Early Identification and Diagnosis of BAD-related Stroke

Branch atheromatous disease (BAD)-related stroke is an important subtype of acute ischemic stroke involving penetrating arteries and is associated with early neurological deterioration. Early recognition and standardized diagnosis remain challenging in routine clinical practice because clinical symptoms are often non-specific and the diagnosis requires integrated clinical and imaging assessment. This multicenter prospective observational study will collect demographic, clinical, laboratory, electrocardiographic, ultrasound, and multimodal neuroimaging data from adults with acute ischemic stroke within 1 week of symptom onset. Participants will receive routine clinical care determined by their treating physicians; no treatment or management strategy will be assigned by the study protocol. An independent central clinical-imaging adjudication committee will classify participants as BAD-related stroke or non-BAD acute ischemic stroke according to predefined diagnostic criteria. The study aims to develop and externally validate artificial intelligence-assisted screening and diagnostic models for BAD-related stroke and to evaluate their discrimination, calibration, and potential clinical utility.

Inclusion Criteria: * Age 18 to 80 years. * Diagnosis of acute ischemic stroke. * Time from symptom onset to enrollment ≤ 1 week; if the onset time is unknown, time from last known well to enrollment ≤ 1 week. * Availability of required baseline clinical and neuroimaging assessments according to the study protocol. * Written informed consent provided by the participant or legally authorized representative. Participants will be classified into the BAD-related stroke cohort if they meet all predefined BAD-related stroke diagnostic criteria, including: * A single isolated deep subcortical infarct on diffusion-weighted imaging. * The presumed culprit perforating artery is the lenticulostriate artery or the paramedian pontine artery. * For lenticulostriate artery territory infarction: a comma-shaped lesion extending from inferior to superior direction on coronal DWI or involvement of ≥3 axial DWI slices with 5-7 mm slice thickness. * For paramedian pontine artery territory infarction: a lesion extending from the deep pons to the ventral surface of the pons on axial DWI. * No ≥50% stenosis of the corresponding parent artery, confirmed by MRA, CTA, or DSA. Participants with acute ischemic stroke who do not meet BAD-related stroke criteria will be classified into the non-BAD acute ischemic stroke cohort. Exclusion Criteria: General exclusion criteria for all participants: * Intracranial hemorrhage, vascular malformation, aneurysm, brain abscess, malignant intracranial mass, or other non-ischemic intracranial lesion on baseline CT, MRI, MRA, CTA, or DSA. * Pre-stroke modified Rankin Scale score ≥2. * Life expectancy ≤6 months. * Unable to tolerate MRI examination. * Pregnancy or breastfeeding. * Participation in another clinical study within 3 months before informed consent or current participation in another clinical study that may interfere with this study. Additional criteria that preclude classification as BAD-related stroke: * Ipsilateral extracranial tandem artery stenosis ≥50%. * Definite cardioembolic source, including atrial fibrillation, myocardial infarction, clinically significant valvular heart disease, dilated cardiomyopathy, infective endocarditis, atrioventricular conduction disease, or heart rate \