Differentiation of convulsive syncope and epilepsy with head-up tilt testing.

OBJECTIVE: To evaluate the usefulness of head-upright tilt table testing in the differential diagnosis of convulsive syncope from epileptic seizures in patients with recurrent idiopathic seizure-like episodes.

DESIGN: Prospective, nonrandomized study.

SETTING: Electrophysiology laboratory of a university hospital.

PATIENTS: Fifteen patients (8 men and 7 women patients; mean age, 29 +/- 20 years) with recurrent unexplained seizure-like episodes, unresponsive to antiseizure medication.

MEASUREMENTS: Head-upright tilt table testing with or without isoproterenol infusion. Five patients who were initially tilt positive had a second tilt test with continuous electroencephalographic (EEG) recording.

MAIN RESULTS: Syncope associated with tonic-clonic seizure-like activity occurred in six patients (40%) during the baseline tilt and in four patients (27%) during isoproterenol infusion (total positive tests, 67%). The EEG showed diffuse brain wave slowing (not typical of epileptic seizures) in five of five patients during the convulsive episode. All patients who had positive test results eventually become tilt table negative after therapy, and over a mean follow-up period of 21 +/- 2 months, no further seizure-like episodes have occurred.

CONCLUSION: Upright tilt table testing combined with isoproterenol infusion may be useful to distinguish convulsive syncope from epileptic seizures.