A craniotomy is a surgical operation in which part of the skull, calle a bone flap, is removed in order to access the brain. Craniotomies are often a critical operation performed on patients suffering from brain lesions or Traumatic Brain Injury (TBI), and can also allow doctors to surgically implant deep brain stimulators for the treatment of Parkinson's, epilepsy and cerebellar tremor. They are also widely used in neuroscience for extracellular recording, brain imaging, and for neurological manipulations such as electrical stimulation and chemical titration.