Ask your/his neurologist about a daTscan. As far as I know it is the only definitive test for Parkinson's but is usually done in major medical centers as the interpretation of the results is as important as the execution of the test. A radioactive isotope is injected several hours before scanning the brain with a gamma camera. The results should show the distribution of dopamine on both sides of the brain as the isotope binds to dopamine. A marked deficit on either side is the basis for a diagnosis of Parkinson's. This is how I finally got my diagnosis of Parkinson's after years of treatment for Essential Tremor, although they are separate disorders.