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 i n patients with long-duration unilateral facial paralysis and normal magnet ic resonance imaging (MRI) findings. Design: Case series. Setting: Ear, nose, and throat department of the University of Cologne, Col ogne, Germany. Patients: A total of 486 patients with unilateral facial. paralysis who wer e treated from 1986 to 1998. Besides the usual diagnostic workup, a complet e electrophysiological evaluation, including investigations such as needle electromyography and neuromyography (also known as electromyography), of th e facial nerve was performed at repeated intervals. In 19 patients, a malig nant tumor was delineated with ultrasonography or MRI. In 8 of these patien ts, the initially performed MRI did not detect any parotid gland lesion cau sing the paralysis, whereas long duration of the paralysis and electroneuro graphy indicated malignancy. Results: Exploration surgery was performed as total parotidectomy in these 8 patients and malignant parotid. gland tumors were proved in all 8 patient s. Conclusions: Individuals with facial nerve paralysis without any signs of r egeneration 6 months after the onset of paralysis and/or persistent electro physiological. evidence of ongoing neuronal degeneration should undergo sur gical exploration of the parotid gland and facial nerve, even if MRI studie s show no tumoral lesion.