Electroclinical characteristics and therapies of tonic spasms

TL;DR

This study examines the electroclinical features and treatment outcomes of tonic spasms in epilepsy patients, suggesting they may be an underreported seizure type.

Contribution

The study provides a detailed analysis of tonic spasms, highlighting their distinct electroclinical features and potential treatment with oxcarbazepine.

Findings

Tonic spasms often occur in clusters and are associated with normal EEG backgrounds in most patients.

Two patients achieved seizure freedom with oxcarbazepine monotherapy.

Tonic spasms differ from established epileptic syndromes like West or Lennox-Gastaut syndrome.

Abstract

Epileptic spasms followed by a tonic component have been frequently observed in patients with late-onset spasms (LOS). However, there is a lack of comprehensive analysis and summary of clinical data related to tonic spasms (TS), including seizures, video-electroencephalogram (V-EEG), synchronous electromyography (EMG) and follow-up data.

To investigate the characteristics of TS, we prospectively collected the clinical data, including 24-h V-EEG and synchronous EMG data of 32 enrolled patients who suffered from epileptic spasms followed by a TS onset at least once during the 24-h V-EEG in the epilepsy center of Xijing Hospital between June 2015 and July 2020. The patients were prescribed anti-seizure medications (ASMs) and followed up for 2–7 years.

The average age of epilepsy onset was 48.06 ± 16.07 months (range: 25 to 88 months). Among the enrolled patients, 22 patients presented with mild intellectual deficits. During the 24-h video-EEG monitoring, an average of 6.94 TS events (range: 3 to 21) were recorded, and these TS seizures often occurred in clusters. In addition to TS, 26 patients experienced generalized tonic-clonic seizures (GTCS), atypical absence seizures, myoclonic seizure, and epileptic spasms. None of the 32 patients with TS displayed hypsarrhythmia during the 24-h video-EEG recording. A total of 28 patients showed normal EEG backgrounds. Interictal epileptic discharges, including slow waves (SW), spike/sharp slow waves (SSW), and spikes, often displayed multifocally. Notably, two patients achieved seizure freedom for more than 2 years through monotherapy with oxcarbazepine (OXC), which was associated with normalization of the EEG.

It is difficult to classify the patients with TS as any existing epileptic syndromes, which were distinct from West syndrome or Lennox-Gastaut syndrome. TS might be an underreported seizure type and further studies are needed to gain a more comprehensive understanding of the electro-clinical features and appropriate choice of ASMs for treating tonic spasms.

The online version contains supplementary material available at 10.1186/s42494-024-00158-3.

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