ABSTRACT
Bell’s palsy is a lower motor-neurone paralysis of the facial nerve of unknown cause.
The nature of Bell’s palsy is not well understood. There appears to be inflammation and swelling of the facial nerve within its bony canal. The site of the swelling is variable and dictates the symptoms (in particular whether there is failure of tear production in the eye on the involved side, whether there are abnormalities of taste sensation, and whether there is intolerance of loud sounds on the affected side because of paralysis of the stapedius muscle). The most usual lesion is a neuropraxia at the level of the swelling due to compression of nerve fibres. Axonotmesis may also occur in more severe cases with degeneration of the nerve. Since there is no interruption of continuity of the nerve as a whole, neurotmesis cannot occur.
