Periodic paralysis is a group of diseases with a genetic basis that belongs to the so-called canal diseases and affects the membrane-bound ion channels. Therapy consists mainly of dietary measures. The course of the disease is predominantly reported to be favorable.
What are periodic paralyses ?
Periodic paralyses are characterized by recurrent muscle paralysis. They are included in the group of diseases known as channel diseases and are associated with abnormalities with respect to blood potassium levels. The disease group affects the ion channels as protein complexes in the cell membrane of the muscles. Ion channels are responsible for the passage of ions and are thus crucial for muscle excitability. Periodic paralysis is a chronic progressive myopathy and develops over a long period of time. In addition to periodic hypokalemic paralysis, periodic hyperkalemic paralysis belongs to the group of periodic paralyses. Both diseases have a genetic basis. Also included in the canal diseases are paramyotonia congenita, congenital myotonia, and Andersen syndrome, which present with similar symptoms and show progressive muscle weakness as a common symptom. Periodic hypokalemic paralysis is clinically and genetically distinct from hyperkalemic paralysis.
Causes
Periodic paralysis has a genetic origin. Periodic hypokalemic paralysis shows a prevalence of one case per 100 000 population. The paralysis usually presents in adolescence or childhood and is subject to autosomal dominant inheritance. This form of periodic paralysis mainly affects males, who usually show a more severe course than the few affected females. A gene defect in the CACNA1S gene on chromosome 1 has been shown to trigger the disease. The gene product corresponds to a misconfigured subunit of the voltage-gated calcium channels in the tubule system of muscle cells. Hyperkalemic paralysis first manifests around the age of ten and is also subject to autosomal dominant inheritance. In this subgroup of periodic paralysis, a gene defect is present in the SCN4a gene on chromosome 17. The affected gene codes for sodium channels.
Symptoms, complaints, and signs
In hypokalemic paralysis, water and sodium retention occurs. Extracellularly, potassium deficiency is present. Because of the increased conductance of sodium across cell membranes, membrane potential and thus muscle excitation are impaired. The first symptoms appear before the age of 20 and initially occur at intervals of several months. The frequency and severity of paralysis episodes increases continuously from the onset of the disease. Only after midlife does the frequency decrease again and usually subsides in the 50th year of life. Paralysis occurs mainly at night or in the morning hours. The attacks are often preceded by mental excitement, carbohydrate-rich meals or physically strong stress. Accompanying symptoms are a feeling of fullness, sweating, paresthesia or weakness. In most cases, the respiratory muscles are not involved. If it is also affected, cardiac arrhythmias also occur. The paralytic symptoms last from several hours to several days. In periodic hyperkalemic paralysis, excessive potassium levels cause a shift in membrane electrolytes at the muscle cells. Potassium flows out of the muscle cells and sodium flows in. The membrane potential is disturbed by increased depolarization. The reduced excitability of the muscles causes paralysis. Paralysis is usually preceded by high potassium intake or heavy exercise. Compared with hypokalemic paralysis, the attacks are shorter but more frequent. A strong feeling of thirst occurs concomitantly. In addition to the legs, the mimic muscles are most commonly affected.
Diagnosis and course of the disease
In periodic hyperkalemic paralysis, the electrocardiogram is striking and characterized by the tent-like T-spikes, widened QRS complex, flattened P wave, and prolongation of PQ time seen in hyperkalemia. Muscle intrinsic reflexes are extinguished in this paralysis. The electromyogram shows reduced potentials and decreased amplitudes. Elevated serum potassium is present in the blood. In hypokalemic paralysis, muscle intrinsic reflexes are attenuated and muscle toni are reduced.In the EMG, the single potentials are low or short. In addition, there is a lamination of the activity pattern. Serum potassium levels are usually less than 2 mmol/l. A decrease in serum creatinine is conceivable. The same is true for an increase in sodium levels and lactic acid levels. The electrocardiogram shows ST segment depression and U waves in addition to a prolonged QT time. Muscle biopsy may show central and glycogen-filled vacuoles in the fibers in this type of periodic paralysis. The prognosis for both cases is considered favorable. Only rarely do walking impairments develop during the course. There is no correlation between the frequency or severity of seizures and final disease severity.
Complications
Periodic paralysis always presents complications that can be fatal in very severe cases. In the long term, the development of an inability to walk is also possible. During seizures, paralysis occurs suddenly and can lead to complete temporary paraplegia, so people at risk should not travel alone. This is because complete immobility can occur during a paralytic attack. However, the severity of paralysis and muscle weakness often varies among different attacks. In addition to harmless weak paralyses that appear only as sensory disturbances (pareses), complete paralysis of all four limbs may occur. This phenomenon is called tetraplegia and is considered a special form of paraplegia. During this severe paralysis, the affected person is completely dependent on outside help. The bladder and rectum may then also be paralyzed. As a rule, however, the respiratory muscles are not affected. In rare cases, however, this does occur. In such cases, this condition represents an extremely life-threatening complication. Only immediate ventilation can then save life. In a few cases, dangerous cardiac arrhythmias also occur during the paralytic attack, which require immediate medical attention. Various therapeutic measures and adherence to a certain diet should help to reduce the number of seizures, thus preventing long-term damage to the muscles of the extremities to the point of incapacity to walk.
When should you see a doctor?
Disorders of the musculoskeletal system, loss of physical performance, and sensory disturbances should be presented to a physician. If there are problems with locomotion, restrictions of movement possibilities as well as a stiffening of the musculature, a doctor is needed. The special feature of periodic paralysis is intermittent phases of freedom from symptoms. Although spontaneous healing occurs, a physician is needed. Since a recurrence of the paralysis occurs after a certain period of time, it is advisable that the affected person be adequately prepared for this situation. Sweating, vegetative disturbances, and irregularities of the heart rhythm should be examined and treated. Internal weakness or restlessness, sleep disturbances, and a diminished sense of well-being are signs of impaired health. A physician should be consulted so that a diagnosis can be made and a treatment plan established. If there is a feeling of fullness or inconsistencies of the digestive tract, the affected person needs medical care. If the risk of accident or injury increases, or if everyday demands can no longer be managed without assistance, a visit to the doctor is advised. In the case of psychological problems, a persistent experience of stress as well as anxiety, it is recommended to ask a doctor for support. In most cases, without medical treatment, the symptoms and emotional stress states increase. Characteristic of the condition is the increased feeling of thirst.
Treatment and therapy
In hypokalimemic paralysis, an attack can be interrupted therapeutically with high doses of potassium chloride. Administration is oral, and the ECG is monitored continuously during therapy. In the long term, attacks in this form of periodic paralysis can be prevented by low-carbohydrate and low-salt diets. In addition to these dietary measures, refraining from heavy muscular exertion can be goal-directed in seizure prevention. In addition, acetazolamide is often given for seizure prophylaxis with medication. Other medications may also be used, such as triamterene or lithium.During an attack, therapy for the hyperkalemic form consists primarily of intravenous infusion of calcium gluconate, glucose, or insulin. These methods cause the existing hyperkalemia to decrease. Dietary measures such as avoiding foods high in potassium are recommended for attack prophylaxis. A high-carbohydrate diet and adequate salt intake are also recommended for this form of periodic paralysis. Medication prophylaxis may include administration of acetazolamide and hydrochlorothiazide.
Outlook and prognosis
Periodic paralysis can be of two different types. The first variant is described as periodic hypokalemic paralysis. The second variant is periodic hyperkalemic paralysis. Both have in common that the periodic paralytic symptoms occur in close relation to the level of potassium in the blood. If deviations in potassium levels occur in these so-called “channel diseases,” paralysis occurs. However, these disappear again when the potassium level is raised or lowered. The paralyses affect the muscular system. The process that triggers muscular activity depends on complex mechanisms. These have not yet been sufficiently researched. However, potassium plays a supporting role in them. The extremities close to the trunk are most frequently affected by periodic paralysis caused by potassium deficiencies or overdoses. Treatment is with either potassium chloride or calcium gluconate. The hypokalemic periodic paralyses may well last for several days. The hyperkalemic paralyses, on the other hand, last only a few minutes. However, they can also affect the facial and pharyngeal muscles. The periodic paralyses reduce the quality of life of those affected quite considerably. When potassium levels are balanced, sufferers have no noticeable symptoms. However, after many years of the disease, many of the affected patients develop chronic progressive myopathy due to their periodic paralysis. As the muscle disease becomes chronic, the prognosis worsens.
Prevention
Periodic paralysis cannot be prevented to date because it is a genetic disorder and not all causal relationships of the disease have been elucidated by a long shot.
Follow-up
Some diseases subside after therapy. Follow-up care then aims to prevent the recurrence of symptoms. In contrast, periodic paralysis is a genetic defect. It is not curable. Medical measures and aftercare cover the entire life of the patient. If necessary, those affected can reduce their suffering through self-help measures. Suitable measures include changing their diet and adapting their home furnishings to meet certain needs arising from the disease. A doctor usually provides the relevant information as part of the initial diagnosis. The actual aftercare for periodic paralysis aims at everyday support and permanent treatment. Physician and patient agree on an individual rhythm for presentations. In addition to a detailed conversation about the current state of health, a physical examination also takes place. Some doctors also use an electromyogram for monitoring purposes. Aftercare consists of drug treatment. In particular, the social environment should be involved in this. This is because the periodic paralysis leads to temporary helplessness and inability to move. As patients get older, the symptoms occur more frequently. Aftercare can then often only be implemented by therapeutic specialists. Placement in an assisted living unit usually becomes inevitable.
What you can do yourself
People with periodic paralysis have a genetic defect that they cannot correct despite their best efforts. Therefore, there are measures to be taken that must be applied throughout life. Medical care and regular check-ups are necessary to adequately monitor the health of the affected person. The therapy worked out with the doctor should be followed and adhered to so that no further irregularities occur. If the patient has a potassium deficiency, the affected person can additionally change his diet. Beet, lamb’s lettuce, chard, kohlrabi or artichokes are foods rich in potassium.Meals should be prepared with fresh and untreated vegetables, so that as many vitamins and nutrients as possible can reach the organism. In order to minimize the general risk of accidents caused by periodic paralysis, the patient’s environment should be adapted to the symptoms of the disease. The home furnishings should be optimized so that the patient does not suffer any injuries if the muscular symptoms occur. Since paralysis symptoms last for several hours or days, both affected persons and relatives should be prepared and create a working schedule for taking immediate measures. In many cases, patients develop a heightened awareness of their own body’s processes. They recognize warning signals in good time and can therefore take preventive action. It can also be helpful to exchange ideas with other sufferers.