The extensive reading I have done has revealed no such thing as "too much B12," especially methylcobalamin.

Since the results of deficiency are so diverse, the answers are likewise diverse. Type of damage, extent of damage, etc. And there is a multitude of temporary (not necessarily short term) effects that may pass as repairs are made.

I would keep up the B12 and make as sure as possible that other nutrients are there in sufficient quantities.

rose