A compositional framework for quantifying neurophysiological motor recovery after stroke

Stroke is a leading cause of disability, often resulting in functional impairments that limit the performance of everyday tasks. The aim of this thesis was to better understand the neurophysiology of upper limb recovery after stroke by introducing a novel compositional analysis framework - the threshold matrix. The threshold matrix explores peri-threshold activation of the corticomotor pathway from transcranial magnetic stimulation-derived motor evoked potentials (MEPs) by characterising suprathreshold, subthreshold, and subliminal responses based on conventional resting threshold criteria. A review of current transcranial magnetic stimulation methodologies and potential use of the threshold matrix precedes the three study chapters that assessed the reliability and sensitivity of the matrix. The first study evaluated the test-retest reliability of the threshold matrix in 23 healthy older adults. The suprathreshold and subliminal elements had good to excellent reliability, whereas the subthreshold element had poor reliability. The subthreshold element was not confounded by resting motor threshold intensity or brain hemisphere. The second study assessed the threshold matrices of 25 participants at one, three, and six months post-stroke. There were more sub- and less supra-threshold MEPs on the paretic compared to the non-paretic side one month after stroke. The prevalence of suprathreshold MEPs on the paretic side increased between one and six months but was not associated with hand dexterity recovery. The third study obtained threshold matrices from 25 acute stroke patients to explore whether the threshold matrix could improve the prediction accuracy of upper limb motor outcomes. The matrix was not associated with outcomes, and subthreshold MEPs had lower test-retest reliability than subliminal and suprathreshold MEPs. Together, these studies suggest that while subthreshold MEPs may capture transient and potentially informative post-stroke neurophysiological changes, the relationship between composite neurophysiological metrics and upper limb recovery remains unclear. To date, a binary measure of MEP status remains the most effective prognostic and predictive biomarker for upper limb recovery after stroke. The findings from this thesis contribute to a deeper understanding of the neurophysiology of upper limb recovery after stroke.

Name thesis:degree_name

PhD

Level thesis:degree_level

Doctoral

Discipline thesis:degree_discipline

Exercise Sciences

Grantor dc:publisher

ResearchSpace@Auckland

Year dc:date.issued

2024

Author dc:creator

• Shanks, Maxine Jemima

Advisors dc:contributor.advisor

• Byblow, Winston
• Stinear, Cathy
• Cirillo, John

• Stroke
• Neurophysiology
• Transcranial Magnetic Stimulation
• Motor evoked potential
• Upper limb

Statement dc:rights

• Items in ResearchSpace are protected by copyright, with all rights reserved, unless otherwise indicated.

Licence dc:rights.uri

• https://researchspace.auckland.ac.nz/docs/uoa-docs/rights.htm

Handle dc:identifier.uri

https://hdl.handle.net/2292/72067

OAI identifier oai:identifier

oai:researchspace.auckland.ac.nz:2292/72067