Myoclonus describes a symptom, not a disease. It means sudden, involuntary contraction of a muscle or group of muscles. Myoclonic twitches often cause sudden muscle contractions called positive myoclonus or muscle relaxation called negative myoclonus. Myoclonic contractions may occur singly or sequentially, in one order or irregularly, while each minute may occur rarely or many times. They can sometimes occur in response to an external event or when a person tries to move. This involuntary twitch cannot be controlled by the living person.
In its simplest form, myoclonus consists of relaxation after a muscle twitch. A hiccup is an example of this type of myoclonus. Other known examples of myoclonus are shaking or sleep onset when some people drift to sleep. These simple forms of myoclonus occur in normal, healthy people and do not cause any difficulties. More commonly, myoclonus may contain persistent, shock-like contractions in a group of muscles. In some cases, it starts in one part of the body and spreads to the muscles in other parts. In more severe cases, it may impair movement and severely limit a person’s ability to eat, talk or walk. This type of myoclonus may indicate an underlying disorder in the brain or nerves.
What are the causes of myoclonus?
Myoclonus may develop in response to infection, head or spinal cord injury, stroke, brain tumors, kidney or liver failure, lipid storage disease, chemical or drug poisoning, and other diseases. Prolonged oxygen deprivation, called hypoxia in the brain, may result in postoxic myoclonus. Myoclonus may occur on its own, but it is often one of the few symptoms associated with a wide variety of nervous system disorders. For example, people with multiple sclerosis, Parkinson’s disease, Alzheimer’s disease or Creutzfeldt-Jakob disease may develop myoclonic concussion. Myoclonic shocks are usually seen in epilepsy patients, a disorder in which electrical activity in the brain causes seizures.
What are myoclonus types?
It is difficult to classify many different forms of myoclonus because the causes, effects and reactions that cause treatment are very variable. The most common types are as follows:
• Action myoclonus: It is characterized by muscle movement triggered or intensified by voluntary movements, or even intention to act. Precise and coordinated movements can be exacerbated by trying. Action myoclonus is the most crippling form of myoclonus and may affect arms, legs, face and even sound. This type of myoclonus often causes brain damage due to the absence of oxygen and blood flow to the brain when breathing or heartbeat is temporarily stopped.
• Cortical reflex myoclonus:It is thought that the kort gray matter ”of the brain is responsible for the epilepsy in the cortex of the brain, which is responsible for most of the information processing in the outer layer or inside the brain. In this type of myoclonus, concussions usually involve only a few muscles in one part of the body, but may occur in concussions involving many muscles. Cortical reflex myoclonus may condense when individuals try to move in a certain way or when they perceive a specific sensation.
• Essential myoclonus:Epilepsy occurs in the absence of other significant abnormalities in the brain or nerves. It may occur randomly in people who do not have a family history of disease, but may appear among members of the same family, indicating that it may sometimes be an inherited disease. Essential myoclonus tends to be stable without increasing severity over time. In some families, essential myoclonus occurs with a form of dystonia called essential tremor and even myoclonus dystonia. Another form of essential myoclonus may be a form of epilepsy without a known cause.
• Palatal myoclonus:It is a regular, rhythmic contraction of one or both sides of the back of the mouth roof called soft palate. These contractions may be accompanied by myoclonus in other muscles, including the face, tongue, throat and diaphragm. Contractions are very fast, occur as often as 150 times per minute, and can remain during sleep. This is usually seen in adults and may persist indefinitely. Some people with palatal myoclonus see this as a minor problem, while others sometimes complain of a sound like a click in the ear, muscles in the soft palate connection. The disease can cause discomfort and severe pain in some people.
Progressive myoclonus epilepsy (PME):Myoclonus is a group of diseases characterized by other serious symptoms such as epileptic seizures, difficulty walking or speaking. These rare disorders often worsen over time and can sometimes be fatal. Studies have identified many forms of PME. Lafora body disease is an inherited disease as an autosomal recessive disease. This occurs when children with the disease inherit two copies of a defective gene, one from each parent. Lafora is characterized by body disease, myoclonus, epileptic seizures and dementia (increased memory loss and other intellectual functions). The second group of PME diseases of the cerebral storage diseases class is usually myoclonus, visual problems, dementia and dystonia (continuous muscle contractions that cause bending movements or abnormal postures). Another group of PME disorders in the system degeneration class is often accompanied by action myoclonus, seizures balance and gait problems. Most of these PME diseases begin in childhood or adolescence.
Reticular reflex myoclonus: It is thought to be a type of generalized epilepsy that controls vital functions from the brain stem to the spinal cord, breathing and heartbeat. Myoclonic concussions usually affect the entire body, while muscles on both sides of the body are affected simultaneously. In some people, myoclonic occurs only in one part of the body, such as legs, and all muscles in this part develop concussion. Reticular reflex myoclonus can be triggered by voluntary movement or by an external stimulus.
• Stimulus-sensitive myoclonus: It can be triggered by a variety of external events, such as noise, movement and light. Sudden events can increase an individual’s sensitivity.
• Sleep myoclonus:It occurs in the early stages of sleep, especially at the time of falling asleep, and some forms are sensitive to the stimulus. Some people whose myoclonus is about to sleep are rarely seen to be uncomfortable or need treatment for this condition. However, it may be a symptom in more complex and disturbing sleep disorders such as restless leg syndrome and may require treatment by doctors.
Although rare cases of myoclonus originate from injury to the peripheral nerves (defined as nerves outside the brain and spinal cord or nerves outside the central nervous system), most myoclonus is caused by disruption of the central nervous system. Research shows that many places in the brain are involved in myoclonus. For example, such a condition is in the brainstem close to the sections responsible for the response to confusion, which is an automatic reaction to an unexpected stimulus involving rapid muscle contraction.
The specific mechanisms underlying myoclonus have not yet been fully understood. Scientists believe that some types of myoclonus sensitive to stimulants may include excessive excitability of parts of the brain that control movement. These parts are interconnected by a series of feedback loops called the motor path. These pathways facilitate and alter communication between the brain and muscles. The main elements of this communication are chemicals known as neurotransmitters that carry messages from one nerve cell or neuron to another. Neurotransmitters are released by neurons and bind themselves to receptors in portions of neighboring cells. Some neurotransmitters may make the host cell more sensitive, while others tend to make the host cell less sensitive. Laboratory studies,
Some researchers claim that abnormalities or deficiencies in the receptor for certain neurotransmitters may contribute to some forms of myoclonus. Myoclonus-related receptors include serotonin and gamma-aminobutyric acid (GABA) for two important inhibitory neurotransmitters. Other receptors that bind to the myoclonus include those for opiates and glycine, an inhibitory neurotransmitter important for controlling motor and sensory functions in the spinal cord. Further research is needed to determine why these receptor abnormalities contribute to myoclonus.
How is myoclonus treated?
Myoclonus therapy focuses on drugs that can help reduce symptoms. In particular, the first preferred drug for treating a particular type of effect myoclonus is clonazepam, a type of sedative. The dose of clonazepam is generally increased gradually until it is individually healed or the side effects become detrimental. Common side effects of the drug are drowsiness and loss of coordination. If the individual develops immunity to the drug, the beneficial effects of clonazepam may decrease over time.
Many of the drugs used for myoclonus, such as barbiturates, levetiracetam, phenytoin and primidone, are also used to treat epilepsy. Barbiturates slow down the central nervous system and cause sedative or antiseizing effects. Phenytoin, levetiracetam and primidone are effective antiepileptic drugs, but phenytoin may cause liver failure or may have other long-term adverse effects in people with PME. Sodium valproate is an alternative therapy for myoclonus and can be used alone or in combination with clonazepam. Although clonazepam or sodium valproate is effective in most people with myoclonus, some people may react with these drugs.
Some studies have shown that doses of 5-hydroxytryptophan (5-HTP), a building block of serotonin, lead to improvement in individuals with myoclonus and PME, which are effective in some species. However, other studies have shown that 5-HTP treatment is not effective in all people with myoclonus and may actually worsen the condition in some people. These differences in the effect of 5-HTP on individuals with myoclonus have not yet been explained, but they may provide important clues for underlying abnormalities in serotonin receptors.
The complex origins of myoclonus may require the use of multiple drugs for effective treatment. Although some drugs have a limited effect when used separately, they may have a greater effect when used in combination with drugs acting on different pathways or mechanisms in the brain. By combining several of these drugs, scientists hope to better control the control of myoclonic symptoms. Some drugs currently being studied in different combinations include clonazepam, sodium valproate, levetiracetam and primidone. Hormonal therapy may also increase the response to antimiconic drugs in some individuals.