Cyclic seizures with automatisms occurring during non-convulsive status epilepticus with lateralized periodic discharges caused by hyponatremia

Lateralized periodic discharges (LPDs) have been known to be one of the ictal electroencephalography (EEG) activities in non-convulsive status epilepticus (NCSE). Cyclic seizures represent a special form of status epilepticus in which seizures recur at regular intervals. We treated a patient who suffered from NCSE with LPDs which developed under hyponatremia. The patient showed cyclic seizures with automatisms during NCSE. The cyclic seizures were associated with high-frequency rhythmic discharges on EEG, and the NCSE was associated with LPDs. Our patient showed that cyclic seizures with motor symptoms can occur on the background of NCSE with LPDs. The rhythm of LPDs abruptly changed at the initiation and the ending of the seizures, implying the possibility of replacement of one pacemaker by another pacemaker, which triggers seizures associated with the ictal high-frequency rhythmic activities. We discuss the pathophysiology underlying the evolution of these two types of seizures.