It's going to cost a good amount to prove that you suffer from manganese toxicity. For that reason, any firm that handles your manganese lawsuit on a contingency basis needs to be able to afford tens of thousands of dollars worth of expert testimony, reports, and research. Ask them if they can handle it before you take them on.
No case of manganese toxicity should be treated lightly. Not only does it indicate permanent damage to the nervous system, it can get progressively worse, sometimes even after the exposure stops. You have a right to file a manganese lawsuit and get recompense if you've been affected.