Symptoms of chiari malformation seem so similar to Multiple schlerosis, which can be extremely difficult to diagnose.
Have you researched MS? Often before diagnose patients develop a long history of what looks like complaining with no cause - before the diagnosis is finally made.
Vitamin B12 Deficiency can mimic certain conditions. You will find a patient leaflet on The Pernicious Anaemia Society website. Doctors don't think about PA in one so young but there are cases that have a genetic cause. If you have B12d it can be treated with high dose B12 injections.
b12 Deficiency also mimics MS see here http://www.b12d.org/MS-like-presentation & symptom check for B12 Deficiency here http://www.b12d.org/content/b12-signs-symptoms-assessment