My mother has Parkinson's disease, and her neurologist says that higher doses of medication causes involuntary movements, like Michael J. Fox has. The condition is called Dyskenesia. My mother does NOT have these spastic movements because the doctors keeps her at a low dosage.
My MIL has Parkinson's. The symptoms of Dyskenisia are strikingly similar to those of the actual disease which it is why it is so difficult to titrate the dose, especially in the Elderly.
Very difficult disease.