The degenerome-a novel streamline-wise approach for white matter integrity in neurodegeneration.

Neurodegenerative diseases impair both gray matter and long-range white-matter pathways. Existing diffusion MRI approaches are either local or depend on predefined parcellations, limiting their ability to capture distributed network disruption. We introduce a streamline-wise framework to map axonal degeneration and derive disease-specific fiber "degeneromes" across Alzheimer's disease (AD), Parkinson's disease (PD), multiple system atrophy (MSA), and progressive supranuclear palsy (PSP). We analyzed diffusion microstructure imaging and T1-weighted MRI (3 T Siemens Prisma, 2018-2024) in AD (n = 81), PD (n = 177), MSA (n = 50), PSP (n = 35), and healthy controls (n = 26). The intraaxonal volume fraction, estimated via a Bayesian three-compartment model, was mapped along ~20,000 normative streamlines in MNI space using age- and sex-adjusted regression with FDR correction. Streamline-wise mapping revealed disease-specific degeneromes consistent with established pathoanatomical models: AD involved limbic and temporo-occipital pathways, PD showed commissural and posterior association involvement, MSA affected pontocerebellar and corticospinal tracts, and PSP involved the dentato-rubro-thalamic tract and superior cerebellar peduncle. These signatures supported group-level differentiation, and streamline-wise z-scores enabled intuitive single-patient visualization. Fiber degeneromes offer a connectome-informed biomarker with strong biological plausibility, discriminatory potential across neurodegenerative entities, and a clear route toward clinical single-patient reporting.