Evaluating the role of craniocervical and atlantoaxial instability in autonomic dysfunction: a narrative review

Background Autonomic dysfunction is a complex condition that affects every organ system in the body. The underlying mechanisms of autonomic dysfunction remain incompletely understood. There appears to be an association between patients with hypermobile Ehlers Danlos syndrome (hEDS), craniocervical instability (CCI), atlantoaxial instability (AAI), and autonomic dysfunction. There is biological plausibility for CCI and AAI being causes for autonomic dysfunction in these populations. Objective The objective of this review is to explore the literature on the potential association between CCI, AAI and autonomic dysfunction and to explore the biological plausibility of this association. Methods A narrative review of PubMed was conducted through August 2026 to evaluate associations among hEDS, CCI/AAI, and autonomic dysfunction. Studies addressing autonomic dysfunction in hypermobility disorders, CCI/AAI, autonomic outcomes following cervical stabilization surgeries, and proposed neurovascular or autonomic mechanisms were included. Findings were synthesized narratively due to the heterogeneity of the study designs analyzed and outcome measures assessed. Results 43 studies were included in the final review. Evidence consistently supported an association between hEDS and autonomic dysfunction and between hEDS and CCI/AAI. More limited evidence demonstrated a direct overlap between CCI/AAI and dysautonomia, while multiple series reports showed improvements in autonomic-associated symptoms following surgical stabilization procedures. Proposed mechanisms for autonomic dysfunction in CCI/AAI patients include vagal nerve involvement, internal jugular vein compression, altered cerebral venous outflow, and cervicomedullary effects. The evidence was predominantly retrospective and heterogeneous, with limited standardized autonomic testing, warranting further investigation and more robust future analysis. Conclusion Current evidence suggests that CCI and AAI represent under-recognized contributors to dysautonomia. While causality has not been established, anatomical, physiological, and clinical observations warrant further investigation into this relationship. Standardized diagnostic criteria for CCI/AAI, as well as autonomic dysfunction, must be established to further study these relationships. Prospective studies incorporating these diagnostic criteria and objective autonomic measurements will assist in clarifying these relationships and determine what interventions will help improve patient outcomes.