The crooked spine: Congenital and developmental spinal disorders (Proceedings)
Gait evaluation in the pediatric patient can initially be difficult as puppies first learn to walk and the myelination process matures. As development progresses spinal disorders may become more apparent. Numerous congenital abnormalities resulting in spinal malformation exist. Spinal malformations most commonly are asymptomatic. However, spinal malformations may lead to mild or significant dysfunction.
Hemivertebrae are wedge shaped vertebrae, with the base oriented ventrally, dorsally or medially. A hemivertebra occurs when a portion of the vertebra does not form, typically the vertebral body. Failure of the central portion of the vertebra to form may result in hemivertebrae on both sides and is called a butterfly vertebra. Hemivertebrae are common in screw tail breeds. Traumatic and pathologic fractures should be distinguished from hemivertebrae as they can appear similar.1,2 Hemivertebrae can lead to severe spinal angulation resulting in kyphosis, scoliosis or lordosis.2 Plain radiographs may diagnosis vertebral anomalies. However, myelography, CT or MR imaging are required to assess the degree of spinal cord compression. Non steroidal anti-inflammatory (NSAID) therapy may be of benefit if pain or mild paresis is present. If NSAID therapy is unsuccessful or if paresis is severe then prednisone therapy at anti-inflammatory dosages (0.5 mg/kg PO BID initially and then tapered) may be successful. If paresis is severe or if progressive despite medical therapy, then surgical decompression ± stabilization is recommended. The prognosis with surgery may be guarded due to concurrent spinal malformations,2 and chronicity.1
Block vertebrae result from embryonic failure of segmentation. Block vertebrae are typically shorter than the sum of the individual segments. Differential diagnoses for block vertebrae include vertebral fusion following a previous fracture, discospondylitis or previous disk surgery.1,2Transitional vertebrae occur at the junction of the divisions of the vertebral column. The thoracolumbar junction is commonly affected, with unilateral or bilateral defects. The thirteenth thoracic vertebra may have a short thick transverse process instead of a rib. Less commonly, the first lumbar vertebrae may have a rib instead of a transverse process.1 Transitional vertebrae at the thoracolumbar junction do not appear to cause a significant clinical problem. However, the last rib is commonly used for localization during the surgical approach for hemilaminectomy. Thus, a malformation at this location could lead to an inappropriate surgical location. Identification of thoracolumbar vertebrae is more difficult via MR imaging. With the increasing availability and use of MR imaging this should be considered.