Characterising Manual Dexterity, Motor Cortex Neuroplasticity and Intracortical Inhibition Long After Burn Injury

Purpose Persistent motor dysfunction after burn injury may be due to altered motor cortex and corticospinal tract function. This study examined manual dexterity, motor cortex neuroplasticity, and intracortical inhibition in former burn patients 1–3 years post-minor injury (<10% TBSA).

Thirty former burn patients (TBSA: 0.78 ± 1.08%) and 30 non-injured controls participated. Manual dexterity was assessed using the Purdue Pegboard. Transcranial magnetic stimulation (TMS) was used to measure motor cortex excitability (motor evoked potential (MEP) amplitude) and short- and long-interval intracortical inhibition (SICI, LICI) before and after paired-associative stimulation (PAS) to induce neuroplasticity.

Former burn patients performed worse than controls on the bilateral assembly subtest of the Purdue Pegboard. PAS did not induce changes in MEP amplitude but increased LICI in both former burn patients and control participants. In former burn patients, greater baseline SICI and LICI were associated with better bilateral performance.

These findings suggest that poorer motor function persists following minor burn injury and is associated with reduced excitability of motor cortex inhibitory circuits. Further research should explore whether targeting motor cortex inhibitory circuits can improve motor performance following burn injury. Highlights Former burn patients 1–3 years post-minor injury had poorer manual dexterity than controls. Paired associative stimulation increased long-interval intracortical inhibition. Greater motor cortex inhibition at rest linked to better manual dexterity in former burn patients. Competing Interest Statement The authors have declared no competing interest. Funding Statement This project was funded by a National Health and Medical Research Ideas Grant (GNT2004107) and the Fiona Wood Foundation. Ann-Maree Vallence was supported by an Australian Research Council Discovery Early Career Researcher Award (DE190100694). Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The experimental protocol was performed in accordance with the Declaration of Helsinki and was approved by the Murdoch University (2021/047) and South Metropolitan Health Service Human Research Ethics Committee (RGS0000004279). I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes Data Availability The primary data are available via https://osf.io/3xfkp/?view_only=48fa8a1f1b1c473d9e7f4748f61ecaf0 https://osf.io/3xfkp/?view_only=48fa8a1f1b1c473d9e7f4748f61ecaf0