What if it wasn't dehydration but rather a dehydration triggered mini-stroke? Dehydration causes thick blood that can stick in the blood vessels in the brain.

Looking up can cause plaques in the arteries to the brain to break loose.

Sore spots on the scalp/skin mean nothing other than an irritation to that surface skin and nerves.

You may have cause inflammation in your neck that is causing nerve sensations in your legs.

Stay hydrated and try to get on with your life.