RESUMEN
Trephination of the skull is an old surgical procedure practised in both the Old and New Worlds from the Neolithic period 7,000 years ago up to the present. Four methods (scratching, cutting, drilling and circling) were used for therapeutic or ritual (magical) reasons, predominantly in older males. The survival rate was between approximately 25% and 75%, the drilling and especially cutting being most dangerous. Macroscopic, CT and histopathological examination of three trephined skulls from the collection of Hrdlicka's Museum of Man, Charles University, revealed two types of bone defect. In the first type the margin of the defects was covered by the cortical bone of identical structure as the cortical bone on the inner and outer surface of the surrounding skull bones. These cases probably represent defects that healed in living persons for a long time, and consequently new cortical bone developed (skull No. 1). However, congenital origin of defects of this type cannot be excluded. The second type of defects, without cortical bone cover at the hole margin, could be caused by trauma in the post mortem period or may have been performed during the people's lifetimes--if they died shortly after their skull damage, so the healing period was too short for the formation of new cortical bone (skull No. 2 and 3).