1) is Arnold Chiari malformation... This should show up on a cervical MRI. Ask your doctor.

2) there is a condition called normal pressure hydrocephalus:
http://en.wikipedia.org/wiki/Normal_..._hydrocephalus

This latter condition sneaks up on people... and often is misdiagnosed. Please read the Wiki site carefully. Many of your symptoms seem similar.

My husband works with a woman who developed a herniation in the cerebellar tonsils and she had all sorts of odd symptoms
including mental confusion. She went to the Cleveland clinic to have surgery finally for this and is now back at work.

Also... what was your B12 reading? Some doctors say normal when in fact it is not.
People with food intolerances often develop malabsorption of nutrients. B12 and Vit D are only now being recognized, but others may exist too. Zinc, and Bvits may be affected as well.