Multifocal motor neuropathy (MMN) is a slowly progressive disease of motor nerves that leads to various deficits. Sensory and autonomic nerves are not involved. An autoimmune process is assumed to be the cause.
What is multifocal motor neuropathy?
Multifocal motor neuropathy is characterized by the slow loss of motor nerves. During investigations, antibodies against the ganglioside GM1 are detected. It is therefore an autoimmune disease. The neuropathy is assigned to the Guillain-Barré syndrome. Guillain-Barré syndrome is a collective term for autoimmune diseases of the nervous system that impair muscle function. See foodezine for Everything about Hyperinsulinism.
Multifocal motor neuropathy is characterized by dysfunction of the ulnar and median nerves. It is a very rare condition with a prevalence of 1 to 2 per 100,000 people. Neuropathy usually occurs for the first time between the ages of 30 and 50. Men are two to three times more likely to be affected by multifocal motor neuropathy than women. The symptoms also appear much earlier in men.
MMN has similar symptoms to ALS and must always be differentiated from it in the differential diagnosis. In contrast to ALS, however, there are good treatment options that can stop and even reverse the progression of the disease.
The possible cause of multifocal motor neuropathy is an autoimmune process in which autoantibodies are formed against the ganglioside GM1. As sphingolipids, gangliosides are part of cell membranes. They play a role in making cell contacts. They are also responsible for the recognition of nerve cells by the immune system.
If these phospholipids fail, the nerve signals are only transmitted weakly. Nerve failures and paresis can occur. The autoantibodies bind to the gangliosides and thereby switch them off. Therefore, the transmission of excitation is locally inhibited and muscle performance is impaired. In the case of multifocal motor neuropathy, the ulnar nerve and the median nerve are affected.
Symptoms, Ailments and Signs
MMN is characterized by the occurrence of asymmetric distal paresis of the upper extremities, which, however, can only lead to muscle atrophy after a long time. Sometimes there are no atrophies at all, or they are only weakly developed. As already mentioned, the ulnar and median nerves are mainly affected.
The ulnar nerve is a motor nerve of the arm. He is responsible for the forearm muscles and hands. The median nerve also innervates muscles of the forearm and hands or fingers. In rare cases, involvement of the cranial nerves is also possible. Muscle cramps and involuntary movements of small muscle groups (fasciculations) also occur. In very rare cases, respiratory paralysis is also possible due to the involvement of the phrenic nerves.
The muscle reflexes decrease in the course of the disease. However, there are hardly any sensory disturbances. However, respiratory problems can occur if the phrenic nerve is involved. However, this only occurs in about one percent of cases. Sometimes the lower extremities are also affected by multifocal motor neuropathy. However, this is only very rarely the case.
Especially at the beginning of the disease, the discrepancy between the often significant paresis and the seemingly insignificant muscle atrophy is striking. However, as the disease progresses, the atrophies become more apparent due to the gradual destruction of the myelin sheaths.
Diagnosis and course of the disease
Multifocal motor neuropathy is characterized by almost identical symptoms to amyotrophic lateral sclerosis (ALS), making it difficult to tell the two disorders apart. The same is also true for spinal muscular atrophy and nerve compression syndrome. A differential diagnosis must be performed to rule out these disorders.
Blood analyses, cerebrospinal fluid tests and imaging methods do not lead to any results. A typical indication of multifocal motor neuropathy is the occurrence of nerve conduction blocks in motor electroneurography. The sum of the cumulative muscle potentials of the proximal nerve stimulations is reduced by well over 50 percent compared to the cumulative muscle potentials of the distal nerve stimulations.
An additional electromyography performed shows a reduction in the proportion of nerves in the skeletal muscles. The GM1 antibody can also be determined. If the titer of this autoantibody is increased, there is further evidence of MMN.
In most cases, those affected suffer from various motor deficits as a result of this disease. This usually makes the patient’s everyday life much more difficult and the quality of life is just as severely reduced and restricted. The patients primarily suffer from severe muscle pain and can no longer move them voluntarily.
Convulsions and epileptic seizures, which are associated with severe pain, can also occur. In the worst case, this also paralyzes breathing, so that the affected person is undersupplied with air and possibly also loses consciousness. Injury may occur in the event of a fall.
Patients also suffer from sensory disturbances or paralysis all over the body as a result of the disease. These can also significantly restrict everyday life, so that those affected need the help of other people in their lives. Self-healing does not usually occur with this disease.
Treatment of this disease can be carried out with the help of medication. However, those affected are usually dependent on various therapies that maintain the functions of the muscles. Special complications usually do not arise.
When should you go to the doctor?
Multifocal motor neuropathy should be evaluated by a doctor if classic symptoms such as muscle spasms or involuntary movements occur. Sensory disturbances and respiratory problems indicate an advanced disease that must be diagnosed and treated immediately. The disease can be recognized at the beginning by the irregular alternation between mild muscle cramps and severe paresis. Ideally, people who notice the symptoms mentioned should go straight to their family doctor.
The doctor can make an initial suspected diagnosis and, if necessary, consult a specialist. In the event of motor failures, the emergency doctor must be called. The same applies to cramps, epileptic seizures and respiratory paralysis. If a fall occurs due to a seizure, first aid must also be provided. The victim is then treated in the hospital. The actual treatment is provided by a neurologist or other specialist in internal diseases. Comprehensive physiotherapy is also part of the treatment, in the context of which attempts are made to preserve the mobility of the limbs.
Treatment & Therapy
In contrast to amyotrophic lateral sclerosis, multifocal motor neuropathy can be treated well. Therefore, a differential diagnosis to distinguish between the two diseases is very important. Some patients with a previous diagnosis of ALS are diagnosed with MMN on closer examination. MMN can be treated well with immunoglobulins.
It was found that 40 to 60 percent of all patients diagnosed with MMN could be prevented from progressing with this treatment. The earlier the therapy was started, the better the prognosis. The therapy is usually carried out for six years. During this time, the dose of immunoglobulins is increased from initially twelve to seventeen grams per week.
There are no known side effects of this treatment. However, since irreversible damage to the nerve cells occurs in the course of the disease, the success of the therapy depends on the time at which therapy begins.
Outlook & Forecast
The outlook for multifocal motor neuropathy is generally poor. Many scientists emphasize that the administration of immunoglobulins prevents the disease from progressing. However, according to statistical studies, this helps a maximum of sixty percent of those affected. The others suffer from permanent muscle weakness and have to accept limitations in their lives. Another disadvantage is that the long-term administration of immunoglobulins usually results in ineffectiveness. Then permanent deficits form. The risk of developing multifocal motor neuropathy is greatest between the ages of 30 and 50. Statistically, men are particularly vulnerable.
In the best case, the symptoms recede. Doctors hope that the treatment will be successful if the symptoms are not too advanced. Starting therapy in the early stages can therefore be regarded as ideal. Multifocal motor neuropathy mainly affects the extremities. Rarely, the disease spreads to the cranial and phrenic nerves, resulting in further complications. Disabilities and weaknesses arise in particular and have been proven when the multifocal motor neuropathy has remained untreated for a long time.
It is not known what options there are for preventing multifocal motor neuropathy because the cause of this disease is unclear. It is an autoimmune disease. When the first symptoms appear, however, treatment should begin quickly, because the success of the therapy largely depends on the time at which therapy begins.
Follow-up care for multifocal motor neuropathy depends on the course of the disease. If treatment with immunoglobulins is started early, there is even a good chance of a complete cure in some cases. If therapy is started later, however, the prospects for a complete remission of the disease worsen.
Then it is often only possible to try to counteract a worsening of the symptoms. In any case, it is a lengthy therapy, which must be accompanied by intensive aftercare measures. Treatment with immunoglobulins is usually repeated every four to eight months. Afterwards, detailed examinations should always be carried out in order to document the progress of the therapy.
In about 40 to 60 percent of cases, the administration of immunoglobulins at least halts the progression of the disease. However, if the follow-up examinations show a resistance to therapy, an attempt can be made to bring about an improvement in the symptoms with the help of other active substances such as cyclophosphamide in combination with immunoglobulins.
Especially in the case of an unfavorable prognosis with increasing inability to move, psychological therapy often has to be integrated into the aftercare measures, because despite a normal life expectancy, the quality of life is considerably restricted. At the same time, aftercare also includes the procurement of suitable aids, which become necessary in the event of significant impairment of the mobility of the lower extremities.
You can do that yourself
If you start physical activity immediately after the diagnosis has been made, you cannot influence the course of the disease, but it will help you to maintain muscle strength and exercise. If necessary, it is important to use joint supports or bandages to prevent overloading certain muscle groups.
If problems arise at work due to illness, the integration specialist office offers comprehensive help. The employees advise and assist in communicating with the employer and applying for aids to maintain the workforce.
When the disease is very advanced, it is hardly possible to live independently without outside help. In this case, it is important to take care of the application for a care level at an early stage, on the one hand to financially support the caring relatives or on the other hand to receive external part-time care. Each patient must decide together with his family which path is the right one. It is often less psychologically stressful to seek outside help. You should not shy away from going to a therapist either, since a mental imbalance can also lead to physical problems.
If there is a complete need for help in all situations, external care can also be requested around the clock. With this support, it is sometimes even possible for those affected to go back to work and participate in social life.