Juvenile myoclonic epilepsy (JME) is one of the most common generalized epilepsy syndromes and typically presents in the teen years.
Clinical Presentation of JME
JME accounts for about 25% of all primary generalized epilepsy syndromes. It presents in patients between 8 and 22 years old who otherwise have minimal abnormalities and usually normal intelligence.
Classic hallmarks of JME including morning jerking movements (myoclonic jerks) that sometims manifests as “morning clumsiness.” Nearly everyone gets myoclonic jerks just before falling asleep, but myoclonic jerks in the morning are atypical and are almost always associated with JME.
Seizures are infrequent (sometimes only 1-2 lifetime seizures), but can be precipitated by sleep deprivation or photic stimulation. It is not unusual for a patient to present with a first time seizure after finals week, being sleep deprived from studying or after being up late celebrating.
Generalized tonic-clonic seizures usually occur upon awakening and in more than 90% of patients are preceded by myoclonic jerks. About a third of patients also have atypical absence seizures consistent of staring spells.
Genetics of Juvenile Myoclonic Epilepsy
Like other primary generalized epilepsies, the genetics of JME are complex. The genetic basis of the disease is polygenic, with mutations in EFHC1 (EF-hand domain containing protein 1) and GABRA1 (α1 subunit, of the GABAA receptor protein) being implicated. When the cause is a GABRA1 mutation, the disease can be inherited in an autosomal dominant fashion. The inheritence pattern is not clear for EFHC1 mutations.(1)
The classic interictal EEG pattern in JME consists of 4-6 Hz poly-spike and wave discharges. Runs of these discharges can often being triggered by photic stimulation.
The first line of treatment is valproic acid, which can provide complete seizure control in ~80% of patients. However, the use of valproic acid is complicated by its teratogencitiy in women of childbearing age, especially when used in combination with other anti-seizure medications like lamotrigine. Alternative medications includ levetiracetam, lamotrigine (monotherapy), topiramate and zonisamide.
Classicaly sodium-channel blockers like carbamazepine or oxcarbazepine should be avoided as they can sometimes worsen the disorder.
While JME is a lifelong condition, the prognosis is good due to rare generalized seizures that can, in the majority of patients, be controlled with a single anti-seizure medication.