Editors' ChoiceEpilepsy

It’s all in the wrist

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Science Translational Medicine  02 Jan 2019:
Vol. 11, Issue 473, eaaw0530
DOI: 10.1126/scitranslmed.aaw0530

Abstract

Motor patterns measured by wrist actigraphy differentiate epileptic seizures from nonepileptic spells.

Psychogenic nonepileptic seizures (PNES), sometimes known as pseudoseizures, are paroxysmal attacks that superficially resemble epileptic seizures (ES) but are caused by psycho-emotional factors rather than the abnormal bursts of electrical brain activity that define epilepsy. Individuals with PNES respond to counseling and treatment of psychiatric comorbidities rather than to antiseizure drugs. PNES are easily mistaken for ES, however, and sometimes appropriate treatment—which requires accurate diagnosis—is delayed for years. The diagnostic gold standard for PNES is video electroencephalographic (EEG) monitoring in an epilepsy monitoring unit (EMU). Unfortunately, this resource-intensive option is not readily available to all patients, so there is a push to develop portable diagnostic devices able to distinguish ES from PNES

ES and PNES often involve repetitive motor activity, a feature that can be captured relatively easily and could potentially be exploited to distinguish PNES from ES. In a typical convulsive ES, stiffening gives way to rhythmic jerking, which slows as the seizure subsides. PNES convulsions may share these motor features but often in a less predictable temporal arrangement. Kusmakar et al. investigate whether movement patterns that occur during convulsions provide sufficient information to distinguish PNES from ES. The authors used actigraphic wristbands to record patients’ movements while they were monitored in an EMU. Motor activity captured during convulsive episodes was transformed into visual patterns, giving each event its own analyzable signature. The authors identified two key metrics, the Tonic Index (TI) and the Dispersion Decay Index (DDI), which differed significantly between PNES and ES. Using an automated system, they were able to correctly classify 95% of PNES and ES events.

This study used data derived from 83 convulsive events experienced by 20 EMU patients. However, seizure semiology differs between individuals, and the motor signatures identified in this cohort may be more or less as robust in a larger group. Moreover, in some seizures, impairment of consciousness is more prominent than motor activity. Whether wrist actigraphy will prove useful in characterizing nonconvulsive events will require further investigation. But with the limited availability of EMU beds and the perils of delayed diagnosis and treatment for PNES, a wristband sensor could prove to be a valuable and practical diagnostic aid.

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