Limitations of magnetic resonance imaging in the evaluation of perineural tumor spread causing facial nerve paralysis.

OBJECTIVE To present and discuss the clinical presentation and treatment in patients with long-duration unilateral facial paralysis and normal magnetic resonance imaging (MRI) findings. DESIGN Case series. SETTING Ear, nose, and throat department of the University of Cologne, Cologne, Germany. PATIENTS A total of 486 patients with unilateral facial paralysis who were treated from 1986 to 1998. Besides the usual diagnostic workup, a complete electrophysiological evaluation, including investigations such as needle electromyography and neuromyography (also known as electroneurography), of the facial nerve was performed at repeated intervals. In 19 patients, a malignant tumor was delineated with ultrasonography or MRI. In 8 of these patients, the initially performed MRI did not detect any parotid gland lesion causing the paralysis, whereas long duration of the paralysis and electroneurography indicated malignancy. RESULTS Exploration surgery was performed as total parotidectomy in these 8 patients and malignant parotid gland tumors were proved in all 8 patients. CONCLUSIONS Individuals with facial nerve paralysis without any signs of regeneration 6 months after the onset of paralysis and/or persistent electrophysiological evidence of ongoing neuronal degeneration should undergo surgical exploration of the parotid gland and facial nerve, even if MRI studies show no tumoral lesion.