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Deep brain stimulation (DBS) is one of a group of treatments involving surgical implantation of a medical device called a brain pacemaker, which sends electrical impulses to specific parts of the brain. This surgical procedure is used to treat severe essential tremor and tremor, rigidity and bradykinesia (slow movement) associated with Parkinson's disease, as well as primary dystonia and other conditions. Brain pacemakers were approved by the Food and Drug Administration (FDA) in 1997 as a treatment for Parkinson's disease as well as essential tremor, and in April 2003 as a treatment for primary dystonia. In March 2005, the results of a Canadian study performed by doctors from the University of Toronto were published indicating that DBS may also alleviate symptoms in patients suffering from treatment-resistant clinical depression.
Procedure Components of Brain pacemaker used in DBS: There are 3 types of stimulation which differ according to the specific area of the brain which is stimulated: The right side of the brain is stimulated to address symptoms on the left side of the body and vice versa. All three components are surgically implanted inside the body. The surgery consists of two parts. First, the location for the leads must be determined and then the neurostimulator is implanted in the patient’s subclavicular area. During the lead insertion the patient is given local anesthesia and lies awake. During the implantation of the stimulator the patient is under general anesthesia. The surgery involves craniotomy for implantation of an electrode into the subthalamic nucleus or basal ganglia of the brain. The electrode is powered by a battery-operated neurostimulator typically placed under the collar bone. A connecting wire of platinum and iridium, insulated with polyurethane, conducts signals from the neurostimulator, which is hermetically sealed in a titanium housing. Electrical stimulation through the electrode interferes with neural activity at the target site (usually specific areas of the thalamus or the subthalamic nucleus and pallidum of the basal ganglia) which can alleviate tremors, rigidity or bradykinesia. The choice of target site depends on the symptoms being addressed. After the surgery is completed, an expert calibrates the unit in order to maximize its effectiveness. The programming of the neurostimulator can take up to a year to achieve an optimal setting. Typically DBS is performed unilaterally on the side of the brain opposite to the side of the body most debilitated by the disease, but in many cases it is performed bilaterally in a single operation. Parkinsons disease Parkinson's disease is a common neurodegenerative disorder which causes loss of control over body movement, balance and coordination, as well as non-motor symptoms such as depression. DBS does not cure Parkinson's, but it can effectively suppress some of its symptoms and so improve the patient’s quality of life. DBS has been found to significantly alleviate symptoms in two-thirds of Parkinson's patients, and has recently been used more frequently to treat cases of severe essential tremor. Unusually for a surgical procedure, it is approved in the United States by the food and drug administration. DBS carries the risks of major surgery, with a complication rate proportional to the experience of the surgical team. The tipping point is 50 DBS procedures and the cushion is 100 DBS procedures. Depending upon usage, the battery in the neurostimulator must be replaced after three to five years. Due to the necessity to maintain an uncontaminated field within the body, the entire unit must be reimplanted. Nevertheless, this is a minor surgical procedure involving only the shallow subclavicular pocket where the neurostimulator resides. Remaining battery life may be reliably determined with a telemetric programmer so that arrangements can be made to replace the unit prior to battery failure. Clinical depression Dr. Helen Mayberg of the University of Toronto, Dr. Andres Lozano of Toronto Western Hospital, and Dr. Sidney Kennedy of Canada's University Health Network (UHN) in 2005 reported in Neuron 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 clinical depression, whose symptoms had previously been resistant to medication, psychotherapy and electroconvulsive therapy. The researchers reported that, using brain imaging, they 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, the team reported. When reporting the results, the team did caution that the trial was so small that the findings must be considered only provisional. Tourette syndrome 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 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. Other clinical applications DBS has been applied to the treatment of obsessive-compulsive disorders, cluster headaches, and obesity. Although their clinical efficacy is not questioned, the mechanisms by which DBS works is still debated. Long-term clinical observation (Benabid et al. 2005) has shown that the mechanism is not due to a progressive lesion, given that interruption of stimulation reverses its effects. There is no current proof that long-term DBS is able to reset neural networks, or induce modifications of the functional organization/synaptic connectivity in the brain. Potential complications & side-effects Whilst DBS is undoubtedly helpful for some patients, there is also the potential for neuropsychiatric side effects. Reports in the literature describe the possibility of 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.• A recent trial of 99 Parkinson's patients who had undergone DBS suggested a decline in executive functions relative to patients who had not undergone DBS. This included problems with word generation, attention and learning. About 9% of patients had "psychiatric events", which ranged in severity to a relapse in voyeurism to a suicide attempt. However, it is worth noting that most patients in this trial reported an improvement in their quality of life following DBS, and there was an improvement in their physical functioning.• Because the brain moves slightly during surgery there is the possibility that the electrodes can become 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. 2% risk of bleeding in the brain which leads to a stroke. The stroke could be mild recovering after a few weeks/months or severe, resulting to weakness, intellectual impairment, or death. 4% risk of infection: not life threatening but the whole DBS system must be removed immediately, and after the infection recedes a new one may placed. After surgery: See also Notes | ||||||||
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