The Antidepressant Effect of Right Prefrontal Low Frequency rTMS in an Accelerated Treatment Model ( rTMS). An Open Controlled, Randomized Study

rTMS has appeared a potential new non-invasive antidepressant method, which implies nonconvulsive focal stimulation of the brain through a time varying magnetic field. RTMS is based on the principle of electromagnetism. An electromagnetic coil placed on the scalp produces a time-varying magnetic field that penetrates the scalp and skull unattenuated and gives rise to a current in the proximity of the cerebral cortex as well as functionally connected parts of the brain. Research on rTMS reports of minimal side effects of the method.

Previous research indicates that the antidepressant effect of rTMS is associated with specific stimulation of the dorsolateral prefrontal cortex. The stimulus frequency has shown to play a key role in the mechanisms of action of rTMS. Previous animal studies have shown that low frequency rTMS is associated with long term inhibition of neuronal activity (long term depression), while high frequency stimulation is followed by prolonged activation (long term potentiation). The majority of clinically controlled studies have used high frequency stimulation of the left frontal cortex, which has been approved by the USA and later in the European Union for the treatment of depression. Fewer studies 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. Randomized controlled trials and meta-analysis have shown that both stimulus models have a clinically, significant antidepressant effect at the same level as antidepressant drugs, and recent research clearly indicates that low frequency rTMS of the right prefrontal cortex is associated with an antidepressant effect at the same level as the high frequency model. The issue indicates that low frequency due to the more advantageous side effect profile should be the stimulus model of choice in a clinical setting.

The Department for Affective Disorders, Aarhus University Hospital has taken part in rTMS research since 1999, and the outpatient clinic has used low frequency rTMS as add-on to conventional antidepressant treatment since 2015. A single treatment course covers 20 treatment sessions given on 20 consecutive days. The demand for daily treatment and attendance in the outpatient clinic for 20 days is resource demanding both for the patient and the clinic. In consequence the investigators want to examine the antidepressant effect of an accelerated stimulus model comparing the antidepressant efficacy of conventional treatment (20 days) with a treatment model covering the same number of stimuli given within one week.The study is lightening the significance of the association between the number of stimulus pulses, the length of the total treatment period and the antidepressant effect. Patients suffering for depression may benefit from the outcome of the study by obtaining an accelerated antidepressant effect from a less time consuming stimulus model. The outcome of the study may be implemented in clinical practice from day one.