Instead of searching for a cause after getting a diagnosis, energies are better directed to understanding the situation and the prognosis, and planning for care and support. Trying to attribute a cause is more like assigning blame, and will not help the situation but only create feelings of guilt.
This line from the Association of Frontotemporal Degeneration sums it up: The three C’s: I didn’t cause it. I can’t change it; and I can’t control it.