Cerebral hemodynamic response to generalized spike-wave discharges

Purpose: Data in the literature concerning metabolic demand during generali zed spike-wave activity (gSW) are conflicting. We investigated instantaneou s changes in cerebral blood flow velocities (CBFV) in both middle cerebral arteries (MCAs) by transcranial Doppler sonography (TCD) during gSW paroxys ms recorded by scalp EEG. Methods: In 13 patients, CBFVs in both MCAs were averaged, time-locked to t he occurrence of the gSW; respiratory rate (RR) and end-expiratory pco(2) w ere measured in one patient. Results: Nine patients showed significant changes in CBFV during gSW. Four had biphasic flow changes with an initial increase (p < 0.05) and a subsequ ent decrease (p < 0.01). This was partially paralleled by an increase in RR (p < 0.01) and a decrease in pco(2) (p < 0.01). In three patients, an incr ease in CBFV that preceded the onset of gSW by several seconds was observed , followed by a decrease in CBFV. Two patients showed a significant decreas e only of CBFV. Only gSWs of a median duration of >0.8 s were associated wi th significant changes in CBFV. Conclusions: We were able to demonstrate that gSWs of several seconds durat ion lead to cortical perfusion changes. We suggest that the initial increas e of CBFV demonstrated in some patients reflects neuronal activation, where as the subsequent decrease might in part be due to hyperventilation-induced hypocapnia.