Contrast-enhanced MR imaging of the facial nerve in 11 patients with Bell's palsy.

Contrast-enhanced MR images (at 1.5 T) were obtained in 11 patients with facial palsy. The group included five people with acute idiopathic facial (Bell's) palsy, three with chronic idiopathic facial palsy, and one each with acute facial palsy after local radiation therapy, acute facial palsy resulting from herpes zoster virus infection, and facial palsy caused by facial neuroma. Eight of the 11 patients demonstrated marked enhancement of the affected facial nerve from the labyrinthine portion through the descending canal. Three patients also demonstrated mild enhancement of the distal canalicular portion of the facial nerve, simulating small distal acoustic neuromas. No difference in the pattern of enhancement between the acute or chronic Bell's palsy patients was seen. Radiographic resolution appeared to lag behind clinical resolution. The facial neuroma appeared distinct from the other lesions as a focally enhancing mass. The enhancement pattern in the Bell's group correlated with the histopathologic features of Bell's palsy and is consistent with the viral hypothesis of the syndrome. Thin-section contrast-enhanced MR scans are recommended for individuals with atypical presentation of facial paralysis. In the proper clinical setting, contrast-enhanced MR imaging may permit a positive radiographic diagnosis of Bell's palsy, which has previously been a diagnosis of exclusion.