Deep brain stimulation (DBS) is a neurosurgical procedure involving the implantation of a medical device called a neurostimulator (sometimes referred to as a 'brain pacemaker'), which sends electrical impulses, through implanted electrodes, to specific targets in the brain (brain nuclei) for the treatment of movement and neuropsychiatric disorders. DBS in select brain regions has provided therapeutic benefits for otherwise treatment-resistant disorders such as Parkinson's disease, essential tremor, dystonia, chronic pain, major depression, and obsessive-compulsive disorder. 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.
The Food and Drug Administration approved DBS as a treatment for essential tremor and Parkinson's disease (PD) in 1997, dystonia in 2003, and obsessive-compulsive disorder (OCD) in 2009. DBS is also used in research studies to treat chronic pain, PTSD, and has been used to treat various affective disorders, including major depression; none of these applications of DBS has yet been FDA-approved. While DBS has proven to be effective for some patients, the potential for serious complications and side effects exists.
Video Deep brain stimulation
Components and placement
The DBS system consists of three components: the implanted pulse generator (IPG), the lead, and an extension. The IPG is a battery-powered neurostimulator encased in a titanium housing, which sends electrical pulses to the brain that interfere with neural activity at the target site. The lead is a coiled wire insulated in polyurethane with four platinum-iridium electrodes and is placed in one or two different nuclei of the brain. The lead is connected to the IPG by an extension, an insulated wire that runs below the skin, 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. The IPG can be calibrated by a neurologist, nurse, or trained technician to optimize symptom suppression and control 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 either the ventrointermediate nucleus of the thalamus or the zona incerta; for dystonia and symptoms associated with PD (rigidity, bradykinesia/akinesia, and tremor), the lead may be placed in either the globus pallidus internus or the subthalamic nucleus; for OCD and depression to the nucleus accumbens; for incessant pain to the posterior thalamic region or periaqueductal gray; for Parkinson plus patients to two nuclei simultaneously, subthalamic nucleus and tegmental nucleus of pons, with the use of two pulse generators; and for epilepsy treatment to the anterior thalamic nucleus.
All three components are surgically implanted inside the body. Lead implantation may take place under local anesthesia or with the patient under general anesthesia ("asleep DBS") such as for dystonia. A hole about 14 mm in diameter is drilled in the skull and the probe electrode is inserted stereotactically. During the awake procedure with local anesthesia, feedback from the patient is used to determine the optimal placement of the permanent electrode. During the asleep procedure, intraoperative MRI guidance is used for direct visualization of brain tissue and device. The installation of the IPG and extension leads 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.
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Applications
Parkinson's disease
The use of DBS as a treatment for Parkinson's Disease (PD) dates from 1987. PD is a neurodegenerative disease whose primary symptoms are tremor, rigidity, bradykinesia, and postural instability. DBS does not cure PD, 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 directly diminish the side effects induced by PD medications, allowing a decrease in medications, or making a medication regimen more tolerable.
A few sites in the brain can be targeted to achieve differing results, so patients must be assessed individually, and a site is chosen based on their needs. Traditionally, the two most common sites are the subthalamic nucleus (STN) and the globus pallidus interna, but other sites, such as the caudal zona incerta and the pallidofugal fibers medial to the STN, are being evaluated and show promise.
In the United States, DBS is approved by the Food and Drug Administration for the treatment of PD. DBS carries the risks of major surgery, with a complication rate related to the experience of the surgical team. The major complications include hemorrhage (1-2%) and infection (3-5%).
Chronic pain
Stimulation of the periaqueductal gray and periventricular gray for nociceptive pain, and the internal capsule, ventral posterolateral nucleus, and ventral posteromedial nucleus for neuropathic pain has produced impressive results with some patients, but results vary and appropriate patient selection is important. One study of 17 patients with intractable cancer pain found that 13 were virtually pain free and only four required opioid analgesics on release from hospital after the intervention. Most ultimately did resort to opioids, usually in the last few weeks of life. DBS has also been applied for phantom limb pain.
Major depression and obsessive-compulsive disorder
DBS has been used in a small number of clinical trials to treat patients suffering from a severe form of treatment-resistant depression (TRD). A number of neuroanatomical targets have been used for DBS for TRD including the subgenual cingulate gyrus, posterior gyrus rectus, nucleus accumbens, ventral capsule/ventral striatum, inferior thalamic peduncle, and the lateral habenula. A recently proposed target of DBS intervention in depression is the superolateral branch of the medial forebrain bundle; its stimulation lead to surprisingly rapid antidepressant effects in very treatment-resistant patients.
The small patient numbers in the early trials of DBS for TRD currently limit the selection of an optimal neuroanatomical target. Evidence is insufficient to support DBS as a therapeutic modality for depression; however, the procedure may be an effective treatment modality in the future. In fact, beneficial results have been documented in the neurosurgical literature, including a few instances in which deeply depressed patients were provided with portable stimulators for self treatment.
A systematic review of DBS for TRD and OCD identified 23 cases, nine for OCD, seven for TRD, and one for both. "[A]bout half the patients did show dramatic improvement" and adverse events were "generally trivial" given the younger psychiatric patient population than with movement disorders. The first randomized, controlled study of DBS for the treatment of TRD targeting the ventral capsule/ventral striatum area did not demonstrate a significant difference in response rates between the active and sham groups at the end of a 16-week study.
DBS for TRD can be as effective as antidepressants, with good response and remission rates, but adverse effects and safety must be more fully evaluated. Common side effects include "wound infection, perioperative headache, and worsening/irritable mood [and] increased suicidality".
Tourette syndrome
DBS has been used experimentally in treating adults with severe Tourette syndrome that does not respond to conventional treatment. 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 risks. 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, five patients with TS have been reported on; all experienced reduction in tics and the disappearance of obsessive-compulsive behaviors.
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 in general this would not 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 Tourette syndrome treatment, the Tourette Association of America convened a group of experts to develop recommendations guiding the use and potential clinical trials of DBS for TS.
Robertson reported that DBS had been used on 55 adults by 2011, remained an experimental treatment at that time, and recommended that the procedure "should only be conducted by experienced functional neurosurgeons operating in centres which also have a dedicated Tourette syndrome clinic". According to Malone et al (2006), "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." Du et al (2010) say, "As an invasive therapy, DBS is currently only advisable for severely affected, treatment-refractory TS adults". Singer (2011) says, "pending determination of patient selection criteria and the outcome of carefully controlled clinical trials, a cautious approach is recommended". Viswanathan et al (2012) say DBS should be used in patients with "severe functional impairment that cannot be managed medically".
Other clinical applications
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 has been tested for effectiveness in people with epilepsy that is resistant to medication. DBS may reduce or eliminate epileptic seizures with programmed or responsive stimulation.
DBS of the septal areas of persons with schizophrenia have resulted in enhanced alertness, cooperation, and euphoria. Persons with narcolepsy and complex-partial seizures also reported euphoria and sexual thoughts from self-elicited DBS of the septal nuclei.
Orgasmic ecstasy was reported with the electrical stimulation of the brain with depth electrodes in the left hippocampus at 3mA, and the right hippocampus at 1 mA.
Adverse effects
While DBS is helpful for some patients, the potential also exists for neuropsychiatric side effects, including apathy, hallucinations, hypersexuality, cognitive dysfunction, depression, and euphoria. However, these may be temporary and related to correct placement of electrodes and calibration of the stimulator, so these side effects are potentially reversible.
Because the brain can shift slightly during surgery, the electrodes can become displaced or dislodged from the specific location. This may cause more profound complications such as personality changes, but electrode misplacement is relatively easy to identify using CT. Also, complications of surgery may occur, such as bleeding within the brain. After surgery, swelling of the brain tissue, mild disorientation, and sleepiness are normal. After 2-4 weeks, a follow-up visit is used to remove sutures, turn on the neurostimulator, and program it.
As with all surgery, a risk exists 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.
Mechanisms
The exact mechanism of action of DBS is not known. A variety of hypotheses try to explain the mechanisms of DBS:
- Depolarization blockade: Electrical currents block the neuronal output at or near the electrode site.
- Synaptic inhibition: This causes an indirect regulation of the neuronal output by activating axon terminals with synaptic connections to neurons near the stimulating electrode.
- Desynchronization of abnormal oscillatory activity of neurons
- Antidromic activation either activating/blockading distant neurons or blockading slow axons
DBS represents an advance on previous treatments which involved pallidotomy (i.e., surgical ablation of the globus pallidus) or thalamotomy (i.e., surgical ablation of the thalamus). Instead, a thin lead with multiple electrodes is implanted in the globus pallidus, nucleus ventralis intermedius thalami, or subthalamic nucleus, and electric pulses are used therapeutically. The lead from the implant is extended to the neurostimulator under the skin in the chest area.
Recent developments
In 2015, a group of Brazilian researchers led by neurosurgeon Dr. Erich Fonoff described a new technique that allows for simultaneous implants of electrodes called bilateral stereotactic procedure for DBS. The main benefits are less time spent on the procedure and greater accuracy.
Forniceal DBS was found to improve learning and memory in a mouse model of Rett syndrome . More recent work showed, that DBS upregulates genes involved in synaptic function, cell survival, and neurogenesis, making some first steps at explaining the restoration of hippocampal circuit function.
See also
References
Further reading
- Appleby BS, Duggan PS, Regenberg A, Rabins PV (2007). "Psychiatric and neuropsychiatric adverse events associated with deep brain stimulation: A meta-analysis of ten years' experience". Movement Disorders. 22 (12): 1722-1728. doi:10.1002/mds.21551. PMID 17721929.
- Gildenberg Philip L (2005). "Evolution of neuromodulation". Stereotact Funct Neurosurg. 83 (2-3): 71-79. doi:10.1159/000086865. PMID 16006778.
- Kringelbach ML, Jenkinson N, Owen SL, Aziz TZ (2007). "Translational principles of deep brain stimulation". Nature Reviews Neuroscience. 8 (8): 623-635. doi:10.1038/nrn2196. PMID 17637800.
- Schlaepfer TE, Bewernick BH, Kayser S, Hurlemann R, Coenen VA (2014). "Deep Brain Stimulation of the Human Reward System for Major Depression--Rationale, Outcomes and Outlook". Neuropsychopharmacology. 39 (6): 1303-1314. doi:10.1038/npp.2014.28. PMC 3988559 . PMID 24513970.
- Diamond A, Shahed J, Azher S, Dat-Vuong K, Jankovic J (May 2006). "Globus pallidus deep brain stimulation in dystonia". Mov. Disord. 21 (5): 692-5. doi:10.1002/mds.20767. PMID 16342255.
- Richter E.O.; Lozano A.M. (2004). "Deep Brain Stimulation for Parkinson's Disease in Movement Disorders". In Markov, Marko; Paul J. Rosch. Bioelectromagnetic medicine. New York, N.Y: Marcel Dekker. pp. 265-76. ISBN 0-8247-4700-3.
External links
- Video: Deep brain stimulation to treat Parkinson's disease
- Video: Deep brain stimulation therapy for Parkinson's disease
- The Perils of Deep Brain Stimulation for Depression. Author Danielle Egan. September 24, 2015.
Source of article : Wikipedia
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