Intracranial erosion of an occipitocervical rod through the foramen magnum following occipitocervical fusion for retro-odontoid pannus: illustrative case.

backgroundRetro-odontoid pannus can cause craniocervical instability and cervicomedullary compression. Occipitocervical fusion (OCF) is an established treatment, but hardware-related complications remain significant. Intracranial rod migration through the foramen magnum is exceedingly rare and poses substantial neurological risk. OBSERVATIONS: A 76-year-old man with retro-odontoid pannus and progressive myelopathy underwent OCF. Months later, he developed wound complications and mechanical failure. Imaging revealed superior rod migration with erosion through the foramen magnum and intracranial extension. A staged surgical strategy was utilized: initial hardware removal and soft tissue reconstruction, followed by targeted left suboccipital craniectomy, durotomy, and ultrasound-guided extraction of the migrated rod. Revision C1 laminectomy and allograft C1-2 arthrodesis restored construct stability. The patient recovered without new neurological deficits and experienced improvement in gait imbalance. LESSONS: Intracranial rod erosion after OCF is rare but should be suspected in the presence of wound breakdown, new posterior fossa symptoms, or construct instability. Prevention requires meticulous rod contouring to avoid occipital contact, secure cranial fixation, and early postoperative surveillance. Management benefits from multidisciplinary collaboration and intraoperative ultrasound for safe extraction in anatomically constrained regions. https://thejns.org/doi/10.3171/CASE25837.