Prevalence
8% to 10% among patients with epilepsies.

Age at onset
Absences: 5 to 16 years (peak at 10 years); myoclonic jerks: 8 to 26 years (peak at 14 to 15 years); generalized tonic-clonic seizures (GTCS): months after onset of myoclonic jerks.

Sex
Males = females.

Neurological and mental state
Normal.

Genetics
Probably complex and polygenic inheritance. Susceptibility loci in chromosome 6p11-12 (EJM1) and 15q14 (EJM2). Genes C6orf33 or BRD2 (RING3) in the EJM1 region. Genetic heterogeneity is common.

Clinical manifestations
(1) myoclonic jerks on awakening (all patients) are the defining features; (2) GTCS (nearly all patients), occurring usually after a series of myoclonic jerks; (3) typical absences (more than 1/3 of patients) are mild and often inconspicuous.

Timing
Nearly exclusively 15 to 30 min after awakening.

Seizure-precipitating factors
Mainly sleep deprivation, fatigue, and excessive alcohol intake. Others include photosensitivity (1/3), mental stress, excitement, and mental and psychological arousal.

Inter-ictal EEG
In untreated patients, EEG is usually abnormal, with generalized discharges of irregular 3 to 6 Hz spike/polyspike waves. Focal abnormalities occur in 1/3. Also 1/3 show photoparoxysmal responses. A normal EEG in a patient suspected of having JME should prompt an EEG on sleep and awakening.

Ictal EEG
Myoclonic jerks = generalized multiple spikes. Absences = generalized 3 to 6 Hz multiple spike waves.

Prognosis
All seizures are probably lifelong, although patients show improvement after the age of 40. Severity varies from mild myoclonic jerks to frequent and severe falls and GTCS if not appropriately treated. Seizures are generally well controlled with appropriate medication in up to 90% of patients. Patients with all 3 types of seizures are more likely to be resistant to treatment.

Differential diagnosis
Misdiagnosis is common (~90%), resulting in avoidable morbidity. Factors responsible include lack of familiarity with JME, failure to elicit a history of jerks, misinterpretation of absences or jerks as focal seizures, and high prevalence of focal EEG abnormalities.

Management options*
Advice with regard to circadian distribution, lifestyle, and seizure precipitants are as important as drug treatment.

Valproate is the most effective AED but with significant concerns in the treatment of women. Control and open studies indicate that levetiracetam is probably one of the most promising of all other AEDs for JME.

Clonazepam is effective for persistent myoclonic jerks. Lamotrigine, topiramate, and zonisamide are possible treatment options.

Contraindicated drugs include vigabatrin#, tiagabine, carbamazepine, oxcarbazepine, phenytoin, pregabalin and gabapentin.

*Expert opinion, please check FDA-approved indications and prescribing information
#Not approved the FDA

See also: http://professionals.epilepsy.com/page/epilepsy_juvenilemyoclonic.html

This page was adapted from:

The educational kit on epilepsies
The epileptic syndromes
By C. P. Panayiotopoulos

Originally published by MEDICINAE
21 Cave Street, Oxford OX4 1BA
First published 2006 and reprinted in 2007