Left Middle Cerebral Artery (MCA) or Left Internal Carotid Artery (ICA) Stroke Syndrome
Right-sided weakness with right facial drooping indicates ischemia or infarction in the distribution of the left internal carotid artery or left middle cerebral artery. 1
Clinical Localization
The combination of right-sided body weakness and right facial involvement localizes to the left hemisphere, specifically:
- Left MCA territory is the most common location for this presentation 1, 2
- Left ICA territory can produce identical symptoms 1
- The face, arm, and leg are all supplied by the MCA territory, making this the primary vascular distribution affected 2
Key Distinguishing Features
Additional symptoms to assess that confirm left hemisphere involvement include:
- Aphasia (language dysfunction) - this is the critical distinguishing feature of left hemisphere stroke in right-handed individuals 1
- Right-sided sensory loss or paresthesias 1
- Left visual field deficits (left homonymous hemianopsia) or monocular blindness affecting the left eye 1
Important caveat: Aphasia may occur with right hemisphere stroke in ambidextrous or left-handed individuals 1
Why This Matters Clinically
Left hemisphere strokes are recognized more readily than right hemisphere strokes because aphasia is more obvious to observers than the neglect and visuospatial deficits seen with right hemisphere lesions 3. This recognition bias means:
- Left hemisphere strokes present to hospitals more frequently (56% vs 44%) 3
- Patients arrive earlier after symptom onset 3
- The NIHSS score systematically rates left MCA strokes as more severe than right MCA strokes of equal volume, particularly when NIHSS >5 4
Immediate Diagnostic Approach
Urgent neuroimaging is mandatory:
- Brain MRI with diffusion-weighted imaging (DWI) is the preferred initial test 5, 6
- If MRI unavailable, perform non-contrast CT head to exclude hemorrhage 6
- CT angiography (CTA) or MR angiography (MRA) from aortic arch to vertex must be completed within 24 hours to identify large vessel occlusion requiring thrombectomy 2, 6
Critical Management Considerations
Time-sensitive treatment decisions:
- Evaluate for intravenous thrombolysis (tPA) if presenting within 4.5 hours 1
- Assess for endovascular thrombectomy if large vessel occlusion is confirmed on CTA 6
- Patients with large MCA infarctions (especially under age 60) may require decompressive hemicraniectomy for malignant cerebral edema 2
Common pitfall to avoid: Do not mistake this presentation for peripheral facial palsy (Bell's palsy). The presence of contralateral body weakness immediately distinguishes brainstem or hemispheric stroke from peripheral facial nerve pathology 5, 7.