Vertebrobasilar Stroke: Association Between Infarction Patterns and Quantitative Magnetic Resonance Angiography Flow State

Background

Treatment and prognosis of vertebrobasilar atherosclerotic disease differs depending on stroke mechanism, such as artery‐to‐artery embolism, branch atheromatous disease, and hemodynamic ischemia. Our aim was to investigate the relationship between infarction pattern and flow status using quantitative magnetic resonance angiography (QMRA), to determine the validity of using infarction patterns to infer stroke mechanism.

Methods and Results

This is a retrospective study of patients with ischemic stroke with intra‐ or extracranial vertebrobasilar atherosclerotic stenosis, who underwent magnetic resonance imaging of the brain, neurovascular imaging, and QMRA, between 2009 and 2021. Patients with cerebral infarction predating or following QMRA by ≥1 year, or QMRA studies performed for basilar thrombosis, vertebral dissection, or only postangioplasty/stenting, were excluded. Poststenotic flow (basilar and posterior cerebral arteries) was dichotomized as low‐flow or normal‐flow based on published criteria. Of 1211 consecutive patients who underwent QMRA noninvasive optimal analysis, 69 met inclusion. Mixed patterns were most common (46.4%), followed by perforator (23.2%), borderzone (14.5%), and territorial (15.9%). Patients with low‐flow had a significantly higher rate of borderzone+ patterns (borderzone alone or in mixed pattern) compared with patients with normal‐flow (77.4% low‐flow versus 39.5% normal‐flow, P=0.002). Borderzone+ patterns were associated with 61.5% probability of low‐flow state, while no borderzone (perforator/territorial) patterns were associated with 76.7% probability of normal‐flow state.

Conclusions

Borderzone infarction pattern (alone or mixed) was associated with low poststenotic posterior circulation flow by QMRA. However, borderzone pattern only moderately predicted low‐flow state, and may be an unreliable flow marker. Therefore, infarct topography may complement, but should not replace hemodynamic studies to establish flow status.

Intraplaque Enhancement Is Associated With Artery-to-Artery Embolism in Symptomatic Vertebrobasilar Atherosclerotic Diseases

Objective: There are limited data regarding the characteristics of intracranial plaques according to stroke mechanism in the posterior circulation. This study aims to compare whether the plaque characteristics and baseline features are different in patients with artery-to-artery (A-to-A) embolism and those with parent artery disease in the intracranial vertebrobasilar atherosclerotic disease.

Methods: From September 2014 to January 2017, patients with recent posterior circulation stroke due to intracranial vertebrobasilar atherosclerotic disease were retrospectively analyzed. Patients with the following eligibility criteria were included: (1) age ≥18 years old, (2) ischemic stroke in the vertebrobasilar territory, (3) 70–99% stenosis of the intracranial vertebral artery or basilar artery, and (4) two or more atherosclerotic risk factors. Patients with concomitant ipsilateral or bilateral extracranial vertebral artery >50% stenosis, cardio-embolism, or non-atherosclerotic stenosis were excluded. The plaque characteristics, including intraplaque compositions (intraplaque hemorrhage and intraplaque calcification), intraplaque enhancement, and remodeling index, were evaluated by using 3T high-resolution magnetic resonance imaging (HRMRI). The baseline features including vascular risk factors and the involved artery were collected. Patients were divided into A-to-A embolism and parent artery disease groups based on the diffusion-weighted images, T2-weighted images, or computed tomography. The plaque characteristics and baseline features were compared between the two groups.

Results: Among consecutive 298 patients, 51 patients were included. Twenty-nine patients had A-to-A embolism and 22 patients had parent artery disease. Compared with parent artery disease, the occurrence rates of intraplaque enhancement and intracranial vertebral involvement were higher in the A-to-A embolism group (79.3 vs. 36.4%; p = 0.002 and 62.1 vs. 18.2%; p = 0.002, respectively). Multivariable logistic regression analysis showed that intraplaque enhancement and intracranial vertebral artery plaques were also associated with A-to-A embolism (adjusted OR, 7.31; 95% CI 1.58–33.77; p = 0.011 and adjusted OR, 9.42; 95% CI 1.91–46.50; p = 0.006, respectively).

Conclusion: Intraplaque enhancement and intracranial vertebral artery plaques seem to be more closely associated with A-to-A embolism than parent artery disease in patients with symptomatic intracranial vertebrobasilar disease.

Clinical Trial Registration:http://www.clinicaltrials.gov, identifier: NCT02705599.

Relationship of brainstem infarction to rupture of nonsaccular vertebrobasilar aneurysms

OBJECTIVE

Symptomatic nonsaccular vertebrobasilar aneurysms (NSVBAs) are associated with high rates of aneurysm-related death. Anecdotal evidence suggests that brainstem infarction may be a harbinger of aneurysm rupture. The authors aimed to investigate the association between brainstem infarction and subsequent NSVBA rupture.

METHODS

The clinical records and radiographic imaging studies of patients presenting to the authors' institution between 1996 and 2019 for evaluation and management of an NSVBA were retrospectively reviewed to determine the effect of perforating artery infarction on the natural history of NSVBAs. Kaplan-Meier curves for patients with and patients without perforator infarction were constructed, and predictors of aneurysm rupture were identified using a multivariate Cox proportional hazards model.

RESULTS

There were 98 patients with 591.3 person-years of follow-up who met the inclusion criteria for analysis. There were 20 patients who experienced perforator infarction during follow-up. Ten patients (10.2%) experienced aneurysm rupture during follow-up and 26 patients (26.5%) died due to aneurysm-related complications, with annual rates of rupture and aneurysm-related death of 1.7% and 4.4%, respectively. Five patients with a perforator infarction later experienced aneurysm rupture, with a median time between infarction and rupture of 3 months (range 0-35 months). On multivariate analysis, the presence of intraaneurysmal thrombus (risk ratio [RR] 4.01, 95% confidence interval [CI] 1.12-14.44, p = 0.033) and perforator infarction (RR 6.37, 95% CI 1.07-37.95, p = 0.042) were independently associated with risk of aneurysm rupture.

CONCLUSIONS

NSVBAs continue to be extremely challenging clinical entities with a poor prognosis. These results suggest that brainstem infarction due to perforating artery occlusion may be a harbinger of near-term aneurysm rupture.

Perfusion-MRI is a Poor Indicator of Hemodynamic Compromise in Vertebrobasilar Disease in the VERiTAS Study

BACKGROUND AND PURPOSE

Dynamic susceptibility perfusion MR imaging (DSC MRP) has been used to assess changes in cerebral perfusion attributable to vascular stenosis or occlusion that may predict stroke risk. However, DSC MRP is not validated for identifying hemodynamic compromise in the posterior circulation. We investigated the clinical utility of DSC MRP in vertebrobasilar (VB) atherosclerotic disease in the observational VERiTAS study.

METHODS

VERiTAS enrolled patients with symptomatic ≥50% VB stenosis/occlusion. Posterior circulation hemodynamic status was designated as low or normal based on large vessel flow measured using quantitative magnetic resonance angiography (QMRA) and was predictive of future stroke risk. In this study, DSC MRP conducted concurrently with QMRA was used to evaluate posterior circulation perfusion. The primary outcome was the mean transit time (MTT) and relative cerebral blood volume (rCBV) in the posterior circulation normalized to the anterior circulation, compared between patients with low and normal blood flow as determined on QMRA.

RESULTS

Twenty-six subjects had 47 DSC MRP studies for review. There was no statistically or clinically significant difference in the rCBV ratio (1.02 vs. .96 P = .89), or MTT ratio (1.04 vs. 1.04 P = .96) relative to normal or low VB territory flow.

CONCLUSIONS

In this study, we did not find that DSC MRP adequately distinguished between patients with low or normal flow status based on large-vessel flow measurements.

Vertebral Artery Stenoses Contribute to the Development of Diffuse Plaques in the Basilar Artery

Vertebral artery (VA) stenosis is relevant to a high early risk of recurrent stroke and basilar artery (BA) is the most common intracranial site of atherosclerotic lesions. It is important to show predictive risk factors for transient ischemic attack (TIA) or posterior infarctions. The aim of the study is to investigate morphometry and hemodynamics in intracranial vertebral and basilar arteries of health and diseased patients to enhance the risk assessment. Based on the geometrical model reconstructed from CTA images in 343 patients, a transient three-dimensional computational model was used to determine the hemodynamics. Patients were classified in symmetric, asymmetric, hypoplastic, and stenotic groups while patients in the stenotic group were divided into unilateral, bilateral, bifurcation, and tandem stenotic sub-groups. Patients in bilateral, bifurcation, and tandem stenotic sub-groups had significantly lower basilar artery diameters than other groups. Patients in the stenotic group had significantly higher surface area ratio (SAR) of high time-averaged wall shear stress gradient (TAWSSG) and higher incidence of TIAs or posterior infarctions than other groups while patients in the tandem stenotic sub-group had the highest values (SAR-TAWSSG of 57 ± 22% and TIAs or posterior infarction incidence of 54%). The high SAR-TAWSSG is predisposed to induce TIAs or posterior infarction.

Novel Oral Anticoagulants as Treatment for Vertebral Artery Dissection: Case Report

BACKGROUND AND PURPOSE

Cervical artery dissections, which may be traumatic or spontaneous, account for a significant proportion of strokes in the young. Antithrombotic therapy is the mainstay of treatment, but new oral anticoagulants could be an alternative treatment to the optimal strategy of anticoagulation followed by antiplatelet drugs.

SUMMARY OF CASE

We report the case of a 40-year-old patient with a spontaneous vertebral artery dissection who developed a cerebellar ischemic stroke, who had a favorable outcome and complete vessel recanalization after three months of treatment with the oral factor Xa inhibitor rivaroxaban.

CONCLUSION

New oral anticoagulant could constitute an alternative and new therapeutic option in cervical artery dissections.

Higher Stroke Risk with Lower Blood Pressure in Hemodynamic Vertebrobasilar Disease: Analysis from the VERiTAS Study

BACKGROUND

Despite concerns regarding hypoperfusion in patients with large-artery occlusive disease, strict blood pressure (BP) control has become adopted as a safe strategy for risk reduction of stroke. We examined the relationship between BP control, blood flow, and risk of subsequent stroke in the prospective Vertebrobasilar Flow Evaluation and Risk of Transient Ischemic Attack and Stroke (VERiTAS) study.

METHODS

The VERiTAS study enrolled patients with recent vertebrobasilar (VB) transient ischemic attack or stroke and ≥50% atherosclerotic stenosis or occlusion of vertebral or basilar arteries. Hemodynamic status was designated as low or normal based on quantitative magnetic resonance angiography. Patients underwent standard medical management and follow-up for primary outcome event of VB territory stroke. Mean BP during follow-up (<140/90 versus ≥140/90 mm Hg) and flow status were examined relative to subsequent stroke risk using Cox proportional hazards analysis.

RESULTS

The 72 subjects had an average of 3.8 ± 1.2 BP recordings over 20 ± 8 months of follow-up; 39 (54%) had mean BP of<140/90 mm Hg. The BP groups were largely comparable for baseline demographics, risk factors, and stenosis severity. Comparing subgroups stratified by BP and hemodynamic status, we found that patients with both low flow and BP <140/90 mm Hg (n = 10) had the highest risk of subsequent stroke, with hazard ratio of 4.5 (confidence interval 1.3-16.0, P = .02), compared with the other subgroups combined.

CONCLUSIONS

Among a subgroup of patients with VB disease and low flow, strict BP control (BP <140/90) may increase the risk of subsequent stroke.