Periodic lateralized epileptiform discharges (PLEDs) had been debated whether it is ictal or non-ictal phenomenon. As mostof PLEDs occur in patients with acute structural lesions, some epileptologists prefer PLEDS as a non-ictal phenomenon,rather an obscure epiphenomenon of etiological diseases. But, almost half of the patients with PLEDs do not have acutestructural lesions in the brain and metabolic disorders or old CNS lesions may cause PLEDs and even more, no brain lesionwas identified in some patients. There are many data supporting PLEDs as ictal phenomena. Occurrence of PLEDs usuallyaccompanied by decreased mentality and is improved as PLEDs disappeared. Current SPECT study showed marked hyperperfusionin the lesion side of PLEDs, that is striking evidence of PLEDs as ictal phenomena. Also careful review of EEGwith PLEDs revealed it is a dynamic process rather than a static state. Despite of these evidences, as PLEDs are an end-stageof animal status epilepticus models, it may be a transition of ictal to interictal state.

Although the pathophysiologic mechanism is unknown, there has been long-running debate on whether periodic discharges suchas periodic lateralized epileptiform discharges (PLEDs) and generalized periodic epileptiform discharges are an ictal or interictalEEG pattern. The goal of this review is to give evidence that such periodic discharges on EEG are not ictal phenomenon and justrepresent underlying acute brain damage. This review includes coma with epileptiform EEG pattern and its prognostic andtherapeutic implications. Based on previous reports, rather than taking the view PLEDs represent either an underlying ictal processor an electrographic correlate of neuronal injury, it would be more reasonable that PLEDs are considered as a dynamicpathophysiological state in which unstable neurobiological processes create an ictal-interictal continuum.