Deep brain stimulation
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In neurotechnology, deep brain stimulation (DBS) is a surgical treatment involving the implantation of a medical device called a brain pacemaker, which sends electrical impulses to specific parts of the brain. DBS was approved by the Food and Drug Administration (FDA) in 1997 as a treatment for Parkinson's disease as well as essential tremor,<ref name=USDHHS>U.S. Department of Health and Human Services.FDA APPROVES IMPLANTED BRAIN STIMULATOR TO CONTROL TREMORS. Retrieved October 18, 2006.</ref> and in April 2003 as a treatment for dystonia.<ref> 'Brain pacemaker' treats dystonia. KNBC TV, April 22, 2003. Retrieved October 18, 2006.</ref> DBS may also alleviate symptoms in treatment-resistant clinical depression,<ref>Brain stimulation may treat resistant depression. CTV.ca, March 1, 2005. Retrieved October 18, 2006.</ref> and has been used experimentally in the treatment of other conditions. While DBS is helpful for some patients, there is potential for serious complications and side effects.
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[edit] Components and placement
The deep brain stimulation system consists of three components: the implanted pulse generator (IPG), the lead, and the extension. The IPG is a battery powered neurostimulator encased in a titanium housing, which sends electrical pulses to the brain to interfere with neural activity at the target site. The lead is a coiled wire insulated in polyurethane with four platinum iridium electrodes, which is placed in one of three areas of the brain. The lead is connected to the IPG by the extension, an insulated wire that runs from the head, down the side of the neck, behind the ear to the IPG, which is placed subcutaneously below the clavicle or in some cases, the abdomen.<ref name=NINDS>National Institute of Neurological Disorders and Stroke. Deep brain stimulation for Parkinson's Disease information page. Retrieved 23 November 2006.</ref> The IPG can be calibrated by a neurologist, nurse or trained technician to optimize symptom suppression and control side effects.[citation needed]
DBS leads are placed in the brain according to the type of symptoms to be addressed. For essential tremor and Parkinsonian tremors, the lead is placed in the thalamus.<ref>Activa Tremor Control Therapy. Medtronic, Inc. Retrieved November 20, 2006.</ref> 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.<ref>Activa Parkinson's Control Therapy. Medtronic, Inc. Retrieved November 20, 2006.</ref><ref>Activa Dystonia Therapy. Medtronic, Inc. Retrieved November 20, 2006.</ref>
All three components are surgically implanted inside the body. The right side of the brain is stimulated to address symptoms on the left side of the body and vice versa.
[edit] Procedure
Image:Parkinson surgery.jpgThe procedure begins with the neurosurgeon mapping the selected target within the basal ganglia through computed tomography and magnetic resonance imaging.During surgery, the patient is given local anesthesia and remains awake. A craniotomy is performed and a DBS lead is placed either unilaterlly or bilaterally, depending on the patient's symptoms. Microelectrode recording may be used to more precisely locate the desired target within the brain. The IPG and extension are then implanted and connected to each lead.
Depending on the procedures of the medical facility, all components of the DBS system may not be implanted during a single surgery. After surgery is completed, the IPG is calibrated to maximize its effectiveness. Programming can take up to a year to achieve optimal settings.
Due to battery depletion, the IPG must be replaced—usually after three to five years, depending on the settings used. The entire unit is replaced to maintain an uncontaminated field within the body. Nevertheless, this is a minor surgical procedure involving only the shallow subclavicular pocket where the IPG 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.
[edit] Parkinson's disease
Parkinson's disease is a common neurodegenerative disease 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.[citation needed] At present, the procedure is used only for patients whose symptoms cannot be adequately controlled with medications.<ref name=NINDS/>
DBS is approved in the United States by the Food and Drug Administration for the treatment of Parkinson's.<ref name=USDHHS/> DBS carries the risks of major surgery, with a complication rate related to the experience of the surgical team.
[edit] Clinical depression
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 clinical depression, whose symptoms had previously been resistant to medication, psychotherapy and electroconvulsive therapy.<ref name=Mayberg>Mayberg HS, Lozano AM, Voon V, McNeely HE, Seminowicz D, Hamani C, Schwalb JM, Kennedy SH. Deep brain stimulation for treatment-resistant depression. Neuron. 2005 Mar 3;45(5):651-60. PMID 15748841.</ref>
Using brain imaging, the reserchers 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.<ref name=Mayberg/>
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.<ref name=Mayberg/>
[edit] 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.<ref>Tourette Syndrome Association. Statement on DBS. Retrieved October 16, 2006.</ref> 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".<ref name=Malone>Malone DA Jr, Pandya MM. Behavioral neurosurgery. Adv Neurol. 2006;99:241-7. PMID 16536372</ref> There are currently five reports 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."<ref name=Malone/> 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.<ref>Mink JW, Walkup J, Frey KA, et al. Patient selection and assessment recommendations for deep brain stimulation in Tourette syndrome. Mov Disord. 2006 Sep 21. PMID 16991144</ref>
[edit] Other clinical applications
DBS has been used in the treatment of obsessive-compulsive disorder,<ref>Nuttin B, Cosyns P, Demeulemeester H, Gybels J, Meyerson B (1999) Electrical stimulation in anterior limbs of internal capsules in patients with obsessive-compulsive disorder. Lancet. 1999 Oct 30;354(9189):1526 PMID 10551504</ref> cluster headaches,[citation needed] and obesity.[citation needed] Although the clinical efficacy is not questioned, the mechanisms by which DBS works is still debated.<ref name=Benabid>Benabid AL, Wallace B, Mitrofanis J, Xia R, Piallat B, Chabardes S, Berger F. (2005) A putative generalized model of the effects and mechanism of action of high frequency electrical stimulation of the central nervous system. Acta Neurol Belg. 2005 Sep;105(3):149-57. PMID 16255153</ref> Long-term clinical observation has shown that the mechanism is not due to a progressive lesion, given that interruption of stimulation reverses its effects.<ref name=Benabid/> 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.<ref>Krauss JK (2002). "Deep brain stimulation for dystonia in adults. Overview and developments". Stereotactic and Functional Neurosurgery 78 (3-4): 168-182. PMID 12652041.</ref>
[edit] Potential complications and side effects
While DBS is 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.<ref>Burn D, Troster A (2004). "Neuropsychiatric Complications of Medical and Surgical Therapies for Parkinson's Disease.". Journal of Geriatric Psychiatry and Neurology 17 (3): 172-180. PMID 15312281.</ref> 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, including problems with word generation, attention and learning. About 9% of patients had "psychiatric events", which ranged in severity from a relapse in voyeurism to a suicide attempt. Most patients in this trial reported an improvement in their quality of life following DBS, and there was an improvement in their physical functioning.<ref>Smeding H, Speelman J, Koning-Haanstra M, et al (2006). "Neuropsychological effects of bilateral STN stimulation in Parkinson disease: A controlled study". Neurology 66 (12): 1830-1836. PMID 16801645.</ref>
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.
There is a 2% risk of bleeding in the brain which can lead to a stroke. The stroke could result in weakness, intellectual impairment, or death. There is a 4% risk of infection: not life threatening but necessitating immediate removal of the DBS system;[citation needed] after the infection recedes. a new one may placed.
After surgery:
- swelling of the brain tissue is normal
- mild disorientation, sleepiness
- personality change which recedes after 1-2 week[verification needed]
- follow up after 2-4 weeks to remove sutures, turn on the neurostimulator and program it
[edit] See also
- Neurosurgery
- Stereotactic surgery
- Psychosurgery
- Neuroprosthetics
- Brain implant
- Vagus nerve stimulation
[edit] Notes
[edit] References
- McIntyre CC, Grill WM (2000) Selective microstimulation of central nervous system neurons. Annals of Biomedical Engineering 38:219-233. PMID 10784087
- McIntyre CC, Grill WM, Sherman DL, Thakor NV (2004) Cellular effects of deep brain stimulation: model-based analysis of activation and inhibition. Journal of Neurophysiology 91:1457–1469. PMID 14668299
