Introduction
Once upon a time, in a lab filled with crackling electricity and bubbling potions, Dr. Frankenstein performed his infamous experiment. It was a dark, rainy, and long night for the mad scientist. Tired, yet relentless, he took two electrical wires and zapped a lightning bolt overhead his monster, who stirred to life with a groan that echoed through the stone walls.
This dystopian and horrifying novel surely turned out to be a classic read for generations to come, but it also might have inspired neurological and psychological fields to curate technologies for the greater good.
Today, we live in a world where we must hear more and more about brain disorders. But we also live in a world where a Google search is faster than a blink. So, when you read the news every morning, you quickly skim over the Science and Technology columns, holding complicated information about multiple revolutionary inventions, discoveries, and breakthroughs.
However, we all must pay attention to one such invention from these newspaper columns – Deep Brain Stimulation (DBS) – a technique that involves making small holes in the skull to implant electrodes within specific brain areas and a pacemaker-like device in the chest.
DBS is typically used to treat disorders that involve tremors and writhing body motions, such as Parkinson’s disease, epilepsy, dystonia, and Alzheimer’s disease.
Localization of brain function and the DBS electrode implantation
One of the defining principles of the brain is that it has localized functions – meaning that particular regions can be responsible for characteristic functions. For instance, in Parkinson’s disease, parts of the basal ganglia (involved in motor learning) are either under or over-stimulated. DBS of a specific ganglia would alter the abnormal electrical circuits and help stabilize the feedback loops, thus reducing symptoms.
Electrodes can typically be placed in the following areas for the commonly treated disorders: Subthalamic Nucleus (STN), Thalamus (VIM), or Globus Pallidus (GPi). Implanting an electrode in the STN is effective for treating tremors, slowness, rigidity, dystonia, and dyskinesia. This is also the most common region to treat Parkinson’s disease. Furthermore, implanting an electrode in the VIM is effective for treating tremors, and is often used to treat essential tremors. Finally, implanting an electrode in the GPi is effective for treating tremor, slowness, rigidity, dystonia, and dyskinesia. This is the most common region to treat dystonia and Parkinson’s disease.
DBS works like a pacemaker, but the electrodes are permanently implanted into the brain instead of the circulatory system. This technique requires surgically placing an electrode to a specific malfunctioning brain region. In the example of Parkinson’s, if the STN is damaged and causing uncontrollable tremors, we implant the electrode to this malfunctioning region. The electrode then delivers a low impulse of an artificial electrical current to activate the neurons in the proximal area, without damaging brain tissue and restoring motor control.
Deciding for- or against-DBS
Although DBS is generally considered to be a low-risk treatment option, it is typically considered for patients whose symptoms worsen and do not respond to medication. This is possibly because of the risks associated with surgery and the side effects of stimulation.
During surgery, there may be a misplacement of the electrodes, bleeding of the brain, stroke, infection, nausea, heart problems, or seizure. On the other hand, the side effects of stimulation may include numbness, muscle tightness, trouble with speech or balance, light-headedness, double vision, or mood changes. Nonetheless, if you do choose DBS as a treatment option, it could work like magic! You could potentially re-gain control over your motor movements and prevent symptoms from worsening.
Before undergoing such major surgery, it is essential to weigh the risks and benefits. To help you make this decision, your physician would likely order medical tests to determine if DBS is a safe and effective option for you.
Neurosurgery & chest wall surgery
Implanting a DBS system in the body typically first involves surgery on the brain. The healthcare team would fit you in a special head frame, called a stereotaxic head frame, which keeps your head still during the procedure. Then, neuroimaging techniques, such as MRI and CT scans, are used to map your brain and pinpoint the area where are the electrodes must be placed.
The electrodes will typically be placed while you are wide awake and alert. This is to test the effects of stimulation. However, no need to fear any pain; you will be given local anesthetic to numb your scalp before the procedure. What’s interesting is that your brain would not need any anesthetic because it does not have any pain receptors.
Your surgeon would then implant a thin lead wire with several electrodes at the tip. This lead wire is placed into specific areas of the brain that were mapped by the neuroimaging techniques before the first incision. The wire runs under your skin to a battery-operated pacemaker-like device called a pulse generator.
This leads us to the second part of the surgery – implanting the pulse generator under the skin of the chest, near the collarbone, and connecting wires from the brain electrodes. During this procedure, surgeons make the use of general anesthesia, which would put you to restful sleep until they complete the surgery.
Activating and living with the pulse generator
Several weeks after surgery, the pulse generator is programmed to send continuous electrical pulses to the brain. Possibly the greatest benefit of DBS is that we can control the rate of pulses by the generator using a special remote control. However, it may take as long as 4-6 months to find the optimal setting.
Depending on the condition, stimulation may be constant, or it can be turned off at night and back on during the day. These settings affect the battery life of the pulse generator. So, when the batteries are running out of energy, your surgeon will replace the generator during a quick outpatient procedure.
Citation:
Mayfield: Brain & Spine. (n.d.). Deep Brain Stimulation. Deep Brain Stimulation (DBS) for
Parkinson’s & Essential Tremor | Mayfield Brain & Spine. https://mayfieldclinic.com/pe-dbs.htm
Mayo Foundation for Medical Education and Research. (2023, September 19). Deep Brain stimulation. Mayo Clinic. https://www.mayoclinic.org/tests-procedures/deep-brain-stimulation/about/pac-
McGovern Medical School, The University of Texas. (2020, October 20). Motor cortex
(section 3, Chapter 3) neuroscience online: An electronic textbook for the
Neurosciences: Department of Neurobiology and Anatomy - the University of Texas
Medical School at Houston. Motor Cortex (Section 3, Chapter 3) Neuroscience Online:
An Electronic Textbook for the Neurosciences | Department of Neurobiology and
Anatomy - The University of Texas Medical School at Houston. https://nba.uth.tmc.edu/neuroscience/m/s3/chapter03.html
Underwood, C. F., & Parr-Brownlie, L. C. (2020a, November 3). Primary motor cortex in
parkinson’s disease: Functional changes and opportunities for neurostimulation.
Elsevier Science Direct. https://www.sciencedirect.com/science/article/pii/S0969996120304344
Underwood, C. F., & Parr-Brownlie, L. C. (2020b, November 3). Primary motor cortex in
parkinson’s disease: Functional changes and opportunities for neurostimulation.
Elsevier Science Direct. https://www.sciencedirect.com/science/article/pii/S0969996120304344 Assessed and Endorsed by the MedReport Medical Review Board