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Juvenile Myoclonic Epilepsy

Juvenile Myoclonic Epilepsy Definition

Juvenile myoclonic epilepsy or JME is also called the Janz syndrome. This is a common type of idiopathic generalized epilepsy which represents 5-10% of all the types of epilepsies. This disease manifests primarily between the 12th-18th month and with myoclonus showing very early during the morning. Most of the patients also manifest absence and tonic-clonic seizures. Studies have shown at least six loci for JME of which 4 have specific causative genes. Most of the genes are ion channels together with the sole non-ion channel gene after manifesting effects on currents of ion channel.

Juvenile Myoclonic Epilepsy Diagnosis and Treatments

The diagnosis is usually made basing on the history of the patient. Records of EEG are also being used in confirming the illness. Before the administration of Carbamazepine, it is always necessary to ask for the history of fits during the morning especially among young persons. Carbamazepine aggravates these fits.

Juvenile Myoclonic Epilepsy Pathophysiology

CACNB4 is the one that encodes a calcium channel beta sub-unit. Beta sub-units are important because they regulate the calcium channel current amplitude, dependence on voltage, and it also regulates trafficking of the channel. The beta isoform which is encoded by CACNB4 is prevalent mostly in the cerebellum. On mice experiments, a natural null mutation leads to the phenotype that is ‘lethargic’ (a sign that is similar to JME). GABRA1 is the one responsible for encoding an alpha sub-unit of the GABA A receptor. One of the chief inhibitory neurotransmitter receptors is encoded by the GABA A receptor. There is one mutation on this gene which is linked with JME. A322D is situated on the third segment of proteins. This mutation also results into greatly lowered receptor sensitivity for GABA activation. CLCN2 is a gene that encodes chloride channel. The chloride channel is expressed mainly in regions of the brain that are inhibited by GABA. It is known to be an important factor in maintaining proper chloride reversal potential. This mutant activates potentials that are more positive when compared with the wild-type channels. Other loci include chromosomal gene or genes 15 (15q14) and also chromosome 6 (6p21) to JME. The causative genes found in these regions have not manifested, however.

Juvenile Myoclonic Epilepsy Symptoms and Signs

The common sign of JME is myoclonus which occurs during early hours in the morning. This does not often result into falls but rather object dropping (or unintentionally letting go of objects that are in one's hands). The attacks of myoclonia are more common on the legs and arms. Other types of seizures can also occur such as absence seizures and generalized tonic-clonic seizures.

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