Severity of restless legs syndrome is inversely correlated with echogenicity of the substantia nigra in different neurodegenerative movement disorders. a preliminary observation

Objective: Hyperechogenicity of the substantia nigra is a frequent observation on transcranial sonography in Parkinson's disease and Machado-Joseph disease patients. Additionally, restless legs syndrome is a sleep disorder that is also frequently found in both diseases. Autopsy studies have demonstrated increased SN iron content in hyperechogenic substantia nigra. Iron storage is also known to be involved in restless legs syndrome. We formally compared echogenicity of the substantia nigra with restless legs syndrome in Parkinson's disease and Machado-Joseph disease patients.

Methods: Transcranial brain sonography was performed in a sample of Parkinson's disease and Machado-Joseph disease patients, and findings then correlated with the presence and severity of restless legs syndrome.

Results: There was a continuum of substantia nigra echogenicity among groups (Parkinson's disease versus Machado-Joseph disease versus controls) and sub-groups (Parkinson's disease with and without restless legs syndrome versus Machado-Joseph disease with and without restless legs syndrome) as well as a statistically significant negative correlation between restless legs syndrome severity and substantia nigra echogenicity (p<0.001).

Conclusions: These preliminary observations demonstrate that the severity of RLS may be influenced by nigral iron load reflected by substantia nigra echogenicity in different neurodegenerative movement disorders.