Severing the phrenic nerve will paralyse that half of the diaphragm. Bilateral paralysis can be caused by spinal cord injury, motor neuron disease, infection, pneumonia, sarcoidosis, multiple sclerosis, polyneuropathy, myopathy and amyotrophy, cardiac surgery, lung transplantation, or mediastinal tumors. Diaphragm paralysis is best demonstrated by sonography. Breathing will be made more difficult but will continue provided the other nerve is intact.

The phrenic nerve arises from the neck (C3-C5) and