There are 2 possibilities. Firstly, it might reflect underlying sinusitis. Although CT scans were done they are not 100% sensitive to detect sinusitis and secondly it could have been done when the sinuses were clear. A second possibility is that your eustachian tubes are blocked. As a result there's failure to properly equalise pressure between your middle ear and the back of your throat. This could be causing pain radiating up to the upper part of the forehead. The key is to use your antihistamines (try several ones and find the one that works for you) and your steroid nasal spray. You will need to discuss with your doctor several possibilities about medical treatment of your postnasal drip.
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