Sheila Carrera‐Justiz and Gabriel Garcia University of Florida, Gainesville, FL, USA Congenital spinal malformations, specifically hemivertebrae, have been long recognized in veterinary medicine [1, 2]. Hemivertebrae are the most frequently noted vertebral malformation in “screw‐tailed dogs,” a group that traditionally includes French Bulldogs, English Bulldogs, Pugs, and Boston Terriers [3]. This topic has become more important to the veterinary profession in recent years with the increasing popularity of screw‐tailed dogs, the French Bulldog in particular. The prevalence of thoracic hemivertebra in neurologically normal French and English Bulldogs has been reported to be as high as 93.5% and 73.2%, respectively [4]. A large proportion of hemivertebrae are subclinical and never require intervention [5] (Figure 13.1). French Bulldogs were shown to have a significantly higher incidence of hemivertebrae than English Bulldogs and Pugs [6]. The same study noted that Pugs are more likely to have ventral hypoplasia and kyphosis, putting Pugs into a different category of hemivertebrae than English and French Bulldogs. Most dogs affected by vertebral body malformations tend to show clinical signs in the first year of life [7]. Clinical signs are reflective of a myelopathy and are dependent on the specific location of the malformation; signs can include ataxia, paresis, scoliosis, lordosis, kyphosis, and incontinence. The cause of the myelopathy in these dogs remains unknown and is thought to be secondary to findings that cause intermittent compression and ischemia of the spinal cord, including stenosis of the spinal canal, spinal cord tethering, and microinstability. In Pug breeds, severe kyphosis, and fewer hemivertebrae have been associated with a higher likelihood of neurological disease. A Cobb angle greater than 35° has been shown to have the highest sensitivity and specificity for predicting clinical signs in dogs [8, 9]. Figure 13.1 A sagittal computed tomography image of a dog spine illustrating the concept that multiple malformations are less likely to cause a severe kyphosis. Congenital vertebral abnormalities can be visualized with various modalities, including radiographs, myelography, computed tomography, and magnetic resonance imaging (MRI). Radiographs serve as a good screening tool for vertebral body malformations and can be used to calculate Cobb angles (Figure 13.2); however, as neural structures cannot be visualized on plain radiographs, advanced imaging is recommended if there is any evidence of a myelopathy. While myelography can highlight spinal cord compression, it cannot show intramedullary changes. As such, cross‐sectional imaging is often chosen over traditional myelography. Computed tomography is an excellent modality for evaluation of bony malformations and allows for the creation of three‐dimensional models, digital or 3‐D printed (Figure 13.3). MRI is most useful for evaluation of the spinal cord parenchyma and any associated abnormalities. Given their ability to provide clinically significant data regarding the various different aspects of the spinal column, Computed tomography (CT) and MRI are often recommended in combination for complete evaluation of a case prior to surgery. Figure 13.2 A sagittal computed tomography image of a dog spine with a vertebral malformation causing a Cobb angle of 40.9. Considering the high incidence of these malformations in commonly affected breeds, it is important to evaluate the entire neuroanatomic segment affected to prevent overlooking an additional lesion that may be partially or completely responsible for the clinical signs. Various protocols of medical management have been used for treatment of myelopathy due to congenital vertebral malformations. Dogs affected with a mild and non‐progressive myelopathy can be treated with conservative management [10]. More recent data suggests that outcomes are quite poor with medical management, with all dogs showing progression of neurological signs despite treatment [11]. It has been suggested that some mildly affected dogs stabilize, and even improve, in their clinical signs when vertebral growth ceases around nine months of age [10]. This concept suggests that surgical intervention in young dogs should be considered after approximately nine months of age. Surgical intervention in these cases has historically been fraught with complications and variable outcomes. Affected dogs are often skeletally immature animals with limited purchase in soft bone and markedly abnormal anatomy. Traditionally, management with decompressive surgery alone has been considered to hold a guarded to poor prognosis.
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Surgical Management of Congenital Spinal Anomalies
Diagnostics
Treatment
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