Optimising parameters of transcranial magnetic stimulation to efficiently treat treatment-resistant post-traumatic stress disorder

Abstract

Post-traumatic stress disorder (PTSD) is a psychiatric disorder following exposure to a traumatic event, and is characterised by a dysregulation in the “fear-extinction” network, causing hyperactivity in the amygdala, hypoactivity in the prefrontal cortex and reduced hippocampal volumes. While trauma-focused psychotherapies and pharmacotherapy are standard first-line treatments, approximately 30–50% of patients fail to achieve remission, highlighting a clinical treatment gap for treatment-resistant populations. This review examines the potential of repetitive transcranial magnetic stimulation (rTMS) as a novel neuromodulatory intervention for PTSD. It particularly investigates the influence of stimulation location (left versus right prefrontal cortex), stimulation frequency (low versus high frequency), and protocol type (standard rTMS versus theta burst stimulation (TBS) versus deep TMS) on clinical efficacy. Current literature suggests that rTMS is efficient in treating PTSD compared to control groups. Regarding the parameters stimulation location and frequency, there was no consensus on optimal settings for treating PTSD. Studies did however show significant treatment effects with multiple combinations of these parameters, but more research would need to be conducted to determine whether there are optimal parameters. Regarding the protocol type parameter, iTBS showed non-inferiority to standard rTMS and superiority to sham stimulation; as the treatment time for iTBS is much shorter than that of rTMS, implementing iTBS to treat PTSD could lead to improved clinical efficacy. Deep TMS and rTMS as an adjunctive therapy to psychotherapies showed less promising results, but more studies should appoint whether this holds for larger trials. In conclusion, rTMS appears to be a promising, potential treatment for treatment-resistant PTSD. More large, randomised, sham-controlled trials are necessary to determine whether there are optimal stimulation parameters, or whether there are multiple paradigms that might improve PTSD symptoms.