Threshold tracking transcranial magnetic stimulation: Effects of age and gender on motor cortical function

Clin Neurophysiol. 2016 Jun;127(6):2355-61. doi: 10.1016/j.clinph.2016.03.009. Epub 2016 Mar 18.

Abstract

Objective: Recently, the utility of threshold tracking paired-pulse transcranial magnetic stimulation (TTTMS), to measure changes in cortical excitabilitability, has been established for diagnostic purposes across a range of neurological diseases. However, the impact of healthy aging on the GABA-ergic intracortical inhibitory system remains unclear. To improve the clinical applicability, TTTMS was performed across an age spectrum.

Methods: TTTMS, single-pulse TMS and nerve conduction studies (NCS) were performed in 113 healthy subjects aged between 20 and 83years (57 male and 56 female).

Results: Prolonged motor evoked potential (MEP) latency, increased central motor conduction time, decreased compound muscle action potential (CMAP) amplitude, prolonged F-wave latency and decreased neurophysiological index (NI), calculated from CMAP amplitude, latency and F-wave frequency, were observed as subjects aged. In contrast, short interval intracortical inhibition (SICI) and facilitation did not change. Compared to females, males exhibited a reduced SICI and NI along with longer MEP, CMAP with prolonged F-wave latencies. Multivariate analyses revealed similar results.

Conclusion: Utilizing clinically applicable TTTMS protocols, findings suggest that GABA mediated intracortical inhibition may be greater in females but does not significantly change with age.

Significance: These findings may better inform the interpretation of diagnostic TTTMS studies in the clinical setting.

Keywords: Age-related change; Cortex function; Gender-related difference; Healthy subject; Intracortical inhibition; Threshold tracking transcranial magnetic stimulation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Age Factors
  • Aged
  • Aged, 80 and over
  • Evoked Potentials, Motor
  • Female
  • Humans
  • Male
  • Middle Aged
  • Motor Cortex / growth & development
  • Motor Cortex / physiology*
  • Sex Factors
  • Transcranial Magnetic Stimulation*