Nonconvulsive Status Epilepticus (NCSE) is generally accepted as a change in behavior and mental processes related to the epileptic discharge and the continuation of epileptogenic activity without convulsive symptoms. Cognitive and behavioral abnormalities often appear during NCSE seizures, thus, it is common for psychiatrists to be consulted to deal with these states as psychiatric manifestations. In this article we reported a 30s years-old female with NCSE, who required hospitalization and had difficulties in diagnosis. Under the diagnosis of generalized epilepsy, various antiepileptic agents had been introduced, however, drug eruptions had been induced by several agents. With serious limitations in drug selection, her seizures had been insufficiently controlled. Prior to admission to our hospital, consciousness disturbance had been prolonged for about 6 days after multiple tonic-clonic seizures. At first, NCSE was taken into consideration. However, the possibility of NCSE was excluded because generalized slow waves were mainly observed without epileptogenic activities like sharps and spikes in electroencephalogram (EEG) and because consciousness disturbance was not improved by administration of oral diazepam. After hospitalization she was treated as a prolonged postical twilight state or a stupor due to psychosis in epilepsy. An apparent response to antipsychotics, followed by complication of aspiration pneumonia which requires intensive physical treatments, led to further delay of diagnosis. Several months later, the EEG examination revealed the alternation of consciousness consistent with the change in EEG abnormal activities. After this, adjustment of the antiepileptic drugs significantly reduced the frequency of consciousness disturbance, and other factors such as brain organic lesions were not identified, which finally resulted in a diagnosis of NCSE. While drug selection was limited due to drug eruptions by multiple agents, the seizures with conscious disturbance were significantly decreased by clobazam, and eventually almost vanished by perampanel. It is important in clinical practice to be aware that the NCSE could be one of the unmissable differential diagnoses when prolonged conscious disorder or higher brain dysfunction were manifested even if typical epileptogenic EEG findings such as spike-wave complex were absent.
 <Authors' abstract>