Myotonic syndrome

Myotonic syndrome is a phenomenon based on slow muscle relaxation after their active contraction. Especially provokes myotonic phenomenon of rapid movement, made with considerable effort. After it, the relaxation phase is delayed for 5-30 seconds. With true myotonia, the patient experiences the greatest difficulties during the first movements; Repeated movements are made freer and after a while can normalize.

Thus, delayed relaxation in myotonia is associated with an increased tone, a decrease which is significantly delayed. In a broad sense, a myotonic syndrome is understood as any impaired relaxation of increased muscle tone, which does not belong to either pyramidal or extrapyramidal hypertonus and can be both transient and permanent.

[1], [2], [3], [4], [5]

Causes of myotonic syndrome

1. Myotonia Thompson (Thomson) and (less often) Myotonia Becker (strongecker).
2. Paramyotonia Eulenburg (Eulenburg).
3. Neuromyotonia (Isaacs syndrome [Isaacs]).
4. Syndrome of the rigid person.
5. Encephalomyelitis with rigidity.
6. Dystrophic myotonia.
7. Schwartz-Jampel syndrome (Schwartz-Jampel).
8. Psedomyotonia with hypothyroidism.
9. Tetanus (tetanus).
10. Pseudomyotonia with cervical radiculopathy.
11. Black widow spider bite.
12. Malignant hyperthermia.
13. Malignant neuroleptic syndrome.
14. Tetania.

Myotonia Thompson

A classic example of myotonic syndrome is Thompson's myotonia, which is a hereditary disease with autosomal-diminant (rarely autosomal recessive - Becker's disease) inheritance and starts at any age, but most often in early childhood or adolescence. In an infant, the initial symptoms are usually noticeable to the mother: the first sucking movements are performed slowly, and then they become more vigorous; after falling while playing, the child cannot stand for a long time; in order to take an object from a child, it is necessary to forcibly unclench his fingers, etc. At school, the patient cannot immediately start writing or quickly get up from behind the desk and go to the blackboard. These children do not participate in games that require quick movements. Crumpy in calf muscles are fairly typical. Slow relaxation of the muscles is sometimes accompanied by their myotonic spasm. Passive movements and voluntary movements performed with little effort or slowly are not accompanied by myotonic spasm. Myotonic spasms can be observed in various groups: in the muscles of the arms and legs, neck, chewing, oculomotor, facial muscles, in the musculature of the tongue and torso. Cold enhances the manifestations of myotonia, alcohol - facilitates. The state of tonic spasm in myotonia is measured in most cases by seconds and almost never lasts more than one or two minutes. Quite often, patients complain of pain in various parts of the body.

Thompson's myotonia is characterized by an athletic physique and marked hypertrophy (sometimes it is more or less selective in localization) of striated muscles. A valuable test for identifying myotonia is walking up the stairs. When walking on a flat floor, difficulties arise especially often after a long rest, as well as when changing tempo or character of movement. Myotonic spasms in the hands make it difficult to write, shake hands, and other manipulations. A myotonic phenomenon can manifest itself in articulation by pronouncing the first few words (blurred speech); during swallowing (first swallowing). Sometimes the first chewing movements are difficult, etc. In some patients, myotonic spasm is observed in the circular muscles of the eyes. Attempting to open your eyes after squeezing your eyes hard is difficult; the resulting spasm is eliminated gradually, sometimes in 30-40 seconds.

A characteristic manifestation of myotonia is an increase in the mechanical and electrical excitability of muscles: the so-called “percussion myotonia” and “myotonic phenomenon” in EMG studies. When struck with a neurological hammer, a characteristic depression is formed at the site of impact, which is noticeable in the deltoid, gluteal muscles, muscles of the thigh and lower leg, and especially in the muscles of the tongue. The simplest phenomenon is the ghosting of the thumb when hitting the hammer with the thumb. The sharp clenching of the fingers is also illustrative, after which the patient cannot immediately unclench him. The duration of myotonic pits reflects the severity of myotonia as a whole. It is noticed that after sleep myotonic symptoms may temporarily increase. The course of the disease after the initial period of growth is generally stationary.

Also described is the so-called remittent myotonia (myotonia, aggravated by an excess of potassium), the clinical manifestations of which are similar to Thompson's disease. Myotonia is generalized, manifesting itself in the muscles of the face. Characterized by fluctuations in the severity of myotonia from day to day (increasing after intense physical exertion or after ingestion of large amounts of potassium from food). On EMG detected myotonic phenomenon; no pathology is detected in muscle biopsy specimens.

[6], [7], [8]

Paramyotonia Eilenburg

Eulenburg paramyotonia is a rare autosomal dominant disease called congenital paramyotonia. Outside cooling, patients feel healthy. Often, well-developed muscles and an increase in the mechanical excitability of the muscles are revealed (“hole” in the tongue, a symptom of the thumb). After general cooling (rarely after local), a muscle spasm resembles myotonic one develops. First of all, the muscles of the face are involved (circular muscle of the eyes, mouth, chewing, sometimes oculomotor muscles). Also characterized by the involvement of the muscles of the distal arms. As with myotonia, after a sharp contraction of these muscles, a sharp difficulty of relaxation arises. However, unlike Thompson’s myotonia, with repeated movements this spasm does not diminish, but, on the contrary, increases (stiffness).

The majority of patients after muscular spasm soon develop paresis and even paralysis of the affected muscles, the duration of which ranges from several minutes to several hours and even days. These paralyzes develop on the background of hypokalemia or hyperkalemia. Very rarely, patients with congenital paramyotonia exhibit constant muscle weakness and atrophy. Muscle biopsy reveals mild signs of myopathy. The activity of enzymes in the blood is normal.

[9]

Neiromyotonia

Neuromyotonia (Isaacs syndrome, pseudomyotonia, the syndrome of constant muscle fiber activity) begins at any age (more often in 20-40 years) with a constant increase in muscle tone (stiffness) in the distal arms and legs. Gradually, the process extends to the proximal limbs, as well as the muscles of the face and throat. The muscles of the trunk and neck are involved less often and to a lesser extent. As a result of permanent muscle hypertonus, which does not disappear in a dream, flexion muscle contractures begin to form. Characterized by persistent, large, slow fascicular twitches (myokimii) in the muscles of the arms and legs. Active movement can increase muscle tension (resembling spasms). Mechanical excitability of the muscles is not increased. Tendon reflexes are reduced. The disease slowly progresses with a tendency to generalize the process. The gait in a rigid rigid manner is the “battleship” gait. On EMG - spontaneous irregular activity at rest.

[10], [11], [12], [13]

Rigid Man Syndrome

The syndrome of a rigid person (stiff-man syndrome; stiff-person syndrome) in typical cases begins in the third - fourth decade of life with the imperceptible appearance of stiffness in the axial muscles, especially in the muscles of the neck and lower back. Gradually, muscle tension spreads from axial to proximally located muscles. In advanced stages, there is a tendency (rarely) to involve distal limbs and, sometimes, faces. Typically, a symmetrical permanent muscle tension in the limbs, torso and neck is detected; muscles dense on palpation. Rigidity of the abdominal wall and paraspinal muscles leads to a characteristic fixed hyperlordosis in the lumbar region, which persists at rest. This postural phenomenon is so typical that, in its absence, the diagnosis should be questioned. Movement difficult due to the sharp rigidity. Muscle tension in the chest can hinder breathing.

Against the background of muscle rigidity, any sudden stimuli of a sensory or emotional nature provoke agonizing (painful) muscle spasms. Unexpected noise, a harsh sound, active and passive movements in the limbs, touch, fear and even swallowing and chewing can serve as triggering stimuli. Rigidity decreases during sleep, anesthesia, and benzodiazepine or baclofen. However, even in a dream, hyperlordosis is not eliminated, which can be very pronounced (the doctor's hands pass freely under the paraspinal muscles when the patient is lying down).

Approximately one third of patients with the syndrome of a rigid person develop type 1 diabetes mellitus and other autoimmune diseases (thyroiditis, myasthenia, pernicious anemia, vitiligo, etc.), which makes it possible to attribute this disease to autoimmune. This is also confirmed by the fact that 60% of patients have a very high titer of antibodies to glutamic acid decarboxylase.

A variant of the rigid human syndrome is the Jerking stiff-man syndrome (“Jerking stiff-man syndrome”), in which, in addition to constant muscular tension, there are fast, pronounced (night and day) myoclonic twitches of the axial and proximal muscles of the extremities. Myoclonic shudders usually appear on the background of the disease existing for several years and respond to diazepam. In these patients, a stimulus-sensitive myoclonus is often detected.

Differential diagnosis is carried out with Isaacs syndrome, in which myocomia are detected on EMG. Sometimes it is necessary to exclude spasticity in pyramidal syndrome (however, in a rigid human syndrome, there are no high reflexes) and rigidity in patients with progressive supranuclear paralysis (symptoms like parkinsonism and dystrophy take place here). Powerful muscle spasms often cause the disease to differentiate with tetanus, but trismus is not characteristic of the syndrome of a rigid person. Electromyography allows to differentiate this syndrome not only with Isaacs syndrome, but also with different variants of myopathy and muscular dystrophy.

[14], [15]

Progressive encephalomyelitis with rigidity

Progressive encephalomyelitis with rigidity (or “subacute myoclonic spinal neuronitis”) is also manifested by rigidity of the axial and proximal muscles and painful muscle spasms, which are also provoked by sensory and emotional stimuli. Chance of easy pleocytosis in the cerebrospinal fluid. In neurological status, sometimes, as the disease progresses, a non-grave cerebellar ataxia is detected. MRI eliminates this disease.

[16]

Dystrophic myotonia

Dystrophic myotonia (or myotonic dystrophy) is probably the most frequent form of myotonia and is characterized by three main syndromes:

1. myotonic type of movement disorder;
2. myopathic syndrome with a characteristic distribution of amyotrophy (damage to the muscles of the face, neck, distal arms and legs);
3. involvement in the process of endocrine, autonomic and other systems (multisystem manifestations).

The age of onset of the disease and its manifestations are very variable. Myotonic disturbances are more pronounced in the flexor of the fingers (the hardening of objects is made most difficult); with repeated movements, the myotonic phenomenon diminishes and disappears. Muscle weakness and atrophy usually appear later. They seize the facial muscles, especially the chewing, including the temporal, vomiting muscles and the muscles that lift the upper eyelid, perioral muscles; a typical appearance develops: amymia, half-eyed eyelids, underlined temporal fossae, diffuse atrophy of the facial muscles, dysarthria and a low, deaf voice. Atrophy of the distal arms and the peroneal muscle group of the legs is often noted.

Characterized by the presence of cataracts; in men, testicular atrophy and impotence; in women, infantilism and early menopause. In 90% of patients, certain abnormalities on the ECG, mitral valve prolapse, and disorders of the motor functions of the gastrointestinal tract are detected. MRI often reveals cortical atrophy, dilatation of the ventricles, focal changes in the white matter, abnormalities in the temporal lobes. Hyperinsulinemia is often detected. CPK level is usually normal. On the EMG - characteristic myotonic discharges. In muscle biopsy - various histological disorders.

[17], [18]

Schwarz-Jampel Syndrome

Schwartz-Jampel syndrome (chondrodystrophic myotonia) begins in the first year of life and is manifested by a sharp difficulty in relaxing the contracted muscles in combination with increased mechanical and electrical excitability of the muscles. Sometimes there are spontaneous contractions of muscles and crumpy. Some muscles are hypertrophied and dense with palpation at rest. Painful contractions are observed in the limbs, abdominal muscles, and also in the face (myotonic blepharospasm; painful contractions of the muscles of the larynx, tongue, pharynx, which can sometimes cause asphyxia). Very often, various skeletal anomalies are identified - dwarfism, short neck, kyphosis, scoliosis, facial asymmetry, retrognathia, etc. As a rule, mental retardation occurs. On the EMG - myotonic discharges.

[19], [20]

Pseudomyotonia with hypothyroidism

This syndrome is manifested by a slow contraction and the same slow relaxation of the muscles, which is clearly detected when the tendon reflexes are called, especially the Achilles reflex. Muscles are edematous. There is no typical myotonic discharge on the EMG; after an arbitrary reduction, aftereffect potentials are sometimes visible. To recognize pseudomyotonia in hypothyroidism, timely diagnosis of hypothyroidism is important.

[21], [22], [23], [24], [25], [26]

Tombstone

Tetanus (tetanus) is an infectious disease. Trismism (jaws on the lock) is the first symptom of tetanus in 80% of cases. Following the trisism, and sometimes simultaneously with it, tension of the muscles of the neck and flattening of the muscles of the face (facies tetanica) appear: the forehead shrivels, the eye slits narrow, the mouth stretches in a laughing grimace (“sardonic smile”). One of the cardinal signs of tetanus is dysphagia. With an increase in the tension of the occipital muscles, first it becomes impossible to tilt the head forward, then the head is thrown backwards (opisthotonus). A spasm of the back muscles develops; muscles of the trunk and abdomen are tense, become very prominent. The abdomen acquires a bench-like hardness, abdominal breathing becomes difficult. If the rigidity covers the limbs, then in this position the whole body of the patient can take the form of a pillar (orthotonus), as a result of which the disease got its name. The cramps are very painful and occur almost continuously. Any external stimuli (touch, knock, light, etc.) provoke general tetanic convulsions.

In addition to the generalized, the so-called local tetanus (“facial paralytic tetanus”) is also described.

The differential diagnosis of tetanus is carried out with tetany, rabies, hysteria, epilepsy, meningitis, strychnine poisoning.

Pseudomyotonia with cervical radiculopathy

This is a rare syndrome observed with the defeat of the root C7. Such patients complain of the difficulty of opening the brush after the seizure of the object. Palpation of the hand reveals with this muscle tension (“pseudomyotonia”), which arises due to the paradoxical contraction of the flexors of the fingers when trying to activate the extensors of the fingers.

The black widow spider bite can be accompanied by increased muscle tone, twitching and cramping in the bite area.

[27], [28], [29], [30], [31], [32], [33], [34], [35]

Malignant hyperthermia

Malignant hyperthermia is a hereditary disease transmitted by an autosomal dominant type, which is based on hypersensitivity to certain substances used for anesthesia. There is a slow (clock) or a rapid rise in body temperature, tachycardia, arrhythmia, tachypnea, muscle fasciculations, and an increase in muscle tone. A generalized muscle rigidity and severe metabolic acidosis, myoglobinuria develops. If untreated, epileptic seizures develop and death can occur. The diagnosis is not difficult, as there is a clear connection with anesthesia. The CPK level is about 10 times normal values.

[36], [37], [38], [39], [40], [41]

Malignant Neuroleptic Syndrome (ZNS)

ZNS is a dangerous complication of neuroleptic therapy, manifested by hyperthermia, muscle rigidity and increased levels of CPK. The syndrome is usually accompanied by impaired consciousness (stunned, stupor) and autonomic disorders: tachycardia, arrhythmia, hyperhidrosis. The most frequent and dangerous complication is rhabdomyolysis, which is manifested in acute diffuse muscle breakdown, leading to extremely high levels of CPK, hyperkalemia, myoglobinemia, and acute renal failure, which requires temporary dialysis.

In the differential diagnosis of malignant neuroleptic syndrome, it is recommended to exclude other possible causes of rhabdomyolysis (compression damage, alcohol abuse, heat stroke, prolonged immobilization), as well as malignant hyperthermia, severe dystonic spasms, lethal catatonia, serotonin syndrome.

Sometimes a malignant neuroleptic syndrome has to be differentiated from an infectious lesion of the central nervous system, an allergic reaction to the drug, hyperthyroidism, tetany, and even Parkinson's disease.

[42]

Tetania

Tetany reflects overt or hidden insufficiency of the parathyroid glands (hypoparathyroidism) and is manifested by a syndrome of increased neuromuscular excitability. The apparent form is observed with endocrinopathy and proceeds with spontaneous muscle cramps. The latent form is most often triggered by neurogenic hyperventilation (in the picture of permanent or paroxysmal psycho-vegetative disorders) and is manifested by paresthesias in the limbs and face, as well as by selective muscle cramps (“carpopedal spasms”, “hand of an obstetrician”) and emotional disorders. Trisism and spasm of other facial muscles may be observed. In severe cases, it is possible to involve the muscles of the back, the diaphragm, and even the larynx (laryngospasm). A symptom of Chvostek and a symptom of Trusso-Bansdorf and other similar symptoms are detected. It is also possible to have a low level of calcium (there are also normocalcemic neurogenic variants) and an increase in the phosphorus content in the blood.

Differential diagnosis: it is necessary to exclude diseases of the parathyroid glands, autoimmune processes, psychogenic disorders of the nervous system.

Diagnostic studies for myotonic syndrome

General and biochemical blood tests, urinalysis, studies of electrolytes and CK in the blood; determination of the level of thyroid and parathyroid hormones; EMG; a study of the speed of the excitation of the nerve; muscle biopsy; research of myotonic phenomenon (clinically and electromyographically); genetic analysis and other, according to indications, diagnostic studies (CSF, somatosensory evoked potentials, MRI of the spinal cord and spine, etc.).

[43], [44], [45]