Computed tomographic myelography for assessment of the cervical spinal cord in ataxic warmblood horses: 26 cases (2015-2017).

OBJECTIVE: To quantify the degree of dural compression and assess the association between site and direction of compression and articular process (AP) size and degree of dural compression with CT myelography. ANIMALS: 26 client-oriented horses with ataxia. PROCEDURES: Spinal cord-to-dura and AP-to-cross-sectional area of the C6 body ratios (APBRs) were calculated for each noncompressive site and site that had > 50% compression of the subarachnoid space. Site of maximum compression had the largest spinal cord-to-dura ratio. Fisher exact test and linear regression analyses were used to assess the association between site and direction of compression and mean or maximum APBR and spinal cord-todura ratio, respectively. RESULTS: Mean ± SD spinal cord-to-dura ratio was 0.31 ± 0.044 (range, 0.20 to 0.41) for noncompressive sites and 0.44 ± 0.078 (0.29 to 0.60) for sites of maximum compression. Sites of maximum compression were intervertebral and extra-dural, most frequently at C6 through 7 (n = 10), followed by C3 through 4 (6). Thirteen horses had dorsolateral and lateral compression at the AP joints, secondary to AP (n = 7) or soft tissue proliferation (6). Site significantly affected direction of compression, and directions of compression from occiput through C4 were primarily ventral and lateral, whereas from C6 through T1 were primarily dorsal and dorsolateral. No linear relationship was identified between mean or maximum APBR and spinal cord-to-dura ratio. CONCLUSIONS AND CLINICAL RELEVANCE: CT myelography may be useful for examination of horses with suspected cervical compressive myelopathy. Degree of compression can be assessed quantitatively, and site of compression significantly affected direction of compression.

Computed tomographic and angiographic assessment of spinal extradural arteriovenous fistulas in a dog.

A 6-month-old German shepherd dog was presented for progressive paraparesis. Multiple arteriovenous fistulae and hyperostosis of the thoracic vertebrae with secondary thoraco-lumbar spinal cord compression were diagnosed. Arteriovenous spinal fistula is a rare condition but should be considered as a differential diagnosis in young dogs with progressive paraparesis.

Évaluation par tomodensitométrie et angiographie de fistules artérioveineuses extradurales spinales chez un chien. Un chien Berger allemand âgé de 6 mois a été présenté pour une paraparésie progressive. De nombreuses fistules artérioveineuses et de l'hyperostose des vertèbres thoraciques avec une compression de la colonne vertébrale thoraco-lombaire secondaire ont été diagnostiquées. Les fistules spinales artérioveineuses sont une rare affection mais elles devraient être considérées comme un diagnostic différentiel chez les jeunes chiens atteints de paraparésie progressive.(Traduit par Isabelle Vallières).

Assessment of Intramedullary Spinal Pressure in Small Breed Dogs With Thoracolumbar Disk Extrusion Undergoing Hemilaminectomy.

OBJECTIVE: To assess intramedullary spinal pressure (IMP) in small breed dogs with thoracolumbar disk extrusion. STUDY DESIGN: Prospective cohort study. ANIMALS: Small breed dogs (n = 14) with thoracolumbar disk extrusion undergoing hemilaminectomy and healthy chondrodystrophic laboratory dogs (control; n = 3) without spinal disease. METHODS: Diagnosis was based on clinical and neurological examinations and magnetic resonance imaging (MRI) and was confirmed intraoperatively. A standardized anesthesia protocol and surgical procedure were used to minimize factors that could influence IMP. Intramedullary pressure was measured through a minidurotomy at the site of spinal cord compression using a fiber optic catheter inserted perpendicular to the longitudinal axis of the spinal cord. Measurements were taken after hemilaminectomy and again after removal of extruded disk material. RESULTS: Affected dogs had significantly higher IMP compared to control dogs (P = .008) and IMP decreased significantly post-decompression compared with initial values (P < .001). No correlation was found between IMP and neurologic grade, degree of spinal cord compression on MRI, or signal intensity changes on MRI. CONCLUSION: Acute thoracolumbar disk extrusion is associated with increased IMP in small breed dogs and surgical decompression results in an immediate decrease of IMP.

Assessment of Intrathecal Pressure in Chondrodystrophic Dogs With Acute Thoracolumbar Disk Disease.

OBJECTIVES: To assess intrathecal pressure (ITP) in chondrodystrophic dogs with thoracolumbar disk extrusion. STUDY DESIGN: Prospective cohort study. ANIMALS: Group 1: 11 chondrodystrophic dogs with thoracolumbar disk extrusion and present deep pain sensation. Group 2 (control): 3 healthy chondrodystrophic laboratory dogs without spinal disease. METHODS: Diagnosis was based on neurologic signs, magnetic resonance imaging (MRI) findings, and surgical confirmation. Blood pressure was maintained within physiologic range during anesthesia. A standardized surgical procedure was applied to minimize factors that could influence measurement readings. An extended hemilaminectomy was performed and ITP was measured with a fiber optic catheter. The catheter was inserted in the subarachnoid space 1 spinal segment caudal to the level of herniation and its tip was advanced to the site of compression. RESULTS: Significantly higher ITP occurred in chondrodystrophic dogs with acute thoracolumbar disk disease compared with controls. ITP was not associated with duration of clinical signs, neurologic status, outcome, degree of spinal cord compression, or signal intensity changes as assessed by MRI. CONCLUSION: Acute thoracolumbar disk disease leads to elevated ITP in chondrodystrophic dogs, which may contribute to increased compression of spinal cord parenchyma.

Partial lateral corpectomy of the thoracolumbar spine in 51 dogs: assessment of slot morphometry and spinal cord decompression.

OBJECTIVE: To report slot morphometry, degree of spinal decompression, and factors influencing decompression after partial lateral corpectomy (PLC) of the thoracolumbar spine in dogs with intervertebral disc disease. STUDY DESIGN: Case series. ANIMALS: Dogs (n=51) with predominantly ventrally located spinal cord compression. METHODS: PLC (n=60) were performed. Spinal cord compression was determined by computed tomographic (CT) myelography (n=46), myelography (n=2) or magnetic resonance imaging (n=3). Postsurgical CT images were used to evaluate slot dimensions and orientation, and spinal cord decompression. The influence of age, body weight, breed, breed type (chondrodystrophic, nonchondrodystrophic), disc location, lateralization and mineralization, presurgical compression, slot morphometry, and surgeon on degree of decompression were evaluated. RESULTS: Mean slot depth was 64.1% of vertebral body width; mean height, 43.0% of vertebral body height; mean cranial extension, 29.5%; median caudal extension, 22.0% vertebral body length; mean angulation from horizontal, 6.3°. Decompression was satisfactory in 90% of sites after PLC (58% complete, 32% good). None of the analyzed factors significantly influenced decompression. All lumbar spine PLC resulted in complete or good decompression compared with 83% after thoracic PLC (P=.052). Deeper slots tended to allow more complete decompression (P=.058). CONCLUSIONS: Thoracolumbar PLC results in satisfactory decompression in most cases with a better outcome in the lumbar spine than the thoracic spine. Achieving a slot depth equal to 2/3 of vertebral body width might facilitate complete decompression.

Assessment of the utility of using intra- and intervertebral minimum sagittal diameter ratios in the diagnosis of cervical vertebral malformation in horses.

Cervical vertebral malformation is one of the most common causes of ataxia in horses. The most important factor in the diagnosis of cervical vertebral malformation is the identification of cervical vertebral canal stenosis, but published data for minimum sagittal diameter ratios in adult horses are only available for C4-C7 intravertebral sites. Intra- and intervertebral sagittal diameter ratios at C2-C7 were evaluated in 26 ataxic horses, for which a complete clinical and neuropathological evaluation was undertaken. Eight of these horses were diagnosed with cervical vertebral malformation. In these horses the majority of compressive lesions were intervertebral. The mean sagittal diameter ratios of horses with cervical vertebral malformation were significantly smaller than those of horses without cervical vertebral malformation, and for an individual horse in our study, the site with the smallest intervertebral sagittal diameter ratio was always the site at which the spinal cord was compressed. Mean sagittal diameter ratio intravertebral site measurements of horses with cervical vertebral malformation were smaller than those of horses without cervical vertebral malformation; however, the site of compression could not be predicted from the data. For our dataset, horses with a sagittal diameter ratio of < or = 0.485 at any inter- or intravertebral site could be correctly classified as having cervical vertebral malformation, and sagittal diameter ratio measurements were an effective tool to identify at least one site of compression in an individual case.

A myelographic technique for avian species.

A post-mortem myelogram was used to diagnose a vertabral fracture in a Red-tailed Hawk (Buteo jamaicensis). This diagnosis led the authors to believe that myelography would be useful in live birds. In a pilot study using live adult female chickens (Gallus domesticus), mammalian myelographic techniques were modified for avian anatomic differences. A thoracolumbar puncture site was used rather than the lumbar or cisternal site which is commonly used in mammals. The volume of contrast medium needed to produce a diagnostic myelogram in birds (0.8-1.2 ml/kg) was found to be approximately four times that needed in mammals. A 25 gauge spinal needle was used rather than a 23 gauge needle. Myelograms of diagnostic quality were obtained with normal subject recovery. Seizures, the most common post-myelographic complication in mammals, were not observed in any of the birds studied. Avian myelography was found to be a cost effective and humane technique with potential application to avian practice.