Impaired Inhibitory Control of Saccadic Eye Movements in Cervical Dystonia: An Eye-Tracking Study.

BACKGROUND: The pathophysiology of cervical dystonia is still unclear. Recent evidence points toward a network disorder affecting several brain areas. The objective of this study was to assess the saccadic inhibition as a marker of corticostriatal function in cervical dystonia. METHODS: We recruited 31 cervical dystonia patients and 17 matched healthy controls. Subjects performed an overlap prosaccade, an antisaccade, and a countermanding task on an eye tracker to assess automatic visual response and response inhibition. RESULTS: Cervical dystonia patients made more premature saccades (P = 0.041) in the overlap prosaccade task and more directional errors in the antisaccade task (P = 0.011) and had a higher rate of failed inhibition in the countermanding task (P = 0.001). CONCLUSIONS: The results suggest altered saccadic inhibition in cervical dystonia, possibly as a consequence of dysfunctional corticostriatal networks. Further studies are warranted to confirm whether these abnormalities are affected by the available therapies and whether this type of impairment is found in other focal dystonias. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Extending the Spectrum of Nonmotor Symptoms with Olfaction in Premotor Huntington's Disease: A Pilot Study.

OBJECTIVE: The aim of this pilot study was to investigate change of olfactory functions in Huntington's disease (HD). BACKGROUND: HD is a neurodegenerative disease characterized by motor, cognitive, and behavioral abnormalities. There are several studies reporting olfactory dysfunction in manifest and some studies in premanifest HD carriers, and a recent neuropathological study demonstrated HD-specific protein aggregation in the anterior olfactory nucleus in HD patients. In this study, we wanted to assess olfactory functions as a possible early nonmotor symptom of HD mutation carriers without disease-specific motor symptoms and HD patients. METHODS: All participants had genetic confirmed HD and were prospectively recruited during their routine control in a specialized outpatient clinic of the Medical University of Innsbruck, Department of Neurology, Austria. Healthy controls (HCs) were caregivers from patients. They were only included if they were younger than 70 years, scored more than 24/30 points on the Mini Mental State Examination, and had no other disease compromising olfactory function. Furthermore, all participants were tested on the Sniffin' sticks 16-items identification test. RESULTS: We included 23 patients with manifest HD, 13 HD mutation carriers, and 19 HCs. Mutation carriers showed significant impaired odor identification compared to HCs (p < 0.001), as well as Huntington's patients compared with both mutation carriers (p = 0.003) and HCs (p < 0.001). CONCLUSIONS: The results of this pilot study suggest that olfactory dysfunction may be an early nonmotor symptom of HD and could be a potential marker to assess disease progression.

A mutation in VPS35, encoding a subunit of the retromer complex, causes late-onset Parkinson disease.

To identify rare causal variants in late-onset Parkinson disease (PD), we investigated an Austrian family with 16 affected individuals by exome sequencing. We found a missense mutation, c.1858G>A (p.Asp620Asn), in the VPS35 gene in all seven affected family members who are alive. By screening additional PD cases, we saw the same variant cosegregating with the disease in an autosomal-dominant mode with high but incomplete penetrance in two further families with five and ten affected members, respectively. The mean age of onset in the affected individuals was 53 years. Genotyping showed that the shared haplotype extends across 65 kilobases around VPS35. Screening the entire VPS35 coding sequence in an additional 860 cases and 1014 controls revealed six further nonsynonymous missense variants. Three were only present in cases, two were only present in controls, and one was present in cases and controls. The familial mutation p.Asp620Asn and a further variant, c.1570C>T (p.Arg524Trp), detected in a sporadic PD case were predicted to be damaging by sequence-based and molecular-dynamics analyses. VPS35 is a component of the retromer complex and mediates retrograde transport between endosomes and the trans-Golgi network, and it has recently been found to be involved in Alzheimer disease.

VPS35 Parkinson's disease phenotype resembles the sporadic disease.

Recently a new autosomal dominant Parkinson's disease mutation (p.Asp620Asn) in the VPS35 gene was discovered. The clinical features of 14 PD patients with this mutation from three Austrian families were evaluated. Age at disease-onset appears lower and depression was more common in Austrian patients compared to sporadic PD patients. However, we were unable to identify a specific clinical maker of VPS35 patients, who otherwise resemble sporadic PD patients.

Correlation of dopaminergic terminal dysfunction and microstructural abnormalities of the basal ganglia and the olfactory tract in Parkinson's disease.

Signal abnormalities of the substantia nigra and the olfactory tract detected either by diffusion tensor imaging, including measurements of mean diffusivity, a parameter of brain tissue integrity, and fractional anisotropy, a parameter of neuronal fibre integrity, or transcranial sonography, were recently reported in the early stages of Parkinson's disease. In this study, changes in the nigral and olfactory diffusion tensor signal, as well as nigral echogenicity, were correlated with clinical scales of motor disability, odour function and putaminal dopamine storage capacity measured with 6-[(18)F] fluorolevodopa positron emission tomography in early and advanced stages of Parkinson's disease. Diffusion tensor imaging, transcranial sonography and positron emission tomography were performed on 16 patients with Parkinson's disease (mean disease duration 3.7 ± 3.7 years, Hoehn and Yahr stage 1 to 4) and 14 age-matched healthy control subjects. Odour function was measured by the standardized Sniffin' Sticks Test. Mean putaminal 6-[(18)F] fluorolevodopa influx constant, mean nigral echogenicity, mean diffusivity and fractional anisotropy values of the substantia nigra and the olfactory tract were identified by region of interest analysis. When compared with the healthy control group, the Parkinson's disease group showed significant signal changes in the caudate and putamen by 6-[(18)F] fluorolevodopa positron emission tomography, in the substantia nigra by transcranial sonography, mean diffusivity and fractional anisotropy (P < 0.001, P < 0.01, P < 0.05, respectively) and in the olfactory tract by mean diffusivity (P < 0.05). Regional mean diffusivity values of the substantia nigra and the olfactory tract correlated significantly with putaminal 6-[(18)F] fluorolevodopa uptake (r = -0.52, P < 0.05 and r = -0.71, P < 0.01). Significant correlations were also found between nigral mean diffusivity values and the Unified Parkinson's Disease Rating Scale motor score (r = -0.48, P < 0.01) and between mean putaminal 6-[(18)F] fluorolevodopa uptake and the total odour score (r = 0.58; P < 0.05) as well as the Unified Parkinson's Disease Rating Scale motor score (r = -0.53, P < 0.05). This study reports a significant association between increased mean diffusivity signal and decreased 6-[(18)F] fluorolevodopa uptake, indicating that microstructural degradation of the substantia nigra and the olfactory tract parallels progression of putaminal dopaminergic dysfunction in Parkinson's disease. Since increases in nigral mean diffusivity signal also correlated with motor dysfunction, diffusion tensor imaging may serve as a surrogate marker for disease progression in future studies of putative disease modifying therapies.

Effects of Nabilone on Sleep Outcomes in Patients with Parkinson's Disease: A Post-hoc Analysis of NMS-Nab Study.

Background: The synthetic tetrahydrocannabinol analogue nabilone improved overall non-motor symptom (NMS) burden in Parkinson's disease (PD) patients in comparison to placebo. Objectives: To characterize the effects of nabilone on different sleep outcomes in PD patients. Methods: We performed a post-hoc analysis of the controlled, double-blind, enriched enrollment randomized withdrawal NMS-Nab study to assess the effects of nabilone on sleep outcomes in study participants who reported clinically-relevant sleep problems (MDS-UPDRS-1.7 ≥ 2 points). Results: After open-label nabilone administration, 77.4% reported no relevant sleep problem. In the withdrawal phase of the trial, the MDS-UPDRS-1.7. and the NMS-Scale Domain 2 (i.e., Sleep/Fatigue) significantly worsened only in PD patients in the placebo group, which was mostly driven by a significant worsening of insomnia (question 5 of the NMS-Scale Domain 2). Conclusions: This post-hoc analysis of the NMS-Nab trial suggests that nabilone has beneficial effects on sleep outcomes in PD patients experiencing sleep problems at baseline.The original trial was registered with ClinicalTrials.gov (NCT03769896, https://clinicaltrials.gov/ct2/show/NCT03769896) and EudraCT (2017-000192-86).