Deep Brain Stimulation
DBS is a stimulation technique which requires the surgical implantation of a neurostimulator; a battery powered device which coordinates neural interference by sending pulsed electricity through an insulated wire to an electrode. The location of the electrode(s) at the tip of each wire is generally decided on a symptomatic basis, with the help of an MRI or CT scan to identify regions of interest. After implantation, the neurostimulator functions by equilibrating areas of abnormal electrical impulse. Stimulation is constant, with level of stimulation subject to individual necessity. DBS has shown great promise in improving the quality of life in Parkinson’s patients by blocking the abnormal nerve signals that cause symptoms of disease (e.g., tremors, rigidity, bradykinesia, and postural instability).1 The exact mechanisms by which DBS affects physiological processes are still unknown, but DBS functions in some way to reset brain activity. It has recently been hypothesized that DBS works by desynchronizing firing patterns in neural circuits.2 The National Institute of Neurological Disorders and Stroke (NINDS) currently deems DBS only available for patients who are resistant to pharmacological treatments, or exhibit severe side-effects. DBS is also being explored in depression, obsessive-compulsive disorder, Tourette syndrome, and other disorders relating to motor irregularities. NINDS funded research has shown Bilateral DBS as superior to the best medical therapy at improving motor symptoms and quality of life. Other pertinent research on DBS can be found at www.clinicaltrials.gov. 
www.clinicaltrials.gov.https://www.parkinsons.org.uk/information-and-support/deep-brain-stimulation Deep Brain Stimulation
What is the criteria for DBS?
Patients are selected very carefully before a DBS surgery is performed. There is a strict criteria in determining eligibility, for those with idiopathic Parkinson’s Disease. The criteria usually excludes patients with advancing Cognitive Impairment which can be made worse with DBS and the candidate should have symptoms which stand a good chance of improvement through surgery. These can include both Motor and non motor symptoms of Parkinsons.
The side-effects of DBS:
Some possible side-effects of DBS which include: Numbness or tingling, muscle tightness of the face or arm, speech problems, balance problems, light-headedness, and unwanted mood changes (mania and depression). Other adverse effects include apathy, hallucinations, hyper-sexuality, cognitive dysfunction, depression, and euphoria.1
References:
1Burn, D. J., & Tröster, A. I. (2004). Neuropsychiatric complications of medical and surgical therapies for Parkinson’s disease. Journal of geriatric psychiatry and neurology, 17(3), 172-180.
2 Qasim, S. E., de Hemptinne, C., Swann, N. C., Miocinovic, S., Ostrem, J. L., & Starr, P. A. (2016). Electrocorticography reveals beta desynchronization in the basal ganglia-cortical loop during rest tremor in Parkinson’s disease. Neurobiology of disease, 86, 177-186.