Impaired cerebral autoregulation in asymptomatic patients with carotid artery stenosis:: Comparison of acetazolamide-SPECT and transcranial CO2-dopplersonography

Purpose: The indication for operation in patients with asymptomatic high-grade carotid artery stenosis is still under debate. Since impaired cerebrovascular autoregulation is associated with an increased risk for ischaemic events, assessment of cerebral vascular reactivity might be a valuable selection criterion for surgery. The aim of our study was therefore to evaluate the incidence of impaired autoregulation in asymptomatic patients with acetazolamide-single photon emission computed tomography (ACZ-SPECT) and transcranial CO2-dopplersonography (CO2-TCD). Furthermore, both methods were compared in regard to results and clinical practicability. Methods: In 42 patients with high-grade (> 70%) asymptomatic carotid artery stenosis, cerebral perfusion and vascular reactivity were assessed with resting and ACZ-enhanced SPECT scans. In 31 of these patients the CO2 reactivity of cerebral perfusion was determined by TCD and expressed as normalized autoregulation reserve (NAR). Results: Cerebral perfusion was decreased in 14.3%. In ACZ-SPECT 26% and in CO2-TCD 28% revealed an impaired vascular reactivity. Conformity of both methods was high (K = 0.93). TCD was superior in practicability, but only applicable in 81% due to a missing temporal bone window for insonation. Conclusion: In accordance ACZ-SPECT and CO2-TCD could detect impaired vascular reactivity in a quarter of asymptomatic patients. Both TCD and SPECT could be of value for preoperative selection in this group of patients, whereby sonography is recommended for daily diagnostic work-up.