Netzwerkstörungen nach Schlaganfall: Neue Erkenntnisse aus der funktionellen Magnetresonanztomografie

Zusammenfassung

Das sensomotorische System des Menschen besteht aus einem komplexen Netzwerk kortikaler und subkortikaler Areale, deren feines Zusammenspiel den physiologischen Ablauf einer motorischen Aktion ermöglicht. Die Balance in diesem Netzwerk kann durch eine Schlaganfall-Läsion empfindlich gestört werden. Mithilfe von bildgebenden Verfahren wie der Positronen-Emissionstomografie (PET) oder der funktionellen Magnetresonanztomografie (fMRT) können über Konnektivitätsanalysen Störungen der Netzwerkstruktur aufgedeckt werden. Hier zeigen Auswertungen mittels Dynamic Causal Modelling (DCM) ausgedehnte Störungen innerhalb und zwischen den Hemisphären von Schlaganfall-Patienten. Solche Störungen können mit nicht-invasiven Stimulationstechniken korrigiert werden und zu einer Verbesserung der motorischen Performanz der paretischen Hand führen. Aber auch pharmakologische Ansätze können genutzt werden, um die herabgesetzte Netzwerkeffizienz durch die Stimulation beispielsweise noradrenerger Mechanismen zu verbessern und somit motorische Fertigkeiten der paretischen Hand zu steigern. Ein Konnektivitätsansatz bei der Analyse von Bildgebungsdatenerlaubt demzufolge neue Einblicke in die Pathophysiologie von Ischämie-bedingten motorischen Störungen und kann dazu beitragen, hypothesengeleitete neue Ansätze zur Neurorehabilitation zu entwickeln.

Abstract

The sensorimotor system comprises a network of cortical and subcortical areas which interact by means of excitatory or inhibitory circuits finally leading to motor output. The balance within this network may be critically disturbed following stroke if the lesion either directly affects any of these areas or damages white matter fibres connecting critical regions. Such effects can be detected by means of functional neuroimaging techniques like positron emission tomography (PET) or functional magnetic resonance imaging (fMRI) and analyses of connectivity. Estimating effective connectivity by means of dynamic causal modelling (DCM) reveals that, after stroke, changes in both intra- and interhemispheric interactions among cortical regions constitute an important pathophysiological aspect of motor impairment in stroke patients. Such disturbances can be partially corrected by non-invasive brain stimulation approaches. Likewise, stimulating noradrenergic mechanisms may also induce a re-arrangement of the functional network architecture of the sensorimotor system, which might be useful in a rehabilitative setting with stroke patients. In summary, analyses of effective connectivity may further our understanding of the pathophysiology underlying motor symptoms after stroke, and may help to design hypothesis-driven treatment strategies to support recovery of motor function in patients.

Schlüsselwörter

fMRT - Konnektivität - Neuromodulation - TMS - Neuropharmakologie - Enhancement

Key words

fMRI - connectivity - neuromodulation - TMS - neuropharmacology - enhancement

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