Can a posterior cerebral artery (PCA) territory infarct cause loss of proprioceptive awareness so that a patient cannot tell their hand is moving despite being able to move it?

Loss of Proprioceptive Awareness in PCA Territory Infarcts

Yes, a PCA territory infarct can cause loss of proprioceptive awareness where a patient cannot tell their hand is moving despite preserved motor function, though this is more characteristic of thalamic involvement (which can occur with combined deep and superficial PCA infarcts) rather than pure cortical PCA territory strokes.

Mechanism and Anatomical Basis

The phenomenon you're describing—preserved motor function with absent proprioceptive awareness—occurs when the sensory pathways are disrupted while the motor pathways remain intact. In PCA territory infarcts, this specific pattern emerges through several mechanisms:

Thalamic Involvement (Most Relevant)

• Combined deep and superficial PCA territory infarcts involving the lateral thalamus are more frequent than commonly assumed and are associated with severe contralateral hypesthesia and ataxia 1, 2
• The thalamogeniculate arteries (arising from P2 segment) supply the lateral thalamus, and infarction here causes severe contralateral hypesthesia and ataxia 1
• In one series, 38 patients (73%) with cortical and deep infarcts had unilateral thalamic involvement 3

Sensorimotor Network Disruption

Research demonstrates that loss of motor control can occur even with an intact corticospinal tract when proprioception is severely impaired by dysfunction of the sensorimotor network 4. A case study showed that movement of an affected hand with proprioceptive loss activated only the contralateral primary motor cortex, while activation of the cerebral sensorimotor network (including supplementary motor areas and cerebellum) was severely depressed 4.

Greater proprioceptive error post-stroke is associated with less activity in the ipsilesional supramarginal and superior temporal gyri, lateral thalamus, bilateral supplementary motor area, and ipsilesional premotor cortex 5.

Clinical Presentation Pattern

Deep vs. Superficial PCA Infarcts

The clinical syndrome depends critically on whether the infarct involves:

• Pure cortical (superficial) PCA infarcts: Visual field defects are the predominant finding, with sensory deficits less prominent 3
• Combined cortical and deep infarcts (CDI): Sensorial, motor, and neuropsychological deficits occur mostly in this group 3
• Thalamomesencephalic infarcts (P1 segment): Classical triad includes hypersomnolence, cognitive deficits, and vertical oculomotor paresis 1

Key Clinical Features

• Sensory deficits are common in PCA strokes but often underappreciated compared to the more obvious visual field defects 2
• Combined deep and superficial PCA territory infarcts are associated with reversible slight motor deficits alongside sensory impairment 2
• The posterior choroidal arteries can cause sectoranopia with lateral geniculate body involvement 1

Diagnostic Approach

Imaging Priorities

1. MRI with DWI is most sensitive for detecting PCA territory infarcts, though it can initially be normal in 6-10% of cases (twice as often as anterior circulation) 6
2. CTA should be obtained to identify vessel occlusion and assess collateral status 6
3. Look specifically for thalamic involvement on imaging, as this predicts sensory deficits 1, 3

Clinical Examination Pearls

• Test proprioception explicitly in patients with PCA territory symptoms, even if motor strength appears intact
• The NIHSS has significant limitations in posterior circulation strokes, focusing on limb and speech impairments with less emphasis on cranial nerve and sensory deficits 6
• Patients with pc-ELVO can have an NIHSS score of 0 with only headache, vertigo, and nausea; truncal ataxia is the most common neurological sign in such cases 6

Management Implications

Acute Treatment

• Acute thrombolysis is as useful after PCA infarctions as after anterior circulation strokes 1
• Standard stroke protocols apply, though recognition may be delayed due to atypical presentations 6

Rehabilitation Considerations

• Intensive rehabilitation with visual support can enable independent living despite proprioceptive deficits 4
• Most rehabilitative interventions emphasize motor deficits but rarely address sensory function and sensorimotor control—this is a critical gap 4
• The sensorimotor network dysfunction requires targeted therapy, not just motor strengthening 4, 5

Prognostic Factors

Favorable Outcomes

• Mortality after PCA strokes is low (7% in one series) 1, 3
• Pure cortical PCA infarcts generally have good outcomes 3

Poor Prognostic Indicators

• Consciousness disturbances at onset (RR 66.6) 3
• Mesencephalic and/or thalamic involvement (RR 3.79) 3
• Proximal large-artery disease (RR 2.71) 3
• Basilar artery disease (RR 5.94) 3

Critical Caveats

Long-term behavioral and cognitive deficits after PCA strokes are underestimated 1. While visual field defects receive attention, the sensory and proprioceptive impairments may be more functionally limiting and require specific rehabilitation strategies that incorporate visual compensation techniques 4.

The specific syndrome you describe—preserved motor function with absent proprioceptive awareness—should prompt immediate imaging to assess for thalamic involvement in the PCA territory, as this represents a combined deep and superficial infarct pattern with specific rehabilitation needs.