Cerebrovascular reactivity over time course in healthy subjects

IntroductionCerebrovascular reactivity (CVR) reflects the compensatory dilatory capacity of cerebral arterioles to a dilatory stimulus and is an important mechanism for maintaining constant cerebral blood flow. Many pathological conditions are associated with an impaired CVR thus contributing to a higher risk of cerebrovascular disease. Since an impaired CVR might contribute to a cerebrovascular disease if it lasts for a longer period of time, it is of importance to know what the time-course of CVR might be under healthy conditions.MethodsWe investigated CVR in 33 healthy subjects on baseline and on follow-up after 1 to 3 years. CVR was determined by calculating the difference between maximal blood flow velocity after stimulation with acetazolamide and during rest. Blood flow velocities were measured by transcranial Doppler ultrasound.ResultsCVR did not differ significantly in a group of healthy persons when reevaluated after 1 to 3 years. Possible influencing factors like age, gender, interval between testing, and smoking did not show a significant influence.DiscussionThis is the first study to investigate within-subject-differences in healthy subjects. CVR seems to remain constant under healthy conditions. Even this short period of life-span is of importance because an altered CVR can improve under treatment within weeks. Nevertheless further studies should follow-up longer periods of time.