(p. 609) Therapeutic Applications of Tms
Focal noninvasive brain stimulation represents a previously unprecedented means of bridging the gap between the neuroscience of clinical disorders and the clinical science of their treatment. The ability to stimulate the brain noninvasively sparked early and sustained interest among clinical researchers regarding its therapeutic potential in psychiatry and neurology. Systemically administered pharmacological agents may be ineffective or cause treatment-interfering side-effects. TMS, on the other hand, avoids systemic side-effects, and stimulates the brain with a spatial and temporal specificity that cannot currently be achieved pharmacologically or via electroconvulsive therapy.
TMS has already attained regulatory approval in some countries for the treatment of depression, and a growing list of other disorders are under active study. Clearly the therapeutic potential of tools like TMS to expand treatment options for medication-resistant disorders merits close scrutiny; however, it is equally essential that enthusiasm not outpace evidence when judging the value of a novel therapeutic intervention. The literature on the clinical potential of TMS has matured to the stage where it is now possible to compile a comprehensive review of the potential applications of TMS in a range of psychiatric and neurological disorders. This section on therapeutic applications of TMS provides a critical review of the state of the evidence for and against the therapeutic value of TMS.
While tools like TMS present great therapeutic promise, the realization of that promise demands an in-depth knowledge of pathophysiology of the illness in question, and of the mechanisms by which repeated activation of circuits can induce plastic changes in the functioning of those circuits. Since TMS is a focal intervention, its clinical utility will ultimately depend upon our knowledge of the circuitry of the underlying disorder that will guide the selection of the target cortical site for stimulation. Likewise, since TMS is administered in a phasic rather than tonic fashion, its appropriate use will hinge on knowledge of the dynamics by which repeated brain stimulation interacts with ongoing endogenous processes to induce lasting changes in behavior.
The ultimate therapeutic value of focal noninvasive brain stimulation may hinge not so much on the tool itself, but on how wisely we use it. (p. 610)