Lumbar Microdiscectomy: A Rare Case of a Duplicate L5 Exiting Nerve Root

The microdiscectomy procedure has been regarded as the preferred method for the treatment of lumbar disc herniation (LDH). Intraoperatively, the procedure may be further complicated due to underlying anatomical variations in the lumbar spine or nerve root variations. Nerve root anomalies (NRAs), in particular, are relatively underdiscussed within the literature. Despite the rarity of these variations to the exiting nerve root, the increased surgical risk that an NRA may add warrants the need for increased awareness and associated complication mitigation. This case describes a rare instance of a symptomatic duplicate L5 nerve root discovered preoperatively and highlights the steps taken to minimize iatrogenic risk. This study is designed as a retrospective case report with formal informed consent provided by the patient. A thorough chart review was performed for this subject, including all prior medical records, imaging studies, imaging reports, operative notes, and communication records. This patient's preoperative lumbar MRI demonstrated severe left foraminal narrowing at L5-S1 with disc encroachment upon the exiting L5 nerve root and traversing S1 nerve root. The patient was described as having a type 1a NRA. Meticulous consideration was made intraoperatively with no known sustained iatrogenic injury. Preoperative awareness of NRAs, careful dissection, and thorough intraoperative visualization of neural structures are paramount to minimizing the risks of surgical complications. Surgeons should be aware of NRA classification systems and have a surgical plan in place to mitigate risk. Improved awareness may increase the likelihood of preoperative diagnosis and prevent iatrogenic injury.