – Limb defects
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==References==
{{Reflist}}

== External links ==
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{{Congenital malformations and deformations of musculoskeletal system}}

[[Category:Dog musculoskeletal disorders]]
[[Category:Congenital disorders of musculoskeletal system]]