Spontaneous regeneration of the foramen magnum after decompressive suboccipital craniectomy in Chiari malformation: case report.

A 21-year-old woman, who had undergone foramen magnum decompression for her symptomatic Chiari malformation (Type 1) 7 years before, presented with recurrence of the symptoms. Neuroradiological examinations demonstrated regeneration of the foramen magnum that was caused by new bone formation, as confirmed at the second surgery. Neurological improvement was obtained after the removal of the regenerated foramen magnum. This observation, though rare, deserves to be kept in mind during the postoperative follow-up period in young patients with Chiari malformation.