Fnate I apparently have a condition called neuralgia which affects cranial nerves.

http://www.nhs.uk/Conditions/Neuralg.../Symptoms.aspx

It first happened to me on a few occasions in the 1990's - not while flying, and when I spoke to a doctor he didnt seem too concerned about it. Then I started flying short haul regularly in 2003 and noticed the facial numbness coming on as we reached altitude, leaving me in great discomfort, which ceased once we began descending. It only happened on some flights however. I often wondered if it was a particular aircraft type or altitude. It has never happened to me on a large jet (757, 767, 747 etc).

As I also suffer from hayfever of a kind, I happen to carry Sinutabs during springtime. I tried one of these once when the numbness started, and it worked. I never fly without them now...though I rarely need them, when I need them, they do the job.