VARIABLE CEREBRAL-DYSFUNCTION DURING TILT INDUCED VASOVAGAL SYNCOPE

Electroencephalographic (EEG) monitoring was performed during head-up tilt testing (HUT) in a group of 63 consecutive patients (27 males, 36 females, mean age 41.5 years) with a history of recurrent syncope of unknown origin despite extensive clinical and laboratory evaluation. S yncope occurred in 27/63 patients (42.8%) during HUT and was cardioinh ibitory in 11/27 (40.7%) and vasodepressor in 16/27 (59.3 %). All pati ents with a negative response to HUT had no significant EEG modificati ons. In patients with vasodepressor syncope a generalized high amplitu de 4-5 Hz (theta range) slowing of EEG activity appeared at the onset of syncope, followed by an increase in brain wave amplitude with a red uction of frequency at 1.5-3 Hz (delta range). The return to the supin e position was associated with brain wave amplitude reduction and freq uency increase to 4-5 Hz, followed by restoration of a normal EEG patt ern and arousal (mean total duration of syncope 23.2 s). In patients w ith cardioinhibitory syncope, a generalized high amplitude EEG slowing in the theta range was noted at the onset of syncope, followed by a b rain wave amplitude increase and slowing in the delta range. A sudden reduction of brain wave amplitude ensued leading to the disappearance of electroencephalographic activity (''flat'' EEG). The return to the supine position was not followed by immediate resolution of EEG abnorm alities or consciousness recovery, both occurring after a longer time interval (mean total duration of syncope 41.4 s). EEG monitoring durin g HUT allowed the recording and systematic description of electroencep halographic abnormalities developing in the course of tilt induced vas ovagal syncope.