Statistical Analysis Plan For Endovascular Treatment For Mild Ischemic Stroke Caused By Acute Anterior Circulation Large Vessel Occlusion: A Multicenter Prospective Randomized ControlledClinical Trial(MILD-MT)

Background: Acute ischaemic stroke (AIS) with a National Institutes of Health Stroke Scale (NIHSS) score <6 is termed as mild stroke. The benefit of endovascular therapy (EVT) for patients with mild stroke caused by large vessel occlusion (LVO) is uncertain. Aim and design: MILD- MT trial is a multicentre, prospective, randomised, open- label, blinded endpoint (PROBE) trial designed to evaluate whether EVT combined with best medical management (EVT+BMM) is superior to BMM alone in patients with mild stroke due to anterior circulation LVO. Eligible patients have confirmed intracranial carotid artery (ICA), middle cerebral artery (MCA M1/M2) segment with or without ipsilateral extracranial ICA occlusion, symptom onset within 24 hours, small core infarct (≤50 mL), and substantial perfusion mismatch (≥50 mL), a profile indicating high risk for early neurological deterioration. Sample size: Aim to randomise 300 patients 1:1 to receive EVT+BMM (intervention) or BMM alone (control). Study outcomes: The primary efficacy outcome is the proportion of excellent functional outcomes (defined as modified Rankin Scale 0 or 1 score) at 90±7 days. The primary safety outcomes include symptomatic intracranial haemorrhage within 48 hours according to the Heidelberg criteria; END is defined as an increase in NIHSS score ≥4 or ≥2 in any individual item within 7 days after randomisation and all- cause mortality at 90±7 days. Discussion: The MILD- MT trial could result in substantial evidence regarding the efficacy and safety of EVT for mild patients with AIS- LVO and large salvageable volume within 24 hours from symptom onset.