THE PHOTIC DRIVING EEG RESPONSE AND PHOTOREACTIVE CEREBRAL BLOOD-FLOWIN THE POSTERIOR CEREBRAL-ARTERY IN CONTROLS AND IN PATIENTS WITH EPILEPSY

Objectives: Instantaneous changes in blood flow velocities during visu al stimulation can be assessed by transcranial Doppler sonography (TCD ), Methods: We investigated the possible relationship between the char acteristics of photic driving in the EEG elicited by repetitive interm ittent photic stimulation and the photoreactive flow changes in the po sterior and middle cerebral artery (PCA, MCA) of 25 normal controls an d 25 patients with focal epilepsy, Cerebral blood flow velocities (CBF V) of the right PCA (P2 segment) and the left middle cerebral artery ( MCA) were measured using a 2 Hz transcranial Doppler device. Simultane ously, scalp EEGs were recorded. Results: During photic stimulation th e mean CBFV increase was 20.4 +/- 9.5% in the PCA of the controls (n = 132 stimulations) and 16.0 +/- 10.8% in epileptic patients (n = 150 s timulations, P < 0.01). During those stimulation series with a good EE G driving response (n = 203), the mean increase of CBFV in the PCA was 19.7 +/- 10.0%, as opposed to 14.4 +/- 10.5% during the stimulations with a poor EEG response (n = 79, P < 0.01). A good photic driving res ponse was associated with a higher increase of CBFV in the PCA than a poor one. The increase in CBFV of the PCA in normal controls was highe r than in patients with focal epilepsy. Conclusions: This may indicate that epileptic patients have a reduced coupling between neuronal acti vation and blood flow. (C) 1998 Elsevier Science Ireland Ltd. All righ ts reserved.