Time-Dependent Quantitative Magnetic Resonance Imaging Staging of Lumbar Disc Herniation Using T2 Signal-Intensity Ratios

OBJECTIVE: Low back pain is the leading cause of musculoskeletal disability worldwide. Lumbar disc herniation (LDH) commonly causes radiculopathy, yet conventional magnetic resonance imaging may conflate symptomatic pathology with age-related change. We assessed quantitative T2-weighted signal intensity ratios (SIRs) of herniated nucleus pulposus (NP) as an objective biomarker to stage LDH beyond morphology, using internal references (e.g., cerebrospinal fluid) for normalized, comparable measurements. METHODS: This retrospective cross-sectional study analyzed 157 patients (64% male) with magnetic resonance imaging-confirmed LDH and radicular symptoms at a tertiary center (2021). Exclusions included prior surgery, infection, tumor, fracture, or suboptimal imaging. SIRs were calculated for herniated NP relative to cerebrospinal fluid (SIR-NP/CSF), anterior annulus fibrosus (SIR-NP/AF), and adjacent uninvolved NP (SIR-NP/adjNP). Symptom duration groups were acute (4 weeks). Group differences were tested with analysis of variance and Tukey post hoc analyses, adjusting for phenotype (protrusion/extrusion), disc level, age, and sex. RESULTS: SIRs decreased significantly with longer symptom duration (P < 0.001). Mean SIR-NP/CSF declined from 0.30 (acute) to 0.23 (subacute) to 0.12 (chronic) and was the most robust temporal marker. Posterior NP signal intensity decreased from 194 (acute) to 75 (chronic; F = 136.9, P < 0.001). Trends were consistent across ratios and were not explained by phenotype, level, age, or sex. An SIR-NP/CSF threshold