To be honest it sounds like you have had EXACTLY all of the same symptoms i had although i had 18mm of brain leakage into the spinal canal (chaira Malformation) When i had went to the neurologist, he automatically said there was nothing he could do, i was sent straight to the neurosurgeon. I had brain surgery within that week. I had extreme pressure in the back of the skull, with pain feeling like someone was stabbing me constantly with a knife. When i'd stay standing up for about 10 minutes i'd feel extremely dizzy and become off balance easily. I also had double vison, which sometimes became worse. But with this the doctors said it wasn't from birth, it was caused by an accident which caused severe damage to the brain causing it to slowly leak through the spinal canal. But all in all, all of your symptoms are very similar to mind. I hope you find relief soon. My prayers are with you.