Axonal Sprouting and the Self: A Conceptual Gap in Biomarkers of Spinal Cord Repair

This preprint is a Matters Arising commentary on the recent Nature Communications article by Farner et al. (2026) reporting that anti-Nogo-A (NG101) treatment slows spinal cord degeneration and promotes fiber sprouting after acute cervical spinal cord injury. While the NISCI phase 2b imaging data represent a landmark advance, the authors' interpretation of their MRI biomarkers as evidence of "neural repair" raises a conceptual question that the paper does not address. The language of "axonal sprouting," "new connections," and "circuit rewiring" implies structural remodeling of central nervous system circuitry—not merely preservation of existing tissue. This commentary argues that structural remodeling and faithful restoration are not equivalent, and that this distinction matters for what "repair" means for the person. Drawing on philosophical accounts of personal identity (Parfit, Schechtman) and the neuroethics of deep brain stimulation, the piece proposes that future regenerative spinal cord injury trials incorporate qualitative patient-reported outcome measures on self-concept and bodily experience, complementing the quantitative imaging and electrophysiological biomarkers the authors elegantly describe. Keywords: spinal cord injury, Nogo-A, axonal sprouting, neural repair, personal identity, neuroethics, biomarkers, patient-reported outcomes