I'm 44 now and creaking a bit but in 35 years sparring and fighting in Boxing (and mma) I've never once been dropped from a punch, kick or elbow flush on the chin and I've been caught by some absolute corkers. However, the five times I've been dropped over the years have all been as a result of glancing blows around my temple area. Is this common to have a good chin but reduced punch resistance elsewhere? I was always a heavyweight so it's been the big boys trading with me.
People who suffer from vertigo/poor balance etc often have issues with the temple area. If you take a blow to the temple it does affect balance. There are also nerves that run through the temples so it could be that. I'm 45 and I've noticed my vision blurs a tiny bit if I practice ducking and weaving for too long. Vision and the temples are connected also.