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Deep Brain Stimulation and How DBS-STN Works

DBS-STN staff

One of the most exciting neurosurgical advances has been the use of electrical stimulation of specific parts of the brain to treat a variety of disabling conditions. These brain stimulation procedures represent a revolutionary new frontier in neurosurgery. Previous neurosurgical procedures employed the destruction or removal of brain tissue. Brain stimulation allows physicians to augment, modulate, and even improve brain function without destroying any area f the brain. Currently, the most common use of brain stimulation is in patients with debilitating movement disorders including essential tremor and Parkinson's disease. Introduced in the late 1980s by Dr Benabid and colleagues in France, DBS is a surgical procedure consisting of the placement of an electrode into one of several possible targets in the brain aided by computer guidance and 3-D physiological mapping. Each electrode has four contact points which is connected to a thin, insulated wire that is threaded under the skin from the top of the skull to the chest. That wire leads to a battery-operated pulse generator (like that used in a pacemaker), which then is implanted beneath the skin in the chest. The electrodes send mild electrical pulses to stimulate the brain and block the signals that cause. High frequency electrical stimulation is believed to "jam" the signals, normal or abnormal, emanating from the brain site. Stimulation therefore has the same outward effect of a lesion but, unlike a permanent lesion, the effect is reversible. Turn the stimulator off and within minutes to hours, the structure begins to function as it had prior to stimulation. Thus, if stimulation yields unwanted side effects, the stimulator may be turned off or repositioned. The surgical placement of the electrodes determines their effect, so that they may treat tremor alone (which is all that is needed for a patient with essential tremor), or they may address the range of debilitating symptoms experienced by Parkinson's patients. Surgeons may recommend the application of DBS to one of three areas of the brain: the thalamus, the subthalamic nucleus, or the globus pallidus. 1. Thalamic Stimulation, electrical stimulation applied to the thalamus, eliminates tremor in more than 80 percent of patients. Most people experience almost complete relief from tremor on the side of the body that corresponds to the stimulation. A small number of patients, however, may receive no benefit. 2. Subthalamic Nucleus Stimulation (STN) is the most promising of the surgical procedures for Parkinson's disease. Most often it is done bi-laterally (on each side) and it is used to treat not only tremor, but also all of the cardinal symptoms of Parkinson1s disease. In addition, it can virtually eliminate the side effects often caused by the long-term use of anti-parkinsonian drugs. On average, patients can cut their medication dosages in half thereby eliminating the terrible dyskinesias. 3. Globus Pallidal Stimulation. When a patient has already had a unilateral pallidotomy (pallidotomy on one side of the brain), but continues to have dyskinesias on both sides of the body, the surgeon may recommend stimulation of the globus pallidus with a deep brain stimulator. This is a conservative alternative to a bilateral pallidotomy (pallidotomy on both sides of the brain), which destroys brain tissue and risks the permanent impairment of cognition and language function. The major advantage of DBS-STN over the traditional lesioning procedures is that DBS-STN is reversible and adjustable. DBS-STN causes no destruction of brain tissue and the stimulator can be adjusted, minimized, turned off or even removed if there are untoward side effects. The second major advantage of DBS-STN is that it is adjustable or programmable, allowing the stimulation level to be altered to achieve continuing improvement of their symptoms. For example, if a patient develops increasing rigidity, bradykinesia, or tremor some time after DBS-STN surgery, the stimulation can be modified to achieve better clinical effects, which is not possible with lesioning procedures. In short, deep brain stimulation technology allows for the optimal scenario in which we can maximize clinical outcome while minimizing complications.



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