Brain Entropy and Complexity as Biomarkers of Neuroplasticity in Neurorehabilitation—A Scoping Review

BACKGROUND: Neurorehabilitation in physiotherapy depends on experience-dependent neuroplasticity; however, conventional clinical outcomes may lack sensitivity to capture dynamic neural adaptations underlying recovery. Brain entropy and complexity measures derived from EEG and neuroimaging have emerged as potential biomarkers of neural adaptability. OBJECTIVE: To map and synthesize evidence on brain entropy and complexity as biomarkers of neuroplasticity in neurorehabilitation, with relevance to physiotherapy practice. METHODS: A scoping review was conducted following PRISMA-ScR guidelines. PubMed, Scopus, and Web of Science were searched up to August 2025 for studies reporting quantitative entropy or complexity measures in neurological populations undergoing rehabilitation or task-based assessment. RESULTS: Eight studies were included. Interventional studies in stroke and brain injury populations reported moderate to large within-group neural effects, with increases in entropy or complexity accompanying functional improvement following task-oriented, robotic, or brain-computer interface-based rehabilitation. Studies of higher methodological quality demonstrated more consistent entropy-outcome associations, whereas lower-quality observational studies showed greater variability. Degenerative neurological conditions are characterized by reduced neural complexity. DISCUSSION: Brain entropy and complexity measures are sensitive indicators of neuroplastic change and may complement clinical outcomes in physiotherapy. Although not yet ready for routine clinical decision-making, these biomarkers show promise for monitoring intervention response and guiding personalized rehabilitation, pending methodological standardization and longitudinal validation.