Electroencephalographic Correlates of Vasovagal Syncope Induced by Head-Up Tilt Testing

Abstract

Background and Purpose-We sought to determine whether the introduction of EEG monitoring during head-up tilt testing could significantly improve the understanding of the cerebral events occurring during tilt-induced vasovagal syncope and the potential danger to the patient of this diagnostic procedure. Methods-EEG monitoring was performed during head-up tilt testing in a group of 63 consecutive patients (27 males and 36 females; mean age, 41.5 years) with a history of recurrent syncope of unknown origin despite extensive clinical and laboratory assessment. Results-Syncope occurred in 27 of 63 patients (42.8%) during head-up tilt testing and was found to be cardioinhibitory in 11 of 27 (40.7%) and vasodepressor in 16 of 27 (59.3%). All patients with a negative response to head-up tilt testing showed no significant EEG modifications. In patients with vasodepressor syncope, a generalized high-amplitude, 4-to 5-Hz (theta range) slowing of EEG activity appeared at the onset of syncope, followed by an increase of brain-wave amplitude with the reduction of frequency at 1.5 to 3 Hz (delta range). The return to the supine position was associated with brain-wave amplitude reduction and frequency increase to 4 to 5 Hz, followed by restoration of a normal EEG pattern and arousal (mean total duration of syncope, 23.2 seconds.). In patients with cardioinhibitory syncope, a generalized high-amplitude EEG slowing in the theta range was noted at the onset of syncope, followed by a brain-wave amplitude increase and slowing in the delta range. A sudden reduction of brain-wave amplitude then ensued, leading to the disappearance of electrocerebral activity ("flat" EEG). The return to the supine position did not allow either the immediate resolution of EEG abnormalities or consciousness recovery, both of which occurred after a further time interval (mean total duration of syncope, 41.4 seconds.). Conclusions-EEG monitoring during head-up tilt testing allowed recording and systematic description of electrocerebral abnormalities developing in the course of tilt-induced vasovagal syncope.

Clinical and Electroencephalographic Features of Carotid Sinus Syncope Induced by Internal Carotid Artery Angioplasty

“…This most severe type of EEG anomaly was more frequently found in cardioinhibitory syncope, whereas the mildest EEG disturbances (S pattern) were most common during syncopal episodes without asystole or hypotension. In keeping with our results, Ammirati et al 15 previously reported a higher prevalence of tonic-clonic jerks during loss of consciousness in patients with cardioinhibitory responses compared with those with vasodepressor syncope.…”

Seizure-Like Activities during Head-Up Tilt Test-Induced Syncope

“…In patients with myoclonic jerky movements during HUT-induced syncope, EEG showed theta and delta wave slowing without spike or spike-wave activity 15. However, simultaneous EEG recording was not performed in this study.…”

Cerebral Autoregulation in Orthostatic Intolerance

“…Finally, other data obtained using techniques other than transcranial Doppler also suggest that cerebral autoregulation is preserved in NMS. EEG abnormalities (diffuse high‐amplitude slow waves or disappearance of EEG activity) during head‐up tilt‐induced syncope are recorded only at clinically evident syncope and at a time when BP is no longer measurable by auscultation 54. Multifocal myoclonus, visual, or auditory hallucinations may often be associated with such profound cerebral hypoperfusion at syncope 55.…”