Evaluating middle cerebral artery collateral blood flow reserve using acetazolamide transcranial Doppler ultrasound in patients with carotid occlusive disease.

BACKGROUND

The objective of this study is to examine the utility of acetazolamide TCD ultrasound in the evaluation of MCA collateral blood flow reserve in patients with carotid occlusive disease.

METHODS

Acetazolamide TCD and cerebral angiography were performed for 28 carotid territories in 14 patients with carotid occlusive disease. The percentage change in mean blood flow velocity and PI in the MCA was measured before and after 1 g of acetazolamide was administered. The carotid territories were divided into groups according their angiographic findings: (1) mild/moderate (<70%) vs severe (> or =70%) extracranial carotid artery stenosis, and (2) active collateral blood flow to the MCA territory vs no collateral blood flow to the MCA.

RESULTS

After acetazolamide injection, the percentage increase in mean MCA velocity for mild/moderate vs severe carotid artery stenosis was 43% +/- 10% and 19% +/- 6%, respectively, indicating less collateral blood flow reserve in patients with severe stenosis (P = .04). The percentage decrease in the PI for MCA territories with vs without angiographic evidence of collateral blood flow was 4.6% +/- 4% and 16% +/- 3%, respectively (P = .04), indicating an exhausted vascular reserve in patients with evidence of active collateral blood flow on angiography.

CONCLUSIONS

A decrease in the PI after acetazolamide administration represents a safe and noninvasive indicator of limited collateral blood flow reserve to the MCA territory ipsilateral to an extracranial carotid stenosis. Further study into the role acetazolamide TCD has in the preoperative evaluation of these patients, including threshold values, is warranted.