Occurrence of hyperventilation-induced high amplitude rhythmic slowing with altered awareness after successful treatment of typical absence seizures and a network hypothesis

Abstract

Highlights We show that typical absence seizures (AS) and hyperventilation-induced high amplitude rhythmic slowing (HIHARS) or HIHARS with Altered Awareness (HIHARSAA) can coexist in the same patient, but never at the same time. We found that alkalosis and dysfunction of the same neural network are involved in both AS and HIHARS. AS and HIHARS should be better recognized to avoid misdiagnosis and overtreatment. AS and HIHARS can coexist in the same patient, but never at the same time.

Respiratory alkalosis provokes spike-wave discharges in seizure-prone rats

“…Electrographically, HIHARS is distinct from spike-wave seizures insofar the EEG lacks epilepsy-associated spikes and resembles slow-wave sleep. Nonetheless, age-dependence and behavioral similarities between HIHARS and absence seizures exist ( Lum et al, 2002 ; Mattozzi et al, 2021 ), thereby supporting the hypothesis that HIHARS and spike-wave seizures borrow from overlapping neural circuit mechanisms ( Mattozzi et al, 2021 ). Indeed, while HIHARS and spike-wave seizures are clearly distinct EEG patterns, human spike-wave seizures observed during hyperventilation are subtly different from those occurring spontaneously ( Sadleir et al, 2008 ), perhaps a reflection of the contribution of EEG-slowing circuitry to spike-wave seizures; while largely similar, we also found some differences in WAG/Rij spike-wave seizure frequency during some manipulations.…”

Respiratory Alkalosis Provokes Spike-Wave Discharges in Seizure-Prone Rats

“…Recent work suggests that spike-wave seizures may limit or preclude the generation of HIHARs in children with absence epilepsy, thereby supporting the hypothesis that HIHARS and spike-wave seizures borrow from similar neural circuit mechanisms (Mattozzi et al, 2021). In this model, hyperventilation engages brain structures that initiate and/or support widespread, synchronous cortical activity.…”

“…Behaviorally, eye opening/staring and fluttering, as well as oral automatisms, are observed during both events, albeit with different frequencies (Lum et al, 2002). Finally, the mean latencies from the onset of hyperventilation to the onset of electrographic HIHARS in healthy children, or spike-wave seizures in absence patients, are also similar (Lum et al, 2002;Mattozzi et al, 2021).…”

“…Nonetheless, similarities between HIHARS and absence seizures exist. Both events are associated with children of the same age (Mattozzi et al, 2021). Behaviorally, eye opening/staring and fluttering, as well as oral automatisms, are observed during both events, albeit with different frequencies (Lum et al, 2002).…”