Brain Stress Test for Assessing Risk for Hemodynamic Stroke

Area of Science:

• Neurology
• Radiology
• Vascular Medicine

Background:

• Intracranial steno-occlusive disease (SOD) poses a stroke risk influenced by poststenotic vasodilatory reserve.
• Cerebrovascular reactivity (CVR) quantifies this reserve, crucial for assessing hemodynamic stroke risk.
• Assessing CVR using P_ETCO₂ stress and Blood Oxygen Level Dependent (BOLD) MRI is vital for managing SOD patients.

Purpose of the Study:

• To correlate cerebrovascular reactivity (CVR) measurements with the incidence of stroke in patients with symptomatic intracranial steno-occlusive disease (SOD).
• To evaluate the utility of CO₂-BOLD MRI CVR as a brain stress test for assessing cerebrovascular reserve.
• To determine if normal CVR in the presence of significant stenosis is associated with a low stroke risk.

Main Methods:

• Retrospective analysis of 100 consecutive patients with symptomatic intracranial SOD who underwent CVR testing.
• CVR measured as % BOLD MR signal intensity change per mmHg P_ETCO₂ increase.
• One-year follow-up to determine stroke incidence, with treatment guided by CVR results (optimal medical therapy or revascularization).

Main Results:

• 83 patients were included; 14 had normal CVR, and 69 had impaired CVR ipsilateral to the lesion.
• Overall stroke incidence was 4.8% (4/83), exclusively in patients with impaired CVR (4/69).
• No strokes occurred in patients with normal CVR (0/14); 86% of revascularized patients showed improved CVR and symptoms.

Conclusions:

• CO₂-BOLD MRI CVR effectively serves as a brain stress test for assessing cerebrovascular reserve.
• Impaired CVR is significantly associated with an increased incidence of stroke in intracranial SOD patients.
• Normal CVR, even with significant stenosis, indicates a low stroke risk, supporting its prognostic value.