Grade CBF (ml/100g/min) EEG changes 0 35-70 Normal I 25-35 Loss in faster beta frequencies II 18-25 Slowing of background to 5-7 Hz (theta) III 12-18 Slowing to 1-4 Hz (delta) IV <8-10 Suppression of all frequencies with neuronal death (Cortical suppression)

Table 1: Morphologic and frequency changes in EEG correlating with reductions in cerebral blood flow (CBF) (modified from Composite data from Sharbrough et al. 1973, Ingvar et al. 1976, Astrup et al. 1981, Nagata et al. 1989, Jordan and Stringer 1991, Anita L Schneider et al. 2005).