golf ball headache:

(no, it has nothing to do with being hit in the head by a golf 
ball.)

when you remove the outer covering from a golf ball, you find what 
looks like a mass of rubber bands. the surface will consist of 
many fragments, since the rubber will have adhered to the inside 
of the shell. but once those are cleared away, you will find that 
the mass of rubber bands is, in fact, one continuous strand of 
long thin elastic, wound into a spherical shape. 

if you have nothing better to do with your spare time, unwind all 
that elastic. at the center of the golf ball is a somewhat pliable 
sac that seems to be filled with a thick liquid. puncturing this 
sac reveals a viscous, foul-smelling ooze. when i was a child in 
grade school, we firmly believed that this liquid was the most 
toxic substance ever invented, and that the mere sight of it would 
instantly kill an entire roomful of schoolchildren; it's nothing 
more than a form of liquid latex, though,  and just smells 
terrible.

what does all this have to do with a headache?

imagine that the long continuous rubber band is wound so tightly 
that, instead of feeling springy and elastic, it feels rigid, taut 
as bridge support cables. that's the tension in the muscles in 
your neck and shoulders and the back of your head.

imagine that the thick, foul liquid latex inside the sac is under 
tremendous overpressure which needs to be relieved. but the sac is 
so tough that it cannot rupture and release the pressure. that's 
your sinuses.

golf ball headache.