Potential Misdiagnosis of Bell's Palsy in the Emergency Department

Abstract

Unilateral facial paralysis may be caused by a host of diseases other than Bell's palsy (BP), some more serious or potentially life threatening. The objective of this study is to describe the incidence and risk factors of potentially incorrect emergency department (ED) diagnosis of BP, defined by subsequent diagnosis of a serious and likely alternative disease. This is a retrospective cohort study using data from the state of California's Office of Statewide Health Planning and Development (OSHPD) for years 2005-2011. We identified a cohort of adult patients (age > 17 years) with a primary ED diagnosis of BP using International Classification of Diseases, Ninth Revision code 351.0. We collected information included in the database related to age, sex, race/ethnicity, insurance status, day of the week, computed tomography (CT) or magnetic resonance imaging (MRI) use, and comorbidities. Our primary outcome was a composite of the following serious ED or inpatient discharge diagnoses within 90 days of the index ED BP diagnosis: ischemic stroke, intracranial hemorrhage, or subarachnoid hemorrhage; brain tumor; central nervous system infection, including meningitis, encephalitis, and brain abscess; human immunodeficiency virus infection; Guillain-Barre syndrome (GBS); Lyme disease; otitis media or mastoiditis; or herpes zoster. We report medians and percentages for continuous and categorical data, respectively and performed survival analysis to determine the combined cumulative incidence of our outcome diagnoses during 90-day follow-up. A multivariable Cox proportional hazards model was used to identify hazard ratios (HR) and 95% confidence intervals (CIs) for demographics, imaging use, and comorbidity-related variables that we thought may be associated with misdiagnosis of BP. In California EDs between 2005-2011, there were 43,979 patients diagnosed with BP. Median age was 45 years (IQR 32 to 57). A total of 6,149 (14.0%) underwent CT and/or MRI imaging. On 90-day follow-up, 356 patients (0.8%) received one of our predefined serious alternative diagnoses. Demographic factors or comorbid conditions positively associated included increasing age (HR 1.10, 95% CI 1.01-1.21, for every 10 years) and black as compared to white race (HR 1.68, 95% CI 1.13-2.48), and diabetes mellitus (HR 1.46, 95% CI 1.10-1.95). The use of CT or MRI imaging on the index visit was also associated with an increase in the misdiagnosis of Bell's palsy (HR 1.43, 95% CI 1.10-1.85). Private insurance, as compared to Medicare, was negatively associated with an alternative diagnosis (HR 0.65, 95% CI 0.46-0.93). Of the 356 individuals with an alternative diagnosis within 90 days, 142 (39.9%) were within seven days. Most common, at all four time intervals, were ischemic stroke, herpes zoster, GBS, and otitis media, accounting for 85.4% of all alternative diagnoses. Emergency providers adequately diagnose Bell's palsy in the ED with a low rate of missing serious or life-threatening alternate diagnoses on 90-day follow-up. The association between use of CT/MRI and misdiagnosis is likely confounded by patient acuity or complexity. Increasing age and diabetes mellitus are modest risk factors for misdiagnosis of Bell's palsy and particular attention should be given to these patients.