Abstracts

Hyperventilation (HV) is used routinely to provoke absence seizures, but is less effective for precipitation of partial seizures. Hyperventilation may also be effective in precipitating nonepileptic seizures. This study was undertaken to determine the effectiveness of hyperventilation in consecutive patients undergoing prolonged video EEG monitoring. We prospectively used hyperventilation in consecutive patients admitted to our epilepsy monitoring unit for long-term video-EEG monitoring. Patients underwent 3 min of hyperventilation on a daily basis (1-6 days). We excluded children younger than 12 and mentally retarded individuals. We evaluated 56 consecutive patients. Their ages ranged from 12 to 85 years. 36 (66%) had localization-related epilepsy, 19 (34%) had nonepileptic spells, and one had both partial onset seizures and nonepileptic seizures. Events were activated in 5 patients with epilepsy (2 auras, 2 complex partial seizures and 1 secondarily generalized tonic clonic seizure), and in 9 patients with nonepileptic seizures (all were nonepileptic events). The patient with both epileptic and nonepileptic seizures had a nonepileptic spell activated. Spontaneous and activated epileptic seizures did not differ in their clinical characteristics. Voluntary HV is effective in inducing seizures as well as nonepileptic spells during monitoring. The effectiveness of HV in localization-related epilepsy was higher than expected, possibly due to increased seizure tendency from medication withdrawal. This study suggests that daily HV may be effective in shortening the duration of video-EEG monitoring, both in patients with epilepsy and those with nonepileptic seizures.