"C3, 4, 5 Keeps the Diaphragm Alive." Is phrenic nerve palsy part of the pathophysiological mechanism in strangulation and hanging? Should diaphragm paralysis be excluded in survived cases?: A review of the literature.

The phrenic nerve arises in the neck. It is formed from C3, C4, and C5 nerve fibers and descends along the anterior surface of the scalenus anterior muscle before entering the thorax to supply motor and sensory input to the diaphragm. Its anatomic location in the neck leaves the nerve vulnerable to traumatic injury. Phrenic nerve injury can arise as a result of transection, stretching or compression of the nerve, and may result in paralysis of the diaphragm. Consequences of diaphragm paralysis include respiratory compromise, gastrointestinal obstruction, and cardiac arrhythmias. There may be serious morbidity and onset of symptoms may be delayed. Cases of diaphragm paralysis occurring as a consequence of neck trauma are documented in the literature. In some cases, the forces involved are relatively minor and include whiplash injury, occurring in minor motor vehicle collisions, chiropractic manipulation, and compression of neck structures, including a case involving external neck compression by industrial machinery. It is concluded that phrenic nerve palsy might be part of the pathophysiological mechanism in strangulation and hanging, and clinical investigation to exclude diaphragm paralysis in survived cases should be considered.