The causal link between manganese toxicity and the symptoms of Parkinson's disease -- trembling, shuffling gait, balance problems, etc. -- is quite strong, so don't let the defendant's counsel in a manganese lawsuit challenge the link. Those who work with magnesium get the symptoms of Parkinson's an average of 15 years before most people.
Although it doesn't hurt to have a good, general personal injury lawyer on your side in a manganese lawsuit, you'd do better to spend a little more time and effort to locate one who specializes in and has a good track record with similar cases.