Posterior Calvarial Augmentation for Chiari Malformation Type 1 Refractory to Foramen Magnum Decompression.

Background: Chiari 1 malformation is a structural abnormality of the hindbrain and posterior fossa characterized by herniation of the cerebellar tonsils through the foramen magnum. Although asymptomatic in some cases, hindbrain herniation can be associated with disruption of cerebrospinal fluid flow dynamics at the craniovertebral junction and syrinx formation, leading to symptoms. Foramen magnum decompression with or without duraplasty has been the most commonly performed surgical procedure in the management of this condition. The management of syringomyelia associated with Chiari malformation is more challenging and controversial. Although the associated syrinx can significantly improve after craniovertebral decompression and restoration of cerebrospinal fluid flow, in some cases, it will persist despite decompressive surgery and could even continue to enlarge.

Case Description: We have described the case of a 4-year-old boy with non-craniosynostotic Chiari malformation and extensive cervical syrinx who, despite foramen magnum decompression and further revision, continued to deteriorate clinically and radiologically. Posterior calvarial augmentation was performed as a salvage procedure, with resolution of the tonsillar herniation and syrinx.

Conclusions: Posterior calvarial augmentation is a viable option for patients with Chiari malformation refractory to foramen magnum decompression.