Disease of a single peripheral or cranial nerve is called a mononeuropathy. It may be associated with systemic illnesses such as diabetes mellitus, sarcoidosis, rheumatoid arthritis or polyarteritis nodosa. The most common cause worldwide is leprosy.
An entrapment neuropathy occurs when a peripheral nerve is damaged by passage through a tight space. It is often precipitated by swelling of the soft tissue as in acromegaly, myxoedema, and pregnancy; for example, entrapment of the median nerve in carpal tunnel syndrome. Occasionally, such conditions show a familial tendency.
A compression neuropathy occurs when sustained pressure is applied to a peripheral nerve which lies between skin and bone, relatively unprotected by soft tissue; for example, "saturday night palsy" due to compression of the radial nerve against the humerus.