A Spine Friendly "Backdoor Anterolateral Retroperitoneal Approach" for the Treatment of Giant Extraforaminal L5-S1 Spinal Schwannoma: A Case Report.

Schwannomas, or peripheral nerve sheath tumors, involving the retroperitoneal space are rare, accounting for approximately 3%-5% of all tumors, and most commonly arise from the eighth cranial nerve and spinal nerve roots. Extraforaminal retroperitoneal spinal schwannomas of the lumbosacral region are particularly uncommon and present unique surgical challenges due to their deep location and proximity to major neurovascular structures. Gross total resection remains the treatment of choice; however, conventional posterior and transparaspinal approaches often require bone removal and extensive paraspinal muscle dissection, potentially resulting in postoperative pain, paraspinal muscle morbidity, and spinal instability. We report the case of a 39-year-old female who presented with clinical and radiological features consistent with an extraforaminal retroperitoneal L5-S1 spinal schwannoma. After a thorough preoperative evaluation, the patient underwent complete tumor excision using a backdoor anterolateral retroperitoneal approach, selected to minimize tissue disruption while preserving spinal biomechanics. This approach provided a wider operative corridor with enhanced visualization of the lesion and adjacent neural structures, facilitating safe dissection and gross total resection through the intervertebral foramen without violation of posterior bony elements or excessive muscular stripping. The postoperative course was uneventful, and spinal stability was maintained. This case demonstrates that the backdoor anterolateral retroperitoneal approach is a safe and effective alternative for selected extraforaminal retroperitoneal lumbosacral schwannomas, enabling adequate exposure and complete excision while avoiding the biomechanical compromise commonly associated with traditional posterior approaches.