Repetitive Transcranial magnetic stimulation (TMS) uses magnetic fields to modulate brain activity. A novel form of repetitive TMS (rTMS), intermittent theta burst stimulation (iTBS), has emerged as a promising new treatment for depression. This technique may be advantageous due to its very short duration and potentially stronger effect on brain activity in comparison with standard rTMS. However, the exact effect of iTBS on the activity of the brain in clinical populations remains poorly understood. This project aims to improve understanding of the mechanisms of action of iTBS by comparing its neuronal effect to sham treatment in 22 individuals with a diagnosis of major depressive episode, using positron emission tomography (PET) and magnetic resonance imaging (MRI) in a double-blind cross-over experiment, followed by a 6-week daily treatment course of iTBS.
Repetitive transcranial magnetic stimulation (rTMS) is a Health Canada approved treatment for major depression. Typical clinical rTMS treatment is delivered on the left dorsolateral prefrontal cortex (DLPFC) at a 10 Hz frequency for 30-45 minutes to increase cortical excitability which will outlast the duration of stimulation. The treatment involves daily sessions that are applied over a four to six-week period. Intermittent theta burst stimulation (iTBS) is a novel refinement of conventional rTMS. iTBS consists of bursts of 3 stimulations at 50 Hz at theta frequency (5 Hz). However, instead of 30-min treatment sessions, iTBS has comparable clinical efficacy with only 3 minutes treatment sessions. Because iTBS is a novel technique, much of its effects on the brain are currently unknown. However, since it is a modified rTMS protocol, it is assumed that its neuronal effects are comparable. Therapeutic effects of rTMS are thought to be related to its effects on the subgenual anterior cingulate cortex (sgACC; Broadman area 25). In depression, metabolic activity of the sgACC is increased (measured as increase of 18F-labeled fluorodeoxyglucose (\[18F\]FDG) uptake with positron emission tomography (PET)). Importantly, the metabolic activity of the sgACC appears to be a general marker for treatment response, e.g. \[18F\]FDG uptake is decreased in response to antidepressant medications or deep brain stimulation. In addition to resting state functional MRI, diffusion weighted imaging has been used to study TMS targets, but this technique has never been used for testing targets for treating depression. Currently, the system level mechanisms of action of iTBS in depression patients are completely unexplored. Based on prior research the investigators hypothesize that 1) a single session of iTBS will decrease \[18F\]FDG uptake in the sgACC and 2) the magnitude of decrease is related to the connectivity between the target site and the sgACC. This study will establish the system level mechanisms of action of iTBS, paving a way to improve clinical treatment. This study will also develop connectivity measures that can be used to improve iTBS targeting (i.e. choose iTBS target based on sgACC connectivity) and predict treatment response (i.e. predict iTBS treatment response in patients based on sgACC connectivity).
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
TRIPLE
Enrollment
22
Cool B65 active/placebo coil (left DLPFC) with X100 MagPro rTMS Device (Magventure A/S, Farum, Denmark)
Cool B70 coil (left DLPFC), with X100 MagPro rTMS Device (Magventure A/S, Farum, Denmark)
The Royal Ottawa Mental Health Centre
Ottawa, Ontario, Canada
Neural mechanisms of iTBS measured by [18F]FDG uptake in the sgACC
The primary outcome measure for Part I is the change in \[18F\]FDG uptake in the sgACC after iTBS.
Time frame: 40 minutes after iTBS
Neuroimaging predictors of iTBS response to treatment - primary measures
The primary clinical outcome measures will be response to treatment and remission. Response to treatment will be defined as at least a 50% reduction in pre-treatment symptoms severity as measured by the mean HRSD-17 score at week 6. Remission will be defined as a HRSD-17 score lower or equal to 7 at week 6.
Time frame: 6 weeks
Neuroimaging predictors of iTBS response to treatment - QIDS-SR16
For secondary analyses, improvement in symptoms will be defined as the percentage of change of symptoms at week 6 in comparison with pre-treatment symptoms severity. Response to treatment will be defined as a 50% reduction in pre-treatment symptoms severity as measured by the mean of the Quick Inventory of Depressive Symptomatology (16-item) (Self-Report) (QIDS-SR16). Remission will be defined as a QIDS-SR score ≤ 6.
Time frame: 6 weeks
Neuroimaging predictors of iTBS response to treatment - Beck Anxiety Inventory (BAI)
For secondary analyses, improvement in symptoms will be defined as the percentage of change of symptoms at week 6 in comparison with pre-treatment symptoms severity. Response to treatment will be defined as a 50% reduction in pre-treatment symptoms severity. The Beck Anxiety Inventory (BAI) will be used to assess severity of patient anxiety. It is a structured 21-item self-report measure using a likert scale of 0-3. A total score of 0 - 7 is interpreted as a "Minimal" level of anxiety; 8 - 15 as "Mild"; 16 - 25 as "Moderate", and; 26 - 63 as "Severe".
Time frame: 6 week
Neuroimaging predictors of iTBS response to treatment - Quality of life (Q-LES-Q-SF)
For secondary analyses, improvement in symptoms will be defined as the percentage of change of symptoms at week 6 in comparison with pre-treatment symptoms severity. Response to treatment will be defined as a 50% reduction in pre-treatment symptoms severity. The Quality of Life Enjoyment and Satisfaction Questionnaire - Short Form (Q-LES-Q-SF) will be used to assess response to iTBS treatment. The Q-LES-Q-SF is used to obtain sensitive measures of the degree of enjoyment and satisfaction experienced by subjects in various areas of daily functioning. It's a structured 16-item self-report measure where items are scored on a 5-point Likert scale, from Very Poor to Very Good.
Time frame: 6 week
Neuroimaging predictors of iTBS response to treatment - Well-being (WEMWBS)
For secondary analyses, improvement in symptoms will be defined as the percentage of change of symptoms at week 6 in comparison with pre-treatment symptoms severity. Response to treatment will be defined as a 50% reduction in pre-treatment symptoms severity. The Short Warwick Edinburgh Mental Well-Being Scale (SWEMWBS) will be used to assess general overview of mental well-being. It's a self-rated; 7 questions; rated over the past 2 weeks. Scored: 1 (none of the time) to 5 (all of the time).
Time frame: 6 week
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