Retinal Thickness and Its Interocular Asymmetry Between Parkinson’s Disease and Drug-Induced Parkinsonism

Abstract

Background Drug-induced parkinsonism (DIP) is common, but diagnosis is challenging. Although dopamine transporter imaging is useful, the cost and inconvenience are problematic, and an easily accessible screening technique is needed. We aimed to determine whether optical coherence tomography (OCT) findings could differentiate DIP from Parkinson’s disease (PD). Methods We investigated 97 de novo PD patients and 27 DIP patients using OCT and [ 18 F] N-(3-fluoropropyl)-2b-carbon ethoxy-3b-(4-iodophenyl) nortropane (FP-CIT) positron emission tomography. We compared peripapillary retinal nerve fiber layer thickness (pRNFLT) and macular retinal thickness (mRT) between PD and DIP patients as well as interocular differences in the pRNFLT and the mRT. Asymmetric index (%) for retinal thickness (AIRT) was calculated to measure the interocular differences between pRNFLT and mRT. The correlation between AIRT and total striatal specific/non-specific binding ratio asymmetry index (SNBRAI) was investigated in PD and DIP patients. Results No significant differences in pRNFLT and mRT values were observed between PD and DIP patients (all P values > 0.090). The mean SNBRAI was significantly higher in PD than in DIP ( P = 0.008) patients; however, AIRT did not differ between PD and DIP patients in pRNFLT and mRT (all P values > 0.100). SNBRAI did not correlate with AIRT of pRNFL or mRT in PD and DIP patients (all P values > 0.060). Conclusion Our study showed no benefit of retinal thickness and interocular asymmetry measurements using OCT for distinguishing PD from DIP in the early stages. Additional investigations are needed for confirmation.

Neuroimaging Techniques in Differentiating Parkinson’s Disease from Drug-Induced Parkinsonism: A Comprehensive Review

“…Patients with Parkinson's disease have a decreased average capillary retinal nerve fiber layer in every quadrant [104] They compared the two groups' peripapillary retinal nerve fiber layer and macular retinal thickness. There were no significant differences in peripapillary and macular retinal thickness values [106]. Suh et al's study is important because it showed that, in the early stages of drug-induced parkinsonism, there is no benefit in measuring these optic parameters to differ from early Parkinson's disease.…”