Background and PurposeCT perfusion (CTP) imaging is now widely used to select patients with large vessel occlusions for mechanical thrombectomy. Ghost infarct core (GIC) phenomenon has been coined to describe CTP core overestimation and has been investigated in several retrospective studies. Our aim is to review the frequency, magnitude, and variables associated with this phenomenon.MethodsA primary literature search resulted in eight studies documenting median time from symptom onset to CTP, median estimated core size, median final infarct volume, median core overestimation of the GIC population, recanalization rates, good outcomes, and collateral status for this systematic review.ResultsAll the studies investigated patients who underwent CTP within 6 hours of symptom onset, ranging from median times of 105 to 309 minutes. The frequency of core overestimation varied from 6% to 58.4%, while the median estimated ischemic core and final infarction volume ranged from 7 to 27 mL and 12 to 31 mL, respectively. The median core overestimation ranged from 3.6 to 30 mL with upper quartile ranges up to 58 mL. GIC was found to be a highly time‐and‐collateral‐dependent process that increases in frequency and magnitude as the time from symptom onset to imaging decreases and in the presence of poor collaterals.ConclusionsCTP ischemic core overestimation appears to be a relatively common phenomenon that is most frequent in patients with poor collaterals imaged within the acute time window. Early perfusion imaging should be interpreted with caution to prevent the inadvertent exclusion of patients from highly effective reperfusion therapies.

Background and Purpose: The relationship between the degree and location of vertebrobasilar stenosis and QMRA distal-flow status is uncertain. Our aim was to investigate the relationship between QMRA distal-flow status with degree and location of vertebrobasilar stenosis. <break><break> Methods: We retrospectively reviewed patients who presented with acute ischemic stroke, had neurovascular imaging demonstrating 50% stenosis of extracranial or intracranial vertebral or basilar arteries, and QMRA performed within one year of stroke, between 2009 and 2021. Standardized methods were used to measure the degree of stenosis and to dichotomize vertebrobasilar distal-flow status. Patients were grouped based on the involved artery and the location and severity of disease. P-values were calculated using chi-squared analysis and Fisher exact test with statistical significance defined as p <0.05.<break> <break> Results: Sixty-nine patients met study inclusion, consisting of 31 with low distal-flow and 38 with normal distal-flow states. Low distal-flow states were found exclusively in patients with severe stenosis or occlusion; however, severe stenosis or occlusion was poorly predictive of distal-flow status as nearly half of these patients had normal flow states (47%). Bilateral vertebral disease was significantly associated with low distal-flow states compared to patients with unilateral vertebral (70.8% versus 14.3%; p = 0.01), isolated basilar (70.8% versus 28.6%; p = 0.01), or mixed (71.4% versus 47.1%; p = 0.01) disease.<break> <break> Conclusions: Severe stenosis of 70% may mark the minimal threshold required to cause hemodynamic insufficiency in the posterior circulation, but nearly half of these patients may remain hemodynamically sufficient. The presence of bilateral vertebral stenosis resulted in a five-fold increase in the probability of QMRA low distal-flow status compared to unilateral vertebral disease. Our findings may have implications for the design of future treatment trials of endovascular versus medical management that may use hemodynamic markers as inclusion criteria.

Introduction The relationship between the degree of vertebrobasilar stenosis and QMRA distal‐flow status is uncertain. Our aim was to investigate this relationship. Methods We retrospectively reviewed patients who presented with acute ischemic stroke, had neurovascular imaging demonstrating ≥ 50% stenosis of extracranial or intracranial vertebral or basilar arteries, and QMRA within one year of stroke, between 2009 and 2021 at two institutions. The WASID and CAVATAS methods were used to measure the degree of intracranial and extracranial vertebrobasilar stenosis, respectively. Patients were grouped as: high‐grade (≥ 70% stenosis) in (1) one vertebral artery; (2) two vertebral arteries; or (3) basilar artery; and (4) moderate grade (≤70% stenosis) in either intracranial vertebral and basilar arteries or exclusive extracranial vertebral stenosis or occlusion. QMRA distal‐flow status was used to dichotomize patients into low‐flow and normal‐flow states based on VERiTAS criteria. P‐values were calculated using chi‐squared analysis and Fisher exact test with statistical significance defined as p < 0.05. Results Of the 303 patients undergoing QMRA for vertebrobasilar disease, 69 met study inclusion, consisting of 31 patients with low‐flow and 38 patients with normal‐flow states. High‐grade stenosis was most commonly found in one vertebral artery (34.8%), followed by both vertebral arteries (29.0%), and the basilar artery (27.5%), and moderate stenosis or exclusive extracranial disease made up 21.7% of patients. High‐grade stenosis in at least one vertebral or basilar artery was significantly associated with low‐flow states compared to patients with moderate‐grade stenosis or exclusive extracranial disease (53.7% versus 13.3%, p = 0.007). High‐grade stenosis in both vertebral arteries was significantly more likely to result in a low‐flow state compared to high‐grade stenosis in one vertebral artery (75.0% versus 41.7%, p = 0.001) or to high‐grade stenosis in the basilar artery (75.0% versus 42.1%, p = 0.040). Conclusions Low distal flow status on QMRA is strongly associated with high‐grade intracranial stenosis compared to moderate‐grade or exclusive extracranial stenosis and is nearly twice as frequent with high‐grade intracranial stenosis of both vertebral arteries compared to one. The location, degree of stenosis, and distal‐flow status should be considered as possible entry points for future prospective treatment trials in intracranial atherosclerotic disease.

Background and Purpose We aimed to investigate the relationship between the degree and location of vertebrobasilar stenosis and quantitative magnetic resonance angiography (QMRA) distal flow. Methods We retrospectively reviewed patients who presented with acute ischemic stroke with ≥50% stenosis of the extracranial or intracranial vertebral or basilar arteries, and QMRA performed within 1 year of stroke. Standardized techniques were used to measure stenosis and to dichotomize vertebrobasilar distal flow status. Patients were grouped based on the involved artery and the severity of disease. All p‐values were calculated using chi‐squared analysis and Fisher exact test with statistical significance defined as p < .05. Results Sixty‐nine patients met study inclusion, consisting of 31 with low distal flow and 38 with normal distal flow. The presence of severe stenosis or occlusion was 100% sensitive, but only 47% predictive and 26% specific of a low distal flow state. Bilateral vertebral disease was only 55% sensitive but was 71% predictive and 82% specific of a low‐flow state and was five times and nearly three times more likely to result in a low‐flow state compared to unilateral vertebral disease (14%) and isolated basilar disease (28%), respectively. Conclusions Severe stenosis of ≥70% may mark the minimal threshold required to cause hemodynamic insufficiency in the posterior circulation, but nearly half of these patients may remain hemodynamically sufficient. Bilateral vertebral stenosis resulted in a fivefold increase in QMRA low distal flow status compared to unilateral vertebral disease. These results may have implications in the design of future treatment trials of intracranial atherosclerotic disease.