Spinal muscular atrophy (SMA) is a hereditary disease in which certain nerve cells (motor neurons) die off. This leads to a degeneration of the muscles and general weakness. Most affected are children. A causal treatment is not possible. With a newly approved drug, however, a stabilization or even an improvement of the health status is possible. Read more about spinal muscular atrophy here.
Spinal Muscular Atrophy: Description
Spinal muscular atrophy is a hereditary neural disease caused by a genetic defect that results in the inadequacy of protein necessary for the muscles. As a result, nerve cells are destroying, which are supposed to transmit information from the central nervous system to the musculature (alpha motor neurons).
By breaking down these nerve cells, the muscles are less supplied with signals than is the case in healthy people. Muscle cells that are under stress are degraded over time. Over several weeks, months and years (depending on the type of disease), spinal muscular atrophy gradually leads to the depletion of muscle cells. As a result, the strength of the patients is at first relieved, and later on, their possibilities of movement are further limited, little by little. If the condition is not treated, even acquired motor skills can be lost again.
Spinal muscular atrophy becomes visible when a large number of muscle cells are already degenerated. The patients have very thin arms and legs and often a crooked back. Also typical are malpositions of the legs and a deformation of the upper body. Children who experience spinal muscular atrophy in their first months of life often do not learn to move-for example, to hold their heads or turn on their backs. In other forms of the disease in later stages of their own mobility is limited so that sufferers can no longer walk alone, eat or perform other activities. Spinal muscular atrophy also affects respiratory muscles, requiring artificial respiration and nutrition. In extreme cases, it can lead to a respiratory arrest and death.
Spinal muscular atrophy is divided into various forms. This classification is based on the severity of the disease and the time when first symptoms appear (manifestation time). The division of the forms is important to estimate the treatment and prognosis for spinal muscular atrophy:
SMA type 1
The SMA type 1 is also referred to as “acute infantile SMA” or after the first authors of the disease as “Werdnig-Hoffmann’s disease”. Spinal muscular atrophy of type 1 is evident in the first six months of life. Children born with SMA Type 1 are also referred to as “floppy infants”. This term refers to an entire body (ie generalized) muscle weakness. For example, children with SMA type 1 can not hold their heads alone and can not sit alone when they are older. Your life expectancy is greatly reduced. About two-thirds of all children with SMA type 1 die from respiratory arrest before the age of three.
SMA type 2
Type 2 Spinal Muscular Atrophy is also referred to as “chronic late infantile spinal muscular atrophy” or “intermediate spinal muscular atrophy.” In this disease, the first symptoms appear between the eighth and eighteenth months of life. and femoral musculature.The patient’s life expectancy is about 10 to 20 years.
SMA type 3
Type 3 spinal muscular atrophy is also referred to as “juvenile spinal muscular atrophy” or “Kugelberg-Welander disease”. First symptoms occur between the third and 30 years of age. The atrophy of the musculature is weak. Mostly sitting and standing are possible. Walking alone is only possible to a limited extent. Persons affected by SMA type 3 only have a slightly reduced life expectancy.
Spinal muscular atrophy: frequency
Spinal muscular atrophy is a relatively rare disease, affecting about 1500 people in Germany. The infantile form affects about one in 25,000 newborns, of the rarer juvenile form about one in 75,000 newborns. Despite these numbers, for example, SMA type 1 is one of the most common hereditary diseases in infants.
Similar disease: Bulbar muscle atrophy
Spinal muscular atrophy is often summarized with bulbar muscle atrophy. The latter shows similar symptoms as are classic for spinal muscular atrophy. In bulbar muscle atrophy, however, there is a mutation in another gene (in the androgen receptor gene, also called the AR gene). In addition to muscle weakness (predominantly in the legs) and muscle cramps, male sufferers also suffer from sexual dysfunction. Common problems are impotence or testicular atrophy. Bulbar muscular atrophy, unlike spinal muscular atrophy, is very rare in childhood or adolescence. Mainly affected are young adults.
Spinal Muscular Atrophy: Symptoms
Spinal muscular atrophy generally leads to a weakening of the musculature: By the breakdown of nerve cells the muscle fibers are less energized than in healthy humans. Muscle fibers that are not aroused will shrink over time and eventually degrade (muscular atrophy). Depending on the form of the disease, this muscle weakness is expressed by different symptoms.
SMA type 1
In SMA type 1, symptoms appear in the first half year of life. There is a generalized muscle weakness that affects the whole body. In addition, the tension of the muscles decreases against each other. Doctors speak of a hypotonia.
In newborns, this muscle weakness initially shows by a typical leg posture, which is reminiscent of a lying frog (frog leg position). The legs are bent, the knees angled outwards and the feet bent inwards. Even an independent lifting or holding the head is usually not possible. In advanced age, children with SMA type 1 can not sit or walk alone. Even speaking is not possible for many children, since the tongue muscles can be affected as well.
Another characteristic feature of type 1 spinal muscular atrophy is the upper body shape: the musculature of the chest cavity and the back are not properly formed. As a result, the upper body has a bell-like shape (Glockenthorax). Due to the low expression of the muscles on the chest and back sufferers take a curved posture. In addition, there is often an increasing curvature of the spine (scoliosis). The posture, which is bent forward and curled up, causes problems with breathing. Characteristic is a very fast and shallow breathing (Tachypnoe).
SMA type 2
Type 2 Spinal Muscular Atrophy causes symptoms only between the eighth and the eighteenth months of life. Affected children can sit alone, but they usually do not learn to walk or walk. The degeneration of the muscles is particularly evident on the lower and thighs. In addition, the ribcage may deform due to the weakness of the muscles lying there. Clinically one speaks of a so-called funnel chest.
SMA type 3
Spinal muscular atrophy of type 3 occurs after the third and the 30th year of life. Affected persons can sit, stand and walk alone. Mostly, the degeneration of the muscles is low. In the course of several years, however, it may come to restricting the performance: First, the affected sports activities, but also climbing stairs or carrying shopping bags difficult. After many years, Type 3 Spinal Muscular Atrophy, even in the elderly, makes running and any other effort difficult or even impossible. Overall, however, the symptoms are much lower than in the other two forms of disease. Spinal muscular atrophy of type 3 usually does not limit the lifespan to a minimum and the quality of life only marginally.
Spinal Muscular Atrophy: Causes and Risk Factors
Spinal muscular atrophy is a hereditary disease. The cause of the degeneration of nerve cells and muscles is a gene change. Thus, the spinal muscular atrophy is based on a change (mutation) of the so-called SMN gene (SMN = Survival of Motor Neurons).
Spinal Muscular Atrophy: Examinations and Diagnosis
Suspected spinal muscular atrophy requires a variety of examinations. First, the exact recording of the medical history (anamnesis). For babies and toddlers here give the parents information. In the case history you have the opportunity to describe changes and abnormalities in the behavior of your child (or yourself). Subsequently, the doctor can ask questions like
- Have there been any cases with similar symptoms in your family?
- Are your family’s hereditary diseases (possibly even spinal muscular atrophy) known?
- When did you first notice the symptoms?
- Have the symptoms worsened since you first noticed them?
After the anamnesis, a physical examination takes place. In infants, for example, it is tested whether they can keep their heads upright, whether (older) children can already sit alone or move their arms or legs by themselves.
In adults with suspected spinal muscular atrophy, physical stress tests are performed. It checks, for example, how much strength affected people can afford and for how long they can hold it. The stamina is also tested. In addition, the reflexes are tested. To do this, tap with a hammer on various tendons, for example on the heel or under the knee, and check the reaction.
Since the symptoms that occur are not only characteristic of spinal muscular atrophy, differentiation from other diseases is very important. This may require additional examinations of the nerves and muscles. Frequently, for example, the conduction velocity of the nerves (by means of electroneurography, ENG) or the muscles (by means of electromyography, EMG) are measured.
Also, a blood picture is usually made. If a spinal muscular atrophy is present, certain parameters of the blood picture are altered: an increased blood cell lowering velocity (ESR) can be detected, and the value of creatine kinase is increased. In addition, thyroid parameters are examined and the value of the parathyroid hormone determined.
The decisive factor for the diagnosis “spinal muscular atrophy”, however, is an examination of the genome. As this study is relatively expensive, it is only performed if there is a reasonable suspicion of spinal muscular atrophy. There is a reasonable suspicion, for example, if a family history of Spinal Muscular Atrophy or similar diseases is already known, or if the symptoms are severe.
For the genetic examination a smear (usually from the mouth) is taken. If a change in the SM genes is detected, a second test is usually performed. This should ensure the diagnosis. If a change in the SM genes is detected twice and the physical examinations provide evidence of a spinal muscular atrophy, then this genetic disease is in all probability present.
Spinal Muscular Atrophy: Treatment
Spinal muscular atrophy is very difficult to treat. A causal treatment (that is, to cause a change in the genes) is not possible. Therefore, an attempt is made to alleviate the symptoms as best as possible and to stop aggravation. How successful a treatment is depends on the form in which the spinal muscular atrophy is present. With a new drug that provides the lack of protein by the gene defect, an improvement in muscle function is possible. Treatment should always take place in specialized centers.
The focus of treatment is physiotherapy, which varies according to the age of the patient. In physiotherapy, different areas are addressed. With a regular exercise therapy is trying to slow the degeneration of the muscles. If the spinal muscular atrophy occurs very early and no active movement is possible, then movements are performed passively by the therapist. Sowird prevents the long immobility of the muscles and joints in addition to damage the tissue leads.
If the spinal muscular atrophy only breaks up a little later and if those affected can still move on their own, movements are trained that support the mobility and strength of the musculature. These exercises should always be performed at home, in addition to the therapist’s practice sessions.
Targeted language teaching (speech therapy) promotes speech learning in children. Elderly people diagnosed with spinal muscular atrophy also benefit from a logopedic treatment. Here, a deterioration of the language can usually be slowed down. Also, the correct swallowing and breathing are trained in the logopedic treatment.
In the further course also the pain therapy becomes important. In the process, older people affected or the parents of small children learn special relaxation methods. In addition, massage or heat and cold treatments can be performed. These also help with relaxation and help to slow down further degeneration.
If the spinal muscular atrophy leads to a strong curvature of the spine (scoliosis), then an operation is considered. The spine is specifically stiffened. This extra support of the spine not only protects the bones and joints, but the more upright posture that it gives helps with respiratory problems.
Medicines and vaccinations
Targeted drug treatment has not been available for spinal muscular atrophy yet. Since July 2017, however, a drug for the treatment of spinal muscular atrophy has been approved for the first time in Germany. This drug can at least partially offset the protein deficiency that results from the genetic defect. The missing protein is then available in higher quantities, whereby an improvement of the muscle function can be achieved.
In other ways, medications play an important role: Spinal muscular atrophy can in some cases affect the immune system. For infections, however, the use of certain drugs in SMA is not possible. That’s why, for example, regular vaccinations are important.
Stay on the ball
It is important in any form of treatment that parents or other relatives support those affected. Young children can not exercise the therapy independently, larger children often do not recognize the urgency. Adults with SMA tend to play down their symptoms and neglect therapy. However, regular therapy is necessary. Even if the spinal muscular atrophy can not be cured, the symptoms can be reduced and the course of the disease slowed down.
Spinal Muscular Atrophy: Disease Course and Prognosis
If a spinal muscular atrophy is present, the prognosis depends primarily on the form of the disease. In general, the later the symptoms appear, the better the prognosis. The spinal muscular atrophy is not curable. With a therapy, the life expectancy can be extended in many cases.
at SMA type 1 the progression of the disease can hardly be prevented. Children with Type 1 Spinal Muscular Atrophy have a life expectancy of around two to five years. Even with a therapy this can hardly be prolonged. Affected children usually do not learn to sit or stand or speak. You will never be able to become self-employed or live alone. The quality of life is severely limited. The most common cause of death in SMA type 1 is death from respiratory failure, usually within the first year of life.
at SMA type 2 the prognosis is a little better. With timely therapy, spinal muscular atrophy can be slowed down. Independent running is usually not possible. Affected children can usually sit alone. Some also learn to speak. The life expectancy is about ten to twenty years, in some cases, but it could also be extended with a therapy.
at SMA Type3 the prognosis is best. Again, the prognosis is better the later the first symptoms appear. If spinal muscular atrophy of type 3 becomes noticeable in childhood, physical performance is usually severely limited. Running is usually possible, but sports are not. If first symptoms do not appear until adulthood, sport is possible. Only in the course of several years, a gradual deterioration of performance. In old age, a wheelchair or even a permanent care may be necessary. Life expectancy is determined by the Spinal muscular atrophy of type 3, however, hardly limited.