What can Middle Cerebral Artery (MCA) stenosis cause?

Middle Cerebral Artery (MCA) Stenosis: Clinical Consequences and Outcomes

Middle cerebral artery stenosis can cause ischemic stroke, transient ischemic attacks, cognitive impairment, and neurological deficits with severity depending on stenosis degree, with patients having >70% stenosis at highest risk for adverse outcomes. 1

Neurological Manifestations

Focal Neurological Deficits

• Contralateral weakness (hemiparesis affecting face and upper limb more than lower limb)
• Sensory disturbances on the contralateral side of the body
• Speech/language problems (especially with left MCA stenosis)
• Visual field defects (homonymous hemianopsia)
• Neglect syndrome (particularly with right MCA stenosis)

Stroke Risk and Severity

• Annual stroke risk varies by stenosis severity:

  • <50% stenosis: Minimal hemodynamic abnormality with lower stroke risk 2
  • 50-74% stenosis: Delayed filling of MCA branches but no significant blood flow reduction 2
  • 75-99% stenosis: Significant flow depression and higher risk of large cerebral infarction 2

• The annual rate of stroke in symptomatic MCA stenosis can be as high as 6.6% 3

• Patients with MCA stenosis show greater initial stroke severity (higher NIHSS scores) and worse functional outcomes compared to those without 4

Hemodynamic Consequences

• Reduced cerebral blood flow in the affected territory 2
• Watershed infarcts may develop in severe stenosis (≥75%) 2
• Collateral circulation development may partially compensate for reduced flow
• Impaired cerebrovascular reactivity leading to compromised autoregulation

Systemic Complications

• Combined vascular events: The annual risk of composite outcomes (stroke, myocardial infarction, vascular death) is approximately 13.2% in symptomatic MCA stenosis 3
• Cognitive decline: May occur due to chronic hypoperfusion or multiple small infarcts
• Increased mortality: Table 3 in the AHA guidelines shows annual death rates of 3.3-7.7% for MCA disease 1

Risk Factors and Associated Conditions

MCA stenosis is associated with:

• Hypertension
• Diabetes mellitus
• Hypercholesterolemia
• Cigarette smoking
• Higher prevalence in Asian, Black, and Hispanic populations 1, 5

Prognostic Factors

The prognosis for patients with MCA stenosis depends on several factors:

1. Symptomatic vs. Asymptomatic:

   • Symptomatic MCA stenosis carries a worse prognosis with higher risk of recurrent stroke 6, 3
   • Asymptomatic MCA occlusion has a relatively benign course with annual composite outcome rate of only 2.2% 3

2. Degree of Stenosis:

   • Severe stenosis (>70%) significantly increases stroke risk 2
   • Hemodynamic effects become apparent at 50% stenosis and significant at 75% 2

3. Combined Stenosis:

   • Patients with both MCA and extracranial ICA stenosis have the worst outcomes with higher NIHSS scores, worse functional outcomes, and higher risk of stroke recurrence or death (HR 2.204,95% CI 1.440-3.374) 4

4. Time Since Symptom Onset:

   • Recent symptoms (within 6 months) indicate higher risk 7

Clinical Pitfalls to Avoid

1. Underestimating asymptomatic stenosis: While asymptomatic MCA stenosis has better prognosis than symptomatic, it still requires aggressive risk factor management 3

2. Overlooking combined stenosis: Always assess both intracranial and extracranial circulation as combined stenosis significantly worsens prognosis 4

3. Misattributing symptoms: Ensure symptoms correspond to the territory supplied by the stenotic artery 7

4. Neglecting modifiable risk factors: Aggressive management of hypertension, diabetes, and hypercholesterolemia is essential as these are strongly associated with MCA stenosis 1, 5

MCA stenosis represents a significant cause of stroke worldwide, with particular prevalence among Asian, African, and Hispanic populations. The clinical consequences range from asymptomatic disease to devastating stroke, with outcomes largely dependent on stenosis severity, symptom status, and presence of combined vascular lesions.