Objective To explore the practical value of continuous video-electroencephalograph (VEEG) monitoring on differentiating the diagnosis between postoperative nonconvulsive encephalopathic status (PONES) and valproate-induced hyperammonemic encephalopathy (VHE),caused by using valproate,after a craniotomy.Methods Eight patients that underwent craniotomy and had problems with postoperative disturbance of consciousness were retrospectively analyzed.The common reasons for disturbance of consciousness were excluded by routine examinations,such as brain CT scan,electrocardiogram,electrolytic analysis,hepatic function,blood sugar analysis,blood gas analysis,etc.VEEG monitoring and detection on blood ammonia (BA) and valproate (VPA) drug concentration were detected.The patients were diagnosed as three PONES and five VHE.Then,the comparison of characteristics in the EEG changes for the two diseases was preformed.Results In the eight patients,three PONES patients' VPA drug concentration was slightly lower than the therapeutic dose,while their hepatic function and blood ammonia were in the normal ranges.VEEG monitoring showed that intermittent bursts of generalized epileptic discharge were taking place in the whole brain.When the VPA dose was increased,the patients' consciousness was improved significantly and VEEG showed a significant decrease on epileptic discharge.The five VHE patients had a significant increase in their blood ammonia concentration,while their hepatic function was in the normal range and VPA drug concentration was slightly higher than the normal range.EEG monitoring showed generalized inhibition on brain electrical activity and an increase of repetitive triphasic waves.When VPA treatment was stopped and arginine was given,the patients' blood ammonia concentration went down,and their EEG recovered to a normal rhythm while consciousness also recovered rapidly.Conclusions VEEG is a specific examination for diagnosing PONES,which provides great value on the diagnosis between PONES and VHE after a craniotomy.