NEURITIS (Gr. νεῦρον, nerve), a term applied to the inflammation of one or more bundles of nerve fibres. Two varieties are known, the localized and the multiple. The localized form frequently follows on exposure to cold and may attack a single nerve. Facial paralysis (Bell's palsy) is commonly seen following a neuritis of the facial nerve. Neuritis may follow blows and wounds of a nerve, injuries involving stretching of a nerve or long continued pressure such as may occur in a dislocation of the elbow joint, or the nerve may share in the extension of a neighbouring inflammation. The first symptom of a localized neuritis is pain of a boring character along the course of a nerve and its distribution, the part being sensitive to pressure. There may be slight redness and oedema along the course of the nerve, movement becomes painful in the muscles to which the nerve is distributed, numbness may follow and the tactile sense be impaired, finally the muscles atrophy, and degenerative changes may take place in the nerve or nerve sheath. Slight cases following cold or injury may pass off in a few days, while severe cases such as those following the pressure of an unreduced dislocation may last for months.
Multiple neuritis or polyneuritis is a disease which may affect many of the peripheral nerves symmetrically and at the same time. For the pathological changes see Neuropathology. Th e difference in these changes is due mostly to the difference in the aetiology of the neuritis. The causes may be divided as follows: (1) The toxins of acute infective diseases, such as diphtheria, influenza, typhoid fever, malaria, scarlet fever and septicaemia. (2) Acute or chronic poisoning by lead, arsenic, mercury, copper and phosphorus. (3) General disorders: gout, rheumatism, tubercle, carcinoma. (4) The local action of leprosy and syphilis. (5) Endemic disease: beri-beri. (6). Alcohol, the most common.