Tom, sorry if I'm bringing up some bad memories, but I'm a little curious about the details of your crash (apologies if you've discussed them previously, but I didn't find it). Just wondering if you remember what you hit on the ground with your temple.

The temple area is certainly particularly vulnerable and a part of the skull that is relatively easy to damage. However it's also fairly well protected in most impacts unless one happens to be unfortunate enough to hit a protrusion right in that spot. If I fall on the ground on my side my shoulder will take most of the impact and my head will rotate around and impact with the side of my skull well above the temple area - and in a spot where the skull is much stronger. Only if there happens to be a rock, curbstone, or other projection just above where my shoulder impacts would I have a direct impact on the temple area. (And of course the same is true if hit by a small projectile, such as a baseball, which is why batting helmets are designed with special emphasis on the temple area.) The temple area is recessed slightly and in a position of the skull that is unlikely to take the brunt of an impact in typical falls which helps to make up for its relative vulnerability.

But if I put on a helmet, the extra inch or two that it sticks out from the temple area makes it much easier for there to be an impact there even in a fall on flat ground. If I lie on my side on the floor while wearing a helmet and let my head rest on its side it'll be resting on the temple area whereas without the helmet I'd need to rotate my head significantly farther to the side and it'd be resting farther up on the skull. It would seem that the presence of the helmet can convert an impact that would have been concentrated on the strong upper part of the skull into one that's concentrated on the temple area.