DLHUnicorn sent me a most informative link that I think is worth bookmarking:
Cornell's Veterinary Atlas of Poultry
http://partnersah.vet.cornell.edu/avian-atlas/
Extremely informative with photos and notes for diagnoses, but sadly, not encouraging in my case. The head twisting thing, even if it isn't Marek's, is never a good sign, especially when it's not due to a nutritional deficiency.
And regarding Mareks, One thing that is particularly discouraging is the mention of
transient paralysis:
"In transient paralysis syndrome, birds may exhibit ataxia and flaccid paralysis of the neck or limbs, 8-12 days post-inoculation. The clinical signs, caused by a transient vasculitis and edema in the brain, persist for 1-2 days and are followed by a rapid recovery. Several weeks after the transient paralysis, infected birds may develop MD lymphomas"
In December, three of my birds, including this one, had these exact symptoms, and then recovered 2 days later while on antibiotics. I had taken this particular bird to the vet the first time (she was the first of the three to show signs), thinking it might be Botulism or lead poisoning. The vet said "no", and also that he didn't think it was Marek's because "she would be dead already". He instead insisted it was extreme weakness, not paralysis, caused by anemia (blood test showed extremely low blood count), and coccidia (two different fecal tests showed absolutely NO sign of coccidia or other internal parisites...He was basing his "guess" on one of my other birds having had coccidia three months before). She, as well as the other two birds, made a complete recovery in a couple of days. At the time, I had attributed it to the triple-antibiotics the vet had prescribed, figuring that it HAD been either coccidia or a secondary bacterial infection as a result of the coccidia. But in retrospect, the antibiotics may have had nothing to do with it. She may now be exhibiting the signs of MD lymphomas, not an encouraging prognosis.
I'm going to continue to hand-feed her today and see what changes tomorrow, if anything.