myoclonus myoclonus myoclonus is a brief, involuntary, irregular (lacking rhythm) twitching of a muscle, a joint, or a group of muscles, different from clonus, which is rhythmic or regular. myoclonus (myo "muscle", clonic "jerk") 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 (positive myoclonus) or brief lapses of contraction (negative myoclonus). the most common circumstance under which they occur is while falling asleep (hypnic jerk). 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. myoclonusa person with a myoclonus following a peripheral nerve blockspecialtyneurology myoclonic jerks may occur alone or in sequence, in a pattern or without pattern. they may occur infrequently or many times each minute. most often, myoclonus is one of several signs in a wide variety of nervous system disorders such as multiple sclerosis, parkinson's disease, dystonia, cerebral palsy, 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 in which myoclonus is caused by central nervous system disease it is preceded by other symptoms; for instance, in cjd it is generally a late-stage clinical feature that appears after the patient has already started to exhibit gross neurological deficits. anatomically, myoclonus may originate from lesions of the cortex, subcortex or spinal cord. the presence of myoclonus above the foramen magnum effectively excludes spinal myoclonus; further localisation relies on further investigation with electromyography (emg) and electroencephalography (eeg). types the most common types of myoclonus include action, cortical reflex, essential, palatal, those seen in the progressive myoclonus epilepsies, reticular reflex, sleep and stimulus-sensitive. epilepsy forms cortical reflex myoclonus is thought to be a type of epilepsy that originates in the cerebral cortex – the outer layer, or "gray matter", of the brain, responsible for much of the information processing that takes place in the brain. in this type of myoclonus, 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 patients attempt to move 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. it can occur randomly in people with no family history, or among members of the same family, indicating that it sometimes may be an inherited disorder. essential myoclonus tends to be stable without increasing in severity over time. some scientists speculate that some forms of essential myoclonus may be a type of epilepsy with no known cause. juvenile myoclonic epilepsy (jme) usually consists of jerking and muscle twitches of the upper extremities. this may include the arms, shoulders, elbows, and very rarely, the legs. jme is among the most common types of epilepsy and can affect one of every 14 people with the disease. these seizures typically occur shortly after waking up. onset for jme can be seen around puberty for most patients. administration of medications that also treat multiple seizure types is usually the most effective form of treatment. lennox-gastaut syndrome (lgs), or childhood epileptic encephalopathy, is a rare epileptic disorder accounting for 1–4% of childhood epilepsies. the syndrome has much more severe symptoms ranging from multiple seizures daily, learning disabilities, and abnormal findings in electroencephalograms (eeg). earlier age of seizure onset is correlated with a higher risk of cognitive impairment. progressive myoclonus epilepsy (pme) is a group of diseases characterized by myoclonus, epileptic seizures, tonic-clonic seizures, and other serious symptoms such as trouble walking or speaking. these rare disorders often get worse over time and can be fatal. studies have identified at least three forms of pme. lafora disease is inherited as an autosomal recessive disorder, meaning that the disease occurs only when a child inherits two copies of a defective gene, one from each parent. lafora disease is characterized by myoclonus, epileptic seizures, and dementia (progressive loss of memory and other intellectual functions). a second group of pme diseases belonging to the class of cerebral storage diseases usually involves myoclonus, visual problems, dementia, and dystonia (sustained muscle contractions that cause twisting movements or abnormal postures). another group of pme disorders in the class of system degenerations often is accompanied by action myoclonus, seizures, and problems with balance and walking. many of these pme diseases begin in childhood or adolescence. treatment is not normally successful for any extended period of time. reticular reflex myoclonus is thought to be a type of generalized epilepsy that originates in the brainstem, the part of the brain that connects to the spinal cord and controls vital functions such as breathing and heartbeat. myoclonic jerks usually affect the whole body, with muscles on both sides of the body affected simultaneously. in some people, 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. reticular reflex myoclonus can be triggered by either a voluntary movement or an external stimulus. diaphragmatic flutter a very rare form includes the diaphragmatic flutter, the belly dancer's syndrome,: 2 or van leeuwenhoek's disease. it was first described by antonie van leeuwenhoek in 1723, who had it.: 2 the condition characterizes spoken communication that sounds like a short-breathed hiccup. these muscle spasms can recur dozens of times per day. rate of diaphragmatic contraction ranges between 35 and 480 contractions per minute, with the average rate found to be 150.: 3 studies show that possible causes 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.: 11 only about 50 people in the world have been diagnosed with diaphragmatic flutter. other forms action myoclonus is characterized by muscular jerking triggered or intensified by voluntary movement or even the intention to move. it may be made worse by attempts at precise, coordinated movements. action myoclonus is the most disabling form of myoclonus and can affect the arms, legs, face, and even the voice. it is often associated with tonic-clonic seizures and diffuse neuronal disease such as post-hypoxic encephalopathy, uremia, and the various forms of pme, although, in the case of focal cerebral damage, the disease may be restricted to one limb. this type of myoclonus often is caused by brain damage that results from a lack of oxygen and blood flow to the brain when breathing or heartbeat is temporarily stopped. over-excitement of the sensorimotor cortex (cortical reflex myoclonus) or reticular formation (reticular reflex myoclonus) is also a cause of action myoclonus. serotonin and gaba neurotransmitters are thought to cause this lack of inhibition, which is a possible explanation as to why improvements are made with the administration of serotonin precursors. systems involved 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 rear of the roof of the mouth, called the soft palate. these contractions may be accompanied by myoclonus in other muscles, including those in the face, tongue, throat, and diaphragm. the contractions are very rapid, occurring as often as 150 times a minute, and may persist during sleep. the condition usually appears in adults and can last indefinitely. people with palatal myoclonus usually regard it as a minor problem; some 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. these muscles may include the tensor tympani and stapedius muscles. it can involve the muscles surrounding the eustachian tube, which include the tensor veli palatini, levator veli palatini, and salpingopharyngeus. those affected describe it as a thumping sound or sensation in the ear. spinal myoclonus is myoclonus originating in the spinal cord, including segmental and propriospinal myoclonus. the latter is usually due to a thoracic generator producing truncal flexion jerk. it is often stimulus-induced with a delay due to the slow conducting propriospinal nerve fibers. stimulus-sensitive myoclonus is triggered by a variety of external events, including noise, movement, and light. surprise may increase the sensitivity of the patient. sleep myoclonus occurs during the initial phases of sleep, especially at the moment of dropping off to sleep, and include familiar examples of myoclonus such as the hypnic jerk. some forms appear to be stimulus-sensitive. some people with sleep myoclonus are rarely troubled by it, or need treatment. if it is a symptom of more complex and disturbing sleep disorders, such as restless legs syndrome, it may require medical treatment. myoclonus can be associated with patients with tourette syndrome. signs and symptoms myoclonic seizure can be described as "jumps" or "jolts" experienced in a single extremity or even the entire body. the feeling experienced by the individual is described as uncontrollable jolts common to receiving a mild electric shock. the sudden jerks and twitching of the body can often be so severe that it can cause a small child to fall. a myoclonic seizure (myo "muscle", clonic "jerk") is a sudden involuntary contraction of muscle groups. the muscle jerks consist of symmetric, mostly generalized jerks, localized in the arms and in the shoulders and also simultaneously with a head nod; both the arms may fling out together and simultaneously a head nod may occur. symptoms have some variability amongst subjects. sometimes the entire body may jerk, just like a startle response. as is the case with all generalised seizures, the patient is not conscious during the event but the seizure is so brief that the person appears to remain fully conscious. in reflex epilepsies, myoclonic seizures can be brought on by flashing lights or other environmental triggers (see photosensitive epilepsy). familiar examples of normal myoclonus include hiccups and hypnic jerks that some people experience while drifting off to sleep. severe cases of pathologic myoclonus can distort movement and severely limit a person's ability to sleep, eat, talk, and walk. myoclonic jerks commonly occur in individuals with epilepsy. cause myoclonus in healthy individuals may indicate nothing other than 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, as a side effect of certain drugs (such as tramadol, quinolones, benzodiazepine, gabapentin, sertraline, lamotrigine, opioids), or other disorders. benign myoclonic movements are commonly seen during the induction of general anesthesia with intravenous medications such as etomidate and propofol. these are postulated to result from decreased inhibitory signaling from cranial neurons. prolonged oxygen deprivation to the brain, hypoxia, may result in posthypoxic myoclonus. people with benign fasciculation syndrome can often experience myoclonic jerking of limbs, fingers and thumbs. myoclonus can occur by itself, but most often as 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. myoclonic jerks commonly occur in persons with epilepsy, a disorder in which the electrical activity in the brain becomes disordered leading to seizures. it is also found in merrf (myoclonic epilepsy with ragged red fibers), a rare mitochondrial encephalomyopathy. jerks of muscle groups, much of the body, or a series in rapid succession, which results in the person jerking bolt upright from a more relaxed sitting position is sometimes seen in ambulatory patients being treated with high doses of morphine, hydromorphone, and similar drugs, and is possibly a sign of high and/or rapidly increasing serum levels of these drugs. myoclonic jerks caused by other opioids, such as tramadol and pethidine, may be less benign. medications unrelated to opioids, such as anticholinergics, are known to cause myoclonic jerks. pathophysiology most