The implications of magnetic resonance angiography artifacts caused by different types of intracranial flow diverters.

BACKGROUND: Serial cerebral angiographic imaging is necessary to ensure cerebral aneurysm occlusion after flow diverter placement. Time-of-flight (TOF)-magnetic resonance angiography (MRA) is used for this purpose due to its lack of radiation, contrast media and complications. The comparative diagnostic yield of TOF-MRA for different flow diverters has not been previously analyzed. PURPOSE: To evaluate the diagnostic accuracy of TOF-MRA in cerebral aneurysms treated w divertersith different flow diverters. MATERIALS AND METHODS: Flow-diverted patients whose cerebral follow-up MRA and digital subtraction angiograms (DSA) were obtained within 6 weeks were retrospectively identified. The DSA (as gold standard) and MRA images of these patients were compared by two readers (blinded to both patient data and endovascular procedure data) for residual aneurysms and the status of the parent artery for each type of flow diverter. In a second group of patients, magnetic susceptibility artifacts were manually measured and compared for different FDs. RESULTS: Seventy-six patients (85 aneurysms) were included in group one, and 86 patients (95 aneurysms) were included in group 2. TOF-MRA and DSA showed almost perfect agreement for residual aneurysms (κ = 0.88, p < 0.001) (positive predictive value (PPV) = 1.00, specificity = 1.00, negative predictive value (NPV) = 0.89, sensitivity = 0.89). Intermodality agreement (κ = 0.97 vs. κ = 0.74, p < 0.005) and sensitivity (0.97 vs. 0.77, NPV: 0.96 vs. 0.77) were highest with nitinol stents. MRA and DSA showed no agreement for occluded or stenotic parent vessels (κ = 0.13, p = 0.015, specificity = 0.44, NPV = 1.00, sensitivity = 1.00). Specificity was lower in chromium-cobalt based FDs than in nitinol devices (specificity = 0.08 vs. 0.60). Chromium-cobalt stents generated the largest artifacts (p < 0.005). The size of the device-related artifact, in millimeters, increased in respective order, for the Silk, Derivo, Pipeline and Surpass devices. CONCLUSION: Unlike DSA, TOF-MRA is susceptible to dissimilarities between flow diverters. MRA is not well-suited for research studies comparing different flow diverters. Nitinol FDs appear to be advantageous for TOF-MRA follow-up so as not to miss small aneurysm remnants or clinically relevant parent artery stenosis.

Clinical challenges associated with the endovascular treatment of acute stroke in a patient with infective endocarditis

Although stroke is common in infective endocarditis (IE), only 26 cases of thrombectomy have been reported to date for IE-related acute stroke. We report a 40-year-old man who presented with left middle cerebral artery occlusion of unknown cause. Multiple attempts of mechanical aspiration thrombectomy and stentrievers failed to recanalize the artery. Effective revascularization was eventually achieved by placing a self-expanding intracranial stent. Post-procedurally the patient was diagnosed with IE with mitral valve insufficiency, mandating emergent valvular replacement while the patient was still on tirofiban infusion. On follow-up, the patient had a modified Rankin’s score of 0, had no recurrent stroke, and the intracranial stent remained patent yet stenosed. Based on the use of a self-expanding intracranial stent in the setting of IE, we discuss the consequences of the fibrotic and inflammatory content of the embolus and the associated high risk of intracranial hemorrhage which complicates clinical decision making.

Dual Mechanical Thrombectomy for Recanalization of a Resistant Acute Posterior Circulation Stroke

A 71-year-old man with acute basilar artery occlusion was referred for endovascular treatment 6 hours after the onset of stroke with a Glasgow Coma Score of 3 and National Institutes of Health Stroke Scale of 27. A cerebral arteriogram revealed occlusion of the left vertebral artery proximally and thromboembolic occlusion of the basilar tip. Direct aspiration and mechanical thrombectomy with various stent retrievers failed to reconstitute arterial flow in the basilar artery. Thrombolysis in cerebral infarction 2b recanalization was achieved only after placement of double Catch Mini stent retrievers through 2 microcatheters, on both side branches of the basilar bifurcation in a kissing fashion and retrieving them simultaneously. It was possible to perform this maneuver through a single distal access catheter without any complications. On follow-up the patient awakened and was able to follow commands on his right side. To our knowledge, dual mechanical thrombectomy with stent retrievers has not been reported in the posterior circulation previously. This technique may be useful in retrieving thrombi located at major intracranial bifurcations of the posterior circulation which do not recanalize with standard mechanical thrombectomy procedures. Although bilateral access to the basilar artery through both vertebral arteries is an advantage in posterior circulation for this technique, dual mechanical thrombectomy can also be performed through a unilateral access.

The WingSpan Stent System for the Treatment of Intracranial Atherosclerotic Stenoses: A Single Center Experience / 신경중재치료의학

PURPOSE: A self-expandable nitinol stent (WingSpan stent; Boston Scientific Corp.) was introduced for the treatment of intracranial stenoses. The purpose of this study is to present our initial experience with the WingSpan stent for the treatment of atherosclerotic stenoses of the cerebral arteries. MATERIALS AND METHODS: Consecutive 37 patients (mean age: 66.8 years, 17 men and 20 women) with symptomatic severe stenoses (>50%) of various anatomic sites were treated with WingSpan stent (BSC). Treatment result was evaluated in terms of technical success rate, intra-procedural event, and clinical course. Neurological morbidity and mortality rates were obtained. Arterial patency was evaluated with the 6 month follow-up angiography. Restenosis over 50% was regarded as significant. RESULTS: The technical success rate was 97.3% (36/37). Flow-limiting vasospasm or dissection after balloon angioplasty (n=3), misplacement of the stent (n=3), and acute in-stent thrombosis (n=1) were occurred. The initial stenosis before the procedure (71.7%) was improved after balloon angioplasty (39.8%) and after subsequent stent placement (20.0%). There were four neurological events during periprocedural period. Those were two TIA, one minor stroke, and one major stroke. The periprocedural morbidity rate was 5.4%. One mortality was the case of progression of previous brainstem infarction. Six-month-follow-up angiography was available in 16 patients and in-stent restenosis was noted in 7 (43.8%). CONCLUSION: WingSpan stents could be delivered to the target lesions without difficulty. However, the system showed technical problems such as misplacement. Restenosis seemed not infrequent on our limited follow-up observations.