Early-phase amyloid PET reproduces metabolic signatures of cognitive decline in Parkinson's disease.

INTRODUCTION: Recent work suggests that amyloid beta (Aß) positron emission tomography (PET) tracer uptake shortly after injection ("early phase") reflects brain metabolism and perfusion. We assessed this modality in a predominantly amyloid-negative neurodegenerative condition, Parkinson's disease (PD), and hypothesized that early-phase 18F-florbetaben (eFBB) uptake would reproduce characteristic hypometabolism and hypoperfusion patterns associated with cognitive decline in PD. METHODS: One hundred fifteen PD patients across the spectrum of cognitive impairment underwent dual-phase Aß PET, structural and arterial spin labeling (ASL) magnetic resonance imaging (MRI), and neuropsychological assessments. Multiple linear regression models compared eFBB uptake to cognitive performance and ASL MRI perfusion. RESULTS: Reduced eFBB uptake was associated with cognitive performance in brain regions previously linked to hypometabolism-associated cognitive decline in PD, independent of amyloid status. Furthermore, eFBB uptake correlated with cerebral perfusion across widespread regions. DISCUSSION: EFBB uptake is a potential surrogate measure for cerebral perfusion/metabolism. A dual-phase PET imaging approach may serve as a clinical tool for assessing cognitive impairment. Highlights: Images taken at amyloid beta (Aß) positron emission tomography tracer injection may reflect brain perfusion and metabolism.Parkinson's disease (PD) is a predominantly amyloid-negative condition.Early-phase florbetaben (eFBB) in PD was associated with cognitive performance.eFBB uptake reflects hypometabolism-related cognitive decline in PD.eFBB correlated with arterial spin labeling magnetic resonance imaging measured cerebral perfusion.eFBB distinguished dementia from normal cognition and mild cognitive impairment.Findings were independent of late-phase Aß burden.Thus, eFBB may serve as a surrogate measure for brain metabolism/perfusion.

Progressive MRI brain volume changes in ovine models of CLN5 and CLN6 neuronal ceroid lipofuscinosis.

Neuronal ceroid lipofuscinoses (Batten disease) are a group of inherited lysosomal storage disorders characterized by progressive neurodegeneration leading to motor and cognitive dysfunction, seizure activity and blindness. The disease can be caused by mutations in 1 of 13 ceroid lipofuscinosis neuronal (CLN) genes. Naturally occurring sheep models of the CLN5 and CLN6 neuronal ceroid lipofuscinoses recapitulate the clinical disease progression and post-mortem pathology of the human disease. We used longitudinal MRI to assess global and regional brain volume changes in CLN5 and CLN6 affected sheep compared to age-matched controls over 18 months. In both models, grey matter volume progressively decreased over time, while cerebrospinal fluid volume increased in affected sheep compared with controls. Total grey matter volume showed a strong positive correlation with clinical scores, while cerebrospinal fluid volume was negatively correlated with clinical scores. Cortical regions in affected animals showed significant atrophy at baseline (5 months of age) and progressively declined over the disease course. Subcortical regions were relatively spared with the exception of the caudate nucleus in CLN5 affected animals that degenerated rapidly at end-stage disease. Our results, which indicate selective vulnerability and provide a timeline of degeneration of specific brain regions in two sheep models of neuronal ceroid lipofuscinoses, will provide a clinically relevant benchmark for assessing therapeutic efficacy in subsequent trials of gene therapy for CLN5 and CLN6 disease.

Higher perceived stress and exacerbated motor symptoms in Parkinson's disease during the COVID-19 lockdown in New Zealand.

AIMS: Stress plays a key role in Parkinson's disease (PD) by acting on the dopaminergic system and worsening patients' motor function. The impact of New Zealand's strict lockdown measures to contain COVID-19 on perceived stress and PD motor symptoms remains unknown. Here we examined the relationship between perceived levels of stress, changes in physical activity levels and PD motor symptoms during lockdown. METHODS: During lockdown, 134 participants with PD and 49 controls completed a survey assessing perceived stress, self-reported changes in PD motor symptoms and physical activity duration and intensity prior to and during lockdown. RESULTS: Perceived stress was higher in PD than controls, and in those reporting a worsening of tremor, balance/gait, dyskinesia and bradykinesia compared to those indicating no change during the COVID-19 lockdown. These effects were not modulated by physical activity. CONCLUSIONS: Reducing stressors may be an important adjunct treatment strategy to improve motor function in PD.

Neuropsychiatric Symptoms Are Associated with Dementia in Parkinson's Disease but Not Predictive of it.

BACKGROUND: Neuropsychiatric symptoms in Parkinson's disease (PD) may increase dementia (PDD) risk. The predictive value of these symptoms, however, has not been compared to clinical and demographic predictors of future PDD. OBJECTIVES: Determine if neuropsychiatric symptoms are useful markers of PDD risk. METHODS: 328 PD participants completed baseline neuropsychiatric and MDS-Task Force-Level II assessments. Of these, 202 non-demented individuals were followed-up over a four-years period to detect conversion to PDD; 51 developed PDD. ROC analysis tested associations between baseline neuropsychiatric symptoms and future PDD. The probability of developing PDD was also modeled as a function of neuropsychiatric inventory (NPI)-total score, PD Questionnaire (PDQ)-hallucinations, PDQ-anxiety, and contrasted to cognitive ability, age, and motor function. Leave-one-out information criterion was used to evaluate which models provided useful information when predicting future PDD. RESULTS: The PDD group experienced greater levels of neuropsychiatric symptoms compared to the non-PDD groups at baseline. Few differences were found between the PD-MCI and PD-N groups. Six neuropsychiatric measures were significantly, but weakly, associated with future PDD. The strongest was NPI-total score: AUC = 0.66 [0.57-0.75]. There was, however, no evidence it contained useful out-of-sample predictive information of future PDD (delta ELPD = 1.8 (SD 2.5)); Similar results held for PDQ-hallucinations and PDQ-anxiety. In contrast, cognitive ability (delta ELPD = 36 (SD 8)) and age (delta ELPD = 11 (SD 5)) provided useful predictive information of future PDD. CONCLUSIONS: Cognitive ability and age strongly out-performed neuropsychiatric measures as markers of developing PDD within 4 years. Therefore, neuropsychiatric symptoms do not appear to be useful markers of PDD risk.

Childbirth and Delayed Parkinson's Onset: A Reproducible Nonbiological Artifact of Societal Change.

BACKGROUND: Uncontrolled studies have reported associations between later Parkinson's disease onset in women and a history of giving birth, with age at onset delayed by nearly 3 years per child. We tested this association in two independent data sets, but, as a control to test for nonbiological explanations, also included men with PD. METHODS: We analyzed valid cases from the Parkinson's Progressive Markers Initiative incident sample (145 women, 276 men) and a prevalent sample surveyed by the New Zealand Brain Research Institute (210 women, 394 men). RESULTS: The association was present in both women and men in the Parkinson's Progressive Markers Initiative study, and absent in both in the New Zealand Brain Research Institute study. This is consistent with generational differences common to men and women, which confound with age at onset in incident-dominant samples. CONCLUSIONS: Despite being replicable in certain circumstances, associations between childbirth and later PD onset are an artifact of generational cohort differences. © 2020 International Parkinson and Movement Disorder Society.

Test-retest reliability and sample size estimates after MRI scanner relocation.

OBJECTIVE: Many factors can contribute to the reliability and robustness of MRI-derived metrics. In this study, we assessed the reliability and reproducibility of three MRI modalities after an MRI scanner was relocated to a new hospital facility. METHODS: Twenty healthy volunteers (12 females, mean age (standard deviation) â€‹= â€‹41 (11) years, age range [25-66]) completed three MRI sessions. The first session (S1) was one week prior to the 3T GE HDxt scanner relocation. The second (S2) occurred nine weeks after S1 and at the new location; a third session (S3) was acquired 4 weeks after S2. At each session, we acquired structural T1-weighted, pseudo-continuous arterial spin labelled, and diffusion tensor imaging sequences. We used longitudinal processing streams to create 12 summary MRI metrics, including total gray matter (GM), cortical GM, subcortical GM, white matter (WM), and lateral ventricle volume; mean cortical thickness; total surface area; average gray matter perfusion, and average diffusion tensor metrics along principal white matter pathways. We compared mean MRI values and variance at the old scanner location to multiple sessions at the new location using Bayesian multi-level regression models. K-fold cross validation allowed identification of important predictors. Whole-brain analyses were used to investigate any regional differences. Furthermore, we calculated within-subject coefficient of variation (wsCV), intraclass correlation coefficient (ICC), and dice similarity index (SI) of cortical segmentations across scanner relocation and within-site. Additionally, we estimated sample sizes required to robustly detect a 4% difference between two groups across MRI metrics. RESULTS: All global MRI metrics exhibited little mean difference and small variability (bar cortical gray matter perfusion) both across scanner relocation and within-site repeat. T1- and DTI-derived tissue metrics showed â€‹< â€‹|0.3|% mean difference and <1.2% variance across scanner location and <|0.4|% mean difference and <0.8% variance within the new location, with between-site intraclass correlation coefficient (ICC) â€‹> â€‹0.80 and within-subject coefficient of variation (wsCV) â€‹< â€‹1.4%. Mean cortical gray matter perfusion had the highest between-session variability (6.7% [0.3, 16.7], estimate [95% uncertainty interval]), and hence the smallest ICC (0.71 [0.44,0.92]) and largest wsCV (13.4% [5.4, 18.1]). No global metric exhibited evidence of a meaningful mean difference between scanner locations. However, surface area showed evidence of a mean difference within-site repeat (between S2 and S3). Whole-brain analyses revealed no significant areas of difference between scanner relocation or within-site. For all metrics, we found no support for a systematic difference in variance across relocation sites compared to within-site test-retest reliability. Necessary sample sizes to detect a 4% difference between two independent groups varied from a maximum of n â€‹= â€‹362 per group (cortical gray matter perfusion), to total gray matter volume (n â€‹= â€‹114), average fractional anisotropy (n â€‹= â€‹23), total gray matter volume normalized by intracranial volume (n â€‹= â€‹19), and axial diffusivity (n â€‹= â€‹3 per group). CONCLUSION: Cortical gray matter perfusion was the most variable metric investigated (necessitating large sample sizes to identify group differences), with other metrics showing substantially less variability. Scanner relocation appeared to have a negligible effect on variability of the global MRI metrics tested. This manuscript reports within-site test-retest variability to act as a tool for calculating sample size in future investigations. Our results suggest that when all other parameters are held constant (e.g., sequence parameters and MRI processing), the effect of scanner relocation is indistinguishable from within-site variability, but may need to be considered depending on the question being investigated.

Volitional Suppression of Parkinsonian Resting Tremor.

BACKGROUND: We have observed in the clinic that a number of patients with Parkinson's disease (PD) can suppress their tremor at will for brief periods, by conscious mental processes. To our knowledge, the ability to consciously diminish one's resting tremor has not yet been reported nor assessed quantitatively. OBJECTIVE: To provide the first detailed systematic investigation of the phenomenon of voluntary tremor suppression in PD. METHODS: We examined changes in tremor characteristics during voluntary tremor suppression in 37 PD patients (on medication) presenting with rest tremor in their upper limb. We measured tremor oscillations with a triaxis accelerometer on the index finger of the most-affected hand (n = 27). With surface electromyography (EMG), we measured changes in neuromuscular activity of the forearm flexor digitorum superficialis and extensor digitorum muscles (n = 15). Participants completed four 1-minute trials, consisting of alternating consecutive 30-second periods of resting tremor and 30-second periods of attempted tremor suppression. RESULTS: Bayesian multilevel modeling revealed that attempted voluntary tremor suppression did indeed reduce tremor amplitude (peak power) of the acceleration signal and increased tremor frequency of the acceleration and EMG signals. Relative EMG power in the 3- to 8-Hz tremor band was also smaller. Tremor suppression was not by enhanced voluntary contraction of the relevant muscle pairs. CONCLUSIONS: We present novel empirical evidence that PD resting tremor can be suppressed by an act of will, as evidenced by significant modulation of key neurophysiological tremor characteristics. These data highlight that it is possible to exert significant conscious control over parkinsonian resting tremor.

Beta Amyloid Deposition Is Not Associated With Cognitive Impairment in Parkinson's Disease.

The extent to which Alzheimer neuropathology, particularly the accumulation of misfolded beta-amyloid, contributes to cognitive decline and dementia in Parkinson's disease (PD) is unresolved. Here, we used Florbetaben PET imaging to test for any association between cerebral amyloid deposition and cognitive impairment in PD, in a sample enriched for cases with mild cognitive impairment. This cross-sectional study used Movement Disorders Society level II criteria to classify 115 participants with PD as having normal cognition (PDN, n = 23), mild cognitive impairment (PD-MCI, n = 76), or dementia (PDD, n = 16). We acquired 18F-Florbetaben (FBB) amyloid PET and structural MRI. Amyloid deposition was assessed between the three cognitive groups, and also across the whole sample using continuous measures of both global cognitive status and average performance in memory domain tests. Outcomes were cortical FBB uptake, expressed in centiloids and as standardized uptake value ratios (SUVR) using the Centiloid Project whole cerebellum region as a reference, and regional SUVR measurements. FBB binding was higher in PDD, but this difference did not survive adjustment for the older age of the PDD group. We established a suitable centiloid cut-off for amyloid positivity in Parkinson's disease (31.3), but there was no association of FBB binding with global cognitive or memory scores. The failure to find an association between PET amyloid deposition and cognitive impairment in a moderately large sample, particularly given that it was enriched with PD-MCI patients at risk of dementia, suggests that amyloid pathology is not the primary driver of cognitive impairment and dementia in most patients with PD.

Parkinson's disease across ethnicities: A nationwide study in New Zealand.

BACKGROUND: New Zealand is an ethnically diverse country with a unified national prescribing system. This provides a good framework to use drug-tracing methodology to establish the prevalence and incidence of Parkinson's disease across different ethnic groups. The objective of this study was to determine the prevalence and incidence of Parkinson's disease in the major ethnic groups in New Zealand. METHODS: Information on Parkinson's disease-related medications was extracted from the national Pharmaceutical Collection of community-dispensed medications for the period January 1, 2005, to December 31, 2014. Diagnoses for a large subset of individuals were independently determined through national mortality and hospital admissions data sets. We used a Bayesian model, accommodating uncertainty and bias, to estimate the number of people with Parkinson's disease. RESULTS: We found the highest rate of Parkinson's disease in the European ethnic group and the lowest rate in the indigenous Maori. The 2006-2013 age-standardized incidence (per 100,000 population per year) was European, 33; Asian, 28; Pasifika, 27; Maori, 20. The 2013 age-standardized prevalence (per 100,000 population) was European, 223; Asian, 174; Pasifika, 160; Maori, 114. CONCLUSIONS: There is a differential occurrence of Parkinson's disease across the major ethnic groups within the New Zealand population, with indigenous Maori showing the lowest incidence. Varying susceptibility profiles, gene-environment interactions, and inequalities in accessing health care may play a role in the variation in rates of Parkinson's disease in New Zealand. © 2018 International Parkinson and Movement Disorder Society.

Response to "Parkinson's disease mild cognitive impairment classifications and neurobehavioral symptoms".

A recent paper, "Parkinson's disease mild cognitive impairment classifications and neurobehavioral symptoms" (McDermott et al., 2017), provides an interesting comparison of the influence of different criteria for Parkinson's disease with mild cognitive impairment (PD-MCI) on progression to dementia (PDD). Unfortunately, McDermott et al. (2017) incorrectly stated that "only 21% of PD-MCI participants (identified with a 1.5 SD cut-off) converted to PDD within four years" (p.6) in our study (Wood et al., 2016). However, the important point made by Wood et al. (2016) was that the proportion of conversions to PDD was 51% when the PD-MCI diagnosis required a minimum of two 1.5 SD impairments within any single cognitive domain, whereas additional PD-MCI patients classified with one impairment at 1.5 SD in each of the two domains (but never two impairments in the same domain) had a non-significant risk of dementia relative to non-MCI patients (11% vs. 6% converted, respectively). Our PDD conversion rate was 38% when combining both 1.5 SD criteria (21/56 PD-MCI patients vs. 4/65 non-MCI patients converted); McDermott et al. (2017) found a 42% conversion rate over three years for similarly described PD-MCI patients (10/24 PD-MCI patients vs. 0/27 non-MCI patients converted). Our study was also part of a multinational study (n = 467) showing that PD-MCI has predictive validity beyond known demographic and PD-specific factors of influence (Hoogland et al., 2017). All three studies found that multiple cognitive domain impairments are common in PD-MCI. Nonetheless, the research community needs to clarify the association between PD-MCI subtypes and, especially, the optimal cognitive markers for dementia risk in PD patients.

Metabolite ratios in the posterior cingulate cortex do not track cognitive decline in Parkinson's disease in a clinical setting.

INTRODUCTION: Parkinson's Disease (PD) is classified as a motor disorder, but most patients develop cognitive impairment, and eventual dementia (PDD). Predictive neurobiomarkers may be useful in the identification of those patients at imminent risk of PDD. Given the compromised cerebral integrity in PDD, we investigated whether brain metabolites track disease progression over time. METHODS: Proton Magnetic Resonance Spectroscopy (MRS) was used to identify brain metabolic changes associated with cognitive impairment and dementia in PD. Forty-nine healthy participants and 130 PD patients underwent serial single voxel proton MRS and neuropsychological testing. At baseline patients were classified as either having normal cognitive status (PDN, n = 77), mild cognitive impairment (PDMCI, n = 33), or dementia (PDD, n = 20). Posterior cingulate cortex (PCC) was examined to quantify N-acetylaspartate (NAA), choline (Cho), creatine (Cr), and myo-inositol (mI). A hierarchical Bayesian model was used to assess whether cognitive ability and other covariates were related to baseline MRS values and changes in MRS over time. RESULTS: At baseline, relative to controls, PDD had significantly decreased NAA/Cr and increased Cho/Cr. However, these differences did not remain significant after accounting for age, sex, and MDS-UPDRS III. At follow-up, no significant changes in MRS metabolite ratios were detected, with no relationship found between MRS measures and change in cognitive status. CONCLUSIONS: Unlike Alzheimer's disease, single voxel MR spectroscopy of the PCC failed to show any significant association with cognitive status at baseline or over time. This suggests that MRS of PCC is not a clinically useful biomarker for tracking or predicting cognitive impairment in Parkinson's disease.

Different PD-MCI criteria and risk of dementia in Parkinson's disease: 4-year longitudinal study.

The Movement Disorder Society Task Force (MDS-TF) has proposed diagnostic criteria for mild cognitive impairment in Parkinson's disease (PD-MCI). We hypothesized that the risk of dementia (PDD) varies across the different cutoff schemes allowed. A longitudinal study followed 121 non-demented PD patients for up to 4.5 years. In Part One, unique groups of patients were identified as PD-MCI at baseline using the MDS-TF requirement of two impaired cognitive test scores, with both scores classified as impaired at either (i) 2 s.d., (ii) 1.5 s.d. or (iii) 1 s.d. below normative data; relative risk (RR) of PDD was assessed at each criterion. In Part Two, the whole sample was reassessed and (i) RR of PDD determined when two impairments at 1.5 s.d. existed within a single cognitive domain, followed by (ii) RR of PDD in the unique group whose two impairments at 1.5 s.d. did not exist within a single domain (i.e., only across two domains). Twenty-one percent of patients converted to PDD. Part One showed that the 1.5 s.d. criterion at baseline is optimal to maximize progression to PDD over 4 years. Part Two, however, showed that the 1.5 s.d. cutoff produced a high RR of PDD only when two impairments were identified within a single cognitive domain (7.2, 95% confidence interval (CI)=3.4-16.6, P<0.0001; 51% converted). The RR when the 1.5 s.d. impairments occurred only across two different domains, was nonsignificant (1.7, CI=0.5-7.4, P=0.13; 11% converted) and similar to using a 1 s.d. criterion (1.9, CI=0.3-4.3, P=0.13; 8% converted). If the intent of a PD-MCI diagnosis is to detect increased risk of PDD in the next 4 years, optimal criteria should identify at least two impairments at 1.5 s.d. within a single cognitive domain.

Tracking Parkinson's Disease over One Year with Multimodal Magnetic Resonance Imaging in a Group of Older Patients with Moderate Disease.

BACKGROUND & OBJECTIVES: Cross-sectional magnetic resonance imaging (MRI) suggests that Parkinson's disease (PD) is associated with changes in cerebral tissue volume, diffusion tensor imaging metrics, and perfusion values. Here, we performed a longitudinal multimodal MRI study--including structural, diffusion tensor imaging (DTI), and perfusion MRI--to investigate progressive brain changes over one year in a group of older PD patients at a moderate stage of disease. METHODS: Twenty-three non-demented PD (mean age (SD) = 69.5 (6.4) years, disease duration (SD) = 5.6 (4.3) years) and 23 matched control participants (mean age: 70.6 (6.8)) completed extensive neuropsychological and clinical assessment, and multimodal 3T MRI scanning at baseline and one year later. We used a voxel-based approach to assess change over time and group-by-time interactions for cerebral structural and perfusion metrics. RESULTS: Compared to controls, in PD participants there was localized grey matter atrophy over time in bilateral inferior and right middle temporal, and left orbito-frontal cortices. Using a voxel-based approach that focused on the centers of principal white matter tracts, the PD and control cohorts exhibited similar levels of change in DTI metrics. There was no significant change in perfusion, cognitive, or motor severity measures. CONCLUSIONS: In a cohort of older, non-demented PD participants, macrostructural MRI detected atrophy in the PD group compared with the control group in temporal and orbito-frontal cortices. Changes in diffusion MRI along principal white matter tracts over one year were found, but this was not differentially affected by PD.

Comparison of cognitive and UHDRS measures in monitoring disease progression in Huntington's disease: a 12-month longitudinal study.

Progressive cognitive decline is a feature of Huntington's disease (HD), an inherited neurodegenerative movement disorder. Comprehensive neuropsychological testing is the 'gold standard' to establish cognitive status but is often impractical in time-constrained clinics. The study evaluated the utility of brief cognitive tests (MMSE and MoCA), UHDRS measures and a comprehensive neuropsychological tests battery in monitoring short-term disease progression in HD. Twenty-two manifest HD patients and 22 matched controls were assessed at baseline and 12-month. A linear mixed-effect model showed that although the HD group had minimal change in overall global cognition after 12 months, they did show a significant decline relative to the control group. The controls exhibited a practice effect in most of the cognitive domain scores over time. Cognitive decline at 12-month in HD was found in the executive function domain but the effect of this on global cognitive score was masked by the improvement in their language domain score. The varying practice effects by cognitive domain with repeated testing indicates the importance of comparing HD patients to control group in research trials and that cognitive progression over 12 months in HD should not be judged by changes in global cognitive score. The three brief cognitive tests effectively described cognition of HD patients on cross-sectional analysis. The UHDRS cognitive component, which focuses on testing executive function and had low variance over time, is a more reliable brief substitute for comprehensive neuropsychological testing than MMSE and MoCA in monitoring cognitive changes in HD patients after 12 months.

Comparing cerebral perfusion in Alzheimer's disease and Parkinson's disease dementia: an ASL-MRI study.

Emerging evidence suggests that Alzheimer's disease (AD) and Parkinson's disease dementia (PDD) share neurodegenerative mechanisms. We sought to directly compare cerebral perfusion in these two conditions using arterial spin labeling magnetic resonance imaging (ASL-MRI). In total, 17 AD, 20 PDD, and 37 matched healthy controls completed ASL and structural MRI, and comprehensive neuropsychological testing. Alzheimer's disease and PDD perfusion was analyzed by whole-brain voxel-based analysis (to assess absolute blood flow), a priori specified region of interest analysis, and principal component analysis (to generate a network differentiating the two groups). Corrections were made for cerebral atrophy, age, sex, education, and MRI scanner software version. Analysis of absolute blood flow showed no significant differences between AD and PDD. Comparing each group with controls revealed an overlapping, posterior pattern of hypoperfusion, including posterior cingulate gyrus, precuneus, and occipital regions. The perfusion network that differentiated AD and PDD groups identified relative differences in medial temporal lobes (AD

Cross-sectional area of the anterior belly of the digastric muscle: comparison of MRI and ultrasound measures.

Changes in morphometry of head and neck muscles have received little attention in research relative to limb muscles. While recent literature suggests that high-frequency ultrasound transducers can provide superior spatial resolution compared to that of magnetic resonance imaging (MRI), no studies have compared these imaging methods for investigating the submental muscle group. This preliminary study sought to compare ultrasound and MRI as a method of quantifying the cross-sectional area (CSA) of the submental muscle group. Measurements were taken from coronal ultrasound and MRI images in 11 healthy participants. Comparisons were limited to the anterior belly of the digastric muscle because of differences in imaging resolution. Ultrasound CSA measurements were smaller than MRI measurements (p = 0.01) by 10 % (95% CI = -18 to -2). Correlations were significant and relatively high (left: r = 0.909, p < 0.001; right: r = 0.776, p = 0.005). Ultrasound imaging has the advantages of natural participant positioning, superior clarity of muscle borders of the submental muscles, requires less acquisition time, and is a less expensive method of imaging compared to MRI. This preliminary study has shown that ultrasound is a viable imaging modality for quantitative measurements of the anterior belly of the digastric muscle and has advantages over MRI beyond cost and accessibility.

The influence of motor and cognitive impairment upon visually-guided saccades in Parkinson's disease.

Studies of saccades in Parkinson's disease (PD) have seldom examined the influence of cognitive status, ranging from normal cognition, through mild cognitive impairment, to dementia. In a large and heterogeneous sample, we examined how motor and cognitive impairment was reflected in the performance of reflexive, visually-guided saccades. We examined 163 people with PD and 47 similar-aged controls. Ninety three of the PD group had normal cognition (PDN), 48 had mild cognitive impairment (PD-MCI), and 22 had dementia (PDD). Pseudo-random targets (amplitudes of 5, 10, 15 and 20 deg and inter-stimulus-intervals ranging from 550 to 1800 ms) were shown in 108 mixed randomised trials, incorporating gap, step, and overlap onset conditions. Analyses were conducted using multi-level regression modeling. Participants were first assessed by continuous measures (Unified PD Rating Scale motor score and the Montreal Cognitive Assessment). Prolonged latency was significantly related to both motor and cognitive impairment, with the cognitive effect being compounded by increasing age. Decreased saccade amplitude, meanwhile, was primarily related to motor impairment. When assessed by discrete cognitive categories, all of the PD groups showed reduced saccadic amplitude relative to controls. Saccadic latencies, meanwhile, were abnormally prolonged only in the PD-MCI and PDD groups (the control and PDN groups were similar to each other). Latency in the overlap task was particularly sensitive to increasing motor and cognitive impairment. We conclude that reflexive saccades in PD are subtly decreased in amplitude even early in the disease process. Prolonged saccade latency, meanwhile, tends to occur later in the disease process, in the presence of more substantial motor and cognitive impairment, and greater age. The progressive impairment of reflexive saccades, and the differential onset of amplitude and latency impairments, may make them a useful objective tool for assessing disease status.

Pharyngeal pressures during swallowing within and across three sessions: within-subject variance and order effects.

No studies have investigated within-subject variation in measures of pharyngeal pressures during swallowing across sessions. This study aimed to document the variation in pharyngeal pressures both within and across three sessions. Twenty healthy participants were recruited for three sessions. For each session, peak or nadir pressures were recorded from the upper pharynx (sensor 1), mid-pharynx (sensor 2), and upper esophageal sphincter (sensor 3) during saliva and 10-ml water bolus swallows. Variance was larger across sessions than within sessions for sensors 1 and 2 but comparable for sensor 3. For all sensors there was a high correlation between the variance across sessions and within session (r = 0.92, p < 0.0001). There were no significant order effects of session or of trial at any sensor with estimated order effects less than 2% and the estimated maximum possible change no larger than 5% for trial and no larger than 12% for session. These data offer direction for longitudinal treatment studies in which pharyngeal pressures are an outcome measurement by (1) providing a basis for power calculations, (2) estimating the likely values of any confounding order effects, and (3) providing suggestions for more reliable data analysis.