Brotherstone R et al. – The pilot study indicates that parasympathetic changes occur during sub–clinical seizures. Generalised sub–clinical seizures may be associated with more autonomic instability compared to temporal lobe sub–clinical seizures.Methods
- A prospective study based on Video-electroencephalography (EEG)/electrocardiography (ECG)/oxygen saturation (SAO2) recordings was selected from patients having sub-clinical seizures during stage 3 or 4 sleep.
- The authors analysed R–R intervals in the ECG from 1-min prior to the electrographic onset to the end of sub-clinical seizures.
- Matched non-ictal R–R baseline measurements were selected from stages 3 or 4 sleep.
- R–R interval data were analysed using NeuroScope software providing a cardiac index of parasympathetic activity (CIPA).
- BioSignal short-term heart rate variability (HRV) software was used to analyse the same R–R interval data previously analysed using NeuroScope except that sub-clinical seizure data was embedded within 5-min epochs and compared to 5-min epochs of non-ictal measurements.
- A total of 33 sub-clinical seizures were recorded from 11 patients comprising 19 generalised sub-clinical seizures (2 patients), 9 right temporal lobe sub-clinical seizures (5 patients) and 5 left temporal lobe sub-clinical seizures (4 patients) were compared to matched non-ictal measurements.
- Parasympathetic activity was clearly altered during total sub-clinical seizures in terms of the CIPA (p<0.001) and 5-min HRV high frequency (HF) % (p=0.026) measures.
- Generalised sub-clinical seizures resulted in increased cardiac parasympathetic activity whereas temporal lobe seizures were associated with a decrease in parasympathetic activity.