In ancient times, trepanation was thought to be a treatment for various ailments, such as head injuries. It may also have been used to treat pain. Some scientists also think that the practice was used to pull spirits from the body in rituals. Many times, the person would survive and heal after the surgery. In this case, you need not fear trepanation, as it has already been performed. You need only sign the logbook!
You will need a "cache extracting tool", something like tweezers, to sign the log!