Spinal muscular atrophy (SMA) is a group of disorders characterized by muscle wasting. SMA is caused by the death of motor nerve cells in the spinal cord.
What is spinal muscular atrophy?
The term progressive spinal muscular atrophy was coined by neurologist John Hoffmann in Heidelberg in 1893. Spinal muscular atrophies are diseases that result from the loss of alpha-motoneurons. Alpha-motoneurons are nerve cells of the central nervous system (CNS). They are located in the brainstem and in the anterior horn of the spinal cord and are responsible for the innervation of skeletal muscle fibers and thus also for muscle contraction. The decline of motoneurons in SMA is progressive. Due to the atrophy, impulses from the nervous system can no longer be transmitted to the muscles. As a result, paralysis occurs with muscle wasting and decreased muscle tension.
Causes
Spinal muscular atrophy is a hereditary disease. Like most neuromuscular diseases, spinal muscular atrophy is rare. The most common form is the infantile form. Here, one child per 25,000 births develops the disease. In the juvenile form, only one child per 75,000 births is affected. The acute infantile form of SMA even begins before birth in the womb. In the juvenile form, symptoms do not begin until childhood or adolescence.
Symptoms, complaints, and signs
Muscle atrophy and weakness occur due to the demise of motor nerve cells. Normally, muscles contract when activated by the nerves that supply them. The muscle contracts, it becomes shorter and tightens. This allows the intended movement to be performed. Muscles that are no longer innervated due to SMA can also no longer contract. The muscle can therefore no longer be used. It becomes more and more lanky due to immobilization. If a larger number of muscle fibers are affected by the paralysis, a decrease in substance of the complete muscle can be observed. In contrast to muscular dystrophy, the muscle itself is not affected. This is why this muscle atrophy is also referred to as muscular atrophy. In the course of the disease, the strength and endurance of the muscle decrease. Affected patients can no longer perform certain movements or can only do so for very short periods of time. The muscles fatigue much more quickly than in healthy people. The acute infantile form of SMA is already noticeable in the womb. The children move very little in the womb. At birth, decreased muscle tone is evident. Spontaneous movements rarely occur. The children cannot keep their heads free and cannot sit freely. Within the first two to three years of life, affected children die from respiratory failure. In the intermediate form, the first symptoms appear in the first months-or years-of life. The children can no longer walk or stand. Spinal curvatures and deformities of the chest occur. Most patients do not reach the age of 20. The juvenile form of progressive spinal muscular atrophy begins in late childhood or adolescence. The first muscle weaknesses usually involve the muscles of the pelvic girdle. Clumsy stair climbing is one of the first symptoms. As it progresses, however, the muscle weakness spreads to the rest of the musculature. Occasionally, a very strong calf can be observed in affected patients. This contains increased fat and connective tissue. Adult spinal muscular atrophies begin in adulthood and progress much more slowly than the other forms of SMA. They often begin with weakness and wasting of the hand muscles. Weakness of the foot muscles may also be the first indication of adult SMA. If the cranial nerves are affected by the disease, there is additional difficulty swallowing, chewing or speaking. When the cranial nerves are involved, the condition is usually spinobulbar muscular atrophy type Kennedy (SBMA) or progressive bulbar paralysis.
Diagnosis and disease course
In making the diagnosis, the first step is to consider the patient’s detailed history, including a description of the functional disorder. Then a detailed physical and neurologic examination is performed. This includes procedures such as electroneurography or electromyography. Electroneurography measures the nerve conduction velocity.Electromyography involves the measurement of muscle currents. With the help of these two procedures, spinal muscular atrophy can be differentiated from multifocal motor neuropathy. In addition, procedures such as needle electromyography, motor electroneurography, or sensory electroneurography can be performed. In the laboratory, parameters such as blood sedimentation rate, creatine kinase, vitamin B12, vitamin D, thyroid hormones or parathyroid hormone are determined. An examination of the cerebrospinal fluid can also provide information. X-rays of the cervical spine or slice images of the brain and cervical spine may also need to be obtained. Muscle biopsy or nerve biopsy provide further clues.
Complications
Primarily, those affected by this disease suffer from severe muscle weakness and atrophy. This results in significant limitations in everyday life and thus complications. Ordinary activities are no longer possible for the affected person without further ado, so that in many cases the patients are dependent on the help of other people. As a result, many affected persons also suffer from psychological complaints or depression and require psychological treatment. As a rule, self-healing does not occur with this disease and the patient’s muscle strength continues to decrease as a result of the disease. Breathing is also significantly weakened as a result, so that those affected suffer from breathing difficulties and thus possibly from dizziness or loss of consciousness. Furthermore, there is a curvature of the spine and severe deformities in the back. These also have a very negative effect on the patient’s quality of life. In most cases, the life expectancy of the affected person is limited to 20 years. Since a causal treatment of the disease is not possible, only the symptoms can be limited. No particular complications occur. However, a completely positive course of the disease does not occur.
When should one go to the doctor?
In any case, direct treatment by a doctor is necessary for this disease. As a rule, there can be no self-healing, so the patient is always dependent on early examination and treatment. The earlier the disease is detected and treated, the better the further course of the disease usually is. A doctor should be consulted if the patient suffers from very severe muscle weakness. In most cases, the patient can no longer perform heavy activities and often feels tired and fatigued. Likewise, respiratory weakness can often be an indication of muscle atrophy and should also be examined by a physician. Some affected persons also suffer from a curvature of the spine and also from a deformed chest. If these symptoms occur, a doctor should be consulted in any case. As a rule, muscle atrophy can be detected by a general practitioner. Special complications do not occur during treatment. The life expectancy is also not changed by this disease. However, whether a complete cure is possible cannot be universally predicted.
Treatment and therapy
The goal of therapy for SMA is to improve muscle function. Affected patients should be able to maintain their independence and self-care for as long as possible. Treatment is usually provided by a team of physicians, physical therapists, speech therapists, occupational therapists, and social workers. Physical therapy, occupational therapy and speech therapy are performed on an outpatient basis and serve to maintain the remaining abilities. The course of the disease can be positively influenced by inpatient rehabilitation measures. Since the main cause of clinical problems is muscle weakness, targeted training of the muscles can be helpful. In individual cases, orthoses can improve function. According to scientists at Freiburg University Hospital, children with spinal muscular atrophy benefit in maintaining their motor skills by starting therapy early with nusinersen (Spinraza).
Prevention
Because spinal muscular atrophy is inherited, prevention is not possible.
Follow-up care
For spinal muscular atrophy follow-up care, affected individuals need to do special workouts to support their muscles. Affected individuals can perform exercises recommended by their doctor on their own at home, in addition to continuing medical treatment.Affected persons should urgently avoid overexertion or excessive strain. Otherwise, the disease and symptoms may worsen. In order to be able to cope with the disease in everyday life, affected persons need emotional stability. Above all, however, the disease can be managed with the support and help of family and relatives. Affected persons should have an intact social environment so that help can be sought at any time. Since the disease is not curable, affected persons should undergo permanent psychological counseling. This can help sufferers learn how best to live with the disease. A self-help group can also be helpful. There, sufferers can compare lifestyles with other sufferers and do not feel alone with the disease. In addition, sufferers can learn other methods of coping with the disease. To increase the quality of life, people should choose activities that they enjoyed before the disease. It would be recommended to do this together with people from the familiar, social environment.
What you can do yourself
Various studies have shown that progression of the disease can be delayed if targeted exercise sessions are performed to support the muscular system. In addition to the physiotherapy sessions offered, the affected person can independently perform regular exercises in everyday life to maintain and improve the muscular system. In cooperation with the physiotherapist, individual workouts are worked out, which the affected person can use at home and on the road on his own responsibility at any time. Situations of overuse or overload are to be avoided. They can revise training successes and contribute to a worsening of the situation. The disease presents a particular challenge due to the visual changes and abnormalities. To cope with the disease in everyday life, emotional stability is therefore particularly important. Self-awareness should be encouraged and an open approach to the symptoms and their causes is helpful. The progressive course of the disease should be discussed with the patient at an early stage. Only in this way can unpleasant situations be avoided and the person affected can mentally adjust to possible developments in good time. Since it is a hereditary disease, no alleviation or cure of the disease can be expected. The patient must therefore learn how to structure his or her life as optimally as possible with the health restrictions. Contact with other sufferers or with self-help groups can be helpful in this regard.
