Bilateral Cerebral Infarctions Secondary to Unilateral ICA Stenosis

A 76-year-old diabetic man presented to us with complaints of sudden-onset right-sided weakness for the last 4 days. On evaluation, he was found to have right hemiparesis (Modified Medical Research Council grade 4-/5) along with left leg weakness (4+/5). Neuroimaging revealed acute infarcts in the right anterior cerebral artery (ACA) territory and left cerebral external watershed territory. Magnetic resonance (MR) angiogram of the brain showed a hypoplastic right A1-ACA with bilateral A2-ACA arising from the left A1-ACA (bi-hemispheric A1-ACA). MR angiogram of the neck revealed significant left internal carotid artery (ICA) origin stenosis. It was concluded that the origin of right A2-ACA from left ACA was the probable because of right ACA infarcts, along with left cerebral watershed infarcts (embolic phenomenon). This represents a very important variation, as in these cases, even a unilateral ICA stenosis can lead to bilateral ACA stroke and thus necessitates urgent revascularization.