Surgical management of Chiari malformation: analysis of 128 cases.

OBJECTIVE: A variety of surgical interventions have been recommended for patients with Chiari malformations (CMs). In this study, we have evaluated the intraoperative findings and clinical outcome in different-aged patients with CMs undergoing posterior fossa decompression.

METHODS: Sixteen pediatric and 112 adult cases with CMs underwent suboccipital craniectomy and wide duraplasty as well as autogenous bone grafting in selected cases. The clinical outcome was assessed by evaluation of postoperative signs and symptoms and magnetic resonance imaging of the craniocervical junction.

RESULTS: The most striking intraoperative finding was the presence of a very thin membrane over the opening of the central canal; the occurrence of this membrane in pediatric patients was significantly higher than that in adults (94 and 43%, respectively; p < 0.05, Fisher's exact probability test). During the immediate postoperative period, 81% of pediatric CMs and 90% of adult CMs showed improved symptomatology and magnetic resonance imaging revealed favorable findings comprising syrinx collapse or reduction of the syrinx diameter in 14 (88%) pediatric and 92 (82%) adult CMs. During discharge from hospital, 103 (90%) patients with CMs type I and 11 (85%) with CMs type II achieved good results. However, there was a statistically significant difference in the occurrence of poor results between patients treated with bony fusion and those without fusion (24 vs. 6%;p < 0.05, Fisher's exact probability test). The incidence of vertebral instability was markedly augmented in pediatric CMs in comparison to adult CMs (19 vs. 2%; p < 0.01, Fisher's exact probability test).

CONCLUSIONS: Suboccipital decompression and duraplasty with autogenous bone grafts in selected cases are effective treatments for most patients with CMs. A higher incidence of a special membrane over the obex and atlantoaxial instability were closely associated with childhood CMs.