The primary hypothesis being tested in this trial is that acute ischemic stroke with isolated internal carotid artery occlusion will have improved clinical outcomes when given early endovascular treatment compared with that of given best medical treatment.

Stroke is the leading cause of death and disability among Chinese residents, and ischemic stroke accounts for 70-80% of all strokes. Isolated internal carotid artery occlusion (iICAO) refers to occlusion of the internal carotid artery, which is not involve the circle of Willis, the M1 and the proximal M2 segment of the middle cerebral artery. IICAO accounts for about 20-25% of symptomatic acute internal carotid artery occlusion. Previous studies have shown that despite the best medical treatment, including intravenous thrombolysis, the early recanalization rate of patients with acute iICAO is only 4.4%-23%, and less than half of the patients eventually achieve self-care. Endovascular Treatment (EVT) is the most effective reperfusion therapy for large vessel occlusive stroke. Since only a few retrospective studies have reported the efficacy and safety of early EVT in patients with acute iICAO stroke, there is a lack of high-level prospective evidence so far. Therefore, the aim of this study is to conduct a prospective, multicenter, open-label, randomized controlled clinical trial to evaluate the efficacy and safety of early EVT in patients with acute iICAO stroke.

Inclusion Criteria:

1. Age ≥18.
2. Clinical signs consistent with an acute ischemic stroke and randomization no later than 23 hours after the time last known to be well.
3. CTP, CTA or enhanced MRA within 1 hour before randomization showed that the offending vessel was isolated internal carotid artery occlusion, namely occlusion of C1-C6 segments (according to Bouthillier's segmentation) at any location. There was no ipsilateral intracranial branch occlusion (T or L shape of internal carotid artery, M1 or M2 segment of middle cerebral artery, A1 or A2 segment of anterior cerebral artery, P1 or P2 segment of posterior cerebral artery).
4. Neurological deficit with a NIHSS of >5, or ≤5 points with disabling symptoms (complete hemianopsia, severe aphasia, neglect, any limb weakness that cannot sustain resistance to gravity, and functional loss that is considered by doctors and patients to be potentially disabling by clinical evaluation).
5. Mismatch: target Mismatch Profile on CT perfusion or MRI (ischemic core volume is < 70 ml, mismatch ratio is ≥1.8 and mismatch volume is ≥15 ml); clinical-imaging mismatch defined as an ASPECTS score of more than 5, was present if perfusion data were not available or imaging quality was poor enough to be interpreted.
6. mRS Score before stroke ≤2.
7. Patient/Legally Authorized Representative has signed the Informed Consent form.

Exclusion Criteria:

1. The patient underwent carotid endarterectomy within 1 month.
2. Severe comorbid condition with life expectancy less than 6 months at baseline.
3. Other suspected cerebrovascular diseases (vasculitis, untreated cerebrovascular malformation, intracranial aneurysm, etc.) based on history and CTA/MRA.
4. Women who are pregnant or planning to become pregnant at the time of the study and who are known to be pregnant or breastfeeding at the time of admission.
5. Known life-threatening allergic reactions to contrast media or intravascular products.
6. Chronic internal carotid artery occlusion, defined as known carotid artery occlusion (imaging examination) ≥30 days before randomization or highly suspected chronic internal carotid artery occlusion based on medical history and CT/MRI.
7. Tandem occlusion, which was defined as internal carotid artery occlusion combined with large intracranial vessel occlusion (T or L shape of internal carotid artery, M1 or M2 segment of middle cerebral artery, A1 or A2 segment of anterior cerebral artery, P1 or P2 segment of posterior cerebral artery).
8. No known vascular access.
9. Suspected aortic dissection based on medical history, clinical evaluation or/and imaging.
10. Evidence of intracranial hemorrhage on CT/MRI.
11. Patient unable to come or unavailable for follow-up.
12. Pre-existing neurological or psychiatric disease that would confound the neurological or functional evaluations.
13. Seizures at stroke onset if they make the diagnosis of stroke doubtful and preclude obtaining an accurate baseline NIHSS assessment.
14. Patients have contraindications to the use of heparin and antiplatelet drugs.