Complex Chiari Malformation: What the Neurosurgeon Needs to Know

Chiari malformation type 1 is a frequently encountered but incompletely understood morphologic variant that may present with headache and lower cranial nerve symptoms. The main surgical treatment for Chiari malformation type 1 is suboccipital decompression. Further research has identified a subset of patients with Chiari malformation type 1 with radiographic findings that predispose to suboptimal outcomes from suboccipital decompression alone. This disease process has come to be referred to as complex Chiari malformation. Here, we discuss imaging findings of complex Chiari malformation, identify craniovertebral metrics used to stratify patients, and propose a reporting structure to assist our neurosurgical colleagues in the selection of appropriate treatment.Learning Objective: To understand imaging findings and radiographic metrics associated with Complex Chiari malformation and their implication on surgical management