Congenital vertebral anomaly
Congenital vertebral anomalies are a collection of malformations of the 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 vertebrae.
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 neurologic problems.[1] The most common location is the midthoracic vertebrae, especially the eighth (T8).[2] 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.[1] 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.[2] Associations Recognised associations are many and include: Aicardi syndrome, cleidocranial dysostosis, gastroschisis 3, Gorlin syndrome, fetal pyelectasis 3, Jarcho-Levin syndrome, OEIS complex, VACTERL association.[3]
The probable cause of hemivertebrae is a lack of blood supply causing part of the vertebrae not to form. Hemivertebrae in dogs are most common in the tail, resulting in a screw shape.
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.
Fossil record
Evidence for block vertebrae found in the fossil record is studied by paleopathologists, specialists in ancient disease and injury. A block vertebrae 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 "failure of the resegmentation of the sclerotomes."[4]
Gallery
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Block vertebrae of the cervical spine (vertebrae 4 and 5). Probably based on degenerative or inflammatory changes. -
Several congenital block vertebrae in the transition from the thoracic to the lumbar spine and hemivertebrae. -
Congenital block vertebra in the lumbar spine (partial vertebrae 3 and 4). The rear portion of the disc still exists. -
Congenital block vertebra of the lumbar spine. CT volume rendering. -
Congenital block vertebra of the lumbar spine. CT volume rendering.
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. Butterfly vertebrae occur most often in Bulldogs, Pugs, and Boston Terriers.[5]
Transitional vertebrae
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 spinal cord compression. Back pain associated with lumbosacral transitional vertebrae (LSTV) is known as Bertolotti's syndrome. One study found that male German Shepherd Dogs with a lumbosacral transitional vertebra are at greater risk for cauda equina syndrome, which can cause rear limb weakness and incontinence.[6]
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 cats.[1] 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.[7]
References
- ^ a b c Braund, K.G. (2003). "Developmental Disorders". Clinical Neurology in Small Animals: Localization, Diagnosis and Treatment. Retrieved 2007-02-04.
- ^ a b Jeffery N, Smith P, Talbot C (2007). "Imaging findings and surgical treatment of hemivertebrae in three dogs". J Am Vet Med Assoc. 230 (4): 532–6. doi:10.2460/javma.230.4.532. PMID 17302550.
- ^ http://radiopaedia.org/articles/hemivertebra
- ^ 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.
- ^ Ettinger, Stephen J.; Feldman, Edward C. (1995). Textbook of Veterinary Internal Medicine (4th ed.). W.B. Saunders Company. ISBN 0-7216-6795-3.
- ^ Flückiger M, Damur-Djuric N, Hässig M, Morgan J, Steffen F (2006). "A lumbosacral transitional vertebra in the dog predisposes to cauda equina syndrome". Vet Radiol Ultrasound. 47 (1): 39–44. doi:10.1111/j.1740-8261.2005.00103.x. PMID 16429983.
- ^ "Congenital and Inherited Anomalies of the Nervous System: Small Animals". The Merck Veterinary Manual. 2006. Retrieved 2007-02-04.