Deep brain stimulation (DBS) is a neurosurgical procedure involving the implantation of a medical device called a brain pacemaker, which sends electrical impulses, through implanted electrodes, to specific parts of the brain (brain nucleus) for the treatment of movement and affective disorders. DBS in select brain regions has provided therapeutic benefits for otherwise-treatment-resistant movement and affective disorders such as Parkinson's disease, essential tremor, dystonia, chronic pain, major depression and obsessive–compulsive disorder (OCD). Despite the long history of DBS,its underlying principles and mechanisms are still not clear. DBS directly changes brain activity in a controlled manner, its effects are reversible (unlike those of lesioning techniques), and it is one of only a few neurosurgical methods that allow blinded studies.[citation needed]

The Food and Drug Administration (FDA) approved DBS as a treatment for essential tremor in 1997,[citation needed] for Parkinson's disease in 2002, dystonia in 2003, and OCD in 2009. DBS is also used in research studies to treat chronic pain and has been used to treat various affective disorders, including major depression; neither of these applications of DBS have yet been FDA-approved. While DBS has proven helpful for some patients, there is potential for serious complications and side effects.

While DBS is helpful for some patients, there is also the potential for neuropsychiatric side-effects, including apathy, hallucinations, compulsive gambling, hypersexuality, cognitive dysfunction, and depression. However, these may be temporary and related to correct placement and calibration of the stimulator and so are potentially reversible.

Because the brain can shift slightly during surgery, there is the possibility that the electrodes can become displaced or dislodged. This may cause more profound complications such as personality changes, but electrode misplacement is relatively easy to identify using CT. There may also be complications of surgery, such as bleeding within the brain. After surgery, swelling of the brain tissue, mild disorientation, and sleepiness are normal. After 2–4 weeks, there is a follow-up to remove sutures, turn on the neurostimulator, and program it.

As with all surgery there is the risk of infection and bleeding during and after a surgery. The foreign object placed may be rejected by the body or calcification of the implant might take place.

Kendall Lee, M.D., describes deep brain stimulation surgery, and how it is is typically done with patients who remain awake, so neurological functions can be measured and maintained.