Diaphragm paralysis.

The diaphragm is a chief muscle of inspiration. Its paralysis can lead to dyspnea and can affect ventilatory function. Diaphragmatic paralysis can be unilateral or bilateral. The clinical symptoms are more prominent in bilateral diaphragm paralysis. Ventilatory failure and cor pulmonale are usually seen in severe cases. Although an uncommon cause of dyspnea it still remains an underdiagnosed condition. A restrictive process is seen on pulmonary function tests in diaphragm paralysis. The symptoms, oxygenation and vital capacity, usually worsen in supine posture. The diagnoses is usually suspected on chest x-ray and clinical exam and confirmed with sniff test or phrenic nerve stimulation/diaphragm electromyography. In most unilateral cases no treatment is needed, especially in the absence of underlying lung disease. In more severe cases modalities such as diaphragmatic pacing or plication of the diaphragm can be used. In bilateral diaphragm paralysis or in patients with ventilatory failure continuous positive airway pressure or mechanical ventilation and tracheostomy are generally needed. Prognosis is good in unilateral paralysis, especially in the absence of underlying neurological or pulmonary process. Prognosis is usually poor in patients with advanced lung disease, bilateral paralysis, and chronic demyelinating conditions.