What Causes Orolingual Dystonia?

a year back my father start having problem with his down lip going right side while speaking , he goes to doctor and doctor pescribe to take some pills to boost energy ?? 8 -9 month down the road he start to have difficulties while speaking as tongues goes to right side while speaking and he couldn t chew his food properly he has been to lots of doctors lately and he didn t find that he getting any better , The consult doctor said that he belonged to OROLINGUAL DYSTONIA n he said that it would take time to cure. He took some medicines but nothing is improved but the doctor told us to continue to take the medicine. So i would like to know what exactly Orolingual dystonia is! and in his condition, we really don t know what to do. Please share me some suggestions. Thanks a lot!