What is the location of the stroke?

Stroke Location: Diagnostic Approach

The location of a stroke is determined primarily through neuroimaging—with MRI diffusion-weighted imaging (DWI) being the gold standard—combined with clinical localization based on the specific neurological deficits present. 1, 2

Imaging Modalities for Stroke Localization

First-Line Imaging

• Non-contrast CT (NCCT) is the most commonly used initial modality due to its rapidity and widespread availability, though it has lower sensitivity for small or posterior fossa lesions 2
• MRI with DWI is the most sensitive and specific technique for detecting acute ischemic stroke, with sensitivity of 88-100% and specificity of 95-100%, and can detect ischemic changes within minutes 2, 3
• For suspected cerebellar stroke specifically, MRI offers much better visualization of the posterior fossa compared to CT 3

Vascular Imaging

• CT angiography (CTA) or MR angiography (MRA) should be performed during initial evaluation to identify the site of vessel occlusion and determine if large vessel occlusion is present 1
• CTA has high accuracy for large vessel occlusion detection with high interrater reliability 1

Common Stroke Locations by Vascular Territory

Anterior Circulation (Most Common)

• Middle cerebral artery (MCA) territory accounts for approximately 62% of single large vessel strokes and is the most frequent location overall 4
• MCA strokes typically present with hemiparesis, hemisensory loss, aphasia (if dominant hemisphere), and spatial neglect 2
• The typical finding in embolic stroke from carotid disease is multiple small cortical infarcts in the MCA territory and vascular border-zone areas 1

Posterior Circulation

• Posterior cerebral artery (PCA) accounts for 12% of single large vessel strokes 4
• Basilar artery distribution represents 9% of single large vessel strokes 4
• Posterior inferior cerebellar artery (PICA) accounts for 8% of single large vessel strokes 4
• Posterior circulation strokes present with vertigo, ataxia, diplopia, and dysarthria 2

Small Vessel (Lacunar) Strokes

• Internal capsule lacunar strokes account for 18% of all strokes 4
• Brainstem lacunar strokes represent 8% of strokes 4
• Thalamic lacunar strokes account for 5% of strokes 4
• These present with pure motor weakness, ataxic hemiparesis, and dysarthria 2

Multiple Territory Involvement

When strokes involve multiple vascular territories bilaterally, this strongly indicates a proximal embolic source such as cardiac chambers, heart valves, or aortic arch rather than individual arterial stenoses. 5

• Scattered emboli in multiple territories mandate comprehensive cardiac evaluation including transthoracic and transesophageal echocardiography, plus continuous cardiac monitoring for atrial fibrillation 5
• Approximately 9% of strokes occur in more than one vascular territory 4

Clinical Localization Principles

Hemispheric Strokes

• MCA territory lesions have lower rates of complete neurological recovery (50%) compared to other locations (83%) 2
• Anterior cerebral artery (ACA) strokes account for 7% of single large vessel strokes 4

Watershed Infarctions

• Watershed infarctions account for 3% of strokes, occurring primarily in MCA/PCA (9 cases) and MCA/ACA (3 cases) border zones 4
• Haemodynamic cerebral lesions typically occur in these watershed zones 1

Critical Imaging Timing Considerations

• Within 6 hours: NCCT followed by multiphase CTA is sufficient for treatment decisions; CT perfusion is not necessary in this timeframe 3
• Beyond 6 hours or unknown onset: Advanced imaging with perfusion assessment (CTP or MRI perfusion) becomes essential for treatment selection 3
• Never delay treatment for advanced imaging, as time-sensitive reperfusion therapies take priority 3

Prognostic Implications

• The volume of acute infarct on DWI correlates with motor outcome and predicts functional recovery 2
• Frank hypodensity on CT within the first 6 hours and early midline shift predict cerebral edema 3
• Patients with MCA strokes have the lowest FIM efficiency scores compared to other vascular territories 6