Small Animal Radiology and Ultrasound: A Diagnostic Atlas and Text

676 Small Animal Radiolo g y and Ultrasono graphy
Fig. 6-12 A 7-year-old male Cocker
Spaniel with paresis of the hind
limbs. The myelogram revealed no
spinal cord abnormalities in the thorax,
but numerous vertebrae and ribs
have large, expansile lesions that are
calcified. Diagnosis: Multiple cartilaginous
exostoses.
Spina Bifida. Spina bifida is a condition with a midline cleft in the vertebral arch, which
may involve one or several adjacent vertebrae. 42 There may be two incomplete spinous
processes or a complete absence of the spinous process. Paired bone densities may be seen
on either side of the midline in the ventrodorsal view. These bone densities represent the
ununited dorsal arch. 68 The condition may be totally asymptomatic or may be associated
with other neurologic defects such as meningocele or meningomyelocele (Fig. 6-13).
Myelography usually is required to identify those animals in which a neural tube defect is
present. Spina bifida may occur at any level of the vertebral column but is observed most
often in the caudal lumbar or sacral spine. Some defects are associated with specific breeds.
For example, syringomyelia and spinal dysraphism may cause gait problems in
Weimaraners. 42 Manx cats and brachycephalic dogs are predisposed to sacrococcygeal
deformities ranging from multiple hemivertebrae or spina bifida or both to sacral dysgenesis.
42,68-70 In some cases these defects will have neurologic manifestations such as posterior
paresis and urinary or fecal incontinence (Fig. 6-14).
C E RV I C A L V E RT E B R A L M A L F O R M AT I O N
Cervical vertebral malformation, wobbler syndrome, is seen most frequently in older
Doberman Pinschers and young Great Danes, although dogs of any age and several different
breeds may be affected. 71-75 The radiographic changes are slightly different in the young
Great Danes when compared with those of the older Doberman Pinschers. The clinical signs
may be due to a number of anatomical abnormalities, including intervertebral disc prolapse,
hypertrophy of the vertebral ligaments (ligamentum flavum or dorsal longitudinal ligament),
stenosis of the spinal canal, synovial proliferation associated with the spinal articular
facets, enlargement of the articular facets, and misalignment of the vertebral bodies. 76 In
young dogs, malformation and misalignment of the vertebral bodies are the most commonly
identified abnormalities. The vertebral bodies are abnormally shaped, losing their
normal rectangular conformation and becoming narrower ventrally. The cranioventral and
caudoventral margins of the vertebral bodies become flattened. There is spondylosis deformans,
with bridging osteophytes forming between the adjacent vertebral bodies. The cranial
orifices of the vertebrae may become narrowed, producing a wedge-shaped spinal
canal. 71,72,75 The radiographic abnormalities most often affect the caudal cervical vertebrae
(C5-C7). However, in severe cases the more cranial vertebral bodies may be affected. The
joint spaces of the caudal cervical vertebrae have a more vertical orientation, which is similar
to that of the thoracic vertebrae rather than the oblique orientation typical of normal