Diseases and Disorders

Transcranial Magnetic Stimulation: A Treatment for Depression

Arya Reddy


Abstract

Depression is currently one of the most common mental health disorders. Mechanism-based therapies for this condition, however, remain elusive. Repetitive transcranial magnetic stimulation (rTMS), a non-invasive technique that uses a pulsed magnetic field to induce electrical activity in the brain, is thought to be an essential therapy for depression {7}. rTMS is a new and emerging technology that utilizes magnetic waves to stimulate the brain and help people become less depressed. The treatment sends currents through a coil to create a magnetic field that affects the nerves. This article discusses the mechanisms, side effects, and the future scope of TMS treatment.


 

Depression

Depression is a mood disorder characterized by a constant feeling of sadness and lack of motivation. It changes how a person acts, perceives, and responds to stimuli and can cause a host of mental and physical symptoms. A person suffering from depression might find it challenging to carry out day-to-day tasks and may feel undue sadness, sometimes to the extent that they believe life isn't worth living {3}. Depression can vary in severity from moderate, temporary depression to extreme, long-term depression. Medical depression, also known as major depression or major depressive disorder, is a more extreme type of depression. It's not the same as sadness that might be brought about by a tragedy, such as a loved one's death or by a medical illness. Symptoms are typically severe enough to trigger difficulties in intimate relationships or everyday activities such as work, education, and social interactions {4}.

 

Current Treatments for Depression

The majority of people who have been diagnosed with depression respond well to medication and psychotherapy. A primary care physician or therapist typically prescribes medications to alleviate symptoms. Many individuals suffering from depression, on the other hand, benefit from visiting a therapist, counselor, or other mental health specialists. Some available antidepressants are selective serotonin reuptake inhibitors (SSRIs), Serotonin-norepinephrine reuptake inhibitors (SNRIs), atypical antidepressants, tricyclic antidepressants, and Monoamine oxidase inhibitors (MAOIs) {5}. Psychotherapy is a common term for consulting with a therapist, psychologist, or other mental health specialist for mental health issues. Psychotherapy teaches patients how to take control of their lives and deal with difficult circumstances using positive coping mechanisms. A mix of many approaches is commonly used to treat depression {6}.

 

Transcranial Magnetic Stimulation (TMS)

TMS (transcranial magnetic stimulation) is a non-invasive therapy for depression that uses magnetic fields to activate nerve cells in the brain. TMS is commonly used when all other depressive therapies have failed. Repetitive TMS, or rTMS, is a therapy for depression that requires the delivery of repetitive magnetic pulses {1}. TMS systems work entirely outside of the body, affecting central nervous system function by delivering strong magnetic fields to various brain regions linked to depression such as the limbic system. TMS does not require anesthesia, and the side effects are usually minuscule compared to antidepressants and electroconvulsive therapy (ECT) {2}.

 

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Figure 1. The basic process of TMS is shown above [10]. 

 

Mechanism

TMS is a non-invasive tool that modulates neuronal processing in the brain by causing a brief discharge of electric current through a stimulated coil. This generates a magnetic field that causes neuron membrane potentials to depolarize in cortical tissue under the coil, affecting the associated nerve loop function. The effects of TMS are linked to context-dependent variables such as total pulses, stimulus frequency and strength, time period between each pulse, and regions on the cortex. Different forms and variations of stimulation, as well as the targeted brain area, can have different biochemical effects. In fact, certain stimulus models may have long-term effects on neuronal function that can continue well after the therapy time has finished {7}. Consequently, during a TMS treatment, an electromagnetic coil is positioned near the forehead. The electromagnet sends a painless magnetic shock to nerve cells in the part of the brain that controls mood and depression. This is intended to stimulate brain areas that are underactive in depression {1}.

 

Treatment Process

In most cases, repetitive TMS is performed in a doctor's office or laboratory and only shows success after a number of therapy sessions. In most cases, meetings are held five days a week for four to six weeks. The doctor determines the best location for the magnets to be placed on the head and the best dosage of magnetic energy for the patient before therapy begins. The duration of the first consultation is usually about 60 minutes. During the first visit, the patient is taken to a recovery area, where they receive treatment. To emit soothing pulses, an electric coil is positioned against the head and turned on and off repeatedly. This produces a tapping or clicking sound that lasts for a few seconds before stopping. A clicking feeling can also develop on the forehead. The term “mapping" refers to this stage of the process. By increasing the magnetic dosage until the patient’s fingertips or hands twitch, the doctor decides the amount of magnetic energy needed. This is referred to as the motor threshold, and it acts as a criterion for deciding the optimal dosage for the patient. Based on the symptoms and side effects, the level of stimulus is increased during therapy {1}.

 

Side Effects

rTMS is well-tolerated and has few adverse effects, with only a limited number of patients opting to avoid therapy due to them. Headaches are the most frequent side effect, reported by around half of patients infected with rTMS. However, this is a minor side effect and usually goes away as the therapy progresses. These headaches can be treated with over-the-counter pain relievers. With rTMS pulses, about a third of patients can experience unpleasant scalp stimuli or facial twitching. This, too, appears to fade with time, though changes in coil orientation and stimulus settings may be made right away to alleviate pain. Since the rTMS system is quite loud, the patients are given earplugs to wear during the procedure. However, some patients may continue to have hearing difficulties after treatment. If earplugs are used during therapy, there is no indication that these symptoms are lasting. Many of the adverse effects of antidepressant drugs, such as gastrointestinal irritation, dry mouth, sexual impairment, weight gain, and sedation, have not been linked to rTMS. Seizures are the most severe side effect of rTMS, although they are highly rare. Even though rTMS is a safe technique, it is worth noting that since it is a modern medication, there could be unforeseeable complications [8].

 

Contraindications

rTMS should not be used on patients who have any form of non-removable metal in their heads (except braces or dental fillings). Failure to adhere to this rule can cause the object to heat up, shift, or malfunction, resulting in serious injury or death. A list of metal implants that can prohibit a patient from having rTMS is as follows: aneurysm clips or coils, stents in the neck or brain, deep brain stimulators, electrodes to monitor brain activity, metallic implants in the ears and eyes, shrapnel or bullet fragments in or near the head, facial tattoos with metallic or magnetic-sensitive ink, and other metal devices or objects implanted in or near the head {8}. 

 

Future Scope

There is currently no definitive data to justify the use of rTMS as a substitute treatment for depression. Although promising outcomes have been documented in both open and randomized controlled trials, the best treatment criteria for individual therapy, such as stimulation location, severity, frequency, and length, are still uncertain [7]. Although these TMS applications are commonly used in clinics around the world, they are still relatively recent and innovative strategies that just scratch the surface of what potential applications may bring. Many future implementations are either in the proof-of-concept stage or are entirely unknown. There have been many studies concerning the protection and effectiveness of noninvasive stimulatory therapies for depression and brain imaging, but other uses have not been examined as extensively. Some of these future implications show that this form of therapy will become even less invasive.  TMS has a wide variety of benefits, including the treatment of psychiatric conditions such as obsessive-compulsive disorder (OCD) and addiction. Applications to help understand the interconnectedness of neuronal processes are another possibility. Most experiments that have been or are currently being conducted to assess the efficacy of TMS for uses other than those listed are still in the proof of concept stage, with limited numbers of participants and no control groups to compare against [9].

 

Conclusion

Depression is one of the most common mental health problems today. Many treatments for depression such as mechanism-based treatments are also a long way off. The non-invasive technique of repetitive transcranial magnetic stimulation (rTMS), which uses a pulsed magnetic field in the brain to stimulate electrical activity, is considered to be an effective treatment for depression. The key findings of clinical and basic research on rTMS for depression, including its antidepressant potency, basic mechanisms, and ability to regulate neuronal functions, neurotransmitters, and brain networks, as well as synaptic and molecular pathways, indicate that it may be a promising choice for treating depression [7].


References


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  4. Daniel K. Hall-Flavin, M. (2017, May 13). Severe, persistent depression. Retrieved March 29, 2021 https://www.mayoclinic.org/diseases-conditions/depression/expert-answers/clinical-depression/faq-20057770. Retrieved: 29/03/2021.

  5. Depression (major depressive disorder). (2018, February 03). https://www.mayoclinic.org/diseases-conditions/depression/diagnosis-treatment/drc-20356013. Retrieved: 29/03/2021.

  6. Psychotherapy. (2016, March 17). https://www.mayoclinic.org/tests-procedures/psychotherapy/about/pac-20384616#:~:text=Psychotherapy%20is%20a%20general%20term,%2C%20feelings%2C%20thoughts%20and%20behaviors. Retrieved: 05/04/2021.

  7. Peng, Z., Zhou, C., Xue, S., Bai, J., Yu, S., Li, X., . . . Tan, Q. (2018, April 25). Mechanism of repetitive transcranial magnetic stimulation for depression. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5936045/#:~:text=Transcranial%20magnetic%20stimulation%20(TMS)%20is,cell%20membrane%20potentials%20depolarizing%20in. Retrieved: 29/03/2021.

  8. Psychiatry & behavioral sciences: Johns Hopkins Medicine, based in Baltimore, Maryland. (2021, March 22). https://www.hopkinsmedicine.org/psychiatry/  Retrieved: 17/04/2021.

  9. Matthew Carpenter. (2018).  Transcranial Magnetic Stimulation: In-Depth Review of Methods, Efficacy and Future Applications. https://openprairie.sdstate.edu/cgi/viewcontent.cgi?article=1005&context=biomicro_plan-b. Retrieved: 30/03/2021.

  10. sapien labs.org. (n.d.). https://sapienlabs.org/the-basics-of-transcranial-magnetic-stimulation/.  Retrieved: 05/05/2021.

Arya Reddy

Arya Reddy


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