Foramen Magnum Decompression for Retro-Odontoid Pseudotumor in an Elderly Patient With Chiari Malformation Type I: A Case Report.

Chiari malformation type I (CM-I) is uncommon in elderly patients, and surgical experience in this population remains limited. Long-term outcomes after surgery, particularly following prolonged conservative observation, have rarely been reported. We present an 82-year-old woman with CM-I who developed neurological deterioration due to a retro-odontoid pseudotumor (ROP) after two decades of clinical stability. Foramen magnum decompression (FMD) was performed without postoperative complications, resulting in marked neurological improvement. She was discharged, and long-term follow-up demonstrated sustained clinical and radiological recovery. This case highlights that advanced age alone should not preclude surgical intervention in CM-I when progressive neurological decline occurs.