Lumbosacral Plexus Magnetic Resonance Neurography in Autoimmune Nodopathy: A Quantitative Analysis.

Background and purpose: This study aimed to evaluate the diagnostic utility and imaging abnormalities identified through lumbosacral plexus magnetic resonance neurography (L-MRN) in patients with autoimmune nodopathy (AN).

Materials and methods: This retrospective study included 16 patients with AN (12 with anti-NF155, 3 with anti-CNTN1, and 1 with anti-CASPR1 antibodies) and 18 healthy volunteers. Additionally, six AN patients were followed up longitudinally. At baseline, imaging features such as cauda equina enhancement and the presence of the "sleeve sign" were analyzed. The cross-sectional area (CSA) of nerve roots and the nerve-to-muscle T2 signal intensity (nT2s) from L3 to S1 was measured in both the AN baseline and control groups. For the follow-up group, CSA, T2 signal intensity, and radiomics features were evaluated and correlated with clinical parameters.

Results: Characteristic imaging findings in AN included cauda equina enhancement (100%), pre-(90.9%) and postganglionic (72.7%) nerve enhancement, and the sleeve sign (68.8%). The nerve root CSA and nT2s was significantly larger in patients with AN compared to healthy controls (all p<0.001), with no significant difference in cross-sectional area between the pre-and post-treatment groups (p>0.10). However, at L5-0.5cm, the nerve-to-muscle T2 signal intensity was reduced after treatment. (p<0.05) Furthermore, 21 radiomic features were identified in the follow-up group. The change of inflammatory Rasch-Built Overall Disability Scale was significantly positively correlated with the change in L5L_NGTDM_Strength (r=0.89, p<0.05) and significantly negatively correlated with the change in L5R_GLCM_IMC1(r=-0.93, p<0.05) .

Conclusions: Lumbosacral plexus MRN proved to be a valuable diagnostic tool for AN. Radiomic features also emerged as promising imaging biomarkers for assessing treatment efficacy.

Abbreviations: AN＝autoimmune nodopathy; MRN＝ magnetic resonance neurography; EDX=electrodiagnostic; CSA = cross-sectional area; nT2s=nerve-to-muscle T2 signal intensity.