Intratemporal and Extratemporal Facial Nerve Schwannoma:CT and MRI Findings

Kim, Keum Won; Lee, Ho Kyu; Shin, Ji Hoon; Choi, Choong Gon; Suh, Dae Chul; Cheong, Hae Kwan

Abstract

PURPOSE: To analyze the characteristics of CT and MRI findings of facial nerve schwannoma in ten patients.
MATERIALS AND METHODS
Ten patients with pathologically confirmed facial nerve schwannoma, underwent physical and radiologic examination. The latter involved MRI in all ten and CT scanning in six. We analyzed the location (epicenter), extent and number of involved segments of tumors, tumor morphology, and changes in adjacent bony structures.
RESULTS
The major symptoms of facial nerve schwannoma were facial nerve paralysis in seven cases and hearing loss in six. Epicenters were detected at the intraparotid portion in five cases, the intracanalicular portion in two, the cisternal portion in one, and the intratemporal portion in two. The segment most frequently involved was the mastoid (n=6), followed by the parotid (n=5), intracanalicular (n=4), cisternal (n=2), the labyrinthine/geniculate ganglion (n=2) and the tympanic segment (n=1). Tumors affected two segments of the facial nerve in eight cases, only one segment in one, and four continuous segments in one. Morphologically, tumors were ice-cream cone shaped in the cisternal segment tumor (1/1), cone shaped in intracanalicular tumors (2/2), oval shaped in geniculate ganglion tumors (1/1), club shaped in intraparotid tumors (5/5) and bead shaped in the diffuse-type tumor (1/1). Changes in adjacent bony structures involved widening of the stylomastoid foramen in intraparotid tumors (5/5), widening of the internal auditary canal in intracanalicular and cisternal tumors (3/3), bony erosion of the geniculate fossa in geniculate ganglion tumors (2/2), and widening of the facial nerve canal in intratemporal and intraparotid tumors (6/6).
CONCLUSION
The characteristic location, shape and change in adjacent bony structures revealed by facial schwannomas on CT and MR examination lead to correct diagnosis.