Myoclonus : Causes, Symptoms, Diagnosis & Treatment

Last Updated: 21/08/2022

Myoclonus is involuntary movements, fast jerky contractions of individual muscles or their groups. The musculature of the limbs, trunk, or face is usually involved without loss of consciousness. Myoclonus are physiological or pathological, the development of which is associated with epilepsy, degenerative and infectious diseases, metabolic-hypoxic disorders. Diagnosis is carried out by clinical, laboratory and instrumental methods (MRI, EEG). Treatment involves the elimination of reversible conditions and supportive care.

Causes of myoclonus

Physiological processes

Sometimes muscle twitching is considered a variant of the norm. Physiological myoclonus is most often observed during falling asleep and in the early phase of sleep (hypnagogic), especially after physical or emotional overwork. Depending on the degree of muscle involvement, they are focal, multifocal, generalized. In children under six months of age, such movements may occur during feeding or during play.

Fast and short muscle contractions are provoked by sudden stimuli - light, sound, motor. Combined with autonomic changes (sweating, palpitations, shortness of breath), they resemble a startle response. Another common situation is diaphragmatic myoclonus, or hiccups, caused by irritation of the vagus nerve from swallowing air or fast food.

Myoclonus epilepsy

Myoclonic seizures are included in the clinical picture of various forms of epilepsy. At the same time, several ways of their development are distinguished, taking into account the localization of the primary focus of excitation in the central nervous system - cortical, thalamocortical, with an unknown mechanism. Pathological impulses from the cortex of the motor areas of the brain are characteristic of the following myoclonus:

  • Cortical reflex: progressive myoclonus epilepsy, eyelid myoclonus with absences.
  • Cortical with rhythmic rapid outbreaks: Angelman syndrome, non-progressive encephalopathy (with tuberous sclerosis, Down syndrome), familial myoclonic epilepsy.
  • Secondarily generalized: Dravet and Lennox-Gastaut syndrome.

Most progressive myoclonus epilepsy is characterized by autosomal recessive inheritance. This is an extensive group of diseases, which includes storage diseases (Gaucher, neuronal lipofuscinosis, GM2-gangliosidosis), Lafora's disease, Unferricht-Lundborg's disease. They also include sialidosis and dentarubro-pallidoleuis atrophy.

The clinical picture of myoclonus epilepsy is varied. Along with rapid spontaneous twitches in the distal extremities, partial and generalized seizures (clonic, tonic-clonic), absences are observed. Severe cortical myoclonus is accompanied by cerebellar disorders, which can lead to immobilization of the patient.

Benign myoclonus of infancy is a condition in which the only symptom is twitches in the shoulder girdle, either in isolation or in series. Such paroxysms may be accompanied by a simultaneous decrease in the tone of the muscles of the neck, which is described as a quick nod of the head. Some of these seizures are triggered by touch.

Degenerative diseases

Myoclonic seizures occur with degenerative damage to the subcortical structures of the central nervous system responsible for the regulation of involuntary movements. They are described as a non-permanent symptom in individuals suffering from dementia with Lewy bodies (LBW), Huntington's chorea, progressive supranuclear palsy. Similar manifestations are observed in Parkinson's disease, Alzheimer's disease, Hunt's cerebellar myoclonic dyssynergy.

Myoclonus in LTD is a fairly common form of movement disorders. The disease is characterized by symptoms of parkinsonism in the form of finger tremors, slowness of movement and postural instability. Progressive cognitive impairments are noted, visual-spatial, vegetative, neuropsychiatric disorders (hallucinations, delirium, depression) develop early.

Cerebral hypoxia

Widespread myoclonus occurs against the background of hypoxic brain damage. The cause may be cardiac arrest, coma, carbon monoxide poisoning. After deep hypoxia due to a severe attack of suffocation, asphyxia or myocardial infarction, kinetic myoclonuses are observed, described as the Lance-Adams syndrome. In its development, the role of cortical and stem dysregulation of motor functions is assumed.

Hypoxic brain damage is characterized by intentional myoclonus - irregular muscle twitching, which intensifies when the goal is reached (against the background of performing a finger-nose or finger-hammer test). They are observed only in the limb, making a rapid movement. With slow actions, pathological contractions are usually absent.


Infectious pathology

The development of myoclonus is associated with neuroinfections of a viral nature: lethargic, herpetic, tick-borne encephalitis. In the latter case, Kozhevnikov's focal epilepsy is noted. It is manifested by typical myoclonus, combined with focal or secondarily generalized convulsive seizures, focal neurological symptoms (central hemiparesis), mental disorders.

Cortical myoclonus in Kozhevnikov epilepsy affects strictly defined muscle groups. They are constant and do not disappear in a dream, they are characterized by rhythm and stereotyping, they increase with excitement and purposeful movements. Usually such twitches develop only in one hand, less often half of the face on the same side is involved.

Another cause of paroxysms is subacute sclerosing panencephalitis. The disease is manifested by twitching of the limbs, head and torso, sharp flexion movements like nods, multiple dyskinesias. Then mixed convulsions, paresis and paralysis join. In the later stages, decerebrate rigidity, swallowing and breathing disorders, and blindness occur.

metabolic disorders

Dysmetabolic conditions are a common cause of myoclonus. They are caused by a violation of biochemical and energy processes in the monoaminergic neurons of the basal nuclei and the cerebral cortex. Generalized muscle myoclonus is described in uremia, liver failure, electrolyte disorders (hypocalcemia, hyponatremia, hypomagnesemia). Muscle twitches are manifested by hypoglycemia and non-ketonemic hyperglycemia.

Intoxication and drug overdose

The direct neurotoxic effect of chemicals is due to a violation of the formation and conduction of an impulse, a modification of plastic and energy exchanges. Indirect influence is realized through dysfunction of the internal organs responsible for excretion and detoxification. As a manifestation of acute intoxication, myoclonus occurs in case of poisoning with heavy metals (including bismuth), DDT, methyl bromide.

Iatrogenic muscle myoclonus is caused by an overdose of medications. The combination with extrapyramidal and cerebellar symptoms is typical for taking lithium preparations, antipsychotics, tricyclic antidepressants. Twitching can be caused by benzodiazepines, antihistamines, and anticonvulsants. Similar effects have been described for penicillin and cephalosporins.


Muscle contractions are identified on the basis of a clinical examination with a neurological examination. The results of additional studies help the neurologist confirm the cause of myoclonus. Given the etiological diversity of the pathology accompanied by such attacks, various procedures may be present in the diagnostic schemes:

  • Laboratory tests. In a biochemical blood test, attention is paid to electrolytes, kidney and liver tests, and acute phase proteins. Serological diagnostics makes it possible to identify antibodies to infections, and the study of cerebrospinal fluid - to establish the nature of encephalitic reactions.
  • Tomographic methods. If an organic pathology of the central nervous system is suspected, modern neuroimaging tools are used. MRI becomes the most informative for assessing the state of the medulla and membranes. Their origin can be assumed from the signal intensity and the size of the foci.
  • Electroencephalography. The key method for detecting epileptic activity is EEG. Allows you to determine focal or generalized discharges (peaks, spike-waves) with an analysis of their frequency and localization. The study is supplemented by provocative tests - photostimulation, hyperventilation.



Conservative therapy

Therapy is carried out mainly by conservative methods, the volume and nature of medical care are determined by the specific situation. Benign myoclonus does not require treatment; in severe cases, active complex correction is necessary. The basis of treatment is medicines, the action of which is realized in several directions:

  • Etiotropic. For viral infections, interferons, isoprinosine, lamivudine can be prescribed. Improvement in tick-borne encephalitis is achieved after therapy with specific immunoglobulins.
  • Pathogenetic. Of great importance is the correction of impaired metabolism and cerebral hypoxia. For this, electrolytes, glucose, antihypoxants are used. Detoxification involves infusion support, the use of sorbents, antidotes.
  • Symptomatic. A key component of therapy is anticonvulsants. The most effective are clonazepam, valproate, levetiracetam. Some myoclonus respond well to 5-hydroxytryptophan with carbidopa, high doses of piracetam.

With the ineffectiveness of anticonvulsants, the issue of prescribing a ketogenic diet is considered. To eliminate uremia or severe chemical intoxication, extracorporeal methods are indicated - hemodialysis, plasmapheresis, hemosorption. Rehabilitation of patients with encephalopathies involves hyperbaric oxygen therapy, cerebral hypothermia, reflexology.


For the treatment of drug-resistant cortical myoclonus, neurosurgical intervention in the scope of functional hemispherectomy is offered. Some focal seizures require radical elimination of gross organic causes - tumors or angiomas. In Unferricht-Lundborg disease and Lennox-Gastaut syndrome, vagus nerve stimulation is recommended.

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