L5 Motor Paresis and Foot Drop Following Herpes Zoster Reactivation: An Unusual Presentation and Diagnostic Challenge in an Immunocompetent Patient - A Case Report.

This is the case of a 67-year-old immunocompetent Hispanic male residing in Mexico who presented with acute right lower back and right lateral thigh pain. Initial imaging was unremarkable. He later developed painful vesicular lesions on the right foot and buttock. He was diagnosed with herpes zoster and initiated acyclovir and gabapentin. Ten days later, he developed foot drop, leg weakness, and urinary incontinence. Magnetic resonance imaging (MRI) showed enhancement of the cauda equina, and electrodiagnostic studies demonstrated right lumbar polyradiculopathy. The patient improved significantly with pain medications and physical therapy. After 8 months of physical therapy, he demonstrated significant clinical improvement. This case highlights the uncommon presentation of motor involvement in herpes zoster and emphasizes the role of imaging and electrophysiology in guiding diagnosis and management.