• Angelman syndrome (AS) is a developmental disorder affecting the brain.
  • AS has been shown in most cases to have a genetic cause. Specifically, it is thought to occur from a problem on a chromosome called 15q11-13 that is passed from a mother to the child. In AS, a part of this chromosome is deleted or not working properly. It can also occur when two copies of the genetic change are inherited from a father (uniparental disomy), there is a change in the UBE3A chromosome or there is a defect in the imprinting center (expression of a gene).
  • About 1 in 10 people with AS may have symptoms of AS but do not have a clear genetic cause. Epilepsy is present in more than 8 out of 10 affected individuals.
  • AS occurs in approximately 1 out of 15,000 live births. AS affects boys and girls equally.
  • AS is generally found when a baby is between 6 and 12 months old and developmental delays become apparent to parents and caregivers.
  • Treatment focuses on managing medical and developmental issues.

How is Angelman Syndrome diagnosed?

If developmental delays are seen, a child should be seen first by the pediatrician as there are many causes of developmental problems. A neurologist should be consulted if seizures are seen or developmental problems associated with AS are observed. A work-up to diagnose AS would include:

  • Blood tests to look for genetic problems that are specific to AS.
  • EEG (electoencephalogram) testing
  • Imaging studies with magnetic resonance imaging (MRI)
  • Speech and swallow evaluations
  • Sleep studies

What types of developmental problems may be seen with AS?

Features seen consistently include:

  • Severe problems with developmental delay
  • Balance or movement problems (unsteady walking, tremor)
  • Behaviorally, the child may have frequent laughing or smiling with a happy sociable demeanor and be easily excitable
  • More motor activity than is usual, for example hand flapping or waving
  • Severe speech problems  (about 1 out of 3 children are unable to speak words)

Features seen commonly but not all the time include:

  • The head is smaller than expected from delayed growth in head circumference (called microcephaly)
  • Seizures and abnormal EEG findings

Features that may be associated with AS include:

  • Flat occiput (back of the head is flatter than normal)
  • Movements of the mouth such as tongue thrusting, sucking and swallowing problems, frequent chewing
  • Problems feeding for infants
  • Frequent drooling
  • Wide mouth and wide spaced teeth,
  • Decreased tone in muscles of the trunk
  • Changes in the color of the skin lighter than expected, light hair and eye color (compared to family)
  • Problems with sleep-wake cycles
  • Curvature of the spine (scoliosis)
  • Overweight with food-related behaviors
  • Constipation
  • Wide based gait
  • Brisk reflexes  
  • Increased sensitivity to heat

What types of seizures occur in Angelman Syndrome?

Seizures are frequently seen in childhood. They may continue or stop and later reappear in adulthood. Seizures usually begin between 1 and 3 years of age. A child may have many different types of seizures, for example:

  • Atonic, generalized tonic-clonic, absence, complex partial, myoclonic, tonic, secondarily generalized and partial motor seizures are commonly seen.
  • Atypical absence and myoclonic seizures are very common.
  • Status epilepticus, a seizure emergency, may be seen. Nonconvulsive status epilepticus (which consists of repeated or prolonged periods of absence, atypical absence or partial seizures) happens more often than status epilepticus with tonic-clonic seizures.
  • Frequent or prolonged episodes of nonconvulsive status epilepticus can contribute to a poor cognitive outcome for children with AS.
  • Seizures are usually difficult to control with seizure medications for many children with AS.

What does an EEG show in AS?

An EEG in a person with AS reflects activity that may contribute to the frequent seizures and also to other developmental or neurologic problems.

  • EEG patterns in AS may show runs of slow wave activity over the frontal areas of the brain and sharp waves in this same area. Slowing may also be seen most in the central and temporal regions of the brain; the central regions are involved in motor and sensory functions. Changes can also be seen in the posterior region or back of the brain.
  • Using EEG terms, the EEG patterns in AS may include: a) high amplitude rhythmic 2 to 3 Hz delta activity seen mainly over frontal regions with a variant composed of sharp slow waves; b) prolonged runs of rhythmic 4 to 6 Hz theta with centrotemporal emphasis; or c) high amplitude 3 to 6 Hz rhythmic activity containing small spike over posterior regions

What types of care and treatment are available for children with AS?

  • Any of the seizure medications for the types of seizures in AS may be tried. Some common ones given to people with AS include: valproate, clonazepam, phenobarbital, leviteracetam, lamotrigine or topamax.
  • If seizure medications don’t work, the ketogenic diet or a vagus nerve stimulator (VNS) may be used in addition to seizure medicines.
  • AS is one of the rare epilepsies that affects a person in many ways. A team approach is definitely needed to address the person’s health and daily life. Build your team to include a supportive pediatrician, neurologist, nurse practitioner, therapists and social worker.
  • Communication (speech) therapy, physical therapy and behavioral therapy may assist with your child's progress.
  • The family will need help too. Consider a support group to link with other families facing similar challenges.

What is the outlook for people with AS?

  • Currently, there is no cure for Angelman Syndrome, but research is looking at potential treatments that would target specific genes.
  • Right now, treatment for people with AS aims to manage medical, developmental, and behavioral issues.
  • New advances in our understanding of AS and other rare epilepsies will help open doors to new treatments. Learn how to participate!
Authored by: Elaine Kiriakopoulos MD, MSc | Drug Resistant and Rare Epilepsies Editor on 3/2015