Many of us have used methyl B12 (methylcobalamin), and particularly 'Zobaline', to help heal neuropathy.
Zobaline is particularly good because is also contains a little bit of folic acid which, as I understand it, works synergistically with the B12.
Methyl B12 is brilliant for helping to heal nerve damage. It worked wonders for my cat!
Bertie had bad neuropathy when first diagnosed, but that resolved really quickly once I started him on Zobaline. That happened even though Bertie was still in high blood glucose numbers at that time.
Some cats take longer to heal, and some only start to see results once they get into better blood glucose levels. But a cat can
completely recover from neuropathy.
Zobaline can be crushed and added to food, and has no discernible flavour.
And it's very hard to overdose B12 because it's water-soluble and any excess is excreted in the urine.
The only contraindication I know of is where a kitty is known to have cancer. (And I
think that's something to do with B12 helping with general cell growth. But I'm sure someone will correct me if I'm wrong!

)
Edited to add:
Potassium deficiency can also cause leg weakness. A blood test is needed to confirm whether there is a deficiency, but potassium supplements can be given to correct it if necessary.