I have a friend who lives in Boston( this year it happened), and she was pregnant and had her case expedited fast. first, she was expecting the baby at any given moment.
secondly, she had her doctor send all information in regards to her condition to USCIS, and the doctor had the hospital administers as well sign-on
they sent that information and her husband was here within 10 days... I don't know why OP needs the case expedited, but if it's for medical reasons.
it can be done.. but!! he/she needs all doctors to sign on.