Pediatric Chiari Formation – Atlantoaxial Instability is the Cause

Background: This study evaluates the role of atlantoaxial instability in the pathogenesis of Chiari malformation in children. Objective: The entity of Chiari formation in pediatric patients and issues in its management are presented. The role of atlantoaxial fixation in pediatric Chiari formation has been analyzed. Material and Methods: Results of 74 pediatric patients with Chiari formation surgically treated by us with atlantoaxial fixation were analyzed. Apart from conventional imaging with plain radiographs, magnetic resonance imaging, and computerized tomography (CT), all patients in the subsequent part of the series underwent dynamic head flexion–extension, head right–left rotation, and lateral right–left head tilt CT imaging. Results: All patients were treated with atlantoaxial fixation using the techniques described in 1994 and 2004. No bone or soft tissue decompression was done in any case. The syrinx was not manipulated in any patient. All patients had gratifying and sustained clinical improvement. Conclusions: Satisfactory clinical outcome in all our patients after atlantoaxial fixation and without any manipulation of neural structures, dura, or bone in the region of foramen magnum consolidates the viewpoint that atlantoaxial instability is the nodal point of pathogenesis of Chiari 1 formation. Dynamic imaging helps in identifying atlantoaxial instability in cases with Chiari formation, even when the other validated parameters are within the range of “normal”. The role of foramen magnum decompression surgery needs to be reassessed.