Objective      To explore the changes of preoperative and postoperative electroencephalograms of video-electroencephalography (V-EEG) in monitoring fourth ventricular tumor resection in order to found an electrophysiological basis to diagnose or differential diagnose early postoperative epilepsy caused by fourth ventricular tumor.       Methods      Preoperative and postoperative EEG and clinical characteristics of 23 patients with fourth ventricular tumor in our hospital from Jan. 2009 to Dec. 2011 were retrospectively analyzed.       Results      These 23 patients all had hydrocephalus at various degrees but no history of seizures before surgery. Preoperative EEG displayed there were 9 patients of normal EEG

8 of increased sporadic slow waves in all electrodes

and 6 of paroxysmal rhythmic slow waves. Hydrocephalus was obviously alleviated after surgery. Perioperative EEG indicated that 16 patients with background moderation and slower EEG frequencies

3 patients with background moderation

synchronous rhythmic slow wave and sporadic single suspicious negative sharp wave/sharp slow wave but with no epileptic seizure after continuous observation

4 patients with synchronous rhythmic slow wave and sporadic bursts of spike/multi-spike slow waves

and 1 patient with eyelid twitching and 3 patients without obvious clinical seizures

but with various disturbance of consciousness observed by video. Consciousness improved significantly after antiepileptic treatment.       Conclusion      V-EEG monitoring is useful to diagnose or differential diagnose early postoperative epilepsy

especially non-typical seizures.