So there are two categories of hypo symptoms:
1) warning symptoms - when you're shaky, sweaty, anxious etc
2) cognitive impairment - your brain needs glucose to function when you get that drunk confusion feeling from a hypo, that's because your brain has run out of glucose & it needs the glucose to work properly. In order to pick up feeling from other bits of your body, your brain has to have glucose, so sometime, you can get weird numbness as part of a hypo.
It sounds horrible, but you just have to treat it the same as any other hypo, so long as the numbness resolves in half an hour or so of getting your blood sugar back to normal it's nothing to worry about. But it does suggest you should try, if you can, to treat your hypos sooner. Do you get the warning symptoms? Do you always have hypo treatment handy? You must be busy & focusing on exams at the moment - try to make it as easy as possible to treat your hypos so you have dextrose tablets/lucozade in you desk drawer etc so you don't have to get up from revising to treat!
I do get numbness in my mouth (as if you've had a local anaesthetic at the dentist) as part of a hypo, but I have no hypo awareness so my blood sugar drops quite low without me noticing. I haven't had it for a few months tho because I've been working hard not to let it drop so low. Having no hypo awareness is a complete pain in the bum, so if you can look after your hypo awareness by treating as soon as you get symptoms, I would highly recommend it.
Sorry for lecturing! I don't think it's that unusual and I don't think it's anything to worry about, just something to be avoided if possible. If nothing else, because I know it is a horrible sensation when it happens, not very nice.
Lots of luck with the exams!
