Not in the sense that matters to this conversation, because neither event is in any way "destined" to happen. I quoted the verbatim dialogue: Crusher told Picard that Irumodic Syndrome was only one possible condition that his neurological defect left him susceptible to, and that he could certainly go through life without ever developing any of those conditions at all. So there's really no difference at all from the warp nacelle example. They're both just possibilities that could be prevented from occurring by any number of factors. Perhaps in the AGT future, Picard's Irumodic Syndrome was triggered by an infection he caught on a planet he never visited in the revised future. Perhaps it was caused by stress resulting from Deanna Troi's death, but her continued presence in the revised future prevented it. Perhaps the rejuvenating effect of the Ba'ku planet in Insurrection cured his defect. There are many, many different ways in which that future could be averted, because it was just one possibility out of many.
Also, "senile" is an outdated and insensitive term, based on the discredited assumption that dementia was an inevitable result of aging (senescence) in itself, rather than the consequence of disease or brain damage as it is now understood to be.
