By Sophia Reiner
Introduction
It’s the mid-20th century. You’ve been rendered unconscious by the lovely sounding “electro-shock” machine, with the last thing you see before darkness being the white walls of a mental institute. During your slumber, instruments resembling ice picks are shoved through the back of your eye socket and through the thin bone separating the socket from the frontal lobe. In the span of roughly 10 minutes, a hammer is used to tap to handle of the ice picks to cut and scrape away white nerve fibre connections in the brain (Terrier et al., 2019). You wake up and may notice personality changes, epilepsy (Miller, 1967), seizures, cognitive impairment (Healthline, 2022), and more; however, you’re told that you’re lucky that your mental illnesses weren’t severe enough for the surgery to have required drilling holes into your head. Welcome to the rest of your lobotomised life!
These lobotomies, developed firstly by António Egas Moniz (who won a Nobel Prize for his contribution), and modernised by Walter Freeman, created a stigma against psychosurgeries (BBC, 2021; Neumaier et al., 2017). However, the introduction and popularisation of lobotomies were significant in developing safer psychosurgery options. This led to the development of deep brain stimulation (DBS), a neurosurgical treatment through the transmission of electrical impulses to neurological sites; this treatment, like lobotomies, is utilised to regulate chemical imbalances found in movement and mental disorders (American Association of Neurological Surgeons).
In application, DBS takes place as intracranial electrodes are inserted into the brain, after which a neurostimulator (which transports electric currents) is implanted under the skin, with an extension wire connecting the two structures. Additionally, to the internal systems that are stimulated with high frequencies, the external hardware is comprised of a transmitter carried by the patient (National Library of Medicine; Krauss et al., 2020). While the exact underlying mechanisms in DBS are still unknown, Orlando De Jesus of the Neurosurgery Section at the University of Puerto Rico and colleagues (2022) contend that the electrodes deeply placed in the brain, upon activation, either “stimulat[es] or inhibit[es] neurons and fiber pathways that will subsequently allow neurochemical release.” In other words, the specific brain location responsible for each particular disorder is stimulated by electric pulses from the neurostimulator, resulting in a chemical readjustment and alleviation of neurological disorders.
Through analysing various viewpoints, this article will conclude that despite the potential complications, deep brain stimulation is an effective treatment option for both movement and psychiatric disorders.
Impacts on Movement Disorders
Deep brain stimulation is an FDA-approved treatment for Parkinson’s, essential tremors, and epilepsy that treats the physical aspects of neurological disorders.
Firstly, Parkinson’s (PD) is a “progressive neurodegenerative disorder,” in which a “loss of neuronal dopamine production in the brain” leads to uncontrollable movements such as an asymmetric resting tremor (asymmetric tremor upon muscle relaxation), bradykinesia (slowed movements), and postural instability (inability to maintain balance/equilibrium) (Fang & Tolleson, 2017). While the first step of Parkinson’s treatment is not DBS but rather pharmacological therapies, Fang and Tolleson (2017) of the Vanderbilt University Medical Center explain the limitations of medications in that “frequent dosing [is required] to avoid the return of symptom.” As a result of these challenges, DBS is FDA approved in select DBS patients (Fang & Tolleson, 2017).
In particular, Schuurman et al. (2000) have discovered that in comparison to treating Parkinson’s with a thalamotomy (in which part of the thalamus is destroyed to treat tremours), DBS of the thalamus has a stronger “functional outcome.” Unlike this treatment with a similar execution to the renounced lobotomy, DBS does not cause permanent impairments.
Beyond this, Mark Hallet and Werner Poewe (2008) of the National Institutes of Health and the University Hospital of Innsbruck, respectively, state that DBS of the subthalamic nucleus (which has the primary function of regulating movement) is the most effective neural location. The reasons for this are due to DBS in this region being effective on the fundamental symptoms, reducing side effects of the pharmacological treatments, and having low energy consumption (Hallet & Poewe, 2008).
Additionally, in terms of epilepsy, 30% of adults with epilepsy are unable to control their seizures with anti-epileptic drugs, becoming candidates for neurostimulation instead (Zangiabadi et al., 2019).
Overall, the use of DBS on Parkinson’s patients indicates that as a last resort, electrodes to the subthalamic nucleus have been the most effective treatment viable – similar to the benefits demonstrated in epilepsy.
Impacts on Psychological Disorders
In addition to movement disorders, other disorders centred in the brain benefit from deep brain stimulation: psychological disorders. The challenges of pharmacotherapy previously described for Parkinson’s also apply to mental illnesses, as medications for disorders such as schizophrenia, depression, and obsessive-compulsive can lead to “patients becom[ing] refractory [resistant] and will not respond to pharmacologic treatments” (De Jesus et al., 2022) As clinicians have begun evaluating neurosurgical procedures as a final alternative treatment, neuromodulation surgeries have thus gained a larger demographic.
Luka Liebrand of the University of Amsterdam and others (2021) have analysed the use of DBS in treating OCD: 60% of treatment-resistant individuals with OCD respond positively to DBS. Essentially, DBS usage is controlled and offered only when other options are exhausted and has a higher success rate. However, Liebrand (2021) also found that individuals with a larger nucleus accumbens (which works as the “neural interface between motivation and action” (Fernández-Espejo)) volume have a more successful response to DBS treatment. The reason for this has been hypothesised to be because the electrodes placed in the brain in the larger nucleus accumbens were “closer to the relevant white matter structures” (Liebrand, 2021). While this indicates that drastic improvements as a result of DBS may not be available for entire populations, it provides a guideline for future treatment applications, and optimise the response rate to such treatments.
Furthermore, treatment-resistant depression has been found to have rapid benefits from DBS treatment (50% reduction on a depression rating scale after a week), according to Thomas Schlaepfer and colleagues from the University Hospital Bonn. In accordance, a study reviewing past trials of DBS applied to different parts of the brain to treat treatment-resistant depression has found the “response and remission rates were respectively 56 and 32%” (Wu et al.). This explains that even without a particular location, deep brain stimulation is significant in treating or at least alleviating the symptoms of OCD.
In essence, the evidence for treating OCD and treatment-resistant depression proves that despite the negative perception of psychosurgeries, deep brain stimulation has been able to break barriers and improve psychological symptoms.
Complications of DBS Surgery
Complications of deep brain stimulation can take place in each step of the procedure: during the surgery, as well as during the conclusive effect of the treatment. Firstly, a brain shift could occur during the surgery through the loss of cerebro-spinal fluid (which acts as a cover for the brain) (Slotty et al.); this loss of fluid occurs mostly at the beginning of the surgery as burr holes can be used to balance the intracranial air (Slotty et al). However, after awakening from the surgery, “DBS requires long-term maintenance for proper functioning” forcing challenges in being cautious after the procedure (Fang & Tolleson, 2017).
In addition, hardware complications can also be present, which include “battery failure, problems with the wires, or misplaced electrodes” (Parkinson Alliance). The detrimental effects of this include the cardinal sign of a sudden onset “significant tremor” and other forms of increased disease progression (Farris et al.). However, in a group of 466 patients, 8.1% were found to have impacted motor function skills as a result of hardware problems (Farris et al.). While this is not a significant sized percentage, caution must still be exercised to maintain the efficacy of DBS. In a demonstration of DBS being a successful procedure, Dr. Michael Okun of the University of Florida and more concluded that “51% of patients who complained of “failed” DBS procedures ultimately had good outcomes,” showing a half chance opportunity to reverse any mistakes presented.
To focus on specific disorders, in Parkinson’s disease, while movement difficulty can be subsided, DBS can also cause “worse cognition, impaired verbal fluency, depression, cerebral hemorrhage, stroke, and infection among others” (Fang & Tolleson, 2017).
Regarding depression, side effects of infections, headaches, mood changes, and potentially suicidal ideation (only 13%) can also be caused (Moreins et al., 2011). Further emotional changes have been proven in depressed patients who have undergone DBS treatments, as Katherine W. Scangos of the University of California, San Fransisco and colleagues have found. Distinctive emotional changes were found immediately after as patients gained a calmed pleasure or felt excessively drowsy (Scangos et al.).
Together, this states that many types of complications can be resulted from DBS treatment, creating more of a debate as to whether the use of DBS is consistently effective.
Conclusion
Overall, due to the benefits deep brain stimulation has in treating movement and mind disorders that would not otherwise be successfully treated, DBS is an effective treatment option despite current complications. In summary of the previous arguments, the insertion of electrodes that then have an electric current passing through to specialised neural areas has been found to rebalance the chemicals and remove symptoms from neurological-based disorders. However, in addressing the issue of complications, the explained half per cent chance of reversing complications and the strict regulations that only individuals in treatment-resistance disorders are allowed to use DBS as a treatment both demonstrate medical ethics and ensure the non-maleficence and beneficence are both fulfilled.
In finality, as DBS is an ongoing neurosurgical intervention, it has the opportunity to strengthen neurosurgery and reintroduce psychosurgery as a treatment for disorders which do not benefit from pharmacological medications; deep brain stimulation is helping the world continue to make advancements in medicine – standing up to previously deteriorative disorders.
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