Thank you for your response, but the pullet doesn't have any of the symptoms associated with these conditions and because the onset was so sudden, I tend to think that Alan Stanford's explanation of trauma to the vaulted skull (neurological insult) may be a pretty good explanation, as to the abrupt onset and sudden cause of her condition.
The reason I am thinking along these lines is that she has been in a very controlled environment, is not being free-ranged and none of my other silkies have any symptoms that would indicate this is a wide-spread problem. I have about 16 silkies and they are all doing fine. They have been checked, and are worm-free, coccidiosis free, and in generally great health and condition.
However, I am going to take her to my vet who does have a degree in poultry science from TX A&M and see what turns up.
I will let you know how it goes. I just got her to take some mashed, hard boiled egg, so maybe I can keep her strength up, if in fact, this is due to trauma, until the swelling (?) goes down and she can function. I am going to try to keep from having to put her down if I can.
I appreciate your kindness. Chickens are neat and mine seem to be really bright little creatures. I never realized how smart they are !