Myoclonic epilepsy

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Myoclonic epilepsy
Specialty Neurology

Myoclonic epilepsy refers to a family of epilepsies that present with myoclonus. When myoclonic jerks are occasionally associated with abnormal brain wave activity, it can be categorized as myoclonic seizure. If the abnormal brain wave activity is persistent and results from ongoing seizures, then a diagnosis of myoclonic epilepsy may be considered. [1]

Contents

Familial adult myoclonus Epilepsy (FAME) This is a condition characterized by the repetition of non-coding sequences and has been identified using various abbreviations. Initially, it was associated with four primary gene locations: FAME1 (8q23.3–q24.1), FAME2 (2p11.1–q12.1), FAME3 (5p15.31–p15.1), and FAME4 (3q26.32–3q28). Currently, it is understood that the genetic mechanism behind FAME involves the elongation of similar non-coding sequences, specifically pentanucleotide repeats, namely TTTCA and TTTTA, within different genes. [2]

Signs and symptoms

Myoclonus can be described as brief jerks of the body; [3] it can involve any part of the body, but it is mostly seen in limbs or facial muscles. The jerks are usually involuntary and can lead to falls. EEG is used to read brain wave activity. Spike activity produced from the brain is usually correlated with brief jerks seen on EMG or excessive muscle artifact. They usually occur without detectable loss of consciousness and may be generalized, regional or focal on the EEG tracing. Myoclonus jerks can be epileptic or not epileptic. Epileptic myoclonus is an elementary electroclinical manifestation of epilepsy involving descending neurons, whose spatial (spread) or temporal (self-sustained repetition) amplification can trigger overt epileptic activity. [3]

Diagnosis

There are two syndromes and several related disorders.

Juvenile

Juvenile myoclonic epilepsy is responsible for 7% of cases of epilepsy. [4] Seizures usually begin around puberty and usually have a genetic basis. [4] Seizures can be stimulus-selective, with flashing lights being one of the most common triggers. [4]

Juvenile myoclonic epilepsy (JME) is a prevalent and typical form of idiopathic generalized epilepsy (IGE) syndrome. However, establishing a precise definition for JME has posed difficulties, making it equally challenging to establish clear indicators for predicting its course and results. None of the existing systems for classifying epilepsy prioritize forecasting or final results. [5]

Progressive

Progressive myoclonus epilepsy is a disease associated with myoclonus, epileptic seizures, and other problems with walking or speaking. These symptoms often worsen over time and can be fatal. [6]

MERRF syndrome is also known as myoclonic epilepsy with ragged-red fibers. This rare inherited disorder affects muscles cells. [7] Features of MERRF, along with myoclonus epilepsy seizures, include ataxia, peripheral neuropathy, and dementia. [7]

Lafora disease is also known as Lafora progressive myoclonus epilepsy, which is an autosomal recessive inherited disorder involving recurrent seizures and degradation of mental capabilities. [8] Lafora disease usually occurs in late childhood and usually leads to death around 10 years after first signs of the disease. [8]

Unverricht-Lundborg disease is an autosomal recessive inherited disorder seen in individuals as young as six years. [9] It is associated with possible loss of consciousness, rigidity, ataxia, dysarthria, declination of mental functioning, and involuntary shaking. [9]

Neuronal ceroid lipofuscinosis is a group of diseases that cause blindness, loss of mental abilities, and loss of movement. [10] All diseases in this group are lysosomal-storage disorders that also lead to death roughly ten years after onset of the disease. [10]

Lennox–Gastaut syndrome is often associated with intellectual deficits as well as a lack of response to anti-epileptic drugs. [11] It usually begins in the first years of life. [11]

Reticular reflex myoclonus is a generalized form of epilepsy originating from the brain stem. Jerks associated with the disorder can affect all muscles on the body or be selective in certain areas. [6] Jerks can be triggered by voluntary movement or be stimulus-selective. [6]

Differential diagnosis

In clinical practice, it's important to differentiate FAME from other tremor-related conditions like essential tremor. Early on, patients without significant myoclonus or seizures might be misdiagnosed and receive incorrect treatment. Factors like unresponsiveness to beta-blockers and absence of certain tremors can help with the diagnosis. Consider progressive myoclonic epilepsy (PME) and juvenile myoclonic epilepsy (JME) as primary differential diagnoses due to their dominant seizures and age of onset. While FAME is milder than PMEs, it shows gradual cognitive decline and worsening tremors/myoclonus. Some cases initially labeled as JME worsen unexpectedly. Lack of cortical reflex myoclonus findings and distinct myoclonus in early JME stages are important clues. [12]

Related Research Articles

Lafora disease is a rare, adult-onset and autosomal recessive genetic disorder which results in myoclonus epilepsy and usually results in death several years after the onset of symptoms. The disease is characterized by the accumulation of inclusion bodies, known as Lafora bodies, within the cytoplasm of the cells in the heart, liver, muscle, and skin. Lafora disease is also a neurodegenerative disease that causes impairment in the development of brain (cerebral) cortical neurons and is a glycogen metabolism disorder.

A hypnic jerk, hypnagogic jerk, sleep start, sleep twitch, myoclonic jerk, or night start is a brief and sudden involuntary contraction of the muscles of the body which occurs when a person is beginning to fall asleep, often causing the person to jump and awaken suddenly for a moment. Hypnic jerks are one form of involuntary muscle twitches called myoclonus.

Absence seizures are one of several kinds of generalized seizures. In the past, absence epilepsy was referred to as "pyknolepsy," a term derived from the Greek word "pyknos," signifying "extremely frequent" or "grouped".These seizures are sometimes referred to as petit mal seizures ; however, usage of this terminology is no longer recommended. Absence seizures are characterized by a brief loss and return of consciousness, generally not followed by a period of lethargy. Absence seizures are most common in children. They affect both sides of the brain.

<span class="mw-page-title-main">Myoclonus</span> Involuntary, irregular muscle twitch

Myoclonus is a brief, involuntary, irregular twitching of a muscle, a joint, or a group of muscles, different from clonus, which is rhythmic or regular. Myoclonus describes a medical sign and, generally, is not a diagnosis of a disease. These myoclonic twitches, jerks, or seizures are usually caused by sudden muscle contractions or brief lapses of contraction. The most common circumstance under which they occur is while falling asleep. Myoclonic jerks occur in healthy people and are experienced occasionally by everyone. However, when they appear with more persistence and become more widespread they can be a sign of various neurological disorders. Hiccups are a kind of myoclonic jerk specifically affecting the diaphragm. When a spasm is caused by another person it is known as a provoked spasm. Shuddering attacks in babies fall in this category.

<span class="mw-page-title-main">Neuronal ceroid lipofuscinosis</span> Medical condition

Neuronal ceroid lipofuscinosis is the general name for a family of at least eight genetically separate neurodegenerative lysosomal storage diseases that result from excessive accumulation of lipopigments (lipofuscin) in the body's tissues. These lipopigments are made up of fats and proteins. Their name comes from the word stem "lipo-", which is a variation on lipid, and from the term "pigment", used because the substances take on a greenish-yellow color when viewed under an ultraviolet light microscope. These lipofuscin materials build up in neuronal cells and many organs, including the liver, spleen, myocardium, and kidneys.

<span class="mw-page-title-main">MERRF syndrome</span> Medical condition

MERRF syndrome is a mitochondrial disease. It is extremely rare, and has varying degrees of expressivity owing to heteroplasmy. MERRF syndrome affects different parts of the body, particularly the muscles and nervous system. The signs and symptoms of this disorder appear at an early age, generally childhood or adolescence. The causes of MERRF syndrome are difficult to determine, but because it is a mitochondrial disorder, it can be caused by the mutation of nuclear DNA or mitochondrial DNA. The classification of this disease varies from patient to patient, since many individuals do not fall into one specific disease category. The primary features displayed on a person with MERRF include myoclonus, seizures, cerebellar ataxia, myopathy, and ragged red fibers (RRF) on muscle biopsy, leading to the disease's name. Secondary features include dementia, optic atrophy, bilateral deafness, peripheral neuropathy, spasticity, or multiple lipomata. Mitochondrial disorders, including MERRFS, may present at any age.

Idiopathic generalized epilepsy (IGE) is a group of epileptic disorders that are believed to have a strong underlying genetic basis. IGE is considered a subgroup of Genetic Generalized Epilepsy (GGE). Patients with an IGE subtype are typically otherwise normal and have no structural brain abnormalities. People also often have a family history of epilepsy and seem to have a genetically predisposed risk of seizures. IGE tends to manifest itself between early childhood and adolescence although it can be eventually diagnosed later. The genetic cause of some IGE types is known, though inheritance does not always follow a simple monogenic mechanism.

Juvenile myoclonic epilepsy (JME), also known as Janz syndrome or impulsive petit mal, is a form of hereditary, idiopathic generalized epilepsy, representing 5–10% of all epilepsy cases. Typically it first presents between the ages of 12 and 18 with myoclonic seizures. These events typically occur after awakening from sleep, during the evening or when sleep-deprived. JME is also characterized by generalized tonic–clonic seizures, and a minority of patients have absence seizures. It was first described by Théodore Herpin in 1857. Understanding of the genetics of JME has been rapidly evolving since the 1990s, and over 20 chromosomal loci and multiple genes have been identified. Given the genetic and clinical heterogeneity of JME some authors have suggested that it should be thought of as a spectrum disorder.

Unverricht–Lundborg disease is the most common form of an uncommon group of genetic epilepsy disorders called the progressive myoclonus epilepsies. It is caused due to a mutation in the cystatin B gene (CSTB). The disease is named after Heinrich Unverricht, who first described it in 1891, and Herman Bernhard Lundborg, who researched it in greater detail in 1901 and 1903. ULD onsets in children between the ages of 6 and 16; there are no known cases in which the person was older than 18. Most cases originate from the Baltic region of Europe, though many have been reported from countries in the Mediterranean.

Progressive Myoclonic Epilepsies (PME) are a rare group of inherited neurodegenerative diseases characterized by myoclonus, resistance to treatment, and neurological deterioration. The cause of PME depends largely on the type of PME. Most PMEs are caused by autosomal dominant or recessive and mitochondrial mutations. The location of the mutation also affects the inheritance and treatment of PME. Diagnosing PME is difficult due to their genetic heterogeneity and the lack of a genetic mutation identified in some patients. The prognosis depends largely on the worsening symptoms and failure to respond to treatment. There is no current cure for PME and treatment focuses on managing myoclonus and seizures through antiepileptic medication (AED).

Ramsay Hunt syndrome type 1 is a rare, degenerative, neurological disorder characterized by myoclonus epilepsy, intention tremor, progressive ataxia and occasionally cognitive impairment

Ohtahara syndrome (OS), also known as early infantile epileptic encephalopathy (EIEE) is a progressive epileptic encephalopathy. The syndrome is outwardly characterized by tonic spasms and partial seizures within the first few months of life, and receives its more elaborate name from the pattern of burst activity on an electroencephalogram (EEG). It is an extremely debilitating progressive neurological disorder, involving intractable seizures and severe intellectual disabilities. No single cause has been identified, although in many cases structural brain damage is present.

<span class="mw-page-title-main">Dentatorubral–pallidoluysian atrophy</span> Congenital disorder of nervous system

Dentatorubral–pallidoluysian atrophy (DRPLA) is an autosomal dominant spinocerebellar degeneration caused by an expansion of a CAG repeat encoding a polyglutamine tract in the atrophin-1 protein. It is also known as Haw River Syndrome and Naito–Oyanagi disease. Although this condition was perhaps first described by Smith et al. in 1958, and several sporadic cases have been reported from Western countries, this disorder seems to be very rare except in Japan.

Mitochondrially encoded tRNA phenylalanine also known as MT-TF is a transfer RNA which in humans is encoded by the mitochondrial MT-TF gene.

Mitochondrially encoded tRNA lysine also known as MT-TK is a transfer RNA which in humans is encoded by the mitochondrial MT-TK gene.

People with epilepsy may be classified into different syndromes based on specific clinical features. These features include the age at which seizures begin, the seizure types, and EEG findings, among others. Identifying an epilepsy syndrome is useful as it helps determine the underlying causes as well as deciding what anti-seizure medication should be tried. Epilepsy syndromes are more commonly diagnosed in infants and children. Some examples of epilepsy syndromes include benign rolandic epilepsy, childhood absence epilepsy and juvenile myoclonic epilepsy. Severe syndromes with diffuse brain dysfunction caused, at least partly, by some aspect of epilepsy, are also referred to as epileptic encephalopathies. These are associated with frequent seizures that are resistant to treatment and severe cognitive dysfunction, for instance Lennox-Gastaut syndrome and West syndrome.

Kufs disease is one of many diseases categorized under a disorder known as neuronal ceroid lipofuscinosis (NCLs) or Batten disease. NCLs are broadly described to create problems with vision, movement and cognitive function. Among all NCLs diseases, Kufs is the only one that does not affect vision, and although this is a distinguishing factor of Kufs, NCLs are typically differentiated by the age at which they appear in a patient

A neonatal seizure is a seizure in a baby younger than age 4-weeks that is identifiable by an electrical recording of the brain. It is an occurrence of abnormal, paroxysmal, and persistent ictal rhythm with an amplitude of 2 microvolts in the electroencephalogram,. These may be manifested in form of stiffening or jerking of limbs or trunk. Sometimes random eye movements, cycling movements of legs, tonic eyeball movements, and lip-smacking movements may be observed. Alteration in heart rate, blood pressure, respiration, salivation, pupillary dilation, and other associated paroxysmal changes in the autonomic nervous system of infants may be caused due to these seizures. Often these changes are observed along with the observance of other clinical symptoms. A neonatal seizure may or may not be epileptic. Some of them may be provoked. Most neonatal seizures are due to secondary causes. With hypoxic ischemic encephalopathy being the most common cause in full term infants and intraventricular hemorrhage as the most common cause in preterm infants.

PRICKLE1-related progressive myoclonus epilepsy with ataxia is a very rare genetic disorder which is characterized by myoclonic epilepsy and ataxia.

References

  1. ↑ Holmes, Gregory L. (April 2020). "Drug Treatment of Progressive Myoclonic Epilepsy". Pediatric Drugs. 22 (2): 149–164. doi:10.1007/s40272-019-00378-y. PMC   7901803 . PMID   31939107.
  2. ↑ Cuccurullo, Claudia; Striano, Pasquale; Coppola, Antonietta (January 2023). "Familial Adult Myoclonus Epilepsy: A Non-Coding Repeat Expansion Disorder of Cerebellar–Thalamic–Cortical Loop". Cells. 12 (12): 1617. doi: 10.3390/cells12121617 . PMC   10297251 . PMID   37371086. Creative Commons by small.svg  This article incorporates textfrom this source, which is available under the CC BY 4.0 license.
  3. 1 2 Wyllie, Elaine (2006). The Treatment of Epilepsy. Lippincott, Williams and Wilkins. ISBN   0-7817-4995-6.
  4. 1 2 3 Murthy, J.M.K.; Rao, Ch.Mohan; Meena, A.K. (February 1998). "Clinical observations of juvenile myoclonic epilepsy in 131 patients: A study in South India". Seizure. 7 (1): 43–47. doi: 10.1016/s1059-1311(98)90007-3 . PMID   9548225. S2CID   17459518.
  5. ↑ Rubboli, Guido; et al. (2 May 2023). "Variation in prognosis and treatment outcome in juvenile myoclonic epilepsy: a Biology of Juvenile Myoclonic Epilepsy Consortium proposal for a practical definition and stratified medicine classifications". Brain Communications. 5 (3): fcad182. doi:10.1093/braincomms/fcad182. PMC   10288558 . PMID   37361715.
  6. 1 2 3 Myoclonus Fact Sheet. National Institute of Neurological Disorders and Stroke.
  7. 1 2 "Myoclonic epilepsy with ragged-red fibers". Genetics Home Reference.
  8. 1 2 "Lafora progressive myoclonus epilepsy". Genetics Home Reference.
  9. 1 2 "Unverricht-Lundborg disease". Genetics Home Reference.
  10. 1 2 Mole, S. E.; Williams, R. E.; Adam, M. P.; Mirzaa, G. M.; Pagon, R. A.; Wallace, S. E.; Bean LJH; Gripp, K. W.; Amemiya, A. (1993). "Neuronal Ceroid-Lipofuscinoses – RETIRED CHAPTER, FOR HISTORICAL REFERENCE ONLY". Neuronal Ceroid-Lipofuscinoses. GeneReviews. PMID   20301601.
  11. 1 2 Niedermeyer, E. (March 1992). "Ellen R. Grass Guest Lecture: Epileptic Syndromes: A Remarkable Contribution of EEG to Epileptology". American Journal of EEG Technology. 32 (1): 3–25. doi:10.1080/00029238.1992.11080389.
  12. ↑ Altiokka Uzun, GüNeş; Baykan, BetüL (2023). "Familial Adult Myoclonic Epilepsy: Clinical and Genetic Approach to an Under-recognized Disease". Archives of Neuropsychiatry. 60 (2): 174–177. doi:10.29399/npa.28252. PMC   10242282 . PMID   37287551.
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