What are the clinical features and management of a patient with a high parietal lobe infarct on the right (rt) side?

Clinical Features of Right High Parietal Lobe Infarction

A right high parietal lobe infarct characteristically produces left-sided motor and sensory deficits, left-sided neglect, and visuospatial dysfunction, with the critical distinction that these deficits may be subtle and easily underestimated compared to left hemisphere strokes. 1

Primary Motor and Sensory Deficits

Contralateral (left-sided) manifestations:

• Left hemiparesis or hemiplegia affecting the face, arm, and leg, though the pattern may be less severe than MCA territory strokes since the parietal lobe is primarily sensory cortex 1
• Left hemisensory loss involving the entire left hemibody, including impaired touch, proprioception, and nociception 2
• Sensory inattention or extinction to double simultaneous stimulation on the left side 3

The motor deficits from pure parietal infarction are typically less pronounced than those from MCA territory involvement, as the motor cortex lies anteriorly in the frontal lobe 3.

Characteristic Right Hemisphere Cognitive Deficits

Left-sided neglect syndrome is the hallmark cognitive feature of right parietal infarction:

• Inattention to the left side of space, including failure to recognize left-sided stimuli 1
• Patients may ignore the left side of their body, food on the left side of a plate, or objects in left visual space 3
• This represents a disturbance of orienting and attending to sensory events 4

Visuospatial dysfunction distinguishes right from left hemisphere strokes:

• Abnormal visual-spatial ability and constructional apraxia 1
• Impaired spatial orientation and navigation 1

Visual Field Deficits

• Left homonymous hemianopsia may occur if the optic radiations coursing through the parietal white matter are affected 1
• The superior parietal location makes inferior quadrantanopia more likely if visual pathways are involved 3

Critical Pitfall: Underestimation of Severity

The right parietal stroke is frequently underestimated in severity because neglect and visuospatial deficits are more subtle than the aphasia seen in left hemisphere strokes. 1 This leads to:

• Delayed recognition of potentially malignant infarction 1
• Inadequate monitoring for clinical deterioration 1
• Missed opportunities for early intervention 1

Signs of Clinical Deterioration

Monitor closely for malignant cerebral edema, which develops rapidly between 12-72 hours post-stroke 1:

• Progressive headache indicating developing cerebral edema 1
• Nausea and vomiting as both initial symptoms and predictors of malignant edema 1
• Declining level of consciousness progressing from alert to obtunded to comatose 1
• Ipsilateral (right-sided) pyramidal signs suggesting transtentorial herniation 1
• Pupillary dilation, initially ipsilateral then bilateral, as a critical herniation sign 1

Predictors of Malignant Course

High-risk features requiring intensive monitoring include 1:

• NIHSS ≥15 for right hemisphere strokes
• Nausea and vomiting at presentation
• History of hypertension or heart failure
• Elevated white blood cell count

Associated Cardiac Complications

Right parietal lobe infarction carries specific cardiac risk:

• Lesions in parietal cortex field 7 can cause compensatory excitement of the sympathetic center in the posterior lateral nucleus of the hypothalamus 5
• This predisposes to tachyarrhythmias, ventricular fibrillation, and sudden death 5
• Troponin elevation and ECG changes mimicking acute myocardial infarction may develop days to weeks after the stroke 5
• Continuous cardiac monitoring is mandatory in patients with right parietal infarction and left upper limb weakness 5

Examination Approach Using NIHSS

Key NIHSS components for right parietal assessment 3:

• Level of consciousness (items 1A-1C): Alert vs drowsy vs obtunded
• Gaze (item 2): Assess for left gaze preference
• Visual fields (item 3): Test for left hemianopsia
• Motor function (items 5-6): Left arm and leg drift or weakness
• Sensory (item 8): Left-sided sensory loss
• Extinction and inattention (item 11): Critical for detecting neglect—test visual and tactile stimuli bilaterally

Differential Considerations

Superior sagittal sinus thrombosis can mimic parietal infarction:

• Brain parenchymal changes in frontal, parietal, and occipital lobes typically correspond to superior sagittal sinus thrombosis 3
• Consider venous imaging (CTV or MRV) if clinical presentation is atypical or if there is hemorrhagic transformation 3

Posterior cerebral artery (PCA) territory involvement may produce overlapping features:

• Proximal PCA occlusion can simulate MCA syndrome with hemiparesis, hemianopia, hemispatial neglect, and sensory loss 6
• Thalamic involvement from PCA stroke explains "cortical" signs 6