Posterior Cerebral Artery (PCA) Territory Infarct: Signs and Symptoms
Visual field defects, particularly homonymous hemianopia, are the hallmark presenting feature of PCA territory infarcts, occurring in approximately 84-87% of patients, with most patients describing the visual loss as a negative phenomenon (darkness) affecting the same hemifield in both eyes 1, 2.
Core Clinical Manifestations
Visual Symptoms (Most Common)
- Homonymous hemianopia or quadrantanopia - the dominant presenting sign 3, 1
- Patients typically recognize the visual loss is lateralized to one hemifield in both eyes (66% of cases) 1
- Visual loss described as "negative" (darkness/absence) rather than positive phenomena in 87% 1
- Cortical blindness may occur with bilateral PCA infarcts 4
- Palinopsia and cerebral dyschromatopsia are rare but documented presentations 5
Sensory Deficits (Second Most Common)
- Contralateral numbness and tingling - present in approximately 43% of patients 1
- Severe contralateral hypesthesia, particularly with thalamogeniculate artery involvement 4
- Sensory signs are strongly linked to concurrent thalamic infarction 1
Motor Findings (Less Common)
- Motor weakness occurs in only 25% of pure PCA territory infarcts 2
- Typically mild and reversible when present 6
- More severe motor deficits suggest precommunal PCA segment occlusion with paramedian midbrain involvement 6
Cognitive and Behavioral Abnormalities
- Present in 25% of patients 2
- Reading disorders (alexia) after left-sided lesions 4
- Disorientation and visual neglect after right-sided lesions 4
- Amnesia with bilateral PCA infarcts 4
- Marked behavioral symptoms can be the predominant presentation, though rare 7
Additional Neurological Signs
- Ataxia - occurs in 25% 2
- New-onset headache - common presenting symptom, often unilateral 6
- Vertical oculomotor paresis with thalamomesencephalic infarcts 4
- Hypersomnolence with rostral midbrain/thalamic involvement 4
Critical Anatomical Correlations
Deep PCA Territory (P1-P2 segments)
When paramedian perforating arteries are involved:
- Classical triad: hypersomnolence, cognitive deficits, and vertical oculomotor paresis 4
- Thalamogeniculate artery occlusion: severe hypesthesia and ataxia 4
- Posterior choroidal artery occlusion: sectoranopia with lateral geniculate body involvement 4
Superficial PCA Territory (P3-P4 segments)
- Visual field defects predominate 4
- Somatosensory deficits are frequent 4
- Neuropsychological deficits based on hemisphere affected 4
Important Clinical Pitfalls
90% of PCA strokes occur without preceding warning symptoms 1, making acute recognition challenging. However, 10% do have warning symptoms that are often missed retrospectively 1.
20% of PCA strokes occur within 72 hours of a medical or surgical procedure, making iatrogenic causes an important consideration 1.
The clinical presentation can mimic complicated migraine due to the frequent unilateral headache, creating a diagnostic challenge 6.
Bilateral thalamic involvement can occur without focal neurological findings, presenting only with altered consciousness due to involvement of the deep venous drainage system 8.
Temporal Presentation
Symptoms typically develop acutely (<48 hours in 37% of posterior circulation strokes), though subacute (48 hours to 30 days) presentation occurs in 56% 8. The median delay from symptom onset to hospital admission is 4 days for posterior circulation strokes 8.
Prognosis Indicators
Mortality after PCA strokes is low compared to anterior circulation strokes 4, but long-term behavioral and cognitive deficits are frequently underestimated 4. Precommunal PCA segment occlusion with paramedian midbrain infarction carries a poorer prognosis than other PCA territory infarcts 6.