Epilepsy with myoclonic absences

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.

Epilepsy with myoclonic absences is a rare form of epilepsy. It happens more in boys and approximately 25 per cent of patients (one quarter) will have another family member with a form of epilepsy.

The underlying cause of this epilepsy syndrome is unknown. Myoclonic absences may be seen in children with brain abnormalities or with some genetic disorders.

Symptoms

The child loses awareness of their surroundings. How much their awareness is changed will vary from child to child. This is accompanied by severe rhythmical jerking of both upper limbs (possibly one arm more than the other) and often with a stiffening of the upper arms resulting in the arms being raised upwards. Sometimes jerking of the muscles around the chin and mouth but not the eyes may also happen. The seizure usually lasts for eight to 60 seconds.

Seizures are more common when the child is tired or has just woken up. The doctor may try to provoke a seizure by getting the child to hyperventilate (over-breath) for up to four minutes. Although this may feel unpleasant it is important in order to correctly diagnose this syndrome.

Other seizure types such as tonic-clonic seizures, drop-attacks and typical absence seizures can happen in about two-thirds of patients.

Almost half of all children with epilepsy with myoclonic absences have some degree of learning difficulty before the start of their seizures. Of the remainder, a further half will develop learning difficulties and behavioral problems after their seizures start.

Diagnosis

A description of the seizure given by the child and any eyewitnesses can help with identifying the particular seizure type in this epilepsy syndrome. An electroencephalogram (EEG) will be carried out.

The doctor may want to order further tests, including a brain scan and a blood test, to look for genetic disorders.

Treatment

Treatment is often difficult, as seizures may not respond to anti-epileptic drugs (AED’s). Commonly used drugs include sodium valproate (Epilim), ethosuximide (Zarontin) and lamotrigine (Lamictal). A combination of lamotrigine and sodium valproate or ethosuximide and sodium valproate are often more effective than a single drug. Another antiepileptic drug, clobazam (Frisium) may also be helpful.

Prognosis (outlook)

Epilepsy with myoclonic absences has a variable but often poor prognosis, with over half of all children continuing to have seizures into adulthood. Children whose seizures don’t respond well to treatment are at particular risk of developing other seizure types, and there is some evidence that these children are also most at risk of developing learning and behavioural difficulties.

Support organisation

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