Why is the Brain Affected?

I would like to know why the brain is affected when you have a bad head cold. Why does it feel like you are under the effect of some strange drug?
Take walking for example. When I walk down the street with a head cold it is not easy to walk. I understand that since the cold is in the head, and the ears are also in the head, and that the ears contain tiny hairs and cartilage that govern balance, thus balance may be affected. Yet it is more than a simple case of balance. Everything looks strange and different, and there is a feeling of lightheadedness.
There is also the matter of the strange waking dreams. On Monday night I barely slept at all, since my nose was so blocked I could only breathe with my mouth. It was not long before I began to see my situation in terms of a TRPG (Tactical Role-Playing Game) where I would move step by step on the grid between battles; the battles were me blowing my nose. I moved through the grid-based environment with my party from one battle to the next, at which point the TRPG scenario would cease and I would get up, knowing now that I was only in my bed, and blow my nose.
This went on all night.