Diaphragmatic Palsy – Causes, Symptoms, and Treatment

Located between the chest cavity and the abdominal cavity is our most important respiratory muscle: the diaphragm. Medical professionals also refer to it as the diaphragma (Greek for “partition”). The term “diaphragm” describes one of its functions: it separates the lungs within the chest cavity (thorax) from the organs located below.

The diaphragm is essential for breathing. It contracts during inhalation, causing it to descend downward. This creates negative pressure in the chest cavity, and the lungs fill with air. 

When a person exhales, the diaphragm moves back up, forcing used air out of the lungs. On the right side, the diaphragm lies slightly higher, with the liver located beneath it. On the left side, the spleen is found beneath the diaphragm.

The diaphragm is a thin, dome-shaped plate of muscle and tendon @ magicmine /AdobeStock

Doctors distinguish between unilateral and the rarer bilateral diaphragmatic paralysis. On both sides, the phrenic nerve (nervus phrenicus) runs from the spine through the thorax to the diaphragm. This nerve travels a long path from the spinal cord, passing lymph nodes, the aorta, the pericardium, and the lungs, to reach its destination. 

If the phrenic nerve is damaged along this path, phrenic nerve palsy can result. This palsy, in turn, causes a high diaphragm: during exhalation, the diaphragm shifts further upward than is normally the case.

In addition to diaphragmatic paralysis, other causes can also be responsible for a high diaphragm:

• obesity
• an enlarged spleen or liver
• Pneumonia
• Congenital malformations
• Pregnancy

If the diaphragm is positioned too high, its function is impaired. This also constricts the lungs and leads to breathing difficulties. In more severe cases, this manifests as shortness of breath.

If the diaphragm is positioned too high, it can no longer function properly or can only do so partially. In addition, the lungs have less space, which leads to breathing difficulties. Shortness of breath and respiratory distress are the consequences that patients experience.

The paralysis is less pronounced when standing than when lying down. This is because gravity pulls the abdominal organs downward, causing the diaphragm to move downward as well. In this position, the lungs have more room to expand. However, shortness of breath becomes more pronounced when bending over or lying down. Swimming also causes the paralyzed diaphragm to shift significantly upward, depriving the lungs of the space they need.

Physical exertion exacerbates the symptoms. 

This is particularly noticeable in patients who already have pre-existing respiratory conditions:

• heart failure
• COPD
• Obesity

Diaphragmatic paralysis increases the likelihood of frequently developing pneumonia.

Shortness of breath typically occurs when bending over, lying down, or swimming @ RFBSIP /AdobeStock

The phrenic nerve runs along various organs on its long path. It passes close to the spine, lymph nodes, and major arteries. The thymus gland—which is important for the immune system—the pericardium, and the lungs are also located along its path. 

There are many causes that can lead to damage to the phrenic nerve along this route:

• Doctors often injure the nerve during surgery, for example on the heart or the thymus. 
• Inflammation or a tumor can also damage the phrenic nerve and cause paralysis. 
• Viral infections are also suspected causes of phrenic nerve paralysis.
• In rare cases, the diaphragm muscle itself may be damaged, leading to unilateral paralysis.

Often, however, the cause of the paralysis remains unknown; in such cases, the doctor refers to it as idiopathic.

Rare cases of bilateral diaphragmatic paralysis may result from spinal cord injuries or neuromuscular disorders such as ALS. Here, too, idiopathic paresis—that is, paralysis of unknown cause—is possible.

To diagnose diaphragmatic paralysis, the doctor will perform a chest X-ray: the elevated position of the diaphragm, caused by the paralysis of the muscle, can be seen on the X-ray. 

If patients complain of shortness of breath after heart surgery, an X-ray examination is recommended.

A breathing test performed at rest, known as spirometry, reveals the extent of the damage to the diaphragm. This allows the doctor to determine how much air enters the lungs during inhalation. The test is performed both while sitting and while lying down. In cases of unilateral diaphragmatic paralysis, reduced lung capacity is evident while sitting. While lying down, even less air enters the lungs. Blood gas analysis from the laboratory provides information through blood test results.

The doctor uses ultrasound to examine the diaphragm and assess the muscle’s movement. The doctor can also determine whether the muscle moves with the necessary thickening during inhalation. This is necessary to confirm or rule out diaphragmatic paralysis. If the cause remains unclear after these tests, computed tomography (CT) or magnetic resonance imaging (MRI) can provide further insight and rule out other conditions. 

In rare cases, neurological tests such as neurography or electromyography are used to learn more about the nerve damage present.

Treatment for the paralysis is only necessary if patients suffer from shortness of breath. In such cases, doctors perform a diaphragmatic suspension procedure. If the damaged phrenic nerve causes only mild symptoms, this is not necessary.

During a diaphragmatic plication, surgeons use sutures to secure the diaphragm. This prevents it from bulging upward into the chest cavity. This improves the efficiency with which the remaining respiratory muscles can work: more air flows into the lungs during inhalation.

If other conditions such as obesity or COPD are the underlying cause, the patient should lose weight and/or take medication. 

If diaphragmatic paralysis occurs after surgery, it may be helpful to wait up to two years: In some cases, the diaphragm recovers on its own and the symptoms subside. Respiratory or physical therapy can provide additional support.

For people with a specific form of ALS, doctors have already used diaphragmatic pacemakers to stimulate the phrenic nerve.

Diaphragmatic paralysis is usually a result of damage to the phrenic nerve. It can occur after surgery, injuries, and illnesses and leads to shortness of breath and difficulty breathing. In severe cases, surgical diaphragmatic plication is effective. Treatment of the underlying conditions is also necessary.