MIkeyy,

The altitude in a commercial aircraft never goes above 8000 feet. The pressurization system is set to maintain an 8,000 foot altitude pressure. You body would acclimate to the altitude quite easily. If there was a pressure differential that the body did not adjust to, all of the passengers eyes would bulge out.

To only difference the pressure would make would be what is called molecular pressure. At the higher altitude, the molecular pressure ( number of molecules per unit of volume) of the oxygen is less so the number that cross the cellular membrane is less so there is less oxygen transfer. As a result, the CO2 is not swapped out and the CO2 level in the blood and tissues increases. This is sort of similar to osmosis. This can cause the sick feeling.

High Altitude Cerebral Edema is not usually a factor at altitudes of 8,000 feet and below. Since your brain is liquid and semi-liquid, it does not compress or decompress. Only gases can compress or expand due to pressure.

The next time you fly, if you notice any return of symptoms, it is because your brain has not healed. The first study of this phenomenon was done in the early 1970's using an altitude chamber. The researchers found that the subjects with a prior concussion had symptoms. Those who had not had a prior concussion, did not have symptoms.

I am highly symptomatic at altitudes of 11,000 to 12,000 feet for extended duration. I had to give up flying my unpressurized airplane and sell it for just this reason. I was making cognitive mistakes. Rarely does a pilot get a second chance after making a mistake.

Most likely, your concussion from the go-kart racing caused a diffuse axonal injury. This stresses the axons that transmit signals between the neurons. When you were at altitude, these weakened axons started misfiring even more and left you with a residual problem after the plane landed. Some of these damaged axons will never heal and leave you with a weak area. The next time you are at altitude, the symptoms might be evident. The most likely symptom would be difficulty concentrating, but only if you had a valid way of testing your concentration skills.