Transcranial magnetic stimulation

Transcranial magnetic stimulation (TMS), also known as repetitive transcranial magnetic stimulation (rTMS), is a noninvasive form of brain stimulation in which a changing magnetic field is used to cause electric current at a specific area of the brain through electromagnetic induction. An electric pulse generator, or stimulator, is connected to a magnetic coil, which in turn is connected to the scalp. The stimulator generates a changing electric current within the coil which induces a magnetic field; this field then causes a second inductance of inverted electric charge within the brain itself.:3 Transcranial magnetic stimulation (TMS), also known as repetitive transcranial magnetic stimulation (rTMS), is a noninvasive form of brain stimulation in which a changing magnetic field is used to cause electric current at a specific area of the brain through electromagnetic induction. An electric pulse generator, or stimulator, is connected to a magnetic coil, which in turn is connected to the scalp. The stimulator generates a changing electric current within the coil which induces a magnetic field; this field then causes a second inductance of inverted electric charge within the brain itself.:3 TMS has shown diagnostic and therapeutic potential in the central nervous system with a wide variety of disease states in neurology and mental health, with research still evolving. Adverse effects of TMS are rare, and include fainting and seizure. Other potential issues include discomfort, pain, hypomania, cognitive change, hearing loss, and inadvertent current induction in implanted devices such as pacemakers or defibrillators. TMS is non-invasive, and does not require surgery or electrode implantation. Its use can be divided into diagnostic and therapeutic applications. Effects vary based on frequency and intensity of the magnetic pulse as well as the length of the train, which affects the total number of pulses given. TMS can be used clinically to measure activity and function of specific brain circuits in humans, most commonly with single or paired magnetic pulses. The most widely accepted use is in measuring the connection between the primary motor cortex of the central nervous system and the peripheral nervous system to evaluate damage related to past or progressive neurologic insult. Repetitive high frequency TMS (rTMS) has shown diagnostic and therapeutic potential with the central nervous system in a variety of disease states, particularly in the fields of neurology and mental health. Although TMS is generally regarded as safe, risks are increased for therapeutic rTMS compared to single or paired diagnostic TMS. Adverse effects generally increase with higher frequency stimulation. The greatest immediate risk is fainting, though this is uncommon. Seizures have been reported, but are extremely rare. Other adverse effects include short term discomfort, pain, brief episodes of hypomania, cognitive change, hearing loss, impaired working memory, and the induction of electrical currents in implanted devices such as cardiac pacemakers. During the procedure, a magnetic coil is positioned at the head of the person receiving the treatment using anatomical landmarks on the skull, in particular the inion and nasion. The coil is then connected to a pulse generator, or stimulator, that delivers electric current to the coil.