How can you tell the difference between impeded blood flow (increased intracranial pressure) and sinus pressure?

Location: Increased intracranial pressure would be more generalized "headache" or pressure. I would expect there to be neurologic deficits as well: change in mentation, gait, speech, etc. Sinus pressure is located: maxillary - below eyes; ethmoid - between eyes; frontal - above eyes; sphenoid - on top of head or very back of head. Sinus pressure is usually very localized.

Perfusion: The brain depends on good blood flow to remain healthy and functional. The blood must enter the brain and then be distributed to the cells and then flow out of the skull in a controlled manner. This process is referred to as cerebral perfusion. This can decrease due to poor inflow due to pressure or poor outflow due to clotting in the sinuses.