The very occurrence of PLEDs (periodic lateralized epileptiform discharges) especially in Frontal region is suggestive of an epileptic state.

However, epilepsy is a clinical diagnosis; hence, clinical history is important in labeling the EEG findings as epileptogenic, otherwise in absence of clinical history of epileptic attacks, epileptiform discharges is a better term in my opinion.

The morphology , frequency , spread etc of the periodic epileptiform discharges (PLEDs, LPDs or GPDs) are by themselves not very specific for epileptogenicity. This is the reason the new ACNS definitions opted to leave the 'E' out in the terms and opted for LPD, GPD etc.

A frequency higher than 2-3 Hz might raise the suspicion of underlying epileptogenicity.

A pragmatic approach would be to do long-term continuous EEG monitoring or at least serial EEG's to see if there is evolution in the PLEDs characteristics, or if electrographic seizures occur. Some features like the occurrence of RDs ( rhythmic after discharges) may herald the occurrence of focal seizures in patients with PLEDs ( see Reiher J et al, Electroencephalogr Clin Neurophysiol 1991;78:12-17). The associated etiology may also help ( higher incidence of seizures in HSV and other CNS infections and lower incidence in aetiologies like stroke). Also important is the associated EEG background activity. Since the aim of the presumptive treatment of PLEDs ( considering it to be an preictal or postictal state) using AED would be to prevent further seizure associated brain injury in an already compromised/sick brain, we could argue that the brain dysfunction or injury should be in a potentially reversible stage. This assumption would exclude patients expressing GPDs or LPDs after severe HIE ( post cardiac arrest etc) on a severely suppressed/flat EEG background, from being treated with antiepileptic drugs.

PLEDs are not highly specific of epilepsy, they occurr more often in acute lesions, like herpes encephalitis, large stroke etc. They may indeed sometimes be the correlate of a status epilepticus.

They are lateralized and may indeed not be as sharp as spikes or sharp waves. They are rhythmic, but their frequency may wax and wane. Also, they do not attenuate under eye opening or other stimuli.

If there is any difference between both, I'd like to know also. The question refers to both conditions.

in general: EEG patterns that resemble those seen during some

epileptic seizures, but are perceived neither by the patient

nor by the observer (sometimes inappropriately

called “subclinical seizures”), are not defined as epileptic

seizures. However, the clinician should be aware that that

more careful observation or interaction may reveal previously

missed subtle behavioral correlates of the EEG

changes.

I agree with the above mentioned opinion that epilepsy is a clinical diagnosis and the previous history as well as family history of the patient is very important. We will not treat an EEG with no history of abnormal behaviour or sezures. We treat patients! Even more a normal EEG does not exclude the diagnosis of Epilepsy.

Sygkliti Henrietta Pelidou, Ass Prof. in Neurology, University of Ioannina, Greece

Actually, the question was about a specific electroencephalographic finding (periodic discharges) and its eventual relationship with epileptic seizures.