I don't know what the sphenoid sinus is, but I just fixed a sinus problem by putting my head over steam and adding drops of eucalyptus oil. Every time the eucalyptus oil hit the steam it was really powerful - after being sick for 2 weeks it was all of a sudden like I hadn't been sick at all. I did lots of drops of the oil.
I've done a neti pot for many years, and I surprised that didn't fix the sinus problem - the Dr. said that the steam gets places that doesn't. I always do the neti pot after the steam, to wash out the stuff the steam losened up.