Spinal muscular atrophy (SMA) is a type of motor neuron disease that is hereditary. The genetic disorder that begins most commonly during childhood is caused by a problem in the SMN (types 1 and 2) genes. These genes play an important role in controlling the contraction and relaxation of the muscles through signaling between the motor neurons (the nerve cells that control the muscles). Problems in the genes cause these nerve cells to break down, disrupting the signals. This leads to weakness of the muscles of the arms, legs and trunk. Muscle wasting sets in gradually. In severe cases, the muscles involved in swallowing and respiration become affected. This leads to respiratory and swallowing difficulties.
Treatment of spinal muscular atrophy
The U.S. Food and Drug Administration (FDA) approved EvrysdiTM (risdiplam) in August 2020 to treat patients who are two months of age and older with spinal muscular atrophy (SMA). This is the first oral drug to be approved for the disease, although the cost is a hefty $2.1 million per dose. Additionally, there are treatments that can help slow the progression of the disease, alleviate the signs and symptoms and help patients improve their quality of life.
For babies who suffer from respiratory and swallowing difficulties in the initial days of their life or adults who suffer from the same later in life, the following treatments may help.
- Artificial feeding: When there is weakness in the muscles that help with swallowing, babies cannot swallow the milk or food. The doctor initiates artificial feeding that can be either through a nasogastric tube (a feeding tube) inserted from the nose down the throat or a gastrostomy tube that is inserted directly into the stomach through the skin of the abdomen.
- Suctioning mucus from the throat: A suction machine can help clear the throat, if needed. The doctor passes a thin, plastic tube from the patient’s mouth to the back of their throat to suck away any mucus.
- External oxygen support: Artificial oxygen is delivered from an oxygen cylinder through a mask that covers the patient’s nose and mouth.
- Breathing exercises: A type of physiotherapy can help strengthen the respiratory muscles and make breathing easier for adults with SMA.
The FDA has approved three medications for the treatment of SMA.
- Spinraza (Nusinersen): This is injected into the fluid surrounding the spinal cord.
- Zolgensma (Onasemnogene abeparvovec-xioi): This is a gene therapy that is given in the form of intravenous (IV) injection.
- EvrysdiTM (Risdiplam): This is available in the form of an oral pill.
With the use of these medications, doctors have seen improvements in muscle weakness of affected children. However, the long-term effects of these medicines are unknown and more research is needed.
Other supportive treatments help patients with SMA ead better lives. These include
- Power wheelchairs
- Ventilator (breathing device)
- Occupational therapy: For difficulties in moving around, an occupational therapist or a physiotherapist can provide advice and support. They may train the child or patient to use assistive devices such as
- Physical therapy (water therapy and wheelchair sports)
- Modified access to computers
- Exercises to stretch and strengthen the spine
- Surgery to correct scoliosis