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Juvenile Myoclonic Epilepsy of Janz (JME)
Marissa A. Broadley, BS, School of Public Health, New York Medical College, Valhalla, New York; Martin L. Kutscher MD, Departments of Pediatrics and Neurology, New York Medical College, Valhalla, New York.
Historical Background and Epidemiology
Juvenile Myoclonic Epilepsy of Janz (JME)is an idiopathic generalized epilepsy syndrome. The types of seizures that can occur in patients with JME are myoclonic jerks, generalized tonic clonic seizures (GTCS), and absence seizures. Herpin first described this syndrome in 1867. He presented a patient with jerks starting at the age of 13, which progressed to "full seizures."
The age of onset is 6-36 years of age; most seizures begin between the ages of 12-18. The seizures typically occur in the morning shortly after awakening. They are bilateral myoclonic jerks (quick startle-like movements) that most often involve the arms and shoulders. If the myoclonic jerk is violent enough, the patient may drop things or fall to the floor. Importantly, there is no loss of consciousness during these seizures. Often, the child has become accustomed to these spells and never mentions them to their parent. Whenever any seizure disorder is being considered, it is imperative to initiate inquiry about myoclonic spells.
Generalized tonic clonic (or "grand mal") seizures occur in 95% of all JME patients. Absence ("staring spells") seizures precede myoclonic jerks in 30% of the cases. The intellectual ability of persons with JME of Janz is normal. Physical examination, CT scan and MRI are also normal. The EEG pattern typically shows 10 – 15 Hz polyspikes and intermittent slow wave discharges. However, some patients with JME of Janz have normal EEG patterns. Some triggers of myoclonic jerks include: sleep deprivation, psychological stress, alcohol use, photic stimulation, menses and the time of day. It is a lifelong syndrome that can usually be well controlled.
One person in every 1,000 – 2,000 has this disorder worldwide, which occurs slightly more often in females. JME accounts for approximately 7% of all idiopathic epilepsy patients. However, there are probably more instances of JME that are misdiagnosed or ignored.
JME is an inherited disorder. One third of people with JME have a family member with epilepsy. Ten percent of all relatives without known seizures will still have abnormal EEG patterns. Brain tumor, brain trauma and encephalitis are not causes of this syndrome. Hence it is considered idiopathic.
Differential Diagnosis includes:
Classic Absence Epilepsy, also known as petit mal epilepsy. These seizures typically last less than 20 seconds, and usually involve a stare and movements of the mouth and hands. These seizures most often begin in childhood and are outgrown 75% of the time.
Generalized Tonic-Clonic Seizures, a type of grand mal seizure that involves the whole brain. Loss of consciousness, shaking, falling and jerking occur.
Myoclonus, a sudden jerk in the process of falling asleep. This may be perfectly normal.
Course and Prognosis
JME of Janz is not typically outgrown. Many patients do very well on one anticonvulsant.
Psychiatric disorders are higher among this cohort. In one study, 7 out 23 patients with JME of Janz reported psychiatric disorders--most often depression. This study also concluded that 18% of first-degree relatives of patients with JME reported a psychiatric diagnosis.
There are several antiepileptic drugs that can be used to treat JME of Janz: valproate (Depakote, Depakene), acetazolamide (Diamox), clonazepam (Klonopin), phenobarbital, primidone (Mysoline), lamotrigine (Lamictal) and topiramate (Topamax). Some medications may trigger myoclonic seizures. These include: carbamazepine (Tegretol), ethosuximide (Zarontin) and phenytoin (Dilantin). Most patients with JME of Janz have seizure control on just one anticonvulsant.
The typical drug of choice to treat JME of Janz is sodium valproate (Depakote, Depakene). 80% of patients who suffer from JME gain seizure control on valproate. Lamotrigine (Lamictal) is good alternative drug. This drug is fairly new in the United States but has been used in Europe for some time. Even though it has been highly effective treating JME of Janz, it has been reported to sometimes trigger myoclonic seizures.
Acetazolamide (Diamox), clonazepam (Klonopin), phenobarbital and primidone (Mysoline) are used less often to treat JME of Janz. These drugs are often used as secondary drug treatment. Physicians should respect the patient’s possible complaint of "not feeling right" with AEDs and should consider changing the medication if this occurs. Surgery is not considered in patients with JME of Janz.
Juvenile Myoclonic Epilepsy (JME) of Janz is characterized by:
Onset in adolescence of myoclonic, absence, and tonic/clonic seizures. (Thus, the existence of possible co-existent myoclonic seizures should be investigated while evaluating absence or tonic/clonic seizures.)
Unlikely to be outgrown.
Associated with normal intelligence.
Good prognosis to be controlled only by specific anticonvulsants, including valproic acid and lamotrigine.
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Sander, Thomas, et al. Progress in Mapping the Gene for Juvenile Myoclonic Epilepsy (EJM1) within Chromosomal Region 6p21.3. Philadelphia: Wrightson Biomedical Publishing Ltd., 2000.
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Disclaimer: This web site is presented as a resource to patients by Pediatric Neurological Associates. There are no commercial sponsors. This information does not constitute medical advice; nor is it a substitute for discussion between patients and their doctors. The views of cited references do not necessarily represent the views of our staff. This information was last modified 06/06/02.
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