Mioclonus

Myoclonus is a sudden, short, jerky muscle twitch that occurs as a result of an active muscle contraction (positive myoclonus), or (rarely) a drop in the tone of postural muscles (negative myoclonus).

An adequate syndromic description of myoclonus should precede the nosological diagnosis. The latter has several complex clinical characteristics. In particular, the clinical analysis of myoclonus must necessarily take into account its features such as the degree of generalization and distribution pattern (localization), severity, synchronicity / asynchrony, rhythm / arrhythmia, permanent / episodic, dependence on provocative stimuli, dynamics in the wake-sleep cycle.

According to the above characteristics, myoclonic syndromes can vary considerably in individual patients. So, myoclonus is sometimes limited to the involvement of a single muscle, but more often it covers several and even many muscle groups up to complete generalization. Myoclonic jerks can be strictly synchronous in different muscles or asynchronous, for the most part they are arrhythmic and can be accompanied or not accompanied by movement in the joint. Their severity can vary from a barely noticeable reduction to a sharp general wince that can lead to the fall of the patient. Myoclonias can be single or repetitive, very persistent, or fluctuating, or strictly paroxysmal (for example, epileptic myoclonias). Oscillatory myoclonus is characterized by sudden (“explosive”) movements lasting a few seconds, usually caused by unexpected stimuli or active movements. Spontaneous myoclonias (or rest myoclonia) and reflex, provoked by sensory stimuli of different modalities (visual, auditory or somatosensory), are distinguished. There are myoclonias caused by voluntary movements (action, intentional and postural myoclonias). Finally, myoclonias are known, dependent and independent of the wakefulness-sleep cycle (disappearing and not disappearing in sleep, appearing only during sleep).

Distribution allocate focal, segmental, multifocal and generalized myoclonus (similar to dystonia syndromic classification).

The above clinical characteristics of myoclonus (or, in other words, syndromic analysis), usually complement the pathophysiological and etiological classification.

[1], [2], [3]

Symptomatic myoclonus

Symptomatic (secondary) myoclonus develops in the framework of various neurological diseases.

Diseases of accumulation are represented by a number of diseases in which a characteristic set of syndromes is revealed in the form of epileptic seizures, dementia, myoclonus, and some neurological and other manifestations. Many of these diseases begin in infancy or childhood.

• Lafore's disease is a rare disease inherited in an autosomal recessive manner. The disease makes its debut in 6-19 years. Characterized by generalized tonic-clonic epileptic seizures, which are often combined with partial occipital paroxysms in the form of simple visual hallucinations, the appearance of cattle or more complex visual disorders. Visual paroxysms is a characteristic sign of Lafory's disease, in 50% of patients they occur already in the early stages of the disease. Soon the severe myoclonic syndrome develops, which often obscures the ataxia that has joined. Transient cortical blindness is described. In the terminal stage, severe dementia develops, patients are bedridden. On EEG - epileptic activity in the form of complexes “spike-slow wave” and “polyspike-slow wave”, especially in the occipital regions. In diagnosis, great importance is attached to the detection of Lafory bodies in a skin biopsy in the area of the forearm (with light microscopy). Fatal outcome occurs after a few years from the onset of the disease.
• GM ₂ -gangliosidosis (Tay-Sachs disease) is inherited in an autosomal recessive manner and makes its debut in the first year of life with mental retardation, progressive generalized hypotension, blindness, and the loss of all voluntary movements are detected in neurological status. Hypotension is replaced by spasticity and opisthotonus, epileptic generalized and partial myoclonic seizures and helolepsy develop. When examining the fundus reveal a symptom of "cherry seed". Patients die in the 2-3rd year of life.
• Ceroid lipofuscinosis is characterized by the deposition of lipopigments in the CNS, hepatocytes, cardiac muscle, retina. There are several types of ceroid lipofuscinosis: infantile, late infantile, early juvenile (or intermediate), juvenile, adults. In all cases, the central manifestation is progressive myoclonus epilepsy. Electron microscopy of the skin and lymphocytes reveals characteristic profiles in the form of "fingerprints".

• Sialidos.
  • Myoclonus with “cherry bone” refers to type I sialidosis. The basis of the disease is the deficiency of neuroaminidase (type of inheritance - autosomal recessive). The disease begins between 8 and 15 years. The main symptoms are: visual impairment, myoclonia and generalized epileptic seizures. Myoclonus is observed at rest, it increases with voluntary movements and when touched. Sensory stimulation provokes the development of massive bilateral myoclonia. The most typical symptom is myoclonus of the facial muscles: spontaneous, irregular, with predominant localization around the mouth. Facial myoclonus persists during sleep. Characterized by ataxia. In the fundus - the symptom of "cherry bone", sometimes - clouding of the vitreous body. The flow is progressive. On EEG - complexes “spike-slow wave”, coinciding with generalized myoclonias.
  • Another rare form of sialidosis is galactosialidosis. Manifested by galactosidase deficiency (determined in lymphocytes and fibroblasts), which is manifested by the presence of mental retardation, angiokeratoma, chondrodystrophy and short stature, epileptic seizures and myoclonic hyperkinesis.
• Gaucher disease is known in 3 forms: infantile (type I), juvenile (type II) and chronic (type III). It is type III that can sometimes be manifested by progressive myoclonus epilepsy, as well as splenomegaly, decreased intelligence, cerebellar ataxia, pyramidal syndrome. On EEG - epileptic activity in the form of complexes "polyspayk-slow wave", in some cases, the amplitude of the SSEP. Glucocerebroside accumulations are found in the biopsy material of various organs, lymphocytes, and bone marrow.

Hereditary degenerative diseases of the cerebellum, brain stem and spinal cord (spinocerebellar degeneration).

• Unferrich-Lundborg disease is the most well-known form of so-called progressive myoclonus epilepsy. Two populations of patients with this disease were studied in detail: in Finland (this variant of myoclonus was recently called the Baltic myoclonus) and the Marseilles group (Ramsay Hunt syndrome, also called the Mediterranean myoclonus). Both variants have a similar clinical picture, age of onset of the disease and type of inheritance (autosomal recessive). In about 85% of cases, the disease begins at the 1st – 2nd decade of life (6–15 years). The main syndromes are myoclonic and epileptic. Epileptic seizures are more often clonic-tonic-clonic. The action myoclonus gradually progresses and becomes the main maladaptive factor. Myoclonus can transform into a fit. Mild ataxia and a slowly progressive decline in intelligence are also possible. Other neurological symptoms are not characteristic.
• Friedreich's ataxy, in addition to other symptoms, can also manifest itself in myoclonic syndrome. The disease begins before puberty is complete (average of 13 years), typical of slowly progressive ataxia (sensitive, cerebellar or mixed), pyramidal syndrome, dysbasia, dysarthria, nystagmus and somatic disorders (cardiomyopathy, diabetes, skeletal deformities, including Friedreich's foot).

Hereditary degenerative diseases with a primary lesion of the basal ganglia.

• Wilson-Konovalov disease often develops at a young age against the background of symptoms of hepatic dysfunction and manifests polymorphic neurological (various types of tremor, chorea, dystonia, akinetiko-rigid syndrome, myoclonus), mental and somatic (hemorrhagic syndrome) disorders. The study of copper-protein metabolism and the detection of the Kaiser-Fleischer ring allow us to make the correct diagnosis.
• Torsion dystonia is quite often combined with myoclonus (as with tremor), but this combination is especially characteristic of symptomatic myoclonic dystonia (Wilson-Konovalov disease, post-encephalitic parkinsonism, lysosomal accumulation diseases, rejected postoxic dystonia, etc.) and the hereditary dystonia-myoclonus syndrome.
• Gallervorden-Spatz disease is a rare familial disease that begins in childhood (up to 10 years) and is characterized by progressive dysbasia (deformity of the feet and slowly increasing rigidity in the extremities), dysarthria and dementia. In 50% of patients, one or another hyperkinesis is found (chorea, dystonia, myoclonus). In some cases, described spasticity, epileptic seizures, retinitis pigmentosa, optic nerve atrophy. On CT or MRI - a picture of the defeat of the pale ball in connection with the accumulation of iron ("tiger's eyes")
• Cortico-basal degeneration refers to diseases in which myoclonus is considered a fairly typical symptom. Progressive akinetic-rigid syndrome in a patient of mature age, accompanied by involuntary movements (myoclonus, dystonia, tremor) and lateralized cortical dysfunction (limb apraxia, alien hand syndrome, disorders of complex types of sensitivity) suggest suspected cortico-basal degeneration. At the heart of the disease is asymmetric fronto-parietal atrophy, sometimes detected on CT or MRI.

Some diseases that are manifested by dementia, for example, Alzheimer's disease and especially Creutzfeldt-Jakob disease, may be accompanied by myoclonus. In the first case, non-vascular type dementia comes to the forefront in the clinical picture, and in the second case, dementia and myoclonus occur against the background of other progressive neurological syndromes (pyramidal, cerebellar, epileptic, etc.) and characteristic changes in EEG (tri- and polyphasic activity of the acute form with an amplitude of up to 200 µV, arising with a frequency of 1.5-2 Hz).

Viral encephalitis, especially encephalitis caused by the herpes simplex virus, subacute sclerosing encephalitis, econo phalitis, and arbovirus encephalitis, are often accompanied (along with other neurological manifestations) by myoclonus, which is a rather characteristic element of their clinical picture.

Metabolic encephalopathies in diseases of the liver, pancreas, kidneys, and lungs, in addition to disorders of consciousness, often manifest symptoms such as tremor, myoclonus, and epileptic seizures. Negative myoclonus (asterixis) is highly characteristic of metabolic encephalopathy (see below), in these cases it is usually bilateral and sometimes occurs in all limbs (and even in the lower jaw). Asterixis can have both cortical and subcortical origin.

A special group of metabolic encephalopathies is made up of some mitochondrial diseases accompanied by myoclonus, the MERRF and MELAS syndromes.

• Myoclonus epilepsy with “torn” red fibers (Myoclonus Epilepsia, Ragged Red Fiber - MERRF) is inherited in the mitochondrial type. The age of onset of the disease varies from 3 to 65 years. The most typical manifestations are progressive myoclonus-epilepsy syndrome, which is associated with cerebellar ataxia and dementia. The rest of the clinical picture is distinguished by polymorphism: neurosensory deafness, myopathic symptoms, optic nerve atrophy, spasticity, peripheral neuropathy, sensory disturbances. The severity of the flow is also extremely variable. On the EEG, anomalous main activity (80%), “spike-slow wave”, “polyspike-slow wave” complexes, diffuse slow waves, and photosensitivity are noted. Identify giant SSEP. With CT or MRI, diffuse atrophy of the cortex, white matter changes of varying severity, calcification of the basal ganglia and focal cortical foci of low density are found. A study of skeletal muscle biopsy specimens reveals a characteristic pathomorphological feature - “torn” red fibers. Biochemical analysis reveals an increase in lactate levels.
• Mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes (MELAS syndrome) is caused by sharpened mutations of mitochondrial DNA. The first signs of the disease appear most often at the age of 6-10 years. One of the most important symptoms is physical exercise intolerance (after them the state of health deteriorates sharply, muscle weakness and sometimes myalgia appear). Characterized by migraine-like headaches with nausea and vomiting. Another unusual and characteristic symptom is stroke-like episodes with headache, focal neurological symptoms (paresis and paralysis of the limbs and muscles innervated by BN, comatose states); they are provoked by fever, intercurrent infections and are prone to relapse. Their cause is acute insufficiency of energy resources in cells and, as a result, high sensitivity to potential toxic effects (“metabolic strokes”). Characterized by epileptic seizures (partial and generalized convulsive), myoclonus, ataxia. As the disease progresses, dementia develops. In general, the picture is very polymorphic and variable in individual patients. Myopathic syndrome is also variable and usually mild. A biochemical examination of blood reveals lactate acidosis, and a morphological study of skeletal muscle biopsy is a symptom of "torn" red fibers.

Toxic encephalopathy, manifested, in addition to other symptoms, myoclonus, can develop with poisoning (bismuth, DDT) or the use / overdose of certain drugs (antidepressants, anesthetics, lithium, anticonvulsants, levodopa, MAO inhibitors, neuroleptics).

Encephalopathy caused by exposure to physical factors can also manifest a typical myoclonic syndrome.

• Posthypoxic encephalopathy (Lants-Adams syndrome) is characterized by intentional and actional myoclonias, sometimes in combination with dysarthria, tremor and ataxia. In severe cases, the patient is relieved of myoclonus only in the position of complete relaxation of the prone position, any movement attempts lead to an “explosion” of generalized myoclonias, which deprive any possibility of independent movement and self-service. The drug of choice is clonazepam, and the good effect of this drug is considered one of the confirmations of the diagnosis.
• Myoclonus in severe traumatic brain injury can be as its only consequence, or combined with other neurological and psychopathological disorders.

The focal lesions of the central nervous system (including the dento-olive, causing palatine myoclonus) of different etiologies (stroke, stereotactic intervention, tumor), in addition to myoclonus, are accompanied by distinct concomitant neurological symptoms and relevant data history, which facilitates diagnosis.

Spinal myoclonus is characterized by local distribution, stability of manifestations, independence from exogenous and endogenous influences, it develops with various lesions of the spinal cord.

[4], [5], [6], [7], [8],

Pathophysiological classification of myoclonus

The pathophysiological classification of myoclonus indicates the source of its generation in the nervous system:

• cortical (somatosensory cortex);
• subcortical (between the cortex and the spinal cord);
• stem (reticular);
• spinal;
• peripheral (with damage to the spinal roots, plexuses and nerves).

Some authors unite a subcortical and stem myoclonus into one group.

• Cortical myoclonias are preceded by changes on the EEG in the form of spikes, spike-slow wave complexes, or slow waves. The latent period between EEG and EMG discharges corresponds to the time of excitation along the pyramidal tract. Cortical myoclonus can be spontaneous, provoked by movement (cortical action myoclonus) or external stimuli (cortical reflex myoclonus). It can be focal, multifocal or generalized. Cortical myoclonus often distal and occurs in the flexor; often combined with kozhevnikovskoy epilepsy, Jacksonian and secondary-generalized tonic-clonic seizures. A pathological increase in the amplitude of an SSEP is noted (up to the formation of giant SSEPs). Furthermore, when the cortical myoclonus polysynaptic significantly enhanced long-hinge (long-loop) reflexes.
• In the subcortical myoclonus, temporary connections between the EEG and the EMG are not traceable. EEG discharges may follow myoclonus or be absent altogether. Subcortical myoclonus can be generated by the thalamus and is manifested by generalized, often bilateral myoclonias.
• Reticular myoclonus is generated in the brain stem due to increased excitability of the caudal part of the reticular formation, mainly the giant cell nucleus, from which impulses propagate caudally (to spinal motoneurons) and rostral (to the cortex). A reticular myoclonus is often characterized by generalized axial twitching, with proximal muscles being involved more than distal muscles. In some patients it may be focal. A reticular myoclonus can be spontaneous, actional and reflex. In contrast to the cortical, with the reticular myoclonus, there is no connection between changes in EEG and EMG, as well as giant SSEPs. Polysynaptic reflexes are enhanced, but not the cortical evoked response. Reticular myoclonus may resemble an enhanced start-reflex (primary hyperexpletion).
• Spinal myoclonus can occur with heart attacks, inflammatory and degenerative diseases, tumors, spinal cord injuries, spinal anesthesia, etc. In typical cases, it is focal or segmental, spontaneous, rhythmic, not sensitive to external stimuli and, unlike myocloni of cerebral origin, does not disappear during sleep. With spinal myoclonus, EMG activity accompanies each muscle contraction, and EEG correlates are absent.

If the pathophysiological classification is attempted to be tied to specific diseases, then it will look like this.

• Cortical myoclonus: tumors, angiomas, encephalitis, metabolic encephalopathy. Among degenerative diseases, this group includes progressive moklonus-epilepsy (MERRF syndrome, MELAS syndrome, lipidosis, Lafory's disease, ceroid lipofuscinosis, familial cortical myoclonic tremor, Unferriht-Lundborg disease with Baltic and Mediterranean myoclonus disease, I have an illness. -Palid-Lewis atrophy), juvenile myoclonic epilepsy, post-toxic Lance-Adams myoclonus, Alzheimer's disease, Creutzfeldt-Jakob disease, Huntington's trochaic, olivopontocerebellar money degeneration, cortico-basal degeneration. Kozhevnikovskaya epilepsy, in addition to tick-borne encephalitis, may be associated with Rasmussen's encephalitis, stroke, tumors, and, in rare cases, with multiple sclerosis.
• Subcortical myoclonus: Parkinson's disease, multiple systemic atrophy, cortico-basal degeneration. Cyclopathic myoclonus should be attributed to this group (idiopathic, with stroke, tumors, multiple sclerosis, traumatic brain injury, neurodegenerative diseases).
• Spinal myoclonus: inflammatory myelopathy, tumors, injuries, ischemic myelopathy, etc.
• Peripheral myoclonus: damage to peripheral nerves, plexuses and roots.

[9], [10], [11], [12]

Etiological classification of myoclonus

It should be noted that the pathophysiological mechanism of some myoclonic syndromes is still poorly known; therefore, the etiological classification should be considered more convenient for the doctor, dividing the myoclonus into 4 groups: physiological, essential, epileptic, symptomatic (secondary).

• Physiological myoclonus.
  • Sleep myoclonium (falling asleep and awakening).
  • Myoclonus fright.
  • Myoclonus caused by intense physical exertion.
  • Hiccup (some of its variants).
  • Benign infant myoclonus when feeding.
• Essential myoclonus.
  • Hereditary myoclonus-dystonia syndrome (multiple Friedreich para-myoclonus or myoclonic dystonia).
  • Night myoclonus (periodic movements of the limbs, restless legs syndrome).
• Epileptic myoclonus.
  • Kozhevnikovskaya epilepsy.
  • Myoclonic absansy.
  • Infantile spasms.
  • Lennox-Gasto syndrome.
  • Juvenile myoclonic epilepsy of Jans.
  • Progressive myoclonic epilepsy and some other young epilepsies.
• Symptomatic myoclonus.
  • Diseases of accumulation: Lafory Taurus disease, GM -gangliosidosis, (Tay-Sachs disease), ceroid lipofuscinosis, sialidosis, Gaucher disease.
  • Hereditary degenerative diseases of the cerebellum, brain stem and spinal cord (Spinocerebellar degeneration): Baltic myoclonus (Unferriht-Lundborg disease), Mediterranean myoclonus (Ramsay Hunt syndrome), Friedreich ataxia, ataxia-telangiectasia.
  • Degenerative diseases with a predominant lesion of the basal ganglia: Wilson-Konovalov disease, torsion dystonia, Hallervorden-Spatz disease, cortico-basal degeneration, progressive supranuclear palsy, Huntington’s chorea, multiple system atrophy, etc.
  • Degenerative dementias: Alzheimer's disease, Creutzfeldt-Jakob disease.
  • Viral encephalitis (herpetic encephalitis, subacute sclerosing panencephalitis, Economo encephalitis, arbovirus encephalitis, etc.).
  • Metabolic encephalopathy (including mitochondrial, as well as with liver or kidney failure, dialysis syndrome, hyponatremia, hypoglycemia, etc.).
  • Toxic encephalopathy (bismuth intoxication, antidepressants, anesthetics, lithium, anticonvulsants, levodopa, MAO inhibitors, neuroleptics).
  • Encephalopathy caused by exposure to physical factors (post-hypoxic Lanz-Adams syndrome, post-traumatic myoclonus, heat stroke, electric shock, decompression).
  • Focal lesion of the central nervous system (stroke, neurosurgical operations, tumors, TBI).
  • Spinal cord injury.
• Psychogenic myoclonus.

[13], [14]

Physiological myoclonus

Physiological myoclonus can occur under certain circumstances in a healthy person. This group includes sleep myoclonia (sleep and awakening); fright myoclonia; myoclonus caused by intense physical exertion; hiccups (some of its variants) and benign myoclonias of babies when feeding.

• Sometimes natural physiological shudders when falling asleep and awakening in anxious individuals can be a cause for fear and neurotic experiences, but they are easily eliminated by rational psychotherapy.
• Fear myoclonias can be not only physiological, but also pathological (startl-syndrome, see below).
• Intense physical activity can cause a single transient myoclonic contractions of a benign character.
• Hiccup is a frequent phenomenon. The basis of this symptom is myoclonic contraction of the diaphragm and respiratory muscles. Myoclonus can be both physiological (for example, after overeating) and pathological (for gastrointestinal diseases or, less commonly, chest organs), including for diseases of the nervous system (stimulation of the phrenic nerve, damage to the brain stem, or damage to the upper cervical spinal cord brain). Hiccups can be caused by toxic effects. Finally, it can be purely psychogenic.

[15], [16], [17]

Essential myoclonus

Essential myoclonus is a rather rare hereditary disease. There are both familial (autosomal dominant inheritance) and sporadic forms. The disease begins on the 1st or 2nd decade of life and is not accompanied by other neurological and mental disorders, there are no changes in the EEG. Clinical manifestations include irregular, arrhythmic and asynchronous twitching and flinching with multifocal or generalized myoclonia distribution. The latter are amplified by voluntary movements. The SSEP is not enlarged even during myoclonic movement, which indicates its subcortical origin. Until recently, this disease was called Friedreich's multiple paramyoclonus. Since it can cause dystonic symptoms (the so-called dystonic myoclonus), and the syndrome itself is sensitive to alcohol, multiple paramyoclonus and myoclonic dystonia are now considered the same disease and are called hereditary myoclonus-dystonia syndrome.

Another form of essential myoclonus is the nocturnal myoclonus, known as the “periodic movements of the limbs” (a term proposed in the international classification of sleep disorders). This disorder is not a true myoclonus, although it is included in modern classifications of myoclonic syndromes. The disease is characterized by episodes of repetitive, stereotypical movements in the legs in the form of extension and flexion in the hip, knee and ankle joints, which occur during the superficial (I-II) sleep stages and are often accompanied by dyssomnic disorders. Movement is not accompanied by changes in EEG or awakening. Periodic movements in sleep can be combined with restless legs syndrome. The latter is characterized by suddenly advancing and rapidly increasing paresthesias in the legs, usually arising before the start of sleep and causing an overwhelming need to move the legs. A short movement of the foot instantly eliminates the feeling of discomfort. In both syndromes, levodopa and benzodiazepine (usually clonazepam) and opiates are usually effective.

[18], [19], [20], [21], [22], [23],

Epileptic myoclonus

In epileptic myoclonus, myoclonic seizures dominate in the clinical picture, but there are no signs of encephalopathy, at least in the initial stages. Epileptic myoclonus can manifest itself in the form of isolated epileptic myoclonic twitches during epilepsia partialis continua (Kozhevnik epilepsy), photosensitive epilepsy, idiopathic “stimulus-sensitive” myoclonus, myoclonic absans. This group includes the group of pediatric myoclonic epilepsies with more extensive manifestations: infantile spasms, Lennox-Gastaut syndrome, juvenile myoclonic epilepsy of Janz, progressive myoclonic epilepsy, early myoclonic encephalopathy, benign myoclonic epilepsy of infants.

Kozhevnikovskaya epilepsy (epilepsia partialis continud) was originally described as one of the variants of the chronic form of tick-borne spring-summer encephalitis, it is manifested by constant focal low-amplitude rhythmic clonic muscle contractions (cortical myoclonus) involving one part of the body. The muscles of the face and distal extremities are often involved. The twitches are constant, they usually last for many days and even years, sometimes they observe a secondary generalization into a tonic-clonic seizure. A similar syndrome, but with a progressive course, has been described with a more diffuse hemispheric lesion (Rasmussen’s chronic encephalitis), its nosological independence remains controversial. Kozhevnikovskaya epilepsy syndrome is also described in such diseases as abscess, granuloma, stroke, subdural hematoma, tumor, brain-brain trauma, non-ketotic hyperglycemic state (especially in the presence of hyponatremia), hepatic encephalopathy, multiple sclerosis, a syndrome, a syndrome, hyponatremia, hepatic encephalopathy, multiple sclerosis, syndromic syndrome, multiple sclerosis, a syndrome of hyponatremia, hepatic encephalopathy, multiple sclerosis, syndromic syndrome, hepatic encephalopathy, multiple sclerosis, a syndrome of hyponatremia, hepatic encephalopathy, multiple sclerosis, syndromic syndrome, hepatic encephalopathy, multiple sclerosis, syndromic syndrome, hepatitis Iatrogenic forms are also described (penicillin and others).

Myoclonic absansy. The average age of onset of epilepsy with myoclonic absences (Tassinari syndrome) is 7 years (from 2 to 12.5 years). The sudden onset of abscess is accompanied by bilateral rhythmic myoclonic flinches, which are observed in the muscles of the shoulder girdle, arms and legs, and the muscles of the face are involved to a lesser extent. Movement can increase in intensity and acquire a tonic character. Short jerks and tonic contractions can be symmetrical or dominate on one side, causing a turn of the head and body. During an attack, respiratory arrest and involuntary urination are also possible. The loss of consciousness during an abscess can be complete or partial. Each episode of myoclonic absans can last from 10 to 60 seconds. Seizures can occur many times a day, they become more frequent in the morning (within 1-3 hours after waking up). In rare cases, episodes of the status of myoclonic absences are observed. In most cases, abscesses are combined with generalized convulsive seizures, which are usually characterized by a low frequency (approximately 1 time per month or less). Often, a decrease in intelligence is observed. Anti-convulsant resistance is quite typical. The etiology is unknown, sometimes genetic predisposition is noted.

Infantile spasms (West syndrome) are referred to as age-dependent epilepsy. The first manifestations of the disease occur in 4-6 months. The syndrome is characterized by typical seizures, mental retardation and hypsa rhythm on EEG (irregular high-voltage slow spike-wave activity), which formed the basis of the West triad. Infantile spasms are usually characterized by symmetrical, bilateral, sudden and short contractions of typical muscle groups (flexor, extensor, and mixed spasms). Frequently observed flexor spasms, which are manifested by a short bow (if the abdominal muscles are involved), while the hands make the movement of the cast or lead. Attacks torso torso and bringing hands resemble eastern greeting and were called "Salaam attacks." The frequency of attacks varies greatly (in severe cases, they occur several hundred times a day). Most attacks are grouped into clusters, they often occur in the morning after waking up or when falling asleep. During an attack, eye deviation and nystagmoid movements are sometimes observed. Infantile spasms can be secondary (symptomatic), idiopathic and cryptogenic. Secondary forms are described for perinatal lesions, infections, cerebral malformations, tuberous sclerosis, injuries, congenital metabolic disorders, degenerative diseases. Infantile spasms should be differentiated from benign non-epileptic infantile spasms (benign myoclonus of infants), the latter is not accompanied by epileptic discharges on EEG and passes independently in the coming years (up to 3 years). In the future, 55-60% of children with infantile spasms may experience other types of seizures (Lennox-Gastaut syndrome).

Lennox-Gasto syndrome is characterized by typical EEG changes [spike-slow wave discharges with less frequency (2 Hz) than with typical absans (3 Hz)], mental retardation and special types of seizures, including myoclonic flinches, atypical abscesses and asthmatic seizures (epileptic drop attacks, akinetic seizures).

The syndrome usually begins with sudden drops, seizures become frequent, epileptic statuses occur, intellectual functions deteriorate, and personality disorders and chronic psychosis are possible. Approximately 70% of children with this syndrome have tonic seizures. They are short, last for several seconds and manifest themselves with flexor movements of the head and torso, or extensor movements, as well as deviation of the eyes or the fall of the patient. Seizures may be asymmetrical or mostly unilateral. Sometimes automatic behavior follows the tonic stage. Most tonic seizures develop in sleep.

Atypical absences are observed in approximately one third of patients with Lennox-Gastaut syndrome. They are longer than typical absans, and are accompanied by a variety of motor phenomena (nodding, myoclonus in the face, postural phenomena, etc.). In addition to atonic and tonic seizures, typical myoclonic and myoclonic-atonic seizures, also leading to the fall of the patient (epilepsy with myoclonic-astatic seizures). Other types of seizures are possible (generalized tonic-clonic, clonic; partial seizures are less common). Consciousness usually remains clear. Etiologically, 70% of cases of Lennox-Gastaut syndrome are associated with perinatal lesions.

Juvenile myoclonic epilepsy of Janz (“impulsive petit mal”) begins on the 2nd decade of life (most often at 12-24 years) and is characterized by myoclonic seizures, sometimes associated with generalized tonic-clonic seizures and / or absans. Myoclonic seizures, characterized by sudden short bilaterally symmetric and synchronous muscle contractions, dominate. Movement captures mainly the shoulders and arms, less the muscles of the torso and legs. Attacks are single or grouped into clusters. The patient may fall to his knees in a fit. During myoclonic seizures, the mind remains intact, even if they appear in a series or in a picture of myoclonic epileptic status.

Generalized tonic-clonic seizures in most cases appear after (on average after 3 years) the onset of myoclonic seizures. In typical cases, the seizure begins with myoclonic twitches, increasing in intensity to a generalized myoclonus, which becomes a generalized tonic-clonic seizure. This typical picture is called “myoclonic grand mal, (“ impulsive grand mal, “clonic-tonic-clonic seizure”). Attacks appear almost exclusively after the morning awakening.

Absancies are usually observed in the atypical variant and appear in 15-30% of patients at an average age of 11.5 years. Intellect does not usually suffer.

Severe myoclonic epilepsy in babies begins in the 1st year of life. First, there are generalized or unilateral clonic seizures without prodromal symptoms. Myoclonic twitching and partial seizures usually appear later. Myoclonic seizures often appear in one hand or head, and then transform into generalized ones; they usually occur several times a day. There may also appear atypical absansy and complex partial attacks with atopic or adversive phenomena or automatisms. Characterized by a lag in psychomotor development and the emergence of a progressive neurological deficit in the form of ataxia and pyramidal syndrome. In 15-25% of patients reveal a hereditary burden of epilepsy. MRI does not reveal specific abnormalities.

Early myoclonic encephalopathy begins in the 1st month of life. The early onset of partial myoclonic epileptic jerks is characteristic, they are joined by simple partial seizures (eye deviation, apnea, etc.), then a more massive or generalized myoclonus, tonic spasms (occur later) and other types of seizures. Typical hypotonia of the muscles of the body, bilateral pyramidal signs, possibly involving peripheral nerves. Psychomotor development is impaired. The child either dies in the first 2 years of life, or falls into a persistent vegetative state. The etiology is unknown.

Benign myoclonic epilepsy in infants usually begins with myoclonic shuddering in a normal otherwise otherwise aged child between 4 months and 3 years. Boys are sick more often. Myoclonic jerks can be subtle, but over time they become apparent. Gradually, the seizures are generalized, involving the trunk and extremities, which leads to nodding movements of the head and raising the arms to the sides, as well as flexion of the lower extremities. The deviation of eyes upwards can be observed, perhaps also a sudden fall of the patient. Myoclonic seizures are short (1-3 s), may occur several times a day. Consciousness usually remains intact. There are no other seizure types.

[24], [25],

Other myoclonic syndromes

In completing the description of myoclonus, it is advisable to mention a few more extremely peculiar syndromes, rarely mentioned in the domestic literature.

Palatine myoclonus (myoclonus of the soft palate, cyclic myoclonus, nystagmus of the soft palate, tremor of the soft palate) is one of the manifestations of myorrhythmia. It can be observed in isolation in the form of rhythmic (2-3 in c) contractions of the soft palate or in combination with similar rhythmic myoclonias, almost indistinguishable from tremor, in the tongue, mandible, larynx, diaphragm and distal arms (classical myorhythmia). Myorrhythmia is a rhythmic myoclonus, which differs from tremor (parkinsonian) mainly by its low frequency (1-3 Hz) and characteristic distribution. Sometimes, along with cyclopathic myoclonus, vertical ocular myoclonus (“swing”) is observed, this syndrome is called the ocular palatine myoclonus. Myorrhythmia disappears during sleep (sometimes pathological movements are noticeable in sleep). Myorrhythmia without palatine myoclonus is rare. Isolated myoclonus of the soft palate can be either idiopathic or symptomatic (tumors in the cerebellum and most of the cerebellar cortex, stroke, encephalomyelitis, trauma). Idiopathic myoclonus often disappears during sleep, anesthesia and in a coma. Symptomatic myoclonus of the soft palate is more stable in these conditions. The most common causes of generalized myorrhythmia are vascular lesions of the brain stem and cerebellar degeneration associated with alcoholism or with malabsorption syndrome.

Opsoclonus (“dancing eyes” syndrome) is a myoclonic hyperkinesis of the eye muscles, which is manifested by rapid jerky, chaotic, mainly horizontal movements of the eyeballs. There may be a random change of horizontal, vertical, diagonal, circular and pendulum movements of different frequencies and amplitudes. According to some observations, opsoclonus persists in sleep, intensifying on awakening, it is often mistaken for nystagmus, which differs from opsoclonus by the presence of 2 phases: slow and fast. Opsoclonus indicates an organic lesion of cerebellar-stem connections and is often accompanied by generalized myoclonia, ataxia, intentional tremor, hypotension, etc. The main etiological factors are viral encephalitis, multiple sclerosis, brain stem and cerebellum tumors, paraneoplastic syndromes (especially in children), trauma, metabolic and toxic encephalopathy (drugs, toxins, non-ketotic hyperglycemia).

Negative myoclonus (“fluttering” tremor, asterixis) resembles tremor externally. However, it is not based on active muscle contractions, but, on the contrary, periodic drops in the tone of postural muscles with bioelectric "silence" at these moments. Asterixis is extremely characteristic of metabolic encephalopathy in diseases of the liver, kidneys, lungs, etc. In such cases, it is usually bilateral. Rarely, asterexis can be a sign of local brain damage (hemorrhage in the thalamus, parietal lobe, etc.), manifesting itself in such cases on the one hand. Asterixis is most easily detected when hands are pulled forward.

Start-syndrome unites a group of diseases characterized by an enhanced start-up reaction (startle) in response to unexpected external stimuli (often auditory and tactile).

[26], [27]

Psychogenic myoclonus

Psychogenic myoclonus is characterized by acute onset, variability in frequency, amplitude, and distribution of myocloni. There are also other inconsistencies typical organic myoclonus (for example, the absence of falls and damage, despite the pronounced instability and fluctuations of the body, etc.), spontaneous remission, reduction of hyperkinesis with distraction, amplification and reduction of hyperkinesis under the influence of suggestion, psychotherapy or in response to a placebo, the presence of other psychogenic motor, mental disorders.

[28], [29], [30], [31], [32], [33], [34],

Diagnosis and treatment of myoclonus

Diagnosis is based on clinical data. Treatment begins with the correction of major metabolic disorders. Often prescribed clonazepam 0.5-2 mg orally 3 times / day. It may be effective valprok 250-500 mg orally 2 times / day; sometimes other anticonvulsants help. Many forms of myoclonus respond to serotonin precursor 5-hydroxytryptophan (initial dose 25 mg orally 4 times / day, then increase to 150-250 mg orally 4 times / day) with a decarboxylase inhibitor carbidopa (orally 50 mg in the morning and 25 mg at noon or 50 mg in the evening and 25 mg at bedtime).

[35], [36], [37],