There are many types of neuromuscular disease, and they affect patients in different ways. Some only affect the lower portions of the body and have little or no impact on a child’s breathing or respiratory health. But many affect the breathing muscles, and these often cause breathing problems.
Neuromuscular diseases that can cause breathing problems include, among many others:
- Spinal muscular atrophy (SMA), which affects the spinal cord and nerves, resulting in muscle wasting and weakness
- Muscular Dystrophy (MD), which causes the muscles in the body to become very weak
- Congenital myopathies, muscle disorders that appear at birth or in infancy
These conditions can cause breathing problems in several ways:
- Weakened muscles in the chest and diaphragm make it difficult for a child to take full, deep breaths. As less air flows in and out of the lungs, carbon dioxide levels in the blood rise and oxygen levels in the blood drop.
- Weakened muscles in the back can lead to stooped posture (kyphosis) and a curved spine (scoliosis). This reduces the size of the chest cavity and the room the lungs have to expand when breathing and can make it very difficult to take deep breaths.
- Coughing is necessary to expel mucus from the lungs, and requires coordination between a number of muscles, from the chest and diaphragm to the throat. When these muscles weaken, the ability to cough effectively can be lost. When mucus builds up in the lungs, it also raises the risk of infection, enabling a minor cold to turn into pneumonia.
- Swallowing difficulties caused by muscle weakness in the mouth and throat can lead to choking and to food and liquid being inhaled into the lungs (aspiration). This can lead to inflammation of the airways and to infection and scarring in the lungs.
- Weakness in the muscles of the upper airways can cause the upper airways to narrow and the flow of air to the lungs to be limited, especially during sleep, a condition known as obstructive sleep apnea (OSA). Poor sleep from OSA can cause other serious health problems.
Most neuromuscular conditions are genetic, which means they are inherited from one or both parents. Different neuromuscular diseases have different inheritance patterns.
Spinal muscular atrophy (SMA), for example, is an autosomal recessive disease, which means that it must be inherited from both parents to affect a child.
Duchenne Muscular dystrophy has a slightly different inheritance path. It is caused by an X-linked recessive gene. A boy can have muscular dystrophy if the gene is inherited from either parent. A girl must inherit the gene from both parents for the disease to be expressed.
The signs of neuromuscular disease are generally in the form of muscle weakness, delays in the development of motor skills, or the emergence of movement problems, such a clumsiness or frequent falls. These signs and symptoms are different and can emerge at different ages for different neuromuscular diseases.
Early signs of breathing problems with neuromuscular disease include:
- Rapid shallow breathing and occasional shortness of breath while at rest
- Low energy
- Difficulty sleeping
- Waking with shortness of breath or with a headache that then goes away
- Colds that last for more than 10 days
As the condition progresses and muscles grow weaker, the breathing problems can become more serious. When a child’s oxygen levels are chronically low, a different stage of disease occurs with additional symptoms, including:
- Daytime sleepiness
- Morning headaches
- Significant shortness of breath at rest
Diagnosis of neuromuscular disease is made by a neurologist, based on the child’s symptoms and diagnostic tests. These tests may include:
- Blood testing for markers of muscle disease or damage
- Muscle biopsy — the removal of a small sample of tissue for examination under a microscope
- Genetic testing
- Electromyogram (EMG) — to measure electrical activity in muscles
- Electrocardiogram (ECG or EKG) — to record the electrical activity of the heart and detect abnormal rhythms or heart muscle damage
When signs of breathing problems are present, a pulmonologist may perform additional diagnostic test, including:
- Pulmonary function testing (PFTs) for children over 5 years old to measure respiratory muscle strength and the volume and flow of air moved through the lungs
- Pulse oximetry to measure oxygen levels in the blood
- Swallow function study — an X-ray imaging study combined with swallowing observations to assess the risk for aspiration
- Sleep study — to assess how well a child breathes at night and if they are getting in enough oxygen and removing enough carbon dioxide
Treatment for breathing problems with neuromuscular disease focuses on the specific causes of the child or adolescent’s difficulties.
For hypoventilation or respiratory failure, with high carbon dioxide and low oxygen, a ventilator can be used. A ventilator is a machine that helps a child take deeper, more normal breaths.
- Ventilation can be done through a nasal, oral or full face mask (non-invasive ventilation (NIV)), or through a tube inserted through the mouth or nose (endotracheal tube), or through the neck and into the windpipe (a tracheostomy tube).
- The typical approach with a ventilator is to give the patient a bigger breath than they would get by breathing on their own.
Chest and spine
Sometimes the muscle weakness causes a curve of the spine to the side (scoliosis) or to the front (kyphosis) or a rib cage deformity with the ribs rotating downward. If this happens, there are spine and chest wall surgeries that can be performed to help treat the deformity and stabilize the chest wall and spine.
If the child is unable to cough with enough force to clear mucus from the lungs and airways, treatment may include a combination of physiotherapy and mechanical devices.
- Chest physiotherapy helps the child clear mucus with percussion or clapping on the chest, posture changes and breathing exercises.
- Mechanical devices such as the Cough Assist® may be used to mobilize and remove mucus from the airways.
Children with breathing problems are at increased risk for severe respiratory infection. The treatment plan may include:
- Increased airway clearance therapies such as the Cough Assist®
- Acute antibiotic therapy during a respiratory illness
- Hospitalization if the child is not getting better, requires more care than can be safely provided at home, or is severely ill
Swallowing and Feeding
A specialist will work with the child to understand the specific swallowing issues and how to most safely and effectively make sure that your child gets the nutrition that he or she needs. This may include:
- Recommendations to avoid certain types of foods, or to thicken liquids to reduce the risk of choking and getting food or liquid into the lungs
- Using supplemental nutrition to help insure that your child gets that calories that he or she need
- Use of a feeding tube if it is not possible for your child to take in all the calories that he or she needs safely and effectively
With improved respiratory therapies for neuromuscular conditions, survival has increased substantially and the outlook for patients is better than it has ever been. With new medicines in development, the outlook is likely to improve even more.
Long-term follow-up care is critical for people with breathing problems from neuromuscular conditions. Patients at Children’s Hospital of Philadelphia (CHOP) are typically seen twice a year for regular follow-up visits, and some patients are scheduled for more frequent visits.