Study sheds light on postictal generalised EEG suppression

By Eleanor McDermid, Senior medwireNews Reporter

A study in Neurology finds postictal generalised EEG suppression (PGES) to be more common in patients who are not given prompt oxygen, and after type 1 generalised convulsive seizures (GCS).

The analysis of video-EEG recordings of 417 patients with drug-refractory epilepsy from the prospective REPO₂MSE study shows that PGES was 14.2 times more likely to occur if oxygen was not given early (during seizure or within 5 seconds of its end). This association was independent of confounding variables, implying that prompt oxygen administration could be a powerful preventive tool.

However, editorialists Orrin Devinsky (NYU School of Medicine, New York, USA) and Lina Nashef (King’s College Hospital, London, UK) caution that the study could not control for “whether oxygen was key, or the accompanying actions such as repositioning, suctioning, or stimulation.”

They add: “The lower SUDEP [sudden death in epilepsy] rates in the community with supervision in sleep suggest that oxygen may not be the critical intervention.”

The editorialists note that oxygen administration after a seizure is not recommended at home, despite being routine in many hospitals. They say this may need to be reconsidered, although they stress that “the evidence does not at this stage support adoption of its widespread use in the community.”

The other factor influencing PGES likelihood was seizure type. It occurred after 65% of type 1 seizures (tonic–clonic GCS with bilateral and symmetric tonic arm extension), 48% of type 3 (unilateral or asymmetric tonic arm extension or flexion) and 15% of type 2 seizures (clonic GCS without tonic arm extension or flexion).

After accounting for confounders, PGES was 66.0-fold more likely to occur after a type 1 seizure and 21.5-fold more likely to occur after a type 3 seizure, relative to after a type 2 seizure.

Sylvain Rheims (Hospices Civils de Lyon and Lyon 1 University, France) and study co-authors investigated type 1 seizures further, finding that the risk of PGES after this type of seizure was increased a significant fivefold if the patient was asleep at the time and 13.4-fold if oxygen was not promptly administered.

The researchers caution that neither type 1 seizures nor lack of early oxygen administration were associated with the duration of PGES, which in turn has been associated with SUDEP, so the effect of these factors on SUDEP remains unknown.

But the editorialists say that, nonetheless, “the findings of this study help us better understand the mechanisms by which risk factors operate, refining (type of GCS) and weaving (seizure type, sleep, lack of intervention, position) them into a probabilistic model of SUDEP.”

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