Brain scans of people exposed to certain neurotoxins reveal

Option A Wrong
Brain scans reveals brain damage when diagnoised automatically means the patient is close to or already suffering from Parkison's disease. It has nothing to do with other methods since one could lead to other with regards to medical examination.

Option B: Wrong
In fact, it is contrary here because the importance of such diagnosis is and should be timely enough in other to help cater for it so early too. It doesn't over-estimate the importance whatsoever contrary to the supposition of the option of the statement.

Option C: Wrong
It did not elaborate on the typology of brain damage neither did it infer that the diseases are caused by the same causal agents. it'd be however speculative to think in a manner that hasn't been proven by any medical examination.

Option D: Wrong
This is wrong from the passage statement. The aim of the patient was to test for brain damage and not parkison's disease although it'd be known to him that he/she is at the verge of been tested positive to parkison's disease because the two has identical relationship.

Option E: Right
This is so correct. As it seems, the aim of this diagnosis is to determine if there's brain damage and not majorly Parkison's disease so it should be expected that the treatment procedures would be specifically for brain damage and not for Parkison's disease. This was aptly captured by the question's specification.