Hey Beatle. I'm not a neurologist, but heavy binging + no meat will almost certainly have depleted your B12 for a longer period. As you probably know vegetarians/vegans should ideally supplement on B12 as the biggest source is meat (and organs). Combined with alcohol which flushes away the B12 it could certainly have lead to PN.

Do you currently take B12 and B1 supplements, and if so, which ones? There is quite a big difference in efficiency - most here would recommend the methylcobalamin version of B12 and the benfothiamine type of B1.

I know it could still be idiopathic, but you really don't need to be a neurologist to suspect B12 deficiency here. What did your test results say (if possible, the numbers, as most docs use outdated limits)?

You might still turn this around with proper supplements.