A comparison of transcranial Doppler and cerebral blood flow studies to assess cerebral vasoreactivity.

BACKGROUND AND PURPOSE The aim of this study was to determine the ability of transcranial Doppler ultrasonography when used to assess cerebral vasoreactivity. The results of this method were compared with regional cerebral blood flow measurements. METHODS Forty-three patients with symptoms suggesting cerebrovascular disease took part. Transcranial Doppler findings in the middle cerebral arteries were compared with regional cerebral blood flow in the corresponding perfusion territories before and after acetazolamide administration. RESULTS There was a significant positive correlation between the absolute increase in cerebral blood flow in milliliters per 100 g per minute and the percent increase in velocity (r = 0.63). The right-left, side-to-side difference of the acetazolamide response obtained by the two methods also showed a positive correlation (r = 0.80). Control limits obtained from healthy subjects were used for both the blood flow increase (absolute values and asymmetry in absolute values) and the velocity increase (percent increase and asymmetry in percent increase). The two methods then agreed in their evaluation of vasoreactivity in 74 (86%) of the 86 middle cerebral artery perfusion territories; 20 (23%) were assessed by both methods as having a reduced vasodilatory reserve. Eleven hemispheres with a slightly reduced regional cerebral blood flow response to acetazolamide were not detected by transcranial Doppler, whereas all territories with a marked reduction were identified by Doppler. Only one hemisphere with a normal cerebral blood flow increase after acetazolamide administration was assessed by Doppler as having reduced vasoreactivity. CONCLUSIONS Transcranial Doppler and the acetazolamide test may be used in clinical situations to assess cerebral vasoreactivity.