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 in select brain regions has provided remarkable therapeutic benefits for otherwise treatment-resistant movement and affective disorders such as chronic pain, Parkinson’s disease, tremor and dystonia [1]. Yet, despite the long history of DBS [2], 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 is one of only a few neurosurgical methods that allows blinded studies.
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 clinical depression. 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 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. 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 essential tremor and Parkinsonian tremors, the lead is placed in 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. The right side of the brain is stimulated to address symptoms on the left side of the body and vice versa.
Procedure
The procedure begins with preoperative identification of the neurosurgical target with computed tomography (CT), magnetic resonance imaging (MRI) or in earlier times ventriculography.[9]
During surgery, the patient is given local anesthesia and remains awake. A craniotomy is performed and a DBS lead is placed either unilaterally 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.
Parkinson's disease
Parkinson's disease is a disorder that affects nerve cells, or neurons, in a part of the brain that controls muscle movement. In Parkinson's, neurons that make a chemical called dopamine die or do not work properly. Dopamine normally sends signals that help coordinate your movements. No one knows what damages these cells. Symptoms of Parkinson's disease may include
- Trembling of hands, arms, legs, jaw and face
- Stiffness of the arms, legs and trunk
- Slowness of movement
- Poor balance and coordination
As symptoms get worse, people with the disease may have trouble walking, talking or doing simple tasks. They may also have problems such as depression, sleep problems or trouble chewing, swallowing or speaking.
Parkinson's usually begins around age 60, but it can start earlier. It is more common in men than in women. There is no cure for Parkinson's disease. A variety of medicines sometimes help symptoms dramatically.
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