Echogenicity of the Substantia Nigra: Association With Increased Iron Content and Marker for Susceptibility to Nigrostriatal Injury | Radiology | JAMA Neurology | JAMA Network
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Original Contribution
June 2002

Echogenicity of the Substantia Nigra: Association With Increased Iron Content and Marker for Susceptibility to Nigrostriatal Injury

Author Affiliations

From the Department of Neurology (Drs Berg and Reiners), Division of Neuropathology (Drs Roggendorf and Klein), Institute for Forensic Medicine (Dr Tatschner), and Department of Psychiatry (Dr Gerlach), Bayerische Julius-Maximilians-Universität Würzburg, Würzburg, Germany, the Department of Neurology, University of Homburg, Saar, Germany (Dr Becker and Mrs Schröder), the Department of Neuropsychology, University of Regensburg, Regensburg, Germany (Drs Tucha and Lange and Mr Preier), and PET-Zentrum Mainz, University of Mainz, Mainz, Germany (Dr Benz).

Arch Neurol. 2002;59(6):999-1005. doi:10.1001/archneur.59.6.999

Background  Patients with Parkinson disease characteristically exhibit an increased echogenicity of the substantia nigra (SN) on transcranial sonography, a new neuroimaging technique. The same echo feature of the SN can be identified in 9% of healthy adults.

Objective  To evaluate the relevance of the echogenic SN in healthy adults.

Design  In the first part of the study, 10 healthy subjects younger than 40 years with a distinct SN hyperechogenicity underwent extensive neurological, motor, neuropsychological, and fluorine 18-dopa positron emission tomographic ([18F]-dopa PET) examinations. Results were compared with those of 10 subjects with a low echogenic SN. In the second part of the study, the postmortem brains of 20 patients without extrapyramidal disorders during their lifetime were sonographically examined with a particular focus on SN echogenicity. Subsequently, one half of the brain was prepared for heavy metal analysis, the other for a histological examination.

Results  Healthy subjects with SN hyperechogenicity exhibited a significant reduction of the [18F]-dopa uptake, especially in the putamen (Wilcoxon matched pair test: left side, P = .006; right side, P = .009), whereas their neuropsychological and motor performance were normal. Postmortem studies showed that the echogenicity of the SN correlated with its iron content.

Conclusions  Increased echogenicity of the SN, characteristically seen in Parkinson disease, is related to a functional impairment of the nigrostriatal system (even in young healthy adults) that can be revealed by [18F]-dopa PET studies. Substantia nigra hyperechogenicity is related to a higher tissue iron level, which is known to enhance the cells' generation of reactive oxygen specimens. Therefore, we hypothesize that transcranial sonography may identify a susceptibility marker for the development of nigral injury that can be detected early in life, prior to the onset of Parkinson disease.