Atonic‐BECTS: An unusual presentation of self‐limited epilepsy in childhood

Abstract

Objectives

We describe an unusual patient with self‐limited epilepsy in childhood to aid in the accurate diagnosis and timely treatment of an atonic variant of self‐limited focal epilepsy of childhood with centrotemporal spikes.

Methods

We reviewed the medical records documenting the clinical presentation, diagnostic evaluation, and treatment. We also reviewed the relevant video electroencephalograms (EEGs).

Patient Description

This 3‐year‐old girl with self‐limited focal epilepsy of childhood (formerly called benign rolandic epilepsy) began having recurrent falls. Multiple clinical seizures were recorded on video EEG. The video documented generalized loss of tone resulting in falls, while the ictal EEG revealed one‐second paroxysms of 4 Hz spike‐slow‐wave discharges in the left centrotemporal region, followed by a brief generalized electrodecrement for 400 milliseconds. These findings support the diagnosis of an atypical variant of benign epilepsy with centrotemporal spikes (BECTS), known as atonic‐BECTS. Valproic acid was maximized. On follow‐up, the patient was seizure‐free with a normal EEG and normal development.

Discussion

Few prior publications describe atonic‐BECTS. We present a child with atonic‐BECTS whose ictal video EEG confirms atonic seizures. While atonic seizures typically occur with generalized epilepsies, our report highlights that they can present as an atypical manifestation of self‐limited focal epilepsy in childhood.

Introduction

Several reports describe atypical variants of benign epilepsy with centrotemporal spikes (BECTS), including atypical benign focal epilepsy of childhood, status epilepticus of BECTS, Landau–Kleffner syndrome, and continuous spike‐wave during slow‐wave sleep. ¹ However, there are limited reports describing atonic‐BECTS.

We report a normally developing child with BECTS who developed atonic seizures, confirmed with unique ictal video EEG.

Patient Description

This 3‐year‐old girl who had self‐limited focal epilepsy of childhood with centrotemporal spikes (formerly called benign rolandic epilepsy) developed new‐onset frequent episodes of tripping and falling a few months after diagnosis.

She initially presented with focal to bilateral tonic‐clonic seizures described as twitching of the right face with intact awareness, occasionally progressing to bilateral tonic‐clonic movements. The family also reported new‐onset frequent falls and possible quick jerks of the right hemibody. Her interictal EEG at seizure onset demonstrated frequent high‐amplitude spike‐slow‐wave discharges in the left centrotemporal region (C3–T7), with a wide field of distribution spreading across the midline to involve the right centrotemporal region (C4–T8) as well. These epileptiform discharges were sleep activated and had a horizontal dipole distribution (with positivity in the ipsilateral frontal region). No seizures were recorded in this study, and it remained unclear what the falls represented. The interictal EEG pattern (Figure 1) was consistent with BECTS. Magnetic resonance imaging of the brain was normal. A genetic epilepsy panel was nondiagnostic. Due to recurrent seizures with secondary generalization, she was started on valproic acid.

Figure 1.

Interictal electroencephalogram at seizure onset (3 years old). Left centrotemporal epileptiform discharges (C3–T7), with horizontal dipole spreading across the midline to involve the right centrotemporal region (C4–T8). Montage: Bipolar longitudinal. Sensitivity: 150 µV/cm.

A few months later, she presented with ongoing recurrent falls in addition to increased seizure frequency, noted particularly during illnesses. Due to these breakthrough seizures, clobazam was added to her medication regimen in addition to valproic acid.

Her seizure frequency further worsened at 6 years of age, with falling episodes occurring several times throughout the day. One such episode was witnessed by a medical provider, who noted a generalized loss of tone followed by a fall. This alerted suspicion for possible atonic seizures. She was reportedly compliant with her seizure medications. Her clinical presentation of acute episodes of loss of tone resulting in falls is most consistent with drop attacks. These may result from tonic, myoclonic, or atonic seizures. Given the witnessed loss of axial tone, atonic seizures were thought to be most likely. Atonic seizures are more typically associated with symptomatic generalized epilepsies and developmental/epileptic encephalopathies than with BECTS. ²

The patient was admitted for continuous video EEG monitoring to clarify the falls. The interictal EEG pattern (Figure 2) demonstrated frequent very high‐amplitude spike‐slow‐wave discharges in the left centrotemporal region (C3–T7), with a wide field of distribution spreading across the midline to involve the right centrotemporal region (C4–T8). They had a horizontal dipole distribution (with positivity in the ipsilateral frontal region) and were sleep activated but did not satisfy the criteria for electrical status epilepticus of sleep. This interictal EEG was similar to her previous EEGs with the exception that the epileptiform discharges were much more frequent and higher in amplitude.

Figure 2.

Interictal electroencephalogram at current presentation (6 years old). Left centrotemporal epileptiform discharges (C3–T7), with horizontal dipole spreading across the midline to involve the right centrotemporal region (C4–T8). Montage: Bipolar longitudinal. Sensitivity: 200 µV/cm.

Several atonic seizures were recorded during this study. On video, she appeared to momentarily lose tone in the neck and trunk for two seconds (see Video 1). The ictal EEG pattern (Figure 3) demonstrated a brief one‐second paroxysm of 4 Hz spike‐slow‐wave discharges in the left centrotemporal region, similar to the interictal discharges, followed by a brief generalized electrodecrement for 400 milliseconds.

Figure 3.

Ictal electroencephalogram at current presentation (6 years old). Brief paroxysm of left centrotemporal spike‐slow wave discharges, followed by a brief generalized electrodecrement. Montage: Bipolar longitudinal. Sensitivity: 200 µV/cm.

At the most recent follow‐up at 7 years old, the patient continues to demonstrate age‐appropriate development and is seizure‐free on valproic acid 33 mg/kg/day and clobazam 0.44 mg/kg/day with a normal 24‐hour video EEG.

Discussion

There are few reports documenting self‐limited focal epilepsies associated with atonic seizures in a normally developed patient. ³ , ⁴ Previously noted features of atonic‐BECTS have included head drop, truncal sway, and recurrent falls. These individuals typically present at an earlier age and experience more frequent seizures, either with this semiology or with the classic focal seizures of BECTS. ⁴ Recognizing this semiology is important to avoid misclassifying these as nonepileptic events. ⁵

In our patient, the loss of tone correlating with a focal ictal discharge followed by a generalized electrodecrement on EEG supports the diagnosis of an atonic variant of BECTS (atonic‐BECTS). Usually, atonic seizures occur with symptomatic generalized epilepsy syndromes or developmental/epileptic encephalopathies, such as Lennox–Gastaut syndrome, myoclonic‐astatic epilepsy (Doose syndrome), or epileptic encephalopathy with continuous spike and wave during sleep. Among these conditions, generalized atonic seizures are typically associated with a rapid fall with truncal atonia lasting less than one second. Truncal atonia among focal atonic seizures, as in our patient, lasts slightly longer than one second. ⁶

However, it is important to consider that atonic seizures may occur in the setting of BECTS, consistent with a diagnosis of atypical benign focal epilepsy of childhood. These patients typically have normal development and a self‐limited course but are at risk for evolution to an epileptic encephalopathy with continuous spike and wave during sleep. ² It is hypothesized that focal atonic seizures may involve the central head regions. ⁵ Involvement of the primary negative motor area, supplementary negative motor area, primary motor area, and corticoreticulospinal fibers have been implicated. ⁵

Carbamazepine and some benzodiazepines may worsen atonic seizures in patients with BECTS. ⁴ In our patient, the atonic seizures likely started prior to medication initiation. Once atonic seizures were captured on EEG, valproic acid was maximized and clobazam was weaned, leading to seizure freedom.

It is important to consider atonic‐BECTS as an additional atypical variant of self‐limited focal epilepsy syndromes. Atonic seizures rarely occur with focal epilepsies, so consideration of this variant faciliates the correct diagnosis and appropriate management of these individuals.

Author Contributions

Varun Sampat: Conceptualization; investigation; methodology; writing—original draft; writing—review and editing. Avantika Singh: Conceptualization; investigation; methodology; supervision; writing—review and editing. Hema Patel: Conceptualization; investigation; methodology; supervision; writing—review and editing.

Ethics Statement

This study is IRB exempt; however, written consent was obtained for use of the patient’s video.

Supporting information

Additional supporting information can be found online in the Supporting Information section at the end of this article.

Ictal EEG with concurrent video.