has your father ever has shingles with the rash? there is a singles without a rash - Zoster Sine Herpete - which i live with, also PHN; blood tests show specific antibodies since 2016. can cause of host of issues, and is usually un/misidentified as is so uncommon that doctors don't consider something they have never heard of. the virus travels everywhere we have nerves; had to ask google this year if can have shingles w/o rash as was symptomatic for shingles, but NO rash ever. took YES to PC, test ordered, what i found was confirmed. symptoms can come & go, anywhere. if you look up and does not fit, better. for some reason, Mayo online only references the rash variety, google will reveal all. sincerely hope is not the case, but since i keep getting diagnosed for the rare & uncommon, have learned to look everywhere. fortunately for me, my PC is always willing and eager to learn more, and i am no longer surprised. Hope answers can be found for your father, good you are advocating for him.