Inaugural Sixth Nerve Palsy in a Patient with Neuroborreliosis: A Case Report

Background: We report an uncommon presentation of Lyme disease and highlight the importance of a detailed history in a patient with new-onset sixth nerve palsy. Methods: Case report and literature review. Results: A 46-year-old man receiving infliximab presented to the ophthalmology emergency department with horizontal binocular diplopia. History revealed a diffuse headache that had begun three weeks earlier. Ophthalmologic examination demonstrated a left sixth cranial nerve palsy. The workup showed positive Borrelia serum IgG, which was interpreted as a likely false-positive result given the limited specificity of serologic testing. At follow-up, the patient reported left-sided peripheral facial palsy, and worsening headache and diplopia. Further history revealed prior erythema migrans treated with doxycycline four months earlier. Considering these new findings, a lumbar puncture was performed and demonstrated intrathecal production of Borrelia antibodies. Neuroborreliosis, a neurologic involvement secondary to systemic infection by the spirochete Borrelia burgdorferi, was diagnosed. The patient was treated with oral doxycycline for 28 days with complete resolution of symptoms. Conclusions: Lyme disease may present with progressive neuro-ophthalmologic symptoms, underscoring the crucial role of ophthalmologists in its diagnosis. Moreover, immunosuppression may delay diagnosis and allow neurological progression, highlighting the need for careful history taking and close follow-up.