The Food and Drug Administration (FDA) approved DBS as a treatment for essential tremor in 1997, for Parkinson's disease in 2002, and dystonia in 2003. DBS is also routinely used to treat chronic pain and has been used to treat various affective disorders, including major depression. While DBS has proven helpful for some patients, there is potential for serious complications and side effects.
DBS leads are placed in the brain according to the type of symptoms to be addressed. For non-Parkinsonian essential tremor the lead is placed in the ventrointermedial nucleus (VIM) of the thalamus. For dystonia and symptoms associated with Parkinson's disease (rigidity, bradykinesia/akinesia and tremor), the lead may be placed in either the globus pallidus or subthalamic nucleus.
All three components are surgically implanted inside the body. Under local anesthesia, a hole about 14 mm in diameter is drilled in the skull and the electrode is inserted, with feedback from the patient for optimal placement. The installation of the IPG and lead occurs under general anesthesia. The right side of the brain is stimulated to address symptoms on the left side of the body and vice versa.
Parkinson's disease (also known as paralysis agitans) is a neurodegenerative disease whose primary symptoms are tremor, rigidity, bradykinesia and postural instability. DBS does not cure Parkinson's, but it can help manage some of its symptoms and subsequently improve the patient’s quality of life. At present, the procedure is used only for patients whose symptoms cannot be adequately controlled with medications, or whose medications have severe side effects. Its direct effect on the physiology of brain cells and neurotransmitters is currently debated, but by sending high frequency electrical impulses into specific areas of the brain it can mitigate symptoms and/or directly diminish the side effects induced by Parkinsonian medications, allowing a decrease in medications, or making a medication regimen more tolerable.
There are a few sites in the brain that can be targeted to achieve differing results, so each patient must be assessed individually, and a site will be chosen based on their needs. Traditionally, the two most common sites are the subthalamic nucleus (STN) and the globus pallidus interna (GPi), but other sites, such as the caudal zona incerta and the pallidofugal fibers medial to the STN, are being evaluated and showing promise.
Research is being conducted as of 2007 to predict the onset of tremors before they occur by monitoring activity in the subthalamic nucleus. The goal is to provide stimulating pulses only when they are needed, to stop any tremors occurring before they start.
DBS is approved in the United States by the Food and Drug Administration for the treatment of Parkinson's. DBS carries the risks of major surgery, with a complication rate related to the experience of the surgical team.
Researchers reported in 2005 that electrical stimulation of a small area of the frontal cortex brought about a "striking and sustained remission" in four out of six patients suffering from major depression. Their symptoms had previously been resistant to medication, psychotherapy and electroconvulsive therapy.
Using brain imaging, the researchers had noticed that activity in the subgenual cingulate region (SCR or Brodmann area 25)—the lowest part of a band of tissue that runs along the midline of the brain—seemed to correlate with symptoms of sadness and depression. They implanted electrodes into six patients while they were locally anesthetised, but alert. While the current was switched on, four of the patients reported feeling a black cloud lifting, and became more alert and interested in their environments. The changes reversed when the current was switched off.
The effects of continuous SCR stimulation have produced sustained remission from depression in the four patients for six months. When reporting the results, the team did caution that the trial was so small that the findings must be considered only provisional.
Another hypothetically interesting site for DBS in depression is the nucleus accumbens, as that region appears to be associated with pleasure and reward mechanisms. A 2007 study reported that experimental use of deep brain stimulation of the nucleus accumbens showed promising results, with patients suffering from profound depression reporting relief from their symptoms.
Deep brain stimulation has been used experimentally in treating a few patients with severe Tourette syndrome. Despite widely publicized early successes, DBS remains a highly experimental procedure for the treatment of Tourette's, and more study is needed to determine whether long-term benefits outweigh the risk. The procedure is well tolerated, but complications include "short battery life, abrupt symptom worsening upon cessation of stimulation, hypomanic or manic conversion, and the significant time and effort involved in optimizing stimulation parameters". As of 2006, there were five published reports of DBS in patients with TS; all experienced reduction in tics and the disappearance of obsessive-compulsive behaviors. "Only patients with severe, debilitating, and treatment-refractory illness should be considered; while those with severe personality disorders and substance abuse problems should be excluded." There may be serious short- and long-term risks associated with DBS in persons with head and neck tics. The procedure is invasive and expensive, and requires long-term expert care. Benefits for severe Tourette's are not conclusive, considering less robust effects of this surgery seen in the Netherlands. Tourette's is more common in pediatric populations, tending to remit in adulthood, so this would not generally be a recommended procedure for use on children. Because diagnosis of Tourette's is made based on a history of symptoms rather than analysis of neurological activity, it may not always be clear how to apply DBS for a particular patient. Due to concern over the use of DBS in the treatment of Tourette syndrome, the Tourette Syndrome Association convened a group of experts to develop recommendations guiding the use and potential clinical trials of DBS for TS.
This result follows research carried out over 40 years, which has analyzed the effects of deep brain stimulation in the thalamus (and elsewhere) in patients with post-traumatic coma. While this research has shown some potential, deep brain stimulation is not yet a reliable cure for patients in post-traumatic coma.
DBS has been used in the treatment of obsessive-compulsive disorder and phantom limb pain. Although the clinical efficacy is not questioned, the mechanisms by which DBS works is still debated. Long-term clinical observation has shown that the mechanism is not due to a progressive lesion, given that interruption of stimulation reverses its effects. Results of DBS in dystonia patients, where positive effects often appear gradually over a period of weeks to months, indicate a role of functional reorganization in at least some cases. The procedure is being tested for effectiveness in patients with severe epilepsy.
DBS has been tried for patients with Lesch-Nyhan syndrome in Japan, Switzerland and France.
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 or MRI. 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.