In an adult middle‑aged or older patient with typical vascular risk factors, is a right cerebral hemispheric ischemic stroke caused by right internal carotid artery disease?

Can Right ICA Disease Cause Right Hemispheric Stroke?

Yes, right internal carotid artery (ICA) disease can definitely cause ipsilateral (right-sided) cerebral hemispheric ischemic stroke through multiple well-established mechanisms. 1

Mechanisms of Stroke from Ipsilateral ICA Disease

The 2025 ESC consensus statement clearly identifies that carotid atherosclerotic disease causes stroke primarily through:

• Athero-thromboembolism - plaque inflammation and disruption with embolism of locally formed thrombus or plaque debris, leading to occlusion of cerebral arteries in the anterior circulation (most common mechanism) 1
• Hemodynamic compromise - reduced cerebral perfusion from critical stenosis or occlusion when collateral circulation is deficient 1
• Acute thrombotic occlusion - from plaque rupture 1
• Arterial dissection - structural disintegration of the arterial wall 1

Clinical Presentation of Right ICA Stroke

Right hemispheric strokes from right ICA disease typically present with:

• Hemineglect (predominantly in the right hemisphere) 1
• Left-sided motor or sensory deficits (contralateral to the lesion) 1
• Left hemianopsia (if optic tract involved) 1
• Monocular blindness of the right eye (amaurosis fugax) from retinal artery occlusion 2

Note that aphasia typically occurs with left hemispheric lesions, not right 1.

Imaging Patterns

DW-MRI studies demonstrate that right ICA disease produces characteristic stroke patterns in the right hemisphere:

• Multiple small cortical infarcts in the middle cerebral artery (MCA) territory and vascular border-zone areas 1
• Territorial ischemia (especially with ICA occlusion - occurs in 47.6% of cases) 3
• Hemodynamic watershed infarcts (particularly with high-grade stenosis - occurs in 50% of cases) 3
• Disseminated lesions in distal cortical regions 3

The specific pattern depends on stenosis severity, with statistical significance (p=0.001) between stenosis degree and stroke pattern 3.

Epidemiological Evidence

Population-based data confirm the causal relationship:

• 7% of all first ischemic strokes are associated with extracranial carotid stenosis ≥60% 1
• 18% of first ischemic strokes are attributed to extracranial or intracranial large-vessel disease 1
• The incidence is higher in certain populations (17 per 100,000 for blacks, 9 per 100,000 for Hispanics, 5 per 100,000 for whites) 1

Important Clinical Caveats

Collateral circulation matters significantly - the severity of symptoms from right ICA disease depends heavily on the efficacy of compensatory collateral supply via the circle of Willis and/or external carotid artery, ranging from clinically silent to catastrophic 1. Patients with better collateral flow through the anterior and posterior communicating arteries have higher flow velocities in the ipsilateral MCA and are more likely to remain asymptomatic 4.

Silent brain infarctions are common - patients with asymptomatic right ICA disease have a higher prevalence of silent brain infarction in the right hemisphere compared to the left, and these silent infarcts double the risk of future stroke 1. Up to 24% of patients with acute ocular vascular events have silent brain infarcts 2.

Contralateral symptoms do NOT exclude ipsilateral ICA disease - patients with contralateral or posterior circulation symptoms who have ipsilateral carotid stenosis are conventionally considered "asymptomatic" for that stenosis, but they still carry stroke risk 1.

Risk Stratification

The stroke risk from right ICA disease increases with:

• Stenosis severity - carotid stenosis >50% is the strongest predictor of new vascular events after TIA 1
• Plaque characteristics - echolucency, intraplaque hemorrhage, ulcerations, lipid-rich necrotic cores 1
• Recent symptoms - TIA from carotid stenosis carries approximately 6% stroke risk in the first year 1