Highlights
- •NEM is a common feature of AS in adolescence and adulthood.
- •NEM differs from seizures in terms of duration, age of onset, and EEG correlate.
- •NEM, while nonepileptic, is often refractory to medications.
- •LEV and benzos are most effective, but no one AED has high rate of efficacy.
Abstract
Angelman syndrome (AS) is a neurogenetic imprinting disorder caused by loss of the
maternally inherited Ube3a gene and is characterized by generalized epilepsy, limited expressive speech, sleep
dysfunction, and movement disorders. Myoclonic seizures are often the first seizure
type to appear, and myoclonic status, associated with developmental regression, may
occur in the first few years of life. Additionally, there have been rare reports of
prolonged episodes of myoclonus without electrographic correlate in adults with AS.
The medical records of 200 individuals seen in the Angelman Syndrome Clinic at the
Massachusetts General Hospital and the Lurie Center for Autism were retrospectively
reviewed to identify and characterize myoclonic seizures and episodes of nonepileptic
myoclonus. Myoclonic seizures were reported in 14% of individuals with age of onset
occurring before 8 years. These are brief events, unless the individual was experiencing myoclonic status,
and electroencephalographs show interictal generalized spike and wave activity. Nonepileptic
myoclonus occurred in 40% of individuals over 10 years of age, and prevalence appears to increase with age. The episodes of nonepileptic
myoclonus arise during puberty or later, with age of onset ranging from 10 to 26 years. These events were captured on 5 video electroencephalographs and had no electrographic
correlate. They can last from seconds to hours, always occurring in the hands and
spreading to the face and all extremities in some individuals. Episodes of nonepileptic
myoclonus have a discrete beginning and end, lacks a postictal period, and are not
associated with significant alteration of consciousness or developmental regression.
These episodes can be difficult to treat and are often refractory to medication; however,
levetiracetam, clobazam, and clonazepam appear to be effective for some individuals.
Myoclonic seizures are common in AS, typically occurring in young children and associated
with epileptiform changes on electroencephalographs. Prolonged episodes are associated
with developmental regression. In contrast, nonepileptic myoclonus typically begins
in adolescence or early adulthood and has no electroencephalogram (EEG) correlate,
alteration in consciousness, or regression but can significantly impact quality of
life.
Keywords
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Article info
Publication history
Published online: March 17, 2018
Accepted:
February 5,
2018
Received in revised form:
February 1,
2018
Received:
July 21,
2017
Identification
Copyright
© 2018 Elsevier Inc. All rights reserved.
