Striatal dopamine transporter imaging in Parkinson's disease drug-naïve patients: focus on sexual dysfunction

Introduction: Dopamine is involved in sexual behavior, but dopaminergic imaging studies establishing the relationship between nigrostriatal dopaminergic degeneration and sexual dysfunction (SD) in Parkinson's disease (PD) are lacking. Methods: We retrospectively analyzed clinical and 123I-FP-CIT SPECT data of 43 drug-naïve PD patients. Based on the sexual function domain of the Non-Motor Symptoms Scale (NMSS), we identified 23 patients with sexual concerns (WSC), reporting a score ≥ 2 due to hyposexuality, and 20 patients without sexual concerns (NoSC). Dopamine transporter (DAT) uptake was assessed through semi-quantitative analysis in the most and least affected putamen (maP, laP), and most and least affected caudate (maC, laC). Total putamen-to-caudate ratio and total striatal binding ratio (tSBR) were also quantified. Results: WSC and NoSC had similar demographic and disease-related characteristics. WSC displayed lower uptake values in maC (p = 0.016), maP (p = 0.004), laC (p = 0.019), laP (p = 0.009), and tSBR (p = 0.006). Pearson correlation analysis revealed, in the WSC group, moderate inverse correlations between the log-transformed SD scores and the uptake in maP (r =  - 0.473, p = 0.023), maC (r =  - 0.428, p = 0.042), laP (r = -0.437, p = 0.037), and tSBR (r =  - 0.460, p = 0.027). After controlling in a two-way ANCOVA model for age and sex, between-group differences,between WSC and NoSC remained statistically significant only for dopaminergic denervation in maP [F(1,38) = 7.478, p = 0.009)], laP [F(1,38) = 4.684, p = 0.037)], and tSBR [F(1,38) = 5.069, p = 0.030]. Conclusion: To the best of our knowledge, this is the first study reporting the relationship between the severity of SD and specific patterns of nigrostriatal dopaminergic denervation (especially involving both putamina) in newly diagnosed drug-naïve PD patients.