The MAIB are, I assume, the same as the CAA medical board - in other words tell them nothing.....!!! If you call up the CAA at Gatwick and say i need to go to hospital for a minor op they pull your medical and charge you 500 quid plus 3 visists and 3 months before re-issuing you with a restricted medical.......... all for a bit of grissle to be removed by key hole surgery....!!!! = they are like the tax man - bugger if you dont - they bugger you if you do.....!! cant win!
Normal common sense precautions apply - and no i dont condone not telling the MAIB about things they need to know about....!