Anterior Cerebral Artery (ACA) Territory Infarct: Signs and Symptoms
ACA territory infarcts present most characteristically with contralateral leg weakness (often monoparesis), behavioral changes including apathy and akinetic mutism, and urinary incontinence, distinguishing them from the more common middle cerebral artery strokes. 1
Classic Motor Deficits
The hallmark motor presentation involves contralateral lower extremity weakness or monoparesis, which is more prominent than upper extremity involvement 1, 2. This leg-predominant pattern results from infarction of the paracentral lobule, where the motor homunculus representation for the leg resides. When Heubner's artery (recurrent artery of Heubner) is involved, you may see additional arm and face weakness due to damage to the medial striate arteries and anterior limb of the internal capsule 1.
Behavioral and Cognitive Features
Apathy and hypobulia are extremely common, occurring in approximately 55% of patients initially 3. The most dramatic behavioral manifestation is akinetic mutism—a state where patients are awake but demonstrate profound lack of spontaneous movement and speech 1. This reflects damage to the supplementary motor area and anterior cingulate cortex.
Additional behavioral signs include:
- Grasp reflex and alien hand sign (callosal disconnection phenomena) 1
- Transcortical motor aphasia when the left hemisphere is affected 1
- Abulia and reduced psychomotor activity 3
- Primitive reflexes (33% of patients initially) 3
Urinary Incontinence
Urinary incontinence occurs in approximately 48% of patients at initial presentation 3, 1. This results from damage to the paracentral lobule affecting bladder control centers.
Sensory Deficits
Contralateral sensory loss affecting the leg can occur, though sensory deficits are less prominent than motor deficits and actually serve as a negative predictor for ACA stroke when compared to posterior cerebral artery infarction 2.
Atypical Presentations: The MCA Mimic
Critical pitfall: Recent case reports demonstrate that distal ACA occlusions can present with global aphasia and dense hemiparesis, mimicking middle cerebral artery syndrome 4, 5. This occurs when the supplementary motor area is affected, producing what appears to be a more severe deficit than expected. These atypical presentations can lead to diagnostic delays and inappropriate treatment decisions.
When you encounter:
- Non-fluent aphasia with right hemiparesis
- Dense contralateral weakness involving arm and face (not just leg)
- Clinical picture suggesting MCA territory
Always verify the actual vascular territory with imaging before making treatment decisions, as ACA involvement may be the true culprit 4, 5.
Headache
Non-throbbing headache at stroke onset is common, particularly in patients with ACA dissection as the underlying mechanism 1.
Etiologic Considerations
Cardioembolism is the predominant mechanism (45-49% of cases), making ACA stroke more likely cardioembolic than atherothrombotic 2. This has implications for secondary prevention strategies. Note that etiologic factors vary by race, with ACA dissection being particularly common in Japanese populations 1.
Prognosis and Recovery
The natural history shows significant improvement over time. While only 9.8% of patients are symptom-free at hospital discharge 2, behavioral symptoms improve substantially:
- Apathy: 55.5% initially → 22.7% at one year 3
- Incontinence: 48% initially → 27.2% at one year 3
- Aphasia: 40.7% initially → 4.5% at one year 3
In-hospital mortality is approximately 7.8% 2, which is relatively favorable compared to other stroke territories.
Regional Vulnerability Pattern
The superior frontal gyrus and anterior cingulate gyrus have the highest infarction probability (26% and 24% respectively), while the posterior cingulate, paracentral lobule, and precuneus are relatively protected due to leptomeningeal collaterals 6. This collateral circulation explains why ACA strokes are relatively uncommon (only 0.5-3% of all ischemic strokes) despite the frequency of proximal vessel disease 1, 2.