Facial nerve biopsy for etiologic clarification of Bell's palsy.

Electron microscopic findings of biopsy specimens of the intratemporal facial nerve from four selected patients with Bell's palsy are described, and the results of clinical examinations and surgical findings are presented. In all specimens, wallerian degeneration of various degrees was demonstrated. In one specimen, extravascular erythrocytes, and in another, lymphatic infiltrations were noted. On the basis of the present investigation and reported temporal bone histopathologic evidence, the causes of Bell's palsy are concluded to be multiple and to be vascular, inflammatory, or degenerative.