The Antidepressant Efficacy of Repetitive Transcranial Magnetic Stimulation ( rTMS) as add-on to Electroconvulsive Therapy (ECT). A Double Blind Randomized Controlled Trial.

ECT is a well-established and effective method for the treatment of severe depression. During the last decades, rTMS has appeared as a potential new non-invasive antidepressant method, which may be a potential alternative to ECT due to fewer side effects.

Both methods expose the brain to an electric current. But while ECT is associated with global cerebral stimulation elicited by an epileptic seizure, rTMS implies non-convulsive focal stimulation through a time varying magnetic field. Thus, the antidepressant effect of rTMS does not depend on seizure activity and consequently requires no anesthesia. In addition, rTMS seems not to be associated with cognitive disturbances.

Previous research indicates that the antidepressant effect of rTMS is associated with specific stimulation of the dorsolateral prefrontal cortex. The majority of clinically controlled studies have used high frequency stimulation of the left frontal cortex (1-4). Few have used right prefrontal low frequency rTMS, which has less side effects, such as local discomfort and a lower risk of releasing epileptic seizures, than high frequency stimulation (5-10). Both models have been used with varying results. Meta-analysis of the antidepressant effect of rTMS (11,x) have found a modest, statistically significant antidepressant effect but generally definite conclusions on the antidepressant effect of rTMS has been difficult to draw, probably because of small and selected study populations, varying ways of stimulation and other confounding factors in the clinical setting.

The important clinical question of whether rTMS may substitute ECT in the treatment of depression has almost exclusively been elucidated in studies using high frequency stimulation of the left frontal cortex. Some of these suggest that the effectiveness of rTMS is equal to that of ECT in non-delusional patients (12-19). However, a recent investigation has compared the antidepressant efficacy and side effects of right prefrontal low frequency rTMS with ECT. In this study the mean Hamilton total 17-item (HAM-D score) scores were reduced significantly over time in both groups (ECT: p<0.001, rTMS: p<0.001); but ECT was more effective than rTMS on a short term after 3 weeks of treatment. The outcome did not point to right frontal low frequency rTMS as a first line substitute for ECT, but it might have place in the treatment of depression as add on to other types of treatment.

ECT is normally administered 3 times a week for 3-4 weeks. Daily treatment sessions might accelerate remission, but is impossible because of cognitive side effects. However, rTMS seems not to be associated with reduction in cognitive performance and might potentiate the antidepressant efficacy of ECT. Therefore the investigators have found it clinical interesting to investigate in which degree low frequency right prefrontal rTMS used ad add-on may potentiate the antidepressant effect of unilateral ECT and accelerate remission .