Bilateral facial nerve palsy as a presentation of coexisting neuroborreliosis and post-acute COVID-19 syndrome.

Bilateral simultaneous facial nerve palsy is an extremely rare condition that may be induced by infection (bacterial, viral, or fungal) or noninfective causes (autoimmune, traumatic, or structural). The treatment depends on the underlying disorder, and, if it is introduced on time, the disease is in most cases completely reversible. We report on a patient with bilateral simultaneous facial nerve palsy without an obvious cause. The possible causes were SARS-CoV-2 infection and postvaccination syndrome. After we excluded the SARS-CoV-2 infection, a wide range of diagnostic tests were conducted. Magnetic resonance imaging after gadolinium intravenous application showed bilateral facial nerve enhancement. Serological tests revealed Borrelia burgdorferi, and the result was confirmed by an enzyme-linked immunosorbent assay (IgM positivity). After 14 days of antibiotic therapy, the symptoms resolved completely without sequelae. This report shows that the symptoms of bilateral simultaneous facial nerve palsy may completely resolve if thorough clinical investigation and an appropriate early treatment are applied.