T2-weighted Three-dimensional Fast Spin-echo MR in Inflammatory Peripheral Facial Nerve Palsy

Purpose: Our objective was to identify histologically and intraoperatively verified focal nerve thickening of the distal intrameatal segment on three-dimensional fast spin-echo (FSE) T2-weighted MR images as a new diagnostic criterion in patients with inflammatory peripheral facial nerve palsy.

Methods: Twenty-two patients with clinically diagnosed unilateral (n = 20) or bilateral (n = 2) inflammatory peripheral facial nerve palsy were examined on a 1.5-T MR imager using noncontrast and contrast-enhanced T1-weighted SE sequences and 3-D T2-weighted FSE sequences with secondary reformations. Abnormal contrast enhancement and possible focal nerve thickening of the distal intrameatal segment, labyrinthine nerve segment, and geniculate ganglion region were analyzed prospectively.

Results: In all patients, the T1-weighted postcontrast SE images showed characteristic smooth, linear, abnormally intense contrast enhancement of the distal intrameatal segment, indicating peripheral inflammatory nerve palsy. In 23 nerves (96%) a focal bulbous nerve thickening of the distal intrameatal segment was observed on 3-D T2-weighted FSE images. In 100% of patients with peripheral inflammatory facial nerve palsy, postcontrast T1-weighted SE images showed a smooth, linear, and abnormally intense contrast enhancement of the distal intrameatal segment; reformatted very thin 3-D T2-weighted FSE images showed a focal bulbous nerve thickening of the distal intrameatal segment in 96% of patients. These findings corresponded to intraoperative and histologic findings.

Conclusion: Three-dimensional T2-weighted FSE sequences are fast and cheap compared with T1-weighted postcontrast images, but secondary reformations are time-consuming and require exact anatomic knowledge for careful analysis of the different nerve segments.