Evidence of Altered Corticomotor Inhibition in older Adults with a History of Repetitive Neurotrauma. A Transcranial Magnetic Stimulation study

International concern continues regarding the association between the long-term neurophysiologic changes from repetitive neurotrauma associated with contact and collision sports. This study describes corticomotor changes in retired contact/collision sport athletes and controls, between the ages of 30 and 70 years. Retired athletes (n=152; 49.1±8.5 years) and controls (n=72; 47.8±9.5 years) were assessed using single and paired-pulse transcranial magnetic stimulation (TMS) for active motor threshold (aMT), motor evoked potential and cortical silent period duration (expressed as MEP:cSP ratio), and short- and long-interval intracortical inhibition (SICI and LICI). Motor threshold, MEP:cSP, SICI and LICI for both groups were correlated across age. Controls showed significant moderate correlations for MEP:cSP ratios at 130% (rho=0.48, p<0.001), 150% (rho=0.49, p<0.001) and 170% aMT (rho=0.42; p<0.001) and significant small negative correlation for SICI (rho=-0.27; p=0.030), and moderate negative correlation for LICI (rho=-0.43; p<0.001). Group-wise correlation analysis comparisons showed significant correlation differences between groups (all p<0.05), specifically showing retired athletes were displaying increased corticomotor inhibition. while previous studies have focussed studies on older athletes (>50 years), this study is the first to characterize corticomotor differences between retired athletes and controls across the lifespan. These results, demonstrating pathophysiological differences in retired athletes across the lifespan, provide a foundation to utilise evoked potentials as a prodromal marker in supplementing neurological assessment for traumatic encephalopathy syndrome associated with contact/collision sport athletes that is currently lacking physiological biomarkers.