Transcranial Magnetic Stimulation

Transcranial magnetic stimulation is a diagnostic tool that stimulates neurons in the motor cortex and induced muscle tissue. More sustained magnetic fields are used to locate areas pertained to vision, memory, and muscle function. A non-invasive method has evolved wherein inductive electric charge is applied to cerebral cortex to study its effects on the cortex. This method is termed as transcranial magnetic stimulation (TMS).

Despite its deficiencies, TMS affords an opportunity of understanding the brain function and its effect on behavior. TMS is used for nerve transmission, as transcranial magnetic stimulation on the motor cortex area will generate muscular induced response on the other side. With the evolvement of a system that delivers quick and recurring stimulation, transcranial magnetic stimulation method has also attracted the attention of the people who are interested in applying the procedure for the treatment of depression. This recurring stimulation method is called repetitive or rapid-rate transcranial magnetic stimulation (rTMS).

Rapid-Rate (Repetitive) Transcranial Magnetic Stimulation

Studies indicate that activation of left prefrontal cortex exhibit antidepressant characteristics. Repetitive or rapid-rate TMS is used to stimulate that cortex to get benefit for depression. Also, it does not need anesthesia, unlike electroconvulsive therapy and it does not induce seizures either. rTMS is also being tried as treatment option in cases of schizophrenia, migraine, spinal cord damage, and fibromyalgia.

TMS is used to find the linkages between brain activity and work performance. It helps in understanding the connectivity aspects of brain functioning. The TMS method involves placing a tiny coil over the scalp area of a person, and swiftly alternating electric charge is applied to the coil, thereby creating a magnetic field. This magnetic field goes unhindered through the brain. After stimulation, a magnetic coil, shaped as two conjoined loops, is placed at a few inches from the scalp on the left side of the head.

When electricity is passed through the coils, magnetic field is created in the loops. This magnetic field, in turn, will induce small electric charges which will excite nerve cells in the brain. The magnetic field also causes excitation in the muscles and skin of the scalp under the coil. Thus, this repetitive transcranial magnetic stimulation does not pass electric charge directly to the scalp, instead it creates magnetic field that will excite nerve cells in the brain, thereby avoiding the possibility of causing seizures. This procedure does not require anesthesia, unlike electroconvulsive therapy. Low frequency mode of rTMS has been reported to cause continued decline in the activity of the cortex.

Efficacy of rTMS

In recent studies, application of rTMS at various scalp positions did not produce any significant alterations in neurology, cognitive behavior, EEG, EKG and in various hormone levels, i.e., the hormone of prolactin, thyroid stimulating hormone, adrenal cortex stimulating hormone, etc.

The supposition that a focality-centered treatment like rTMS will alleviate depression, which has neurological and physiological implications in many areas of the brain, is not fully established. In some cases, high frequency repetitive TMS applied to the left prefrontal cortex has displayed antidepressant effects in experiments with people. But more research is needed for establishing the efficacy of this treatment.

Possible Side Effects of rTMS

The side effects, if any, are minimal. The most reported side effect of rTMS is headache, may be a tension induced headache, due to excitation of the muscles in the proximity. Others felt uneasiness from the heat generated by the coil. No seizures are reported. People with past history of seizures may experience mild seizures.

Normally rTMS treatment does not result in any pain to the patient. The magnetic field activity may cause some uncomfortable effects such as stinging or tapping sensation on the scalp area. Sometimes, muscle tightening may occur on the scalp near the position of the coil.

Memory loss is not reported with rTMS, but some studies indicated memory problems and some loss of concentration in persons.

The strident snapping noise of the coil during stimulation may cross frequency ranges of tolerance in people. This may result in temporary hearing loss.

rTMS and ECT

When compared to electroconvulsive therapy (ECT), rTMS does not produce any post-treatment memory impairment. rTMS has fewer adverse effects than ECT. Because of that, rTMS may, one day, become the favored treatment option for depression. Or it may be used alongside antidepressant medications concurrently to hasten up relief from the depression symptoms. Moreover, there is this cost factor. The cost of ECT is estimated to be six times more than the rTMS treatment.