Magnetic resonance imaging, electroneurographic, and clinical findings in Bell's palsy

Sammanfattning: Seventy-two patients were examined in order to learn more about the pathophysiology of Bell's palsy and to assess the value of magnetic resonance imaging (MRI) as well as electroneurographic and clinical tests in predicting the outcome in patients with this disease.In 12 of 20 patients (60%) an increased signal intensity in the paranasal sinuses was evident on T2-weighted MRI scans in the early stage of palsy, and in six of the positive patients the high signal intensity had disappeared by the time of the follow-up examination. Gadolinium-enhanced MRI (GdMRI) of the facial nerve demonstrated transient enhancement, mainly in the meat&internal auditory canal segment, on the ipsilateral side in 17 of 32 patients with Bell's palsy. In 11 of the 32 patients the disappearance of facial nerve enhancement was found to be related to clinical and electroneurographic (ENoG) improvements in facial nerve function during recovery from Bell's palsy. GdMRI in the early stage of palsy did not add any prognostic information regarding recovery.Thirty patients were serially examined (mean days 11, 36 and 99) with ENoG, and the results were compared with the Yanagihara and House-Brackmann clinical gradings. Initial ENoG testing was superior in predicting the outcome of palsy. The pattern in the two clinical systems during recovery from palsy strongly resembled each other. For the mild palsies, values obtained in the initial ENoG were relatively lower compared with the initial clinical gradings. Severe palsies improved clinically even in patients who continued to show a high degree of degeneration according to ENoG.Patterns of change in serially recorded ENoG (n=30) values in the frontalis, orbicularis oculi, nasalis and mentalis muscles during recovery were similar for the four regions. The correlation between the facial muscle ENoG recordings was initially poor but it was better in follow-up examinations. The difference between patients with a favorable and unfavorable outcome increased when the average ENoG values were calculated from more than one muscle. The MRI findings indicated that an inflammatory/edematous lesion was present in the meatal region of the facial nerve in Bell's palsy, which in some cases was related to inflammatory paranasal sinus disease. The discrepancy between ENoG and clinical results was related mainly to the degree of neurapraxia. ENoG recordings from more than one facial region may add prognostic information.