Patients
We retrospectively reviewed all stroke patients with ICASS-related M1 occlusion who underwent EVT at our institution between January 2015 and December 2020. The inclusion criteria were as follows: (1) age ≥ 18 years, (2) isolated M1 occlusion confirmed by CTA or MRA, (3) acute symptom onset with a neurologic deficit in accordance with the occluded MCA territory, and (4) patients who underwent EVT and confirmed as ICASS-related occlusion. The exclusion criteria were as follows: (1) multiple vessel occlusions or tandem occlusions; (2) another stroke etiology such as dissection, moyamoya disease, or vasculitis; and (3) data (baseline or procedural or follow-up) were missing. Two experienced interventional neurologists assessed the surgical notes, medical charts, and radiologic images of the patients. Moreover, patients’ demographics (age and gender), risk factors (diabetes, hypertension, hyperlipidemia, atrial fibrillation, smoking, drinking, and previous stroke), clinical and imaging characteristics, perioperative complications, and immediate postoperative results were evaluated. An ICASS-related occlusion was defined as a degree of fixed stenosis > 70% after thrombectomy in the occlusion site, not sensitive to vasoactive substances, with impairment of perfusion of the dependent territory. This retrospective study was approved by the Institutional Review Board of 971 Hospital of PLA (LL20220608002).
Procedure details
For the patients with proven occlusion of the M1 segment within the time window of intravenous thrombolysis and without contraindications, they received standard care which started with intravenous alteplase (0.9 mg/kg) according to the guidelines, before undergoing EVT. Patients over 4.5 h were directly subjected to EVT. The physician and anesthetists decided the choice of anesthesia (local or general) on the patient’s consciousness status. Patients who treated with bridging EVT protocol received no heparin, while the others were administered with a low dose of heparinization. The treating physician selected the type of EVT procedure according to the angiographic result. An 8-F or 9-F guiding catheter was introduced into the internal carotid artery to provide stable support. The direct aspiration thrombectomy (Penumbra, Alameda, CA, USA), stent retrievers (Solitaire, Medtronic, Irvine, CA, USA; Trevo, Stryker Neurovascular, Fremont, CA, USA), or combinations were routinely performed. For patients with a degree of stenosis > 70% after thrombectomy, a vasodilator was injected through the guiding catheter for continuous irrigation, and repeat angiography was performed to exclude potential dissection or vasospasm after the first recanalization. If the stenosis persisted, an underlying ICASS was identified.
Once ICASS-related occlusion was identified, after the cone-beam CT showed no hemorrhage, a low dosage of tirofiban (glycoprotein IIb/IIIa inhibitor) was injected, and a rescue therapy strategy was applied. Then, intracranial angioplasty was performed with a Gateway balloon (Boston Scientific, Natick, MA, USA). The diameter of the balloon was adjusted to 80% of the normal vessel diameter, and the shortest length that would cover the entire lesion was chosen to minimize potential damage to lenticulostriate arteries in adjacent unaffected segments [10]. The repeat angiography was performed, and when stenosis persisted or reocclusion occurred, permanent stent (Solitaire; Enterprise, Codman, Raynham, MA, USA; or Neuroform, Stryker Neurovascular, Fremont, CA, USA) was deployed. All patients underwent CT scans immediately after procedure, and 24 h after, to detect any intracranial hemorrhage. When the patient’s neurological status deteriorated, a CT scan was immediately performed. If no intracranial hemorrhage was detected, tirofiban was continuously used in the patients with ICASS-related occlusion. Meanwhile, dual antiplatelet therapy with clopidogrel and aspirin (300 mg each) was administered and overlapped with tirofiban infusion 6 h before the cessation of tirofiban for these patients with stent deployment. And then, these patients were treated for 3 months with aspirin (100 mg/day) and clopidogrel (75 mg/day), followed by lifelong 100mg aspirin.
Clinical assessment and follow-up
Successful reperfusion was defined as modified Thrombolysis in Cerebral Infarction (mTICI) score of 2b–3 [11]. The National Institutes of Health Stroke Scale (NIHSS) was assessed by experienced neurosurgeons. Clinical outcome was assessed using the modified Rankin Scale (mRS) at 3-month follow-up at the clinic or by phone interview. The first angiographic follow-up was generally performed at 6 months using DSA and then MRA or DSA yearly thereafter. For the patients, underlying ICASS-related occlusion treated with intracranial angioplasty alone and the stenosis has improved significantly (degree of stenosis ≤ 50%); once patients were clinically and neurologically recovered from the acute phase after stroke (2 weeks), DSA was performed. If the stenotic segment was severe restenosis (degree of stenosis > 70%), stent deployment was scheduled Fig. 1.