Everything about Spinal Muscular Atrophy Explained

Are your body muscles gradually becoming weak? If yes, then there lies a possibility of Spinal Muscular Atrophy (SMA). If you suspect that you or a loved one is developing it, you should go through the symptoms of this disease. If you notice similar signs, then you must consult a doctor immediately for diagnosis and treatment.

Spinal Muscular Atrophy is a common autosomal recessive disorder that can lead to gradual weakening of the muscles. The main characteristics of this disease are loss of anterior horn cells.

It can occur in individuals of different age groups starting from infants to adults. Based on the age group there, it can be classified into different types.

The types of SMA disease are as follows:

• Type I: Also called infantile-onset SMA or Werdnig-Hoffmann disease, it is more prominent in infants aged six months or less. They have trouble breathing normally and difficulty surviving beyond one year of age if not treated properly.

• Type II: This develops mainly in children between 6 and 18 months of age. Although their life expectancy is prominently reduced, they often survive till adolescence or even adulthood.

• Type III: Type III SMA is also called Kugelberg-Welander disease. It is generally observed in children with age above 18 months. Although they can walk independently, they have difficulty walking normally. However, disease-modifying treatment has shown promising results in its improvement.

• Type IV: Individuals with age above 21 years are prone to this type of atrophy, showing symptoms of this disease.

Each type is associated with several symptoms that are essential to identify at the earliest to ensure proper treatment.

The primary sign of spinal muscular atrophy that you can notice is a weakness of voluntary muscles. With the passage of time, you will experience an inability to control your muscles and a gradual loss of strength. If left untreated, you will eventually become unable to walk, sit or stand again.

However, the symptoms also vary with the type of SMA disease. These include:

• Type I: Diminished limb movements, hypotonia, lack of tendon reflexes, impaired breathing, fasciculations, swallowing and feeding difficulties.

• Type II: Inability to sit without support, respiratory disease such as hypoventilation in sleep.

• Type III: Difficulty in walking, running, climbing steps, tremors in hands, and prone to respiratory infections.

• Type IV: Mild proximal muscle weakness.

There are several causes behind the development of spinal muscular atrophy disease that leads to the appearance of such symptoms.

There are several causes of spinal muscular atrophy that are highlighted below:

• Defects in SMN1 gene: A defect in the SMN1 gene result in halted SMN production. This results in a deficiency of SMN protein, leading to the death of the motor neurons. Due to this, the muscles are unable to receive signals from the brain, which leads to atrophy.
• Copies of SMN2 gene: In the absence of the SMN1 gene, the SMN2 gene compensates for the production of SMN protein. Hence, if there is only one copy of this gene, infants usually develop type I SMA. However, with an increase in a number of these genes, the severity of atrophy decreases.

Apart from knowing what causes spinal muscular atrophy, it is crucial to be aware of the risk factors as well as to take necessary preventive measures.

The risk factors that increase complications of SMA disease are as follows:

• Infectious disease: Exposure to infectious diseases can increase complications to a great extent, as SMA can severely affect the immune system.
• Inactivity: If you do not move much or avoid exercising regularly, then you can encounter health issues like bedsores, respiratory infections and constipation.
• Unhealthy diet: If you do not have sufficient essential nutrients in your diet, it can contribute to extreme weakness.

So, it becomes essential to approach a certified doctor at the right time for the diagnosis of this disease.

Doctors suggest the following spinal muscular atrophy diagnostic techniques to confirm it:

• Blood test: When the conditions of the muscles worsen, they release creatine and kinase into the bloodstream. Thus, doctors suggest an enzyme protein blood test to check if their levels are high.
• Nerve conduction test: Often, doctors prescribe an EMG to measure the activity of the nerves and nerve muscles.
• Genetic test: The doctor often suggests various genetic tests to confirm the development of SMA.
• Muscle biopsy: This is a rare diagnostic test where a small portion of the muscles is removed to check for atrophy.

If the results are positive, the doctor can suggest a variety of treatment techniques based on its severity.

The doctor generally decides the type of spinal muscular atrophy treatment based on its type and severity. However, the treatments available are:

• Gene replacement therapy: The doctors inject onasemnogene abeparvovec-xioi in the veins of children below the age of two years. This is a one-time infusion drug substituting the faulty SMN1 gene with a functioning gene.

• Disease-modifying therapy: This treatment includes intake drugs such as Nusinersen for children between 2 and 12 years and risdaplam for adults and children above the age of two months. These drugs generally stimulate the production of SMN protein.

Since only a limited number of treatment options are available, it would be prudent to take the necessary precautions.

SMA is a genetic disease, and hence there are no such precautionary measures for this disease. However, you can undergo Preimplantation Genetic Diagnosis (PGD) to check if there are possibilities of passing this disease on. This ensures that your future generations have a fully functioning SMN1 gene.

In addition to this, you can also take some steps to reduce the severity of this disease. These include:

• Getting a balanced diet: You must add all the essential nutrients to your diet to enhance the strength and immunity of your body.
• Exercising regularly: You should exercise regularly to keep from bedsores and increase the strength of your muscles.

You can consult a doctor on experiencing the following:

• High fever
• Signs of pneumonia
• Vomiting
• Diarrhoea
• Severe dehydration
• Difficulty in breathing
• Extreme fatigue