Odontoid process and clival regeneration with Chiari malformation worsening after transoral decompression: an unexpected and previously unreported cause of “accordion phenomenon”

Purpose: Transoral odontoidectomy followed by occipito-cervical fixation is a widely used approach to relieve ventral compressions at the craniovertebral junction (CVJ). Despite the large amount of literature on this approach and its complications, no previous reports of odontoid process and clival regeneration following transoral odontoidectomy are present in the English literature. Methods: We report the case of odontoid process and clival regeneration following transoral odontoidectomy. Results: A 7-year-old boy presented with symptoms of brainstem and upper cervical spinal cord compression due to a complex malformation at the CVJ including a basilar invagination with Chiari malformation…