Another interesting article, this one with a focus on assessment of issues pertaining to B12 deficiency. Amazingly, when contrasting things known in this article to current medical practices, the article was printed in 2005.
Note the following regarding treatment administered as part of the study:
"Patients with suspected deficiency were treated with cyanocobalamin 2 mg per day orally or 1 mg intramuscularly 3 times a week for 2 weeks, weekly for 8 weeks, and monthly thereafter. All patients were reevaluated within 3 months of beginning Cbl therapy."
This, B12 deficiency patients with neurological symptoms should be considered as under-treated, given that they received considerably less B12 than the recommended injection every other day or twice per week.
Study requirements for being considered to be a responder to (under-) treatment seems to be quite a high bar, especially considering that subjects could have been experiencing progressive damage for many years:
"Neurologic improvement in these patients during Cbl therapy was considered to be significant if paresthesias completely resolved, observed ataxic gait became normal, and/or vibratory sensation that was completely absent at least in the ankles prior to therapy became easily detectable within 6 months of treatment."
The link to the article:
BMJ Best Practice website advice on B12 deficiency
Paper preprint: Transcobalamin Receptor Autoantibodies in Central Vitamin B12 Deficiency 
IFAB testing guidelines per Mayo clinic laboratory website
