Peripheral nerve involvement in acute Bell's palsy.

Motor nerve conduction studies were carried out on the ipsilateral and contralateral ulnar nerves (arm and forearm segments) in 20 patients presenting with unilateral acute Bell's palsy. In seven of these cases (35%), there was motor conduction delay in one or more segments of the ulnar nerve. The present study confirms the hypothesis that Bell's palsy has a viral or autoimmune aetiology resulting in a generalized polyneuropathy or mononeuritis multiplex. Paralysis is clinically more manifest in the facial nerve than other motor nerves; this is because of the peculiar anatomical course of the facial nerve inside a bony canal.