Comparison of Transcranial Sonography and [

BACKGROUND: Mutations in GBA1 are a common genetic risk factor for parkinsonism; however, penetrance is incomplete, and biomarkers of future progression to parkinsonism are needed. Both nigral sonography and striatal [(18)F]-FDOPA PET assay dopamine system health, but their utility and coherence in this context are unclear. OBJECTIVES: To evaluate the utility and coherence of these modalities in GBA1-associated parkinsonism. METHODS: Thirty-four patients with GBA1 mutations (seven with parkinsonism), underwent both transcranial studies for substantia nigra echogenicity and [(18)F]-FDOPA PET to determine striatal tracer specific uptake (K(i)). RESULTS: Larger nigral echogenic areas and reduced striatal K(i) were exclusively seen in parkinsonian subjects. Sonographic and PET measurements showed strong inverse correlations, but solely in individuals with clinical parkinsonism. CONCLUSIONS: Close correspondence between nigral echogenicity and striatal presynaptic dopamine synthesis capacity seen only in GBA1 carriers with parkinsonism provides validation that these two modalities may conjointly capture aspects of the biology underlying clinical parkinsonism but raises questions about their utility as predictive tools in at-risk subjects.