Children With Trisomy 21 and Lennox-Gastaut Syndrome With Predominant Myoclonic Seizures

Introduction: Lennox-Gastaut syndrome is a severe form of pediatric epilepsy that is classically defined by a triad of drug-resistant seizures, including atonic, tonic, and atypical absence seizures; slow spike-and-wave discharges and paroxysmal fast activity on electroencephalography (EEG); and cognitive and behavioral dysfunction. In the vast majority, Lennox-Gastaut syndrome develops in patients with an identified etiology, including genetic or structural brain abnormalities. Long-term prognosis is generally poor with progressive intellectual deterioration and persistent seizures. At present, there are few reported cases of Lennox-Gastaut syndrome and trisomy 21 in the literature. To further delineate the spectrum of epilepsy in trisomy 21, we reviewed children with trisomy 21 and Lennox-Gastaut syndrome at one center over 28 years.

Methods: This is a retrospective case series. At our institution, all EEG results are entered into a database, which was queried for patients with trisomy 21 from 1992 to 2019. Pertinent electroclinical data was obtained from medical records.

Results: Of 63 patients with trisomy 21 and epilepsy, 6 (10%) had Lennox-Gastaut syndrome and were included in the study. Four of the 6 patients were male and 5 of 6 had neuroimaging, which was normal. Follow-up ranged from 3 to 20 years. Notably, 5 of 6 had predominant myoclonic seizures throughout the course of their epilepsy, associated with generalized spike-wave discharges, <100 milliseconds.

Conclusion: We observed myoclonic seizures to be a predominant seizure type in patients with trisomy 21, suggestive that trisomy 21 patients may have a unique pattern of Lennox-Gastaut syndrome.