Substantia nigra hyperechogenicity is a risk marker of Parkinson's disease: no

Abstract

During the past two decades, transcranial sonography (TCS) has developed to an increasingly used brain imaging method that visualizes characteristic patterns of basal ganglia alterations in distinct movement disorders. Since the discovery of a characteristic abnormal hyperechogenic appearance of substantia nigra (SN) on TCS in Parkinson's disease (PD), which is stable during the course of the disease and probably present already in preclinical disease stages, the results of several studies have promoted the idea that this TCS finding in healthy subjects might be a risk marker of PD. The present view summarizes current scientific evidence favouring the idea that the TCS finding of SN hyperechogenicity alone may not be a (strong) risk marker of PD. Especially, it is discussed how reliable this TCS finding is, whether this TCS finding can be regarded as a progression marker or a risk marker of PD, how strongly it may indicate a risk of PD, what else if not an increased risk of PD could be indicated, and which role TCS of SN may finally play in the detection of subjects at risk of PD.