Myoclonus is a brief, involuntary, irregular twitching of a muscle or a group of muscles, different from clonus, which is rhythmic or regular.
Myoclonus is a medical sign.
Myoclonic twitches, jerks, or seizures are usually caused by sudden muscle contractions, positive myoclonus, or brief lapses of contraction, negative myoclonus.
A myoclonic seizure is a sudden involuntary contraction of muscle groups.
The feeling is described as uncontrollable jolts common to receiving a mild electric shock.
Myoclonus occurs most commonly when falling asleep.
Myoclonic jerks occur in healthy people.
Myoclonus is experienced occasionally by everyone.
When myoclonus appears persistently and become more widespread they can be a sign of various neurological disorders.
Most myoclonus is caused by a disturbance of the central nervous system.
Some are from peripheral nervous system injuries, suggesting several locations in the brain are involved in myoclonus.
Myoclonic jerks commonly occur in individuals with epilepsy.
Hiccups are a kind of myoclonic jerk affecting the diaphragm.
Myoclonic jerks may occur alone or in sequence, and with or without a pattern.
Myoclonic jerks may occur infrequently or many times each minute.
Most often, myoclonus is one of several signs in a wide variety of nervous system disorders: multiple sclerosis, Parkinson’s disease, dystonia, Alzheimer’s disease, Gaucher’s disease, subacute sclerosing panencephalitis, Creutzfeldt–Jakob disease (CJD), serotonin toxicity, some cases of Huntington’s disease, some forms of epilepsy, and occasionally in intracranial hypotension.
In almost all instances of myoclonus caused by central nervous system disease it is preceded by other symptoms.
Lesions of the cortex, subcortex or spinal cord may be the site of origin of myoclonus.
The most common types of myoclonus:
action, cortical reflex, essential, palatal, those seen in the progressive myoclonus epilepsies, reticular reflex, sleep and stimulus-sensitive.
Cortical reflex myoclonus epilepsy originates in the cerebral cortex, which is responsible for much of the information processing that takes place in the brain.
Cortical reflex myoclonus epilepsy jerks usually involve only a few muscles in one part of the body, but jerks involving many muscles may occur.
Cortical reflex myoclonus can be intensified when moving in a certain way or perceive a particular sensation.
Essential myoclonus occurs in the absence of epilepsy or other apparent abnormalities in the brain or nerves.
Essential myoclonus can occur randomly in people with no family history, or among members of the same family.
Essential myoclonus is associated with sometimes an inherited disorder.
Essential myoclonus is a mostly stable process, without increasing in severity over time.
Essential myoclonus may be a type of epilepsy.
Juvenile myoclonic epilepsy (JME) usually consists of jerking and muscle twitches of the upper extremities: arms, shoulders, elbows, and very rarely, the legs.
JME is among the most common types of epilepsy.
JME can affect one of every 14 people with the disease.
JME seizures typically occur shortly after waking up.
Onset for JME occurs around puberty for most patients.
Lennox-Gastaut syndrome (LGS), or childhood epileptic encephalopathy, is a rare epileptic disorder accounting for 1–4% of childhood epilepsies:
multiple seizures daily, learning disabilities, abnormal findings in electroencephalogram (EEG).
Earlier age of seizure onset is correlated with higher risk of cognitive impairment.
Progressive myoclonus epilepsy (PME) is diseases characterized by myoclonus, epileptic seizures, tonic-clonic seizures, and other serious symptoms such as trouble walking or speaking.
Progressive myoclonus epilepsy (PME)
disorders often get worse over time and can be fatal.
There are at least three forms of PME.
Lafora disease is inherited as an autosomal recessive disorder.
Lafora disease is characterized by myoclonus, epileptic seizures, and dementia.
PME diseases belonging to the class of cerebral storage diseases usually involves myoclonus, visual problems, dementia, and dystonia.
A third group of PME disorders in the class of system degenerations often is accompanied by action myoclonus, seizures, and problems with balance and walking.
Many PME diseases begin in childhood or adolescence.
Treatment is not normally successful.
Reticular reflex myoclonus is a type of generalized epilepsy that originates in the brainstem.
Reticular reflex myoclonus can be triggered by either a voluntary movement or an external stimulus.
Myoclonic jerks usually affect the whole body.
Muscles on both sides of the body are affected simultaneously.
In some cases myoclonic jerks occur in only a part of the body, such as the legs, with all the muscles in that part being involved in each jerk.
Diaphragmatic flutter is characterized by a spoken communication that sounds like a short-breathed hiccup.
The rate of diaphragmatic contraction ranges between 35 and 480 contractions per minute, with the average rate found to be 150.
These muscle spasms can recur dozens of times per day.
Possible causes of diaphragmatic flutter include disruptions within the central or peripheral nervous systems, anxiety, nutritional disorder, and certain pharmaceuticals.
No single treatment has proven effective, though blocking or crushing of the phrenic nerve can provide instantaneous relief when pharmacologic treatment has proven ineffective.
Reported in about 50 people in the world.
Action myoclonus is characterized by muscular jerking triggered or intensified by voluntary movement or even the intention to move.
Action myoclonus is exacerbated by
by attempts at precise, coordinated movements.
Action myoclonus is the most disabling form of myoclonus.
Action myoclonus can affect the arms, legs, face, and even the voice.
Action myoclonus is often associated with tonic-clonic seizures and diffuse neuronal disease such as post-hypoxic encephalopathy, uremia, and the various forms of progressive myoclonus epilepsy.
In the presence of focal cerebral damage from a lack of oxygen and blood flow to the brain when breathing or heartbeat is temporarily stopped , action myoclonus disease may be restricted to one limb.
Over-excitement of the sensorimotor cortex the reticular formation is also a cause of action myoclonus: Serotonin and GABA neurotransmitters are thought to cause a lack of inhibition.
Systems involved in myoclonus include the cerebellodentatorubral, pyramidal, extrapyramidal, optic, auditory, posterior columns and gracile and cuneate nuclei, spinocerebellar tracts, motor neurons of cranial nerves and anterior horns, and muscle fibers.
Palatal myoclonus is a regular, rhythmic contraction of one or both sides of the soft palate.
Palatal myoclonus contractions may be accompanied by myoclonus in other muscles: face, tongue, throat, and diaphragm.
Palatal myoclonus contractions are very rapid, occurring as often as 150 times a minute.
Palatal myoclonus may persist during sleep.
Palatal myoclonus usually appears in adults and can last indefinitely.
It is usually regarded as a minor problem.
Some patients with palatal myoclonus complain of an occasional clicking sound, a noise made as the soft palate muscles contract.
Middle ear myoclonus occurs in the muscles of the middle ear: tensor tympani and stapedius muscles, or can involve the muscles surrounding the Eustachian tube: tensor veli palatini, levator veli palatini, and salpingopharyngeus.
Middle ear myoclonus is appreciated as a thumping sound or sensation in the ear.
Spinal myoclonus originates in the spinal cord, and includes segmental and propriospinal myoclonus.
Propriospinal myoclonus is usually due to a thoracic generator producing truncal flexion jerk.
Stimulus-sensitive myoclonus is triggered by a variety of external events, including noise, movement, and light.
Sleep myoclonus occurs during the initial phases of sleep, especially at the moment of dropping off to sleep.
Sleep myoclonus is associated with sleep disorders, such as restless legs syndrome.
Myoclonus can be associated with patients with Tourette syndrome.
The muscle jerks consist of symmetric, mostly generalized jerks.
They may be localized to the arms and shoulders and also simultaneously with a head nod.
Sometimes the entire body may jerk.
Because the event is so brief the person appears to remain fully conscious; but as is the case with all generalized seizures, the patient is not conscious.
Myoclonic reflex seizures can be brought on by flashing lights or other environmental triggers.
Common myoclonus experienced include hiccups and hypnic jerks that some people experience while drifting off to sleep.
Severe cases of pathologic myoclonus impair movements and severely limit a person’s ability to sleep, eat, talk, and walk.
Myoclonus in healthy person may indicate an arbitrary muscle contraction.
Myoclonus may also develop in response to: infection, hyperosmolar hyperglycemic state, head or spinal cord injury, stroke, stress, brain tumors, kidney or liver failure, lipid storage disease, chemical or drug poisoning, and drug side effects; tramadol, quinolones, benzodiazepine, gabapentin, sertraline, lamotrigine, opioids.
Benign myoclonic movements are commonly seen during the induction of general anesthesia: suspected to be the result from decreased inhibitory signaling from cranial neurons.
Prolonged oxygen deprivation to the brain, may result in posthypoxic myoclonus.
People suffering from benign fasciculation syndrome can often experience myoclonic jerking of limbs, fingers and thumbs.
While myoclonus can occur by itself, it most often is one of several symptoms associated with a variety of nervous system disorders, including multiple sclerosis, Parkinson’s disease, Alzheimer’s disease, opsoclonus myoclonus, Creutzfeldt–Jakob disease, Lyme disease and lupus.
It is found in MERRF (Myoclonic Epilepsy with Ragged Red Fibers), a rare mitochondrial encephalomyopathy.
Jerks of muscle groups, is sometimes seen in ambulatory patients being treated with high doses of morphine, hydromorphone, and similar drugs.
The jerks could be a sign of high and/or rapidly increasing serum levels of these drugs.
Myoclonic jerks caused by other opioids, such as tramadol that may be less intense.
Anticholinergics, are known to cause myoclonic jerks.
Some types of stimulus-sensitive myoclonus may involve overexcitability of the parts of the brain that control movement.
These parts of the CNS are interconnected in a series of feedback loops called motor pathways, which
facilitate and regulate communication between the brain and muscles.
Neurotransmitters, which carry messages from one nerve cell, to another.
An imbalance between these neurotransmitters may underlie myoclonus.
Receptors associated with myoclonus include two important inhibitory neurotransmitters: serotonin, which constricts blood vessels and brings on sleep, and gamma-aminobutyric acid (GABA), which helps the brain maintain muscle control.
Receptors with links to myoclonus include those for benzodiazepines, and for glycine, an inhibitory neurotransmitter that is important for the control of motor and sensory functions in the spinal cord.
TREATMENT
Myoclonus may be treated with multiple drugs, which have a limited effect individually, but greater when combined with others that act on different brain pathways or mechanisms: combinations include clonazepam, sodium valproate, piracetam, and primidone.
Treatment is most effective when the underlying cause is known, and specific treated can be applied.
Hormonal therapy may improve responses to antimyoclonic drugs in some people.
5-hydroxytryptophan (5-HTP) leads to improvement in patients with some types of action myoclonus and PME.
Many of the drugs used for myoclonus are also used to treat epilepsy:
Barbiturates slow down the central nervous system and cause tranquilizing or antiseizure effects.
Phenytoin and primidone are effective antiepileptics drugs.
Sodium valproate is an alternative therapy for myoclonus and can be used either alone or in combination with clonazepam.
Discontinuation of drugs suspected of causing myoclonus and treatment of metabolic derangements may resolve some cases of myoclonus.
In forms of myoclonus where only a single area is affected, Botox injections may be helpful: The chemical messenger responsible for triggering the involuntary muscle contractions is blocked by the Botulinum toxins.
Surgery is an option for treatment if the symptoms are caused by a tumor or lesion in the brain or spinal cord.
In severe cases of myoclonus, with underlying disorder in the brain or nerves, movement can be extremely distorted and limit ability to normally function, such as in eating, talking, and walking.
Treatments that are usually effective, such as clonazepam and sodium valproate, may cause adverse reactions to these drug, including increased tolerance and a greater need for increase in dosage.
The prognosis for more simple forms of myoclonus there may be few to no difficulties.