Acute Bihemispheric Stroke from a Single Carotid Source: Risk Factors, Mechanisms and Outcome

Background— Mechanisms and natural history of acute bihemispheric strokes (ABSs) from a single carotid source
are little known. Aim of our study was to identify risk factors, mechanisms and outcome in ABS from a single carotid
source in a consecutive series of ABS patients.
Methods— From the ASTRAL registry (2003-2018) we retrospectively selected patients with acute ischemic
lesion(s) in one or both carotid territories confirmed on brain DWI-MRI, significant carotid artery disease (>50%
stenosis or acute dissection) in the arterial territory(ies) involved, and no other concomitant stroke etiology. Baseline
features and outcome of patients with ABS were compared to all patients with unilateral ischemic lesions and to a
group matched for age, grade of stenosis and etiology of the carotid disease (atherosclerosis or dissection).
Results— We included 184 patients having median age of 65.3 years (IQR 53.5-77.1) and median NIHSS of 6.
Twenty-three patients (12.5%) had ABS, while 161 had unilateral lesions. In the multivariate analysis of the matched
cohort, patients with ABS had significantly lower diastolic blood pressure (DBP) on admission (OR 0.96; 95%CI
0.92-1.00, p=0.04), more frequently contralateral internal carotid (ICA) occlusion (OR 49.79; 95% CI 2.99-829.82,
p=0.01) and absence of anterior communicating artery (ACoA) (OR 14.28; 95%CI 3.03-100, p=0.00). ABS was as
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sociated with lower probability of 3-month functional independence (adjOR 0.24; 95%CI 0.06-0.92, p=0.04).
Conclusions— Bihemispheric stroke may occur in stroke patients with a single carotid source. Their association
with lower admission DPB, contralateral ICA occlusion and absence of ACoA suggests contralateral hypoperfusion
as the main mechanism.