Progressive Olfactory Impairment and Cardiac Sympathetic Denervation in REM Sleep Behavior Disorder.

BACKGROUND: Isolated rapid eye movement sleep behavior disorder (iRBD) is prodromal for Parkinson's disease (PD) and dementia with Lewy bodies (DLB). OBJECTIVE: We investigated the use of cardiac [123I]meta-iodo-benzyl-guanidine scintigraphy ([123I]MIBG) and olfactory testing- in comparison to [123I]N-ω-fluoropropyl-2ß-carbomethoxy-3ß-(4-iodophenyl)nortropane single photon emission computed tomography ([123I]FP-CIT-SPECT)- for identifying iRBD patients as prodromal phenotype of PD/DLB. METHODS: 37 RBD subjects underwent cardiac [123I]MIBG and brain [123I]FP-CIT-SPECT at baseline. Olfactory (Sniffin' Sticks), cognitive and motor functions were tested annually for ∼4 years. RESULTS: 29/37 (78.4%) subjects had a pathological [123I]MIBG, of whom 86.2% (25/29) presented at least a moderate hyposmia at baseline (threshold/discrimination/identification-(TDI-)score ≤25). 20/37 (54.1%) subjects had a pathological [123I]FP-CIT-SPECT, always combined with a pathological [123I]MIBG. In subjects with pathological [123I]MIBG, olfactory function worsened (mainly due to threshold and discrimination subscores) from baseline to follow-up (p = 0.005). Olfaction was more impaired in subjects with pathological [123I]MIBG compared to those with normal [123I]MIBG at baseline (p = 0.001) and follow-up (p < 0.001). UPDRS-III scores increased in subjects with both pathological [123I]MIBG and [123I]FP-CIT-SPECT. In this group, seven subjects phenoconverted to PD, all- except for one- presented with at least moderate hyposmia at baseline. CONCLUSION: A combination of the biomarkers "pathological [123I]MIBG" and "hyposmia" likely identifies iRBD patients in an early prodromal stage of PD/DLB, i.e., before nigrostriatal degeneration is visualized. One-third of the subjects with pathological [123I]MIBG had a normal [123I]FP-CIT-SPECT. Noteworthy, in iRBD subjects with pathological [123I]MIBG, olfactory impairment is progressive independent of the [123I]FP-CIT-SPECT status.

Eye tracking identifies biomarkers in α-synucleinopathies versus progressive supranuclear palsy.

OBJECTIVES: This study (1) describes and compares saccade and pupil abnormalities in patients with manifest alpha-synucleinopathies (αSYN: Parkinson's disease (PD), Multiple System Atrophy (MSA)) and a tauopathy (progressive supranuclear palsy (PSP)); (2) determines whether patients with rapid-eye-movement sleep behaviour disorder (RBD), a prodromal stage of αSYN, already have abnormal responses that may indicate a risk for developing PD or MSA. METHODS: Ninety (46 RBD, 27 PD, 17 MSA) patients with an αSYN, 10 PSP patients, and 132 healthy age-matched controls (CTRL) were examined with a 10-min video-based eye-tracking task (Free Viewing). Participants were free to look anywhere on the screen while saccade and pupil behaviours were measured. RESULTS: PD, MSA, and PSP spent more time fixating the centre of the screen than CTRL. All patient groups made fewer macro-saccades (> 2◦ amplitude) with smaller amplitude than CTRL. Saccade frequency was greater in RBD than in other patients. Following clip change, saccades were temporarily suppressed, then rebounded at a slower pace than CTRL in all patient groups. RBD had distinct, although discrete saccade abnormalities that were more marked in PD, MSA, and even more in PSP. The vertical saccade rate was reduced in all patients and decreased most in PSP. Clip changes produced large increases or decreases in screen luminance requiring pupil constriction or dilation, respectively. PSP elicited smaller pupil constriction/dilation responses than CTRL, while MSA elicited the opposite. CONCLUSION: RBD patients already have discrete but less pronounced saccade abnormalities than PD and MSA patients. Vertical gaze palsy and altered pupil control differentiate PSP from αSYN.

Speech Biomarkers in Rapid Eye Movement Sleep Behavior Disorder and Parkinson Disease.

OBJECTIVE: This multilanguage study used simple speech recording and high-end pattern analysis to provide sensitive and reliable noninvasive biomarkers of prodromal versus manifest α-synucleinopathy in patients with idiopathic rapid eye movement sleep behavior disorder (iRBD) and early-stage Parkinson disease (PD). METHODS: We performed a multicenter study across the Czech, English, German, French, and Italian languages at 7 centers in Europe and North America. A total of 448 participants (337 males), including 150 with iRBD (mean duration of iRBD across language groups 0.5-3.4 years), 149 with PD (mean duration of disease across language groups 1.7-2.5 years), and 149 healthy controls were recorded; 350 of the participants completed the 12-month follow-up. We developed a fully automated acoustic quantitative assessment approach for the 7 distinctive patterns of hypokinetic dysarthria. RESULTS: No differences in language that impacted clinical parkinsonian phenotypes were found. Compared with the controls, we found significant abnormalities of an overall acoustic speech severity measure via composite dysarthria index for both iRBD (p = 0.002) and PD (p < 0.001). However, only PD (p < 0.001) was perceptually distinct in a blinded subjective analysis. We found significant group differences between PD and controls for monopitch (p < 0.001), prolonged pauses (p < 0.001), and imprecise consonants (p = 0.03); only monopitch was able to differentiate iRBD patients from controls (p = 0.004). At the 12-month follow-up, a slight progression of overall acoustic speech impairment was noted for the iRBD (p = 0.04) and PD (p = 0.03) groups. INTERPRETATION: Automated speech analysis might provide a useful additional biomarker of parkinsonism for the assessment of disease progression and therapeutic interventions. ANN NEUROL 2021;90:62-75.