Enlarged hyperechogenic substantia nigra as a risk marker for Parkinson's disease.

Background: SN hyperechogenicity (SN+), determined by transcranial sonography, has been proposed as a risk factor for Parkinson's disease (PD). Recently, we reported a 17.4-fold increased risk for PD in individuals with SN+ older than 50 years within 3 years.

Methods: This is the second follow-up of a prospective, longitudinal, three-center observational study after 5 years. Of the initial 1,847 at baseline PD-free participants 50 years or older, 1,271 underwent the 5-year reassessment.

Results: Within 5 years, 21 individuals developed incident PD. Participants with SN+ at baseline had a more than 20.6 times increased risk to develop PD in this time span than those without this echo feature.

Conclusion: We thus confirm our finding of the 3-year follow-up examination in a longer observation time and higher number of individuals with incident PD and suggest SN+ as an important risk marker for PD.