Internal Cerebral Vein Asymmetry on Follow-up Brain Computed Tomography after Intravenous Thrombolysis in Acute Anterior Circulation Ischemic Stroke Is Associated with Poor Outcome

Background

Identifying early predictors of functional outcome after acute ischemic stroke (AIS) is important for planning rehabilitation strategies. Internal cerebral veins (ICV) drain deep parts of brain, run parallel to each other, and consistently seen on computed tomography angiography (CTA). Even minor asymmetry in their filling can be identified. We hypothesized that venous drainage would be impaired in patients with acute occlusion of internal carotid artery or middle cerebral artery. Because systemic thrombolysis can alter the vascular findings, we evaluated the relationship between ICV asymmetry on follow-up CTA and functional outcome.

Methods

Consecutive AIS patients treated with intravenous thrombolysis between 2007 and 2010 were included. ICV asymmetry was assessed by 2 independent blinded stroke neurologists/neuroradiologists. Functional outcome was assessed by the modified Rankin Scale (mRS) at 3 months, dichotomized as good (0-1) and poor (2-6). Data were analyzed for predictors of functional outcome.

Results

Of 2238 patients with AIS, 226 (10.1%) anterior circulation AIS patients received intravenous thrombolysis. The median age was 65 years (range 19-92), 44% were men, and median National Institutes of Health Stroke Scale (NIHSS) score was 16 points (range 4-32). Hypertension was the commonest risk factor in 173 (76.5%) patients, whereas 78 (34.5%) had atrial fibrillation. ICV asymmetry on follow-up CTA was assessed in 103 (45.5%) patients. Admission NIHSS score (odds ratio [OR] 1.07; 95% confidence interval [CI] 1.079-1.201, P = .046), change in NIHSS score during first 24 hours (OR .737; 95% CI .672-.807, P < .0001), and ICV asymmetry on follow-up CTA (OR 20.3; 95% CI 4.67-52.07, P < .0001) independently predicted poor outcome at 3 months.

Conclusions

ICV asymmetry on follow-up CTA after intravenous thrombolysis is an early predictor of poor functional outcome.

Introduction

A significant proportion of acute ischemic stroke (AIS) patients achieve good functional outcome with timely administered intravenous tissue plasminogen activator (tPA). However, the rate and extent of recovery remain variable. Considering scarce and costly resources, early identification of reliable predictors for functional outcome is important for planning rehabilitation strategies and placement after discharge from the hospital. Internal cerebral veins (ICVs) drain the deep parts of cerebral hemispheres and run backward to form the great cerebral vein.¹ Impaired arterial blood supply results in poor venous drainage, rendering the corresponding ICV less visible. Because the 2 ICVs are consistently seen on computed tomographic angiography (CTA) as running parallel and very close to each other, even minor asymmetry in their filling can be diagnosed easily on CTA (Fig 1).² We hypothesized that ipsilateral cerebral hypoperfusion because of acute occlusion of internal carotid artery (ICA) or middle cerebral artery (MCA) would impair the ipsilateral deep venous drainage and result in obvious asymmetric opacification of the ICVs. Therefore, ICV asymmetry might serve as a surrogate marker of inadequate cerebral perfusion and collateral circulation.

Because a significant proportion of intravenous tPA-treated patients achieve arterial recanalization³ and many of them might develop sufficient collateral arteries during the early phase of AIS,⁴ ICV asymmetry on the pre-tPA CTA can disappear. Therefore, ICV asymmetry on a pre-tPA CTA may not be useful for predicting the long-term outcomes. On the other hand, vascular status of the intracranial circulation is believed to acquire its near-final status in majority of AIS patients by day 2. Therefore, we aimed to evaluate whether the presence of ICV asymmetry on day 2 CTA in tPA-treated AIS patients can predict the final outcome.