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

ABSTRACT

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.