Juvenile Myoclonic Epilepsy (JME)
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Description
Juvenile myoclonic epilepsy (JME) is an idiopathic generalized epilepsy
syndrome. It presents in adolescents 12 to 18 years of age with myoclonic jerks,
generalized tonic-clonic seizures, and sometimes absence seizures. Myoclonic jerks,
typically but not exclusively upper extremity, often occur for months or more before
the seizures begin and must be specifically asked about as patients often think they
are a normal occurrence. Myoclonic jerks typically occur in the morning after
awakening and may vary among patients. Some patients describe them as brief tingling
sensations, others have myoclonic jerks similar to those the general population
experiences upon falling asleep, and others may have them so hard that they throw
objects. Leg jerks and sudden falls can also occur. No change in consciousness
occurs during the jerks. Seizures may be initiated by light (such as strobe lights),
lack of sleep, alcohol, and stress. Treatment usually needs to be lifelong.
Prevalence
The JME risk in the general population is approximately 1 case per
1000-2000 people. JME constitutes 5% to 10% of epilepsy, although this may be a low
number as JME is often misdiagnosed unless the myoclonic jerks are specifically
sought. [Grunewald: 1993] <
Diagnosis
JME is a clinical diagnosis, based on the myoclonic jerks and the
generalized tonic-clonic seizures (sometimes absence) in a normally developing child
with a normal exam sometimes in the setting of a family history of epilepsy. An EEG
when the patient is sleep deprived is helpful to confirm the diagnosis. EEG
typically shows rapid generalized polyspike waves during seizures. Neuroimaging in
the classical clinical setting is not necessarily required.
Etiology
JME is an idiopathic hereditary form of epilepsy not associated with
organic brain pathology. JME may be inherited (up to 50% of patients have family
members who have experienced seizures). [Delgado-Escueta: 1989] JME is genetically heterogeneous and although usually
thought of as an autosomal dominant disorder with reduced penetrance, may have
autosomal recessive forms as well. Currently, genes on several chromosomes have been
implicated in various populations. For details see [Omim: 2007].
Treatment
Valproic acid is currently the medication of choice although newer
medications such as lamotrigine and levetiracetam (which has been approved for
adjunctive therapy for treatment of myoclonic seizures by the FDA) are also being
used in increasing numbers due to better side effect profiles. Treatment is almost
always successful, although generally the patients will have to continue on
antiepileptic therapy on a very long-term basis.
Pearls and Alerts
Women of child-bearing age should be counseled regarding the possible
teratogenic effects of anti-epileptic medications on a fetus. [Hill: 2010] Women on oral contraceptives should understand that
anti-epileptic medications can interfere with oral contraceptive serum levels
(Antiepileptic Drugs and Contraception (US Pharmacist), [Hill: 2010]). Typical seizure activity restrictions should be
discussed and documented for this generalized epilepsy syndrome. Please see
Activity Restrictions in Children with Seizures.
Prognosis
Although children and youth with JME will often need to remain
indefinitely on medication, seizures are generally well controlled and intellectual
function is not affected.
Page Bibliography
Delgado-Escueta AV, Greenberg DA, Treiman L, Liu A, Sparkes RS, Barbetti A, Park MS, Terasaki PI.
Mapping the gene for juvenile myoclonic epilepsy.
Epilepsia.
1989;30 Suppl 4:S8-18; discussion S24-7.
PubMed abstract
Grunewald RA, Panayiotopoulos CP.
Juvenile myoclonic epilepsy. A review.
Arch Neurol.
1993;50(6):594-8.
PubMed abstract
Hill DS, Wlodarczyk BJ, Palacios AM, Finnell RH.
Teratogenic effects of antiepileptic drugs.
Expert Rev Neurother.
2010;10(6):943-59.
PubMed abstract / Full Text
Omim.
Epilepsy, Juvenile Myoclonic.
Omim, Johns Hopkins University; (2007)
http://www.omim.