I the gliadin test was the only test for celiac that was done, you were not adequately/thoroughly tested. Check out the applicable forum here or glutenfreeandbeyond.org or celiac.com for advice on testing. And keep in mind that the testing is ~ 30% false neg anyway. The chiari may be applicable as well, present since birth but mild and aggravated by injury and age.
http://en.wikipedia.org/wiki/Porphyria
i am thinking this is the disease you will be tested for ?
and some persons have issues with the B12 testing not being accurate, your normal homocysteine at least partially lays that to rest, but a methylmalonic acid test would be good as well. Taking a small supplemental amount (1 mg/d) to try for a level over 1000 may be of assist as well.
so, if you haven't had the blood draw yet get the proper celiac testing done and the MMA level...good luck