Juvenile Myoclonic Epilepsy – Symptoms – Prognosis – Treatment
Types of Seizures in JME – Seizure Triggers – Cause – Genetics and Inheritance – Diagnosis – Effective and Contraindicated Drugs in Juvenile Myoclonic Epilepsy
Juvenile Myoclonic Epilepsy (JME)
Juvenile myoclonic epilepsy is one of the most common epilepsy syndromes (25% of idiopathic/genetic generalized epilepsy cases, or 10% of all epilepsy cases).
It is probably more common in girls.
JME typically starts in adolescence.
It is a lifelong condition with tendency of improving later in life.
There are 3 types of seizures in Juvenile Myoclonic Epilepsy: Myoclonic, Generalized Tonic-clonic, and Absence (see “Seizure Types” page).
Pathophysiology, Genetics, Epidemiology of JME
Neurons in some areas of the brain are hyperexcitable for unknown reasons.
Some JME cases run in families with a variable type of inheritance. There is no single gene responsible for this epileptic syndrome. Only 9% of juvenile myoclonic epilepsy can be attributed to the particular genetic abnormality (EFHC1). Fourteen more genes are suspected.
Functional abnormalities in the frontal part of the brain can be detected on sophisticated brain imaging.
The diagnosis of juvenile myoclonic epilepsy is typically made between 12 and 18 years of age.
It is believed that JME is more common in girls, but not all the studies confirm this.
Symptoms of Juvenile Myoclonic Epilepsy
Myoclonus is an involuntary shock-like, sudden muscle conduction; it is often described by patients as jerk or spasm. They come in singles or in series and are similar to the jerky movements that most people experience upon falling asleep.
In JME, myoclonus more often involves the upper part of the body, commonly, either one or both arms. The jerks may be either obvious, like dropping held objects due to the involuntary movement, or subtle, like a slight finger twitch. Myoclonus in JME rarely involves legs, so falls are not common.
Mild myoclonic movements may be missed and the right diagnosis is often made after the first generalized seizure. Even then, you have to specifically ask the patient about unusual involuntary movements.
Some patients might be treated for generalized epilepsy with inappropriate medications for years without proper diagnosis. Some anti-epileptic drugs might precipitate myoclonus, so the right diagnosis is important.
Myoclonus in JME is most common in the morning upon awakening and in the evening, when tired. It is provoked by lack of sufficient sleep, flashing light, and alcohol.
Generalized Tonic-Clonic Seizures (GTCS)
Close to 100% of patients with Juvenile Myoclonic Epilepsy have at least one GTCS. Generalized seizures are not any different from other types of generalized epilepsy.
Up to 40% can experience focal seizures: versive, tonic, or clonic.
Generalized seizures may be precipitated by the same factors as myoclonus.
In some patients, generalized seizures are very occasional, such as once in a few years or even a single seizure over a lifetime.
Absence is the least common type of seizures in juvenile myoclonic epilepsy. They affect about a third of patients with JME.
When present, absence seizures are the first symptom of the syndrome and they usually start years prior to myoclonus.
Absences are usually less frequent than in juvenile absence epilepsy and severity of loss of consciousness is variable. Unlike classical absences, in JME coming back to senses might be gradual and loss of awareness might be incomplete.
Cognitive, Behavioral, and Psychiatric symptoms
About half of JME patients experience anxiety and mood disorders; a quarter has some personality traits of impulsivity, emotional instability, and difficulty accepting social cues.
Cognitively, there are no significant problems.
Neuropsychological testing reveals mild frontal lobe dysfunction: verbal fluency, abstract reasoning, mental flexibility, processing speed, planning, and organization. There are some controversies if these findings are related to JME of to the fact of chronic disease and multiple medications.
Diagnosis of JME
Conventional brain imaging (Brain MRI or CT) have no use in JME diagnosis.
Type of seizures, family history, and age of onset define the diagnosis.
Electroencephalogram (EEG) has specific findings in about 75% of patients. Sleep recording brings it up to 100%.
A typical finding on EEG is a presence of 4 to 6 Hz bilateral polyspike and slow wave discharges dominating in the frontal lobes. Other types of spikes and spike and waves (2.5 to 4.5 Hz), either bilateral symmetrical or focal and single, are less common.
During the myoclonic seizure there are 3 to 4 Hz polyspike-waves predominantly in the frontal lobes. In absence seizure there are generalized spike-waves discharges with frequency slightly less than 3 Hz.
Background of EEG recording should be normal.
Flashing light bring up abnormal EEG discharges in significant percentage of patients, especially when prolonged.
Treatment of Juvenile Myoclonic Epilepsy
Valproate is a drug of choice in JME. It controls well all three types of seizures. It is effective in 80% of patients and is relatively well tolerated.
Valproate has to be avoided in women of childbearing age, whenever possible, due to strong association with birth defects.
Liver toxicity, pancreatitis, thrombocytopenia, weight gain, and hair loss are other major concerns associated with valproate.
Levetiracetam provides a decent seizure control in juvenile myoclonic epilepsy with fewer side effects. Good tolerability makes it the second most appropriate medication when valproate is undesirable or contraindicated.
Lamorigine may exacerbate myoclonus while offering control over other types of seizures. It is usually very well tolerated.
The major concern is a life-threatening rash (Stevens – Johnson syndrome) especially in children, in combination with valproate, and with fast dose escalation.
Clobazam or Clonazepam may be used as an adjunctive to Lamotrigine therapy for myoclonus control.
Insufficient seizure control with one medication may warrant a combination of drugs. Combination of Lamotrigine and Valproate may produce powerful seizure control. On the other hand, this combination increases chance of life threatening complications especially in children under 12 yo.
Topiramate is a valid alternative for seizure control in JME. It is often poorly tolerated, which significantly limits its use.
Carbamazepine, Phenytoin, Oxcarbazepine must be avoided. They tend to exacerbate absence and myoclonic seizures while offering some control of GTCS.
Gabapentin, Pregabaline, Tiagabine, and Vagabatrin are contraindicated. They may aggravate all seizure types and cause absence status epilepticus.
Lifestyle in JME
JME sufferers have to avoid insufficient sleep, alcohol, and, for some, flickering lights.
Juvenile Myoclonic Epilepsy is a lifelong disease with a tendency to ease up in the fourth decade of life.
About 20% can reach a long lasting remission and around 15% have intractable and hard to control seizures.
The prognosis is worse in patients with all three types of seizures and psychiatric problems. The majority of JME sufferers require long-term treatment to control the seizures.
Some patients with milder forms choose to have no treatment. It actually makes sense, if myoclonic seizures are occurring exclusively due to sleep deprivation or alcohol intake; and GTCS are in single digits over a lifetime.
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