Periodic Slow Waves Presenting as Ictal Electroencephalography Findings in Complex Partial Status Epilepticus

The diagnosis of nonconvulsive status epilepticus (NCSE) largely relies on electroencephalography (EEG) findings, but the existing diagnostic criteria for EEG results are sometimes inconsistent. Much debate has centered on periodic epileptic discharges (PEDs) and their relationship with seizures. The recently published Salzburg Consensus Criteria for diagnosis of NCSE, which consider PEDs to be ictal findings under several conditions, have been proven to have high diagnostic accuracy. However, the criteria do not include periodic slow waves (PSWs) and do not consider these as overall ictal electrographic changes. Here, we report 2 cases of complex partial status epilepticus in which routine EEG showed PSWs without epileptiform activity during the clinical ictal phase. Both patients were elderly males who had histories of seizures and presented with impaired consciousness and signs such as aphasia or tongue automatism that indicated a temporal lobe origin. After we administered antiepileptic drugs (AED), the clinical signs and periodic EEG slow waves disappeared. These cases show that PSWs may appear as ictal electrographic changes in NCSE. When PSWs accompany clinical signs suggestive of NCSE, they should be considered ictal findings, and physicians should administer AED.