Trephines are surgical instruments that are used for drilling holes in the skull in order to remove bone tissue or fluids. Synonyms for trephines include skull drills, cranial perforators, and cranial trephine instruments. These tools have been used in various medical procedures for centuries, and have been developed and refined over time to improve their safety and efficacy. While trephination is not as commonly used today, it is still considered a viable treatment option for certain medical conditions. Whether referring to trephines or other similar instruments, these tools play an important role in modern medicine and continue to advance the field of neurosurgery.