Is Bell’s palsy a bilateral condition? A temporal magnetic resonance image analysis of contrast enhancement across all segments of the facial nerve

OBJECTIVE: To determine the contrast enhancement values in the facial nerve segments using magnetic resonance imaging (MRI) and to examine the association with clinical progress in Bell's palsy. MATERIALS AND METHODS: Temporal MRI images of 90 adult patients with Bell's palsy and 45 individuals without facial nerve pathology (control group) were analyzed retrospectively. Each of the five intratemporal segments of the facial nerve was delineated bilaterally, and quantitative values obtained using point-shaped ROI (region of interest) were recorded. These values were compared between the affected and unaffected sides of Bell's palsy patients, as well as between the unaffected side and the control group. The association between the disease's progress was examined. RESULTS: The ROI value of the affected side of the patients was significantly greater than the normal side in all segments. Contrast measures in five separate patient segments could not predict improvement after three months. At the end of the 6th month, ROI values could not predict whether the patient would have progression or not. In all 5 segments, ROI intensity values were found to be significantly higher in the unaffected sides of patients than in the ears of healthy individuals in the control group. CONCLUSION: The mean ROI intensity value in any segment of the facial nerve on the affected side could not predict the prognosis of patients with Bell's palsy. The considerable rise in signal intensity values evaluated by point-shaped ROI may suggest a possible role for systemic and local immunological responses; however, this interpretation remains a hypothesis, as no direct laboratory immunological evidence was obtained in the present study.