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.