Cranial nerve VII on gadolinium contrast-enhanced magnetic resonance imaging in the case of Bell’s palsy

Abstract

Bell’s palsy is a rapid unilateral peripheral paralysis of cranial nerve VII whose etiology is varied, most commonly associated with an acute infectious or inflammatory demyelinating process. Nerve injury can result in edema because of increased permeability of vascular structures, which can sometimes be seen as a locus of enhancement of magnetic resonance imaging (MRI). Bell’s palsy is typically considered a clinical diagnosis and the specificity and sensitivity of imaging have been poorly studied. Herein is describe a case of a 73-year-old male who presented to the emergency department with left-sided facial droop and no other focal neurological abnormalities. With a history of a Janus kinase 2 (JAK2) mutation and the new initial facial drooping, acute cerebrovascular insult was high on the differential. Initial labs and computerized tomography (CT) head were inconclusive, but MRI showed pronounced enhancement of the left distal internal carotid artery (ICA) with contiguous enhancement of the labyrinthine, geniculate, and tympanic segments of the left facial nerve. Diagnosing Bell’s palsy can be a challenge as there are numerous postulated etiologies stemming from trauma, infection, and neoplasm; with infection (particularly viral) postulated to be the most likely source. Though MRI is currently not validated as a tool in expediting Bell’s palsy diagnosis, findings such as the enhancement seen here provide some insight into the benefit of MRI as a diagnostic modality in some cases. This case is unique both for the diagnostic dilemma between stroke and Bell’s palsy and the potential for MRI imaging to help guide clinical decision-making into treatment.