boy staring

What is the syndrome called epilepsy with myoclonic-absences?

Epilepsy with myoclonic-absences is a rare form of epilepsy. Fewer than 1 in 100 children seen in a specialty center for epilepsy have this syndrome.

  • These seizures typically begin between 2 and 12 years of age with the majority starting around 7 years of age.
  • They are seen more often in boys than in girls.
  • The cause of this epilepsy syndrome is unknown.

What do seizures look like in epilepsy with myoclonic-absences?

The most characteristic seizure type is a myoclonic-absence seizure. During a seizure, the child’s neck, back, and arms become stiff or rigid (tonic contraction). There is ratchet-like (repeated starts and stops) jerking of the head, arms, and legs. The child is not aware and has a staring facial expression. The loss of awareness might be subtle and hard to notice.

  • Some children might stop breathing during the tonic or stiffening part of the seizure. They could also lose control of their urine.
  • Seizures last 10-60 seconds and happen several times a day. They may occur in groups or clusters when the child is waking up.
  • Falls during a seizure can happen but are not common.

Over time, 70% of children will have other types of seizures, including generalized tonic-clonic, clonic, absence, and atonic seizures. In the other 30%, myoclonic-absence is the only seizure type. In up to 40% of children, generalized tonic-clonic seizures are noted before myoclonic-absence begin.

Is epilepsy with myoclonic-absences inherited?

The cause of this epilepsy syndrome is unknown. It has been reported that about 1 in 5 children with this condition will have a family member with a form of epilepsy, usually generalized epilepsy.

In up to 3 in 10 children, an inborn or acquired brain injury may be found.

What are known triggers to this seizure type?

  • Breathing heavily or hyperventilation can trigger seizures during an EEG (electroencephalogram).
  • Seizures triggered by intermittent light stimulation are rare.

How is epilepsy with myoclonic-absences diagnosed?

  • Getting a typical clinical history and seizure description, along with an EEG (electroencephalogram), help with making the diagnosis. Find tools and forms to help you describe the seizures in our toolbox.
  • Your doctor will take a good history and may ask your child to hyperventilate (breathe fast and deep) during the examination.
  • The EEG is the most important test. The EEG shows a typical pattern of normal background activity, but a 3 per second spike-wave activity during a seizure. Other abnormalities like spikes and spike-wave discharges may also be seen.
  • MRI (magnetic resonance imaging) scans might be ordered to look for a structural change in the brain. The MRI is usually normal and shows no abnormalities from a specific or known cause.

How is epilepsy with myoclonic-absences treated?

What is the outlook for persons with epilepsy with myoclonic-absences?

  • Approximately 7 in 10 children with epilepsy with myoclonic-absences will eventually be diagnosed with learning disabilities.
  • Some children will develop multiple seizure types - that are resistant to treatment and have a characteristic EEG pattern - called Lennox-Gastaut syndrome.
  • In more than half of the children, seizures will persist into adulthood. In others, they may disappear after a mean period of 5.5 years from onset.
  • Prognosis is more favorable if medication can control the seizures early.

Resources

References

Authored By: 
Angel Hernandez MD
Charuta Joshi MBBS
Authored Date: 
11/2019
Reviewed By: 
Elaine Wirrell MD
on: 
Sunday, November 24, 2019