Epileptic Negative Myoclonus in a Newborn with Hemimegalencephaly

Abstract

Summary: Purpose:We report the case of a male newborn with Ohtahara syndrome and right hemimegalencephaly who presented epileptic negative myoclonus in the first days of life.Methods: Prolonged polygraphic studies were performed, as well as MRI and a full clinical examination.Results: EEG showed a constant and nonreactive pattern of burst suppression. There were several kinds of electro-clinical seizures (generalized myoclonia, short atonias, typical spasm and tonic spasms) at the beginning of the EEG's burst. The periods of EMG silence, lasting less than 300 ms, were associated with stereotyped EEG transients.Conclusions: Epileptic negative myoclonus can be observed also in neonatal age. The short transient impairment of motor function observed in the newborn seems linked to the slow component of spike-wave discharge, but its mechanism is still not clear. Key Words: Epileptic negative myoclonusHemimegalencephaly-Early epileptic encephalopathy.A severe epileptic syndrome often with polymorphic seizures characterizes early epileptic encephalopathies. No epileptic negative myoclonus has been reported. We present one patient with Ohtahara syndrome with hemimegalencephaly in whom epileptic negative myoclonus occurred as a neonate. CASE REPORTThe male infant was born after an uneventful pregnancy and term delivery. Since the first days of life, frequent startles intermixed with partial tonic seizures located at the right limbs with or without secondary generalization. A loading dose of phenobarbital (PB; 20 mg/ kg) was administered, followed by maintenance therapy of 4 mg/kg/day.At clinical examination, there was evidence of jitteriness with limb hypertonia and hyperreflexia more marked at the right side. There was neither fixation nor an evident responsiveness. Feeding was made difficult by frequent seizures.Routine analysis and metabolic as well as microbiologic and immunologic examinations were normal. Karyotype was 46, XY. Magnetic resonance imaging (MRI) showed a right hemimegalencephaly (Fig. 1). Results of the polygraphic studyWe performed prolonged polygraphic studies in the first days of life, by using electrode placement according to the 10/20 International System modified on the basis of the asymmetric MRI data, so that the midline z electrodes corresponded roughly to the interhemispheric fissure. The examinations showed, during all the states, a pattern of constant and nonreactive burst suppression (Fig. 2); even strong stimulations did not provoke any change of the pattern. Interbursts lasted between 4 and 20 s, and short bursts, only 1-3 s, characterized by highvoltage chaotic spikes and slow waves. At the beginning of each burst, high-voltage spike-or polyspike-waves were usually recorded, coinciding with variable seizures. Consistent with the most dysplastic cortex, highervoltage spike discharges were often observed at the right frontal region; sometimes they were transmitted to the contralateral hemisphere. Several kinds of paroxysmal events were located at the beginning of the bursts: high-voltage s...

Epileptic negative myoclonus in a case of atypical benign partial epilepsy of childhood: a detailed video-polygraphic study

“…ENM is a rare epileptic condition whose exact physiopathology remains unresolved. It has been associated with very diverse clinical situations, such as ABPE, cortical malformations, antiepileptic drug tapering, or more recently hemimegalencephaly 2,3,[5][6][7] . The intensity of the clinical manifestations may be markedly variable, and it may oscillate from slight focal atonia to severe gait disturbances originating pseudoataxia 8 .…”

Proteus syndrome associated with hemimegalencephaly and Ohtahara syndrome: Report of two cases

“…The association of infantile spasms, myoclonias, and partial epilepsy in newborn infants is generally observed in cases with extensive migration disorders diagnosed as Ohtahara syndrome. Guzzeta et al 30 reported the case of a male newborn with Ohtahara syndrome and right hemimegalencephaly who presented epileptic negative myoclonus on the 1st day of life. Dietrich et al 29 described three children with hemimegalencephaly among eight patients with early-infantile epileptic encephalopathy with suppression bursts.…”

Hemimegalencephaly and epilepsy: an overview

“…They may be of partial onset, infantile spasms, epilepsia partialis continua or drop attacks (7,11) . Non-convulsive status epilepticus and atypical seizure types are related in the literature and some authors had reported epileptic negative myoclonus (18,19) .…”