This causes drowsiness, headaches and a general lack of well-being. When this happens, assistance with breathing through a face or nose mask, used only during sleep, may return the blood oxygen and carbon dioxide levels to normal and relieve the symptoms. A small number of affected people choose to have mechanically assisted breathing for 24 hours a day when their breathing muscles are so weak that they could not otherwise support life. This may need to be through a tracheostomy, when a tube is inserted through the neck into the trachea. An arbitrary means of distinguishing the two disorders depends on whether the affected person can still walk at age 16 years.
Muscle biopsy tends to show more or less severve changes, related to the severity of disability.
Since the discovery that dystrophin is defective in DMD and BMD, but more severely defective in DMD, examination of dystrophin in muscle biopsy samples can be used to distinguish them. However the conclusive test to distinguish BMD and LGMD is the examination of dystrophin on the muscle biopsy specimen. DMD is fairly predictable. There is a range of severity, and disability progresses more rapidly in some people than in others. Nevertheless the range of severity is rather narrow.