Evaluation of the DTI-ALPS index in neuromyelitis optica spectrum disorder: a cross-sectional study of its correlation with disease duration and disability

PURPOSE: This study evaluates the utility of the Diffusion-Tensor Imaging Analysis along the Perivascular Space (DTI-ALPS) index as an imaging marker for neuromyelitis optica spectrum disorder (NMOSD). We investigated its correlation with disease duration, clinical severity, and its specificity relative to a Multiple Sclerosis (MS) cohort. METHODS: We conducted a cross-sectional study involving patients with NMOSD (n = 21), RRMS (n = 42), and healthy controls (n = 34). DTI-ALPS values were calculated from 3T MRI data using a standardized automated pipeline. Correlations between DTI-ALPS and clinical metrics-including the Expanded Disability Status Scale (EDSS) and disease duration-were analyzed. Comparisons were performed between all three groups to assess the index's ability to differentiate neuroinflammatory pathologies. RESULTS: = 0,241). In the NMOSD group, a significant negative correlation was found between DTI-ALPS and EDSS (R = -0.462, P = 0.011), whereas no such association was observed in the MS cohort (R = -0.035, P = 0.772). Furthermore, disease duration strongly correlated with the ALPS index (R = -0.799, P = 0.013), with patients exceeding five years of disease showing a more pronounced decline in perivascular diffusivity. CONCLUSION: The DTI-ALPS index is a sensitive marker for capturing cumulative neuroinflammatory and neurodegenerative changes in NMOSD. Interestingly, the correlation with clinical disability was unique to the NMOSD group, suggesting that the index may track disease progression differently across demyelinating pathologies. While the index successfully differentiates patients from healthy individuals, the comparable values found in the MS cohort suggest that DTI-ALPS reflects a common pathway of image biomarker for glymphatic or microstructural impairment across demyelinating diseases rather than NMOSD-specific pathology. These findings support its use as a rapid, complementary metric for monitoring disease progression at a group level.