Multimodal, automated detection of nocturnal motor seizures at home: Is a reliable seizure detector feasible?

Abstract

Objective: Automated seizure detection and alarming could improve quality of life and potentially prevent sudden, unexpected death in patients with severe epilepsy. As currently available systems focus on tonic-clonic seizures, we want to detect a broader range of seizure types, including tonic, hypermotor, and clusters of seizures.

Methods: In this multicenter, prospective cohort study, the nonelectroencephalographic (non-EEG) signals heart rate and accelerometry were measured during the night in patients undergoing a diagnostic video-EEG examination. Based on clinical video-EEG data, seizures were classified and categorized as clinically urgent or not. Seizures included for analysis were tonic, tonic-clonic, hypermotor, and clusters of short myoclonic/tonic seizures. Features reflecting physiological changes in heart rate and movement were extracted. Detection algorithms were developed based on stepwise fulfillment of conditions during increases in either feature. A training set was used for development of algorithms, and an independent test set was used for assessing performance.

Results: Ninety-five patients were included, but due to sensor failures, data from only 43 (of whom 23 patients had 86 seizures, representing 402 h of data) could be used for analysis. The algorithms yield acceptable sensitivities, especially for clinically urgent seizures (sensitivity = 71-87%), but produce high false alarm rates (2.3-5.7 per night, positive predictive value = 25-43%). There was a large variation in the number of false alarms per patient.

Significance: It seems feasible to develop a detector with high sensitivity, but false alarm rates are too high for use in clinical practice. For further optimization, personalization of algorithms may be necessary.

Keywords: Accelerometry; Epilepsy; Heart rate; Seizure monitoring; Sudden unexpected death in epilepsy.

Figure 1

Boxplots showing median, 25th percentile, 75th percentile, and range of maximum heart rate (A), maximum slope of the heart rate (B), maximum summed waveform length (C), and maximum of spectral contrast (Kalitzin et al.25) in accelerometry (D) of included patients during seizure and nonseizure periods. Variation among patients is generally high, which can be seen in the wide range of maximum values found during seizures as well as during nonseizure periods. Maximum of the heart rate shows the most distinction for generalized tonic–clonic (GTC) seizures. GT, generalized tonic; HM, hypermotor.

Figure 2

Heart rate and accelerometry data in a patient with three generalized tonic–clonic seizures. The clinical seizures occur between the gray vertical lines. The top panel shows heart rate (HR) and summed waveform length (WL), and the bottom panel shows spectral contrast (SC) of the accelerometry. The black circles highlight non–seizure‐related rises in HR. All seizures come with a high rise in HR, an increase in summed waveform length, and high spectral contrast in the range of 2–6 Hz. In all three seizures, the rise in HR is visible before seizure onset. Also, HR has reached high levels before movement is registered, which is due to the tonic phase, which starts the seizure and in which amplitude of movement is very low.