Deep TMS (dTMS)

In the last half century, treatment options in the field of psychiatry have increased exponentially with new developments and technologies. A new class of pharmacological drugs was developed, electroconvulsive therapy (ECT) protocols were optimized, and brain stimulation techniques were invented. Most importantly, many Psychiatric symptoms now have identifiable functional changes in specific regions and circuits in the brain. Methods such as MRI, fMRI, positron emission tomography (PET) have linked certain disorders and symptoms with certain diseases and loss of function in brain regions.

This allowed techniques such as deep brain stimulation (DBS) or transcranial magnetic stimulation (TMS-TMU) to target specific networks.

Targeting brain regions affected in a particular mental disorder has become easy. One condition for which significant progress has been made is major depressive disorder (MDD). MDD is a common disease and its lifetime prevalence is 17%.

It is the second leading cause of disability according to World Health. Patients diagnosed with MDD have irregularities in various brain regions, including hypometabolism in regions such as the dorsolateral prefrontal cortex (DLPFC), and abnormal overactivity in the cingulate cortex (ACC) and amygdala, basal ganglia, and thalamus activity. Despite the availability of psychotherapy and more than four classes and 30 different pharmacological agents, the majority (32-52%) of MDD is still considered resistant to treatment. These results necessitate new strategies for the treatment of this disorder. Among the available treatments, stimulation technologies, ECT, are still the most widely accepted. ECT (Electro Convulsive Therapy) is an effective method with a remission rate of over 70%. However, inpatient treatment, which is associated with procedures and side effects, is applied as a last option because it requires anesthesia.

It is the most stigmatized treatment available in psychiatry and a true 'last resort' and is only used for those who are severely resistant to drugs or TMS. (Deep Brain Stimulation) has also been shown to alleviate the depressive state. Conventional TMS, which is a noninvasive technique in drug-resistant MDD patients, does not have the above disadvantages. and moderate MDD. To address these limitations, deep TMS (dTMS) was introduced. dTMS includes all the benefits of TMS. There is no need for hospitalization or anesthesia and negligible side effects. There is less focal distribution of the electric field with the advantage of stimulating deeper brain targets. Similar to the traditional TMS technique, dTMS uses short magnetic pulses.

Generally, trains provide a facilitating effect, inducing increased neuronal excitability of transmitted pulses in high-frequency stimulation (>5 Hz). Thus, certain brain regions of hypo- or hyper-activity can be modulated. Conversely, however, conventional TMS coils (eg 8 or round) stimulate targets directly up to ~1 cm below the surface of the Skull, dTMS can simulate up to ~4 cm below the skull surface. This increased stimulation depth is achieved due to multiple coils. These coils in the H-coil are bundled together and improve the depth penetration of the electromagnetic field without the need to increase it. Although deep stimulation can also be performed with a large circular coil or a dual cone coil, their electromagnetic field decays faster and much higher intensities must be used to achieve significantly deep targets.

dTMS in the Clinic

In the United States, dTMS uses the H1-coil, and different types of dTMS are used. In Europe, dTMS using the H1-coil has started to be used for unipolar depression, bipolar depression, negative symptoms and post-traumatic treatment of schizophrenia, and OCD (Obsessive Compulsive Disorder) and post-traumatic stress disorder (PTSD). Several versions of H-coils are designed to target other brain networks.

It has started to be used in the treatment of Alzheimer's disease, chronic pain, smoking cessation, obsessive compulsive disorder (OCD), autism, Parkinson's disease, stroke rehabilitation and multiple sclerosis (MS).

Clinical Considerations

In the United States, the dTMS device is only available with a prescription from a doctor (usually a psychiatrist or a neurologist). Currently, approximately 90% of all TMS treatments are administered in the treatment form of dTMS.

Before administering dTMS to a patient, informed consent must be obtained from the patient or legal guardian. In addition to explaining the procedure in the process, there should be a description of the risks, benefits and alternatives. Among the risks and potential side effects of dTMS, headaches, facial pain, toothache, or neck pain can often occur during the procedure but can also occur between procedures. Patients with pre-existing epilepsy may be at risk of developing seizures. Despite these potential risks, it is among the safest treatment methods. The advantage of this method, which does not require outpatient anesthesia or hospitalization, over classical TMS is its capacity to regulate deteriorated structures in deep brain structures associated with diseases.