Resting motor threshold changes and clinical response to prefrontal repetitive transcranial magnetic stimulation in depressed patients

Abstract

Aims: Several variables are able to influence the antidepressant effects of repetitive transcranial magnetic stimulation (rTMS), particularly the intensity of stimulation, which is generally expressed according to the resting motor threshold (RMT). The aim of our study was to investigate whether or not RMT changes during the treatment of resistant depression by rTMS and whether these fluctuations could alter treatment outcome. Methods: Seventy‐five inpatients suffering from unipolar or bipolar treatment‐resistant depression and who had been antidepressant‐free or taking a stable antidepressant drug and a daily dose of benzodiazepine for at least a month received a left prefrontal rTMS session once a day for 10 days at 10 Hz and 95% RMT. Results: For the whole group, no significant fluctuation of RMT was observed between the first and the second week of rTMS treatment. However, RMT increased, decreased or remained constant throughout treatment depending on the patient. These RMT changes influenced the outcome of the 10 sessions concerning the severity of depressive and anxiety symptoms, measured by the Beck Depression Inventory and State Trait Anxiety, respectively. Conclusions: Our results justify calculating RMT regularly, and suggest that its variations play a role in treatment outcome.

Resting motor threshold changes in vagus nerve stimulation‐treated patients during on/off‐stimulation conditions

“…As shown in recently published studies, however, rMT does not appear to be a static variable and changes in motor cortex excitability are implicated, similar to previous results. 3,6,7 The present results suggest that VNS affects the motor cortex by increasing motor excitability, thereby reducing rMT. This reduction should be discussed as a significant indicator of increased responsiveness of the frontal and motor cortex due to VNS.…”

Neurobiological Predictors of Response to Dorsolateral Prefrontal Cortex Repetitive Transcranial Magnetic Stimulation in Depression: A Systematic Review

“…1). [13, 14, 16-18, 20, 22, 24, 25, 28, 29, 31-35, 37-45, 47, 49, 50, 59] Twenty-five studies include experiments that examined neurobiological predictors of response at baseline, [13-17, 19-24, 26-35, 37, 42, 44, 59] six studies included experiments that examined changes to neurobiological factors pre-post a course of rTMS, [18,25,36,41,49,51] and 10 studies examined both a baseline predictor and pre-post experiment. [15, 24-46, 48-51, 59] Four studies investigated only the effects of low-frequency right-sided (LFR) rTMS, [21,27,36,48] whereas eight studies investigated the effects of LFR and high-frequency left-sided (HFL) rTMS combined.…”

“…[38] In terms of TMS neurophysiology for motor cortex, resting motor threshold variations played a role in conferring treatment outcome. [25,36] Larger size of right-sided motor evoked potential (MEP), and longer duration of left side cortical silent period (CSP) at baseline were associated with poorer clinical response after bilateral rTMS, whereas larger short-interval intracortical inhibition (SICI) was associated with poorer clinical response post HFL-rTMS. [19] Here, MEP was correlated with motor excitability, CSP is one of the indices of intracortical inhibition assumed to be mediated by gamma-aminobutyric acid-B (GABA B ) receptor function, and SICI mainly reflects cortical inhibition mediated by GABA A receptor.…”

“…[15,19,23,26,30,46,51,58] The remaining 29 studies examined the effects of HFL-rTMS alone. [13, 14, 16-18, 20, 22, 24, 25, 28, 29, 31-35, 37-45, 47, 49, 50, 59] Twenty-five studies include experiments that examined neurobiological predictors of response at baseline, [13-17, 19-24, 26-35, 37, 42, 44, 59] six studies included experiments that examined changes to neurobiological factors pre-post a course of rTMS, [18,25,36,41,49,51] and 10 studies examined both a baseline predictor and pre-post experiment. [38-40, 43, 45-48, 50, 58] The number of studies that fell into each of the strength category were as follows; strength 1 was 9, strength 2 was 20, strength 3 was 5, and strength 4 was 7.…”

Changes in motor cortex excitability associated with temporal repetitive transcranial magnetic stimulation in tinnitus: hints for cross-modal plasticity?

“…In this study we found no effects for other excitability measures. Since RMT, ICF and CSP are rather modulated by other neurotransmitters and -receptors, our findings highlight the role of GABAA mediated neurotansmission in rTMS treatment effects in tinnitus [41,42]. We are well aware that this interpretation is highly speculative and needs to be confirmed by further studies, before further conclusions can be drawn.…”