By: Nazneen Khan
Epilepsy is defined as a disorder characterized by two or more seizures which occur twenty-four hours apart. Myoclonic epilepsy is a generalized epilepsy where all parts of the brain show abnormal electrical activities. This type of epilepsy presents short, rapid, and uncontrollable muscle jerks and rhythmic contractions which occur more than once in a person’s lifetimes causing problems in normal activities. Furthermore, myoclonic epilepsy is of two types: juvenile myoclonic epilepsy and progressive myoclonic epilepsy. There are numerous causes and factors linked to epilepsy, but research findings show evidence for genetics and infection which are discussed in detail in this paper. Juvenile myoclonic epilepsy and progressive myoclonic epilepsy are two types of myoclonic epilepsy that are distinguishable based on the symptoms, progression, and disease they have. Treatment options for myoclonic epilepsy include many antiepileptic drugs as well as non-medicinal ones.
Myoclonic Epilepsy: Understanding the Etiology, Types, and Treatments
In order to better understand myoclonic epilepsy, it is important to first define what epilepsy is. Epilepsy is a neurological disorder which is commonly characterized by the occurrence of seizures. According to Mayo Clinic, seizures occur when the brain undergoes an electrical disturbance causing a change in a person’s level of awareness and behavior. There are numerous signs and symptoms that can alert someone when a seizure is occurring such as temporary confusion, a dazed stare, unusual movements of the extremities, and loss of consciousness (Mayo Clinic, 2021). Because doctors and clinicians classify seizures based on the location of the abnormal brain activities, there are two main categories where seizures can fall. If abnormal brain activity stems from both hemispheres of the brain, the seizure is categorized as generalized whereas if only one part of the brain is involved it is called focalized. Moreover, when sudden, brief, jerking movements occur in the upper body, arms, and legs, the seizure is defined as myoclonic. If a person has two episodes of unprovoked myoclonic seizures that occur twenty-four hours apart, he will be diagnosed with myoclonus epilepsy. Research about myoclonic epilepsy is limited due to research and misdiagnosis from doctors; however, this paper will discuss what is already known about the etiology, different types of myoclonic epilepsy, and treatments surrounding the disorder.
A patient diagnosed with myoclonic epilepsy will have episodes of seizures that deal with abnormal movements of the body’s muscles which are quick and involuntary. Myoclonus itself is defined as brief rhythmic contractions of the muscles such as with the diaphragm during hiccups or when a person experiences a sudden jerk-like feeling soon after falling asleep. These behaviors are normal and pose no serious harm to the person. However, the clinical prognosis of myoclonus becomes an issue when it appears as a seizure which can last longer than a few seconds, recur throughout a person’s lifetime, and cause unusual muscle contractions. Myoclonic epilepsy can be further categorized based on the subtle characteristics and symptoms present in the person. The three types of epilepsy discussed here are juvenile myoclonic epilepsy and progressive myoclonic epilepsy. It is not well known as to the etiology surrounding epilepsy for some people although it is thought that half the people who are diagnosed with epilepsy may be linked to a specific cause. The main categories of causes include the following: genetic, infection, and brain tumor.
Genetic and Infection as Causes
Genetic causes of myoclonus epilepsy occur because of a change in the DNA (deoxyribonucleic acid) sequence in cells. Parts of an organism’s DNA encodes for proteins and special enzymes. When there is a mutation or disruption to the DNA sequence, the translated protein will therefore be abnormal. Inherited gene changes happen when a person inherits the affected gene from their parents. Their inheritance can be of different types such as autosomal dominant, autosomal recessive, and X-linked. When a person is born, he acquires one chromosome from his father and the other chromosome from his mother. With autosomal dominant disorders, the gene is defined as dominant if the gene acquired from either the father or mother overshadows the “weaker” gene and is sufficient to cause a disorder. According to an article, one type of autosomal dominant disorder pattern is caused by a missense mutation in an alpha subunit of a GABA receptor (Gisoul and Grisar et all, 2019). Because the neurotransmitter GABA is responsible for an inhibitory effect in the brain, once the GABA receptor subunits mutate into altered shape, the receptor is not able to function normally; and thus, it cannot allow the neurotransmitter to bind to the receptor properly and perform its function. The autosomal recessive is another case where the gene in question will be expressed and passed down to the offspring if both the father and the mother possess the allele of the gene. Epilepsy which concerns X-linked inheritance deals with the sex chromosomes of the person. A person is biologically determined to be male if he has the sex chromosome XY whereas a person determined to be female has XX. Since males have only one X chromosome, any genes which are passed on which are located on the X chromosome, is enough to cause the disorder.
Epilepsy can also be caused by infection which is the most common cause for seizures. Malaria, a blood disease which is caused by the Plasmodium parasite, usually infects humans through the mosquito vector. Although malaria is present in red blood cells, if it makes its way to the brain, it is then called cerebral malaria which can lead to a potential cause for seizures and other neurological disorders. Malaria can cause high fevers which can in turn lead to seizures (febrile seizures) (Casassa, 2020). Other causes and factors include brain injuries, use of alcohol, and abnormal brain development.
Juvenile Myoclonic Epilepsy
Myoclonic epilepsy can start at any age and range from mild to severe symptoms. The way doctors and psychiatrists categorize myoclonic epilepsy is based on many factors such as age of incidence, signs and symptoms, and the inclusion of different causes. One of the types of myoclonic epilepsy is juvenile myoclonic epilepsy (JME) or also known as Janz. JME is a type of generalized epilepsy with myoclonic, generalized tonic-clonic, and absence seizures, and it occurs in about 5%-11% of all epilepsies accounting for both males and females with similar prevalences (Reganathan and Delanty, 2003). Generalized tonic-clonic seizures are seizures which first begin with the tonic phase (stiffening of the muscles) and then the clonic phase (rhythmical jerking). With the tonic phase, the body stiffens up and the person usually loses consciousness. Because muscles stiffen up, breathing may become difficult, and the person may produce a slight cry. Once past the tonic phase, the clonic phase presents rapid jerking motions of the arms and legs for a few minutes. Afterwards, a person may experience sleepiness, confusion, and irritability. Breathing is also hindered and may cause the person to turn blue (Epilepsy Foundation Kiriakopoulos, 2017). Absence seizures are defined as, “An absence seizure causes a short period of “blanking out” or staring into space. Like other kinds of seizures, they are caused by brief abnormal electrical activity in a person’s brain” (Epilepsy Foundation Kiriakopoulos, 2019). JME starts at puberty and the onset of the different types of seizures varies throughout. According to Juvenile myoclonic epilepsy: under-appreciated and under-diagnosed:
Eighty percent of patients with JME begin having seizures between ages 12 and 18 with a mean age of onset of 14.6 years. The mean age of onset for GTCS is 15.5 years, absence seizures 11.5 years, and myoclonic seizures 15.4 years. (7) Earlier onset is seen in photosensitive patients. Absence seizures typically begin between ages 5 and 16 years. Myoclonic jerks follow between one and nine years later followed by GTCS a few months later. Approximately 3%-8% of childhood absence epilepsies evolve into JME.
Progressive Myoclonic Epilepsy
In an article published in the European Journal of Epilepsy, progressive myoclonic epilepsy (PME) is defined as “a group of uncommon clinically and genetically heterogeneous disorders (mainly autosomal recessive), characterized by myoclonus, generalized epilepsy, and progressive neurological deterioration, including dementia and ataxia another type of myoclonic epilepsy though it is” (Orsini and Valetto et al, 2019). PME has an onset during infancy, childhood, and adulthood but late childhood and adolescence is more common. This type of myoclonic epilepsy is rare. Going further, PME has numerous subtypes including Unverricht-Lundborg disease (ULD), Lafora disease, and others. ULD shows a pattern on autosomal recessive inheritance, accounting for equal prevalence in males and females. Studies have shown that there is a mutation on the Cystatin B gene (CTSB) which is a gene which helps protect the cells from endogenous protease. Proteases are enzymes which break down proteins. Decrease in CTSB has shown to exhibit hyperexcitability. In ULD, myoclonus and generalized tonic-clonic seizure (GTCS) are present in patients, yet GTCS has been found to disappear over time. Ataxia, a neurological disorder of the brain which affects the cerebellum and impair balance and gain in a person, is also a symptom in ULD. One of the triggers in about 80%-100% patients is photosensitivity, though after 15 years, this number decreases to about 30% (Orsini and Valetto et al, 2019).
Anti-Epileptic Drugs (AED) and Non-medicinal Treatments
Treatments for myoclonic epilepsies include many drug medications and are countless. Some of these include Valproate (VPA), Lamotrigine (LTG), and Levetiracetam (LEV) (Striano and Belcastro, 2012). VPA had been the only drug used against generalized and focal epilepsies until the 1990’s. In a few randomized double-blind studies, 25% of the patients assessed were seizure-free during the entire study and in adolescence studies, 16 out of 23 had full seizure-control. Thus, VPA is usually used as a first choice when treating myoclonic epilepsies of any kind.
Lamotrigine is also another drug of choice for treatments for people who experience JME. It is considered better for women to use Lamotrigine due to lower risks of malformation during pregnancy. Levetiracetam, another drug of choice, was tested in double-blind, placebo-controlled trial and shown “to be effective in controlling generalized tonic-clonic seizures, myoclonic seizures and all seizures type in patients with IGE compared with placebo” (Striano and Belcastro, 2012). A non-medicinal approach to treatment of myoclonic epilepsy includes regulating one’s sleep cycle, reducing the intake of alcohol, and incorporating a ketogenic diet.
Though much has been discussed in this paper regarding myoclonic epilepsy and the causes, types, and treatments surround it, more still must be discovered about this disorder and its clinical features. In order to better understand and reduce misdiagnosis and underappreciation of myoclonic epilepsy, primary doctors, psychiatrists, and clinical personnel need to undergo more training in figuring out distinct signs and symptoms. Also, patients need to feel comfortable regarding their disorders and medical problems and be willing to share changes they may be undergoing so that better treatments and diagnoses can be given. Without data, myoclonic epilepsy will remain a mystery in the medical community.
Barot, N., Margiotta, M., Nei, M., & Skidmore, C. (2020). Progressive myoclonic epilepsy: myoclonic epilepsy and ataxia due to KCNC1 mutation (MEAK): a case report and review of the literature. Epileptic Disorders : International Epilepsy Journal with Videotape, 22(5), 654–658. https://doi-org.proxy.westernu.edu/10.1684/epd.2020.1197
Casassa. C. and Kiriakopoulis, E. (2020). Malaria and its Relation to Epilepsy. Epilepsy Foundation. Retrieved from: https://www.epilepsy.com/learn/epilepsy-due-specific-causes/specific-infections-associated-epilepsy/malaria-and-its-relation-epilepsy
Cedars-Sinai (2021). Myoclonic Epilepsy. Cedars-Sinai. Retrieved from: https://www.cedars-sinai.org/health-library/diseases-and-conditions/m/myoclonic-epilepsy.html
Gilsoul, M., Thierry, G., Delgado-Escueta, A.V., di Nijs, L., and Bernard, L. (2019). Subtle Brain Developmental Abnormalities in the Pathogenesis of Juvenile Myoclonic Epilepsy. Frontiers in Cellular Neuroscience, Volume 13. Doi:10.3389/fncel.2019.00433
Holmes, G. L. (2020). Drug Treatment of Progressive Myoclonic Epilepsy. Paediatric Drugs, 22(2), 149–164. https://doi-org.proxy.westernu.edu/10.1007/s40272-019-00378-y
Kara, B., Sarıkaya, C. E., Bayrak, Y. E., Güneş, A. S., Güngör, M., & Yeşil, G. (2020). Early-onset rapidly progressive myoclonic epilepsy associated with G392R likely pathogenic variant in SERPINI1. Seizure, 80, 181–182. https://doi-org.proxy.westernu.edu/10.1016/j.seizure.2020.06.022
Kiriakopoulos, E. and Osborne Shafer, P. (2019). Absence Seizures. Epilepsy Foundation. Retrieved from: https://www.epilepsy.com/learn/types-seizures/absence-seizures
Kiriakopoulos, E. and Osborne Shafer, P. (2017). Tonic-clonic Seizures. Epilepsy Foundation. Retrieved from: https://www.epilepsy.com/learn/types-seizures/tonic-clonic-seizures
Mayo Clinic (2021). Epilepsy, Symptoms and Causes. Mayo Clinic. Retrieved from: https://www.mayoclinic.org/diseases-conditions/epilepsy/symptoms-causes/syc-20350093
Mayo Clinic (2020). Myoclonus, Symptoms and Causes. Mayo Clinic. Retrieved from: https://www.mayoclinic.org/diseases-conditions/myoclonus/symptoms-causes/syc-20350459
Moawad, H. (2022). An Overview of Myoclonic Epilepsy. Very Well Health. Retrieved from: https://www.verywellhealth.com/myoclonic-epilepsy-4175105
Orsini, A., Valetto, A., Bertini, V., Esposito, M., Carli, N., Minassian, B. A., Bonuccelli, A., Peroni, D., Michelucci, R., & Striano, P. (2019). The best evidence for progressive myoclonic epilepsy: A pathway to precision therapy. Seizure, 71, 247–257. https://doi-org.proxy.westernu.edu/10.1016/j.seizure.2019.08.012
Pasquale Striano & Vincenzo Belcastro (2012). Treatment of myoclonic seizures, Expert Review of Neurotherapeutics, 12:12, 1411-1418, DOI: 10.1586/ern.12.90
Renganathan, R., & Delanty, N. (2003). Juvenile myoclonic epilepsy: under-appreciated and under-diagnosed. (Review). Postgraduate Medical Journal, 79(928), 78+. https://link.gale.com/apps/doc/A98901410/EAIM?u=sali50380&sid=bookmark-EAIM&xid=4a6b9701
Wirrell, E. (2019). Epilepsy Due to Specific Causes. Epilepsy Foundation. Retrieved from: https://www.epilepsy.com/learn/epilepsy-due-specific-causes