Mononeuritis: Inflammation of a single nerve. There are many causes of mononeuritis including diabetes mellitus, carpal tunnel syndrome, rheumatoid arthritis, and Lyme disease. The treatment of mononeuritis depends on the underlying cause.
Whereas mononeuritis involves only a single nerve, mononeuritis multiplex involves inflammation of two or more nerves, typically in unrelated portions of the body, causing a loss of function of the muscle tissue that is innervated by the affected nerve. For example, sudden loss of ability to normally lift the foot up while walking (foot drop) can be caused by mononeuritis multiplex when accompanied by loss of nerve function elsewhere in the body.