Early myoclonic encephalopathy

Epilepsy Action is indebted to Dr Richard Appleton, a Consultant Paediatric Neurologist who specialises in children’s epilepsy, and to Dr Rachel Kneen, Consultant Paediatric Neurologist and Dr Stewart Macleod, Specialist Registrar in paediatric neurology, at Alder Hey at Alder Hey Children’s Hospital, Liverpool, who have kindly prepared the information on this page.

(sometimes called neonatal myoclonic encephalopathy)

Early myoclonic encephalopathy almost always starts in the newborn period or in very early infancy. It is a syndrome with several causes but it is thought that most of the infants have an underlying biochemical disorder even if this cannot be identified. Some infants definitely have a very rare condition called non-ketotic hyperglycinaemia. Affected infants have extremely poor development.

Symptoms

The seizures can be myoclonic jerks, which affect small areas of the body from time to time, massive myoclonic movements (sudden flexion or extension), partial motor seizures or, rarely, tonic spasms (when stiffness occurs). The seizures are very frequent throughout the day. After several months seizures usually change to infantile spasms (West syndrome).

The electroencephalogram (EEG), which records the electrical activity ongoing in the brain, shows evidence of abnormal discharge or spikes and waves interspersed with periods of flatness. The type of record is referred to as suppression-burst and is similar to that seen in Ohtahara’s syndrome.

The infants are all neurologically very abnormal. Often they are extremely floppy and excessively sleepy.

Treatment

The seizures are often resistant to medication. If this syndrome is suspected it is probably unwise to use valproate (Epilim), since in this group of babies, an underlying biochemical disorder is quite likely.

It is important to test the babies thoroughly for a possible chemical disorder, in case this in itself can be treated. The actual choice of medication is difficult and it may be safer to use some of the older anti-epileptic drugs such as Phenobarbital before others are tried.

All babies should receive a trail of pyridoxine (vitamin B6) in case they have pyridoxine dependent seizures.

Prognosis (outlook)

Infants with early myoclonic encephalopathy make very little developmental progress. They remain totally dependent and often feed poorly. More than half of the infants who have been reported in the literature to have this condition die within the first year of life. Those who survive remain severely developmentally delayed.

Support organisation

Contact a Family, 209-211 City Road, London, EC1V 1JN, telephone 0808 808 3555, www.cafamily.org.uk