2.0 Case History
A two-year-old Standardbred cryptorchid colt was presented to the Ambulatory Equine Service at the Atlantic Veterinary College for evaluation of a reported lameness of five days duration. The colt was actively in training and the owner indicated that the colt had begun to increasingly stumble in the stall over the past 5 days leading him to believe a lameness was present and request radiographs of a swollen tarsus. The horse had been examined nine days prior to presentation for a case of cellulitis in the left forelimb that resulted from a superficial wound and no neurologic deficits were observed during that examination. On presentation, the colt was bright, alert and responsive. He stood with a base wide stance in the forelimbs and on physical examination, the left tibiotarsal joint was moderately swollen and the left hind digital flexor tendon sheath was moderately distended. When observed at the walk he was noted to have grade 3.5/5 ataxia based on a modified Mayhew grading system for cervical spinal cord disorders with the hindlimbs more severely affected than the forelimbs (Whitlock RH 1998, de Lahunta and Glass 2009). The colt exhibited weakness when the tail was pulled to both sides and he circumducted both hindlimbs when walked in a circle. He exhibited severe proprioceptive deficits and dragged both hind hooves at a walk. After approximately 10 minutes of walking, he almost fell to the ground several times and was deemed unsafe to continue to proceed with the neurologic examination. Owners declined further investigation based on the acute onset and severity of ataxia and elected humane euthanasia. An intravenous catheter was placed in the right jugular vein. Due to the severity of the ataxia, the colt was not premedicated with sedation and was humanely euthanized with intravenous sodium pentobarbital (Euthansol, Merck Animal Health Intervet Canada Corp., Kirkland, Quebec, Canada), 110 mg/kg BW and submitted for necropsy.