What Is Spinal Muscular Atrophy (SMA)?
Spinal muscular atrophy (SMA) is an inherited (genetic) disease that affects the peripheral and central nervous systems as well as voluntary muscle movement. It weakens muscles due to the loss of motor neurons, a nerve cell that controls movement from the spinal cord.
With reduced motor neurons, there are minimal nerve signals to the muscles for movement. Generally, the term Atrophy is used in medicine to mean smaller, which describes why the muscles become weaker and smaller due to minimal use.
Types Of Spinal Muscular Atrophy (SMA)
The types of Spinal Muscular Atrophy are classified based on the disease’s transformation in the patient as time progresses.
Spinal Muscular Atrophy Type 0-Type 0 is a rare and extremely severe type of Spinal Muscular Atrophy that begins before the birth of a child. It is characterized by the reduced movement of the fetus during the final weeks of pregnancy.
During the process of birth, the infant becomes very weak and experiences breathing difficulties. Such infants may live for only a few months. Their feeding is also a challenge that finally affects their cardiac system.
Spinal Muscular Atrophy Type 1-Type 1 is the most common type of Spinal Muscular Atrophy with its symptoms being experienced immediately after birth to the age of 6 months. Infants with Type 1 SMA experience difficulties in breathing, eating, and muscle movement. It cannot be treated but the baby can be supported through breathing ventilators and feeding tubes.
Spinal Muscular Atrophy Type 2-Type 2 SMA is diagnosed between 6 months and 2 years of age. Delayed motor development and inability to meet the motor milestone is one of the major symptoms of the disease. Despite people with type 2 SMA being able to sit without help, they may need a wheelchair since they may not walk.
Spinal Muscular Atrophy Type 3-Type 3 SMA is diagnosed between 18 months and 3 years of age. People with SMA Type 3 can be able to walk at this stage but their mobility becomes increasingly reduced as they progress in age.
Spinal Muscular Atrophy Type 4-Spinal Muscular Atrophy Type 4 is not very common and it usually appears during adulthood. Its symptoms appear from 18 years through to mid 30syears of age.
Spinal Muscular Atrophy Symptoms
Generally, individuals with SMA go through a significant loss of muscle strength, control, and movement. However, the symptoms of Spinal Muscular Atrophy vary based on the type. The symptoms appear on a broad scope that ranges from mild to acute. While some people can stand and walk for short periods, others may find sitting, standing, and walking impossible for the rest of their lives. On the other hand, some individuals slowly lose these abilities as they progress in age.
The major symptom of SMA is the weakened movement of muscles. The commonly affected muscles include those near the backbone such as the neck shoulders and hips. Moreover, the upper limbs seem to be less affected than the lower limbs, which explains why individuals suffering from SMA cannot stand or walk.
Spinal Muscular Atrophy Treatment
The Food and Drug Administration (FDA) has approved disease-modifying and gene replacement therapies as the best ways of treating SMA.
For this therapy, only two drugs (Nusinersen and Risdaplam) have been approved to treat SMA.
Nusinersen (Spinraza). This drug is injected into the space around the spinal canal to stimulate the production of the SMN2 gene that is responsible for making more protein.
The drug has proved to slow the disease and strengthen the patients’ muscles.
Risdiplam (Evrysdi). The drug is used to prohibit SMN2 genes from reducing the production of protein. It is administered orally with the dosage depending on the baby’s weight.
Gene Replacement Therapy
This therapy is used to replace missing SMN genes with new genes. Onasemnogene abeparvovec-xioi is the only drug that has been approved to be used in this therapy.
Onasemnogene abeparvovec-xioi (Zolgensma). This drug is used for children below 2 years old to replace unfunctional SMN1 genes. It is administered only once to the child through a vein in their arm.
Spinal Muscular Atrophy Life Expectancy
The life expectancy of people with Spinal Muscular Atrophy depends on the type of the disease as well as the symptoms being experienced. Individuals with Type 0 SMA, who are probably infants, barely live for more than six months due to acute respiratory problems.
On the other hand, about 80 percent of children with Type 1 SMA barely make it to their 4th birthday. However, their survival has tremendously improved over the past decade due to advancements in care. People with SMA Type 2 and those with type 3 can live to their adulthood if given proper care.
Currently, there is no cure for Spinal Muscular Atrophy. The disease’s treatment relies on the Type of SMA as well as its symptoms. Individuals with SMA can gain significantly from physiotherapy and making use of wheelchairs and walkers.