Accelerated Transcranial Magnetic Stimulation (aTBS) to Treat Depression

Repetitive transcranial magnetic stimulation (TMS) is a technique for stimulating brain activity using transient magnetic field to induce an electrical current in the brain producing firing of focal groups of brain cells. TMS is beginning to emerge in routine clinical practice as a treatment for depression. The predominant hypothesis is that depressed patients benefit from left sided high-frequency TMS (LHF-TMS) over the left dorsolateral prefrontal cortex (DLPFC)(1). A major limitation of rTMS is the large amount of time taken for a standard protocol (38 minutes a day for 20-30 working days). The optimal type and duration of TMS is still uncertain , as is the optimal strategy for continuing or changing type of rTMS if there is poor initial response.(1) One potential strategy to improve the acceptability of rTMS is to compress or accelerate the administration of rTMS (aTMS) by administering multiple sessions of rTMS over a shorter period of time to have equivalent efficacy in shorter period of time. Various studies of aTMS (2-9) have been safely conducted with anywhere from 2 (3) to 10 (2) sessions of rTMS a day for a total of 9 (5) - 20 (4, 7) sessions of TMS over 2 (2) to 9 (8) days. These studies showed that aTMS was safe and efficacious, with no significant side effects reported and a high level of patient acceptability and significant improvements in subjects' depression after the aTMS. However, there is no data on whether subjects who do not response to aTMS will benefit from more of the same TMS or from changing the mode of rTMS. The only study investigating this issue investigated normal rTMS, not aTMS, and did not find a significant difference in response to different forms of rTMS in initial non-responders (10). Our own observations and some preliminary evidence suggest that there may be a delayed response to TMS in some patients (11, 12). Thus, instead of the usual practice of giving 4-6 weeks stimulation (every weekday) and assessing for response at the end of the stimulation period, the same outcome may be achieved by giving a shorter period of stimulation (eg 1 weeks), waiting 2-4 weeks, then assessing response and the need for further TMS treatment. Further, giving more than 1 treatment per day has been shown to be effective (13) and may lead to more efficient treatment, i.e. fewer days to response and less requirement for patient attendance at the treatment centre (2-9). This pilot study will contribute to existing knowledge by being possibly the first group in South East Asia to investigate the immediate and delayed efficacy of aTMS in the local population (i.e. in an Asian setting) as well as whether continuing or changing the type of rTMS is more efficacious in subjects who do not respond to initial aTMS.