For several years now, Gertrud (58) has had problems holding the spoon without the whole soup sloshing away. She also had problems walking and without a walker she might hardly make any progress. Her feet don’t seem to obey her anymore. Gertrud has Parkinson’s. Tremors, hesitant movement, and stiff muscles are symptoms of Parkinson’s disease, an insidious neurodegenerative disease that can be traced back to the death of dopamine-producing neurons in the substantia nigra in the midbrain (1). She is given medication, but the tremors and unsteady gait did not improve.
Her doctors suggested a new treatment method, which, however, requires an operation. She agreed. She had small electrodes placed in her head that “stimulate” her brain.
A few days following the operation, the tremors had improved significantly and following a few months she was able to walk once more without any problems.
Gertrud benefits from the treatment called Deep Brain Stimulation.
Was ist Deep Brain Stimulation?
In deep brain stimulation (DBS), or deep brain stimulation, electrodes are implanted in the brain. These electrodes deliver high-frequency electrical pulses to brain structures. They work like pacemakers in the brain. A battery is then inserted under the skin in the chest area.
For the treatment of Parkinson’s, nuclei in the thalamus are usually controlled and modulated. The thalamus regulates, among other things, both sensory and motor signals. Electrodes, which are intended to act in the region of the ventricular intermedius nucleus, reduce tremors in patients with Parkinson’s disease. In other regions, such as the subthalamic nucleus (STN) or the globus pallidus internus (GPi), stimulation can not only reduce tremors, but also bradykinesia (hesitation and halting in movements (1,2)) and stiffness.
At present, DBS is still most commonly used in Parkinson’s patients.
What happens in the brain?
How DBS works at the cellular and molecular level is still a matter of debate. DBS was initially thought to block parts of brain structures. However, this approach does not seem entirely correct. Other studies report stimulation of nerve cells. This is supported, among other things, by the increased release of some neurotransmitters.
Another approach is that DBS can have both an activating and an inhibitory (blocking) effect. The soma (cell body) is electrically “separated” from the axon. The soma is inhibited and thus silences afferents (incoming signals), while the axon is stimulating.
These contrasting approaches to exactly how DBS works prompts further study. Many different ideas and variables will be examined: Which neurotransmitters are released? How long does it take from stimulation (or modulation) to the effect? And many more questions are the subject of ongoing investigations (3).
Where is the future going?
So far, network theories, i.e. which parts of the brain communicate a lot with other parts, might be set up with the help of DBS. Areas that communicate with each other influence, for example, movement processes or decision-making. Such insights might only be gained because very localized changes in the brain, which are possible with small electrodes, can affect the entire central nervous system. In addition, the small electrodes allow direct interaction with the relevant network in the brain and the parameters of the electrode can be adjusted in such a way that the optimum can be achieved for the patient.
Nonetheless, DBS is a surgical procedure that comes with risks such as post-operative bleeding and infection.
In the scientific field, DBS is used to investigate the physiological basis of dysfunctions in the brain and thus to treat pathological neurological processes in the future.
There are indications that DBS can be used not only for motor diseases such as Parkinson’s, but also for mental illnesses such as severe depression, obsessive-compulsive disorders or bipolar disorders. However, the data is still too sparse to use DBS safely and successfully in such clinical pictures. Further studies are being carried out on this. (4)
Disclaimer: Gertrud is a fictional character. The symptoms that people with Parkinson’s disease experience and the treatment that hundreds of thousands of people have undergone are real.
Sources
1. Bradykinesia (Slowness of Movement) | Parkinson’s Foundation [Internet]. [cited 2022 Aug 30]. Available from: https://www.parkinson.org/understanding-parkinsons/symptoms/movement-symptoms/bradykinesia#:~:text=Bradykinesia%20means%20slowness%20of%20movement,Parkinson%27s%20diagnosis%20to%20be%20considered.
2. Parkinson’s disease – DPG e. V [Internet]. [cited 2022 Aug 31]. Available from: https://parkinson-gesellschaft.de/fuer-betroffene/die-parkinson-krankheit?dpg/spende
3. Lozano AM, Lipsman N. Probing and Regulating Dysfunctional Circuits Using Deep Brain Stimulation. Neuron [Internet]. 2013 Feb 6 [cited 2022 Aug 30];77(3):406–24. Available from: http://www.cell.com/article/S089662731300086X/fulltext
4. Lozano AM, Lipsman N, Bergman H, Brown P, Chabardes S, Chang JW, et al. Deep brain stimulation: current challenges and future directions. Nature Reviews Neurology 2019 15:3 [Internet]. 2019 Jan 25 [cited 2022 Aug 26];15(3):148–60. Available from: https://www.nature.com/articles/s41582-018-0128-2
