Transcranial Magnetic Stimulation in the Treatment of Depression

Abstract

Objective: Transcranial magnetic stimulation (TMS) is a noninvasive and easily tolerated method of altering cortical physiology. The authors evaluate evidence from the last decade supporting a possible role for TMS in the treatment of depression and explore clinical and technical considerations that might bear on treatment success. Method:The authors review English-language controlled studies of nonconvulsive TMS therapy for depression that appeared in the MEDLINE database through early 2002, as well as one study that was in press in 2002 and was published in 2003. In addition, the authors discuss studies that have examined technical, methodological, and clinical treatment parameters of TMS. Results:Most data support an antidepressant effect of high-frequency repetitive TMS administered to the left prefrontal cortex. The absence of psychosis, younger age, and certain brain physiologic markers might predict treatment success. Technical parameters possibly affecting treatment success include intensity and duration of treatment, but these suggestions require systematic testing.Conclusions: TMS shows promise as a novel antidepressant treatment. Systematic and large-scale studies are needed to identify patient populations most likely to benefit and treatment parameters most likely to produce success. In addition to its potential clinical role, TMS promises to provide insights into the pathophysiology of depression through research designs in which the ability of TMS to alter brain activity is coupled with functional neuroimaging. (Am J Psychiatry 2003; 160:835-845)In 1831, Michael Faraday discovered that electrical currents can be converted into magnetic fields and vice versa. His principle of mutual induction is the basis of transcranial magnetic stimulation (TMS). In TMS, a bank of capacitors is rapidly discharged into an electric coil to produce a magnetic field pulse (Figure 1). When the coil is placed near the head of a human or animal, the magnetic field penetrates the brain and induces an electric field in the underlying region of the cerebral cortex (4) (Figure 2). An electrical field of sufficient intensity will depolarize cortical neurons, generating action potentials. These then propagate to exert their biological effects. For example, TMS over the left motor cortex causes action potentials that propagate through the corticospinal tract, causing twitches in contralateral skeletal muscles.This new technology has been used to affect underlying brain tissue at several levels. First, TMS can alter regional activity within the cortex. Positron emission tomography (PET) has revealed changes in cortical metabolism and dose-dependent changes in regional cortical blood flow in response to TMS (5-7). Such changes are also observed at sites distant from the magnetic stimulus, showing that the effects of TMS propagate to other parts of the brain (6, 7). The connections demonstrated in this manner correspond to known neural pathways in nonhuman primates, suggesting that the propagation of TMS effects occurs by means of...

Mechanisms of Action Underlying the Effect of Repetitive Transcranial Magnetic Stimulation on Mood: Behavioral and Brain Imaging Studies

“…In depressed patients, a recent meta-analysis (Gershon et al, 2003) revealed that the most efficacious rTMS treatment protocols applied highfrequency (ie 5-20 Hz) rTMS over the left MDLFC for 5-20 days, resulting in improvement in depression ratings in 41% of the patients studied (n ¼ 139). In healthy subjects, however, the short-term changes in affect observed following a single rTMS session are often opposite to the changes in mood observed in depressed patients, namely more negative affect following 10-Hz rTMS applied over the left MDLFC (eg George et al, 1996;Pascual-Leone et al, 1996;Martin et al, 1997; but for negative findings, see Mosimann et al, 2000;Padberg et al, 2001).…”

Estimulação magnética transcraniana: um estudo controlado do padrão da ativação cerebral na depressão maior utilizando a tomografia por emissão de pósitrons

“…Quando este dispositivo é posicionado próximo à cabeça de um ser humano, o campo magnético penetra o cérebro e induz um campo elétrico na região adjacente do córtex cerebral. Um campo elétrico de intensidade suficiente despolariza os neurônios corticais, gerando um potencial de ação (Gershon et al, 2003).…”

“…Os parâmetros técnicos para a aplicação da EMT no TDM ainda não estão definidos. Não se sabe ainda qual o local exato, número de dias, frequência e intensidade da estimulação (Gershon et al, 2003). Da mesma forma, ainda não se sabe qual população clínica melhor se beneficiaria desta abordagem, não sabendose ainda se seria melhor aplicável à depressão unipolar, bipolar ou psicótica (Gershon et al, 2003).…”

“…Estudos sobre a fisiopatologia do TDM foram habitualmente realizados em um único dia Paus et al, 1997). Estudos abordando a EMT como tratamento utilizaram a EMT em diferentes dias, o que provavelmente aumenta o efeito da estimulação (Gershon et al, 2003). Estudos abordando tratamento da Depressão e outras patologias utilizaram um numero maior de dias e sessões de aplicação da TMS (Paus et al, 1999).…”

“…A maior parte dos estudos foi realizada com o aparelho sendo posicionado no local de forma manual, ou sem o uso de um robô Paul et al, 1997, Gershon et al, 2003, o que prejudica o direcionamento da estimulação. Ao realizarmos previamente a RMI, definindo o local preciso do CPFDL em cada paciente, e ajustando o robô para estimular aquela área precisa, nos asseguramos da estimulação do local preciso (Figura 9).…”