Spinal muscular atrophy or SMA is a genetic condition that mostly affects babies and children. It causes a breakdown of the nerve cells in the brain and spinal cord. Hence, the brain is unable to send messages for controlling muscle movement. When a child is affected by this condition, their muscles may become weak and shrink. This makes it difficult for them to crawl, walk, control head movements, and sit up straight.

Here is a look at the causes and symptoms of spinal muscular atrophy according to the types/stages.

Symptoms of SMA
The symptoms of spinal muscular atrophy can vary depending on its stages of the condition.

1. Type 0
This is a rare but most severe form of SMA. It develops when a woman is still pregnant. Babies affected by this SMA type will move less in the womb. They are usually born with weak muscle tone, joint problems, and weak respiratory muscles.

2. Type 1
This is yet another type of SMA. A child suffering from this may not be able to sit without help. They may also find it difficult to support their head. Kids with Type 1 SMA may have flaccid arms and legs and swallowing problems. The main cause of concern is respiratory muscle weakness. This causes breathing issues and makes survival difficult.

3. Type 2
This is also known as chronic infantile SMA. It may have moderate to severe symptoms and it affects children between 6-18 months old. Children suffering from this type can sit, stand and walk with help.

4. Type 3
This is the mildest form of SMA and its symptoms may appear when children are 2-17 years old. While a child can stand or walk without help, it may be difficult for them to get up from a chair, climb stairs or run. They may need a wheelchair later in life.

5. Type 4
This type affects adults and its main symptoms are muscle weakness, breathing problems, and twitching. It usually affects the upper arms and legs only. Although symptoms will be there throughout life, they will not affect mobility. Many times, the symptoms also get better with physical therapy.

Causes of SMA
Spinal muscular atrophy usually happens when motor neurons in the brain stem and spinal cord do not work. Motor neurons are the nerve cells that play an important role in controlling movement. At times, the neurons may also stop working because of the changes in SMN1 and SMN2 genes.

SMN1 and SMN2 genes may not make enough protein that the motor neurons need to work normally. Hence, the neurons break down and are unable to send signals to the muscles. This prevents the muscles from functioning properly. A child who has SMA gets the SMN1 gene from both parents. If a child gets an SMN1 gene from one parent, they may not show any signs of SMA. However, they can pass the gene to their kids.

These are the main causes and symptoms of spinal muscular atrophy. Many times, the condition is hard to diagnose as its symptoms may be similar to other conditions. Hence, the doctor may ask you certain questions and perform tests to make a diagnosis.