Microsurgical removal of a C1-C5 laterally located intramedullary subependymoma through a postero-lateral sulcus approach: case report, surgical video and critical review of diagnostic and surgical challenges

Introduction Spinal subependymomas are rare, benign, and slow-growing intramedullary tumors, often misdiagnosed pre- operatively due to their radiological resemblance to more common spinal cord neoplasms such as ependymomas and astro- cytomas. Given their rarity, the optimal surgical approach and oncological strategy remains debated. While these tumors are histologically benign, obtaining a definitive diagnosis is crucial due to the diagnostic overlap with more aggressive lesions. In this case, a postero-lateral sulcus approach was selected based on the tumor’s location and spinal cord rotation, allowing for a safe resection while preserving spinal cord function. Case Presentation A 41-year-old female presented with progressive right arm weakness over two years, followed by gait instability, paresthesia, and severe tetraparesis. Neurological examination revealed right-sided paresis, sensory deficits, and an unsteady gait. MRI demonstrated a T2-hyperintense, T1-hypointense intramedullary lesion from C1 to C5, with an eccen- tric localization and subpial extension, raising suspicion for an astrocytoma or ependymoma, though a subependymoma remained a consideration. Given the patient’s progressive deterioration and the need for a histological diagnosis, surgical intervention was performed. A postero-lateral sulcus approach was chosen due to the lesion’s lateral subpial emergence. Intraoperative mapping and neuromonitoring were used to preserve the corticospinal tracts and posterior columns. The tumor was carefully dissected through working windows between the dorsal root entry zones and was completely removed without significant neuromonitoring changes. Histological analysis confirmed the diagnosis of subependymoma, with a low Ki-67 index and no high-grade features. Postoperatively, the patient experienced transient worsening of motor deficits but showed progressive improvement, regaining full right arm function and near-normal gait at follow-up. No adjuvant therapy was required. Conclusion This case highlights the diagnostic challenges of spinal subependymomas and the role of surgery in securing a definitive diagnosis. The postero-lateral sulcus approach, enabled by the tumor’s location and spinal cord rotation, provided a safe and effective approach. Intraoperative mapping and neuromonitoring were essential in minimizing surgical morbidity. Given their benign nature, complete resection is curative, and no additional treatment is required. This report underscores the importance of an individualized surgical strategy in managing rare intramedullary tumors with uncertain preoperative diagnosis.