Effect of glycerol on ischemic edema evaluated by somatosensory evoked potentials

Glycerol is administered to reduce intracranial pressure by clinically enhancing cerebral edema. In this study, the effect of glycerol on ischemic edema was evaluated in 34 cerebral infarct patients by serial SEP. Evoked potentials were obtained by stimulating the hemiparetic median nerve 60 times with duration of 0.1 msec. N20 wave of SEP was analyzed by signal processor. SEP was monitored every 30 min for 3 hr after glycerol administration. Improvements of CCT, which means interpeak latency between N13 and N20, were observed in 14 patients. In seven patients, N20 waves were observed after IV administration of glycerol even though N20 waves were not observed before glycerol administration. The patients in acute stage or with the small infarction of basal ganglia showed these electrophysiological improvements. No CCT changes were observed in nine patients, and no N20 waves were obtained in two patients even after glycerol administration. In conclusion, electrophysiologically, glycerol effect on ischemic edema was well recognized in acute staged infarct patients and the patients with small infarction of basal ganglia.