“Convulsive” Nonepileptic Seizures Have a Characteristic Pattern of Rhythmic Artifact Distinguishing Them from Convulsive Epileptic Seizures

Abstract

Summary:Purpose: Approximately 30% of patients admitted for video-EEG monitoring have psychogenic nonepileptic seizures (PNES). Differentiation of "convulsive" PNES from convulsive seizures can be difficult. The EEG often displays rhythmic movement artifact that may resemble seizure activity and confound the interpretation. We sought to determine whether time-frequency mapping of the rhythmic EEG artifact during "convulsive" PNES reveals a pattern that differs from that of epileptic seizures.Methods: EEGs from 15 consecutive patients with "convulsive" PNESs were studied with time-frequency mapping by using NEUROSCAN and compared with 15 patients with convulsive epileptic seizures. Fast Fourier transforms (FFTs) were performed to determine the dominant frequency for 1-to 2-s windows every 2 s through the seizures. Results:The dominant frequency remained stable within a narrow range for the duration of the PNES, whereas in the epileptic seizures, it evolved through a wide range. The coefficient of variation of the frequency during the seizures was considerably less for patients without epilepsy (median, 15.0%; range, 7.2-23.7% vs. median, 58.0%; range, 34.8-92.1%; p < 0.001). The median frequency did not differ significantly between groups (4.2 vs. 4.6 Hz; p = 0.290).Conclusions: "Convulsive" PNES display a characteristic pattern on time-frequency mapping of the EEG artifact, with a stable, nonevolving frequency that is different from the evolving pattern seen during an epileptic seizure. Key Words: Psychogenic nonepileptic seizures-Time-frequency mapping-EEG.Individuals with psychogenic nonepileptic seizures (PNES) have recurrent episodes of altered movement, sensation, or experience that resemble epileptic seizures but are not associated with abnormal electrical activity in the brain (1). The etiology of PNES remains unclear; however, they are presumed to relate to underlying psychogenic disturbances, with multiple factors including personality traits playing a role in both etiology and prognosis (2).PNES represent a common diagnostic and management problem, not just for the neurologist, but also for general practitioners, emergency departments, and other treating physicians. The estimated prevalence of PNES is between 2 to 33 per 100,000 individuals, making PNES one of the more common conversion disorders in the community (3).

Does the primary literature provide support for clinical signs used to distinguish psychogenic nonepileptic seizures from epileptic seizures?

“…Vinton et al performed a time-frequency analysis of movement artefacts in convulsive PNES and generalised tonic clonic seizures (GTCS). Brief pauses in rhythmic movement were documented in 47% of PNES patients and none of the ES patients 45. Chen et al compared partial ES with PNES.…”

Proposal for best practice in the use of video-EEG when psychogenic non-epileptic seizures are a possible diagnosis

“…While it is best to observe ictal movements on video, movement artefact captured in EEG channels or, ideally, bilateral surface EMG recordings can be useful. Whereas the frequency of shaking movements in PNES remains relatively static or episodes of vigorous motor activity may be interspersed with ‘pauses’ of more than five seconds, the frequency of movements associated with epileptic seizures commonly change and evolve during the course of a seizure (Vinton et al, 2004, Devinsky and Paraiso, 2000, Beniczky et al, 2014). In psychogenic convulsive events, deltoid EMG amplitude is less, and the ratio of high frequency (tonic): low frequency (clonic) EMG activity is smaller, when compared to that typically observed in epileptic generalised tonic clonic seizures (Beniczky et al, 2014).…”

Psychogenic non-epileptic seizures: aetiology, diagnosis and management

“…The frequency of the shaking in PNES tends not to change during the course of a seizure (only the amplitude varies). The frequency of muscle contractions diminishes gradually in tonic-clonic epileptic seizures (Vinton 2004).…”