Paralysis of the Suprascapular Nerve.

Anatomy.—­The suprascapular (anterior scapular) nerve, a small branch of the brachial plexus, is given off from the anterior portion of this plexus.  The nerve rounds the anterior border of the neck of the scapula, passing upward and backward under the supraspinatus (antea-spinatus) muscle and terminating in the infraspinatus (postea-spinatus) muscle.

Etiology and Occurrence.—­As the result of direct injury to this nerve by contusion such as may be received in runaway accidents, collar bruises, especially collar bruises in young horses that are not accustomed to pulling and that walk in a manner to cause side draft, injury to the nerve occurs, and partial or complete paralysis supervenes.  Some writers state that it may be produced by confining an animal in recumbency, with the casting harness.  The common cause of paralysis or paresis of this nerve in cases such as one observes in country practice, is bruises from the collar in colts that are put to heavy farm work or where ill fitting collars are used.

Symptomatology.—­With partial or complete suspension of function of the suprascapular nerve there results enervation of the supraspinatus and infraspinatus muscles.  Since these muscles act as external lateral ligaments of the scapulohumeral joint, when they are incapacitated, there naturally follows more or less abduction of the shoulder when weight is borne.

In extreme cases, as soon as the ailing animal is caused to support weight with the affected member, the joint is suddenly thrown outward in a manner that the average layman at once concludes that there must be scapulohumeral luxation, and the veterinarian receives a call to see a case wherein the “shoulder is out of place.”  There exists, however, no luxation in such cases.

If serious injury is done the nerve so that it undergoes degenerative changes, there will result atrophy of the muscles that derive their nerve supply from the suprascapular nerve.

[Illustration:  Fig. 7—­Paralysis of the suprascapular nerve of the left shoulder]

Treatment.—­During the first few days following injuries which result in this form of paralysis, it is well to keep the subject inactive, and if much inflammation of the injured structures contiguous to the nerve exists, the application of cold packs is beneficial.  Later, as soon as acute inflammation has subsided, vesication of a liberal area around the anteroexternal part of the scapulohumeral joint and over the course of the suprascapular nerve, will stimulate recovery in favorable cases.  As a rule, in mild cases, the subject is in a condition to return to work in two or three weeks.

Radial Paralysis.

Described under the titles of “Radial Paralysis” and “Brachial Paralysis,” there is to be found in veterinary literature a discussion of conditions which vary in character from the almost insignificant form of paresis to the incurably affected conditions wherein the whole shoulder is completely paralyzed.