Hyperventilation Revisited: Physiological Effects and Efficacy on Focal Seizure Activation in the Era of Video‐EEG Monitoring

Abstract

Summary:Purpose: Hyperventilation is an activation method that provokes physiological slowing of brain rhythms, interictal discharges, and seizures, especially in generalized idiopathic epilepsies. In this study we assessed its effectiveness in inducing focal seizures during video-EEG monitoring.Methods: We analyzed the effects of hyperventilation (HV) during video-EEG monitoring (video-EEG) of patients with medically intractable focal epilepsies. We excluded children younger than 10 years, mentally retarded patients, and individuals with frequent seizures.Results: We analyzed 97 patients; 24 had positive seizure activation (PSA), and 73 had negative seizure activation (NSA). No differences were found between groups regarding sex, age, age at epilepsy onset, duration of epilepsy, frequency of seizures, and etiology. Temporal lobe epilepsies were significantly more activated than frontal lobe epilepsies. Spontaneous and activated seizures did not differ in terms of their clinical characteristics, and the activation did not affect the performance of ictal singlephoton emission computed tomography (SPECT).Conclusions: HV is a safe and effective method of seizure activation during monitoring. It does not modify any of the characteristics of the seizures and allows the obtaining of valuable ictal SPECTs. This observation is clinically relevant and suggests the effectiveness and the potential of HV in shortening the presurgical evaluation, especially of temporal lobe epilepsy patients, consequently reducing its costs and increasing the number of candidates for epilepsy surgery.

Transient Increase in Epileptiform Discharges after the Introduction of Nasal Continuous Positive Airway Pressure in a Patient with Obstructive Sleep Apnea and Epilepsy

“…These decreased awakenings resulted in decreased relative hyperventilation, and thus, the GSWC frequency returned to the approximate baseline level. These findings were consistent with the fact that seizures are provoked by hyperventilation in some patients with generalized and focal epilepsy (17).…”

The efficacy of routine hyperventilation for seizure activation during prolonged video-electroencephalography monitoring

“…This theory suggests that hypocapnia leads to vasoconstriction and a reduction in the supply of oxygen, glucose and other necessary nutrients to the cerebral tissue. 16 On the contrary, single photon emission CT studies with EEG in the setting of HV showed a relationship between areas of interictal lateralized epileptiform discharges and a localized increase in regional cerebral perfusion in 12 patients who were affected by simple and complex partial epilepsy. 17 Also, a change in end-tidal partial pressure of carbon dioxide was not associated with increments in interictal spikes in patients who had temporal lobe epilepsy.…”

The Use of EEG in the Diagnosis of Childhood Epilepsy

“…Its true yield in focal epilepsies is controversial. Holmes et al suggested a rare association, whereas Guaranher et al found it to be both safe and effective [6,7]. Both authors found its use to be particularly effective during long-term studies in activating temporal lobe seizures.…”