The Neurological Examination

The equine neurologic exam can be divided into 4 parts: Evaluation of mental status; Cranial nerve (CN) exam; Evaluation of posture, spinal reflexes and muscle while horse is standing; and Evaluation of gait, posture, and postural reflexes while horse is moving. At the onset examine the horse standing quietly in its stall looking at its posture, mental awareness and whether any odd behaviors are exhibited. Next is to approach the horse to evaluate its cranial nerves, looking for abnormalities or asymmetry between sides of the horse. Next is to watch the horse walk in straight line, trot horse in straight line, walk in circles, walk with head elevated, walk backwards and then walk the horse while pulling tail in each direction. I sometimes walk the horse in a serpentine, spin it in tight circles, walk on uneven ground and walk up and down hills. Pay attention to stride length, stride height, regularity of foot placement and whether the horse is dragging a toe. Horses with spinal cord disease affecting the upper motor neuron and general proprioceptive tracts show a long-stride length with a floating gait. Diseases that affect the lower motor neurons or neuromuscular system tend to cause a short choppy gait that sometimes mimics an orthopedic problem. Horses with ataxia tend to have irregularly irregular foot placement, while horses with orthopedic disease have regularly irregular foot placement. Proprioceptive deficits suggestive of neuro- logic disease are most easily seen when the horse is changing directions, circling tightly, or walk- ing up and down a hill with the head elevated. If evidence of ataxia is subtle or not observed, a more extensive lameness examination is indicated, which could include trotting in circles, flexion tests, and working on the lounge or under saddle. When an abnormal gait is recognized but its origin is not clear, the next step is again often diagnostic local or regional analgesia to see if the abnormal gait will ‘block out’, in which case musculoskeletal disease is assumed. If the abnormal gait is not considered ‘blockable,’ involves multiple limbs, or there are other reasons not to perform diagnostic analgesia, a systemic analgesia trial with phenylbutazone or similar non-steroidal anti-inflammatory drug might yield useful information. Repeated neurologic and lameness examinations are important, particularly after analgesia trials. Some of the most confusing cases are those with neuromuscular disease, or those that have both neurologic and orthopedic problems. […]