Enhancement along the facial nerve on MRI.

Enhancement along the facial nerve on magnetic resonance imaging (MRI) with intravenous contrast (gadolinium) is not only common, it is normal. In most cases, enhancement is asymmetric. The distribution of the enhancement corresponds anatomically to the extrinsic perineural vascular plexus of the facial nerve rather than to a breakdown of the blood-nerve barrier. This enhancement is more prominent in the region of the geniculate ganglion. [1]

Even though facial nerve enhancement is common, the physician should consider that an inflammatory process might be present when the enhancement of the affected side is marked and diffuse and involves the intracanalicular and labyrinthine segments, as well as the geniculate ganglion, as occurred in the case presented here. In some cases, the tympanic and mastoid portions of the facial nerve are also enhanced. In our case, a 29-year-old woman with facial paralysis (Bell's palsy) on the left exhibited a marked enhancement of the left facial nerve (figure). It should be mentioned, however, that the most important reason for performing an MRI in a patient with Bell's palsy is to rule out other causes of facial paralysis, including cholesteatoma and other tumors.

From the Department of Radiology, Louisiana State University Health Science Center, New Orleans (Dr. Palacios), and the Department of Radiology and Otolaryngology, University of Illinois Medical Center, Chicago (Dr. Valvassori).

Reference

(1.) Gebarski SS, Telian SA, Niparko JK. Enhancement along the normal facial nerve in the facial canal: MR imaging and anatomic correlation. Radiology 1992;183:391-4.