Biportal Endoscopic Foramen Magnum Decompression in an Arnold-Chiari Malformation: A Technical Note With a Case Report

Chiari malformation, when accompanied by progressive neurological symptoms or syringomyelia, often necessitates surgical decompression. Although endoscopic spinal surgery continues to advance, its application in foramen magnum decompression remains limited. This video article demonstrates the biportal endoscopic foramen magnum decompression technique for Chiari type I malformation. We present the case of a 19-year-old female patient with progressive headache, motor weakness, and radiological evidence of 7-mm tonsillar descent with C2–7 syringomyelia. She successfully underwent biportal endoscopic foramen magnum decompression with C1 laminectomy. The procedure employed a triportal approach with safe docking on the C2 spinous process, allowing a minimally invasive C1 laminectomy and foramen magnum decompression extended to the suboccipital area. Postoperatively, computed tomography confirmed adequate decompression, and magnetic resonance imaging revealed expansion of the posterior fossa with resolution of tonsillar herniation. The patient experienced no complications or symptom recurrence at the 3-month follow-up. Despite a minor intraoperative–postoperative measurement discrepancy, which highlights the anatomical considerations required to achieve sufficient decompression, this video supports the feasibility of biportal endoscopic surgery. This approach may provide comparable clinical outcomes to conventional open surgery while offering minimally invasive advantages, though long-term follow-up remains essential.