Observations on EEG patterns in neurally-mediated syncope: an inspective and quantitative study

We performed an observational EEG study in 43 patients with neurally-mediated syncope in basal condition and during hyperventilation (HV), and compared it with 32 healthy controls. On blind analysis at rest, EEG was classified as normal in 47% of patients (vs. 94% of controls, P < 0.001). More abundant and pronounced delta-theta activities and alpha stowing were found in patients than in control subjects on both visual inspection and quantitative spectral analysis. During prolonged HV, the EEG remained normal in 21% of patients only. Slow activities became more evident in patients than in control subjects, and intermittent rhythmic delta activity appeared in 40% of syncopal patients. These "pseudoparoxysmal" EEG changes differed from the common slowings induced by HV in adult subjects and were not observed in our control subjects. Moreover, these distinctive EEG changes, a common finding in syncopal patients, could not be confused with epileptiform activity of any kind. Further studies will clarify the pathophysiology of these EEG modifications. (C) 2004 Elsevier SAS. All rights reserved.