I forget the exact medical details of his illness at Nuremberg but IIRC they were consistent with being whacked on the head.
This interrogation at Nuremberg eludes to mistreatment
A. That is completely wrong. I know such a thing will make
no difference to me because in any case, you will sentence
me. May I put an addition to this? The colonel in charge of
the London Prison that I was in has told me that I would be
hanged in any case, no matter what the outcome would be.
Since I am fully aware of that, all I want to do is to clear
up on the fundamental things that are wrong here.
Q. Have you been subject to any treatment that you consider
to be intimidation, coercion, or undue influence since you
have been brought to Nurnberg?
A. I have not suffered from wrong treatment.
Q. Have you suffered any threats or any preconceived
statements that you are guilty of any crime?
A. Not directly, but I am treated as a man that is already
in a criminal prison.
Q. You have been examined at great length because of the
multitude of evidence and witnesses that have been presented
in the field where you are active.
A. I have not complained about any treatment and I am not
complaining now. The difference between the treatment here
and in London is like day and night.
Although perhaps he might have received more mistreatment during the trial just prior to his medical issues if it looked like he was going to stray too far off the reservation a la Ley.