Abstracts

Rationale: Epilepsy with myoclonic absences (EMA) is a rare genetic generalized epilepsy with distinct features compared to childhood absence epilepsy (CAE). While CAE is a common epilepsy syndrome, EMA is rare, making up less than 1% of epilepsy. EMA patients also have decreased response to treatment and more intellectual impairment compared to CAE. Clinically, myoclonic absence (MA) seizures have rhythmic myoclonic jerking of the bilateral upper extremities, which results in ratcheting movements with sequential rise of arms in discrete steps as well as altered awareness. Electrographically, rhythmic 3 Hz generalized spike-and-wave discharges are time-locked to arm movements. Patients with EMA may have other seizure types including bilateral tonic-clonic seizures, absence seizures, and atypical absence seizures. Given the rarity of EMA compared to CAE, we wanted to highlight the clinical heterogeneity by presenting a retrospective review of ten pediatric patients with EMA.

Methods: Patients seen at Monroe Carell Jr. Children’s Hospital at Vanderbilt (MCJCHV) were identified through Epic’s Clarity data warehouse using a free-text search of “absence,” “myoclonic,” and “myoclonic absence” in video electroencephalogram (vEEG) reports in patients less than 22 years old between November 2017 and April 2021. This search identified eight patients that had MA seizures recorded on EEG. An additional two patients with the diagnosis of EMA made prior to November 2017 were also included. After identification, medical records were retrospectively reviewed to determine each patient’s demographics, age of onset, vEEG reports, other seizure semiologies, anti-seizure medication (ASM) history, non-medication treatments, seizure frequency at follow-up, comorbidities, and diagnostic evaluations.

Results: Ten patients were identified with the diagnosis of EMA, with age of onset six months to nine years, half were female (n = 5/10), 40% had atonic component to MA seizures (n = 4/10), 20% presented with MA status epilepticus (n =2/10 that were identical twins), most received valproic acid as part of ASM regimen (n = 7/10), most did not have definite pathogenic genetic mutation for epilepsy (n = 8/10 that included identical twins), and most had incomplete control of seizures at last follow-up (n = 7/10). Of the three patients whose MA seizures resolved, seizure freedom was achieved with three different ASMs (ethosuximide, valproic acid, and levetiracetam). One patient underwent complete corpus callosotomy for treatment of MA seizures with atonia with resolution of seizures at two months after surgery.

Conclusions: In our cohort of ten pediatric patients with EMA, phenotypic heterogeneity was evident in seizure semiologies, ASM history and current regimen, non-medication treatments, seizure frequency, and comorbidities. Identifying this specific epilepsy syndrome is important in guiding treatment decisions and provides better insight into neurodevelopmental prognosis. Novel findings in our cohort include identical twin siblings with MA seizures as well as occurrence of MA status epilepticus. Notably, 75% of the patients with an atonic component did not achieve seizure freedom with medication. The patients that became seizure free did not have an atonic component. Corpus callosotomy was performed in one patient with MA seizures with atonia, while another is awaiting this surgery. Corpus callosotomy as a treatment option for EMA is not described in the literature, however, given one patient’s encouraging seizure response thus far, a larger longitudinal study may be considered to better evaluate efficacy.

Funding: Please list any funding that was received in support of this abstract.: none.