Intracranial Atherosclerotic Stenosis: Asian Recommendations on Standardized Definitions, Diagnosis and Imaging. A Joint World Stroke Organization (WSO), Asia Pacific Stroke Organisation (APSO), and Philippine Academy of Vascular and Interventional Neurology (PAVIN) Consensus Statement.

INTRODUCTION: Intracranial atherosclerotic stenosis (ICAS) is a leading cause of ischemic stroke, particularly in Asian populations. Despite its significance, standardized definitions, diagnostic criteria, and imaging protocols remain limited, affecting the validity and interpretability of existing data. We aimed to develop expert consensus recommendations for the standardization of definitions, diagnosis, and imaging of ICAS, taking into account the diversity of healthcare resources and infrastructure across Asia.

METHODS: An international multidisciplinary expert panel with broad Asian representation was convened to develop regionally relevant evidence-guided consensus recommendations using a modified Delphi process. Statement development was informed by targeted literature reviews undertaken to address prespecified research questions. The consensus process incorporated iterative voting rounds and an interim non-voting consensus meeting held during the 2026 Philippine Academy of Vascular and Interventional Neurology Biennial Conference. Consensus was predefined as ≥80% agreement.

RESULTS: Question-specific targeted literature reviews informed the development of 24 candidate statements. The 17-member expert panel completed the Delphi process after 2 voting rounds, yielding 23 final recommendations: 2 on the definitions of intracranial atherosclerotic disease (ICAD) and ICAS (≥50% luminal narrowing); 2 on the definitions of symptomatic and asymptomatic ICAS; 12 on the diagnostic evaluation of ICAS; 2 on the use of transcranial Doppler ultrasound for the screening of intracranial stenosis; 3 on stenosis quantification and severity classification; and 2 on the advanced and investigational assessment of intracranial atherosclerosis.

CONCLUSION: These consensus recommendations provide a standardized framework for the definitions, diagnosis, and imaging of ICAS, intended to guide and align research and clinical practice across Asia whilst laying the foundation for future international standardization. Periodic review and refinement will be needed in response to emerging evidence, advances in diagnostic technologies, and increasing access to these modalities across healthcare settings.