Connecting the Dots: Exploring the Relationship between Optical Coherence Tomography and ^99mTc-TRODAT-1 SPECT...

While optical coherence tomography (OCT) is explored as a potential biomarker in Parkinson's disease (PD), technetium-99m-labeled tropane derivative (^99mTc-TRODAT-1) single-photon emission computed tomography (SPECT) imaging has a proven role in diagnosing PD. Our objective was to compare the OCT parameters in PD patients and healthy controls (HCs) and correlate them with ^99mTc-TRODAT-1 parameters in PD patients.

This cross-sectional study included 30 PD patients and 30 age- and gender-matched HCs. Demographic data, PD details including Movement Disorders Society Unified Parkinson's Disease Rating Scale-III (MDS-UPDRS-III) and Hoehn-Yahr (HY) staging, and OCT parameters including macular and peripapillary retinal nerve fiber layer (RNFL) thickness in bilateral eyes were recorded. PD patients underwent ^99mTc-TRODAT-1 SPECT imaging. The terms "ipsilateral" and "contralateral" were used with reference to more severely affected body side in PD patients and compared with corresponding sides in HCs.

PD patients showed significant ipsilateral superior parafoveal quadrant (mean ± standard deviation [SD] = 311.10 ± 15.90 vs. 297.57 ± 26.55, P = 0.02) and contralateral average perifoveal (mean ± SD = 278.75 ± 18.97 vs. 269.08 ± 16.91, P = 0.04) thinning compared to HCs. Peripapillary RNFL parameters were comparable between PD patients and HCs. MDS-UPDRS-III score and HY stage were inversely correlated to both ipsilateral (Spearman rho = -0.52, P = 0.003; Spearman rho = -0.47, P = 0.008) and contralateral (Spearman rho = -0.53, P = 0.002; Spearman rho = -0.58, P < 0.001) macular volumes, respectively. PD duration was inversely correlated with ipsilateral temporal parafoveal thickness (ρ = -0.41, P = 0.02). No correlation was observed between OCT and ^99mTc-TRODAT-1 SPECT parameters in PD patients.

Compared to HCs, a significant thinning was observed in the ipsilateral superior parafoveal quadrant and the contralateral average perifoveal region in PD patients. Macular volume and ipsilateral temporal parafoveal thickness were inversely correlated with disease severity and duration, respectively. OCT and ^99mTc-TRODAT-1 SPECT parameters failed to correlate in PD patients.