Hereditary neuropathies with tendency to pressure paralysis are hereditary neurological disorders that belong to the group of neuropathies. The slightest pressure on the nerves leads to paralysis symptoms, which, however, completely or partially regress in the unstressed state. The condition is not life-threatening.
What is hereditary neuropathy with a tendency to pressure paralysis?
Hereditary neuropathy with a tendency to pressure paralysis is characterized by increased sensitivity of the nerves to pressure. Even low levels of stress caused by physical activity can lead to paralysis. These disorders are a collective term for neurological disorders whose main feature is the restriction of nerve conduction when pressure is applied. Hereditary neuropathy with a tendency to pressure paralysis is abbreviated as HNPP. HNPP in turn is derived from the English term “Hereditary Neuropathy with liability to Pressure Palsies”. Furthermore, the disease is also called tomacular neuropathy, which is characterized by the sausage-like swelling of the myelin sheaths. HNPP is a hereditary disease. Its prevalence is reported to be 1/50,000 to 1/20,000. HNPP is particularly common in Finland. Since hereditary neuropathies with a tendency to pressure paralysis have a genetic basis, they cannot be cured. However, they can be treated well. The life expectancy of affected individuals is not limited. A characteristic feature of the disease is demyelination of the medullary sheaths, which swell as a result. The myelin sheaths surround the nerve cells or their axons and provide their electrical insulation. In HNPP, however, the myelin sheaths are destroyed. Therefore, they can no longer perform their protective function adequately. The result is a reduction in nerve conduction velocity. The reduced conductivity causes the failure of important reflexes and the appearance of numbness, insensitivity and weakness. Mainly when pressure is applied to the nerves, their lack of electrical insulation becomes noticeable.
Causes
The cause of demyelination of myelin sheaths is a defectively assembled myeloprotein PMP22. This protein is encoded by a gene on chromosome 17. The same gene is also responsible for the development of hereditary motor-sensitive neuropathy in corresponding defects. However, many different mutations of the PM22 gene can also lead to hereditary neuropathy with a tendency to pressure paralysis. Most of these are deletions (truncations). However, point mutations can also lead to PMP22 malformation. Approximately 80 percent of HNPP is due to deletions of the PMP22 gene. The remaining 20 percent are caused by point mutations of the same gene and mutations of other genes. These include the MPZ and connexin 32 genes. The basis of pressure paralysis represents the reduced ability of demyelinated myelin sheaths to insulate nerve cells. When the nerves are compressed, electrical short circuits occur, limiting nerve conduction.
Symptoms, complaints, and signs
The condition usually first appears in the second or third decade of life. In rare cases, however, it can occur in childhood. However, there are also symptom-free patients who are never diagnosed with HNPP despite a genetic predisposition. The most common symptoms are sudden loss of sensation and muscle weakness along the course of individual nerves. There is no pain associated with this. This loss of sensitivity of the particular nerve is due to localized pressure. The pressure is caused by repeated movement or stretching at the affected area. The symptoms often occur in the fibula, elbow, wrist or foot. Unlike polyneuropathies, these are mononeuropathies because only single nerves are affected. Such symptoms as numbness and weakness of hands, loss of sensitivity in fingers and hands, weakness in arms or drop feet are observed. When the pressure load stops, in 50 percent of cases the symptoms resolve within days to months. In other cases, symptoms improve, with residual symptoms remaining. However, with repeated pressure loading, the symptoms reappear.
Diagnosis
The suspected diagnosis of HNPP results from the repeated occurrence of mononeuropathies and a familial clustering of these disorders. Furthermore, electrophysiologic studies and biopsies of nerve tissue are performed to determine focal thickening of the myelin sheaths. Genetic testing can definitively establish the diagnosis.
Complications
This disease can significantly limit the daily life and quality of life of the affected person. In this case, even very simple and light applications of pressure to certain regions in the body result in symptoms of paralysis. Although these regress, the affected person is not infrequently dependent on the help of other people in his or her everyday life. Life expectancy is not reduced by this disease. However, it is not uncommon for patients to suffer from psychological upsets and depression, so that in some cases suicidal thoughts may occur. Sensitivity disorders and muscle weakness occur. In general, the patient’s ability to cope with stress decreases enormously. However, pain does not occur. The paralyses lead to movement restrictions, so that the patient may be dependent on a wheelchair. The paralysis does regress, but this can take up to a month. A causal treatment of this disease is not possible. The symptoms can also only be treated to a limited extent, with various therapies being used in particular. No complications occur in this process. The patient’s relatives may also suffer from psychological symptoms and therefore not infrequently require psychological care.
When should one go to the doctor?
Although this disease is not life-threatening, in this case a doctor should still be consulted at the first signs and symptoms. This can prevent further complications and discomfort, since there is usually no self-healing. A doctor should be consulted if there are disturbances in sensitivity or discomfort in the muscles and general muscle weakness. These complaints can occur in different parts of the body. Similarly, the disturbance of sensitivity may occur due to pressure and may not be present without pressure. Furthermore, weak or numb hands and feet also indicate the disease and should always be examined by a doctor if the symptoms do not disappear on their own within a short time. As a rule, in the case of neuropathy with a tendency to pressure paralysis, a general practitioner or, in the case of children, a pediatrician can be consulted in the first instance. Further treatment is then provided by various specialists, and the exact treatment also depends on the cause of neuropathy with tendency to pressure paralysis. However, the patient’s life expectancy is not reduced by the disease.
Treatment and therapy
There is no causal therapy for hereditary neuropathies with a tendency to pressure paralysis because the disease is genetic. Orthopedic aids should be used when walking ability is limited by increasing paresis. These include orthopedic shoes, shoe lifter orthoses, knee orthoses, walking sticks, rollators and, if necessary, a wheelchair. Surgical corrections are also performed for major deformities of the feet. Physical therapy and occupational therapy are also used regularly. In some patients, however, no treatment at all is necessary because the complaints disappear on their own after some time. A prerequisite for this, however, is the avoidance of mechanical stress.
Outlook and prognosis
Hereditary neuropathy with a tendency to pressure paralysis cannot be cured. It is a genetically determined disease. However, the prognosis of the disease is usually good. In half of the cases, there is complete regression of symptoms. In these patients, therapy is not necessary. In the other 50 percent of patients, there is an incomplete regression of symptoms. Normally, the residual symptoms are mild and do not lead to disability. However, in some patients, the ability to walk is later limited. Orthopedic aids may then become necessary. The limitations are very variable, however, so that the use of these aids also varies. Among other things, foot lifter orthoses, knee orthoses, orthopedic shoes, walking sticks, rollators and sometimes even wheelchairs are used.If the hands are affected, aids for writing and eating may also be required. In cases of severe foot deformities, surgical correction is sometimes sought. Physiotherapy and occupational therapy are also considered for certain limitations, such as paralysis in the hands. However, it is up to the patient to avoid trigger situations for pressure lesions. There are sufferers who remain completely symptom-free throughout their lives. The use of neuropathy-inducing drugs such as high-dose penicillin or vitamin B6, as well as lithium, gold, vitamin A, and many others, must definitely be considered on an individual basis.
Prevention
If there is a family history of HNPP, human genetic counseling may be sought. The disease is usually inherited in an autosomal dominant manner. Individuals who are already affected by HNPP can prevent the onset of the typical symptoms by avoiding pressure loads. This includes, among other things, sitting for long periods with the legs crossed, repetitive movements of the wrists, or resting the elbows. Rapid weight loss is also counterproductive. Furthermore, many drugs that have a reinforcing effect on polyneuropathies should be critically questioned. In particular, the use of vincristine should be avoided.
Follow-up
Following therapy for hereditary neuropathy with a tendency to pressure paralysis, it is helpful to use protective pads for the affected joints. Patients receive appropriate information from their physician on how to protect the nerves well in the future. Excessive mechanical stress should be avoided if possible. If the knees are affected, sufferers should not constantly cross their legs for long periods of time. If there are difficulties with the elbows and wrists, it helps to avoid repetitive movements or frequent propping. Rapid weight loss can also have a negative effect on physical well-being. In consultation with the physician, patients learn which medications they may need to stop taking. Vincristine, for example, is taboo. As part of follow-up care and as a supportive treatment, reducing overly vigorous movements and excessive activities plays a major role. In addition, bandages and padded elements are available that reduce pressure on the joints. This helps to prevent the overuse from recurring. In addition to protection against repeated damage, there is also protection of the nerves. This gives the myelin structure a chance to regenerate successfully.
Here’s what you can do yourself
Hereditary neuropathy with a tendency to pressure paralysis is always genetic and therefore cannot be treated causally. Patients must learn to live with the complaints and symptoms in the long term. This can be achieved on the one hand by talking to friends and relatives, but also by attending a self-help group. The doctor can help patients to accept the disease in the long term. Accompanying therapy, measures must also be taken to alleviate the discomfort caused by the deformities. Physiotherapy and occupational therapy are among the most important measures – both can be supported by the sufferers through moderate sport, physiotherapy and also yoga. In some patients, the symptoms disappear all by themselves. In this case, no further treatment is necessary. However, patients should keep a diary of their symptoms and consult closely with their physician. If symptoms suddenly reappear, this must be clarified immediately. Acute pain can be relieved by natural painkillers. Which preparations are suitable depends on the type of neuropathy and must always be decided by a doctor or alternative practitioner.
