Anatomic Localization of Stroke with Right Hemiparesis and Aphasia
The stroke is located in the left hemisphere, specifically involving the left internal carotid artery or left middle cerebral artery distribution. 1
Primary Anatomic Explanation
Ischemia or infarction in the distribution of the left internal carotid artery or middle cerebral artery causes right-sided weakness, right-sided sensory loss, and aphasia. 1 This represents the classic presentation of dominant hemisphere stroke in a right-handed individual.
Key Anatomic Structures Involved
The combination of right hemiparesis and aphasia localizes to:
- Left hemisphere cortical and subcortical structures supplied by the left middle cerebral artery 1
- Language areas including Broca's area, Wernicke's area, and connecting white matter tracts such as the arcuate fasciculus 1, 2
- Motor cortex and corticospinal tract on the left side, producing contralateral (right-sided) weakness 1
Language Localization Details
Aphasia results from damage to left hemisphere language networks, with specific deficits correlating to distinct anatomic regions:
- Broca's aphasia (nonfluent, effortful speech with relatively preserved comprehension) results from damage to white matter above the insula and the anterior arcuate fasciculus 2
- Wernicke's area involvement (posterior superior temporal gyrus) produces comprehension deficits when hypoperfused or infarcted 1
- Arcuate fasciculus damage impairs repetition and connects temporal, parietal, and frontal language regions 1, 2
Important Clinical Caveat
In rare cases (approximately 3-5% of right-handed individuals), aphasia can occur with right hemisphere stroke in patients with atypical language dominance. 3 However, this "crossed aphasia" is uncommon and shows more variable anatomic-clinical correlations with less frequent comprehension and repetition impairments compared to typical left hemisphere stroke aphasia 3. In ambidextrous or left-handed individuals, aphasia may result from right internal carotid artery or middle cerebral artery distribution stroke. 1
Motor Pathway Localization
Right hemiparesis indicates damage to the left motor cortex or descending corticospinal tract before it crosses at the medullary decussation. 1 The motor deficit is contralateral to the lesion because motor fibers cross to the opposite side of the body.
Clinical Implications
The presence of both right hemiparesis AND aphasia strongly suggests a large left middle cerebral artery territory infarction affecting both motor cortex (producing hemiparesis) and perisylvian language areas (producing aphasia). 1 This combination indicates significant stroke burden and warrants immediate evaluation for thrombolytic therapy or thrombectomy if within the appropriate time window. 1
Stroke affecting the left hemisphere language areas occurs in 21-38% of acute stroke patients and is associated with high morbidity and mortality. 4, 5