Using transcranial magnetic stimulation to quantify electrophysiological changes following concussive brain injury: a systematic review

Mild traumatic brain injury (mTBI) and sports concussion are a growing public health concern, with increasing demands for more rigorous methods to quantify changes in the brain post-injury. Electrophysiology, and in particular, transcranial magnetic stimulation (TMS), have been demonstrated to provide prognostic value in a range of neurological conditions; however, no review has quantified the efficacy of TMS in mTBI/concussion. In the present study, we present a systematic review and critical evaluation of the scientific literature from 1990 to 2014 that has used TMS to investigate corticomotor excitability responses at short-term (< 12 months), medium-term (1-5 years), and long-term (> 5 years) post-mTBI/concussion. Thirteen studies met the selection criteria, with six studies presenting short-term changes, five studies presenting medium-term changes, and two studies presenting long-term changes. Irrespective of time post-concussion, change in intracortical inhibition was the most reported observation. Other findings included increased stimulation threshold, and slowed neurological conduction time. Although currently limited, the data suggest that TMS has prognostic value in detecting neurophysiological changes post-mTBI/concussion.

Transcranial magnetic stimulation in autism spectrum disorder: challenges, promise, and roadmap for future research

Autism Spectrum Disorder (ASD) is a behaviorally defined complex neurodevelopmental syndrome characterized by impairments in social communication, by the presence of restricted and repetitive behaviors, interests and activities, and by abnormalities in sensory reactivity. Transcranial magnetic stimulation (TMS) is a promising, emerging tool for the study and potential treatment of ASD. Recent studies suggest that TMS measures provide rapid and noninvasive pathophysiological ASD biomarkers. Furthermore, repetitive TMS (rTMS) may represent a novel treatment strategy for reducing some of the core and associated ASD symptoms. However, the available literature on the TMS use in ASD is preliminary, composed of studies with methodological limitations. Thus, off-label clinical rTMS use for therapeutic interventions in ASD without an investigational device exemption and outside of an IRB approved research trial is premature pending further, adequately powered and controlled trials. Leaders in this field have gathered annually for a two-day conference (prior to the 2014 and 2015 International Meeting for Autism Research, IMFAR) to share recent progress, promote collaboration across laboratories, and establish consensus on protocols. Here we review the literature in the use of TMS in ASD in the context of the unique challenges required for the study and exploration of treatment strategies in this population. We also suggest future directions for this field of investigations. While its true potential in ASD has yet to be delineated, TMS represents an innovative research tool and a novel, possibly transformative approach to the treatment of neurodevelopmental disorders. Autism Res 2015. © 2015 International Society for Autism Research, Wiley Periodicals, Inc.