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Quantitative analysis of surface electromyography during epileptic and nonepileptic convulsive seizures
Author(s) -
Beniczky Sándor,
Conradsen Isa,
Moldovan Mihai,
Jennum Poul,
Fabricius Martin,
Benedek Krisztina,
Andersen Noémi,
Hjalgrim Helle,
Wolf Peter
Publication year - 2014
Publication title -
epilepsia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.687
H-Index - 191
eISSN - 1528-1167
pISSN - 0013-9580
DOI - 10.1111/epi.12669
Subject(s) - electromyography , electroencephalography , epilepsy , psychogenic disease , tonic (physiology) , seizure types , anesthesia , medicine , psychology , audiology , physical medicine and rehabilitation , neuroscience , psychiatry
Summary Objective To investigate the characteristics of sustained muscle activation during convulsive epileptic and psychogenic nonepileptic seizures ( PNES ), as compared to voluntary muscle activation. The main goal was to find surface electromyography ( EMG ) features that can distinguish between convulsive epileptic seizures and convulsive PNES . Methods In this case–control study, surface EMG was recorded from the deltoid muscles during long‐term video–electroencephalography ( EEG) monitoring in 25 patients and in 21 healthy controls. A total of 46 clinical episodes were recorded: 28 generalized tonic–clonic seizures ( GTCS ) from 14 patients with epilepsy, and 18 convulsive PNES from 12 patients (one patient had both GTCS and PNES ). The healthy controls were simulating GTCS . To quantitatively characterize the signals we calculated the following parameters: root mean square ( RMS ) of the amplitude, median frequency ( MF ), coherence, and duration of the seizures, of the clonic EMG discharges, and of the silent periods between the cloni. Based on wavelet analysis, we distinguished between a low‐frequency component ( LF 2–8 Hz) and a high‐frequency component ( HF 64–256 Hz). Results Duration of the seizure, and separation between the tonic and the clonic phases distinguished at group‐level but not at individual level between convulsive PNES and GTCS . RMS , temporal dynamics of the HF / LF ratio, and the evolution of the silent periods differentiated between epileptic and nonepileptic convulsive seizures at the individual level. A combination between HF / LF ratio and RMS separated all PNES from the GTCS . A blinded review of the EMG features distinguished correctly between GTCS and convulsive PNES in all cases. The HF / LF ratio and the RMS of the PNES were smaller compared to the simulated seizures. Significance In addition to providing insight into the mechanism of muscle activation during convulsive PNES , these results have diagnostic significance, at the individual level. Surface EMG features can accurately distinguish convulsive epileptic from nonepileptic psychogenic seizures, even in PNES cases without rhythmic clonic movements. A PowerPoint slide summarizing this article is available for download in the Supporting Information section here .