Symptoms of Spinal Muscular Atrophy


Spinal muscular atrophy (SMA) is an inherited neurodegenerative disorder that affects lower motor neurons. Lower motor neurons are nerve cells that control voluntary muscle movements and are involved in walking, speaking, swallowing, and breathing.

The most common symptoms in most types of SMA are muscle weakness and decreased gross motor skills, impaired mobility, breathing problems, problems swallowing, and scoliosis (curvature of the spine). However, age of onset and severity of the symptoms vary among the different types of SMA.

Breathing Difficulties

The breathing, sucking, and swallowing difficulties that arise in people with SMA are related to weakness in the intercostal muscles, leaving the diaphragm as the primarily breathing muscle. This weakness creates a serious health danger, because people with SMA often develop respiratory complications, which can be due to lung underdevelopment and weak cough, respiratory tract infections, the aspiration of food and fluids, and sleep problems with hypoventilation.

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Fatigue is a state of physical exhaustion. It can decrease motivation and affect everyday activities, work, and social life. Besides perceived fatigue, SMA patients also experience muscle fatigue. Muscle fatigue is usually defined as an exercise-induced decrease in the ability to produce force. In SMA, the term is used to describe muscle weakness and rapid exhaustion during daily activities.

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People with SMA may experience several problems related to feeding. One such problem is food or drink entering the respiratory tract instead of the esophagus, referred to as aspiration. Aspiration can occur during eating and drinking or as a result of the contents of the stomach coming back up into the esophagus. This is especially a problem during times of respiratory illness, when vomiting, or in cases when chewing and swallowing are difficult.

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Scoliosis is an abnormal and progressive curvature of the spine caused by weakness in muscles of the back that support the spine’s position. It generally refers to a sideways curve of the spine; when viewed from behind, the spine forms an “S” shape. Scoliosis is the most common symptom that SMA patients may encounter, and its severity is linked to SMA type. Scoliosis can cause breathing difficulties, because the lungs have less room to expand and allow for deep breathing.

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Poor Muscle Tone

SMA is characterized by a progressive loss of muscle control, muscle movement, and increasing muscle weakness. Because it is a muscle-related disease, the proximal muscles are more severely affected than the most distant muscles, such as those in the hands and feet. People with SMA may never acquire or may gradually lose the ability to walk, sit, or move. In addition, normal growth and development can also place additional stress on muscles that are already weakened.

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Good nutrition is important for everyone’s good health, but in children with SMA, poor nutrition and an inadequate diet can further weaken muscles essential to breathing and the immune system. A balanced diet is believed to benefit patients by promoting better breathing, a stronger immune system, and improved growth and motor function, all of which contributes to an overall better quality of life.

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Abdominal Problems

People with SMA may suffer from abdominal problems such as diarrhea, bloating, spitting up, vomiting after meals, bad breath, regurgitation, and abdominal distention. Because these symptoms vary with the type of SMA and its severity, it is important that parents and healthcare assistants assess the nutritional status of the child regularly. In extreme situations, these symptoms may contribute to undernutrition.

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