The role of limited posterior fossa craniectomy in the surgical treatment of Chiari malformation Type I: experience with a pediatric series

Abstract

Despite progress in the understanding of the causes and pathophysiology of Chiari malformation Type I (CM-I), definitive surgical treatment remains unresolved. Various techniques have been propounded over the years, but there is no general consensus on the most appropriate surgical management for this condition. The authors report their experience with the surgical treatment of 30 pediatric patients with CM-I. The results obtained in 30 patients who underwent surgery for symptomatic CM-I with a purely extradural procedure were retrospectively reviewed. The patient age at operation ranged from 2 months to 16 years (mean 68 months). In 26 patients the CM-I occurred as an isolated disease, whereas in four a recognized bone anomaly involving the cranial base (achondroplasia) was observed. All patients underwent suboccipital craniectomy, which was accompanied by C-1 laminectomy in 22. In all cases a thick fibrous band at the level of foramen magnum was resected; in 11 children serial incisions of the outer layer of the dura mater were performed as well to expand the posterior fossa volume. The follow-up duration varied from a minimum of 12 months to 12.6 years (mean 4.7 years). The most frequent symptoms and signs were head and/or neck pain (56.7%), followed by vertigo (27.7%), upper-and lower-extremity weakness (20.0%), and ataxia (20.0%). Syringomyelia was noted in 12 patients (40.0%) on magnetic resonance (MR) images. Improvement in or resolution of clinical symptoms and signs was observed in all patients. However, only minimal or no modifications could be found in the position of cerebellar tonsils on postoperative MR images in most patients (only occasional improvement in tonsillar herniation), whereas syringomyelic cavitations reduced in size in half of the cases. Nevertheless, in only two patients was a reoperation necessary. In the authors' experience, suboccipital craniectomy and C-I laminectomy (eventually integrated by dural delamination) can represent an effective treatment for symptoms associated with CM-I.