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 . . .