Hemidiaphragm is half part of the diaphragm. Diaphragm is a dome shaped muscle which is considered to be the main muscle for respiration. It plays vital role in breathing. It is also an important landmark for dividing the abdominal cavity from thoracic cavity. Breathing in and out is an involuntary process, meaning you do not have to think about it. This primary function is controlled by phrenic nerve; you do not have to command your body to do so. When the phrenic nerve is damaged the diaphragm gets paralyzed. Hemidiaphgram is when half of the diaphragm is paralyzed due to phrenic nerve damage.There are several reasons for it. Any problem related with lungs, liver or heart which is closely attached with the diaphragm can cause damage to phrenic nerve. There are two phrenic nerves each runs on one side of the diaphragm. Damage to any one side of the nerve can produce paralysis of that side of diaphragm. In most cases paralyzed hemidiaphgram does not produce any symptoms in resting phase unless there is associated disorder such as COPD, heart disease, muscular weakness, obesity etc. It is often an incidental finding on X-ray. Fortunately the condition is treatable.
Hemidiaphragm paralysis occurs due to damage to the phrenic nerve. You may not have heard about phrenic nerve before. It is the nerve which innervates the diaphragm, the main muscle for breathing. Phrenic nerve is actually twin nerve. One nerve is on the left side of the diaphragm and the other is on right side. It carries signals between brain and diaphragm. The nerve originates from the brain, continues down for few first vertebras and then bifurcates into right and left phrenic nerve. Each nerve passes on the side of body. The right phrenic nerve reaches the right side of diaphragm passing in close proximity with the windpipe, heart and lung. The left nerve passes close to the heart and eventually ends up into the diaphragm. Because of close proximity to lung and heart any problem with these vital organs can cause damage to that side of phrenic nerve resulting is a condition called hemidiaphragm. There are several risk factors that may cause phrenic nerve damage and subsequent diaphragm paralysis.
- Injury to the spinal cord, especially the upper three or four cervical spinal vertebras.
- Neck injury
- Blunt and forceful impact on the chest as in case of car accident or a blow, gunshot injury or a stab injury to the chest.
- Cancer of lung. The growth putting pressure on the phrenic nerve.
- Pneumonia and other lung infections.
- Viral disease such as herpes zoster.
- Radiation and chemotherapy to brain and mesiastinum area.
- Enlarged thyroid gland.
- Neuromuscular disease such as myasthenia gravis, GB syndrome, multiple sclerosis etc.
- Hemidiaphragm paralysis can develop as a complication of open heart surgery, removal of lung tumor, etc. It is unintentional damage caused to the nerve while operating for heart or liver surgery.
- Post infective neuritis occurring after measles, diphtheria, typhoid etc.
- Metabolic disturbance such as hypokalemia, hypocalcemia, vitamin B6 and B12.
In many cases the cause is never known.
Usually patient with hemidiaphragm paralysis is asymptomatic. It means patient does not experience any symptoms. However, in case if there is associated underlying lung disease such as chronic obstructive lung disease (COPD), tuberculosis, asthma, then patient may present with difficulty in breathing on exertion or even on rest.
Patient may present with decreased tolerance for exercise. Slight walking may produce breathlessness.
Patient may also experience difficulty in breathing when he lies on the paralyzed side of the diaphragm. There may be reduced breathing in sleep, especially during REM sleep.
Occasionally patient may also suffer from chest pain.
Hemidiaphragm paralysis can be detected with the help of X-ray chest. In majority of cases the condition is not life threatening. However, this also depends on the underlying cause that has produced diaphragm paralysis. Treatment mainly depends on correcting the underlying cause. For example if the cause is detected to be metabolic disturbance, it can be treated by correcting electrolyte imbalance. In case of a tumor in lung, removal of this tumor can reduce compression on the phrenic nerve. Often if the phrenic nerve is intact, a pacemaker called phrenic nerve pacemaker can be beneficial. In case if there is trouble of breathing during sleep non invasive positive pressure may be necessary.
Prognosis of hemidiaphragm paralysis is good after treatment, unless patient has comorbid conditions such as asthma, COPD or any other neurological disease.