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Review
Interrogating cortical function with transcranial magnetic stimulation: insights from neurodegenerative disease and stroke
  1. Smriti Agarwal1,
  2. Giacomo Koch2,3,
  3. Argye E Hillis4,5,6,
  4. William Huynh1,
  5. Nick S Ward7,8,9,
  6. Steve Vucic10,
  7. Matthew C Kiernan1
  1. 1Brain and Mind Centre, University of Sydney, and Institute of Clinical Neurosciences, Royal Prince Alfred Hospital, Sydney, New South Wales, Australia
  2. 2Non-Invasive Brain Stimulation Unit, Neurologia Clinica e Comportamentale, Fondazione Santa Lucia IRCCS, Rome, Italy
  3. 3Stroke Unit, Department of Neuroscience, Policlinico Tor Vergata, Rome, Italy
  4. 4Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
  5. 5Physical Medicine and Rehabilitation, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
  6. 6Cognitive Science, Johns Hopkins University, Baltimore, Maryland, USA
  7. 7Sobell Department of Motor Neuroscience, UCL Institute of Neurology, University College London, London, UK
  8. 8UCL Partners Centre for Neurorehabilitation, UCL Institute of Neurology, University College London, London, UK
  9. 9The National Hospital for Neurology and Neurosurgery, London, UK
  10. 10Westmead Clinical School, University of Sydney, Sydney, Australia
  1. Correspondence to Dr Smriti Agarwal, Brain and Mind Centre, University of Sydney, Sydney, New South Wales, Australia; smriti.agarwal{at}cantab.net

Abstract

Transcranial magnetic stimulation (TMS) is an accessible, non-invasive technique to study cortical function in vivo. TMS studies have provided important pathophysiological insights across a range of neurodegenerative disorders and enhanced our understanding of brain reorganisation after stroke. In neurodegenerative disease, TMS has provided novel insights into the function of cortical output cells and the related intracortical interneuronal networks. Characterisation of cortical hyperexcitability in amyotrophic lateral sclerosis and altered motor cortical function in frontotemporal dementia, demonstration of cholinergic deficits in Alzheimer’s disease and Parkinson’s disease are key examples where TMS has led to advances in understanding of disease pathophysiology and potential mechanisms of propagation, with the potential for diagnostic applications. In stroke, TMS methodology has facilitated the understanding of cortical reorganisation that underlie functional recovery. These insights are critical to the development of effective and targeted rehabilitation strategies in stroke. The present review will provide an overview of cortical function measures obtained using TMS and how such measures may provide insight into brain function. Through an improved understanding of cortical function across a range of neurodegenerative disorders, and identification of changes in neural structure and function associated with stroke that underlie clinical recovery, more targeted therapeutic approaches may now be developed in an evolving era of precision medicine.

  • magnetic stimulation
  • stroke
  • motor neuron disease
  • dementia
  • parkinson’s disease

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Footnotes

  • Contributors MCK and SA conceived the idea for the article. SA drafted the manuscript. All authors revised the manuscript critically for important intellectual content and gave final approval of the version to be published.

  • Funding This work was supported by funding to Forefront, a collaborative research group dedicated to the study of motor neuron disease, from the National Health and Medical Research Council of Australia program grant (#1037746), the Motor Neuron Research Institute of Australia Ice Bucket Challenge Grant and grant aid from Magnetic Health Science Foundation. SA was funded by the Ellison-Cliffe travelling fellowship from the Royal Society of Medicine, UK. AH was funded by NIH P50 DC014664 and NIH ROI DC05375.

  • Competing interests None declared.

  • Patient consent Not required.

  • Provenance and peer review Commissioned; externally peer reviewed.

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