Phrenic Nerve

A nerve that arises mainly from the fourth cervical nerve and is primarily the motor nerve of the diaphragm, but also sends sensory fibers to the pericardium (the thin membrane that encases the heart).

When there is respiratory involvement in CMT, often, it is the result of the phrenic nerve being affected by the disease process of CMT. This affect on the phrenic nerve can cause the diaphragm to weaken and can therefore cause respiratory weakness.