I like the part where he is decribing his dad having his skull opened after the horseback fall and doctors finding evidence of alzheimers.
While a full autopsy can find the indications in the full brain, there is not test that I am aware of to examine brain lining when skull pressure is relieved or other similar test site and make a clinical pathological diagnosis.
Long term neurological evaluation can lead to such a diagnosis on a conditional basis, but such would not be done or relied upon at the time of head truama.
Good points. I appreciate you raising them.