Unexpected Right-Sided Nerve Root Variant During L4-L5 Microdiscectomy and Decompression: A Case Report Highlighting Diagnostic and Intraoperative Challenges

Lumbosacral nerve root variants may complicate anatomical identification and decompression during lumbar spine surgery. We report a 45-year-old woman with progressive lower limb numbness and paresthesia predominantly affecting the right leg, intermittent low back pain, and right-sided radiating pain aggravated by standing and walking. Examination showed preserved motor strength and sensory impairment in a predominantly right L4 distribution. Preoperative magnetic resonance imaging (MRI) demonstrated an L4-L5 disc bulge with thecal sac indentation, bilateral L5 nerve root abutment, and mild bilateral foraminal narrowing; no nerve root anomaly was reported. During L4-L5 microdiscectomy and decompression, two distinct right-sided neural structures were unexpectedly identified under microscopic visualization and interpreted as suspected duplication of the exiting L4 root. Both structures were preserved during decompression. Retrospective MRI review did not confirm the variant, and intraoperative electrophysiological identification was not feasible. During five months of monthly telephone follow-up, the patient reported improvement in radicular pain, walking tolerance, and sensory symptoms, without reported neurological deterioration. Follow-up neurological examinations and standardized outcome measures were unavailable. This case highlights the importance of recognizing and characterizing unexpected neural anatomy when clinical, imaging, and operative findings do not fully correlate. Definitive anatomical classification and objective postoperative recovery remain uncertain.