NERVE INJURIES Nerves when divided as the result of injury usually unite readily, even when a gap exists between the two ends. In some cases, how ever, inflammatory changes take place in the divided end nearest to the nerve centre with the production of fibrous tissue, particularly in the nerve sheath. Cicatricial contraction then occurs, with the result that pain is mani fested, and should the"neuroma,"as the enlargement is called, be present in one of the limbs, lameness will result.
"Neuroma"is a frequent sequel to neurec tomy, whilst we have observed neuroma forma tion follow section of one of the branches of the musculo-cutaneous division of the median nerve occurring in connection with an extensive wound of the forearm. This was accompanied by marked lameness.
As a rule a neuroma"can be felt through the skin, and its manipulation is attended by evidence of great pain on the part of the animal.
The"neuroma"may be removed surgically after local injection of cocaine solution, or the nerve may be divided just above the enlarge ment.
Neuroma formation following neurectomy is facilitated by suppuration in the wound and by exercise before healing is complete. If the animal be kept in a stall for ten days following operation the condition will be very rarely met with. Care should also be taken when operat ing that the nerve is divided as high up as possible, so that the end may retract and not become implicated in the process of healing. Neuroses. As a result of nervous disorders, we may meet with, among horses, cases of hyper sthesia, anaesthesia, and perverted sensibility. Hypemsthesia is occasionally met with in various parts of the body, but is commonest in the region of the mane, particularly beneath the collar, although it is apparently in no way due to injury. The animal cannot bear the least touch on the affected area. Anaesthesia is more rare, and is usually associated with paralysis of muscles, though local anaesthesia may exist independent of any other disorder.
Perverted sensibility applies to the condition of non - parasitic"itchiness"without any visible cause. Some horses with clean skin and
quite free from any cutaneous lesion will show signs of appreciation whcn the withers are scratched, and may even lean on the attendant or go to ground, as a result of nervous excite ment.
Treatment. Hyperwsthesia of the neck is palliated by the application of astringents and by sedatives, as cocaine or belladonna ointment.
Its cure is, however, only effected by shaving the part and then completely removing the outer layer of the skin by means of the razor and subsequently treating with antiseptic astringents.
may be overcome by massage, electricity, counter- irritation, and the adminis tration of strychnine.
Non-parasitic itchiness is relieved by washing with strong salt solution or with weak vinegar and carbolic acid. Sometimes an alkaline mixture containing a small percentage of hydro cyanic acid gives relief.
Arsenic may be administered internally and a dose of physic is advisable. Certain food stuffs may produce skin irritation, and excess of nitrogenous food must be avoided.
Neuritis.Unfortunately we are not in a position to study neuritis in the lower animals so carefully as can the surgeon who attends a human being capable of explaining his or her symptoms; nevertheless we occasionally meet with cases of lameness to which by a process of exclusion we are forced to diagnose neuritis.
Changes in the sciatic nerve in the horse have been recorded by several observers. Possibly certain cases of obscure lameness may be attri butable to the condition affecting one or other of the nerve-trunks. Persistent shaking of the head shown by some horses in harness or saddle has been attributed to neuritis of the superior maxillary nerve at or just within the foramen by which it becomes superficial. In some in stances the nerve has been found enlarged or thickened, and its section has been followed by disappearance of the peculiar nodding or shaking of the head. R. H. S.