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.