NEURITIS

inflammation of one or several nerves. The characteristic symptoms of neuritis include pain and tenderness; impaired sensation, strength, and reflexes; and abnormal circulation and sweating in the distribution of the inflamed nerve or nerves. A unique feature of the nerve fibre is its extraordinary length. In its course a nerve may lie next to skin or bone or it may pass through muscles or tunnels. All these anatomic vicissitudes represent hazards, and, indeed, neuritis frequently results from such mechanical injuries as adjacent tissues pressing on a nerve or blows delivered on a nerve running just underneath the skin. Nerve fibres are housed in connective tissue that may become infected, scarred, or invaded by tumours, events that may cause injury to nerve fibres. There are many causes of neuritis, but in general it may be said that when neuritis affects one nerve (mononeuritis) or a plexus of nerves (plexitis), the cause commonly is a mechanical one; that when several single nerves are affected simultaneously (mononeuritis multiplex), the cause often is a vascular or allergic one; and that when widely separated nerves are affected (polyneuritis), the cause often is toxic, metabolic, viral, or allergic. The symptoms of neuritis are usually confined to the specific portion of the body served by the inflamed nerve. Inflammations of sensory neurons in a nerve fibre cause sensations of tingling, prickling, burning, boring, or stabbing pains that are worse at night and are aggravated by touch or temperature change. The inflammation of the motor part of a nerve (i.e., those neurons that transmit impulses to muscles) causes symptoms ranging from muscle weakness to complete paralysis. Muscles in the area served by the affected nerve lose tone, become tender, and may atrophy. A notable form of mononeuritis is Bell's palsy, which is caused by the inflammation of a facial nerve and which causes a characteristic distortion of the facial muscles. The treatment of neuritis is directed toward the causative agent. Analgesics may be required for pain. Under proper therapy, recovery is usually rapid in less severe cases; repetition of the original cause may bring about recurrence. In severe cases, recovery may be incomplete, with some residual motor and sensory disturbances. See also neuralgia.