Evaluation of the acetazolamide test. Vasoreactivity and cerebral blood volume

We evaluated the potential usefulness of the acetazolamide test by investigating whether acetazolamide vasoreactivity reflected the change in resting cerebral blood volume caused by compensatory vasodilation due to a decline in cerebral perfusion pressure.

We measured resting and acetazolamide-activated cerebral blood flow with a stable xenon-enhanced CT system and resting cerebral blood volume with the subtraction technique using contrast-enhanced CT in 30 patients with various diseases. These parameters were measured in the anterior, middle, and posterior cerebral arterial territories of both hemispheres separately. We evaluated the statistical relationships between resting cerebral blood volume and vasoreactivity in these three territories, and the significance of the correlations was tested by ANOVA/ANCOVA to adjust for the double entries.

Significant negative linear relationships were demonstrated between the resting cerebral blood volume and the change in cerebral blood flow, expressed as a percentage induced by acetazolamide activation, for the anterior (r = -.607, P = .0004), middle (r = -.551, P = .0015), and posterior (r = -.523, P = .0078) cerebral arterial territories and between the resting cerebral blood volume and the increase in cerebral blood flow (absolute values) for the anterior (r = -.512, P = .0164) and middle (r = -.523, P = .0001) but not the posterior (r = -.571, P = .0563) cerebral arterial territories.

The acetazolamide test appears to be useful for the investigation of compensatory vasodilation: the vasoreactivity can be calculated as the increased cerebral blood flow expressed as a percentage or an absolute value, which both reflect cerebral blood volume directly.