CMT can cause breathing problems by affecting the nerves that control the muscles used for breathing. Just as CMT can cause the muscles of the lower legs, feet, or hands to become weakened, CMT can also cause the muscles used for breathing to become weakened. When these muscles weaken, it is a consequence of the effects of CMT on the nerves that control them, a process similar to the one that occurs when the hands and feet become weakened in CMT. The result is a reduced ability to fully expand the chest cavity with each breath, which leads to a reduced ability to fully inflate the lungs, a condition known as hypoinflation.
When talking about CMT-related respiratory muscle weakness, we often focus on the diaphragm and the phrenic nerve, which is the nerve that controls diaphragm movement. When this nerve is affected by CMT, the diaphragm can become weakened, resulting in CMT-related respiratory impairment. The diaphragm and its nerve are not the muscle and nerve involved in breathing, and therefore, the diaphragm is not the only breathing muscle that can become weakened in CMT.
