Subclinical entrapment neuropathy of the equine suprascapular nerve.

The suprascapular nerve from 14 horses, which had no clinical evidence of spinatus muscle atrophy, were obtained to determine whether the nerve was sub-clinically compressed at the scapular edge. The nerves were divided into three portions, proximal and distal to the scapular edge and as it reflected around it. In nine horses there was evidence of a chronic neuropathy which varied in severity and which was most severe at the site of reflection, where the nerve appeared constricted by a tendinous band. At this site the predominant change was that of chronic demyelination and remyelination, with many scattered thinly myelinated fibres and occasionally profuse onion bulb formation. There were also occasional regenerating clusters, which were the only abnormalities seen in the distal nerve. Renaut bodies appeared to be more common and larger in nerves with chronic focal neuropathy. Teased fibres confirmed the chronic myelin sheath changes, and the presence of many paranodal swellings suggested a possible chronic compressive aetiology. This is the first reported spontaneous entrapment neuropathy in the domestic animals.