The complex Chiari: issues and management strategies

“Complex Chiari” malformations may be defined as cerebellar tonsil herniation combined with one or more of the following radiographic findings: brainstem herniation through the foramen magnum (Chiari 1.5 malformation), medullary kink, retroflexed odontoid, abnormal clival-cervical angle, occipitalization of the atlas, basilar invagination, syringomyelia or scoliosis. Patients with “complex Chiari” malformation are different from those with typical Chiari 1 malformation in that their management strategy has a higher chance of including other operative interventions aside from a typical suboccipital decompression. These other operative procedures include odontoid resection and craniocervical fusion. This paper outlines specific scenarios where these other operative procedures must be considered and carried out.