Aims: Strokes caused by hemodynamically significant internal carotid artery stenoses and occlusions are believed to be embolic or hemodynamic of origin. The aim of the study was to assess cerebral hemodynamic compromises of significant carotid artery stenosis of occlusion using vasodilatory testing (acetazolamide test) in asymptomatic and symptomatic patients.
Patients and methods: 36 patients with unilateral, hemodynamically significant carotid stenosis were investigated using transcranial Doppler acetazolamide-test. There were 12 asymptomatic and 24 symptomatic patients. The middle cerebral artery mean blood flow velocity was measured at rest and after intravenous injection of 1 g acetazolamide. The absolute mean blood flow velocities and the cerebrovascular reactivity was compared at the stenotic and non-stenotic side. In a further analysis the mean velocities and the cerebrovascular reactivity values of the stenotic side were compared. Results of acetazolamide test performed on 28 healthy volunteers were used as control values.
Results: There were no side-differences between the middle cerebral artery mean blood flow velocity and cerebrovascular reactivity values in the asymptomatic group. In the symptomatic group, however middle cerebral artery mean velocity and cerebrovascular reactivity after acetazolamide was significantly lower on the stenotic side, than on the non-stenotic one. Comparing the different groups non-stenotic sides did not differ to each other in their cerebral blood flow velocity and cerebrovascular reactivity. In the symptomatic patients, however, cerebral blood flow velocity and cerebrovascular reserve capacity after acetazolamide was lower, than that of the stenotic side of asymptomatic patients and controls.
Conclusions: The transcranial Doppler is a suitable method for detecting altered cerebral hemodynamics in significant carotid stenosis. Impaired cerebrovascular reactivity may refer to the impairment of cerebral autoregulatory mechanisms.