Chiari Malformation: Diagnosis, Classifications, Natural History, and Conservative Management. WFNS Spine Committee Recommendations.

STUDY DESIGN: A comprehensive search was conducted in PubMed/EMBASE/MEDLINE databases. Inclusion criteria included publications between January 2011 and December 2022 on CM diagnosis classification, natural history, and conservative management. OBJECTIVE: This study aims to offer an update on diagnosis classifications, natural history, and conservative management in Chiari Malformation (CM). SUMMARY OF BACKGROUND DATA: Chiari Malformation type 1 involves cerebellar tonsil herniation leading to neurological symptoms. There is controversy regarding its pathophysiology and optimal management, especially for asymptomatic cases. Previous research has focused on surgical outcomes with limited consensus on conservative strategies. Standardized guidelines are needed to enhance clinical decision-making. METHODS: The screening process involved reviewing abstracts, assessing full-text articles, and reviewing references. Eligibility criteria ensured the selection of relevant studies. Data extraction involved recording various variables. Results were discussed and voted in two consensus meetings of the WFNS Spine Committee, reaching consensus using the Delphi method. RESULTS: A total of 164 abstracts were screened. 99 articles met the inclusion criteria and were included in the study. Headache, brainstem and/or cerebellar/brainstem symptoms/signs were confirmed as the main typical neurological hallmarks of CM. Still, an accurate clinical assessment appeared to be the most reliable evaluation model available. Considering classification, the most common form in adult is type 1, while type 2 is associated with myelo-meningocele and hydrocephalus from childhood. MRI is the gold standard to show extent of tonsillar herniation, overcrowded posterior fossa or the absence of cisterna magna. Focusing on natural history, for asymptomatic or mildly symptomatic radiologically positive patients a conservative management is appropriate. Somato-sensory, motor, brainstem auditory evoked potentials and polysomnography could be helpful to guide eventual surgical indication. CONCLUSION: Further higher-quality studies are recommended to establish more substantial evidence and recommendations.