Abdominal and nutrition issues in SMA

Spinal muscular atrophy (SMA) may cause a range of abdominal, digestive, and nutritional problems, so regular monitoring and support from nutrition specialists are important for people with the rare neuromuscular disease.

Genetic mutations cause SMA by disrupting the function of the survival motor neuron (SMN) protein. Low SMN activity causes the specialized nerve cells that control movement, called motor neurons, to degenerate and die, leading to muscle weakness and wasting.

Some SMA abdominal problems are directly related to weakness and wasting of the muscles that move food through the digestive system. Some nutrition-related problems in SMA may also reflect SMN’s effects on cells other than motor neurons.

How SMA affects digestion

Several disease processes can contribute to SMA digestion issues and related problems, including:

weakness in the muscles needed for chewing or swallowing
abnormal metabolism, including altered fat and sugar processing
weakness in the muscles that move food through the gastrointestinal tract

Difficulty chewing or swallowing

When the muscles that support sucking, chewing, and swallowing weaken, SMA feeding difficulties can develop. People with more severe forms of the disease, such as SMA Type 1 and Type 2, are more likely to experience this.

Feeding problems can make it more difficult to meet nutritional needs and increase the risk of food or liquid entering the airways, leading to respiratory infections and other complications.

Metabolic changes

Studies show that aspects of metabolism — the processes that allow the body to turn food into energy — are altered in people with SMA. This includes changes in how fats and sugars are broken down. These changes may be related to the wasting of muscles, where many metabolic processes occur, and/or a direct consequence of SMN protein loss.

Changes in fat metabolism can lead to disproportionate increases in fat levels despite calorie intake. This can raise the risk of other health issues such as fatty liver disease. Altered fat metabolism can also lead to problems with the absorption of certain vitamins, contributing to nutritional deficiencies.

Problems with sugar metabolism are more variable — some people with SMA experience low blood sugar, while others have high blood sugar. Both can increase the long-term risk of health complications if untreated.

Gastrointestinal tract problems

SMA can affect gastrointestinal motility, or the way that food moves through the digestive system, which is likely related to weakness in the muscles that coordinate this process.

Slowed gastrointestinal motility may manifest as delayed emptying of the stomach (gastroparesis), which can lead to symptoms such as:

nausea
vomiting
spitting up food
acid reflux
fullness after eating just a few bites
a bloated belly or other stomach swelling (abdominal distention)
stomach pain

Impaired movement of food through the gastrointestinal tract can also lead to constipation and gastroesophageal reflux disease (GERD), a condition characterized by chronic acid reflux.

Acid reflux and GERD in SMA

Acid reflux occurs when stomach acid travels backward, moving up into the esophagus, the tube that carries food from the throat to the stomach. When this occurs chronically, it’s called GERD.

SMA acid reflux may be related to low muscle tone in the digestive tract, as well as to scoliosis, an abnormal curvature of the spine that’s common in SMA and may affect the shape and function of the gastrointestinal system.

Symptoms of acid reflux and GERD may include:

food or liquid backwashing into the throat
burning sensations in the chest or stomach
nausea
sore throat
coughing, wheezing, and shortness of breath

GERD can also increase the risk of lung or respiratory complications for people with SMA.

Managing constipation and bloating with SMA

Digestive tract muscle weakness and reduced gastrointestinal motility in SMA can cause stomach pain, bloating, and constipation. Lifestyle changes, medicines, and supplements may help manage these symptoms under supervision from healthcare professionals.

Common recommendations for SMA constipation relief and bloat management include:

increasing fiber and fluid intake
using bowel-regulating medications or laxatives
increasing intake of microorganisms that can help with gut health (probiotics)
increasing physical activity levels, as tolerated, which helps boost digestion

Probiotics for SMA can come from supplements or probiotic-rich foods like yogurt. Fiber intake can be increased through supplements or fiber-rich foods such as whole grains, fruits, and vegetables. A dietitian can help develop an appropriate SMA eating plan for constipation.

For babies with SMA who experience bloating or stomach distention, regular burping and gas relief may help ease symptoms.

Medical tests for SMA gut health

In some cases, a doctor may recommend diagnostic tests to promptly identify, characterize, and treat digestive problems. This may include:

swallowing studies: involves a specialized type of X-ray video or a small camera inserted into the throat to visualize swallowing
abdominal X-rays: can visualize stool buildup or blockages contributing to constipation or other symptoms
gastric emptying scintigraphy: uses a radioactive tracer to track the movement of food through the digestive tract
endoscopy: uses a small tube with a camera attached to examine parts of the digestive tract
blood tests: can identify vitamin deficiencies, blood sugar changes, and other nutrition-related or metabolic factors

Other tests can help track body composition, including bone, fat, and muscle, to better understand a person’s nutritional status. That includes specialized X-ray techniques and skin fold tests, which can estimate body composition by measuring the thickness of a fold of skin.

Some tests may only be recommended if concerning symptoms arise, while others may be part of regular monitoring. Experts typically recommend nutritional and dietary follow-up every three to six months for infants and young children, and annual check-ups for older children and adults.

These visits can help doctors track changes and make recommendations for treatment and lifestyle modifications. For example, underweight patients may need specific SMA weight gain tips, while overweight patients may benefit from physical activity tailored to their ability level.

Managing nutrition safely

Specific dietary needs vary greatly in SMA, depending on functional abilities, specific symptoms, and potentially, the use of disease-modifying treatments.

Body composition also plays a substantial role. Some people with SMA may be underweight because they have trouble eating or are not absorbing enough nutrients from food. Others may become overweight because of metabolic issues and low physical activity levels. Either of these situations can further contribute to low muscle mass and poor bone health.

As such, it is important to seek expert, individualized advice from doctors, nutritionists, and dietitians about safe and appropriate nutrition management. In addition to treatments for specific gastrointestinal problems, nutritional recommendations for SMA may include:

working with a dietitian to develop a well-rounded eating plan that supports muscle strength and digestion, while meeting individual caloric needs
taking supplements and vitamins as needed to avoid nutritional deficiencies
consulting an occupational therapist or speech therapist to help with difficulty swallowing or chewing

People with severe feeding difficulties may need a feeding tube to ensure adequate nutrition.

SMA News Today is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.