Pallidal Volumetry and Neutrophil-to-Lymphocyte Ratio in Differentiating Progressive Supranuclear Palsy from Parkinson's Disease.

BACKGROUND: Progressive supranuclear palsy (PSP) and Parkinson's disease (PD) frequently present with overlapping clinical features, creating diagnostic challenges, particularly during the early stages of disease. Structural MRI and peripheral inflammatory biomarkers may provide complementary information for differential diagnosis. OBJECTIVE: To evaluate the diagnostic performance of automated pallidal volumetry and the neutrophil-to-lymphocyte ratio (NLR), individually and in combination, for distinguishing PSP from PD. METHODS: This retrospective case-control study included 12 patients with PSP and 12 patients with PD. Automated brain volumetry was performed using the volBrain 2.0 platform. Total pallidal volume was selected as the primary imaging biomarker based on its established involvement in PSP pathology. NLR was calculated from routine blood counts. Diagnostic performance was assessed using receiver operating characteristic (ROC) analysis. A combined MRI-blood model was constructed using binary logistic regression. RESULTS: Patients with PSP demonstrated lower normalized pallidal volumes than patients with PD. Pallidal volume showed high diagnostic performance for differentiating PSP from PD (AUC = 0.885), whereas NLR demonstrated only modest discriminatory ability (AUC = 0.715). The combined pallidal volume-NLR model achieved an AUC of 0.903 compared with 0.885 for pallidal volumetry alone, but this difference was not statistically significant (DeLong p = 0.732), and sensitivity, specificity and overall accuracy remained unchanged. CONCLUSIONS: Automated pallidal volumetry provided substantially better discrimination between PSP and PD than NLR alone. Although the combined model showed a small numerical increase in AUC, this improvement was not statistically significant and did not alter sensitivity, specificity or overall accuracy. These findings do not demonstrate incremental diagnostic value of NLR beyond pallidal volumetry in this cohort. Larger prospective studies are needed to determine the clinical utility of combined MRI-blood biomarker approaches in PSP.