Complications of Spinal Muscular Atrophy: Malnutrition And Aspiration Pneumonia

Reviewed by: HU Medical Review Board | Last reviewed: August 2021

Children with spinal muscular atrophy (SMA) often have progressive muscle weakness in the tongue, throat, and jaw. This usually makes it difficult for those with type 1 or type 2 SMA to swallow (dysphagia) and eat. It can also cause acid reflux.1,2

Poor swallowing and acid reflux increases the risk of aspiration or inhalation of material into the lungs. Combined with other gastrointestinal problems, it can also lead to low nutrient intake and poor growth. Nutritional support is an important part of SMA management in infants and children.1,2

Why does spinal muscular atrophy cause aspiration pneumonia?

Children with type 1 or 2 SMA often have difficulty swallowing (dysphagia) because of “bulbar” weakness. This refers to weak tongue, jaw, and throat muscles. It happens because of defective motor neurons in the bulb-like part of the brain stem (where the brain and spinal cord meet).1,2

Difficulty swallowing in infants with type 1 SMA increases their risk of inhaling material into the lungs. This is referred to as “aspiration.” Aspiration can happen when food or drink enters the airways during eating. Children with SMA also often have acid reflux. This happens when food or liquids in the stomach travel back into the mouth. Poor swallowing can cause inhalation of stomach contents into the lungs when breathing.3,4

Food and other particles in the lung can lead to lung infection (pneumonia). When pneumonia occurs because of inhaled food or liquids, it is called “aspiration pneumonia.” This can make breathing problems worse for children with SMA.4

What are symptoms of aspiration?

Not everyone who is experiencing aspiration shows symptoms. However, symptoms of aspiration occur as the body reacts to stomach contents traveling up into the mouth and airways. Signs of aspiration include coughing, choking, and vomiting.3

Colds and respiratory conditions can make swallowing and chewing more difficult for people with SMA. This increases the risk of aspiration. It is important to watch for signs of aspiration during illness.3

Why does SMA cause malnutrition?

Weak tongue, jaw, and throat muscles can make it difficult for people with SMA to eat. In turn, this can make it hard for them to get enough nutrients. Children with SMA also often tire quickly during feeding. This leads to malnutrition in many children with SMA. People with SMA usually have low body weight and bone density. Children with SMA often have an “inability to thrive,” which refers to an inability to properly grow.5-7

Malnutrition can worsen muscle weakness and lead to impaired motor functioning. Poor bone health increases the risk of fractures. Common nutrient deficiencies in SMA include:6,8,9

  • Vitamins A, D, E, and K
  • Folate
  • Calcium
  • Magnesium
  • Iron
  • Fatty acids

How are malnutrition and aspiration pneumonia prevented and treated?

Management of SMA focuses on changing food consistency to improve food intake and avoid aspiration. Because everyone with SMA has such different experiences, there is no single best diet to support nutrition. A dietitian who is familiar with the nutritional needs of people with SMA can help you find the right balance of nutrients while meeting your own needs and preferences.2,3,9

In general, people with SMA should avoid foods that are hard to chew and swallow. For example, tough pieces of meat or sticky foods are especially difficult. These foods often increase the risk of aspiration. Thicker drinks are also better because thin drinks are more easily aspirated.3,9

However, avoiding these foods and drinks can lead to nutritional deficiencies. People with SMA should be monitored often for nutrient levels. Nutritionists or dietitians can monitor nutrient intake and growth to ensure children are meeting their needs. They can also suggest a diet that provides enough nutrients.8,9

During colds or before and after surgeries, nutritional support is even more important. In these instances, nutritional support focuses on:3,8,9

  • Providing enough hydration
  • Maintaining electrolytes
  • Avoiding fasting

Children with type 1 SMA usually need a feeding tube to maintain proper nutrition and reduce the risk of aspiration. Feeding tubes can be inserted to deliver food directly to the stomach or intestines. This procedure is often done when the infant is healthy, as soon as type 1 SMA is diagnosed.2,8

Children with type 2 SMA may need supplementary nutrition through a feeding tube. However, they do not usually need it for all of their feeding needs. People with type 3 SMA rarely have swallowing or feeding problems. They may need nutritional support because of an increased risk of obesity due to reduced mobility.2,8

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