What is the anatomic location of a stroke presenting with left-sided weakness, left-sided numbness, and left facial droop?

Anatomic Location of Stroke

The stroke is located in the right cerebral hemisphere, specifically in the right middle cerebral artery (MCA) or right internal carotid artery (ICA) territory. 1

Neuroanatomical Localization

The presentation of left-sided body weakness, left-sided numbness, and left facial droop localizes to the right hemisphere because motor and sensory pathways cross (decussate) in the brainstem, causing contralateral deficits. 1, 2

Key Localizing Features:

• Left hemiparesis (body weakness): Results from damage to the right motor cortex or descending corticospinal tract in the right hemisphere 1, 3
• Left hemibody sensory loss: Indicates involvement of right sensory cortex or thalamus 1
• Left facial droop: Reflects damage to right facial motor cortex (upper motor neuron pattern affecting lower face contralaterally) 1, 2

Most Likely Vascular Territory:

The right middle cerebral artery (MCA) is the most common location for this clinical presentation, as it supplies the lateral cerebral hemisphere including motor and sensory cortex. 1, 2 The right internal carotid artery territory can produce identical symptoms since the MCA is its major branch. 1, 2

Critical Distinguishing Features to Assess

Evaluate for additional right hemisphere signs that help confirm localization and exclude other territories:

• Visual-spatial neglect or left-sided neglect: Highly specific for right hemisphere stroke 1
• Abnormal visual-spatial ability: Suggests right parietal involvement 1
• Right homonymous hemianopsia: Left visual field loss in both eyes indicates right occipital or deep temporal involvement 1
• Absence of aphasia: Language dysfunction would suggest left hemisphere involvement in right-handed individuals 1, 2

Excluding Alternative Localizations

Why This is NOT a Brainstem Stroke:

A brainstem lesion would produce ipsilateral facial weakness with contralateral body weakness (crossed findings), which is not present here. 3, 4 In this case, the facial droop and body weakness are on the same side (both left), confirming a supratentorial hemispheric lesion. 1, 2

Rare Exception to Consider:

While extremely uncommon, ipsilateral weakness from ipsilateral stroke has been reported in patients with previous contralateral strokes causing functional reorganization of motor pathways. 5 However, this is exceedingly rare and should not be the primary consideration without history of prior stroke.

Immediate Diagnostic Approach

Obtain urgent neuroimaging to confirm the diagnosis and identify large vessel occlusion:

• Non-contrast CT head: Minimum required imaging to exclude hemorrhage and identify early ischemic changes (hypodensity in right MCA territory, loss of gray-white differentiation, effacement of right lentiform nucleus) 1, 3
• CT angiography (CTA) from aortic arch to vertex: Essential within 24 hours to identify right ICA or MCA occlusion requiring endovascular thrombectomy 1, 2, 3
• MRI with diffusion-weighted imaging (DWI): Preferred if available, as it detects acute infarction within minutes and is more sensitive than CT for early ischemia 1, 2

Critical Management Implications

The right MCA territory location carries specific risks:

• Malignant cerebral edema: Large right MCA infarctions (>50% of MCA territory or >145 mL volume) can develop life-threatening swelling within 24-96 hours 1
• Decompressive hemicraniectomy: Should be considered early in patients under age 60 with large MCA infarctions to reduce mortality, with neurosurgical consultation obtained urgently 1
• Monitoring for herniation: Watch for declining consciousness, pupillary changes, or worsening neurological status indicating increased intracranial pressure 1

Common Pitfall to Avoid

Do not mistake central (upper motor neuron) facial weakness for peripheral (Bell's palsy). In stroke, the forehead is typically spared on the affected side due to bilateral cortical innervation of upper facial muscles, whereas Bell's palsy affects the entire ipsilateral face. 6 However, some cortical strokes can mimic peripheral facial palsy, making detailed neurological examination essential. 6