Right Middle Cerebral Artery (MCA) Territory Infarction
This clinical presentation of left-sided hemiplegia, left hemisensory loss, and left homonymous hemianopia localizes to the right middle cerebral artery (MCA) territory. 1, 2, 3
Anatomical Localization
The right MCA supplies the lateral motor cortex containing motor representation for the contralateral (left) face and upper extremity, which explains the left-sided hemiplegia. 1, 4, 3 The characteristic pattern of MCA territory infarction produces contralateral hemiparesis affecting the face and arm more prominently than the leg, with sensory deficits following a similar distribution. 1, 3
The presence of left homonymous hemianopia confirms MCA territory involvement, as this visual field deficit results from damage to the optic radiations or visual cortex supplied by the MCA. 1 The combination of motor, sensory, and visual deficits affecting the entire left side indicates a large right MCA territory infarction. 2
Distinguishing from Other Arterial Territories
Why Not Anterior Cerebral Artery (ACA)?
The ACA supplies the medial motor cortex containing motor representation for the contralateral lower extremity. 4 ACA territory infarction characteristically causes contralateral weakness that is most prominent in the lower extremity, not the face and arm. 1, 4 This patient's presentation with hemiplegia affecting face, arm, and leg together—rather than leg-predominant weakness—excludes ACA territory involvement. 3
Why Not Posterior Cerebral Artery (PCA)?
While isolated homonymous hemianopia can result from PCA territory infarction affecting the occipital cortex, the presence of hemiplegia and hemisensory loss indicates involvement of motor and sensory cortex, which are not supplied by the PCA. 1 The PCA does not supply the motor or primary sensory cortex responsible for this patient's deficits.
Why Not Ophthalmic Artery?
Ophthalmic artery occlusion causes monocular blindness affecting one eye, not homonymous hemianopia. 1 Homonymous hemianopia indicates retrochiasmal visual pathway involvement (optic tract, optic radiations, or occipital cortex), not anterior visual pathway damage. 1
Clinical Syndrome Recognition
Ischemia or infarction in the distribution of the right internal carotid artery or middle cerebral artery causes left-sided weakness, left-sided paresthesia or sensory loss, left-sided neglect, abnormal visual-spatial ability, and left homonymous hemianopsia. 1 This patient demonstrates the classic triad of:
- Motor deficit: Left hemiplegia from damage to right motor cortex 1, 3
- Sensory deficit: Left hemisensory loss from damage to right sensory cortex 1, 5
- Visual deficit: Left homonymous hemianopia from damage to right optic radiations or visual cortex 1
Common Pitfalls
Do not confuse equal upper and lower extremity weakness with leg-predominant weakness. 3 When both extremities are equally weak (as implied by "hemiplegia"), this represents MCA territory involvement. If the leg were significantly weaker than the arm, you would suspect ACA territory or parasagittal lesions. 4, 3
Cortical deficits may be absent in approximately 19% of cortical stroke patients on initial examination, making anatomical localization challenging. 6 However, the presence of homonymous hemianopia in this case confirms cortical involvement, as this deficit requires damage to cortical visual pathways. 1
The pseudothalamic sensory syndrome can occur with parietal stroke involving the parietal operculum and posterior insula, causing faciobrachiocrural impairment of elementary sensation that mimics thalamic stroke. 5 However, the presence of significant motor weakness and hemianopia indicates more extensive MCA territory involvement beyond isolated parietal cortex. 1, 2