Relationship of substantia nigra echogenicity and motor function in elderly subjects

Background: Patients with Parkinson's disease (PD) exhibit an increased ech ogenicity of the substantia nigra (SN) on transcranial sonography. Some hea lthy adults with the same echo characteristics showed a reduced (18)fluorod opa uptake on PET, indicating a subclinical alteration of the nigrostriatal system. Objectives: To determine whether the sonographic phenotype of hype rechogenic SN has any relevance for motor function in elderly subjects and whether an increased echogenicity of the SN is associated with an impaired motor function. Method: In a population-based, cross-sectional study, 93 su bjects older then 60 years without history of extrapyramidal disorder under went sonographic and neurologic examinations, with a quantitative motor ass essment. Results: Elderly healthy subjects without prediagnosed extrapyrami dal disorder but with SN hyperechogenicity had more frequent and more sever e parkinsonian symptoms and a slower finger tapping than those with a regul ar echogenicity of the SN (p < 0.05, U test). Conclusion: With increasing a ge, subjects with SN hyperechogenicity develop a more substantial slowing o f movements than subjects without this echo pattern, stressing the function al relevance of this sonographic finding. The authors speculate that hypere chogenicity of the SN may be detected by transcranial sonography early in l ife and may serve as a risk marker for nigral injury, although only a minor ity of these subjects will develop the full clinical picture of PD.