Dorsal root ganglia hypertrophy as in vivo correlate of oxaliplatin-induced polyneuropathy

PURPOSE: To investigate in vivo morphological and functional correlates of oxaliplatin-induced peripheral neuropathy (OXA-PNP) by magnetic resonance neurography (MRN). METHODS: Twenty patients (7 female, 13 male, 58.9±10.0 years) with mild to moderate OXA-PNP and 20 matched controls (8 female, 12 male, 55.7±15.6 years) were prospectively enrolled. All patients underwent a detailed neurophysiological examination prior to neuroimaging. A standardized imaging protocol at 3.0 Tesla included the lumbosacral plexus and both sciatic nerves and their branches using T2-weighted fat-saturated sequences and diffusion tensor imaging. Quantitative assessment included volumetry of the dorsal root ganglia (DRG), sciatic nerve normalized T2 (nT2) signal and caliber, and fractional anisotropy (FA), mean diffusivity (MD), axial (AD) and radial diffusivity (RD). Additional qualitative evaluation of sciatic, peroneal, and tibial nerves evaluated the presence, degree, and distribution of nerve lesions. RESULTS: DRG hypertrophy in OXA-PNP patients (207.3±47.7mm(3) vs. 153.0±47.1mm(3) in controls, p = 0.001) was found as significant morphological correlate of the sensory neuronopathy. In contrast, peripheral nerves only exhibited minor morphological alterations qualitatively. Quantitatively, sciatic nerve caliber (27.3±6.7mm(2) vs. 27.4±7.4mm(2), p = 0.80) and nT2 signal were not significantly changed in patients (1.32±0.22 vs. 1.22±0.26, p = 0.16). AD, RD, and MD showed a non-significant decrease in patients, while FA was unchanged. CONCLUSION: OXA-PNP manifests with morphological and functional correlates that can be detected in vivo by MRN. We report hypertrophy of the DRG that stands in contrast to experimental and postmortem studies. DRG volume should be further investigated as a biomarker in other sensory peripheral neuropathies and ganglionopathies.