Paramyotonia congenita belongs to the group of myotonia, which are characterized by long-lasting states of tension in the muscles. It is a genetic disease in which the functioning of the sodium channels is disturbed. The symptoms only appear when the muscles cool down or during prolonged physical activity and are hardly or not at all noticeable when it is warm.
What is paramyotonia congenita?
Paramyotonia congenita is a disease of muscle function that manifests itself in long-lasting tension after muscle contraction or exposure to cold. This disease was first described by the neurologist Albert Eulenberg, who lived from 1840 to 1917. For this reason, Paramyotonia congenita is also known as Eulenberg disease. See ezhoushan for What does HI Stand for.
In contrast to the other myotonia such as myotonia congenita Thomsen and myotonia congenita Becker, it is not a matter of chloride channel myotonia but of sodium channel myotonia. This is where sodium ion transport is disrupted. Sodium ions flow into the cell to generate the action potential. Normally, after the muscle contraction, these are transported out of the cell immediately until a membrane resting potential is formed.
In the case of paramyotonia congenita, this process is delayed and can last several hours. Mainly when exposed to cold or after prolonged muscle stress, the tension in the muscles can only be broken down poorly. In contrast to the chloride channel myotonia, the musculature stiffens even more during movement. The voluntary muscles are particularly affected by this disease.
Causes
Point mutations on the gene SCN4A, which is located on chromosome 17, were identified as the cause of Paramyotonia congenita. As a result of these mutations, the function of the sodium channel in the muscle cells is severely impaired. Sodium ions flow into the cell to develop the action potential. However, in the resting potential state, the sodium ion concentration is greater outside the cell than inside.
This means that the concentration of potassium ions in the cell is higher than the concentration of sodium ions. The resting potential is actively established by the ion pump function of the sodium channel. If the process of restoring the resting potential from the action potential is disrupted, the muscles will be in a state of tension that will last for a long time. This is referred to as myotonia because the muscle tone remains elevated for a long time.
In the case of Paramyotonia congenita, the influx of sodium ions into the cell is promoted, particularly when exposed to cold and muscle contraction. Two reasons for the development of a particularly high action potential are discussed. Some of the diseases are probably due to the fact that the sodium channels are no longer closed. Another part of the sodium channel myotonia is based on the delayed closing of the sodium channels.
With further exposure to cold or continued physical activity, the action potential continues to build up. The resting potential is only slowly built up again when the body is warm and at rest. However, this is in contrast to chloride ion channel myotonia, in which the resting potential is built up with physical activity.
Symptoms, Ailments & Signs
Paramyotonia congenita is present from birth, with symptoms remaining unchanged throughout life. The eyelid muscles, eye muscles, face, neck and lower and upper extremities are particularly affected. For example, a closed eyelid cannot be opened for hours after exposure to cold.
A cold effect already exists when a damp and cool washcloth is put on. In addition, the patient’s face stiffens like a mask when exposed to cold. At the same time, movement disabilities occur, with the fingers exhibiting a painless flexed position. Paradoxically, stiffness increases with repetitive movement and exposure to cold.
After prolonged exercise and exposure to cold, muscle weakness occurs . Some patients also suffer from periodic hyperkalemic paralysis from puberty onwards. When it is warm, there are usually no or only minor symptoms.
Diagnosis & course of disease
Myotonia congenita can already be diagnosed by the symptoms that occur. The differential diagnosis between the individual forms of myotonia is also simple. While the chloride ion channel myotonia Myotonia congenita Thomsen and Myotonia congenita Becker have almost identical symptoms, they can be clearly distinguished from Paramyotonia congenita.
A simple examination method is the application of cold compresses to induce lid myotonia. After that, it is impossible for those affected to open their eyelids for a long time. At the same time, the patients see double images, which should always be asked about in the anamnesis. Increasing stiffness with repeated movement also points to sodium channel myotonia.
The increased levels of creatine kinase that are typical of muscle diseases are found in the blood. However, since these values also occur in other diseases, they are irrelevant for the diagnosis. However, a genetic test can fully confirm the diagnosis.
Complications
With proper treatment of paramyotonia congenita, there are no complications. Life expectancy is not reduced. However, the major challenge, particularly in winter, is to prevent the joints from cooling down. In summer, the joints stiffen, among other things, when going for a swim. This leads to stiffening of the joints and general physical weakness. The same applies to prolonged physical work.
However, cooling cannot be completely avoided. That would only be achievable if those affected were to stay in rooms with a higher temperature all the time. Some patients also suffer psychologically from the fact that they can only carry out many leisure activities to a limited extent. In some cases, this can even lead to mental illness and depression. As a rule, no drug treatment is necessary for paramyotonia congenita.
In most cases, simply avoiding cooling of the joints is enough to prevent stiffening. In a few cases, however, the symptoms can be so severe that treatment with the drug mexiletine is recommended. However, treatment with this drug, which is actually used for cardiac arrhythmias, should only be done in exceptional cases, as it can lead to various side effects. Dizziness, mood swings, visual disturbances or nausea are often noticeable when taking the drug. In very rare cases, thrombocytopenia with an increased tendency to bleed can also occur.
When should you go to the doctor?
Disorders of the muscular system are a sign of a health impairment. They should be clarified by a doctor so that a treatment and therapy plan can be drawn up. The first signs appear in the first days or months of life. If muscle stiffness occurs after exposure to cold or intense physical activity, it is advisable to consult a doctor. If the solidification persists for several hours, this is an indication of paramyotonia congenita. If the joints move, the stiffness increases even further.
The symptoms of the genetic disease remain constant for life without medical care and do not increase in intensity. Disturbances in the movement sequences, a fixed flexed position of the joints as well as paralysis should be examined by a doctor. A symptom-free condition under warm environmental conditions is characteristic of the disease. If there are irritations in coping with everyday life or if sporting activities and professional activities cannot be carried out as desired, a doctor is needed.
An increased risk of falling or accidents, unsteady gait and fear should be discussed with a doctor. If emotional problems or mental disorders appear at the same time due to the physical limitations, the symptoms must be clarified. If the affected person complains about changes in vision during the muscle stiffness, there is a need for action. Double vision is often documented during this phase.
Treatment & Therapy
A causal treatment of paramyotonia congenita is not possible because it is a genetic disease. In most cases, however, no treatment is necessary if the effects of cold and prolonged physical activity are avoided. There is no reliable data on drug treatment.
However, to resolve a long-lasting stiffness, the use of the drug mexiletine is recommended. Since this drug is a heart drug, attention should be paid to any side effects that may occur.
Outlook & Forecast
The disease called Paramyotonia congenita is characterized by overexcitability of the skeletal muscles. This leads to involuntary muscle contractions. However, life expectancy is not limited. The prognosis for Paramyotonia congenita is therefore positive. The relatively rare hereditary disease is inherited in an autosomal dominant manner.
The muscles of those affected involuntarily cramp. It can only be relaxed with difficulty. Tension and relaxation when climbing stairs are difficult. People affected by Paramyotonia congenita experience problems, especially when exposed to cold or after sitting for a long time. You have difficulty walking, grasping, or balancing. Due to the involuntary muscular cramps that occur, they are more at risk of falling than others.
Despite the paramyotonia congenita, there is no muscle weakness. Those affected may well have an athletic physique. The constantly contracting muscles create a kind of training effect. The symptoms are improved by targeted training. The aim of this is to eliminate the relaxation disorder and to weaken its effect. Most of the time this works quite well. The treating physicians therefore rarely consider short-term drug therapy.
A cure for paramyotonia congenita is currently not possible. The disease is already established in childhood. It remains for life. Those affected may have an increased risk of respiratory diseases or respiratory paralysis due to myopathies if they require intensive care treatment.
Prevention
Prevention of Paramyotonia congenita is not possible due to its genetic cause. However, in the case of an existing disease, it is possible to achieve extensive freedom from symptoms if a few rules are observed. It is important to avoid the effects of cold, swimming in cool water and prolonged physical activity. However, since the connection between these influences and the symptoms is obvious, those affected will essentially follow these rules.
Aftercare
In many cases, those affected with Paramyotonia congenita only have limited follow-up care available. First and foremost, a quick and, above all, early diagnosis should be made so that there are no further complications or other complaints for the person concerned. The sooner a doctor is consulted, the better the further course of the disease, so that the person concerned should ideally consult a doctor as soon as the first signs and symptoms of the disease appear.
Most patients with paramyotonia congenita are dependent on physiotherapy and physiotherapy. Many of the exercises from these therapies can also be carried out at home in order to increase the mobility of the body again. In many cases, paramyotonia congenita is also treated by taking various medications.
The person concerned should always be on a regular and prescribed intake in order to properly alleviate the symptoms. If anything is unclear or if you have any questions, always consult a doctor first. Even with severe side effects, a doctor should be consulted first. Paramyotonia congenita may also reduce the life expectancy of those affected.
You can do that yourself
Patients suffering from paramyotonia congenita are very sensitive to cold. Therefore, in order to avoid myotonic reactions, they must keep their muscles warm. It is therefore important to avoid the cold, especially in the winter months. Warm clothing and heated rooms are essential in the cold season. There are also some challenges in summer, because the characteristic muscle tension also occurs in a cold bathing lake. In everyday life, even cold tap water on the face can lead to paralysis.
Depending on how severe the symptoms are, the doctor may recommend drug treatment. The correct dosage is important here. Drugs alleviate the problem, but they also have side effects. When those affected know the cause of their sudden muscle stiffness, they learn to deal with it. Those affected warm the washcloth before use and wait until the water is warm before holding their hands under the open tap.
Muscle tension can be exacerbated by physical activity. Therefore, too much exercise is not recommended for patients. If you have a stiffening, it helps to act quickly and warm up the affected body parts.
