Originally Posted by wphamilton

Scrapes, cuts, contusions are fairly common head injuries which are pretty well protected by a helmet. Whether protection against minor injuries is worth it to a given rider on a given day is another story.

Not to forget the possibility of skull fractures and inter-cranial hemorage, for which the helmets provide some significant protection. Anticipating ILTB's next comment, although this data is from pediatric patients:
Pediatric bicycle injury prevention and the effect of helmet use: the West Virginia experience.


"Skull fractures occurred in 3.2% of the helmeted and 17.4% of the un-helmeted (p = 0.0408) riders. The rate of intra-cranial hemorrhage was 0% in helmeted riders and 17.4% in un-helmeted riders"

To be sure, this says nothing of the likelihood of an injury to begin with but does suggest that these kinds of injuries are mitigated.