JUVENILE & MYOCLONIC SEIZURES aka JME EPILEPSY including Lennox-Gastaut

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JUVENILE & MYOCLONIC SEIZURES AKA JME EPILEPSY
including Lennox-Gastaut




Here are some partial quotes:



JME / MYOCOLINIC SEIZURES - from eMed

Background

Juvenile myoclonic epilepsy (JME) is an idiopathic generalized epileptic syndrome characterized by myoclonic jerks, generalized tonic-clonic seizures (GTCSs), and sometimes absence seizures. JME is relatively common and usually responds well to treatment with appropriate anticonvulsants. However, JME is frequently misdiagnosed until the patient is specifically asked about the leading symptom, jerky movements occurring primarily within the first couple of hours after awakening. Other keys to the diagnosis include normal intelligence, onset around adolescence, GTC seizures occurring shortly after awakening, family history of the condition, and seizures after precipitating factors such as sleep deprivation or psychological stress. Although patients usually require lifelong treatment with anticonvulsants, their overall prognosis is generally good.

Brief history of JME

In 1867, Herpin was the first to describe a probable case of JME.1 He described a bright boy aged 13 years who developed upper-body jerks that progressed to "full seizures" 3 months later. Later, Rabot2, Lundborg3, and other physicians reported patients who had similar seizures, and terms such as impulsions were used to describe the myoclonic jerks. Janz and Mathes published a monograph about patients with "propulsive petit mal epilepsy" in 1955.4 In 1957, Janz and Christian published observations of a group of patients with a syndrome now known as JME.5 Janz named this syndrome "impulsive petit mal epilepsy." Lund introduced the term juvenile myoclonic epilepsy in 19756, and the International League Against Epilepsy has adopted this term.

Definition

Under the proposal for revised classification of epilepsies and epileptic syndromes, in 1989 the Commission on Classification and Terminology of the International League Against Epilepsy defined JME (impulsive petit mal) as follows: "Impulsive petit mal appears around puberty and is characterized by seizures with bilateral, single or repetitive, arrhythmic, irregular myoclonic jerks, predominantly in the arms. Jerks may cause some patients to fall suddenly. No disturbance of consciousness is noticeable. Often, there are GTCS and, less often infrequent absences. The seizures usually occur shortly after awakening and are often precipitated by sleep deprivation. Interictal and ictal EEG have rapid, generalized, often irregular spike-waves (SW) and polyspike-waves (PSW); there is no close phase correlation between EEG spikes and jerks. Frequently the patients are photosensitive. The disorder may be inherited and sex distribution is equal. Response to appropriate drugs is good."

In one case of identical twins in the first author's experience (JEC), one twin exclusively had absences and had been treated only with ethosuximide since childhood. She never had myoclonic or generalized tonic-clonic seizures, and her seizures were well controlled with a drug that was considered ineffective in the treatment of these other types of seizures. The other twin first presented with generalized tonic-clonic seizures at the age of 18 years; in retrospect, she had noticed morning myoclonic jerks for 2 years before her presentation. She had never had absences. Their EEGs showed typical polyspike and slow-wave discharges interictally in both cases with no obvious difference between the twins.
Pathophysiology

Etiology

JME is an idiopathic generalized epilepsy syndrome. It is not associated with conditions such as head trauma, brain tumor, or encephalitis. Neuropathologic studies involving specialized staining techniques in patients with primary generalized seizures (including a few with a diagnosis of JME) have revealed microscopic brain alterations. Changes include an increase in the number of partially dystopic neurons in the stratum moleculare, white matter, hippocampus, and cerebellar cortex; an indistinct boundary between the cortex and the subcortical white matter and between lamina 1 and 2; and a columnar arrangement of cortical neurons. These findings are termed microdysgenesia and have been interpreted as a manifestation of minimal developmental disturbances. However, results of routine pathologic analysis of brain specimens from patients with JME are typically normal.

The exact cause of this disorder remains unknown. However, considerable progress has been made in the understanding of some families with specific mutations that yield the clinical phenotype of JME. Some of the known mutations result in abnormalities in ion channel proteins such as the beta-4 subunit of calcium channels and the chloride channel 2 protein. A protein called myoclonin has been identified. Its function remains uncertain but has been implicated in apoptosis, cell division, and cell migration. These functions might explain the subtle abnormalities in cortical migration reported in the neuroimaging of some patients with JME.

Genetics

JME is an inherited disorder, but the exact mode of inheritance is not clear. About a third of patients with JME have a positive family history of epilepsy. About 17-49% of patients with JME have relatives who have epileptic seizures, including parents (about 4%) and children (about 7%). The risk of expressing clinical JME might be slightly higher in female individuals than in male individuals and in relatives of people with JME. However, some studies have shown similar sex-related risks.

Progress in identifying genetic mutations in patients and families with JME has been considerable. Dr. Delgado-Escuet has written a comprehensive review about the genetics of JME.7 The syndrome of JME likely consists of many genetic diseases that result in a similar electroclinical syndrome. See Causes for a further discussion on specific mutations.

Although investigators in most studies have presumed that JME is an autosomal dominant condition (ie, 50% risk of inheritance), it has incomplete penetrance, which means that some individuals who inherit the JME gene or genes do not express clinical JME. However, their children may inherit the JME genes and express clinically obvious disease. To an untrained observer, the disease seems to skip generations. For relatives of a patient with JME, the risk of having clinically obvious JME is small: 3.4% in parents, 7% in siblings, and 6.6% in children.
Frequency
United States

The risk of JME in the general population is estimated to be 1 case per 1000-2000 people. JME is a relatively common idiopathic generalized epilepsy. It represents about 5-10% of all epilepsies; however, the exact figures may be higher, as the condition is often misdiagnosed.
International

The incidence and prevalence of JME appear to be the same in all the populations that have been studied.
Mortality/Morbidity

Sudden unexpected death in epilepsy (SUDEP) and accidental morbidity and mortality have been observed as in other epileptic syndromes with generalized tonic clonic seizures. Seizure precautions to minimize these risks are discussed later in this chapter.
Race

No systematic racial differences have been observed. However, it is likely that some specific genetic mutations among the different types described in families with JME might be more prevalent among different racial groups. For example, the myoclonin (EFHC1) mutation has been found in 9-20% of Mexican-American families with JME, but only in 3% of Japanese families with this disorder.7
Sex

Findings from some studies suggest that JME is slightly more prevalent among females than males. The reason is unknown. However, data from other studies indicate similar prevalences in both sexes.
Age

* JME typically begins in adolescence. Although the age of onset varies from 6-36 years, symptoms typically begin in adolescents aged 12-18 years.
* Myoclonic jerks, GTCSs, and absence seizures all have an age-related onset in JME.
* If absence seizures are a feature, they usually begin between the ages of 5 years and 16 years. Myoclonic jerks may follow 1-9 years later, usually around the age of 15 years. GTCSs typically appear a few years later than myoclonic jerks.
* Why the onset of this genetic disorder is delayed until adolescence is unclear.

MYOCLONIC SEIZURES - Epilepsy Foundation

Myoclonic seizures are rapid, brief contractions of bodily muscles, which usually occur at the same time on both sides of the body. Occasionally, they involve one arm or a foot. People usually think of them as sudden jerks or clumsiness. A variant of the experience, common to many people who do not have epilepsy, is the sudden jerk of a foot during sleep. First aid is usually not needed, however, a person having a myoclonic seizure for the first time should receive a thorough medical evaluation

JME, MYOCLONIC, LENNOX-GASTAUT SEIZURES by Epilepsy.com

Myoclonic (MY-o-KLON-ik) seizures are brief, shock-like jerks of a muscle or a group of muscles. "Myo" means muscle and "clonus" (KLOH-nus) means rapidly alternating contraction and relaxation—jerking or twitching—of a muscle.

Even people without epilepsy can experience myoclonus in hiccups or in a sudden jerk that may wake you up as you're just falling asleep. These things are normal.

In epilepsy, myoclonic seizures usually cause abnormal movements on both sides of the body at the same time. They occur in a variety of epilepsy syndromes that have different characteristics:

• 
  * Juvenile myoclonic epilepsy: The seizures usually involve the neck, shoulders, and upper arms. In many patients the seizures most often occur soon after waking up. They usually begin around puberty or sometimes in early adulthood in people with a normal range of intelligence. In most cases, these seizures can be well controlled with medication but it must be continued throughout life.
  * Lennox-Gastaut syndrome: This is an uncommon syndrome that usually includes other types of seizures as well. It begins in early childhood. The myoclonic seizures usually involve the neck, shoulders, upper arms, and often the face. They may be quite strong and are difficult to control.
  * Progressive myoclonic epilepsy: The rare syndromes in this category feature a combination of myoclonic seizures and tonic-clonic seizures. Treatment is usually not successful for very long, as the patient deteriorates over time.

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