It is estimated that, throughout the world, spinal muscular atrophy (SMA) affects as many as one out of every 8,000 to 10,000 people. For the most part, this devastating disease affects babies and toddlers. However, the variation commonly known as Type 4 SMA or proximal spinal atrophy, though extremely rare, can strike at any time during adulthood and is a progressive disease that grows more severe over time.
SMA is a genetic disease that affects the nervous system, impacting control of voluntary muscle movement. It’s classified as a motor neuron disease because it causes patients to lose the motor neuron nerve cells in the spinal cord. This is due to a genetic mutation that causes a deficiency in SMN, which stands for “survival of motor neuron” and is a protein necessary for the motor neurons to function.
Symptoms of Type 4 spinal muscular atrophy
Because the effects of SMA can come on gradually, it’s sometimes difficult to notice until they grow fairly severe. Symptoms typically are related to the weakening of voluntary muscles, such as the muscles of the thighs, hips, shoulders, and upper back. And if the upper back muscles are affected, it can lead to curvature of the spine. Symptoms may also include:
- Difficulty in speaking or swallowing
- Muscle weakness
- Wasting away of muscles in the arms and legs
- Respiratory issues
- Muscle spasms and twitches
- Twitching of the tongue
- Hand tremors
Additionally, reduced or absent deep tendon reflexes – which your physician can test with a reflex hammer – may indicate the onset of SMA.
Unfortunately, there is no cure for SMA, so the treatments that are available are intended to manage symptoms and minimize complications. In 2016, however, the U.S. Food & Drug Administration approved nusinersen, marketed as Spinraza, as a treatment. Nusinersen was designed to increase the body’s production of the full-length SMN protein that is essential for maintaining motor neurons.
Patients and caregivers also have some non-pharmaceutical options that will help manage symptoms. For example, because SMA affects muscular strength, staying within a healthy weight will put less strain on the legs and hips when standing or walking. That means nutrition is an important area to focus on. You can also reduce spasticity and improve circulation by doing daily stretching and strengthening exercises. Mild heat, applied to the affected muscles, can also reduce pain.
For some SMA patients, physical and occupational therapy are effective at keeping joints from stiffening up too much, as well as slowing the progression of muscle weakness and even improving posture. In some cases, therapy is also needed to help the patient speak and eat solid food.
Most important, if you notice any of the symptoms of SMA developing, be sure to bring it to your doctor’s attention so you can slow down the progression of the disease and manage the pain and discomfort.