The Significance of Bell's Palsy That Presents as Monocranial Versus Polycranial Neuropathy: A Case Series and Systematic Literature Review

Purpose: To investigate the effect of Bell's palsy (BP) presenting as polycranial neuropathy (PCN) compared with BP caused by isolated facial nerve (CNVII).Methods: We carried out a retrospective cohort study of the medical records of all consecutive patients who were diagnosed with BP at a single tertiary referral center between 2010 and 2017. Included were patients 18 years or older who were clinically diagnosed with BP and completed 7 days of systemic steroidal treatment and at least 6 months of follow-up. The patients were divided into two groups according to whether the BP derived from a monocranial neuropathy or a PCN. Demographics and BP severity and outcome were compared between these groups. A systematic literature review using Medline via "PubMed," "Embase," and "Web of Science" was conducted.Results: In total, 321 patients with BP were enrolled. The median (interquartile range) age at presentation was 44 (33-60) years. Sex distribution showed male predominance of 57.6% (n = 185) versus 42.4% (n = 136), and 21.2% (n = 68) had PCN. The most concomitantly affected cranial nerve (CN) was the trigeminal (CNV; n = 32, 47%), followed by the glossopharyngeal nerve (CNIX; n = 14, 21%) and the audiovestibular nerve (CNVIII; n = 10, 15%). Age, House-Brackmann score on presentation, and diabetes mellitus (DM) were independent predictors for PCN etiology (p = 0.001, p = 0.034, and p < 0.001, respectively). Each increase in 1 year of age was associated with additional odds ratio (95% confidence interval) of 0.97 (0.95-0.99) for PCN. The odds ratio (95% confidence interval) associated with DM was 8.19 (4.02-16.70). Our systematic literature review identified 1,440 patients with the PCN type of BP. The most commonly affected CN was the trigeminus (25-48%), followed by the glossopharyngeal and audiovestibular nerves (2-19% and 0-43%, respectively).Conclusion: The severity of facial weakness on initial presentation among PCN patients was significantly higher compared with the monocranial neuropathy-type BP patients. The authors believe that the significant association and prevalence rate ratio between DM and PCN warrant that a patient presenting with PCN undergo screening for DM.