Introduction: Many patients are referred to our epilepsy center for the differential diagnosis (DD) of sudden unexplained falls or loss of muscle tone with or without loss of consciousness (SUF). We prospectively evaluated a diagnostic protocol including an active orthostatic stress test in 115 patients. Patients: Evaluation included all consecutive patients referred for DD of SUF between 05/02 and 06/04 in whom syncope was a probable diagnosis. Patients had neurological and cardiological evaluation (incl. normal tilt-table test) without a definite diagnosis. Age was 12 to 88 years with a median of 36 years, 59 were female, 56 male. Methods: Evaluation included a meticulous history of falls, in nearly all cases an observer was interviewed. The AOST was performed in the video-EEG lab following 24–48h video-EEG with 10/20 scalp EEG + ECG electrodes (Neurofile XP, ITmed). Until 12/03, blood pressure was measured intermittently by an automatic device, since 2004 all 42 patients were evaluated with a non-invasive beat-to-beat blood pressure device (Task Force Monitor, CNSystems). After 15min lying supine the patients actively stood for 30min or until a spontaneous fall. Results: In 48 patients (42%) the AOST was classified as abnormal. In 31 patients (27%) a fall (24) or presyncope (7) occurred, comorbid epilepsy was present in 6, cataplexy in 1 of the patients. Of the 24 falls, 15 were classified as neurocardiogenic syncope and 9 as psychogenic (active falling, no changes in blood pressure or pulse). Presyncope was diagnosed when the patient became symptomatic (e.g., dizziness) and a significant change in blood pressure or heart rate occurred. Diffuse high amplitude theta or delta EEG activity was seen in 13/15 patients with neurocardiogenic syncope, 3/7 patients with presyncope, and 0/9 patients with psychogenic falls. In 17 other cases (15%) postural orthostatic tachycardia occurred. Discussion: The AOST is of great diagnostic value in selected patients during video-EEG. It is preferable to tilt-table test because of the more physiological situation, the high rate of psychogenic falls, and abnormal results in patients with previous normal tilt-table tests. The video can be shown to compare the documented fall with other falls. Conclusions: EEG is helpful in discriminating psychogenic falls from syncope with generalized EEG-slowing. Continuous measurement of blood pressure is necessary, since changes may be too short to be detected by intermittent measurements.
