Mary, just a couple of quotes from Lara's post:

In response to the post about your vet not finding this regarding Puddy's tongue, I just wanted to add that nowhere on the internet could I find this tongue/burning mouth syndrome in connection with cats, just people.
And from a quote she quoted :
For example, “memory impairment due to vitamin B12 deficiency can precede blood symptoms of deficiency by years.
You found Sergeline through the net - used mostly for people, though use of it in dogs and cats is on the net also. But it sounds like this Vitamin B thing isn't even mentioned in cats on the net - so even if Dr Lee was a Google hound, he would have found nothing.

Just a couple of things to bear in mind when you talk to him.