Transcranial Magnetic Stimulation (TMS) is a novel procedure that is used to treat neurological and psychiatric pathologies. The Dra. Lluch, a specialist in Clinical Neurophysiology, explains the benefits of this procedure.
Functioning of the Transcranial Magnetic Stimulation (EMT)
Transcranial Magnetic Stimulation is a neurostimulation and neuromodulation technique based on the principle of electromagnetic induction of an electric field in the brain. This field must be of sufficient magnitude and density to depolarize neurons. When the pulses are applied repetitively they can modulate the excitability, increasing or decreasing it depending on the stimulation parameters (frequency and intensity), as well as the duration of the trains and the pause between them.
This has potential consequences at the behavioral and therapeutic level. Repetitive Transcranial Magnetic Stimulation (TMS) can become a very promising noninvasive treatment in a wide variety of neuropsychiatric disorders.
Use of Transcranial Magnetic Stimulation (EMT)
Within the psychiatric disorders of therapeutic application are depression, acute mania, bipolar or panic disorder, OCD, schizophrenia, catatonia and post-traumatic stress syndrome. Also neurological disorders such as Parkinson's syndrome, dystonia, tics, tinnitus, spasticity, post-stroke rehabilitation and pain, whether neuropathic or migraine.
Numerous specialists in Clinical Neurophysiology offer this therapeutic alternative in several disorders and has already been approved in some countries in the treatment of depression refractory to medication. It is reasonable to expect an increasing introduction of this technique in the coming years.
Side effects of Transcranial Magnetic Stimulation (TMS)
The safety of the technique is supported by numerous experts, who state that patients with a history of epileptic seizures or neurosurgical interventions should not undergo EMT.. In addition to those who have implanted aneurysm clips or other metallic devices, a pacemaker or hearing aid. Or if you are at risk of being pregnant or being able to stay during sessions, in addition to suffering from serious cardiac or circulatory diseases.
However, the risk of epileptic seizures in healthy subjects is very low. Transient hearing problems are easily solved by placing earplugs during the technique.
The most common side effects are vasovagal syncope due to the tension associated with the procedure. Some discomfort in the form of a headache after the intervention could also occur in an isolated patient without consequences.. Discomfort is described during the test if contractions of the facial muscles or neck pain occur due to the position maintained during the test if the duration is prolonged. Isolated cases of mania, psychotic outbreaks, anxiety, agitation, suicidal ideation and insomnia have been reported.
How Transcranial Magnetic Stimulation (EMT) works
The EMT consists in the production of a very short electric current. Passing a small coil of copper wire placed on the scalp generates a magnetic field of sufficient intensity to pierce the skull and depolarize the neurons of the cortex that are about two centimeters below. Unlike EET (Transcranial Electrical Stimulation), it is a painless technique.
The EMT can be applied by means of an isolated stimulus, by means of stimulus pairs separated by a variable interval or in trains, in a repetitive way. In the latter case, it can be done by isolated pulses at fast frequencies (when the stimulus frequency is more than 1 Hz) and at slow frequencies (when the frequency is 1 Hz or less). Such classification is based on the different physiological effects and degree of risk associated with the different stimulations. In turn, the application can be carried out regularly or in patterns, which refers to the application of short periods of high frequency EMT separated by intervals of absence of stimulation.
There is an infinite variety of combinations of such protocols and it is important to point out that the effects and safety of them can differ and small changes can have a profound impact.
Transcranial Magnetic Stimulation (EMT) step by step
The patient sits in a reclining chair. Previously he will have read a questionnaire and signed a consent where the possible side effects of the technique are indicated and accepted and it is established that there is no contraindication. However, any metal objects should be removed in the vicinity of the coil application and earplugs should be provided.
In the first session the motor threshold should be evaluated, which will consist in the application of the coil to intensities initially subthreshold and will be increased until detecting the motor contraction of the thenar eminence (thumb) right.
Depending on the therapy to be performed, the stimulation point can be this same motor point or, in the case of depressions, it will move to locate the dorsolateral prefrontal cortex. Once at the site, the coil arm is fixed and therapy begins.
During the treatment a series of taps are perceived that will temporarily stop feeling. In subsequent sessions it will not be necessary to recalculate the threshold.
The duration of the procedure will be variable and will depend on the pathology of the patient to be treated and the protocol used. A typical protocol for depression usually includes between 10 and 20 consecutive sessions lasting between 30 and 45 minutes. In the case of migraines, the protocol establishes 3 sessions on alternate days of about 7 minutes. For all these reasons, the treatment must be individualized.
Results Transcranial Magnetic Stimulation (TMS)
In general terms, it can be said that EMT produces a selective stimulation of certain areas of the brain that, depending on the applied protocol, will produce an increase or decrease in neuronal excitability.
Often there is no noticeable change in mood or other psychiatric symptoms during the first sessions. In TMS for therapeutic purposes, long-term cognitive changes are related to the cumulative effects of repeated sessions in their application to psychiatric and neurological disorders.
EMT can produce several types of biological effects in addition to purely neurocognitive effects such as:
- Endocrine effects: We have seen a response of hormones of the pituitary-hypothalamus axis (prolactin, TSH, FSH and cortisol) and the increase in plasma of beta-endorphins in the treatment of migraine.
- Effects on neurotransmitters, such as dopamine, which could induce beneficial effects in the parkinsonian.
- Effects on the immune system by decreasing the number of lymphocytes.
- Autonomic function, since many brain regions are involved in the control of blood pressure, respiration and heart rate.
We must take into account some factors that may also influence the results obtained:
- The effects can be variable if they are applied in the acute phase of the disease or by prevention.
- Many variables can theoretically contribute alone or in combination to modify the previous stage of neuronal activity and can affect the effects or risk: menstrual cycle, age, level of anxiety, sleep deprivation, hidden substance abuse, thinness of the layers of the skull or brain atrophy.
- Interaction with other forms of therapy such as psychotherapy, neurorehabilitation or drugs, mainly by exerting synergistic or opposite effects.