Manganese poisoning can cause symptoms very similar to those of Parkinson's disease: shuffling gait, slow movement, tremors, and the like. If you're diagnosed with Parkinson's and have worked around manganese products, you may have a basis for a lawsuit against an employer or manufacturer for not warning you about or protecting you from manganese poisoning.
If your medicines for Parkinson's disease just don't seem to help, there's a possibility that you have a related but different ailment called manganism. If you were a welder, steel worker, or manganese miner, you should let your doctor know and have the diagnosis re-examined.