Definition

Deep brain stimulation therapy is a technique designed to alleviate the symptoms of Parkinson's disease using two electrodes implanted in the brain and a battery implanted near the collarbone. Neurosurgeons implant an electrode in an area of the brain called the subthalamic nucleus. This region plays a close role with the basal ganglia, the area of the brain most impaired by the deteriorating effects of Parkinson's disease. The cause of Parkinson's disease is as of yet unknown.

The Subthalamic Nucleus' Role in Parkinson's Disease

The subthalamic nucleus, as the name suggests, is the "bottom" (or ventral) part of the thalamus. It is critical in the distribution of dopamine to other parts of the brain. When Parkinson's disease takes hold, as it does in nearly one percent of the American population, many parts of the basal ganglia begin to experience abnormal electrical activity, as does the subthalamic nucleus. This unpredictable and ineffectual electrical commotion is the precursor for behavior typical of the disease. Patients inflicted with Parkinson's disease can expect to experience tremor, ataxia, micrographia, limb parasthesias, and later dysphagia, dyspnea, and dementia*.

Later onset depression also occurs in 40% of Americans with Parkinson's disease. Although one might assume that the depression results from the debilitating state of Parkinson's disease, results indicate no correlation between depression and the progression of the disease. Instead, the disruption of dopaminergic pathways is variable among patients. Dopamine plays a critical role in depression, as well as being a critical component of several cortical functions.

The Procedure

Surgeons implant one electrode into the STN at a time, with a few weeks in-between for recovery and testing. To reach the STN, surgeons create a small hole in the back of the skull. Through this hole, a permanent wire connects the electrode to a battery placed near the collar bone. The entire biomechanical unit costs around $8,000. After recovery, physicians tune the electrode's voltage to maximize the effectiveness of the device. If all works well, four out of five patients can expect to see a marked improvement in their motor control, thanks to a domino effect of cortical reactivation due to the stabilized electrical activity in the STN.

*Although deep brain stimulation to the STN relieves many of the motor functions impaired by Parkinson's disease, the implant does little or nothing to alleviate Parkinson's related dementia. Therefore, neurologists avoid selecting those inflicted with dementia as candidates for the procedure. Psychologists screen potential candidates for dementia beforehand.

History

Alim-Louis Benabid and Pierre Pollak from the University of Grenoble in France are responsible for developing the original design for the device, which was first built and tested by Medtronic in 1987. Canada, the European Union, and the United States all approved of the device by the mid-1990s, although few hospitals offer the procedure because of cost for specialization. In 1999, the National Institute of Health (NIH) met to discuss the technique in the Consortium on Deep Brain Stimulation for the Treatment of Parkinson's Disease and other Neurological Disorders. Their findings supported the effectiveness of the implant and advised its continued availability.


Refernces:

http://www.medtronic.com/UK/patients/neuro/brain_stimulation.html
http://grants1.nih.gov/grants/guide/rfa-files/RFA-NS-99-006.html

Deep brain stimulation of the subthalamic nucleus in PD: an analysis of the exclusion causes. Lopiano L, Rizzone M. J Neurol Sci. 2002 Mar 30;195(2):167-70.

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