Understanding individual variability in symptoms and recovery following mTBI: A role for TMS-EEG?

The pathophysiology associated with mild traumatic brain injury (mTBI) includes neurometabolic and cytoskeletal changes that have been shown to impair structural and functional connectivity. Evidence that persistent neuropsychological impairments post injury are linked to structural and functional connectivity changes is increasing. However, to date the relationship between connectivity changes, heterogeneity of persistent symptoms and recovery post mTBI has been poorly characterised. Recent innovations in neuroimaging provide new ways of exploring connectivity changes post mTBI. Namely, combined transcranial magnetic stimulation and electroencephalography (TMS-EEG) offers several advantages over traditional approaches for studying connectivity changes post TBI. Its ability to perturb neural function in a controlled manner allows for measurement of causal interactions or effective connectivity between brain regions. We review the current literature assessing structural and functional connectivity following mTBI and outline the rationale for the use of TMS-EEG as an ideal tool for investigating the neural substrates of connectivity dysfunction and reorganisation post mTBI. The diagnostic, prognostic and potential therapeutic implications will also be explored.