Comparative Study of the Substantia Nigra Echogenicity and 123i-Ioflupane Spect In Patients With Synucleinopathies With And Without Rem Sleep Behavior Disorder

Abstract Objectives Hyperechogenicity of the substantia nigra (SN) and abnormal dopamine transporter-single-photon emission computed tomography (DAT-SPECT) are biomarkers commonly used in the assessment of prodromal synucleinopathy. Our goal was: 1) to compare echogenicity of SN in idiopathic REM behavior disorder (iRBD), PD without RBD (PD-noRBD), PD with RBD (PD+RBD), and control subjects, and 2) to examine association between SN degeneration assessed by DAT-SPECT and SN echogenicity. Patients/Methods Sixty-one subjects with confirmed iRBD were examined using Movement Disorders Society-unified PD rating scale (MDS-UPDRS), TCS (transcranial sonography) and DAT-SPECT. The results were compared with 44 patients with PD (25% PD+RBD) and with 120 age-matched healthy subjects. Results and conclusion The abnormal SN area was found in 75.5% PD, 23% iRBD and 7.3% controls. Median SN echogenicity area in PD (0.27 ± 0.22 cm2) was higher compared to iRBD (0.07 ± 0.07 cm2; p Abnormal DAT-SPECT was found in 16 iRBD (25.4%) and 44 PD subjects (100%). No correlation between the larger SN area and corresponding putaminal binding index was found in iRBD (r=-0.13, p=0.29), nor in PD (r=-0.19, p=0.22). The results of our study showed that: 1) SN echogenicity area in iRBD was higher compared to controls, but the hyperechogenicity was present only in a minority of iRBD; 2) SN echogenicity and DAT-SPECT binding index did not correlate in either group; and 3) SN echogenicity does not differ between PD with/without RBD.