Patients with spinal muscular atrophy (SMA) suffer from muscle weakness and muscle atrophy. The reason for this is the progressive destruction of nerve cells in the spinal cord ('spinal'). In childhood, spinal muscular atrophy is divided into three types with different courses of the disease (SMA type I, SMA type II, SMA type III).
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Spinal muscular atrophy (SMA) is the second most common recessive inherited disease. There is one affected child for every 6,000 newborns. An equal number of boys and girls are affected.
Every 35th to 40th person in the population is a carrier for SMA. These people have no symptoms as they have a second intact gene in addition to the defective one. This intact gene compensates for the defect.
If both parents carry this gene and pass it on to their child, the child will develop SMA. The risk is 25 percent.
In spinal muscular atrophy, there is a decline in the motor anterior horn cells in the spinal cord. If these cells in the spinal cord are no longer functional, the muscles also no longer function properly. This leads to progressive muscle weakness and muscle atrophy.
Patients with SMA suffer from muscle atrophy, which can have various degrees of severity @ Framestock /AdobeStock
The different types of spinal muscular atrophy primarily differ in terms of age at onset:
50 to 60 percent of SMA patients suffer from the severe infantile form of SMA (SMA type I). In this form, the first symptoms appear in the first few months of life. Sometimes as early as the first few weeks of life. The children are usually unable to lift their heads and will never be able to sit freely. Most die without treatment in the first year of life or before the age of 2. The reason is a failure of the respiratory muscles.
The onset of the intermediate form (SMA type II) is later. The children learn to sit freely but not to walk. Doctors usually make the diagnosis at the beginning of the second year of life.
Children with a juvenile form (SMA type III) show a very variable picture of muscle atrophy. They initially learn to walk freely, but then lose some of their motor skills. Due to the highly variable course, specialists now divide the juvenile form into 2 further subgroups: type IIIa with onset of symptoms before the age of 3 and type IIIb with onset of symptoms after the age of 3.
SMA is first suspected when a baby or toddler fails to reach certain developmental milestones. In type I and type II in particular, the muscle reflexes do not function properly and do not react as they should. Some patients also have a slight tremor in the tongue. To confirm the suspicion, doctors carry out a genetic test (SMN1 gene).
An active substance that treats the cause of the disease has been approved since July 2017. The active substance is called nusinersen. Nusinersen almost compensates for the genetic defect. This enables the spinal cord cells to produce a functional SMN protein.
The disadvantage of this therapy is that doctors can only administer the active substance via the spinal fluid. This requires a lumbar puncture.
Clinical studies show that the use of nusinersen significantly improves motor skills. Nusinersen enables infants and toddlers to sit, crawl, stand and walk. Previously - without nusinersen - they would have died or never been able to move themselves. The new drug gives SMA patients and their relatives cause for hope.
Previously, SMA patients could only be treated symptomatically. Particularly in the early form of SMA, survival was only possible with continuous ventilation.
Specialists for the treatment of SMA are
The therapy mainly includes physiotherapy and respiratory therapy. In addition, doctors must alwaysadapt the provision of aids. An international group of experts has drawn up detailed guidelines for treatment standards for spinal muscular atrophy (www.treat-nmd.de).
The prognosis for patients with spinal muscular atrophy depends largely on the type of spinal muscular atrophy the children have:
Once the patient reaches adulthood, the disease continues to progress, but usually more slowly @ sofiko14 /AdobeStockDoctors are not yet able to predict how nusinersen will affect the life expectancy of SMA patients. The drug has not been on the market long enough for this.
However, study results show thatthe earlier patients start treatment with nusinersen, the better the outcome.
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