OK so the optional update KB4512941 is the update that has caused Cortana to show excess CPU usage for extended period of time. (If I 'End Task' several times it stops).
After this update Cortana Search Bar (Bottom Left) no longer functions properly. Typing shows in bar but nothing happens EXCEPT then Cortana goes nuts with the CPU usage again.
I've tried a couple of fixs mentioned on forums including setting "CortanaEnable" value to 1
I've also tried the fix recommended for "BingSearchEnabled" set to 1
I'm quite concerned at this point because Cortana still shows CPU usage at around 35-45 on every reboot and system start and the Cortana Search function no longer works
All caused by the optional Cumulative update..KB4512941
I would investigate all forums and info about issues users are having with this update before proceeding to install (Wish I would have known)
Scary thing is I read Microsoft doesn't recognize any issue with this update.
Does a user now have to 'research' forums about offered updates BEFORE one downloads and installs

And I still don't have a fix....not happy!!