Atlantoaxial fixation for failed foramen magnum decompression in patients with Chiari formation

BACKGROUND: Relationship of atlantoaxial instability with Chiari formation is further analyzed in the report. OBJECTIVE: The outcome of 25 patients who had failed conventional treatment for Chiari formation that included foramen magnum decompression surgery and were treated by atlantoaxial fixation is analyzed. MATERIALS AND METHODS: During the period January 2010 to November 2019, we treated 25 patients who had undergone conventionally described surgical procedures; all included foramen magnum decompression for Chiari formation. None of the patients had any craniovertebral junction anomaly. All patients had syringomyelia. All patients had worsened in their neurological condition following surgery either in the immediate or in the delayed postoperative phase. Atlantoaxial instability was diagnosed on the basis of facetal alignment and on the basis of direct observation of joint status by bone manipulation during surgery. The patients were treated by atlantoaxial fixation. Goel clinical grading scale and Japanese Orthopedic Association Score assessed the clinical status both before and after surgery. RESULTS: Following surgery, all patients improved in the clinical condition. The improvement began in the immediate postoperative period and progressed. During the follow-up period that ranged from 4 to 123 months, “significant” neurological recovery and amelioration of presenting symptoms were observed. During the period of follow-up, reduction in the size of syrinx was observed in 14 out of 18 cases where postoperative magnetic resonance imaging was possible. CONCLUSIONS: Clinical results reinforce the belief that atlantoaxial instability is the nodal point of pathogenesis of Chiari formation. Atlantoaxial fixation is the treatment.