Hyperventilation and Epileptic Seizures

Abstract

To the Editor: The article by Holmes et al. (1) on hyperventilation (HV) and seizures concludes that their findings “provide compelling evidence that both localization-related and generalized epilepsies are relatively resistant to routine HV activation in adults and adolescents.” I disagree with their interpretation. Absence of a witnessed clinical or electrographic seizure, especially with a retrospective study, does not imply that epilepsies are resistant to HV. We often use HV when attempting ictal single-photon emission computed tomography (SPECT) scan in our hospitalized telemetry patients and have been doing so for the last several years. Of the last 40 to 50 patients who underwent HV, seizures were personally witnessed in three to four patients (unpublished data). These were all adult patients with localization-related epilepsies. Seizures can occur during HV or a few minutes after the procedure. This is significantly contradictory to the numbers provided by the author. While conducting routine EEGs, the technologists encourage a good effort with HV but may not consistently get ideal results. Second, HV by technologists is not aimed at provoking a seizure but rather at unmasking epileptiform activity. Therefore a trained technologist will often stop HV if a suspicion exists that the patient is about to seize. Based on the observation of Holmes et al., it would be more appropriate to conclude that seizures are very infrequently witnessed during routine HV. However, this does not provide “compelling evidence” that epilepsies are relatively resistant to this procedure.