Our main hypothesis is that acute EVT associated with best medical treatment is superior to best medical treatment alone, for improving clinical outcomes at 90 days, in patients with mild or severe acute ischemique stroke and diffusion-perfusion or clinical-imaging mismatch, secondary to CICAO.

The primary objective of this study is to demonstrate the superiority of endovascular therapy (EVT) associated with best medical therapy (BMT) (experimental arm) compared to BMT alone (control arm) to increase the functional independence at day 90 3 months (mRS 0-2) in patients with acute cervical isolated internal carotid artery occlusion (CICAO), mild to severe stroke (NIHSS score > 5), and core-perfusion or clinical-imaging mismatch.

Secondary objectives are,(i) to compare the safety of EVT + BMT vs. BMT alone in patients with AIS secondary to CICAO and core-perfusion of clinical imaging mismatch; (ii) to demonstrate the superiority of EVT + BMT vs BMT alone on : the rate of excellent outcome at 3 months (modified Rankin Scale, mRS, score = 0-1),the decrease of the 90-day degree of disability (shift on the mRS combining scores of 5 and 6), the rate of carotid recanalization at 24 hours and at day 90 post-randomization, the cerebral infarct size at 24 hours and at day 90 post-randomization, the early neurological deterioration rate at 24 hours and at day 5- 7 post-randomization, the ischemic recurrences rate at day 90 post-randomization, the early neurological improvement rate at 24h hours post-randomization, the cognitive impairment rate at day 90 post-randomization, the Quality of life at day 90 post-randomization.

One of the secondary objective is also to describe in the experimental group (EVT + BMT), the procedure-related adverse events at day 90 ((Embolism to an intracranial artery, vascular perforation, arterial dissection, access site complication requiring surgical repair or blood transfusion, peri-procedural mortality, device failure).

Inclusion Criteria:

• ≥18-year-old patients (no upper age limit)
• Clinical signs consistent with AIS (Acute ischemic stroke)
• NIHSS score >5 at randomization time with time from last seen well to randomization ≤23h, or fluctuating neurological symptoms, defined as recurrent transient attacks and/or progression of neurological deficit within the last 7 days.
• Ischemic stroke confirmed by cerebral imaging (CT: Computed Tomography or MRI:Magnetic Resonance Imaging) or normal imaging with suspected ischemic stroke
• Existence of a mismatch: If perfusion data are available (PWI/CTP), existence of a core-perfusion mismatch, suggestive of carotid hemodynamic mechanism, according to the DEFUSE-3 criteria: mismatch volume ≥15 mL, core volume ≤70 mL, and mismatch ratio ≥1.8 ; if perfusion data are not available, or non interpretable, existence of a clinical-imaging mismatch, defined by an ASPECTS >5 (Alberta Stroke Program Early CT score)
• CICAO (Cervical isolated Internal Carotid Artery Occlusion) all causes (for example dissection, atheroma or undetermined cause) on CTA (Computed Tomography Angiography) or MRA with gadolinium, without associated visible ipsilateral large intracranial occlusion (T or L, M1, M2, A1, A2, P1, P2), <1 h before randomization
• Anticipated possibility to start the EVT procedure (arterial access) within 60 minutes after randomization
• Pre-stroke mRS score ≤2
• Patient or patient's representative has received information about the study and has signed and dated the appropriate Informed Consent or met the criteria for emergency consent, signed by the investigator

Exclusion Criteria:

• CICAO after recent (<1 month) endarterectomy
• Patient with severe or fatal co-morbidities or life expectancy <6 months that will likely interfere with improvement or follow-up or that will render the procedure unlikely to benefit the patient
• Patient unable to come or unavailable for follow-up
• Pre-existing neurological or psychiatric disease that would confound the neurological or functional evaluations
• Seizures at stroke onset if they make the diagnosis of stroke doubtful and preclude obtaining an accurate baseline NIHSS assessment
• Suspected cerebral vascular disease (e.g., vasculitis) based on the medical history and CTA/MRA
• Pregnancy in progress or planned during the study period, woman who is known to be pregnant or lactating at admission time
• Adult protected by law or patient under guardianship or curators
• Current participation in another investigational drug or device study
• Not affiliated to the French social security system or not beneficiary of such system
• Known contrast or endovascular product life-threatening allergy
• Associated stenosis (≥50%) of the middle cerebral artery ipsilateral to the CICAO
• Chronic CICAO, defined as a known carotid occlusion (on a previous imaging exam) ≥30 days before randomization or high suspicion of chronic CICAO based on medical history and CT/MRI
• Tandem occlusion, defined by cervical ICA occlusion associated with intracranial large vessel occlusion (T- or L-shaped, M1 or M2 portions of the middle cerebral artery, A1 or A2 portions of the anterior cerebral artery, P1 or P2 portions of the posterior cerebral artery)
• Associated ipsilateral large intracranial arterial occlusion
• Prior stenting of the target ICA
• Intracranial stent implanted in the same vascular territory as the CICAO
• Sub-occlusive cervical ICA stenosis on CTA or MRA
• Suspicion of ICA occlusion starting at the petrous, cavernous or intracranial segment with normal cervical portion on non-invasive imaging (MRA or/and CTA)
• Known absence of vascular access
• Suspicion of aortic dissection based on medical history, clinical evaluation or/and imaging
• Sub-occlusive cervical ICA stenosis on CTA or MRA
• Common carotid artery occlusion without ICA occlusion on non-invasive imaging (MRA or/and CTA)
• Evidence of intracranial hemorrhage on CT/MRI.

As the therapeutic arm is interventional in the experimental arm, the physicians in charge of the patient and the patients cannot be blinded.

The mRS score will be evaluated by qualified assessors blinded to the initial treatment