Key result
Positive tilt tests are linked to left-lateralized EEG slow waves before syncope in ~83% of patients.
Observational (n=18)
No
Absolute Event Rate: 83% vs 0%
p-value: p=< 0.05
EEG activity lateralizes to the left hemisphere before neurally mediated syncope, suggesting a role for the central nervous system in its mechanism.
Should not alter syncope evaluation; leaves open a potential lateralized CNS role in neurally mediated syncope.
OBJECTIVE: To determine the role of the cerebral cortex in neurally mediated syncope, the electroencephalograms (EEG) of patients recorded during head up tilt table test were analysed. DESIGN: Retrospective study. SETTING: University hospital. PATIENTS: 18 patients with syncope or near syncope underwent head up tilt table test with simultaneous ECG and EEG monitoring. METHODS: Standard 70 degrees tilt table test was done with simultaneous ECG and EEG monitoring. EEG waveforms were analysed by both visual inspection and spectral analysis. RESULTS: 6 of 18 patients (33%) had a positive tilt table test. Before syncope slow waves increased in patients with a positive test. In addition, five of six tilt positive patients (83%) had slow wave activity that lateralised to the left side of the brain (mean (SD) 822 (724) v 172 (215) micro V(2), p < 0.05), while none of the tilt negative patients exhibited lateralisation (24 (15) v 26 (19) micro V(2), NS). Spectral analysis showed that the lateralisation occurred in the delta frequency. The lateralisation preceded the event by 5-56 seconds (18 (21) seconds). CONCLUSIONS: EEG activity lateralises to the left hemisphere of the brain before syncope. The lateralisation precedes syncope and is associated with the onset of bradycardia, hypotension, and clinical symptoms. These findings suggest that the central nervous system may have a role in neurally mediated syncope.
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Marco Mercader (2002) conducted an observational in Syncope or near syncope (n=18). Positive head up tilt table test vs. Negative head up tilt table test was evaluated on EEG slow wave activity lateralisation to the left side of the brain (p=< 0.05). EEG slow wave activity lateralised to the left hemisphere in 83% of patients with a positive tilt table test before syncope, compared to 0% of tilt-negative patients.
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