Phrenic nerve palsy has many causes, and can be caused by lesions anywhere along its course, as it travels from the neck to pierce the diaphragm. The epidemiology will therefore match that of the underlying etiology [1].
Most of the cases are idiopathic or even thought to be post viral. Common causes include: tumors like bronchogenic carcinoma or neuroblastoma, trauma like post thoracic or neck surgeries or penetrating injuries, neuromuscular diseases, inflammation, direct compression from aortic aneurysm or cervical osteophytes, toxins like some spider or lizard toxins, alcoholic neuropathy, or endocrinal causes like hypothyroidism or diabetes mellitus (diabetic autonomic neuropathy) which enhances and exaggerates the effect of the other factors [2-4].
It is known that the incidence of phrenic nerve injury post open heart surgery is about 10% due to its close relation to the pericardium and to the mammary artery. This makes it, especially the left one, very liable to injury due to direct trauma of the nerve itself or its blood supply during left internal mammary artery (LIMA) harvesting, thermal injury due to local ice or cold saline on the heart or direct cautery trauma, or over traction of the pericardium during heart exposure |
