sinus flush caused burning in back of head, not in sinuses

Different from older thread.  I get the burn in back of my head from horse radish, wasabi, lemon juice and sinus flush (warm salt water).  Not from crick in neck, it goes away after 5-30 seconds.  Sometimes the pain comes without any cause, but usually is very short lived, maybe 1-3 seconds.  It doesn't happen every day, but often. Since sinuses are behind the eyes and nose, I'm curious.  I also get a clear runny nose on some mornings, which had me thinking sinuses, hence the sinus flush. Didn't burn behind the eyes and nose, but immediately in the back of my head.  Anyone have any ideas?