Substantia nigra hyperechogenicity (SN+) is a common finding in transcranial ultrasound studies of parkinsonian patients. However, this echofeature is also found in 10% of healthy controls and is here associated with PD risk factors such as male gender and positive family history for PD, as well as with putative premotor symptoms such as hyposmia, depression, sleep disturbances, and subtle neuropsychological and motor impairment. SN+ is hypothesized to indicate an increased risk to develop PD during lifetime. PET studies substantiate this hypothesis, given that SN+ controls showed reduced striatal [(18)Fluoro] Dopa uptake in PET studies. First results of longitudinal follow-up studies show a higher relative risk for future PD in SN+ asymptomatic individuals.
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