ABSTRACTPurpose: We compared injected, assumed to be symptomatic, and non-injected, assumed to be asymptomatic, dorsal root ganglia (DRG) in patients receiving lumbar facet and/or nerve injections using DTI MRI data and foraminal stenosis (FS) and canal stenosis (CS) grades. Materials and Methods: Healthy volunteers (HVs) and patients receiving lumbar facet and/or nerve block injections for pain underwent lumbar MRIs including axial T2-weighted fat-water separated FLEX 3D FSE and axial DTI. Patients were imaged up to a month prior to injection and up to six months after injection. Processing included: DRG segmentation (MD.ai), 3D volume (MorphACE), DTI (spherical harmonic and Constant Solid Angle). ADC, FA and volume were compared between HVs, asymptomatic and symptomatic DRG and correlated with stenosis grades using paired t-tests. Results: 25 patients and 5 HVs DTI scans were analyzed (34 patients and 10 HVs for volume). There was a sequential increase in DRG volume from cranial-caudal L1-S1 in the HVs (p<0.001). Symptomatic DRG had higher FA than asymptomatic DRG before injection (p<0.01) and symptomatic DRG FA decreased after injection (p<0.05) while asymptomatic DRG FA slightly increased. Severe CS was associated with lower ADC than no or mild CS (p<0.001). Conclusion: Cranial-caudal sequential increase in DRG volume from L1-S1, consistent with cadaver data, may reflect degree of cutaneous and muscle area/volume innervation. Symptomatic DRG have higher FA than asymptomatic DRG that return to asymptomatic levels after injection. This could be due to phospholipase A2 (PLA2) inhibition by corticoid-steroid suppressing nerve cell growth and thus organized diffusion alternatively receptor inhibition. Severe CS could cause arterial flow constriction leading to ischemic DRG and reduced ADC.