Microsurgical resection of a perimedullary conus medullaris arteriovenous fistula type IVa: a case report.

Introduction and importance: Conus medullaris arteriovenous fistulas (AVFs) are rare among spinal vascular malformations. This case report highlights the presentation, diagnostic work-up, and management of a patient with a perimedullary conus medullaris AVF type IVa. Case presentation: A 29-year-old male presented with progressive weakness and numbness in the left leg. Thoracic magnetic resonance imaging (MRI) showed increased arterial supply in the dural membrane and large, smoldering, twisting spaces from T8 to L1 with a central point from which many abnormal vessels radiated. Angiographic findings showed an enlarged fistula fed by a radiculomedullary artery around the T10 level and draining through a medullary vein, draining into an aberrantly placed radicular vein at the posterior spinal venous plexus. The vein was mimicking nidus. Clinical discussion: The microsurgical resection with intraoperative indocyanine green angiography and neuromonitoring was successful. A follow-up MRI showed postoperative resolution of the malformation, and clinically, the patient experienced gradual improvement of his symptoms confirming the surgical success with complete AVF obliteration on postoperative angiography. Conclusion: Accurate detection and precise treatment are essential for managing conus medullaris AVFs. These complex lesions can be effectively addressed through both microsurgical and endovascular techniques. A successful treatment strategy necessitates thorough preoperative planning and a collaborative, multidisciplinary approach.