Middle Cerebral Artery Stroke
MCA stroke is the most common type of ischemic stroke, affecting the lateral cerebral hemisphere. It causes contralateral motor and sensory deficits (face and arm > leg), and when affecting the dominant hemisphere, aphasia. Understanding the vascular territories is essential for localizing strokes.
Anatomical Basis
The MCA supplies the lateral surface of the cerebral hemisphere, including the motor and sensory cortices for the face and upper limb (homunculus), Broca's and Wernicke's areas (dominant hemisphere), and the internal capsule (lenticulostriate branches). The leg representation is on the medial surface (ACA territory).
Relevant Structures
Mechanism
Thrombotic: Atherosclerosis at MCA origin or proximal segment. Embolic: Cardiac source (atrial fibrillation, valve disease) or carotid artery plaque. Risk factors: Hypertension, diabetes, smoking, hyperlipidemia, atrial fibrillation.
Clinical Presentation
- âĒContralateral hemiparesis (face and arm > leg)
- âĒContralateral hemisensory loss (face and arm > leg)
- âĒAphasia if dominant hemisphere (usually left)
- âĒBroca's aphasia: Non-fluent, impaired expression, relatively preserved comprehension
- âĒWernicke's aphasia: Fluent but nonsensical speech, impaired comprehension
- âĒGlobal aphasia: Both expression and comprehension impaired
- âĒNeglect if non-dominant hemisphere (usually right)
- âĒGaze deviation toward the lesion (eyes "look at the lesion")
Physical Examination
- âContralateral face and arm weakness (leg relatively spared)
- âUpper motor neuron pattern: increased tone, hyperreflexia (may be absent acutely)
- âContralateral sensory loss to all modalities
- âVisual field cut (homonymous hemianopia)
- âAssess language function (naming, repetition, comprehension, fluency)
- âTest for neglect (line bisection, extinction to double simultaneous stimulation)
Treatment
- âIV thrombolysis (tPA/alteplase): Within 4.5 hours of symptom onset (with criteria)
- âMechanical thrombectomy: For large vessel occlusion up to 24 hours in selected patients
- âAdmit to stroke unit
- âAspirin after hemorrhage excluded (and after 24h if tPA given)
- âBlood pressure management
- âSecondary prevention: Antiplatelets, statins, anticoagulation if cardioembolic, risk factor control
Prognosis
Depends on infarct size and treatment timing. Thrombolysis/thrombectomy significantly improve outcomes if given early. Large MCA territory infarcts have high mortality. 30-day mortality ~10-15%. Long-term disability common.
Study Tips
- ðĄMCA = face and arm (lateral cortex); ACA = leg (medial cortex)
- ðĄDominant hemisphere (usually left) MCA stroke = aphasia
- ðĄNon-dominant (usually right) = neglect syndrome
- ðĄ"Eyes look at the lesion" in MCA stroke (frontal eye field damaged)
- ðĄLenticulostriate branches supply internal capsule - small lacunar strokes cause pure motor hemiparesis
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Common questions about this condition
The motor homunculus shows the leg represented on the medial surface of the cortex, which is supplied by the anterior cerebral artery (ACA). The MCA supplies the lateral cortex where the face and arm are represented. This is why MCA stroke causes face and arm weakness greater than leg.
Malignant MCA syndrome occurs with large MCA territory infarctions, causing severe cerebral edema, herniation, and high mortality (up to 80%). It typically occurs in younger patients with complete MCA occlusion and minimal collateral flow. Decompressive craniectomy can be life-saving.