Magnetic resonance imaging of the facial nerve.

Magnetic resonance imaging (MRI) of the facial nerve was evaluated by studying normal volunteers and patients with diseases of the facial nerve with a 0.3 Tesla permanent-magnet MRI system with special surface coils. The normal MR images were correlated with the anatomy of thin cryosection specimens of fresh cadavers. The seventh nerve was followed from its nucleus in the brainstem through the temporal bone to the parotid gland bed. The entire labyrinth and tympanic portions, as well as the geniculate ganglion, could be shown with appropriate scan planes. Examples of brainstem diseases affecting the facial nerve and nucleus, facial neuromas, parotid tumors involving the facial nerve, and other diseases were studied. MRI is a technique that allows unique evaluation of the entire course of the facial nerve. It produces superior images of the facial nerve with high-contrast resolution. Unlike computed tomography, there is no beam-hardening artifact from the temporal bone or exposure to ionizing radiation and contrast agents. MRI also allows visualization of the main trunks of the facial nerve in the parotid bed not possible with any other imaging technique.