Abstracts

Hyperventilation (HV) provokes a physiological slowing of the brain rhythms and activation of discharges and seizures. Classically, the effect is more pronounced in idiopathic generalized epilepsies and rarely produced in other types of epilepsies. However, since the 70[apos]s the attention has been drawn to the fact that the activation of focal clinical seizures should not be as rare as thought earlier. The aim of this study was to determine the value of HV in induction of focal seizures in a video-EEG monitorization setting.
We retrospectively evaluated the spontaneous and HV activated seizures of those patients who had at least one activated seizure.
Out of 102 patients submitted to video-EEG monitoring for evaluation of drug-resistant focal epilepsy, 24 (23.5%) had seizures induced by HV. The proportion of patients with activated seizures was greater in temporal lobe epilepsy since 18 out of 63 patients (28.6%) presented activated seizures compared with 1/21 frontal (4.8%), 1/5 parietal, none of 7 occipital and 4/6 multilobar. The induced seizures reached a maximum at 4 minutes of HV and declined significantly thereafter. The activation of seizures was independent of the degree of background slowing. The activated seizures had similar characteristics of those spontaneous in terms of clinical manifestations, EEG recording and generalization rate. Ictal SPECT performed during HV induced seizures, demonstrated hyperperfusion regionalized to the lobe of seizure origin.
About 1/5 of the patients with focal epilepsy and 1/3 of the temporal lobe ones had HV activated seizures. HV is an important tool in evaluation of patients with refractory focal epilepsy since the time spent in a video-EEG monitoring unit could be cut down in this way, a simple and safe method of activation. In this particular circumstance, the maneuver duration must be stressed as at least 4 minutes.