Peripheral Facial Paralysis as a Sentinel Symptom of Early Lyme Neuroborreliosis: A Diagnostic Challenge.

Lyme disease, while well recognized in many regions of the Northern Hemisphere, is generally considered uncommon in Morocco. While erythema migrans represents its hallmark cutaneous manifestation, neuroborreliosis remains a challenging diagnosis, particularly when presenting as isolated peripheral facial paralysis, often mimicking idiopathic Bell's palsy. We report the case of a 55-year-old man presenting with fever followed six weeks later by left-sided peripheral facial paralysis. Neurological examination revealed stage IV facial palsy according to the House-Brackmann classification. Radiological assessment, including computed tomography of the brain and temporal bones as well as magnetic resonance imaging, revealed no abnormalities. Laboratory investigations excluded viral and autoimmune causes. Borrelia burgdorferi immunoglobulin M and immunoglobulin G (IgG) antibodies were detected using the enzyme-linked immunosorbent assay method. Serum Western blot testing confirmed positivity with 8 of 10 IgG bands. Cerebrospinal fluid analysis revealed pleocytosis, with normal protein and glucose levels. A diagnosis of Lyme neuroborreliosis was established. The patient received doxycycline at a dose of 200 mg daily for six weeks, in combination with facial physiotherapy, and was subsequently discharged after achieving full clinical recovery, characterized by complete resolution of the facial paralysis, with normalization of inflammatory biomarkers. This case underlines the importance of considering Lyme neuroborreliosis in the differential diagnosis of facial paralysis, even in non-endemic regions such as Morocco, and highlights the role of comprehensive clinical, radiological, and serological evaluation in establishing an accurate diagnosis.