NRP Fall 2023. Isabel Kidd: Deep Brain Stimulation

The anticipation filled the room. Dr. Malone and the Boston Technology Representative were in the corner adjusting the settings to the deep brain stimulator prior to turning the device on. The patient sat patiently awaiting the hopeful relief from the unconscious tremor controlling their movements. Once the device was turned on, the uncontrolled fidgeting seemed to digress. Calmness and joy filled the room, as the device had worked. Dr. Malone discussed the small adjustments that could be made over time to further control their Parkinson’s symptoms. The implantation of this incredible device in a precise location in the brain granted this patient the autonomy that they had so desperately been missing. This interaction was one I viewed while shadowing Dr. Malone, a neurologist board-certified in Sleep Medicine, Electrodiagnostic Medicine, and Psychiatry & Neurology. During this clinic day, Dr. Malone was working with patients whose primary treatment was Deep Brain Stimulation. Deep Brain Stimulation (DBS) is a neurosurgical procedure that treats movement disorders associated with Parkinson’s Disease (PD), essential tremor, dystonia, and other neurological conditions.3 This procedure uses implanted electrodes and electrical stimulation to treat these disorders. The mechanism utilized by DBS is complex and targeted toward specific regions of the brain parenchyma. Although complex, Deep Brain Stimulation is promising for many kinds of disorders.

Deep Brain Stimulation induces changes in the local field potentials within the brain parenchyma due to the use of implanted electrodes. The current standard of care application of DBS targets the subthalamic nucleus, globus pallidus internus, globus pallidus externus, ventral lateral, thalamus, pedunculopontine nucleus, and the spinal cord.4 These regions of the brain intervene in movement plans and coordinate their fluidity. The implanted electrode within these brain structures redistributes charged particles (like Na+ and Cl-) throughout the extracellular space. The redistribution initiates an electric field that can manipulate the voltage sensor domains of voltage-gated sodium channels within the axonal membrane. The opening of these ion channels can lead to the generation of action potentials propagating both in the normal direction toward the axonal bouton and the cell soma. Under normal conditions, once an action potential is fired, neurons tend to repolarize and baseline equilibrium is reestablished.2 DBS utilizes high-frequency stimulation to prevent the resetting of pre-synaptic neurons, the neuronal cleft, and post-synaptic neurons. The utilization of long-term high-frequency stimulation leads to new dynamic states of equilibrium. The parameters of high-frequency stimulation can be manually adjusted to provide effective treatment while minimizing side effects for patients.

DBS has been a standard care for refractory motor circuit disorders, like Parkinson’s disease (PD), for over 30 years.2 Parkinson’s disease is caused by the impairment or death of nerve cells within the basal ganglia.5 As a result, less dopamine is produced impacting neuronal circuits within the basal ganglia and its impacted motor plans. There is currently no cure for Parkinson’s disease. Conservative treatment involves the supplementation of dopamine.2 DBS has been proven to be an effective treatment for advanced PD. The main targets for DBS in PD are the subthalamic nucleus and the globus pallidus internus. Although, DBS has its limits in treating patients with PD. Non-dopaminergic symptoms are unable to be treated with DBS and will gradually progress. Patients may come to suffer from cognitive impairment, hallucinations, dysarthria, impaired postural reflexes, freezing, and impairment of the autonomic nervous system. The cure for PD remains undiscovered but DBS has made great impacts on bodily autonomy for PD patients.

Deep Brain Stimulation (DBS) employs high-frequency stimulation targeting specific brain structures. This treatment has been utilized for refractory motor disorders for decades. DBS has a bright future that allows patients the ability to reclaim their autonomy and lives.

References

1. Alho, E., Baldermann, J., Castelo-Branco, L., & Contreras Lopez, W. (2022). Editorial: Deep brain stimulation for neuropsychiatric disorders: Current status and perspectives. Frontiers in Neurology, 13, 1029102.

2. De Bie, Rob M.A. ; Fasano, Alfonso ; Chabardes, Stephan ; Leentjens, Albert F.G. ; Temel, Yasin. (n.d.). Fundamentals and Clinics of Deep Brain Stimulation. Cham: Springer International Publishing.

3. Deep brain stimulation. (2021, August 8). Johns Hopkins Medicine. https://www.hopkinsmedicine.org/health/treatment-tests-and-therapies/deep-brain-stimulation

4. Lozano, A., Lipsman, N., Bergman, H., Brown, P., Chabardes, S., Chang, J., . . . Krauss, J. (2019). Deep brain stimulation: Current challenges and future directions. Nature Reviews. Neurology, 15(3), 148-160.

5. U.S. Department of Health and Human Services. (2022, April 14). Parkinson’s disease: Causes, symptoms, and treatments. National Institute on Aging. https://www.nia.nih.gov/health/parkinsons-disease/parkinsons-disease-causes-symptoms-and-treatments#causes