What is diaphragmatic paralysis?
Diaphragmatic paralysis is where the diaphragm is not able to contract either on one side (unilateral) or both sides (bilateral). Breathing does not cease immediately as there are accessory respiratory muscles that normally assists with inspiration. However, these muscles are not as effective as the diaphragm and a person labors to breathe. Unilateral diaphragmatic paralysis (UDP) is often asymptomatic since it only results in a loss of about 20% of ventilatory capacity. Bilateral diaphragmatic paralysis (BDP) is symptomatic and when there is other diseases of the lung or airways, the person may be in severe respiratory distress. It can eventually lead to respiratory failure.
The human diaphragm is a muscular sheet that contracts and relaxes to enable the movement of the air through the lungs. It sits at the base of the lungs and separates the thoracic (chest) cavity from the abdominal cavity. Although it is a single muscle sheet, the central part where the mediastinum (containing the heart and great vessels) sits does not move. In this way the each side of the diaphragm affects the corresponding lung (left or right). When the diaphragm contracts, it increases the negative pressure around the lungs in the pleural cavity. The elastic lungs are forced to expand and air is drawn in – inspiration. When the diaphragm relaxes, it returns to its dome-shaped state thereby reducing the negative pressure. The elastic lungs recoil thereby pushing air out of the lungs – expiration. This action is controlled by the respiratory centers in the brain which sends impulses down the spinal cord, through the phrenic nerve (C3 to C5) to the diaphragm.
Causes of Diaphragmatic Paralysis
Diaphragmatic paralysis is almost always due to problems with the nerves. Less frequently it is due to muscle problems affecting the diaphragm. Sometimes it arises for unknown reasons but at times it is termed idiopathic due to inadequate investigations.
Tumors may compress the phrenic nerve and malignant tumors (cancer) can also destroy the nerve. This is mainly seen with :
- Bronchial carcinoma – most common cause
- Metastatic lung cancer
- Mediastinal tumors
- Cervical spine tumors
Disruption of nerve impulses to the diaphragm are the main reason for paralysis. Tumors, and in particularly bronchial carcinoma, are the most common causes of phrenic nerve damage that leads to diaphragmatic paralysis but other causes may include :
- Cervical radiculopathy where diseases of the cervical vertebrae causes nerve root compression (pinched nerve).
- Trauma to the nerve with birth injuries or motor vehicle accidents.
- Surgery that leads to accidental damage of the phrenic nerve. Mainly occurs with thoracic surgery.
- Stretching of the nerves with an aortic aneurysm or other mediastinal masses.
- Herpes zoster (shingles) which is a reactivation of the infection caused by varicella zoster (chickenpox virus).
- Multiple sclerosis where the protective insulating sheath around the nerve is destroyed by the immune system.
- Guillian-Barre syndrome is an autoimmune disorder where the body’s immune system specifically acts against nerves.
- Amyotrophic lateral sclerosis (ALS) also known as Lou Gehrig’s disease where there is gradual loss of the nerve cells due to biochemical, genetic or autoimmune factors.
- Polio where a viral infection disrupts the nervous system leading to muscle weakness. Post-polio syndrome that may arise years after recovering may also lead to diaphragmatic paralysis.
There are various other causes of peripheral neuropathy which is damage or disease of the nerves outside the brain and spinal cord that may lead to paralysis of the diaphragm. This includes diseases that may not specifically affect the nerves such as connective tissue diseases like systemic lupus erythematosus (SLE).
Some diseases that affect the muscles of the body may also involve the diaphragm. These conditions are not specific for the diaphragm and there may be other areas affected with muscle weakness or even paralysis. Disorders of the muscle that may lead to diaphragmatic paralysis includes :
- Injury to the diaphragm with severe trauma or during surgery.
- Muscular dystrophy where the muscle becomes prone to damage due to deficiencies of certain proteins.
- Polymyositis is disease where there is inflammation of the muscle leading to muscle weakness which appears to be due to autoimmune factors.
As with nerve diseases, certain inflammatory conditions may affect various tissues in the body and also involve the diaphragm.
Signs and Symptoms
The clinical features of paralysis of the diaphragm can vary depending on whether the condition involves one side or both sides of the diaphragm – unilateral diaphragmatic paralysis (UDP) or bilateral diaphragmatic paralysis (BDP).
Unilateral diaphragmatic paralysis is usually asymptomatic meaning that there are no symptoms. When symptomatic, the following may be noted :
- Difficulty breathing when physically active (exertional dyspnea).
- Reduced endurance.
- Mild orthopnea – difficulty breathing when lying down.
- Dyspnea at rest – only when there is also some lung disease present.
Clinical examination will reveal absence of breathing sounds, dullness on the affected side upon percussion and diminished movement when compared to the unaffected side.
- Rapid shallow breathing
- Difficulty breathing even at rest
- Pronounced orthopnea
- Disturbed sleep
- Morning headache
Clinical examination reveal absence of or severely dulled breathing sounds, inward movement of the abdomen when inhaling and signs of right side heart failure.
It is important to identify the cause of diaphragmatic paralysis and commence with the appropriate treatment as soon as possible. Treatment is not usually necessary with unilateral diaphragmatic paralysis (UDP). Ventilatory assistance (positive pressure) is only needed for bilateral diaphragmatic paralysis (BDP). There are various surgical procedures which may prove beneficial. This includes :
- Diaphragmatic plication where the dome of the diaphragm is surgically flattened to allow the lungs to expand to a greater degree.
- Diaphragmatic pacing is where the phrenic nerve is electrically stimulated to cause contractions of the diaphragm.
- Nerve reconstruction is where the damaged phrenic nerve is surgically repaired or even replaced (graft).
1. Diaphragmatic paralysis. Emedicine Medscape