How do you know what the main term is in a multiple-word diagnosis?

Example:
Acute Fulminating Multiple Sclerosis

In English, the noun at the end is usually the main term, with the adjectives before the noun describing the main term. In this particular phrase, though, "multiple sclerosis" is the main term, and "acute" and "fulminating" describe it.

http://www.answers.com/acute

http://www.answers.com/fulminating

http://www.answers.com/multiple-sclerosis