Infectious Mimics of Bell's Palsy: Facial Nerve Palsy Due to Lyme Neuroborreliosis.

Facial nerve palsy (FNP) is a common neurological disorder. There are multiple causes of FNP, and Bell's palsy is defined as an idiopathic cause of FNP. If a patient presents with facial palsy, a full investigation workup should be performed. Lyme disease can present with erythema migrans, fever, headache, muscle and joint pain, and facial palsy. We present a case of a 47-year-old man who presented with progression from unilateral to bilateral FNP. After a series of investigations, he was diagnosed with LNB. Even if MRI findings are normal, cerebrospinal fluid (CSF) analysis and Lyme serology (enzyme-linked immunosorbent assay followed by Western blot) in serum and/or CSF can confirm the diagnosis of neuroborreliosis. We have administered the patient IV ceftriaxone 2 g daily, as per the guidelines. He showed gradual improvement in FNP from House-Brackmann Grade V to Grade II on subsequent follow-ups. This case emphasizes the importance of broad clinical evaluation in diagnosing FNP. Early detection of LNB and initiation of treatment can ensure patients have a favorable outcome.