Utility of daily supervised hyperventilation during long-term video-EEG monitoring

Hyperventilation (HV) is most effective in activation of generalized absence seizures during routine EEG studies. It is also used as an activation technique in the epilepsy monitoring unit, with limited data on its utility. This prospective study was undertaken to determine the effectiveness of daily hyperventilation sessions in precipitating events in the epilepsy monitoring unit. The authors performed hyperventilation for 3 minutes on a daily basis on patients admitted to our epilepsy monitoring unit. They considered events to be activated by HV if they occurred during or within 3 minutes of the procedure. They asked the patient if the precipitated event was typical, and compared the precipitated events to those that occurred spontaneously during the monitoring period. They evaluated 79 consecutive patients; 54 had localization related epilepsy, 24 had psychogenic nonepileptic events only, and 1 patient had spells of unknown nature. Six patients with epilepsy had epileptic seizure activation (three auras, two complex partial seizures and one secondarily generalized tonic clonic seizures), and eight patients with nonepileptic spells had precipitation of nonepileptic events. Two patients with both epilepsy and psychogenic nonepileptic events had a nonepileptic event activated. Spontaneous and activated epileptic seizures did not differ in their clinical characteristics. Daily supervised HV is effective in inducing partial seizures as well as psychogenic nonepileptic events in the epilepsy monitoring unit. Daily HV may be effective in shortening the duration of video EEG monitoring, consequently reducing its cost.