Imaging in Acute Anterior Circulation Ischemic Stroke: Current and Future

Clinical trials on acute ischemic stroke have demonstrated the clinical effectiveness of revascularization treatments within an appropriate time window after stroke onset: intravenous thrombolysis (NINDS and ECASS-III) through the administration of tissue plasminogen activator within a 4.5-hour time window, endovascular thrombectomy (ESCAPE, REVASCAT, SWIFT-PRIME, MR CLEAN, EXTEND-IA) within a 6-hour time window, and extending the treatment time window up to 24 hours for endovascular thrombectomy (DAWN and DEFUSE 3). However, a substantial number of patients in these trials were ineligible for revascularization treatment, and treatments of some patients were considerably futile or sometimes dangerous in the clinical trials. Guidelines for the early management of patients with acute ischemic stroke have evolved to accept revascularization treatment as standard and include eligibility criteria for the treatment. Imaging has been crucial in selecting eligible patients for revascularization treatment in guidelines and clinical trials. Stroke specialists should know imaging criteria for revascularization treatment. Stroke imaging studies have demonstrated imaging roles in acute ischemic stroke management as follows: 1) exclusion of hemorrhage and stroke mimic disease, 2) assessment of salvageable brain, 3) localization of the site of vascular occlusion and thrombus, 4) estimation of collateral circulation, and 5) prediction of acute ischemic stroke expecting hemorrhagic transformation. Here, we review imaging methods and criteria to select eligible patients for revascularization treatment in acute anterior circulation stroke, focus on 2019 guidelines from the American Heart Association/American Stroke Association, and discuss the future direction of imaging-based patient selection to improve treatment effects

Long-term outcome of vertebral artery origin stenosis in patients with acute ischemic stroke

BACKGROUND: Vertebral artery origin (VAO) stenosis is occasionally observed in patients who have acute ischemic stroke. We investigated the long-term outcomes and clinical significance of VAO stenosis in patients with acute ischemic stroke. METHODS: We performed a prospective observational study using a single stroke center registry to investigate the risk of recurrent stroke and vascular outcomes in patients with acute ischemic stroke and VAO stenosis. To relate the clinical significance of VAO stenosis to the vascular territory of the index stroke, patients were classified into an asymptomatic VAO stenosis group and a symptomatic VAO stenosis group. RESULTS: Of the 774 patients who had acute ischemic stroke, 149 (19.3%) of them had more than 50% stenosis of the VAO. During 309 patient-years of follow-up (mean, 2.3 years), there were 7 ischemic strokes, 6 hemorrhagic strokes, and 2 unknown strokes. The annual event rates were 0.97% for posterior circulation ischemic stroke, 4.86% for all stroke, and 6.80% for the composite cardiovascular outcome. The annual event rate for ischemic stroke in the posterior circulation was significantly higher in patients who had symptomatic VAO stenosis than in patients who had asymptomatic stenosis (1.88% vs. 0%, p = 0.046). In a multivariate analysis, the hazard ratio, per one point increase of the Essen Stroke Risk Score (ESRS) for the composite cardiovascular outcome, was 1.46 (95% CI, 1.02-2.08, p = 0.036). CONCLUSIONS: Long-term outcomes of more than 50% stenosis of the VAO in patients with acute ischemic stroke were generally favorable. Additionally, ESRS was a predictor for the composite cardiovascular outcome. Asymptomatic VAO stenosis may not be a specific risk factor for recurrent ischemic stroke in the posterior circulation. However, VAO stenosis may require more clinical attention as a potential source of recurrent stroke when VAO stenosis is observed in patients who have concurrent ischemic stroke in the posterior circulation

Traumatic Entrapment of the Vertebrobasilar Junction Due to a Longitudinal Clival Fracture: A Case Report

Vertebrobasilar junction entrapment due to a clivus fracture is a rare clinical observation. The present case report describes a 54-yr-old man who sustained a major craniofacial injury. The patient displayed a stuporous mental state (Glasgow Coma Scale [GCS]=8) and left hemiparesis (Grade 3). The initial computed tomography (CT) scan revealed a right subdural hemorrhage in the frontotemporal region, with a midline shift and longitudinal clival fracture. A decompressive craniectomy with removal of the hematoma was performed. Two days after surgery, a follow-up CT scan showed cerebellar and brain stem infarction, and a CT angiogram revealed occlusion of the left vertebral artery and entrapment of vertebrobasilar junction by the clival fracture. A decompressive suboccipital craniectomy was performed and the patient gradually recovered. This appears to be a rare case of traumatic vertebrobasilar junction entrapment due to a longitudinal clival fracture, including a cerebellar infarction caused by a left vertebral artery occlusion. A literature review is provided

Assessment of Tissue Viability Using Diffusion- and Perfusion-Weighted MRI in Hyperacute Stroke

OBJECTIVE: The aim of this study was to investigate the relationship between the diffusion and perfusion parameters in hyperacute infarction, and we wanted to determine the viability threshold for the ischemic penumbra using diffusion- and perfusion-weighted imaging (DWI and PWI, respectively). MATERIALS AND METHODS: Both DWI and PWI were performed within six hours from the onset of symptoms for 12 patients who had suffered from acute stroke. Three regions of interest (ROIs) were identified: ROI 1 was the initial lesion on DWI; ROI 2 was the DWI/PWI mismatch area (the penumbra) that progressed onward to the infarct; and ROI 3 was the mismatch area that recovered to normal on the follow-up scans. The ratios of apparent diffusion coefficient (ADC), the relative cerebral blood volume (rCBV), and the time to peak (TTP) were calculated as the lesions' ROIs divided by the contralateral mirror ROIs, and these values were then correlated with each other. The viability threshold was determined by using the receiver operating characteristic (ROC) curves. RESULTS: For all three ROIs, the ADC ratios had significant linear correlation with the TTP ratios (p < 0.001), but not with the rCBV ratios (p = 0.280). There was no significant difference for the ADC and rCBV ratios within the ROIs. The mean TTP ratio/TTP delay between the penumbras' two ROIs showed a significant statistical difference (p < 0.001). The cutoff value between ROI 2 and ROI 3, as the viability threshold, was a TTP ratio of 1.29 (with a sensitivity and specificity of 86% and 73%, respectively) and a TTP delay of 7.8 sec (with a sensitivity and specificity of 84% and 72%, respectively). CONCLUSION: Determining the viability thresholds for the TTP ratio/delay on the PWI may be helpful for selecting those patients who would benefit from the various therapeutic interventions that can be used during the acute phase of ischemic stroke