If you get offered to try this drug don't, it had me saying things that weren't true, halucinating and causing arguments with my wife/carer. A very bad experience this was and I never want to experience that again.
Really sorry to hear you've had such a bad experience with trihexyphendyl. I've been taking it for about three years now and it has really helped with my walking. I used to get what my consultant called, a 'peacock gait', which was very disabling. It seems that all the medications affect everyone differently.