Juvenile Myoclonic Epilepsy
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Juvenile Myoclonic Epilepsy
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Authors: Dorottya B. Kacsoh, University of Central Florida College of Medicine
Alison L. Christy, MD, PhD, Providence Pediatric Neurology at St. Vincent Medical Center—Portland, Oregon
Reviewed: February 2023 

SUMMARY

Juvenile myoclonic epilepsy (JME) is a common, readily controlled form of epilepsy. Epilepsy is a condition characterized by a tendency to have seizures.  

JME makes up about 8–10% of epilepsy cases in adults and adolescents. About half of cases are due to unknown causes. The other half are due to genetic causes. 

JME usually presents between the ages of twelve and eighteen in otherwise healthy children. Males and females are equally affected. JME does not cause intellectual or physical disability.  

JME is also known as Janz syndrome.

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Disorder Overview

DESCRIPTION

JME involves three different seizure types:

Myoclonic jerks.

Myoclonic jerks are irregular jerks.  

  • They most frequently occur within an hour of waking up.  
  • Jerks most commonly affect the arms. However, they may affect the legs as well. 
  • Jerks may affect only the fingers. Or, they can affect the entire arm. These jerks make people with JME prone to dropping objects. 
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Generalized tonic-clonic seizures (GTCS).

GTCS are convulsive seizures. During them, the person will fall and lose consciousness.  

  • GTCS are associated with: 
    • Tongue-biting  
    • Loss of bladder control  
    • These seizures typically last less than five minutes. They end on their own.  
    • After, the individual will appear confused and drowsy for minutes or even hours afterward. 
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Absence seizures.

Absence seizures occur when the individual stares straight ahead and is unresponsive. 

  • Absence seizures last about five to ten seconds.  
  • The person does not realize they have had a seizure. They will resume normal activity. 
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Myoclonic jerks are the first sign of JME. They may be subtle. So, they can easily be missed. A few months later, generalized seizures typically begin.  

Absence seizures are present in over one third of individuals. It is not necessary to have all three seizure types to have JME.  

A seizure lasting longer than five minutes is not likely to end on its own. So, rescue medicine may be given at that time. However, seizures are unlikely to cause brain damage unless they last longer than thirty minutes. 

A relatively rare complication of seizures in JME is status epilepticus. Status epilepticus occurs when either a seizure does not stop on its own after five minutes or at least two seizures occur without a return to normal.  

It is imperative to seek treatment if your child develops status epilepticus. There is an increased risk of death and disability.  

There is a low risk of death associated with JME. Sudden unexpected death in epilepsy (SUDEP) is a rare complication of epilepsy. It is unknown why SUDEP occurs. To learn more about SUDEP visit this webpage on the CNF website.  

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SIGNS AND SYMPTOMS

Children will have typical growth and development. Seizures begin during adolescence. Myoclonic jerks are the first sign. These are followed shortly by GTCS.  

Seizures are typically provoked by:  

  • Sleep deprivation  
  • Excessive alcohol consumption

Some seizures can be triggered by flashing lights. Stress may also be a contributing factor.

After seizures begin, children will not develop any intellectual or physical disabilities. Besides having seizures, they are otherwise healthy.

CAUSES

In about half of cases, the cause of JME is unknown. It is thought that JME runs in families. However, many people have no family members with epilepsy. Mutations in CACNB4, EFHC1, and GABRA1 genes are associated with JME.

LABORATORY INVESTIGATIONS

JME is diagnosed by obtaining a thorough history and an electroencephalogram (EEG) 

An EEG is a test that measures the electrical activity of the brain. Electrodes are taped to a person’s scalp.  EEGs are abnormal during seizures, but they may also be abnormal between seizures. JME has a characteristic pattern between seizures.  

Imaging studies are unnecessary in the diagnosis of JME. If an MRI is obtained, it will be normal in most cases.  

No lab work or genetic testing is needed to make a diagnosis.

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TREATMENT AND THERAPIES

Most cases of JME are readily controlled with daily medications. Many people will stop having seizures with a single medication. Sometimes, more than one will be necessary. Discuss medication options with the child’s provider. It is also important to discuss medications that can make seizures worse. They should be avoided. 

Seizures that last longer than five minutes are more likely to progress to status epilepticus. So, a rescue therapy should be used for seizures lasting longer than five minutes. Discuss seizure rescue therapy options with the child’s provider. There are multiple rescue therapy options to choose from.  

Vagus nerve stimulation (VNS) is an alternative to medication. VNS involves surgically inserting a device under the skin. This device sends electrical pulses to the brain. These control seizures before they start. VNS is reserved for those who fail treatment with multiple medications.  

The ketogenic diet is used in cases of epilepsy that do not respond to medical treatment. Because seizures are typically well controlled in JME, the ketogenic diet is rarely used. 

OUTLOOK

JME does not affect growth and development or academic performance. Children can participate in most regular activities. Teachers should be made aware of their diagnosis.  

JME is a lifelong condition. Symptoms typically lessen by the fourth decade of life. Individuals will require lifelong treatment with daily medication.  

The prognosis for JME is excellent. Most people will go on to live independently. With appropriate management, individuals may remain completely seizure-free.

Resources 

Epilepsy Leadership Council 

The Epilepsy Leadership Council is made up of individuals representing organizations serving individuals with epilepsy and their families, as well as professionals, and governmental organizations. The mission is to develop and coordinate among its members shared projects that will have a positive impact on the lives of individuals with epilepsy, focusing on those areas where working together produces greater efficiency and impact than working independently. 

For a list of more than 40 professional societies, patient advocacy organizations, and governmental agencies, please click here. 

Exploring Epilepsy 

This website provides information to help you better understand epilepsy. Learn more about epilepsy, gain knowledge about epilepsy medications, and feel empowered to manage epilepsy. 

Pediatric Epilepsy Surgery Alliance  

The Pediatric Epilepsy Surgery Alliance (formerly known as The Brain Recovery Project) enhances the lives of children who need neurosurgery to treat medication-resistant epilepsy. They empower families with research, support services, and impactful programs before, during, and after surgery. PESA’s programs include research-based, reliable information to help parents and caregivers understand when a child’s seizures are drug-resistant; the risks and dangers of seizures; the pros and cons of the various neurosurgeries to treat epilepsy; the medical, cognitive, and behavioral challenges a child may have throughout life; school, financial aid, and life care issues. PESA’s resources include a comprehensive website with downloadable guides, pre-recorded webinars, and virtual workshops; an informative YouTube channel with comprehensive information about epilepsy surgery and its effects; a private Facebook group (Education After Pediatric Epilepsy Surgery) with over 300 members; Power Hour (bi-monthly open forums and live virtual workshops on various topics); and free school training to help your child’s education team understand the impact of their epilepsy surgery in school. Their Peer Support Program will connect you with a parent who has been there. The Pediatric Epilepsy Surgery Alliance also hosts biennial family conferences and regional events that allow families to learn from experts, connect with other families, and form lifelong friendships. They also provide a travel scholarship of up to $1,000 to families in need to fund travel to a level 4 epilepsy center for a surgical evaluation. 

In addition, PESA has resources for medical professionals to assist in helping clinicians help the parents of their patients find the resources they need after surgery. Educators and therapists will also find helpful resources and information, including videos, guides, and relevant research. Patients who have undergone surgery are encouraged to register with the Global Pediatric Epilepsy Surgery Registry to help set future research priorities.

Child Neurology Foundation (CNF) solicits resources from the community to be included on this webpage through an application process. CNF reserves the right to remove entities at any time if information is deemed inappropriate or inconsistent with the mission, vision, and values of CNF. 

Research 

These are clinical trials that are recruiting or will be recruiting. Updates are made daily, so you are encouraged to check back frequently.   

ClinicalTrials.gov is a database of privately and publicly funded clinical studies conducted around the world. This is a resource provided by the U.S. National Library of Medicine (NLM), which is an institute within the National Institutes of Health (NIH). Listing a study does not mean it has been evaluated by the U.S. Federal Government.  Please read the NLM  disclaimer for details.    

Before participating in a study, you are encouraged to talk to your health care provider and learn about the  risks and potential benefits.

For more information about participation in clinical trials, check out our education hub on the topic here.  

Information for research and clinical trials specific to Juvenile Myoclonic Epilepsy can be found on the Pediatric Epilepsy Surgery Alliance website.  

The information in the CNF Child Neurology Disorder Directory is not intended to provide diagnosis, treatment, or medical advice and should not be considered a substitute for advice from a healthcare professional. Content provided is for informational purposes only.  CNF is not responsible for actions taken based on the information included on this webpage. Please consult with a physician or other healthcare professional regarding any medical or health related diagnosis or treatment options. 

References

About VNS Therapy [Internet]. Livanova; 2023 [cited 2023 Jan 15]. Available from: https://www.livanova.com/epilepsy-vnstherapy/en-us. 

Panayiotopoulos CP. A clinical guide to epileptic syndromes and their treatment: Based on the new ILAE Diagnostic scheme. Oxfordshire, UK: Bladon Medical Pub.; 2002.   

Amrutkar C, Riel-Romero RM. Juvenile Myoclonic Epilepsy. [Updated 2022 Aug 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK537109/.

Gidal B, Detyniecki K. Rescue therapies for seizure clusters: Pharmacology and target of treatments. Epilepsia. 2022 Sep;63 Suppl 1(Suppl 1):S34-S44. https://doi.org/10.1111/epi.17341. PMID: 35999174; PMCID: PMC9543841. 

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