Here is a quick list of the symptoms of embouchure dystonia. It comes from the DMRF website.
Air leaks at the corners of the mouth: Sometimes worse in higher registers and accompanied by a noticeable tremor.
Involuntary, abnormal contractions of the muscles in the face: Involuntary puckering; Excessive elevation of the corners of the mouth; involuntary closing of the mouth.
Some musicians’ difficulties are limited to sustained notes in particular registers or to certain passages at specific speeds. The dystonia is typically painless but may elicit intense psychological stress.
Read Katie Berglof's
great blog on her
It has lots of
Dr. Peter Iltis is a Professor of Kinesiology and horn player affected by focal embouchure dystonia. If you visit this page, that introduces his research, you can download a short movie of a player with FED.
Make sure your read David Vining's dystonia website! David re-trained his embouchure dystonia and writes extensively about the cause and the cures. Essential reading!