MR imaging in Bell's palsy and herpes zoster opticus: correlation with clinical findings

To evaluate the MRI findings of acute facial nerve paralysis in Bell's palsy and herpes zoster opticus, and to correlate these with the clinical findings. We retrowspectively reviewed the MRI findings in six cases of BEll's palsy(BP) and two of herpes zoster oticus(HZO), and compared them with the findings for 30 normal facial nerves. This nerve was considered abnormal when its signal intensity was greater than that of brain parenchyma or the contralateral normal side on Gd-enhanced T1-weighted axial and coronal MR images. We analysed the location and degree of contrast enhancement, interval change, and clinical progression in correlation with House-Brackmann(HB) grade and electroneuronography (ENoG) findings. Fifteen of 30 normal facial 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) or labyrinthine segment of the facial nerve was noted, however. In BP and HZO, Gd-enhanced MR images revealed fair to marked enhancement for more than two segments from the internal auditory canal to the mastoid segment of the facial 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. No correlation between clinical HB grade, ENoG, and follow up MRI findings was noted. Except in the internal auditory canal and labyrinthine segment, normal facial nevemay show mild and relatively symmetrical enhancement. In BP and HZO, the facial nerve showed diffuse enhancement from the IAC to the mastoid segment.=20