Biomarkers Obtained by Transcranial Magnetic Stimulation of the Motor Cortex in Epilepsy

Melissa Tsuboyama; Harper Lee Kaye; Alexander Rotenberg

doi:10.3389/fnint.2019.00057

Biomarkers Obtained by Transcranial Magnetic Stimulation of the Motor Cortex in Epilepsy

Front Integr Neurosci. 2019 Oct 30:13:57. doi: 10.3389/fnint.2019.00057. eCollection 2019.

Authors

Melissa Tsuboyama^{1

2}, Harper Lee Kaye^{1

2}, Alexander Rotenberg^{1

2

3}

Affiliations

¹ Neuromodulation Program, Department of Neurology, Division of Epilepsy and Clinical Neurophysiology, Boston Children's Hospital, Boston, MA, United States.
² FM Kirby Neurobiology Center, Department of Neurology, Boston Children's Hospital, Boston, MA, United States.
³ Berenson-Allen Center for Noninvasive Brain Stimulation, Beth Israel Deaconess Medical Center, Boston, MA, United States.

Abstract

Epilepsy is associated with numerous neurodevelopmental disorders. Transcranial magnetic stimulation (TMS) of the motor cortex coupled with electromyography (EMG) enables biomarkers that provide measures of cortical excitation and inhibition that are particularly relevant to epilepsy and related disorders. The motor threshold (MT), cortical silent period (CSP), short interval intracortical inhibition (SICI), intracortical facilitation (ICF), and long interval intracortical inhibition (LICI) are among TMS-derived metrics that are modulated by antiepileptic drugs. TMS may have a practical role in optimization of antiepileptic medication regimens, as studies demonstrate dose-dependent relationships between TMS metrics and acute medication administration. A close association between seizure freedom and normalization of cortical excitability with long-term antiepileptic drug use highlights a plausible utility of TMS in measures of anti-epileptic drug efficacy. Finally, TMS-derived biomarkers distinguish patients with various epilepsies from healthy controls and thus may enable development of disorder-specific biomarkers and therapies both within and outside of the epilepsy realm.

Keywords: biomarker (development); classification; drug development and application; drug therapy; epilepsy—abnormalities; motor cortex excitability; neuromodulation; transcranial magnetic stimulation (TMS).