S2-08 SESSION 2: POSTERIOR VAULT DISTRACTION POSTERIOR CALVARIAL DISTRACTION − A SAFE AND EFFECTIVE FIRST-LINE TREATMENT FOR CHILDREN WITH COMPLEX CRANIOSYNOSTOSIS AND CHIARI MALFORMATION

Introduction: Posterior calvarial distraction (PCD) is an effective method to increase the intracranial volume in children with craniosynostosis. Children with multi-suture and lambdoid synostosis often have concurrent Chiari malformation type I (CM1). This study investigated the efficacy of PCD in posterior fossa (PF) volume expansion and treatment of CM1. Methods: Ten-year retrospective study in a quaternary craniofacial unit. Results: Sixteen children were identified (8M, 8F). The mean age was 5.1 years (8m to 19y). Fourteen children had pansynostosis and two lamboid synostosis; 8 were syndromic. Ten patients had raised intracranial pressure (ICP); 4 had syringomyelia. Clinically, 9 patients improved, 7 remained stable, none deteriorated. The average distraction distance was 23mm (16-28mm). An osteotomy extending inferior to the torcula was associated with a larger PF AP distance increase (13 v 6mm, p=0.028). The average tonsillar descent improved (9.3 to 6.0mm). Syrinx dimensions also improved: superior-inferior (203 to 136mm), anterior-posterior (7.9 to 3.1mm). Conclusion: Cranial volume expansion following PCD also includes PF volume expansion. This results in improvement of tonsillar descent and syrinx. PCD is a safe and efficacious first-line treatment for children with concurrent multi-suture craniosynostosis, CM1, and syrinx. The findings add to existing hypotheses that Chiari malformation is not a condition per se, but a manifestation of an insufficient intracranial volume.