Middle cerebral artery syndrome

Overview

Middle cerebral artery syndrome refers to a collection of neurological deficits resulting from the occlusion or damage of the middle cerebral artery (MCA), one of the three major paired arteries that supply blood to the brain. The MCA is the largest branch of the internal carotid artery and supplies vast areas of the cerebral cortex, including the frontal, temporal, and parietal lobes, as well as the basal ganglia and internal capsule through its deep branches.

When the MCA is blocked—most commonly by a clot or embolus—it leads to an ischemic stroke in the territory it supplies. Because of the extensive area the MCA perfuses, an infarction here can result in significant impairments in motor and sensory function, speech, vision, and cognition, depending on the hemisphere involved and the specific branches affected. MCA syndrome is one of the most common types of stroke syndromes encountered in clinical practice.

Causes

Middle cerebral artery syndrome is most often caused by an ischemic stroke resulting from the blockage of the MCA or one of its branches. Less commonly, it may result from hemorrhagic stroke or other vascular pathologies. Common causes include:

• Thrombotic stroke: Formation of a blood clot within the MCA due to atherosclerosis

• Embolic stroke: A clot or embolus that originates elsewhere, such as the heart (e.g., in atrial fibrillation), and lodges in the MCA

• Cerebral artery dissection: A tear in the artery wall that causes narrowing or blockage

• Intracerebral hemorrhage: Bleeding into the brain tissue, which may compress the MCA

• Vasculitis: Inflammation of blood vessels leading to narrowing and potential thrombosis

Risk factors for MCA syndrome include hypertension, diabetes, hyperlipidemia, smoking, atrial fibrillation, and a history of previous stroke or transient ischemic attack (TIA).

Symptoms

The symptoms of middle cerebral artery syndrome depend on the hemisphere affected (left or right), the extent of the occlusion (proximal vs. distal), and whether the dominant or non-dominant hemisphere is involved. General signs and symptoms include:

Common Symptoms (Either Hemisphere)

• Contralateral hemiparesis (weakness) affecting the face, arm, and to a lesser extent the leg

• Contralateral hemisensory loss (reduced sensation)

• Homonymous hemianopia (loss of the same visual field in both eyes)

• Gaze preference toward the side of the lesion (especially in large infarcts)

Left MCA Syndrome (Dominant Hemisphere in Most People)

• Aphasia (language deficits), which may be expressive (Broca’s), receptive (Wernicke’s), or global

• Impaired reading, writing, and speech comprehension

• Right-sided weakness and sensory loss

Right MCA Syndrome (Non-Dominant Hemisphere)

• Left-sided hemineglect (lack of awareness of the left side of the body and space)

• Spatial and perceptual deficits

• Left-sided weakness and sensory loss

Severe MCA strokes, especially when involving the proximal MCA trunk, can cause large territory infarctions leading to cerebral edema, increased intracranial pressure, and potentially herniation if not treated promptly.

Diagnosis

The diagnosis of middle cerebral artery syndrome involves a combination of clinical assessment and neuroimaging. Key diagnostic steps include:

• Neurological examination: Detailed assessment of motor function, sensory perception, language, cognition, and visual fields

• CT scan: Non-contrast CT to rule out hemorrhage and detect early signs of infarction

• MRI of the brain: Diffusion-weighted imaging (DWI) is sensitive in detecting early ischemic changes

• CT or MR angiography: To visualize the occlusion in the MCA or its branches

• Carotid Doppler ultrasound: To assess blood flow and identify sources of emboli

• Cardiac evaluation: Including echocardiogram and ECG to detect embolic sources such as atrial fibrillation or cardiac thrombi

Prompt diagnosis is critical, as many treatment options are time-sensitive and must be initiated within a narrow therapeutic window.

Treatment

Treatment of MCA syndrome focuses on restoring blood flow, preventing complications, and initiating rehabilitation. Management depends on the timing of presentation and the nature of the stroke (ischemic vs. hemorrhagic). Common treatment approaches include:

Acute Ischemic Stroke Management

• Intravenous thrombolysis (tPA): Administered within 4.5 hours of symptom onset

• Mechanical thrombectomy: Endovascular clot retrieval within 6 to 24 hours in eligible patients with large vessel occlusion

• Antiplatelet therapy: Aspirin and/or clopidogrel for secondary prevention

• Anticoagulation: In patients with atrial fibrillation or cardioembolic stroke

Supportive and Preventive Measures

• Blood pressure management

• Control of blood glucose and cholesterol levels

• Lifestyle modifications (smoking cessation, diet, exercise)

Rehabilitation

• Physical therapy to improve motor function and mobility

• Occupational therapy to assist with daily activities

• Speech and language therapy for aphasia or communication difficulties

• Neuropsychological support for cognitive and emotional issues

Prognosis

The prognosis for patients with middle cerebral artery syndrome varies widely depending on the severity of the infarction, the location of the occlusion, the timeliness of treatment, and the presence of comorbidities. Factors influencing outcome include:

• Size and location of the infarct: Larger, proximal occlusions have worse outcomes

• Time to treatment: Early thrombolysis or thrombectomy significantly improves recovery

• Age and overall health of the patient: Younger patients tend to recover better

• Access to rehabilitation: Intensive post-stroke rehabilitation greatly enhances functional outcomes

Some patients may recover significant function with therapy, while others may have permanent disabilities. Severe MCA strokes, especially when untreated, can result in life-threatening complications or profound neurological deficits. Long-term support, including assistive devices and caregiver involvement, may be necessary in many cases.