[The correlation between the type of positivity of the tilt test and a simultaneous electroencephalogram: the...

Today the first-choice examination to study neurally-mediated syncope is the tilt test. There are still many aspects to be clarified on the pathophysiology of neurally-mediated syncope, and much uncertainty remains on the therapeutic procedure to adopt. Recent research has investigated the role of neurohumoral agents, thus shifting interest to the pathogenetic role of the central nervous system, over and above that of the already widely studied vegetative nervous system. This is why we decided to carry out the tilt test with simultaneous electroencephalogram (EEG) recordings, with the aim of documenting any possible correlation between test positivity, according to Sutton's classification, and the EEG results.

We studied 15 patients (8 males, 7 females, age range 18-74 years) with a history of repeated syncopal and presyncopal episodes who had formerly undergone numerous clinical and instrumental examinations, including EEG, with negative results. The tilt test was carried out with continuous measurement of blood pressure (Ohmeda Finapres System) and simultaneous EEG recording.

Ten patients (66%) were positive, 6 had experienced syncope episodes (4 type 2A and 2 type 1) and 4 presyncope (1 type 2A and 3 type 1). In all the syncope positive patients the EEG showed modifications in comparison with basal EEG, whereas only 50% of the presyncope positive patients showed slight alterations. There was no EEG alteration for tilt negative patients. The EEG result was markedly different in patients with tilt-induced type 2A syncope in comparison with those with type 1. Type 2A showed the following: 1) slowdown and reduced amplitude of electrical activity during the prodromes; 2) during the syncope, first pseudorhythmic then polymorphic delta activity were followed by total disappearance of activity ("flat" EEG); 3) then, in inverse sequence, reappearance of polymorphic then pseudorhythmic delta activity (average duration of syncope 37 s); 4) lastly, slowdown and reduced amplitude of electrical activity similar to that preceding the syncope. Whereas type 1 revealed: 1) no alteration of electrical activity during the prodromes; 2) during the syncope, first theta then polymorphic delta activity (average duration of syncope 16 s); 3) subsequent normal EEG.

These observations indicate a correlation between the type of tilt test positivity and the EEG results, the latter being markedly more serious in type 2A than in type 1. EEG behavior, different in the two types also during the prodromes and the post-syncopal phase, would suggest a cerebral circle vasoconstriction mechanism in type 2A but not in type 1 mixed with a prevalent vasodepressive component. Should these preliminary results be confirmed by further data there will be evident clinical, prognostic and therapeutic implications. In the light of the considerably different involvement of the central nervous system, we believe it will be necessary to redefine the various types of neurally-mediated syncope in terms of seriousness. Simultaneous EEG could be proposed routinely in tilt test execution and become a determining factor in the choice of a therapeutic option.