THETA BURST STIMULATION
Theta Burst Stimulation
Theta Burst Stimulation (TBS) is a newer form of TMS (transcranial magnetic stimulation).
Here, the magnetic pulses are applied in a certain pattern, called bursts. Research studies with TBS have been shown to produce similar if not greater effects on brain activity compared to standard rTMS (repetitive transcranial magnetic stimulation).
Conventional TMS procedures typically last up to 37 minutes per session whereas TBS can go down to as little as a few minutes' duration.
The standard theta burst pattern consists of three bursts of pulses given at 50 Hz and repeated every 200 ms.
The two most widely used TBS patterns are:
Continuous (cTBS) stimulation. Here, a 40 second train of uninterrupted TBS is given on the right dorsolateral prefrontal cortex and typically 600 pulses.
lntermittent stimulation (iTBS). Here, 2 seconds of stimulation on the left dorsolateral prefrontal cortex is followed by an 8 second pause, for example for a total of 190 seconds and typically 600 pulses.
In August 2018, FDA cleared a 3-minute TBS protocol for treatment of major depressive disorder. The FDA cleared protocol was based on a clinical study - the THREE-D trial - which was led in partnership by three leading research hospitals in Canada (CAMH, UHN, and UBC). The THREE-D trial is the largest, double-blinded, randomized TMS trial to date involving 414 participants suffering from major depressive disorder. The article was published in The Lancet in 2018.