I don't take benzos apart from the odd 1/4 of a 0.5 mg clonazapan at night
That is more than you think.
so its definitely not connected to that.
I wouldn't bet on that.
Valium withdrawal equivalence is 1.25-2.5mg (10x-20x). Clonazepam is a long halflife benzo that is arguably the most difficult to withdraw from. Many people have to switch from it to something else to get off of it, especially the last little bit. When tapering I take them down to 0.01mg of valium, 0.001 clonazepam at 1% per day. Faster than 1% per day can cause a lot of problems. Clonazepam is notorious for protracted withdrawal syndrome. A single such dose a week or even each two weeks could cause enough accomodation to cause withdrawal effects including spasms and headaches and another 30 or so symptoms.
How often do you take it?
I take the 1/4 of 0.5 mg quite often but just had 3 nights of taking nothing and no migraine at all so obviously there is no problem. Took 1/4 last night and no migraine but of course no AdnB12 for over a week. Its pretty certain that the migraines start 3 days after just 1/2 AdnB12 on its own and no MB12.