Deep brain stimulation

Deep brain stimulation (DBS) is a neurosurgical procedure involving the placement 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 disorders, including Parkinson's disease, essential tremor, and dystonia. While its underlying principles and mechanisms are not fully understood, DBS directly changes brain activity in a controlled manner. Deep brain stimulation (DBS) is a neurosurgical procedure involving the placement 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 disorders, including Parkinson's disease, essential tremor, and dystonia. While its underlying principles and mechanisms are not fully understood, DBS directly changes brain activity in a controlled manner. DBS has been approved by the Food and Drug Administration as a treatment for essential tremor and Parkinson's disease (PD) since 1997. DBS was approved for dystonia in 2003, obsessive–compulsive disorder (OCD) in 2009, and epilepsy in 2018. DBS has been studied in clinical trials as a potential treatment for chronic pain for various affective disorders, including major depression; it is one of only a few neurosurgical methods that allow blinded studies. DBS is used to manage some of the symptoms of Parkinson's Disease that cannot be adequately controlled with medications. It is recommended for people who have PD with motor fluctuations and tremor inadequately controlled by medication, or to those who are intolerant to medication, as long as they do not have severe neuropsychiatric problems. Four areas of the brain have been treated with neural stimulators in PD. These are the globus pallidus internus, thalamus, subthalamic nucleus and the pedunculopontine nucleus. DBS of the globus pallidus internus improves motor function while DBS of the thalamic DBS improves tremor but has little effect on bradykinesia or rigidity. DBS of the subthalamic nucleus is usually avoided if a history of depression or neurocognitive impairment is present. DBS of the subthalamic nucleus is associated with reduction in medication. Pedunculopontine nucleus DBS remains experimental at present. Generally DBS is associated with 30–60% improvement in motor score evaluations. 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 people with TS had 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 person. 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 for people with 'severe functional impairment that cannot be managed medically'. 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%). The potential exists for neuropsychiatric side effects after DBS, 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.