Does hyperventilation elicit epileptic seizures?

PURPOSE Voluntary hyperventilation has been advocated for many decades as an "activating" procedure to provoke clinical seizures and epileptiform discharges in subjects with suspected epilepsy who undergo standard EEG recordings. This study was undertaken to determine the effects of hyperventilation in patients with proven epilepsy. METHODS We examined the records of 433 consecutive patients with proven epilepsy, as documented by long-term video-EEG studies. The patients underwent 5 min of voluntary hyperventilation during standard EEG recordings. All EEGs were interpreted by board-certified electroencephalographers. The patients ranged in age from 10 to 64 years; 384 (88.7%) had localization-related and 48 (11.3%) generalized epilepsy syndromes. RESULTS Hyperventilation was associated with a clinical seizure in two (0.46%) of the subjects (partial seizures in both cases). Interictal epileptiform discharges were interpreted as showing in increase in frequency during hyperventilation in 19 (4.4%) patients, when compared with the baseline EEG. CONCLUSIONS Voluntary hyperventilation in patients with unequivocal epilepsy is rarely associated with either clinical seizures or an increase in frequency of epileptiform discharges.