What are the typical arterial territories and associated clinical findings for localizing ischemic infarcts in a cerebrovascular accident?

CVA Infarct Localization: Arterial Territories and Clinical Findings

Middle Cerebral Artery (MCA) Territory

The MCA is the most commonly affected vessel in ischemic stroke, producing contralateral hemiparesis that characteristically affects the face and arm more than the leg, with parallel sensory loss and homonymous hemianopia. 1, 2

Right MCA Infarction

• Left-sided hemiplegia with face and arm weakness greater than leg weakness, due to lateral motor cortex involvement 1
• Left hemisensory loss affecting all sensory modalities from right sensory cortex damage 1
• Left homonymous hemianopia from disruption of right optic radiations or visual cortex 1
• Left-sided neglect and visuospatial deficits characteristic of non-dominant hemisphere involvement 2
• Approximately 19% may lack overt cortical deficits initially despite cortical involvement 1

Left MCA Infarction

• Right-sided hemiparesis with face and arm predominance 1, 2
• Aphasia (Broca's, Wernicke's, or global) from dominant hemisphere involvement 2
• Right homonymous hemianopia 2
• Loss of cortical sensory functions including stereognosis, graphesthesia, and two-point discrimination 2

Early CT Imaging Signs (detectable in 82-94% within 6 hours)

• Hyperdense MCA sign indicating thrombus in the proximal MCA 2
• Loss of gray-white differentiation in the insular ribbon or lentiform nucleus 2
• Sulcal effacement 2
• Critical pitfall: Involvement of >1/3 MCA territory carries 8-fold increased hemorrhagic transformation risk with thrombolysis 2

Anterior Cerebral Artery (ACA) Territory

ACA infarcts produce contralateral weakness that is most prominent in the lower extremity, distinguishing them from MCA strokes. 1

• Leg weakness greater than arm or face from medial motor cortex involvement 1
• Sensory loss following the same distribution 1
• If both upper and lower extremities are equally weak, suspect MCA rather than ACA territory 1

Posterior Cerebral Artery (PCA) Territory

PCA infarcts most commonly result from cardiac or intra-arterial embolism (73% combined), presenting primarily with visual deficits. 3

Clinical Presentation

• Visual abnormalities in 84% of patients, including homonymous hemianopia 3
• Motor weakness in only 25% of cases 3
• Cognitive and behavioral abnormalities in 25% 3
• Sensory signs in only 15% 3

Infarct Patterns

• Pure PCA territory involvement in 61% of cases 3
• Combined cortical and deep infarcts in 41% 3
• Multiple territory involvement (PCA+) in 39%, more common with proximal arterial disease 3

Stroke Mechanisms

• Cardiogenic embolism: 41% 3
• Proximal arterial disease: 32% 3
• Intrinsic PCA disease: 9% 3
• Vasoconstriction and coagulopathy: combined 9% 3

Posterior Circulation: Brainstem and Cerebellar Territories

Superior Cerebellar Artery (SCA)

SCA infarcts are predominantly embolic (56% combined embolic mechanisms), with multiple lesions being the most common pattern. 4

• Lateral SCA territory most frequently involved 4
• Borderzone SCA infarcts occur in one-third of patients with transient benign symptoms 4
• Mass effects unusual despite large territorial involvement 4
• Seven distinct lesion patterns identified on diffusion-weighted imaging 4

Brainstem Infarction

• Level of consciousness is the most reliable indicator of impending deterioration 5
• Pupillary changes (anisocoria or pinpoint pupils) indicate brainstem compression 5
• CT is relatively insensitive for posterior fossa lesions; MRI is essential when clinical suspicion is high 5

Thalamic Infarction

• Executive dysfunction and behavioral changes characteristic 5
• Accounts for only 4.6% of stroke locations 5
• Early CT often normal or non-revealing, requiring MRI for diagnosis 5

Borderzone (Watershed) Infarcts

Borderzone infarcts constitute approximately 10% of all brain infarcts and occur at junctions between major arterial territories. 6

Two Distinct Types with Different Mechanisms

• Internal (subcortical) borderzone infarcts: caused mainly by hemodynamic compromise 6
• External (cortical) borderzone infarcts: result from embolism, not always with hypoperfusion 6
• Multiple small internal infarcts are independent predictors of subsequent ischemic stroke 6

Critical Diagnostic Pitfalls

• Normal early CT does not exclude acute ischemic stroke—CT shows abnormalities in <50% of patients in the first hours 2
• Physician accuracy for detecting >1/3 MCA territory involvement is only 70-80% 2
• CT is relatively insensitive for small cortical/subcortical lesions and posterior fossa infarcts 2, 5
• Do not delay thrombolytic therapy to obtain advanced imaging beyond non-contrast CT if the patient is otherwise eligible 2
• MRI improves localization and changes clinical diagnosis in 16.3% of cases, particularly for brainstem, cerebellar, and multiple territory infarcts 7