ABSTRACT NUMBER: ESOC2026A1307 NODDI METRICS CORRELATED WITH HAND-GRIP RECOVERY AFTER STROKE: A LONGITUDINAL MULTI-SHELL DIFFUSION MRI STUDY

Abstract Background and aims Fractional anisotropy (FA) is an established MRI biomarker of stroke motor recovery, but conventional single-shell diffusion imaging has limited sensitivity, particularly in the chronic phase. Multi-shell diffusion enables improved modeling of white matter micro-structure using biophysical approaches such as Neurite Orientation Dispersion and Density Imaging (NODDI). This study aimed to evaluate the clinical relevance of NODDI metrics in relation with hand-grip recovery across acute and chronic phases. Methods Twelve patients (9 men; mean age 59.3±14.2 years) were assessed at 7 days (M0) and 6 months (M6) post-stroke. Paretic hand-grip strength and MRI were acquired at both time-points. Structural sequences and a five-shell diffusion-weighted sequence (7 directions b=0, 6 b=500, 15 b=1000, 15 b=2000, 59 b=3000) were acquired on a 3T MRI. Diffusion data were processed using MRtrix3 and TractSeg. FA, Neurite Density Index (NDI), and Orientation Dispersion Index (ODI) were extracted along the corticospinal tract (CST). Hand-grip values were converted to age- and sex-adjusted Z-scores. Wilcoxon signed-rank tests and Spearman correlations were used for statistical analyses. Results At M0, FA and ODI differed significantly between ipsilesional (-i) and contralesional CST, whereas NDI did not. At M6, all showed significant differences (Figure). FA-i and ODI-i at M0 correlated with hand-grip at M0 (p=0.002 and p=0.005) and M6 (p=0.004 and p=0.002). At M6, ODI-i (p=0.043) and NDI-i (p=0.019), but not FA (p=0.065) correlated with hand-grip at M6. Conclusions ODI and NDI may provide complementary information beyond FA. ODI appears more sensitive in the acute phase, whereas NDI may be more relevant in the chronic phase. Conflict of interest Gourieux: nothing to disclose. Jaillard: nothing to disclose. Krainik: Geodaisics. Detante: nothing to disclose.Legris: nothing to disclose. Pietras: nothing to disclose. Delphin: nothing to disclose Figure 1 - belongs to Results