Background and purpose: Electromyography (EMG) is an important diagnostic toll in the study of Thoroughbred foals, and other horses with neurologic disorders. This case study was designed to follow, in a serial manner, a Thoroughbred foal with an isolated peripheral lesion of the axillary nerve. Subject: A Thoroughbred foal with a suspected lesion of the axillary nerve. Methods: Serial electromyographic analysis was performed on a monthly basis for six months. Electromyographic findings were correlated with the phyisical exam and functional progress of the subject. Results: Electromyographic testing revealed a severe isolated lesion of the left axillary nerve. Serial testing revealed a slow neural regeneration process. The return of muscle girth is less likely in muscles with severe atrophy, and little EMG evidence of neural regeneration, three months post injury. In this case, a foal with severe isolated unilateral loss of the deltoid muscle showed little electrophysiologic, or muscle girth improvement, but returned to full function. Conclusions and Discussion: Electromyography is of great benefit in the differential diagnosis of peripheral nerve injuries in horses. By isolating the location and severity of a nerve lesion, the EMG data can be valuable in developing a prognosis for neurologic improvement. Additional EMG research may be clinicians develop patterns of functional return in horses with specific peripheral nerve lesions.
