APPLICATION OF TRANSCRANIAL DOPPLER SONOGRAPHY TO EVALUATE CEREBRAL HEMODYNAMICS IN CAROTID-ARTERY DISEASE - COMPARATIVE-ANALYSIS OF DIFFERENT HEMODYNAMIC VARIABLES

Background and Purpose Transcranial Doppler sonography in combination with manipulation of cerebral resistance vessels is widely used to scr een patients with suspected intracranial hemodynamic disturbances. Max imal flow velocity (V-max), mean flow velocity (V-mean), cerebral puls atility index (CPi), and cerebral resistance index (CR(i)) have all be en used to describe cerebral hemodynamics. The present study examined CO2 reactivity of the above hemodynamic variables with respect to its variability between different age groups and its capability to discrim inate between normal and abnormal findings. Methods Absolute and relat ive CO2 reactivity of V-max, V-mean, CR(i), and CPi were determined in both hemispheres in 30 young and 37 elderly control subjects and in 2 45 consecutive patients with strictly unilateral symptomatic (n=101) o r asymptomatic (n=144) carotid artery disease (>80% stenosis or occlus ion). Results Hemispheric reactivities of V-mean, CR(i), and CPi were significantly age dependent. Hemispheric V-max reactivity and interhem ispheric differences of individual reactivities (except absolute CPi r eactivity) did not vary with age and could therefore be used to define normal values. Patient classification according to these values revea led different frequencies of subjects with pathological findings (3% f or hemispheric V-max reactivity, 5% to 7% for interhemispheric differe nces of V-max or V-mean reactivity, 39% and 45% for interhemispheric d ifferences of relative CR(i) and CPi reactivity, respectively). Conclu sions Hemispheric reactivities are less suitable to evaluate cerebral hemodynamics than interhemispheric differences, since most of the latt er do not vary with age. However, interhemispheric differences vary wi th respect to their discriminatory power. Power is low for interhemisp heric differences of V-max and V-mean reactivity, since the correspond ing frequencies of abnormal findings do not differ from the 5% frequen cy expected in the reference population (reference range defined as me an+/-2 SD). With respect to the discriminatory power, interhemispheric differences of relative CR(i) and CPi reactivity may be superior to o ther parameters.