I was asked the question this week on whether symptomology or symptomatology is the correct usage.
I use symptomatology no matter which one is dictated. Here is what I have down in my notes:
Symptomatology refers both to the symptoms of a disease and a branch of medical science concerned with the symptoms of a disease (another more clouded definition says it is the group of facts that appear linked to any disease that ultimately identifies it, leading to a diagnosis). Most experts say that people inaccurately use symptomology interchangeably with the first word, but this is not correct. They challenge you to find symptomology in any dictionary of any kind.
One source, however, said symptomology is the study (or analysis) of symptoms. That same expert agrees that people inaccurately use symptomology when they should be using symptomatology because most people are describing the symptoms of a disease.
Let me know if you agree or disagree with this explanation or if you have something else that you follow.