Intratemporal and Extratemporal Facial Nerve Schwannoma:CT and MRI Findings

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.

MR Findings of Facial Nerve on Oblique Sagittal MRI Using TMJ Surface Coil: Normal vs Peripheral Facial Nerve Palsy

PURPOSE: To evaluate the findings of normal facial nerve, as seen on oblique sagittal MRI using a TMJ (tem-poromandibular joint) surface coil, and then to evaluate abnormal findings of peripheral facial nerve palsy. MATERIALS AND METHODS: We retrospectively reviewed the MR findings of 20 patients with peripheral facial palsy and 50 normal facial nerves of 36 patients without facial palsy. All underwent oblique sagittal MRI using a TMJ surface coil. We analyzed the course, signal intensity, thickness, location, and degree of enhancement of the facial nerve. According to the angle made by the proximal parotid segment on the axis of the mastoid seg-ment, course was classified as anterior angulation (obtuse and acute, or buckling), straight and posterior angu-lation. RESULTS: Among 50 normal facial nerves, 24 (48%) were straight, and 23 (46%) demonstrated anterior angula-tion; 34 (68%) showed iso signal intensity on T1WI. In the group of patients, course on the affected side was either straight (40%) or showed anterior angulation (55%), and signal intensity in 80% of cases was isointense. These findings were similar to those in the normal group, but in patients with post-traumatic or post-operative facial palsy, buckling, of course, appeared. In 12 of 18 facial palsy cases (66.6%) in which contrast materials were administered, a normal facial nerve of the opposite facial canal showed mild enhancement on more than one segment, but on the affected side the facial nerve showed diffuse enhancement in all 14 patients with acute facial palsy. Eleven of these (79%) showed fair or marked enhancement on more than one segment, and in 12 (86%), mild enhancement of the proximal parotid segment was noted. Four of six chronic facial palsy cases (66.6%) showed atrophy of the facial nerve. CONCLUSION: When oblique sagittal MR images are obtained using a TMJ surface coil, enhancement of the proximal parotid segment of the facial nerve and fair or marked enhancement of at least one segment within the facial canal always suggests pathology of the facial nerve. The use of this modality, together with the coil, is, therefore, an effective complementary technique for the evaluation of a facial nerve.

MR Imaging in Bell's Palsy and Herpes Zoster Oticus: Correlation with Clinical Findings

PURPOSE: To evaluate the MRI findings of acute facial nerve paralysis in Bell's palsy and herpes zosteroticus, and to correlate these with the clinical findings. MATERIALS AND METHODS: We retrospectively reviewed theMRI findings in six cases of Bell's palsy(BP) and two of herpes zoster oticus(HZO), and compared them with thefindings for 30 normal facial nerves. This nerve was considered abnormal when its signal intensity was greaterthan that of brain parenchyma or the contralateral normal side on Gd-enhanced T1-weighted axial and coronal MRimages. We analysed the location and degree of contrast enhancement, interval change, and clinical progression incorrelation with House-Brackmann(HB) grade and electroneuronography(ENoG) findings. RESULTS: Fifteen of 30 normalfacial nerves(50%) seen on Gd-enhanced MRI were mildly enhanced in the geniculate ganglion, the proximal tympanic,and the proximal mastoid segment of the facial nerve. No enhancement of the internal auditory canal(IAC) orlabyrinthine segment of the facial nerve was noted, however. In BP and HZO, Gd-enhanced MR images revealed fair tomarked enhancement for more than two segments from the internal auditory canal to the mastoid segment of thefacial nerve. During follow-up MRI, enhancement of the facial nerve varied in location and signal intensity,though gradually decreased in intensity approximately eight weeks after the onset of facial nerve palsy. Nocorrelation between clinical HB grade, ENoG, and follow up MRI findings was noted. CONCLUSION: Except in theinternal auditory canal and labyrinthine segment, normal facial neve may show mild and relatively symmetricalenhancement. In BP and HZO, the facial nerve showed diffuse enhancement from the IAC to the mastoid segment.

Three-Dimensional Short-Range MR Angiography and Multiplanar Reconstruction Images in the Evaluation of Neurovascular Compression in Hemifacial Spasm

PURPOSE: To evaluate the diagnostic efficacy of three-dimensional(3D) short-range MR angiography(MRA) andmultiplanar reconstruction(MPR) imaging in hemifacial spasm(HS). MATERIALS AND METHODS: Two hundreds patientswith HS were studied using a 1.5T MRI system with a 3D time-of-flight(TOF) MRA sequence. To reconstructshort-range MRA, 6-10 source images near the 7-8th cranial nerve complex were processed using a maximum-intensityprojection technique. In addition, an MPR technique was used to investigate neurovascular compression. We observedthe relationship between the root-exit zone(REZ) of the 7th cranial nerve and compressive vessel, and identifiedthe compressive vessels on symptomatic sides. To investigate neurovascular contact, asymptomatic contralateralsides were also evaluated. RESULTS: MRI showed that in 197 of 200 patients there was vascular compression orcontact with the facial nerve REZ on symptomatic sides. One of the three remaining patients was suffering fromacoustic neurinoma on the symptomatic side, while in two patients there were no definite abnormal findings. Compressive vessels were demonstrated in all 197 patients; 80 cases involved the anterior inferior cerebellarartery(AICA), 74 the posterior cerebellar artery(PICA), 13 the vertebral artery(VA), 16 the VA and AICA, eight theVA and PICA, and six the AICA and PICA. In all 197 patients, compressive vessels were reconstructed on one 3Dshort-range MRA image without discontinuation from vertebral or basilar arteries. 3D MPR studies providedadditional information such as the direction of compression and course of the compressive vessel. In 31 patientsthere was neurovascular contact on the contralateral side at the 7-8th cranial nerve complex. CONCLUSION: Inpatients with HS, 3D short-range MRA and MPR images are excellent and very helpful for the investigation ofneurovascular compression and the identification of compressive vessels.