In acute ischemic stroke, achievement of reperfusion as soon as possible by recanalizing the occluded intracranial vessels is the most important priority.4)10)14) However, intravenous infusion of recombinant tissue plasminogen activator (rTPA) has a relatively tight time limit and rates of recanalization are unsatisfactory.13) Several intra-arterial methods have been introduced and recent studies have shown that mechanical thrombectomy can extend the time limit and make earlier and better recanalization possible.2)3)6)9)11)12) Among thrombectomy techniques, there is a method using the fully retrievable, self-expanding Solitaire stent (ev3 Inc., Irvine, CA) which was initially used in stent-assisted embolization of intracranial aneurysms. Relatively quick and safe performance of thrombectomy using this stent, with satisfactory recanalization rates, has been documented.1)7)8)

In this report, we analyzed the clinical and radiological outcomes of mechanical thrombectomy using the Solitaire AB stent (the Solitaire thrombectomy) in 40 patients with acute occlusion of intracranial arteries.

Forty consecutive patients with acute intracranial artery occlusion underwent Solitaire thrombectomy in our department. Patients' data were collected from October 2010 through November 2011. Neurological evaluation (as per the National Institutes of Health Stroke Scale [NIHSS]) was performed before and after the procedure and at the time of discharge. Assessment of the modified Rankin Scale (mRS) was performed 90 days after treatment. The mRS of 0 to 2 was defined as a good neurological outcome and poor outcome was assumed when the mRS score was 3 to 6.

In order to rule out hemorrhagic stroke, all patients underwent evaluation with brain computed tomography (CT) on arrival. Then, magnetic resonance (MR) imaging with diffusion-weighted imaging (DWI), MR angiography, and perfusion-weighted imaging (PWI) was performed for assessment of occluded vessels and DWI-PWI mismatch. After the thrombectomy procedure, brain CT was performed routinely in order to rule out intracerebral hemorrhage (ICH). MR angiography with DWI was acquired 24 to 36 hours after the procedure. In one patient, these were replaced with brain CT and brain CT angiography because of his pacemaker.

The main inclusion criteria were (1) NIHSS score ≥ 8; (2) Thrombolysis in cerebral infarction (TICI) score of 0 to 1 in an accessible vessel; (3) DWI-PWI mismatch and no detection of ICH; and (4) arrival at the hospital within six hours of symptom onset. When intracranial artery occlusion was found on MR angiography, treatment with intravenous rTPA (0.9 mg/kg body weight) was started if symptom onset was within three hours. Patients who were refractory or ineligible for use of intravenous rTPA were then transferred to the angiosuite for treatment with Solitaire thrombectomy.

All of the procedures were performed under local anesthesia by an endovascular neurosurgeon. When the patient required sedation (three out of 40), intravenous midazolam (Bukwang Pharm, Seoul, Korea) was administered. First, angiograms of the normal vessels were obtained for evaluation of the degree of leptomeningeal collaterals to the ischemic area. Then, the occlusion status and TICI scale of the occluded vessel were confirmed by taking angiography after locating the 7F or 8F guiding catheter (Guider XF Softip™, Boston Scientific, Plymouth, MN) to the proximal internal carotid artery (ICA) or vertebral artery (VA). To prevent occurrence of a new thromboembolic event during the procedure, a mixture of 2,000 IU of heparin and 0.9% normal saline 1,000 ml was administered continuously through the guiding catheter. Next, the microcatheter (Prowler SELECT™ PLUS, Codman Neurovascular, Raynham, MA) and microwire (Synchro™-14, Stryker Neurovascular, Fremont, CA) were introduced into the target vessel and located at the distal portion of the occlusion site after passing the thrombus segment. Then, the microwire was removed and the total length of the thrombus was confirmed by manual injection of contrast through the microcatheter while withdrawing it or simultaneous injection of contrast through the microcatheter and guiding catheter before the withdrawal under roadmap condition (Fig. 1). The Solitaire stent was introduced into the microcatheter so that the device could be deployed to completely cover the occlusion segment. Deployment of the stent was maintained for at least two minutes before retrieval. The microcatheter and stent were gently withdrawn and the guiding catheter was pulled out of the sheath with the stent in it and the flushing was stopped. At the same time, an assistant applied negative pressure using a 50 cc syringe through the guiding catheter to prevent development of a new embolism by lost clots. When the subsequent angiogram showed a TICI score < 2, the procedure was repeated until a TICI score of ≥ 2 or 3 was achieved.

In this study, male was slightly dominant (65%), 18 (45%) patients had atrial fibrillation, and the proximal middle cerebral artery was the most common site of occlusion (55%). Intravenous rTPA was administered to 17 patients (Table 1). Of the 40 patients, revascularization was achieved in 36 (90%) (TICI grades 2a/2b and 3). The mean initial NIHSS score was 14.1 (range, 8-26), and the mean NIHSS score was 11.6 (range, 1-23) at 24 hours after the procedure. In 13 patients (32.5%), NIHSS scores showed improvement of more than 10 or were 0-1 at the time of discharge. At 90 days, 42.5% (17 of 40) of patients showed a good neurological outcome (mRS 0-2) (Table 2). The average time from symptom onset to groin puncture and groin puncture to recanalization were 215.8 minutes (range, 60-417 minutes) and 85.3 minutes (range, 8-160 minutes) respectively. The average number of times of thrombectomy up to maximal recanalization was 2.9 (range, 1-9); one thrombectomy in 15 cases (37.5%), while more than two in 21 cases (62.5%) in cases of successful recanalization (Table 3).

In one case, new occlusion occurred during withdrawal of the stent by migrated emboli but showed near complete resolution after infusion of 250,000 IU of urokinase (Fig. 2) and post-procedural ICH, which was asymptomatic, occurred in only one case (2.5%). There was no occurrence of technical failure or procedure-related complications such as arterial rupture or dissection, groin complication requiring surgery, or blood transfusion. However, there were two cases of stent breakage. Three patients underwent decompressive craniectomy for aggravated brain edema. Two (5%) patients who died after aggravation of brain swelling had refused to undergo further treatment, such as decompressive craniectomy.

These initial results suggest that a self-expanding and fully retrievable Solitaire stent may be a safe and efficient tool for recanalization of acute ischemic stroke due to intracerebral artery occlusion that was refractory or ineligible for use of intravenous tissue plasminogen activator.