The prodromal stage of synucleinopathies in idiopathic rapid eye movement sleep behavior disorder (iRBD). Patients with synucleinopathies usually have aberrant eye movements. However, it was uncertain if people with iRBD exhibited aberrant eye movements. For a study, researchers sought to determine eye movement abnormalities and associated gray matter changes in iRBD to see whether they might be used as biomarkers for phenoconversion to synucleinopathies. A 15-minute ocular-tracking test was performed on 40 patients with iRBD who were in the early stages of disease development and 35 healthy control volunteers. They were also evaluated clinically for olfactory function, nonmotor symptoms, and autonomic symptoms, which are all indicators for predicting phenoconversion to synucleinopathies in iRBD. In addition, a subset of the individuals (20 iRBD patients and 20 healthy control subjects) also underwent structural magnetic resonance imaging.

In two areas, patients with iRBD’s ocular-tracking skills were poorer than healthy control subjects: pursuit initiation and steady-state tracking. Cortical thinning in the right visual region V4 is associated with poor pursuit in patients with iRBD. Furthermore, in individuals with iRBD, protracted pursuit start has a pattern of connection with olfactory loss, the first biomarker that occurs before other prodromal indicators. They discovered previously unreported ocular-tracking anomalies in individuals with iRBD early in their illness development. The anomalies and atrophy of brain regions involved in object motion perception may imply phenoconversion to synucleinopathies in iRBD.