What evidence suggests that some prehistoric patients survived trepanning?

Evidence that some prehistoric patients survived the surgical procedure of trepanning is found in the examination of recovered skull remains from the Mesolithic and Neolithic periods.12

Archaeologists have observed visual signs of bone healing around the edges of the openings created in these skulls. This biological response indicates that the individuals did not die during or immediately after the operation, but instead lived long enough for the bone tissue to begin the regenerative process. Such findings suggest that, despite the use of rudimentary tools—such as flint or obsidian—and a limited understanding of anatomy, these early surgical interventions were sometimes successful in allowing the patient to survive.123