Deep Brain Stimulation in Parkinson's Disease

Parkinson's Disease is the second most common neurodegenerative illness affecting 1 in 1,000 over the age of 55, and 1 in 100 over the age of 65.  Parkinson's disease is diagnosed by four cardinal features, which include tremor, rigidity, bradykinesia (which is the slow ability to start and continue movements), and postural instability.  Patients with parkinson's disease also experience non-motor symptoms such as depression, fatigue, anxiety and pain. Fatigue is one of the most disabling because it affects half of this population, it is difficult to asses, and there are no available treatments.

Deep Brain Stimulation (DBS) involves the implantation of thin electrodes in the brain, to stimulate certain brain regions with electrical impulses.  Figure 1 below shows the areas of the brain that are stimulated by DBS, these are the Thalamus (VIM), Subthalamic Nucleus (STN), and the Globus Pallidus (GPI).  DBS is most commonly performed as a last resort when the patient no longer responds to medications.  Medications such as Sinemet may cause serious side effects such as Dyskinesia (which are involuntary movements) when taken for a long time.  For this reason its seems to be best that patients try other medications first before being on Sinemet, especially when they are diagnosed early in life.

During the surgery, the patient was awake as the electrode was implanted.  While awake, the patient was performing several tests such as the finger to nose test, and the spiral test, which tests for tremor.  The Spiral Test was performed many times during the surgery, in order for the surgeon to keep track of the electrode and the amount of stimulation needed, if the tremor improved or was completely gone then the electrode was in the correct area of the brain and was therefore providing the correct stimulation.

The sounds of neurons captured by the electrode as it was implanted were different depending on the brain region.  For example, neurons in the cortex had different sounds than neurons in the Globus Pallidus or the Thalamus, etc.  Here is an example of what neurons sound like Sounds of Neurons, in the beginning of this youtube video, you can see the electrode in a specific brain region.  At this time you can hear a sound that is similar to that of popping popcorn, but this sound is actually coming from the neurons within that brain region.  At about 32 seconds of this video, action potentials start firing faster and the sound is more like a zipper.  More Sounds! The difference in sound (popping popcorn vs. zipper) in this video is due to the difference in the stimulation applied, where fast stimulation causes a different sound compared to low stimulation.  However, in deep brain stimulation, the different sounds captured by the electrode corresponds to the different areas of the brain that the electrode travels through in order to reach the brain region of interest.  Interestingly, surgeons use these sounds to make a map of where they are in the brain so that the stimulation is applied to the correct brain region.


References

Friedman JH, Brown RG, Comella C, Garber CE, Krupp LB, Lou JS, et al. Fatigue in Parkinson's disease: a review. Mov Disord. 2007; 22:297-308.

Van Hilten JJ, Weggeman M, van der Velde EA, Kerkhof GA, van Dijk JG, Roos RA. Sleep, excessive daytime sleepiness and fatigue in Parkinson's disease. J Neural Transm Park Dis Dement Sect. 1993; 5:235-44.

Friedman J, Friedman H. Fatigue in Parkinson's disease. Neurology. 1993; 43:2016-8.

Schifitto G, Friedman JH, Oakes D, Shulman L, Comella CL, Marek K, et al. Fatigue in levodopa-naive subjects with Parkinson disease. Neurology. 2008; 71:481-5. 

Types of symptoms and patients who are likely to benefit from Movement Disorder Surgery (MDS), July 22, 2010, http://motiondisorders.com/about.php

Steve Greenberg. September 28th, 2007. Deep Brain Stimulation Surgery: Hospitals in India for Parkinson’s Disease Treatment , July 22, 2010, http://www.medical-trip.com/deep-brain-stimulation-surgery—hospitals-in-india-for-parkinsons-disease-treatment/

Posted September 6, 2008. Walley or Waldo, August 2, 2010, http://www.sodahead.com/entertainment/wally-or-waldo/question-148127/?link=ibaf &imgurl=http://bokertov.typepad.com/photos/uncategorized/2007/12/15/waldo.jpg&q=Waldo%2Bbook