Single-pulse transcranial magnetic stimulation for assessment of motor development in infants with early brain injury

ABSTRACT

Introduction

Single-pulse transcranial magnetic stimulation (TMS) has many applications for pediatric clinical populations, including infants with perinatal brain injury. As a noninvasive neuromodulation tool, single-pulse TMS has been used safely in infants and children to assess corticospinal integrity and circuitry patterns. TMS may have important applications in early detection of atypical motor development or cerebral palsy.

Areas covered

The authors identified and summarized relevant studies incorporating TMS in infants, including findings related to corticospinal development and circuitry, motor cortex localization and mapping, and safety. This special report also describes methodologies and safety considerations related to TMS assessment in infants, and discusses potential applications related to diagnosis of cerebral palsy and early intervention.

Expert opinion

Single-pulse TMS has demonstrated safety and feasibility in infants with perinatal brain injury and may provide insight into neuromotor development and potential cerebral palsy diagnosis. Additional research in larger sample sizes will more fully evaluate the utility of TMS biomarkers in early diagnosis and intervention. Methodological challenges to performing TMS in infants and technical/equipment limitations require additional consideration and innovation toward clinical implementation. Future research may explore use of noninvasive neuromodulation techniques as an intervention in younger children with perinatal brain injury to improve motor outcomes.

Plain Language Summary

Single pulse transcranial magnetic stimulation (TMS) is a safe and noninvasive way to study brain activity in infants and children who have experienced brain injuries around the time of birth. Infants who have had an early brain injury may develop cerebral palsy, a developmental disability that affects movement. TMS uses a device that gives single pulses of energy to activate specific areas of the brain. This can be used to study how the brain connects to the muscles in the body through paths or ‘tracts.’ TMS helps researchers understand the development of the tracts and the potential need for therapy. This article reviews research studies that used TMS in infants and explains how TMS can be used to assess brain development. It also reviews safety considerations and challenges related to using TMS in infants. TMS could be a valuable tool for early diagnosis of cerebral palsy and could also help guide treatments for infants with brain injuries. However, more research is needed, using larger groups of infants, to potentially expand the use of TMS in clinical practice. Future directions include developing infant-specific research tools and using noninvasive brain stimulation to improve recovery for infants with brain injuries.

KEYWORDS:

• Transcranial magnetic stimulation
• perinatal brain injury
• infant
• neuromodulation
• corticospinal tract
• cerebral palsy

Article highlights

• Single-pulse TMS assessment in infants with perinatal brain injury has unique methodological considerations related to brain anatomy and administration in awake, moving infants.

• Single-pulse TMS has demonstrated safety in infants with perinatal brain injury, with appropriate screening and safety procedures.

• Motor cortex localization and assessment of motor evoked potentials using TMS is feasible in infants with perinatal brain injury. Higher stimulation levels are typically required, and responses are less consistent than those observed in adults and older children.

• TMS studies in infants with perinatal brain injury have identified changes to corticospinal tract development and integrity over the first 2 years of life in some infants that may be associated with motor function.

• TMS biomarkers may be useful to inform early diagnosis of cerebral palsy and related rehabilitation therapies; future research in larger sample sizes may more clearly outline the relationship between TMS biomarkers and individual developmental trajectories.

Declaration of Interest

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Reviewer disclosures

Peer reviewers on this manuscript have no relevant financial relationships or otherwise to disclose.

Acknowledgments

The authors thank Sally Jones for editorial contributions.

Additional information

Funding

This work was supported in part by the National Institute of Neurological Disorders and Stroke/Eunice Kennedy Shriver National Institute of Child Health and Human Development (5R01HD098202), and a Foundation for Physical Therapy Research Promotion of Doctoral Studies – Level I Scholarship.