Trepanation and craniotomy are surgical procedures used to access the interior of a patient’s head. They involve drilling into the skull to remove a piece of bone (larger in the case of a craniotomy, and smaller in the case of a trepanation) to gain access to areas of the brain. Cranial trepanation is performed primarily to decompress the brain or to provide the neurosurgeon with access to areas of interest.

Various neurosurgical procedures can be performed through a trepanation opening, such as endoscopic ventriculostomy, drainage of subdural hematomas, neurosurgical propedeutics, microvascular decompression, stereotactic surgeries, etc. The hole of cranial trepanation is made with a surgical drill or trephine drill, usually with automatic stop.