A clinical evaluation of a novel algorithm in the reliable detection of epileptic seizures.

PURPOSE: Undetected and prolonged epileptic seizures can result in hypoxic brain damage or death and occur most often when the victim is in bed alone or unsupervised. Sudden unexpected death in epilepsy may not always be preventable but it is believed that timely assistance with rescue medication and body re-positioning may overcome respiratory compromise in some cases. A novel algorithm based on a real time moving 9 s epoch, calculating 25 % percentage heart rate change and/or an oxygen saturation trigger level of <85 % was developed using photoplethysmography and incorporated into a prototype data storage device. METHODS: The algorithm was clinically evaluated in this multicentre trial in the detection of clinically significant epileptic seizures. A range of epileptic seizures and normal physiological events were recorded and classified by reference standard EEG Videotelemetry and time-synchronised event data recorded by the prototype device incorporating the pre-specified cut-off points prospectively and retrospective analysis of all events. RESULTS: 119 participants who were attending electroencephalographic (EEG) videotelemetry as part of their clinical management of their epilepsy consented to take part in the trial. 683 epileptic seizures (77 clinically significant seizures) and 2648 normal physiological events were captured. When using pre-specified cut-off point 25 % heart rate change and/or oxygen desaturation <85 % on the basis of one/other, the device showed a sensitivity of 87 % for detecting clinically significant seizures. False Alarm Rate 4.5 (24 h FAR), detection latency of 58 s using heart rate percentage change. CONCLUSIONS: The results indicate that the novel algorithm can be used in detecting clinically significant seizures.

Parasympathetic alteration during sub-clinical seizures.

INTRODUCTION: Autonomic instability is considered a contributing factor in sudden unexpected death in epilepsy (SUDEP). The aim of this pilot study was to measure parasympathetic activity in sub-clinical seizures to investigate autonomic instability. MATERIALS AND 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. We 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. RESULTS: 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. CONCLUSION: This 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.

Lengthening of corrected QT during epileptic seizures.

PURPOSE: To measure the corrected QT cardiac repolarization time before and during epileptic seizures. METHODS: Thirty-nine video-EEG/ECG/SAO(2) (electroencephalography/electrocardiography/oxygen saturation) telemetry patients were included in this prospective study. Epileptic seizures were identified both clinically and electrographically. RR intervals and associated QT intervals were measured 5 min prior to the onset of the identified seizure. Consecutive RR and associated QT intervals were then measured from the seizure onset until the seizure had ended and the EEG had resumed its preseizure trace. Averaged RR and QT intervals over nine consecutive beats were applied to Bazett's, Hodge's, Fridericia's, and Framingham's formulas to compare the corrected QT values before and during the seizures. RESULTS: A total of 156 seizures had corrected QT analysis performed. Nine generalized tonic-clonic seizures (5 patients), 34 absences (6 patients), 12 tonic seizures (6 patients), 27 temporal lobe seizures (14 patients), 58 frontal lobe seizures (4 patients), and 16 subclinical seizures (4 patients). All formulae reported a statistically significant difference in corrected QT (p < 0.001) during total seizure data compared to total preseizure values. According to Bazett's formula, 21 seizures (nine patients) transiently increased their corrected QT beyond normal limits, with a maximum corrected QT of 512 ms during a right temporal lobe seizure. CONCLUSION: Significant lengthening of corrected QT cardiac repolarization time occurred during some epileptic seizures in this study. Prolonged corrected QT may have a role in sudden unexplained death in epilepsy (SUDEP).