Generalized Periodic Discharges

From Pedersen GL, et al. Prognostic value of periodic electroencephalographic discharges for neurological patients with profound disturbances of consciousness. Clinical Neurophysiology. 17 July 2012 [epub].

It seems that stroke isn’t the only neurological subspecialty developing technologies that we don’t exactly know how to apply in practice. In this week’s Green Journal, Foreman, et al. published a very interesting study of critically ill patients undergoing continuous EEG. They found 200 patients (4.5% of their population) whose reports mention “generalized periodic discharges” (GPDs), “generalized periodic epileptiform discharges”, “triphasic waves”, and similar findings. They matched these 200 patients to a controls of similar age, disease type, and level of consciousness.

GPDs were highly correlated with non-convulsive seizures and non-convulsive status epilepticus. They were not correlated with convulsive seizures or status. Most interesting, patients with GPDs had the same spectrum of outcomes as those without. Caveats to this are many and include the retrospective nature of the study, non-standardization of EEG terminology (not the authors’ fault–continuous EEG is relatively new), lack of data on the duration of GPDs (thanks, Dr. Kotloski) and lack of data on what treatments the patients received.

The most common underlying clinical diagnoses were toxic/metabolic encephalopathy, sepsis, and stroke. Clearly, GPDs are associated with widespread brain insults, but are they epileptic or not? Dr. Maganti and others view them as being on an ictal-interictal continuum. Here’s what Pohlmann-Eden et al. have to say about PLEDS, which seems reasonably applicable to GPDs as well:

Rather than taking the view that PLEDs represent either an underlying ictal process or an electrographic correlate of neuronal injury, we prefer to consider them as an electrographic signature of a dynamic pathophysiological state in which unstable neurobiological processes create an ictal-interictal continuum, with the nature of the underlying neuronal injury, the patient’s pre-existing propensity to have seizures, and the coexistence of any acute metabolic derangements all contributing to whether seizures occur or not.

It follows that, as usual, clinical judgment must be brought to bear in deciding whom to treat. Dr. Maganti:

I would treat these patients especially if they are occurring in the setting of acute neurological injury and not treat them if it is a patient with anonxic injury/multiorgan failure

Now, an unsurprising but very important additional finding of this study is that patients with GPDs had ICU stays that were 3 days longer and continuous EEG monitoring periods that were 4 days longer than the control patients. In other words, finding GPDs may lead to more aggressive and expensive treatment. Since GPDs were found in 4.5% of their patients, and it’s not clear when they should be treated, this is a non-trivial resource allocation issue. Our institution, like many others, is ramping up its continuous EEG monitoring capabilities. Get ready to start finding all kinds of interesting things . . .

About Justin A. Sattin

I'm a vascular neurologist and residency program director. I created this blog in order to share some thoughts with my resident and other colleagues, and to foster my own learning as well.
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2 Responses to Generalized Periodic Discharges

  1. Khalid says:

    This is an ongoing discussion with a lot of debate among epileptologists and neurointensivests who mainly suffer from this variability in reading those patterns and they get confused ” one day treat seizures and the next don’t treat as epilepsy attending change !”
    any way this is similar to the article we discussed last month with Dr. Rutecki which was published in Neurocritical care journal by Columbia group Ong et al. Impact of prolonged PEDs on coma and prognosis. it was retrospective and they reviewed cases with Persistent PEDS ” >= 5 day” intermittent < 5days , or no periodic epileptiform discharged " they lumped all the different patterns in it including PLEDS, GPD, biPEDS, etc , " and they concluded that persistent PED activity in comatose patients is associated with SIRPIDS " stimulus induced" and electrographic seizures but has NO impact of the likelihood of survival or recovery of consciousness. they did also report that those with PEDS were likely to be on multiple AEDs and longer stay and monitoring .
    and i think both brings us back to the question ? " what are those periodic discharges ? and where they come from ? " and to be honest so far i had no clear explanation . as those studies suggest that those just represent a reflection of the cortical injury rather than an epileptiform activity, the fact that we see them post stroke would suggest that. but on the other hand some read them as a stage of status epilepticus , but the question that also i dont know that answer to is that all studies showed that if you have PEDS you will be more likely to have electrographic seizures , but what does not make sense is why treating those seizures does not change the out come ?

    any way , i think this is a very interesting area of study and neuromonitoring continues to be impressive area . and i dont think those studies should be used against using the cEEG , although i might be biased here , but i think there are more data and utility of this tool especially in comatosed patients more than just detecting subclinical seizures.

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