Focal Dystonia
Dystonia is a neurological disease affecting the brain's ability to fire neurons (which control muscle movement) correctly. Focal dystonia specifically affects one particular area of the body and is usually completely isolated, affecting only one activity. The disease basically renders the sufferer unable to control the muscles in the affected area.
The presence of this condition in a brass player's facial muscles results in an inability to form an embouchure because of the individual's loss of control over the relevant muscles. Because the condition is neurological, there is, in terms of brass playing at least, no effective cure. Treatments using botox have been pioneered to treat focal dystonia in other parts of the body; however, they have been found to be ineffective in treating embouchure collapse. This is possibly because botox causes the facial muscles to relax; and although this collapse lessens the uncontrollable twitching of the muscles, the newly relaxed status deprives the player of the lip flexibility needed to play a brass instrument. For most brass players, diagnosis with focal dystonia signals the end of their careers.
Read more about this topic: Embouchure Collapse