Cauda Equina Malignant Peripheral Nerve Sheath Tumor Presenting with Subarachnoid Hemorrhage: A Case Report

Introduction: Malignant peripheral nerve sheath tumors (MPNST) are uncommon aggressive neoplasms. This type of tumor is frequently associated with type I neurofibromatosis and is usually found in the extremities, trunk, head, and neck. There are only 6 reported cases of intradural lumbar spine MPNST. This is the eldest patient presenting with an intradural MPNST, and the first with intraoperative and radiological findings of associated subarachnoid hemorrhage.

Methods: We report a case with an atypical presentation of MPNST at an academic institution in Colombia in March 2022. We collected information regarding his clinical features, diagnosis, and treatment.

Results: A 72-year-old man presented to the emergency department with severe acute low back pain. His medical history was positive for recent non-quantified weight loss. Neurological examination was unremarkable. Gadolinium-enhanced lumbar spine MRI showed an irregularly shaped intradural lesion extending from L3 to L5. The lesion appeared as isointense on T1 and T2-weighted imaging with the presence of central void and peripheral enhancement. The suspicion of a ruptured spinal vascular malformation was ruled out by spinal digital subtraction angiography. Through an L3, L4, and L5 laminectomy, a diffuse subarachnoid hemorrhage, and a tumor tightly adherent to cauda equina nerve roots were found. Gross total resection was achieved. Specimen examination revealed a fusocelular tumor with pleomorphic and hyperchromatic nuclei. The lesion was positive for S100, and SOX10. Ki67 proliferative index was 15%, and a diagnosis of MPNST was made.
Moreover, bone and cartilage specimens were negative for malignancy. The patient received 25 sessions of fractionated radiotherapy. On a 7-month follow-up, he had no neurological deficit, with a Karnofsky performance score of 90 points.

Conclusion : The diagnosis of lumbar spine intradural MPNST is challenging due to its rare frequency. Surgical evidence of subarachnoid hemorrhage is a novel finding.