Visually evoked blood flow response assessed by simultaneous two channel transcranial Doppler using flow velocity averaging

Abstract

Background and Purpose We assessed the influence of different visual stimuli and the reproducibility and habituation of evoked flow responses using simultaneous two-channel transcranial Doppler monitoring and flow velocity averaging. Methods We measured stimulus-related percentage changes in posterior cerebral, basilar, and middle cerebral artery blood flow velocities in 14 normal volunteers using stimulus-triggered velocity averaging. With a two-channel transcranial Doppler system, simultaneous measurements in two arteries (both posterior cerebral arteries and the basilar and middle cerebral artery) were taken using multiple-array light-emitting diodes applying flash stimuli. Both posterior cerebral arteries were monitored to assess reproducibility and habituation of the evoked response with repetitive measurements under unchanged conditions and to analyze the influence of different features of the visual stimulus. Results There was a distinctive increase in velocities resulting from visual stimuli in bo...