[Clinical and electroencephalographic characteristics of epilepsy with myoclonic absences]

Epilepsy with myoclonic absences (EMA) is a type of childhood epilepsy characterized by a specific seizure type, i.e. myoclonic absences (MA). This study aimed to investigate the clinical and electrophysiological characteristics of EMA.

Video-EEG monitoring was carried out in 6 patients with EMA, and 2 of them were examined with simultaneous deltoid muscle surface electromyogram (EMG). The clinical and EEG characteristics, treatment and prognoses of EMA were analyzed.

Of the 6 patients, 3 were female, and 3 were male. The age of onset was from 2 years and 3 months to 11 years (average 5 years and 2 months). MA was the sole seizure type in 5 patients. One patient presented generalized tonic clonic seizures (GTCS) at the onset and then switched to MA. The manifestations of MA included an impairment of consciousness of variable intensity, rhythmic myoclonic jerks with evident tonic contraction mainly involving the upper extremities, a deviation of head and body to one side or asymmetrical jerks observed in some cases, a duration ranging from 2 to 30 s, an abrupt onset and termination, a high frequency of attacks, at least several times to over 30 times per day, and easily provoked by hyperventilation. The ictal EEG consisted of rhythmic 3 Hz spike and wave discharges that were bilateral, synchronous and symmetrical in all patients. The deltoid muscle EMG recording in 2 patients showed rhythmic myoclonus at the same frequency as the spike and waves. The interictal EEG showed generalized spike and wave discharges in all patients, and focal discharges in some patients. Valproate was the drug of choice, which was often combined with other antiepileptic drugs. The ages at follow up ranged from 6 years and 4 months to 19 years. Seizures were controlled from 8 months to 3 years in 4 cases. The treatment at the onset was late in one case and was irregular in another who had GTCS during the course of the disease. These two cases were followed up for 2 years and 6 months and 5 years, respectively. Seizures could not be controlled in the 2 patients with intellectual impairment.

EMA was a rare type of childhood epilepsy characterized by MA. Clinical observation and ictal video-EEG and EMG were essential to diagnose EMA. Valproate alone or combined with other antiepileptic drugs given early could have a favorable effect to EMA. Delayed therapy and the presence of GTCS might suggest poor prognosis.