Objective: To evaluate whether enlarged substantia nigra hyperechogenicity (SN+) is associated with an increased risk for Parkinson disease (PD) in a healthy elderly population.
Design: Longitudinal 3-center observational study with 37 months of prospective follow-up.
Setting: Individuals 50 years or older without evidence of PD or any other neurodegenerative disease.
Participants: Of 1847 participants who underwent a full medical history, neurological assessment, and transcranial sonography at baseline, 1535 could undergo reassessment.
Main outcome measure: Incidence of new-onset PD in relation to baseline transcranial sonography status.
Results: There were 11 cases of incident PD during the follow-up period. In participants with SN+ at baseline, the relative risk for incident PD was 17.37 (95% confidence interval, 3.71-81.34) times higher compared with normoechogenic participants.
Conclusions: In this prospective study, we demonstrate for the first time a highly increased risk for PD in elderly individuals with SN+. Transcranial sonography of the midbrain may therefore be a promising primary screening procedure to define a risk population for imminent PD.