Enlarged Substantia Nigra Hyperechogenicity and Risk for Parkinson Disease: A 37-Month 3-Center Study of 1847 Older Persons

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.