A substantial proportion of patients fail to respond to standard treatments for depression. Several new methods of stimulating the brain are being developed as alternative interventions for these and other patient groups.
Repetitive transcranial magnetic stimulation is a method of brain stimulation that involves the application of repeated magnetic pulses to directly activate cortical neurones. Several studies show it has antidepressant efficacy.
There are few adverse effects of repetitive transcranial magnetic stimulation. However, the optimal stimulation parameters are not yet fully established.
Major depressive disorder is common and disabling with a lifetime prevalence of around 15%.1 There are a range of psychosocial treatments and drugs for depression. Despite these options, approximately 30% of patients remain unwell with ‘treatment-resistant depression’ resulting in substantial suffering as well as high treatment costs.2 The main established treatment option for patients with treatment-resistant depression is electroconvulsive therapy (ECT) but this has cognitive adverse effects, requires general anaesthesia and has a stigma associated with it.3 This has prompted research into new methods of brain stimulation.
Repetitive transcranial magnetic stimulation
Repetitive transcranial magnetic stimulation (rTMS) has recently been developed as an additional option for treatment-resistant depression. It may also have a role for patients who cannot tolerate other treatments.
rTMS involves the application of a rapidly time variable magnetic field, administered via a coil placed over the scalp, to stimulate brain activity4 (see Fig. 1). A high voltage current in the coil generates a focused magnetic field which passes into the brain and induces an electrical field. This induces depolarisation of superficial cortical neurones.4 Repeated high frequency stimulation increases brain activity, and low frequency stimulation decreases it.5 rTMS can be applied either directly to nonconvulsively modulate brain activity or to induce a focused seizure (magnetic seizure therapy).
Fig. 1 Repetitive transcranial magnetic stimulation procedure
|REPETITIVE TRANSCRANIAL MAGNETIC STIMULATION||ELECTROCONVULSIVE THERAPY|
Failure to tolerate other treatments for depression
Possible first-line treatment based on patient choice
Emergency treatment of depression requiring urgent clinical response
|Efficacy||Moderately well established
Response rates <50%
Response rates >50%
|Safety||Low risk of seizure induction
No cognitive adverse effects
No general anaesthetic
|Risks associated with general anaesthesia
Memory impairment, possible other cognitive adverse effects
One of the major benefits of rTMS is its benign adverse effect profile.18 Some patients find the treatment uncomfortable or experience a transient headache afterwards, but there are no other major reported adverse effects. rTMS can induce seizures but the risk is extremely low when treatment is applied following standard safety guidelines.19 The induction of mania is possible in patients with bipolar disorder, but has not been reported in unipolar depression.20
Standard left-sided rTMS clearly has antidepressant properties but there are a range of issues that remain unresolved. These include the optimal method of administration. Other forms of rTMS such as low frequency stimulation applied to the right dorsolateral prefrontal cortex and bilateral rTMS also have efficacy.21 Other uncertainties include the individualisation of treatment parameters and the evaluation of maintenance protocols to limit the problematic issue of depressive relapse. rTMS also appears a useful treatment for patients with relative contraindications to drugs and ECT or when there is a wish to avoid these treatments, such as during pregnancy, but only limited data on such uses are currently available.22
Magnetic seizure therapy
The therapeutic benefits of ECT may be related to the seizure, rather than the direct electrical current. Researchers are investigating the effects of using rTMS to provoke a seizure. This requires rTMS to be applied at a frequency and intensity beyond that used in standard therapy. As with ECT, a general anaesthetic is required.
Several human trials of magnetic seizure therapy have begun but currently insufficient data are available to confirm its place in treatment. Open-label data and a small comparative trial23 have suggested that it might have similar efficacy to ECT with fewer cognitive adverse effects, although this conclusion is still very preliminary.
A range of novel brain stimulation technologies are currently under active investigation for the treatment of depression. rTMS has progressed down this developmental path to a point where it is currently entering into clinical practice. However, further research is still required to optimise its application. Its availability in Australia is currently limited by the lack of a Medicare rebate for treatment. Only limited treatment programs subsidised by hospital services and without direct patient charge are currently accessible in some private and public hospitals. Magnetic seizure therapy is at an earlier stage of development but there are some promising preliminary results.
Professor Fitzgerald is supported by a National Health and Medical Research Council (NHMRC) Fellowship. In the last two years he has received equipment for research from Brainsway Ltd and MagVenture A/S, manufacturers of TMS and related equipment, and Medtronic Ltd. He is also the Chief Investigator on an ongoing NHMRC sponsored clinical trial of magnetic seizure therapy versus ECT, and other rTMS related research studies.
The following statements are either true or false.
1. Unlike electroconvulsive therapy, repetitive transcranial magnetic stimulation therapy does not require a general anaesthetic.
2. Repetitive transcranial magnetic stimulation therapy induces remission in more than 50% of patients with treatment-resistant depression.
Answers to self-test questions
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- Greenberg PE, Kessler RC, Birnbaum HG, Leong SA, Lowe SW, Berglund PA, et al. The economic burden of depression in the United States: how did it change between 1990 and 2000? J Clin Psychiatry 2003;64:1465-75.
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- Barker AT, Jalinous R, Freeston IL. Non-invasive magnetic stimulation of human motor cortex. Lancet 1985;1:1106-7 .
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- Schlaepfer TE, George MS, Mayberg H; WFSBP Task Force on Brain Stimulation. WFSBP Guidelines on Brain Stimulation Treatments in Psychiatry. World J Biol Psychiatry 2010;11:2-18.
- Fitzgerald PB, Laird AR, Maller J, Daskalakis ZJ. A meta-analytic study of changes in brain activation in depression. Hum Brain Mapp 2008;29:683-95.
- George MS, Ketter TA, Post RM. Prefrontal cortex dysfunction in clinical depression. Depression 1994;2:59-72.
- Schutter DJ. Antidepressant efficacy of high-frequency transcranial magnetic stimulation over the left dorsolateral prefrontal cortex in double-blind sham-controlled designs: a meta-analysis. Psychol Med 2009;39:65-75.
- O’Reardon JP, Solvason HB, Janicak PG, Sampson S, Isenberg KE, Nahas Z, et al. Efficacy and safety of transcranial magnetic stimulation in the acute treatment of major depression: a multisite randomized controlled trial. Biol Psychiatry 2007;62:1208-16.
- George MS, Lisanby SH, Avery D, McDonald WM, Durkalski V, Pavlicova M, et al. Daily left prefrontal transcranial magnetic stimulation therapy for major depressive disorder: a sham-controlled randomized trial. Arch Gen Psychiatry 2010;67:507-16.
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- Rosa MA, Gattaz WF, Pascual-Leone A, Fregni F, Rosa MO, Rumi DO, et al. Comparison of repetitive transcranial magnetic stimulation and electroconvulsive therapy in unipolar non-psychotic refractory depression: a randomized, single-blind study. Int J Neuropsychopharmacol 2006;9:667-76.
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- Holtzheimer PE 3rd, McDonald WM, Mufti M, Kelley ME, Quinn S, Corso G, et al. Accelerated repetitive transcranial magnetic stimulation for treatment-resistant depression. Depress Anxiety 2010;27:960-3.
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- Wassermann EM. Risk and safety of repetitive transcranial magnetic stimulation: report and suggested guidelines from the International Workshop on the Safety of Repetitive Transcranial Magnetic Stimulation, June 5-7, 1996. Electroencephalogr Clin Neurophysiol 1998;108:1-16.
- Xia G, Gajwani P, Muzina DJ, Kemp DE, Gao K, Ganocy SJ, et al. Treatment-emergent mania in unipolar and bipolar depression: focus on repetitive transcranial magnetic stimulation. Int J Neuropsychopharmacol 2008;11:119-30.
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- Zhang X, Liu K, Sun J, Zheng Z. Safety and feasibility of repetitive transcranial magnetic stimulation (rTMS) as a treatment for major depression during pregnancy. Arch Womens Ment Health 2010;13:369-70.
- Kayser S, Bewernick BH, Grubert C, Hadrysiewicz BL, Axmacher N, Schlaepfer TE. Antidepressant effects, of magnetic seizure therapy and electroconvulsive therapy, in treatment-resistant depression. J Psychiatr Res 2011;45:569-76.