An atypical spinal cord injury in a 7 month old Standardbred colt
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A 7 month old Standardbred colt presented to the Equine Farm Animal Hospital for a recheck of an angular limb deformity. Historically, the colt was treated for neonatal maladjustment syndrome and at 6 weeks of age for a mixed bacterial pneumonia (Streptococcus zooepidemicus, Actinobacillus spp., Rhodococcus equi.). The colt had some abnormal behaviors such as nursing from the mare while “dog-sitting” and incoordination which had been noted over the past few months. Upon presentation the weaned foal was bright, alert and responsive. He was noted to have several minor orthopedic problems (bilateral carpal valgus, moderate swelling of the left tarsus, external rotation in the right hind limb) however his gait was more consistent with a neurological condition. A neurological examination confirmed a mild tetraparesis and moderate ataxia on all four limbs (grade II of V) consistent with a C1-C5 myelopathy. The main rule outs at this time were a congenital abnormality including cervical vertebral malformation, trauma, equine protozoal myelitis, Rhodococcus equi infection of a cervical vertebra, and equine degenerative myelopathy. A complete blood count, chemistry panel with fibrinogen, serum amyloid A, Vitamin E and selenium levels were unremarkable. Cervical vertebral radiographs were normal. A CT scan with contrast revealed a small area of asymmetry (intraparenchymal lesion) of the spinal cord at the level of the first cervical section. Further diagnostic evaluation was recommended but euthanasia was elected due to the foal’s poor prognosis for future performance. Post-mortem MRI of the cranium confirmed the intraparenchymal lesion of the spinal cord at C1, and showed a questionable region of sclerosis of the right occipital condyle. Histopathology of the spinal cord revealed a large glial scar that corresponded to the region of the asymmetry noted on imaging. Based on the pattern and the presence of hemosiderin laden macrophages near this lesion, a healed infarct was prioritized as the most likely cause of the glial scar, which was likely 3-6 months old. This presentation will focus on the diagnostic evaluation of a weanling colt with cervical ataxia.