Die Hirnparenchym-Sonographie ist ein nicht invasives bildgebendes Verfahren, das aufgrund seines eigenständigen physikalischen Prinzips die Ergebnisse konventioneller bildgebender Untersuchungen des Gehirns erweitert. Bei Patienten mit idiopathischer Parkinson-Krankheit (IPK) oder hereditärem Parkinsonismus infolge Parkin-Mutation findet sich eine charakteristische Vergrößerung des Schallechos (Hyperechogenität) der Substantia nigra (SN), die bereits in präsymptomatischen Stadien nachweisbar ist und künftig als präklinischer Risikomarker genutzt werden könnte. Als Ursache der SN-Hyperechogenität werden erhöhte Konzentrationen von Eisen angenommen, das nicht an Ferritin, sondern an alternative Proteine gebunden ist. Bei Patienten mit Multisystematrophie (MSA) und progressiver supranuklärer Blickparese (PSP) liegt typischerweise eine normale SN-Echogenität vor, während Patienten mit kortikobasaler Degeneration (CBD) und Demenz bei diffuser Lewy-Körperchen-Krankheit (DLB) ebenfalls eine SN-Hyperechogenität aufweisen. Die klinisch oft schwierige Differenzierung zwischen IPK und MSA/PSP bzw. zwischen PSP und CBD wird über die Messung der SN-Echogenität bereits im Frühstadium erleichtert. Weitere sonographische Befunde können zur Syndromdiskrimination beitragen. Eine abnorme Hyperechogenität des Nucleus lentiformis ist nur bei einem Drittel der IPK- und DLB-Patienten nachweisbar, jedoch bei etwa 80 % der MSA-, PSP- und CBD-Patienten. Für die PSP ist eine Dilatation des dritten Ventrikels über 10 mm charakteristisch. Die Hirnparenchym-Sonographie stellt ein neues Werkzeug zur Früh- und Differenzialdiagnostik von Parkinson-Syndromen dar.
Abstract
Brain parenchyma sonography is a non-invasive imaging technique extending the results of conventional imaging methods because of its different physical principle. In patients with idiopathic Parkinson's disease (IPD) or with parkinsonism due to parkin mutation a highly characteristic enlargement of the ultrasound signal (hyperechogenicity) of the substantia nigra (SN) can be detected that is already present in presymptomatic stages and could be used in future as a preclinical risk marker. SN hyperechogenicity is thought to be caused by increased amounts of iron bound to proteins other than ferritin. In patients with multiple-system atrophy (MSA) and progressive supranuclear palsy (PSP) typically a normoechogenic SN is found, whereas patients with corticobasal degeneration (CBD) and dementia with diffuse Lewy bodies (DLB) also exhibit SN hyperechogenicity. Clinical differentiation of IPD vs. MSA/PSP and of PSP vs. CBD, which is often difficult, is supported already in early stages by measurement of SN echogenicity. Further sonographic findings may improve syndrome discrimination. Abnormal lenticular-nucleus hyperechogenicity is present only in one-third of IPD and DLB patients, but in about 80 % of MSA, PSP and CBD patients. Third-ventricle dilatation exceeding 10 mm is characteristic for PSP. Brain parenchyma sonography represents a new tool for early diagnosis and discrimination of parkinsonian disorders.
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