Study Design. The issue of progression of congenital basilar invagination is evaluated on the basis of 3 clinical cases. The rationale of treatment of basilar invagination in general and, particularly, in the complex clinical situation encountered in the presented cases, by the authors' technique of atlantoaxial joint distraction, reduction of basilar invagination, and direct lateral mass plate and screw fixation is discussed. Objective. The subject of progression of congenital basilar invagination and recurrent craniocervical cord compression after an initial transoral decompression is analyzed, and an alternative surgical treatment involving craniovertebral bone realignment is suggested. Summary of Background Data. This is a review of 3 cases of basilar invagination treated earlier by transoral decompression. No fixation procedure was performed. The patients presented with recurrent symptoms of high cervical cord compression. Investigations revealed a progression of basilar invagination and cord compression. The treatment of such a complex clinical situation by atlantoaxial joint distraction is discussed. Methods. Between September 2001 and January 2004, we treated 3 patients with congenital basilar invagination who underwent transoral odontoidectomy but did not undergo any posterior atlantoaxial or occipitoaxial fixation. The patients had postoperative improvement but worsening of their neurologic condition after an average duration of 26 months after transoral surgery. Repeat investigations revealed that basilar invagination and the craniovertebral alignments worsened during the period, and there was recurrent cervicomedullary cord compression. These patients were treated by atlantoaxial facet distraction, and attempts were made toward reduction of the basilar invagination and craniovertebral junction bony realignment, and atlantoaxial fixation by the technique recently described by us. Results. During the average follow-up of 25 months, all 3 patients have had a neurologic recovery. Conclusions. The probable cause of basilar invagination and its progression is a congenital malformation of alignment of the facets of the atlantoaxial joint. Distraction of the facets and direct interarticular atlantoaxial fixation presents a unique opportunity of reduction of the basilar invagination and fixation of the region.
