Potential misdiagnoses of Bell's palsy in the emergency department

We evaluate the incidence of potentially incorrect emergency department (ED) diagnoses of Bell's palsy and identify factors associated with identification of a serious alternative diagnosis on follow-up.

We performed a retrospective cohort study from California's Office of Statewide Health Planning and Development for 2005 to 2011. Subjects were adult patients discharged from the ED with a diagnosis of Bell's palsy. Information related to demographics, imaging use, and comorbidities was collected. Our outcome was one of the following diagnoses made within 90 days of the index ED visit: stroke, intracranial hemorrhage, subarachnoid hemorrhage, brain tumor, central nervous system infection, Guillain-Barré syndrome, Lyme disease, otitis media/mastoiditis, or herpes zoster. We report hazard ratios (HRs) and 95% confidence intervals (CIs) for factors associated with misdiagnosis.

A total of 43,979 patients were discharged with a diagnosis of Bell's palsy. Median age was 45 years. On 90-day follow-up, 356 patients (0.8%) received an alternative diagnosis, and 39.9% were made within 7 days. Factors associated with the receiving alternative diagnosis included increasing age (HR 1.11, 95% CI 1.01 to 1.21, every 10 years), black race (HR 1.68; 95% CI 1.13 to 2.48), diabetes (HR 1.46; 95% CI 1.10 to 1.95), and computed tomography or magnetic resonance imaging use (HR 1.43; 95% CI 1.10 to 1.85). Private insurance was negatively associated with an alternative diagnosis (HR 0.65; 95% CI 0.46 to 0.93). Stroke, herpes zoster, Guillain-Barré, and otitis media accounted for 85.4% of all alternative diagnoses.

Emergency providers have a very low rate of misdiagnosing Bell's palsy. The association between imaging use and misdiagnosis is likely confounded by patient acuity. Increasing age and diabetes are modest risk factors for misdiagnosis.