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.