Skull trepanation among the early Indians of Canada and the United States.

The authors reviewed anthropological reports of skull trepanation (trephination) among the early Indians of Canada and the United States of America. Published reports of 20 trepanations in 19 skulls are reviewed. All were believed to have been performed ante mortem. Most were from the pre-Columbian era. Eleven were from Canada (8 from British Columbia) and 8 from the United States. The location of skull perforation was parietal in 9 cases and less often frontal (3) or occipital (3). The average skull opening was oval or oblong, with a diameter of 3.0 cm. The method of trepanation was probably gradual scraping in most cases. Skull fractures were not present in any case. About 90% of the trepanations showed evidence of healing, indicating survival. The authors discuss the evidence for skull trepanation in the United States and Canada, and compare these findings to the better studied South and Central American material.