Did Rad Exposure Cause Parkinson's?

We know that radiation results in brain degeneration.  And Parkinson's is brain degeneration in a particular area called the substania nigra.

So could Dan Hott's Parkinson's disease have been caused by his 1970's radiation exposure?

His neurologist thinks so.

The VA doesn't.
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I wish the article had provided the actual radiation dose.

"....perhaps the greatest amount ever any American has received."

Does that mean received and survived?  Or truly received whether the person survived or not?