Chiari Malformation Type 1: A Systematic Review of Natural History and Conservative Management

Abstract Objective Chiari type 1 malformations (CM-1) are variations of hind-brain development which can sometimes occur in asymptomatic individuals. Conventional treatment is surgical decompression, but little is known about the natural history of patients who do not undergo surgical management. Appreciation of this information is critical to determine how these patients should be managed. We conducted a systematic review of the literature to determine the natural history of CM-1 particularly in patients who did not undergo surgery, and in asymptomatic individuals, to help inform patients and doctors when surgery is likely to be beneficial. Methods A systematic literature search was performed following PRISMA guidelines using the electronic databases PubMed, SCOPUS, the Cochrane foundation and Web of Science. Inclusion and exclusion criteria were predefined. Results In symptomatic patients who did not undergo surgery, headaches and nausea often improved, whereas ataxia and sensory disturbance tended not to improve spontaneously. 27-47% had an improvement in their symptoms after 15 months. 37-40% of patients with cough headache and 89% with nausea who were managed non-operatively improved at follow up. Most asymptomatic individuals with CM-1 remained asymptomatic (93.3%), even in the presence of syringomyelia. Conclusions The natural history of mild symptomatic and asymptomatic CM-1 in adults is relatively benign and non-progressive, therefore the decision to perform surgical decompression should be based on the severity and duration of a patient’s symptoms at presentation. It is reasonable to observe a patient with mild or asymptomatic symptoms, even in the presence of significant tonsillar descent or syringomyelia.