Echogenicity of the substantia nigra: association with increased iron content and marker for susceptibility to nigrostriatal injury.
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.


METHODS
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.
Berg
Daniela
D
Department of Neurology, University of Würzburg, Josef-Schneider-Str 11, 97080 Würzburg, Germany. daniela.berg@mail.uni-wuerzburg.de
Roggendorf
Wolfgang
W
Schröder
Ute
U
Klein
Rüdiger
R
Tatschner
Thomas
T
Benz
Peter
P
Tucha
Oliver
O
Preier
Michael
M
Lange
Klaus W
KW
Reiners
Karlheinz
K
Gerlach
Manfred
M
Becker
Georg
G
D000293:Adolescent; D000328:Adult; D015415:Biomarkers / Q000032:analysis / Q000737:chemistry; D003342:Corpus Striatum / Q000737:chemistry / Q000378:metabolism* / Q000473:pathology*; D005260:Female; D006801:Humans; D007501:Iron / Q000032:analysis / Q000378:metabolism*; D008297:Male; D011180:Postmortem Changes; D018709:Statistics, Nonparametric; D013378:Substantia Nigra / Q000737:chemistry / Q000378:metabolism* / Q000473:pathology*; D014055:Tomography, Emission-Computed / Q000379:methods / Q000706:statistics & numerical data; D017585:Ultrasonography, Doppler, Transcranial / Q000379:methods / Q000706:statistics & numerical data
D015415:Biomarkers; D007501:Iron