I was trying the oral B12 B complex (the active forms) but after awhile, the shocks started coming back quite alot. I am back on injections for now, which seem to help completely. But I have also found that going to a upper cervical chiropractor may help many people with TN. It helped me immediately.
The upper cervical chiropractors are highly skilled in the spine and neck regions. A slight adjustment (hardly noticeable) puts your neck straight and then the spine follows. This allows the nerves to work properly and must have moved my nerves off the wrong portion on the skull where the Trigeminal Nerve lies. All I know is that it stopped the shocks. I have to be careful what I do to my neck now, and I follow the doctor's advice. I will still take the B vitamins, but because of a malapsorption problem, my body just doesn't assimilate it as well as it could. It maybe a year before my body heals from the gluten I have been giving it. I am very gluten intolerant and that can cause your body to have problems storing and activating nutrients.
Look up NUCCA, which stands for National Upper Cervical Chiropractors Assocation and see if you can find a referral list for one in your home area. Then don't wait, but go. It is the best decision I ever made. There is no painful period afterwards, either, as you hear there is from osteopathics. Just relief... Some people may take more than one adjustment for total relief... but I think it works great for this affliction.