What Is Paramyotonia Congenita?

Myotonia myopathy refers to a group of muscle diseases characterized by the difficulty in relaxation of affected skeletal muscles after contraction, reduction or disappearance after continuous contraction, and cold that can aggravate symptoms. Including tonic muscular dystrophy, congenital myotonia, and paramyotonia.

Causes of Congenital Paramyotonia

Congenital paramuscular ankylosing is an autosomal dominant hereditary disease. So far, it has been clearly identified as a sodium channel disease of skeletal muscle. Its pathogenic gene is located in SCN4A (encoding the subunit of skeletal muscle sodium channel) at 17q23.1 25.3. Gene mutations mainly affect sodium channel inactivation.

Clinical manifestations of congenital paramyotonia

Tonic muscular dystrophy

The most common is an autosomal dominant multisystem disease. Usually onset at the age of 15 to 25 years. The offspring age tends to be earlier than that of the father. More men than women. The affected skeletal muscles are rigid and difficult to relax and progressive muscle atrophy. The above facial muscles, temporal muscles, and sternocleidomastoid muscles are the most prominent. A few types predominate with atrophy of the distal forearm. The patient had a thin face, flat frontal lines, drooping eyelids, raised cheekbones, thick lips, and slightly open mouth, showing a typical axe-like head. The neck is slender and leans forward like a goose neck. Almost all have premature baldness and systemic dysfunction, such as cataracts, male testicular atrophy, diabetes and arrhythmias, megacolon, gallstones, etc. Muscle rigidity was seen when tapping the intermuscular, gastrocnemius, and tongue muscles.

2. Congenital Myotonia

Also known as Thomsen's disease. Most are autosomal dominant and a few are recessive. General skeletal muscle rigidity and hypertrophy, symptoms worsen in cold environments, and symptoms can be relieved after warm and repetitive activities. Severe cases can cause tonic contraction of the whole body muscles after sudden panic and cannot move. The lightest can be found without any conscious complaint, only in the family tree survey. Individual muscle tonicity, the symptoms did not alleviate after repeated muscle contractions, but worsened, known as abnormal muscle rigidity. No signs of muscle atrophy and multiple system damage.

Hypertrophy of muscles throughout the body, big fish, quadriceps, gastrocnemius, etc. can cause throbbing muscle rigidity. It is manifested as depression of the muscles at the thumping area, muscle ball, thumb adduction, or the palm cannot be separated immediately. The electromyogram shows the phenomenon of continuous myotonic discharge, which is exactly like the starting sound of a motorcycle.

3. Congenital Paramyotonia

It is a rare autosomal dominant hereditary disease. Onset in infancy. Prominent manifestations are muscle rigidity and general muscle weakness induced during cold, and symptoms immediately improve after entering a warm environment. It may gradually improve with age.

(1) Most patients develop onset at an early age.

(2) Prominent symptoms In the case that the degree of cold is not enough to affect the activities of normal people, muscle rigidity and weakness occur in the whole body. The symptoms worsen after continuous muscle contraction in the cold environment, and abnormal muscle rigidity is particularly obvious. The muscles of the face and both hands were significantly affected. Therefore, patients have difficulty opening their eyes after being cold, and have no difficulty in relaxing after muscle contraction in a warm environment. Only when they eat cold food after tapping the tongue muscle can induce muscle stiffness in the throat.

(3) Main signs Patients may have paroxysmal soft palsy, which is likely to induce muscle weakness after cold and exercise. Aggravation of myotonia may occur before the attack, which is called periodic paralysis of paramuscular tonicity. Myasthenia is distributed mainly in the proximal muscles, and seizures can last from minutes to days. Tonicity and weakness are exacerbated after exercise, which is the opposite of congenital myotonia, which is why Eulenburg calls it paramuscular rigidity. In some families, there is only weakness and no tonicity. This weakness is similar to primary periodic paralysis and can be induced by oral potassium. Physical examination: muscle hypertrophy can be seen.

(4) Electromyographic examination In the non-paralyzed period, myotonic discharge occurs. Electric paralysis is more common in the paralyzed period.

Congenital paramuscular rigidity test

1. Serum muscle enzyme test and serum electrolyte test are helpful for differential diagnosis.

2. Other auxiliary inspections

(1) Cold water induction test Immerse hands and forearms in cold water at 11 13 for several minutes to 40 minutes. It can help to diagnose myotonia and muscle weakness.

(2) EMG examination is helpful for differential diagnosis. Muscle biopsy can help with differential diagnosis.

Diagnosis of Congenital Paramyotonia

Congenital paramyotonia can be diagnosed based on the characteristics of myotonia and weakness after cold stimulation. When diagnosis is difficult, cold water induction test can be used to help diagnosis. It is also possible to take ice water or ice cubes and place them on one side of the patient for several minutes. If muscle tonicity symptoms appear, that is, if the tonic limbs are placed on warm water or hot water bottle for several minutes, the symptoms of myotonia will disappear. Established.

Differential diagnosis of congenital paramyotonia

Congenital muscle rigidity

In this disease, muscle hypertrophy is obvious, and the degree of muscle rigidity is heavier. You cannot relax immediately after exerting force, but this phenomenon can gradually disappear after repeated exertion. Paramuscular rigidity is aggravated after repeated activities or congenital muscle rigidity with muscle weakness, and rarely coexists with the symptoms of periodic paralysis. It is more likely to cause myotonic potential during the electromyography test. During the cold induction test, the myoelectric activity is recorded in the adductor or brachial abductor muscle. For congenital myotonia, a slight movement of the electrode can cause the release of myotonic potential. Duration It is longer than room temperature, and the results are the same after 4 to 5 consecutive shrinks. However, the rigidity of the paramuscular rigidity can not cause the release of myotonic potential. The amplitude of the motor unit potential is significantly reduced after continuous contraction. The electrical activity of the continuous contraction disappears rapidly and there is electrical rest.

2. Atrophic myotonia

The age of onset of this disease is relatively late, and muscle atrophy, endocrine and nutritional disorders can be identified.

3. Periodic paralysis

Because congenital paramuscular rigidity is often associated with paroxysmal soft palsy, it must be distinguished from it. It can be used as a potassium load test to induce weakness after the potassium is elevated and the blood potassium is elevated. If it has nothing to do with potassium, it is paramuscular rigidity. If there is muscle weakness after taking potassium and normal blood potassium is normal potassium periodic paralysis. If glucose insulin test can induce muscle weakness, it is hypokalemic periodic paralysis. Those with cold-induced muscle rigidity and muscle weakness are paramuscular rigidity.

Congenital Paramyotonia Treatment

Most patients with this disease gradually stabilize and improve after adulthood, and generally do not require special treatment. It is important to keep cold and warm in your life and avoid overwork. Pay attention to the possible dangers of children swimming in cold water; after strenuous activities, relax and rest first, which can prevent muscle rigidity and muscle weakness.