Epilepsy with myoclonic absences: Electroclinical characteristics in a distinctive pediatric epilepsy phenotype

Purpose: The purpose of this article was to study the electroclinical characteristics and seizure outcome of children with epilepsy with myoclonic absences (EMA).

Method: In this descriptive cohort study, we reviewed clinical records of patients who met the criteria for EMA. Each patient's demographic data, birth/developmental history, seizure semiology/pattern, antiepileptic drugs (AED), clinical examination, video-electroencephalography (VEEG), and neuroimaging data were reviewed. Response to AED and change in seizure frequency/pattern on follow-up were noted. Responders were defined by seizure freedom/>50% reduction in seizure frequency on follow-up.

Result: Twelve children were diagnosed with EMA between 2008 and 2013 [50% male; mean age of onset: 3.5years]. Main seizure types were the characteristic myoclonic absences (100%) and generalized tonic-clonic seizures (42%). Ictal correlate on VEEG was 3- to 3.5-Hz spike-and-wave discharges (82%) and fast recruiting bifrontal rhythm (25%). One patient had specific MRI abnormalities. Mean duration of follow-up was 23.9months. Seizure frequency had significantly improved on follow-up (p=0.005), and at last follow-up, nine patients were in the responder group: four seizure-free for at least 1year, two with >90%, and three with >50% reduction in seizure frequency. The number of AED reduced significantly between initial visit and last follow-up among responders. Two patients on follow-up developed different seizure patterns, with generalized tonic and complex partial seizures. One responder expired because of unprovoked generalized convulsive status epilepticus.

Conclusion: This cohort, the largest from the Indian subcontinent on the rare syndrome of EMA, suggests mild heterogeneity in a seemingly homogenous electroclinical phenotype. Clinical semiology while unique may demonstrate focality and variable ictal patterns. Most patients respond to either valproate monotherapy or valproate-lamotrigine combination; however, the prognosis remains guarded. The seizures of a minority of patients remain drug-refractory and may evolve into tonic or complex partial seizures.

Epilepsy with myoclonic absences; Pediatric epilepsy; Tassinari syndrome.