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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 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.
The Food and Drug Administration (FDA) approved DBS as a treatment for essential tremor in 1997, for Parkinson's disease in 2002, dystonia in 2003, and obsessive-compulsive disorder (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.
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 and is placed in one or two different nuclei of the brain. The lead is connected to the IPG by the 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 the ventrointermediate 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 internus or the subthalamic nucleus, for OCD and Depression to the nucleus Accumbens, for incessantly 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 anterion 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 Distonia. A hole about 14 mm in diameter is drilled in the skull and the probe electrode is inserted stereotacticly. During the awake procedure with local anesthesia, feedback from the patient is used to determine 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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