Visual and spatial symptoms in Parkinson’s disease

Sex-dependent associations of serum BDNF, glycolipid metabolism and cognitive impairments in Parkinson's disease with depression: a comprehensive analysis

Brain-derived neurotrophic factor (BDNF) and glycolipid metabolism have been implicated in cognitive impairments and depression among Parkinson's disease (PD). However, the role of sex differences in this relationship remains elusive. This study aimed to investigate the potential sex differences in the link between serum BDNF levels, glycolipid metabolism and cognitive performance among depressive PD patients. PD patients comprising 108 individuals with depression and 108 without depression were recruited for this study. Cognitive function was assessed using the Montreal Cognitive Assessment Beijing version (MOCA-BJ). The severity of depressive symptoms was assessed using the Hamilton Depression Rating Scale (HAMD-17), while motor symptoms were evaluated using the Revised Hoehn and Yahr rating scale (H-Y) and the Unified Parkinson's Disease Rating Scale Part III (UPDRS-III). Laboratory testing and enzyme-linked immunosorbent assay (ELISA) are used to measure serum levels of glycolipid metabolism and BDNF. Females showed superior performance in delayed recall (all p < 0.05), male PD patients exhibited higher scores in naming tasks compared to females in non-depression group. There was no sex differences in serum BDNF levels between depression and non-depression groups. Liner regression analysis indicated BDNF as an independent risk factor for language deficits in male PD patients with depression (p < 0.05), while cholesterol (CHOL) emerged as a cognitive influencing factor, particularly in delayed recall among male PD patients with depression (p < 0.05). Our study reveals extensive cognitive impairments in PD patients with depression. Moreover, BDNF and CHOL may contribute to the pathological mechanisms underlying cognitive deficits, particularly in male patients with depression.

Navigating Visual Challenges: How Parkinson's Disease Alters Cognitive Priorities in Visual Search

OBJECTIVE

Parkinson's disease (PD) hampers visual search tasks such as reading, driving, and navigation. We examined expectations from past experiences, guiding cognition and contextual priors, on visual search in PD.

METHODS

We compared eye movements as PD and healthy participants searched for a hidden object (target) in cluttered real-world scenes.

RESULTS

PD participants prolonged fixation on high-probability (high-prior) locations for the target, consistent across expected and unexpected scenario. Such emphasis on contextual visual priors, evidenced by high fixation duration on high-probability areas, was beneficial when the target was at the expected location but presented challenges when the target was situated in an unlikely place.

CONCLUSION

This study contributes to understanding how PD impacts visual search behavior and cognitive processing. The findings indicate that PD alters attention allocation and visual processing by affecting the utilization of contextual visual priors. It provides insights for potential interventions targeting visuo-cognitive deficits in PD patients. Published 2024. This article is a U.S. Government work and is in the public domain in the USA.

Deep Brain Stimulation Modulates the Visual Pathway to Improve Freezing of Gait in Parkinson's Disease Patients

OBJECTIVE

To investigate the involvement of the visual cortex in improving freezing of gait (FoG) after subthalamic nucleus (STN) deep brain stimulation (DBS) in Parkinson's disease (PD) patients using whole-brain seed-based functional connectivity.

METHODS

A total of 66 PD patients with FoG who underwent bilateral STN-DBS were included in our study. Patients were divided into a FoG responder group and an FoG nonresponder group according to whether FoG improved 1 year after DBS. We compared the differences in clinical characteristics, brain structural imaging, and seed-based functional connectivity between the 2 groups. The locations of active contacts were further analyzed.

RESULTS

All PD patients benefited from STN-DBS. No significant differences in the baseline characteristics or brain structures were found between the 2 groups. Seed-based functional connectivity analysis revealed that better connectivity in bilateral primary visual areas was associated with better clinical improvement in FoG (P < 0.05 familywise error corrected). Further analysis revealed that this disparity was associated with the location of the active contacts within the rostral region of the sensorimotor subregion in the FoG responder group, in contrast to the findings in the FoG nonresponder group.

CONCLUSIONS

This study suggested that DBS in the rostral region of the STN sensorimotor subregion may alleviate FoG by strengthening functional connectivity in primary visual areas, which has significant implications for guiding surgical strategies for FoG in the future.

Retinal Alterations Predict Early Prodromal Signs of Neurodegenerative Disease

Neurodegenerative diseases are an increasingly common group of diseases that occur late in life with a significant impact on personal, family, and economic life. Among these, Alzheimer's disease (AD) and Parkinson's disease (PD) are the major disorders that lead to mild to severe cognitive and physical impairment and dementia. Interestingly, those diseases may show onset of prodromal symptoms early after middle age. Commonly, the evaluation of these neurodegenerative diseases is based on the detection of biomarkers, where functional and structural magnetic resonance imaging (MRI) have shown a central role in revealing early or prodromal phases, although it can be expensive, time-consuming, and not always available. The aforementioned diseases have a common impact on the visual system due to the pathophysiological mechanisms shared between the eye and the brain. In Parkinson's disease, α-synuclein deposition in the retinal cells, as well as in dopaminergic neurons of the substantia nigra, alters the visual cortex and retinal function, resulting in modifications to the visual field. Similarly, the visual cortex is modified by the neurofibrillary tangles and neuritic amyloid β plaques typically seen in the Alzheimer's disease brain, and this may reflect the accumulation of these biomarkers in the retina during the early stages of the disease, as seen in postmortem retinas of AD patients. In this light, the ophthalmic evaluation of retinal neurodegeneration could become a cost-effective method for the early diagnosis of those diseases, overcoming the limitations of functional and structural imaging of the deep brain. This analysis is commonly used in ophthalmic practice, and interest in it has risen in recent years. This review will discuss the relationship between Alzheimer's disease and Parkinson's disease with retinal degeneration, highlighting how retinal analysis may represent a noninvasive and straightforward method for the early diagnosis of these neurodegenerative diseases.

Patients with Parkinson's disease demonstrate deficits in visual-spatial memory in the Chinese Visual Retention Test

OBJECTIVE

We aimed to explore the existence of visual-spatial memory deficit in patients with Parkinson's disease (PD) without dementia in the Chinese Visual Retention Test, as well as to assess whether their performance is related to age, duration, severity, stage, and dopamine (DA) dose.

METHODS

Forty-two patients with PD and 30 healthy controls were included in our study. The Chinese Visual Retention Test was used to evaluate the visual-spatial memory of the subjects. Parameters of the Chinese Visual Retention Test were compared between the two groups. Correlation analysis and multiple linear regression analysis were used to explore the associations of the Chinese Visual Retention Test with age, duration, severity, stage of PD, and DA dose.

RESULTS

Three correct scores in the Chinese Visual Retention Test were all significantly lower in the PD group than in the control group. The total error scores, error scores of omissions, deformation, and persistence in the PD group were significantly higher than those in the control group. Correlation analysis showed the total error scores in the Chinese Visual Retention Test was positively correlated with UPDRS III score and H-Y classification. Multiple linear regression analysis showed that the total error scores in the Chinese Visual Retention Test were associated with the UPDRS III score and H-Y classification.

CONCLUSION

Patients with PD without dementia had visual-spatial memory deficits in the Chinese Visual Retention Test which may be affected by the severity and clinical stage of PD.

Altered Outer Retinal Structure, Electrophysiology and Visual Perception in Parkinson's Disease

BACKGROUND

Visual biomarkers of Parkinson's disease (PD) are attractive as the retina is an outpouching of the brain. Although inner retinal neurodegeneration in PD is well-established this has overlap with other neurodegenerative diseases and thus outer retinal (photoreceptor) measures warrant further investigation.

OBJECTIVE

To examine in a cross-sectional study whether clinically implementable measures targeting outer retinal function and structure can differentiate PD from healthy ageing and whether these are sensitive to intraday levodopa (L-DOPA) dosing.

METHODS

Centre-surround perceptual contrast suppression, macular visual field sensitivity, colour discrimination, light-adapted electroretinography and optical coherence tomography (OCT) were tested in PD participants (n = 16) and controls (n = 21). Electroretinography and OCT were conducted before and after midday L-DOPA in PD participants, or repeated after ∼2 hours in controls.

RESULTS

PD participants had decreased center-surround contrast suppression (p < 0.01), reduced macular visual field sensitivity (p < 0.05), color vision impairment (p < 0.01) photoreceptor dysfunction (a-wave, p < 0.01) and photoreceptor neurodegeneration (outer nuclear layer thinning, p < 0.05), relative to controls. Effect size comparison between inner and outer retinal parameters showed that photoreceptor metrics were similarly robust in differentiating the PD group from age-matched controls as inner retinal changes. Electroretinography and OCT were unaffected by L-DOPA treatment or time.

CONCLUSIONS

We show that outer retinal outcomes of photoreceptoral dysfunction (decreased cone function and impaired color vision) and degeneration (i.e., outer nuclear layer thinning) were equivalent to inner retinal metrics at differentiating PD from healthy age-matched adults. These findings suggest outer retinal metrics may serve as useful biomarkers for PD.

Retina Oculomics in Neurodegenerative Disease

Ophthalmic biomarkers have long played a critical role in diagnosing and managing ocular diseases. Oculomics has emerged as a field that utilizes ocular imaging biomarkers to provide insights into systemic diseases. Advances in diagnostic and imaging technologies including electroretinography, optical coherence tomography (OCT), confocal scanning laser ophthalmoscopy, fluorescence lifetime imaging ophthalmoscopy, and OCT angiography have revolutionized the ability to understand systemic diseases and even detect them earlier than clinical manifestations for earlier intervention. With the advent of increasingly large ophthalmic imaging datasets, machine learning models can be integrated into these ocular imaging biomarkers to provide further insights and prognostic predictions of neurodegenerative disease. In this manuscript, we review the use of ophthalmic imaging to provide insights into neurodegenerative diseases including Alzheimer Disease, Parkinson Disease, Amyotrophic Lateral Sclerosis, and Huntington Disease. We discuss recent advances in ophthalmic technology including eye-tracking technology and integration of artificial intelligence techniques to further provide insights into these neurodegenerative diseases. Ultimately, oculomics opens the opportunity to detect and monitor systemic diseases at a higher acuity. Thus, earlier detection of systemic diseases may allow for timely intervention for improving the quality of life in patients with neurodegenerative disease.

Side of motor symptom onset predicts sustained attention deficits and motor improvements after attention training in Parkinson's disease

OBJECTIVE

Parkinson's disease (PD) side of motor symptom onset has been associated with distinct cognitive deficits; individuals with left-side onset (LPD) show more visuospatial impairments, whereas those with right-side onset (RPD) show more verbal impairments. Non-spatial attention is a critical cognitive ability associated with motor functioning that is right hemisphere lateralized but has not been characterized with regard to PD side of onset. We compared individuals with LPD and RPD on non-spatial attention tasks and examined differential responses to a 4-week sustained attention training program.

METHOD

Participants included 9 with LPD and 12 with RPD, who performed both brief and extended go/no-go continuous performance tasks and an attentional blink task. Participants also engaged in an at-home sustained attention training program, Tonic and Phasic Alertness Training (TAPAT), 5 days/week for 4 weeks. We assessed cognitive and motor symptoms before and after training, and after a 4-week no-contact period.

RESULTS

At baseline, participants with LPD exhibited worse performance than those with RPD on the extended continuous performance task, indicating specific deficits in sustaining attention. Poorer attention was associated with worse clinical motor scores. Notably, side of onset had a significant effect on clinical motor changes after sustained attention training, with only LPD participants improving after training, and 4/9 showing clinically meaningful improvements.

CONCLUSIONS

Compared to RPD, participants with LPD had poorer sustained attention pre-training and were more likely to improve on clinical motor functioning after sustained attention training. These findings support mechanistic differences between LPD and RPD and suggest potential differential treatment approaches.

Objective assessment of eye alignment and disparity-driven vergence in Parkinson's disease

Background

Self-reported diplopia is described in up to one-third of Parkinson's disease (PD) patients.

Objective

The purpose of our study was to expand our understanding of the mechanistic underpinnings of diplopia in PD. We hypothesize that the time-based control of eye alignment and increased eye deviation under binocular viewing will be related to the fusion-initiating and fusion-maintaining component deficits of disparity-driven vergence in PD.

Methods

We used high-resolution video-oculography to measure eye alignment under binocular and monocular viewing and disparity-driven vergence in 33 PD and 10 age-matched healthy participants. We computed eye deviation and time-based control of eye alignment, occurrence of conjugate saccadic eye movements, latency and gain of vergence (fusion initiation), and variance of eye position at the end of dynamic vergence (fusion maintenance).

Results

We categorized PD subjects into three groups, considering their time-based control of eye alignment as compared to healthy controls in binocular viewing. Group 1 = 45% had good control and spent >80% of the time when the eyes were well-aligned, Group 2 = 26% had intermediate control and spent <80% but greater >5% of the time when the eyes were well-aligned, and Group 3 = 29% had very poor control with increased eye deviation majority of the times (<5% of the time when the eyes were well-aligned). All three groups exhibited greater eye deviation under monocular viewing than controls. PD subjects exhibited fusion-initiating and fusion-maintaining vergence deficits (prolonged latencies, reduced vergence gain, increased variance of fusion-maintaining component) with a greater probability of saccadic movements than controls. Group 2 and Group 3 subjects were more likely to exhibit failure to initiate vergence (>20%) than Group 1 (13%) and controls (0%) trials. No significant difference was found in the Unified Parkinson's Disease Rating Scale (UPDRS-a tool to measure the severity of PD) values between the three PD groups (Group 1 = 33.69 ± 14.22, Group 2 = 38.43 ± 22.61, and Group 3 = 23.44 ± 1, p > 0.05).

Conclusion

The majority of PD subjects within our cohort had binocular dysfunction with increased eye deviation under monocular viewing and disparity-driven vergence deficits. PD subjects with intermediate or poor control of eye deviation under binocular viewing had greater fusion-initiating and fusion-maintaining vergence deficits. The study highlights the importance of assessing binocular dysfunction in PD subjects independent of the severity of motor symptoms.

Resting-state functional magnetic resonance imaging study comparing tremor-dominant and postural instability/gait difficulty subtypes of Parkinson's disease

PURPOSE

The symptom-specific intrinsic neural mechanisms underlying Parkinson's disease (PD) subtypes (tremor dominant [TD] and postural instability gait difficulty [PIGD]) remain unclarified. We examined spontaneous brain activity patterns in TD and PIGD.

MATERIAL AND METHODS

We included 49 patients with PD (21 with TD/28 with PIGD) and 32 healthy controls (HCs) in this study. We conducted analysis of variance and post-hoc analyses of the amplitude of low-frequency fluctuation (ALFF) and regional homogeneity (ReHo) values of the three groups, with age, sex, and gray matter volume as covariates, and a relationship analysis of the ALFF and ReHo values with clinical variables.

RESULTS

In comparison with HCs, PIGD PD patients had increased ALFF values in the right middle occipital gyrus and left superior occipital gyrus and decreased values primarily in the bilateral inferior frontal gyrus (triangular part). TD PD patients had lower ALFF values in the right inferior frontal gyrus (triangular part) and left insula. In comparison to TD PD patients, PIGD PD patients had higher ALFF values in the left middle occipital gyrus and left superior occipital gyrus. In contrast to HCs, TD PD patients demonstrated a reduction of ReHo values in the left middle temporal gyrus, and PIGD patients showed a decrease of ReHo values in the left inferior temporal gyrus.

CONCLUSION

ALFF values increased in the occipital gyrus of the PIGD PD patients, thus providing evidence of a compensatory mechanism of altered motor function in comparison with the TD PD patients.

Visual velocity perception dysfunction in Parkinson's disease

OBJECTIVE

Compared with motor deficits, sensory information processing in Parkinson's disease (PD) is relatively unexplored. While there is increasing interest in understanding the sensory manifestations of PD, the extent of sensory abnormality in PD has remained relatively unexplored. Furthermore, most investigations on the sensory aspects of PD involve motor aspects, causing confounding results. As sensory deficits often arise in early PD development stages, they present a potential technological target for diagnosis and disease monitoring that is affordable and accessible. Considering this, the current study's aim is to assess visual spatiotemporal perception independent of goal directed movements in PD by designing and using a scalable computational tool.

METHODS

A flexible 2-D virtual reality environment was created to evaluate various cases of visual perception. Using the tool, an experimental task quantifying the visual perception of velocity was tested on 37 individuals with PD and 17 age-matched control participants.

RESULTS

PD patients, both ON and OFF PD therapy, displayed perceptual impairments (p = 0.001 and p = 0.008, respectively) at slower tested velocity magnitudes. These impairments were even observed in early stages of PD (p = 0.015).

CONCLUSION

Visual velocity perception is impaired in PD patients, which suggests impairments in visual spatiotemporal processing occur in PD and provides a promising modality to be used with disease monitoring software.

SIGNIFICANCE

Visual velocity perception shows high sensitivity to PD at all stages of the disease. Dysfunction in visual velocity perception may contribute to observed motor dysfunction in PD.

Visual Dysfunction in Parkinson's Disease

Non-motor symptoms in Parkinson's disease (PD) include ocular, visuoperceptive, and visuospatial impairments, which can occur as a result of the underlying neurodegenerative process. Ocular impairments can affect various aspects of vision and eye movement. Thus, patients can show dry eyes, blepharospasm, reduced blink rate, saccadic eye movement abnormalities, smooth pursuit deficits, and impaired voluntary and reflexive eye movements. Furthermore, visuoperceptive impairments affect the ability to perceive and recognize visual stimuli accurately, including impaired contrast sensitivity and reduced visual acuity, color discrimination, and object recognition. Visuospatial impairments are also remarkable, including difficulties perceiving and interpreting spatial relationships between objects and difficulties judging distances or navigating through the environment. Moreover, PD patients can present visuospatial attention problems, with difficulties attending to visual stimuli in a spatially organized manner. Moreover, PD patients also show perceptual disturbances affecting their ability to interpret and determine meaning from visual stimuli. And, for instance, visual hallucinations are common in PD patients. Nevertheless, the neurobiological bases of visual-related disorders in PD are complex and not fully understood. This review intends to provide a comprehensive description of visual disturbances in PD, from sensory to perceptual alterations, addressing their neuroanatomical, functional, and neurochemical correlates. Structural changes, particularly in posterior cortical regions, are described, as well as functional alterations, both in cortical and subcortical regions, which are shown in relation to specific neuropsychological results. Similarly, although the involvement of different neurotransmitter systems is controversial, data about neurochemical alterations related to visual impairments are presented, especially dopaminergic, cholinergic, and serotoninergic systems.

Salivary Exosomes in Health and Disease: Future Prospects in the Eye

Exosomes are a group of vesicles that package and transport DNA, RNA, proteins, and lipids to recipient cells. They can be derived from blood, saliva, urine, and/or other biological tissues. Their impact on several diseases, such as neurodegenerative, autoimmune, and ocular diseases, have been reported, but not fully unraveled. The exosomes that are derived from saliva are less studied, but offer significant advantages over exosomes from other sources, due to their accessibility and ease of collection. Thus, their role in the pathophysiology of diseases is largely unknown. In the context of ocular diseases, salivary exosomes have been under-utilized, thus creating an enormous gap in the literature. The current review discusses the state of exosomes research on systemic and ocular diseases and highlights the role and potential of salivary exosomes as future ocular therapeutic vehicles.

Structural and functional changes in the retina in Parkinson's disease

Parkinson's disease is caused by degeneration of dopaminergic neurons, originating in the substantia nigra pars compacta and characterised by bradykinesia, rest tremor and rigidity. In addition, visual disorders and retinal abnormalities are often present and can be identified by decreased visual acuity, abnormal spatial contrast sensitivity or even difficulty in complex visual task completion. Because of their early onset in patients with de novo Parkinson's disease, the anatomical retinal changes and electrophysiological modification could be valuable markers even at early stages of the disease. However, due to the concomitant occurrence of normal ageing, the relevance and specificity of these predictive values can be difficult to interpret. This review examines retinal dysfunction arising in Parkinson's disease. We highlight the electrophysiological delays and decreased amplitude in the electroretinography recorded in patients and animal models. We relate this to coexisting anatomical changes such as retinal nerve fibre layer and macular thinning, measured using optical coherence tomography, and show that functional measures are more consistent overall than optical coherence-measured structural changes. We review the underlying chemical changes seen with loss of retinal dopaminergic neurons and the effect of levodopa treatment on the retina in Parkinson's disease. Finally, we consider whether retinal abnormalities in Parkinson's disease could have a role as potential markers of poorer outcomes and help stratify patients at early stages of the disease. We emphasise that retinal measures can be valuable, accessible and cost-effective methods in the early evaluation of Parkinson's disease pathogenesis with potential for patient stratification.

Utility of the 20-Item Noise Pareidolia Task (NPT-20) for Assessing Visuoperceptual Disturbances Associated with Complex Visual Hallucinations in Parkinson's Disease

Background

Complex visual hallucinations (VH) are a common complication of Parkinson's disease (PD). Recent studies have demonstrated relevance of face pareidolia to VH in PD and Lewy body dementia (LBD).

Objective

This study examined utility of the 20-item Noise Pareidolia Task (NPT-20) in assessing visuoperceptual disturbances associated with VH in PD.

Methods

Retrospective chart review included 46 consecutive PD patients who completed NPT-20 during clinical neuropsychological evaluation.

Results

About half the sample (43%) reported VH. PD with VH made significantly more false-positive pareidolia errors on the NPT-20 (p < 0.0001). A cut-off of 2 errors yielded 40% sensitivity, 100% specificity to VH; cut-off of 1 yielded 75% sensitivity, 81% specificity. NPT-20 was not associated with any other clinical or demographic factor. Across groups, NPT-20 evinced moderate correlations with visuospatial functioning and visual memory.

Conclusions

Current findings support utility of the NPT-20 for evaluating visuoperceptual disturbances associated with VH in PD.

Narrative Review Concerning the Clinical Spectrum of Ophthalmological Impairments in Parkinson's Disease

Ophthalmic non-motor impairments are common in Parkinson's disease patients, from the onset of the neurodegenerative disease and even prior to the development of motor symptoms. This is a very crucial component of the potential for early detection of this disease, even in its earliest stages. Since the ophthalmological disease is extensive and impacts all extraocular and intraocular components of the optical analyzer, a competent assessment of it would be beneficial for the patients. Because the retina is an extension of the nervous system and has the same embryonic genesis as the central nervous system, it is helpful to investigate the retinal changes in Parkinson's disease in order to hypothesize insights that may also be applicable to the brain. As a consequence, the detection of these symptoms and signs may improve the medical evaluation of PD and predict the illness' prognosis. Another valuable aspect of this pathology is the fact that the ophthalmological damage contributes significantly to the decrease in the quality of life of patients with Parkinson's disease. We provide an overview of the most significant ophthalmologic impairments associated with Parkinson's disease. These results certainly constitute a large number of the prevalent visual impairments experienced by PD patients.

Multisensory Cues for Gait Rehabilitation with Smart Glasses: Methodology, Design, and Results of a Preliminary Pilot

Recent advances in mobile technology have shown that augmented unisensory feedback can be leveraged to improve gait using wearable systems, but less is known about the possible benefits and usability of multisensory (i.e., multimodal) feedback. This paper introduces the preliminary results of an innovative research project aiming to develop an mHealth system including Android smart glasses, and providing multisensory cues for gait rehabilitation of people affected by Parkinson's disease in and out of the medical context. In particular, the paper describes a preliminary pilot focusing on the design of visual, auditory, and haptic cues, and testing the design methodologies to be used in further developments of the project. Considered research questions were: Which kinds of images, sounds, and vibrations mostly influence gait speed, stride length, and cadence? Which are the ones stressing the user the least? Which ones induce the most immediate reaction? Thus, in this starting part of the research project, different typologies of sensory cues were designed, tested, and evaluated considering quantitative and qualitative parameters to properly answer the research questions.

[Features of visual, cognitive and neuroimaging changes in Parkinson's disease patients with freezing of gait]

OBJECTIVE

To determine visual and cognitive impairments in relation to MRI changes in patients with freezing of Gait (FOG) in Parkinson's disease (PD).

MATERIAL AND METHODS

We examined 78 patients with PD without dementia, who were divided into groups according to the presence (FOG«+» group) or absence (FOG«-» group) of «freezing» episodes.

RESULTS

A decrease in contrast sensitivity (CS) and retinal photosensitivity was determined in all subjects with PD, but in patients with FOG, the decrease in CS was more pronounced. There was a significant decrease in the volume of the cuneus, lingual gyrus, posterior cingulate gyrus, superior parietal lobe and middle frontal gyrus in the FOG«+» group. It was revealed that patients with FOG had cognitive impairments of both the frontal and posterior cortical subtypes, while in the FOG«-» group, only visuospatial deficit prevailed. A direct correlation was determined between the severity of FOG and part I of the UPDRS scale, between a decrease in CS and cortical areas related to the dorsal and ventral visual information processing systems. The presence of a negative relationship between the scores of the FOG-Q, Timed Up and Go test and the volume of cortical areas of the frontal lobe responsible for planning and programming of movements indicates their role in the development of FOG in PD.

CONCLUSION

Thus, visual impairments associated with PD, along with a heterogeneous profile of cognitive impairment, make a significant contribution to the development of FOG.

Multilingual evaluation of interpretable biomarkers to represent language and speech patterns in Parkinson's disease

Motor impairments are only one aspect of Parkinson's disease (PD), which also include cognitive and linguistic impairments. Speech-derived interpretable biomarkers may help clinicians diagnose PD at earlier stages and monitor the disorder's evolution over time. This study focuses on the multilingual evaluation of a composite array of biomarkers that facilitate PD evaluation from speech. Hypokinetic dysarthria, a motor speech disorder associated with PD, has been extensively analyzed in previously published studies on automatic PD evaluation, with a relative lack of inquiry into language and task variability. In this study, we explore certain acoustic, linguistic, and cognitive information encoded within the speech of several cohorts with PD. A total of 24 biomarkers were analyzed from American English, Italian, Castilian Spanish, Colombian Spanish, German, and Czech by conducting a statistical analysis to evaluate which biomarkers best differentiate people with PD from healthy participants. The study leverages conceptual robustness as a criterion in which a biomarker behaves the same, independent of the language. Hence, we propose a set of speech-based biomarkers that can effectively help evaluate PD while being language-independent. In short, the best acoustic and cognitive biomarkers permitting discrimination between experimental groups across languages were fundamental frequency standard deviation, pause time, pause percentage, silence duration, and speech rhythm standard deviation. Linguistic biomarkers representing the length of the narratives and the number of nouns and auxiliaries also provided discrimination between groups. Altogether, in addition to being significant, these biomarkers satisfied the robustness requirements.

Reading Difficulties in Parkinson's Disease: A Stepped Care Model for Neurovisual Rehabilitation

BACKGROUND

People with Parkinson's disease (PD) frequently experience reading difficulties. Little is known about what functional impairments distinguish people with PD with and without reading difficulties and how these should guide rehabilitation.

OBJECTIVE

To provide concrete advice for an efficient stepped care model for reading difficulties in PD, based on extensive functional assessments.

METHODS

This study included 74 people with PD in a neurovisual rehabilitation setting who underwent assessment of visual, visuoperceptual, and cognitive functions. Outcomes were compared between those with frequent (RD+; N = 55) and infrequent reading difficulties (RD-; N = 19). Aids and advice provided during rehabilitation were registered.

RESULTS

Only a few functions appeared to distinguish RD+ and RD-. Visual functions (i.e., contrast sensitivity, g = 0.76; reading acuity, g = 0.66; visual acuity, g = 0.54) and visuoperceptual functions (i.e., visual attention, g = 0.58, visual motor speed, g = 0.56) showed significant worse scores in RD+ compared to RD-. Aids and advice applied consisted mainly of optimizing refraction, improving lighting, and optimizing text size and spacing.

CONCLUSION

The test battery showed significant differences between RD+ and RD-on only a few tests on visual and visuoperceptual functions. The applied aids and advice matched well with these impairments. Therefore, we recommend a stepped care model, starting with a short test battery on these functions. If this battery indicates functional impairments, this can be followed by standard aids and advice to improve reading. Only in case of insufficient effect additional testing should take place.

Characterisation of functional deficits induced by AAV overexpression of alpha-synuclein in rats

Background

In the last decades different preclinical animal models of Parkinson's disease (PD) have been generated, aiming to mimic the progressive neuronal loss of midbrain dopaminergic (DA) cells as well as motor and non-motor impairment. Among all the available models, AAV-based models of human alpha-synuclein (h-aSYN) overexpression are promising tools for investigation of disease progression and therapeutic interventions.

Objectives

The goal with this work was to characterise the impairment in motor and non-motor domains following nigrostriatal overexpression of h-aSYN and correlate the behavioural deficits with histological assessment of associated pathology.

Methods

Intranigral injection of an AAV9 expressing h-aSYN was compared with untreated animals, 6-OHDA and AAV9 expressing either no transgene or GFP. The animals were assessed on a series of simple and complex behavioural tasks probing motor and non-motor domains. Post-mortem neuropathology was analysed using immunohistochemical methods.

Results

Overexpression of h-aSYN led to progressive degeneration of DA neurons of the SN and axonal terminals in the striatum (STR). We observed extensive nigral and striatal pathology, resembling that of human PD brain, as well as the development of stable progressive deficit in simple motor tasks and in non-motor domains such as deficits in motivation and lateralised neglect.

Conclusions

In the present work we characterized a rat model of PD that closely resembles human PD pathology at the histological and behavioural level. The correlation of cell loss with behavioural performance enables the selection of rats which can be used in neuroprotective or neurorestorative therapies.

Motion sickness susceptibility and visually induced motion sickness as diagnostic signs in Parkinson's disease

Postural instability and loss of vestibular and somatosensory acuity can be part of the signs encountered in Parkinson's Disease (PD). Visual dependency is described in PD. These modifications of sensory input hierarchy are predictors of motion sickness (MS). The aim of this study was to assess MS susceptibility and effects of real induced MS in posture. 63 PD patients, whose medication levels (levodopa) reflected the pathology were evaluated, and 27 healthy controls, filled a MS questionnaire; 9 PD patients and 43 healthy controls were assessed by posturography using virtual reality. Drug amount predicted visual MS (p=0.01), but not real induced MS susceptibility. PD patients did not experience postural instability in virtual reality, contrary to healthy controls. Since PD patients do not seem to feel vestibular stimulated MS, they may not rely on vestibular and somatosensory inputs during the stimulation. However, they feel visually induced MS more with increased levodopa drug effect. Levodopa amount can increase visual dependency. The strongest MS predictors must be studied in PD to better understand the effect of visual stimulation and its absence in vestibular stimulation.

Exploring the feasibility of technological visuo-cognitive training in Parkinson's: Study protocol for a pilot randomised controlled trial

Visual and cognitive dysfunction are common in Parkinson's disease and relate to balance and gait impairment, as well as increased falls risk and reduced quality of life. Vision and cognition are interrelated (termed visuo-cognition) which makes intervention complex in people with Parkinson's (PwP). Non-pharmacological interventions for visuo-cognitive deficits are possible with modern technology, such as combined mobile applications and stroboscopic glasses, but evidence for their effectiveness in PwP is lacking. We aim to investigate whether technological visuo-cognitive training (TVT) can improve visuo-cognitive function in PwP. We will use a parallel group randomised controlled trial to evaluate the feasibility and acceptability of TVT versus standard care in PwP. Forty PwP who meet our inclusion criteria will be randomly assigned to one of two visuo-cognitive training interventions. Both interventions will be carried out by a qualified physiotherapist in participants own homes (1-hour sessions, twice a week, for 4 weeks). Outcome measures will be assessed on anti-parkinsonian medication at baseline and at the end of the 4-week intervention. Feasibility of the TVT intervention will be assessed in relation to safety and acceptability of the technological intervention, compliance and adherence to the intervention and usability of equipment in participants homes. Additionally, semi structured interviews will be conducted to explore participants' experience of the technology. Exploratory efficacy outcomes will include change in visual attention measured using the Trail Making Test as well as changes in balance, gait, quality of life, fear of falling and levels of activity. This pilot study will focus on the feasibility and acceptability of TVT in PwP and provide preliminary data to support the design of a larger, multi-centre randomised controlled trial. This trial is registered at isrctn.com (ISRCTN46164906).

Feasibility and positive effects of scalp acupuncture for modulating motor and cerebral activity in Parkinson's disease: A pilot study

BACKGROUND

A variety of acupuncture therapies have shown efficacy in Parkinson's disease (PD).

OBJECTIVE

To evaluate scalp acupuncture (SA) effects on motor and cerebral activity by using gait equipment and resting-state functional magnetic resonance imaging (rs-fMRI).

METHODS

Twelve patients with PD received SA. They underwent the first functional-imaging scan after tactile stimulation and the second scan following needle removal. Gait test and local sensation assessment were performed immediately after each functional scan. Gait parameter differences between pre- and post-SA were analyzed using a paired t-test and altered brain areas in degree centrality (DC) and fractional amplitude of low-frequency fluctuation (fALFF) were identified between the two scans.

RESULTS

Eight patients completed the experiment. Stride length, maximum ankle height, maximum ankle horizontal displacement, gait speed, and range of shank motion significantly increased post-treatment (P <  0.05). fALFF in left middle frontal gyrus and DC in left cerebellum (corrected) increased, while fALFF in left inferior parietal lobule (corrected) during SA decreased, compared with those in tactile stimulation. A positive correlation was observed between right limb swings and both fALFF areas.

CONCLUSIONS

Differences in gait and brain analyses presented modulation to motor and brain activity in PD, thus, providing preliminary evidence for SA efficacy.

Regional Metabolic Changes Influencing Three-Dimensional Perception in Parkinson's Disease

Background and Purpose

Stereopsis refers to the perception of depth and awareness of the distance of an object from the observer that results from the brain receiving visual stimuli from both eyes in combination. Patients with idiopathic Parkinson’s disease (PD patients) typically experience problems with vision, eyeball movements, and visual perception due to degeneration of the cells that generate dopamine in the brain. We therefore hypothesized that stereopsis is affected more by visual cortical dysfunction in idiopathic PD than by retina and subcortical structural dysfunction.

Methods

We analyzed stereopsis in 12 PD patients and 7 healthy controls using a three-dimensional (3D) television (TV). Before allowing patients to watch TV, we examined their visual acuity and strabismus using the Titmus Stereo Fly Test, and evaluated their cognitive function using cognitive tests. The patients watched 3D and two-dimensional (2D) versions of a movie with an approximate duration of 17 minutes, and then completed a questionnaire about stereopsis. All subjects underwent brain F-18 fluorodeoxyglucose (FDG) positron-emission tomography after watching the 3D version of the movie. One week later, subjects watched the 2D version of the same movie under the same conditions. Each scan was analyzed using statistical parametric mapping (version 8) software.

Results

The visual cortex was activated less in the PD patients than in the healthy controls when watching the 2D or 3D movie. However, there was no significant difference between watching 2D and 3D movies in the PD patients or healthy controls.

Conclusions

The lower activation of the primary visual cortex in PD patients suggests the presence of dysfunction of the visual cortex. In addition, there was less activation of the visual association cortex in PD patients when watching a 3D movie than in controls under the same conditions. This might be one reason why PD patients do not recognize real and dynamic stereopsis. These findings have clinical significance since they suggest that safety needs to be considered when making devices or programs using 3D or virtual reality for use by patients with various cerebral degenerative diseases.

Weighting for the Beat: Using a Dance Cue to Facilitate Turning in People with Parkinson's Disease and Freezing of Gait

Freezing of gait (FOG) can severely compromise daily functioning in people with Parkinson's disease. Inability to initiate a step from FOG is likely underpinned, at least in part, by a deficient preparatory weight-shift. Conscious attempts to weight-shift in preparation to step can improve success of initiating forward steps following FOG. However, FOG often occurs during turning, where weight-shifting is more complex and risk of falling is higher. We explored the effectiveness of a dance-based ('cha-cha') weight-shifting strategy to re-initiate stepping following FOG during turning. Results suggest that this simple movement strategy can enhance turning steps following FOG, without compromising safety.

Antagonistic network signature of motor function in Parkinson's disease revealed by connectome-based predictive modeling

Motor impairment is a core clinical feature of Parkinson’s disease (PD). Although the decoupled brain connectivity has been widely reported in previous neuroimaging studies, how the functional connectome is involved in motor dysfunction has not been well elucidated in PD patients. Here we developed a distributed brain signature by predicting clinical motor scores of PD patients across multicenter datasets (total n = 236). We decomposed the Pearson’s correlation into accordance and discordance via a temporal discrete procedure, which can capture coupling and anti-coupling respectively. Using different profiles of functional connectivity, we trained candidate predictive models and tested them on independent and heterogeneous PD samples. We showed that the antagonistic model measured by discordance had the best sensitivity and generalizability in all validations and it was dubbed as Parkinson’s antagonistic motor signature (PAMS). The PAMS was dominated by the subcortical, somatomotor, visual, cerebellum, default-mode, and frontoparietal networks, and the motor-visual stream accounted for the most part of predictive weights among network pairs. Additional stage-specific analysis showed that the predicted scores generated from the antagonistic model tended to be higher than the observed scores in the early course of PD, indicating that the functional signature may vary more sensitively with the neurodegenerative process than clinical behaviors. Together, these findings suggest that motor dysfunction of PD is represented as antagonistic interactions within multi-level brain systems. The signature shows great potential in the early motor evaluation and developing new therapeutic approaches for PD in the clinical realm.

Confirmatory factor analysis of the Dutch Screening Visual Complaints questionnaire in people with multiple sclerosis

Background

Visual complaints among people with multiple sclerosis (pwMS) are common, but often difficult to recognize. The Screening Visual Complaints questionnaire (SVCq) has been developed to screen for visual complaints in people with a neurodegenerative disease, including multiple sclerosis (MS). A previous study performed a factor analysis in a normal population which revealed an acceptable one-factor model, a three-factor model and a five-factor model within the SVCq. To increase the usability of the SVCq in people with MS, the purpose of the current study was to investigate the fit of the three models in a cohort of pwMS.

Results

The confirmatory factor analysis on the SVCq in 493 people with MS showed good fit for all the models. The three-factor model (diminished visual perception, altered visual perception and ocular discomfort) outperformed the one-factor model. The five-factor model outperformed both models, which showed that dividing the first factor (diminished visual perception) into three more factors (function-related, luminance-related and task-related) has merit.

Conclusions

All models may be useful in clinical care for pwMS. The one-factor model may give a quick overview of the presence and severity of visual complaints in general. The individual factors, of either the three- or the five factor models, may contribute to a better recognition of the nature of visual complaints in pwMS and may guide further steps in rehabilitation for pwMS with visual complaints.

Self-Reported Visual Complaints in People with Parkinson’s Disease: A Systematic Review

Background:

Scientific research increasingly focuses on visual symptoms of people with Parkinson’s disease (PD). However, this mostly involves functional measures, whereas self-reported data are equally important for guiding clinical care.

Objective:

This review provides an overview of the nature and prevalence of self-reported visual complaints by people with PD, compared to healthy controls.

Methods:

A systematic literature search was performed. Studies from three databases (PubMed, PsycInfo, and Web of Science) were screened for eligibility. Only studies that reported results of visual self-reports in people with idiopathic PD were included.

Results:

One hundred and thirty-nine eligible articles were analyzed. Visual complaints ranged from function-related complaints (e.g., blurred vision, double vision, increased sensitivity to light or changes in contrast sensitivity) to activity-related complaints (e.g., difficulty reading, reaching, or driving). Visual complaints were more prevalent in people with PD compared to healthy controls. The presence of visual complaints leads to a reduced quality of life (QoL). Increased prevalence and severity of visual complaints in people with PD are related to longer disease duration, higher disease severity, and off-state.

Conclusion:

A large proportion of people with PD have visual complaints, which negatively affect QoL. Complaints are diverse in nature, and specific and active questioning by clinicians is advised to foster timely recognition, acknowledgement, and management of these complaints.

α-Synuclein at the Presynaptic Axon Terminal as a Double-Edged Sword

α-synuclein (α-syn) is a presynaptic, lipid-binding protein strongly associated with the neuropathology observed in Parkinson’s disease (PD), dementia with Lewy bodies (DLB), and Alzheimer’s Disease (AD). In normal physiology, α-syn plays a pivotal role in facilitating endocytosis and exocytosis. Interestingly, mutations and modifications of precise α-syn domains interfere with α-syn oligomerization and nucleation that negatively affect presynaptic vesicular dynamics, protein expressions, and mitochondrial profiles. Furthermore, the integration of the α-syn oligomers into the presynaptic membrane results in pore formations, ion influx, and excitotoxicity. Targeted therapies against specific domains of α-syn, including the use of small organic molecules, monoclonal antibodies, and synthetic peptides, are being screened and developed. However, the prospect of an effective α-syn targeted therapy is still plagued by low permeability across the blood–brain barrier (BBB), and poor entry into the presynaptic axon terminals. The present review proposes a modification of current strategies, which includes the use of novel encapsulation technology, such as lipid nanoparticles, to bypass the BBB and deliver such agents into the brain.

Undetected ophthalmological disorders in Parkinson's disease

Background

Ophthalmological disorders are common and frequently disabling for people with Parkinson’s disease (PD). However, details on the prevalence, severity and impact of ophthalmological disorders thus far lacking. We aimed to identify PD patients with undetected ophthalmological disorders in a large cross-sectional, observational study.

Methods

We previously delivered a screening questionnaire to detect ophthalmological symptoms (Visual impairment in PD questionnaire; VIPD-Q) to 848 patients. Here, we report on a subgroup of 102 patients who received complete ophthalmological assessment aimed at identifying clinically relevant ophthalmological diseases, which were classified as either vison-threatening or not. Impact on daily life functioning was measured using the visual functioning-25 questionnaire (VFQ-25) and fall frequency.

Results

Almost all patients (92%) had one or more clinically relevant ophthalmological disorders. Of those, 77% had a potentially vision-threatening disease, while 34% had a potentially treatable ophthalmological disease which impacted on quality of life. The most prevalent ophthalmological disorders were dry eyes (86%), ocular misalignment (50%) and convergence insufficiency (41%). We found a weak but significant association between clinically relevant ophthalmological diseases and both fall frequency (R² = 0.15, p = 0.037) and VFQ-25 score (R² = 0.15, p = 0.02). The VIPD-Q could not correctly identify patients with relevant ophthalmological disorders.

Conclusions

Surprisingly, in our study sample, many participants manifested previously undetected ophthalmological diseases, most of which threatened vision, impacted on daily life functioning and were amenable to treatment. Screening for these ophthalmological disorders using a questionnaire asking about symptoms seems insufficient. Instead, episodic ophthalmological assessments should be considered for PD patients, aiming to identify vision-threatening yet treatable diseases.

Trial registration

Dutch Trial Registration, NL7421.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00415-022-11014-0.

Multimodal brain and retinal imaging of dopaminergic degeneration in Parkinson disease

Parkinson disease (PD) is a progressive disorder characterized by dopaminergic neurodegeneration in the brain. The development of parkinsonism is preceded by a long prodromal phase, and >50% of dopaminergic neurons can be lost from the substantia nigra by the time of the initial diagnosis. Therefore, validation of in vivo imaging biomarkers for early diagnosis and monitoring of disease progression is essential for future therapeutic developments. PET and single-photon emission CT targeting the presynaptic terminals of dopaminergic neurons can be used for early diagnosis by detecting axonal degeneration in the striatum. However, these techniques poorly differentiate atypical parkinsonian syndromes from PD, and their availability is limited in clinical settings. Advanced MRI in which pathological changes in the substantia nigra are visualized with diffusion, iron-sensitive susceptibility and neuromelanin-sensitive sequences potentially represents a more accessible imaging tool. Although these techniques can visualize the classic degenerative changes in PD, they might be insufficient for phenotyping or prognostication of heterogeneous aspects of PD resulting from extranigral pathologies. The retina is an emerging imaging target owing to its pathological involvement early in PD, which correlates with brain pathology. Retinal optical coherence tomography (OCT) is a non-invasive technique to visualize structural changes in the retina. Progressive parafoveal thinning and fovea avascular zone remodelling, as revealed by OCT, provide potential biomarkers for early diagnosis and prognostication in PD. As we discuss in this Review, multimodal imaging of the substantia nigra and retina is a promising tool to aid diagnosis and management of PD.

The use of virtual reality to modify and personalize interior home features in Parkinson's disease

As the second most common progressive neurodegenerative disorder with increased prevalence in the aging population, Parkinson's disease (PD) affects more than 10 million individuals worldwide with approximately 60,000 new cases occurring each year only in the US. While daily living abilities deteriorate in people with PD, they spend a significant amount of time in their homes. Unfortunately, most existing guidelines for home modification design reflect a standardized, singular plan. This study aimed to demonstrate the feasibility of using a virtual reality (VR) system for persons with PD to virtually walk through different home modifications and to adapt and personalize interior features. A sample of 15 participants with idiopathic PD and 24 healthy adults ambulated on a pressure mat, while using a VR headset and hand controller. Both groups envisioned walking through a virtual doorway from a simulated bedroom into its attached bathroom. Design features for the intervention included doorway width and door-frame color. Each participant was randomly assigned to one of three intervention conditions: (1) standard design, (2) enhanced design, and (3) co-design. The codesign module allowed participants to manipulate design features using a hand controller. We recorded 4 movement variables. Participants completed three questionnaires assessing anxiety, system usability, and satisfaction. Healthy control adults revealed no differences in movement or subjective assessment between the three intervention conditions. However, there were significant differences in the PD group between co-design and the other conditions. The changes were appreciated in the baseline measures of gait distance and strikes as well as in the composite gait component score. This study showed that using VR as a participatory design tool for persons with PD is safe and feasible. Additionally, the self-determination of interior design conditions may possibly affect movement performance measures and merits additional controlled trials.

Which Test Is the Best to Assess Visuo-Cognitive Impairment in Patients with Parkinson's Disease with Mild Cognitive Impairment and Dementia? A Systematic Review and Meta-Analysis

BACKGROUND

Visuo-cognitive impairment is common in patients with Parkinson's disease with mild cognitive impairment (PD-MCI) and constitutes a prognostic factor for the conversion to Parkinson's disease dementia (PDD). However, systematic analyses on which neuropsychological tests are most suitable to assess visuo-cognition in PD-MCI and PDD and to differentiate these cognitive stages are lacking.

OBJECTIVE

To review neuropsychological tests used to assess visuo-cognition including visuo-perceptual and visuo-spatial processing, visuo-constructive copying and drawing on command abilities; and to identify the visuo-cognitive subdomain as well as tests most suitable to discriminate between PD-MCI and PDD.

METHODS

MEDLINE, PsycINFO, Web of Science Core Collection, and CENTRAL were systematically searched for relevant studies assessing visuo-cognitive outcomes in patients with PD-MCI and PDD. Risk of bias was assessed using a customized form based on well-established tools. Random-effect meta-analyses were conducted.

RESULTS

33 studies were included in the systematic review. Data of 19 studies were entered in meta-analyses. Considerable heterogeneity regarding applied tests, test versions, and scoring systems exists. Data indicate that visuo-constructive command tasks are the subdomain best suited to discriminate between PD-MCI and PDD. Furthermore, they indicate that the Rey-Osterrieth-Complex-Figure Test (ROCF), Corsi Block-Tapping Test, Judgment of Line Orientation (JLO), and Clock Drawing Test (CDT) are tests able to differentiate between the two stages.

CONCLUSION

We provide suggestions for suitable visuo-cognitive tests (Corsi Block-Tapping Test, or JLO, ROCF, CDT) to improve diagnostic accuracy. Methodological challenges (e.g., heterogeneity of definitions, tests) are discussed and suggestions for future research are provided.

REGISTRATION

https://www.crd.york.ac.uk/prospero/, ID: CRD42018088244.

Cognitive and visual processing performance in Parkinson's disease patients with vs without visual hallucinations: A meta-analysis

IMPORTANCE

Cognitive and visual impairments in Parkinson's Disease Psychosis (PDP) raise the question of whether a specific profile of impaired cognition and visual function is linked to vulnerability to visual hallucinations (VHs). Previous studies have limited sample sizes and only included a sub-sample of tests. This is the first meta-analysis quantifying visuo-cognitive impairments in PDP patients across a spectrum of tests and taking into account potential confounding factors such as levodopa medication, illness duration and general cognitive ability.

OBJECTIVE

Compare visual processing and cognitive performance between PD patients with and without VHs (PDVH and PDnoVH).

METHODS

Four databases (PubMed, PsychINFO, Scopus, WebOfScience) were searched for studies on visual and/or cognitive performance of PDnoVH and PDVH published up to 02/2020. For each task, means and SDs were extracted and standardized-mean-differences (SMDs) between-groups calculated. Effect-sizes (Hedges' g) were calculated for all comparisons and synthesized in random-effects meta-analyses with robust-variance-estimation (accounting for multiple correlated measures within each study per cognitive/visual domain). Publication bias was assessed with funnel plots and Egger intercept.

RESULTS

N = 99 studies including 2508 PDVH patients (mean age 68.4 years) and 5318 PDnoVH (mean age 66.4 years) were included in the seven meta-analyses. PDVH patients performed worse than PDnoVH across all measures of cognition and visual processing, with the greatest between-group effect-sizes in executive functions, attention, episodic memory and visual processing. Study characteristics were not significantly associated with between-group differences in the domains investigated. Age-differences were significantly associated with performance differences in general cognition, working memory and executive functions.

CONCLUSION

Models of PDVH need to incorporate a wider range of cognitive and processing domains than currently included. There is a need for studies disentangling the temporal relationship between cognitive/visual deficits and VHs as early identification of risk before the onset of VHs could mitigate later outcomes such as progression to dementia.

Sensitive immunosensing of α-synuclein protein in human plasma samples using gold nanoparticles conjugated with graphene: an innovative immuno-platform towards early stage identification of Parkinson's disease using point of care (POC) analysis

Parkinson's disease (PD) or simply Parkinson's is a long-term degenerative disorder of the central nervous system, which mainly affects the motor system. Consequently, the detection and quantification of related biomarkers play vital roles in the early-stage diagnosis of PD. In the present study, an innovative electrochemical immunosensor based on gold nanoparticle-modified graphene towards bioconjugation with biotinylated antibody (bioreceptor) was developed for the ultra-sensitive and specific monitoring of the alpha-synuclein (α-synuclein) protein. The synergistic effects between the gold nanoparticles (AuNPs) and graphene drastically enhanced the electrochemical activity of the resulting materials. The enhanced conductivity of the substrate together with the increase in its surface area improved the sensitivity and lowered the detection limit of the capture layer. For the first time, the α-synuclein protein was measured in human plasma samples using bioconjugated AuNP-Gr bioconjugated specific antibody with an acceptable linear range of 4 to 128 ng mL⁻¹ and a lower limit of quantification (LLOQ) of 4 ng mL⁻¹. Accordingly, it is expected that this diagnostic method may be produced in the near future for clinical applications and high-throughput screening of PD using point of care (POC) analysis.

Parkinson's disease (PD) or simply Parkinson's is a long-term degenerative disorder of the central nervous system, which mainly affects the motor system.

Impact of Visual Impairment on Vision-Related Quality of Life in Parkinson's Disease

BACKGROUND

Visual impairment is frequent and highly disabling in Parkinson's disease (PD); however, few studies have comprehensively evaluated its impact on vision-related quality of life.

OBJECTIVE

To evaluate the relationship between visual function tests and the visual impairment perceived by PD patients in daily living activities.

METHODS

We cross-sectionally evaluated 62 PD patients and 33 healthy controls (HC). Visual disability was measured with a comprehensive battery of primary visual function and visual cognition tests (visual outcomes), and vision-related quality of life was evaluated with the National Eye Institute 25-Item Visual Function Questionnaire (NEI VFQ-25). The relationship between visual outcomes and NEI VFQ-25 sub-scores was analyzed with Pearson's correlations and stepwise linear regression.

RESULTS

In PD patients, and not in HC, most NEI VFQ-25 sub-scores were significantly correlated with Cube Analysis and Dot Counting from Visual Object and Space Perception (VOSP) battery (visual perception), Clock Drawing Test (visuoconstructive capacity) and Trail Making Test part-A (visual attention and processing speed) and to a lesser extent with high- and low-contrast visual acuity. Dot Counting (VOSP) was the test primarily associated with most NEI VFQ-25 sub-scores (5 out of 12). Roth-28 color test was the one that best explained the variance of Peripheral Vision (R2: 0.21) and Role Difficulties (R2: 0.36) sub-scores of NEI VFQ-25, while photopic contrast sensitivity explained 41% of Driving sub-score variance.

CONCLUSION

Vision-related quality of life in PD is mainly influenced by alterations in visual perception, visuoconstructive capacity and visual attention and processing speed. Future studies are warranted to confirm and further extend our findings.

Diplopia Is Frequent and Associated with Motor and Non-Motor Severity in Parkinson's Disease: Results from the COPPADIS Cohort at 2-Year Follow-Up

Background and objective: Diplopia is relatively common in Parkinson’s disease (PD) but is still understudied. Our aim was to analyze the frequency of diplopia in PD patients from a multicenter Spanish cohort, to compare the frequency with a control group, and to identify factors associated with it. Patients and Methods: PD patients who were recruited from January 2016 to November 2017 (baseline visit; V0) and evaluated again at a 2-year ± 30 days follow-up (V2) from 35 centers of Spain from the COPPADIS cohort were included in this longitudinal prospective study. The patients and controls were classified as “with diplopia” or “without diplopia” according to item 15 of the Non-Motor Symptoms Scale (NMSS) at V0, V1 (1-year ± 15 days), and V2 for the patients and at V0 and V2 for the controls. Results: The frequency of diplopia in the PD patients was 13.6% (94/691) at V0 (1.9% in controls [4/206]; p < 0.0001), 14.2% (86/604) at V1, and 17.1% (86/502) at V2 (0.8% in controls [1/124]; p < 0.0001), with a period prevalence of 24.9% (120/481). Visual hallucinations at any visit from V0 to V2 (OR = 2.264; 95%CI, 1.269–4.039; p = 0.006), a higher score on the NMSS at V0 (OR = 1.009; 95%CI, 1.012–1.024; p = 0.015), and a greater increase from V0 to V2 on the Unified Parkinson’s Disease Rating Scale–III (OR = 1.039; 95%CI, 1.023–1.083; p < 0.0001) and Neuropsychiatric Inventory (OR = 1.028; 95%CI, 1.001–1.057; p = 0.049) scores were independent factors associated with diplopia (R² = 0.25; Hosmer and Lemeshow test, p = 0.716). Conclusions: Diplopia represents a frequent symptom in PD patients and is associated with motor and non-motor severity.

Recognizing visual complaints in people with multiple sclerosis: Prevalence, nature and associations with key characteristics of MS

BACKGROUND

Visual disturbances are common in multiple sclerosis (MS), but visual complaints may be underestimated. While these complaints decrease quality of life, they may not be discussed during clinic visits. People with MS (pwMS) may not be referred to appropriate care. We therefore investigated the prevalence, nature and associations of visual complaints of pwMS.

METHODS

We performed a cohort study with a comparison group. PwMS (n = 493) and healthy controls (n = 661) filled out the Screening Visual Complaints questionnaire (SVCq). Primary outcomes were the percentage of pwMS and controls that reported the 19 complaints, and total scores of the SVCq. We also compared the scores on the SVCq between different groups of pwMS.

RESULTS

In general, the complaints were reported more often by pwMS than by controls. PwMS especially reported experiencing complaints 'often/always', while controls reported the complaints primarily 'sometimes'. PwMS with and without a history of optic neuritis showed similar complaints. PwMS with a longer disease duration and those with SPMS reported more complaints. EDSS score and disease duration only showed a limited association with discomfort of visual complaints.

CONCLUSION

The prevalence of visual complaints among pwMS is high and any person with MS may experience a wide array of different visual complaints anywhere along the disease course, regardless of a history of optic neuritis. Using the SVCq may help detect pwMS' visual complaints and may facilitate referrals to appropriate care.

Influence of radial optic flow stimulation on static postural balance in Parkinson's disease: A preliminary study

The role of optic flow in the control of balance in persons with Parkinson's disease (PD) has yet to be studied. Since basal ganglia are understood to have a role in controlling ocular fixation, we have hypothesized that persons with PD would exhibit impaired performance in fixation tasks, i.e., altered postural balance due to the possible relationships between postural disorders and visual perception. The aim of this preliminary study was to investigate how people affected by PD respond to optic flow stimuli presented with radial expanding motion, with the intention to see how the stimulation of different retinal portions may alter the static postural sway. We measured the body sway using center of pressure parameters recorded from two force platforms during the presentation of the foveal, peripheral and full field radial optic flow stimuli. Persons with PD had different visual responses in terms of fixational eye movement characteristics, with greater postural alteration in the sway area and in the medio-lateral direction than the age-matched control group. Balance impairment in the medio-lateral oscillation is often observed in persons with atypical Parkinsonism, but not in Parkinson's disease. Persons with PD are more dependent on visual feedback with respect to age-matched control subjects, and this could be due to their impaired peripheral kinesthetic feedback. Visual stimulation of standing posture would provide reliable signs in the differential diagnosis of Parkinsonism.

Dopaminergic Basis of Spatial Deficits in Early Parkinson's Disease

Dopaminergic mechanisms regulating cognitive and motor control were evaluated comparing visuoperceptual and perceptuomotor functions in Parkinson's disease (PD). The performance of PD patients (n = 40) was contrasted with healthy controls (n = 42) across two separate visits (on and off dopaminergic medications) on computerized tasks of perception and aiming to a target at variable stimulus lengths (4, 8, 12 cm). Novel visuoperceptual tasks of length equivalence and width interval estimations without motor demands were compared with tasks estimating spatial deviation in movement termination. The findings support the presence of spatial deficits in early PD, more pronounced with increased discrimination difficulty, and with shorter stimulus lengths of 4 cm for both visuoperceptual and perceptumotor functions. Dopaminergic medication had an adverse impact on visuoperceptual accuracy in particular for length equivalence estimations, in contrast with dopaminergic modulation of perceptuomotor functions that reduced angular displacements toward the target. The differential outcomes for spatial accuracy in perception versus movement termination in PD are consistent with involvement of the direct pathway and models of progressive loss of dopamine through corticostriatal loops. Future research should develop validated and sensitive standardized tests of perception and explore dopaminergic selective deficits in PD to optimize medication titration for motor and cognitive symptoms of the disease.

The starting distance of obstacle circumvention did not affect intersegmental coordination in individuals with Parkinson's disease

BACKGROUND

Obstacle circumvention is a challenging task in Parkinson's disease (PD). Body segments adjustments, such as changing the direction of the trunk, followed by a change in the direction of the head, and modifications in the positioning of the feet, are necessary to circumvent an obstacle during walking. For that, individuals need to identify the distance to the obstacle, its characteristics (such as its dimension), and perform well-coordinated movements. However, PD is characterized by rigidity, which may be increased in the axial axis and compromise the task execution. Also, worsening sensory integration in PD may increase the time to perform these body segments adjustments, thus impairing the movement coordination when starting obstacle circumvention near to the obstacle.

AIM

To determine if the starting distance (1.5 m, 3 m, or 5 m) from the obstacle could modify the intersegmental coordination (specifically, the coordination between head, trunk, and pelvis) during the obstacle circumvention steps in individuals with PD.

METHODS

Fourteen individuals with a diagnosis of idiopathic PD and 15 neurologically healthy individuals (CG) from the community were included in this study. The participants were evaluated in three different gait conditions, according to the starting distance from the obstacle: 1.5 m, 3 m, and 5 m away from the obstacle. Vector coding technique was employed to establish the coupling between head, trunk, and pelvis in the steps immediately before and during obstacle circumvention. Three-way ANOVA's (group, distance, and step) were calculated with the level of significance at p < 0.05.

RESULTS

For all couplings of coordination, there were no effects of distance. However, significant main effects of group and steps (p < 0.05) were found for all couplings with different patterns of coordination: head/pelvis (group: in-phase and anti-phase variables; steps: anti-phase variable), head/trunk (group: trunk variable; steps: in-phase and anti-phase variables) and trunk/pelvis (group: anti-phase; steps: trunk and pelvis). Finally, only head/trunk coupling showed an interaction between group*steps. Individuals with PD showed 7.95% lower head movement (p < 0.024) and 14.85% greater trunk movement than CG (p < 0.002). Also, individuals with PD performed 17.56% greater head movement in the step before the circumvention compared to the step during circumvention (p < 0.044).

CONCLUSION

The starting distance from the obstacle did not influence the pattern of axial intersegmental coordination in both groups. However, how these segments interact in the preparation and during the obstacle circumvention are opposite in individuals with PD. While on the previous step to obstacle circumvention, the head movement was greater than the trunk, during the obstacle circumvention step, individuals with PD rotated the trunk more.

Diplopia in Parkinson's disease: Indication of a cortical phenotype with cognitive dysfunction?

BACKGROUND

Visual disturbances are increasingly recognized as common non-motor symptoms in Parkinson's disease (PD). In PD patients, intermittent diplopia has been found to be associated with the presence of visual hallucinations and the Parkinson's psychosis spectrum. Here, we investigated whether diplopia in PD is associated with other non-motor traits and cognitive impairment.

METHODS

We investigated 50 non-demented PD patients with and without intermittent diplopia and 24 healthy controls for visual disturbances, as well as motor and non-motor symptoms. All participants underwent a neuropsychological test battery; visuospatial abilities were further evaluated with subtests of the Visual Object and Space Perception Battery (VOSP). The two PD patient groups did not differ significantly in age, symptom duration, motor symptom severity, frequency of visual hallucinations, or visual sensory efficiency.

RESULTS

PD patients with diplopia reported more frequent non-motor symptoms including more subjective cognitive problems and apathy without changes in global cognition measures compared to those without diplopia. PD patients with diplopia had greater impairment in several tests of visuospatial function (pentagon copying p = .002; number location p = .001; cube analysis p < .02) and object perception (p < .001) compared to PD patients without diplopia and healthy controls. By contrast, no consistent group differences were observed in executive function, memory, or language.

CONCLUSIONS

PD patients with diplopia have a greater non-motor symptom burden and deficits in visuospatial function compared to PD patients without diplopia. PD patients with diplopia might be prone to a cortical phenotype with cognitive decline and apathy associated with worse prognosis.

Visual Impairments Are Associated With Retinal Microvascular Density in Patients With Parkinson's Disease

Objective

This study aimed to evaluate retinal microvascular density in patients with Parkinson’s disease (PD) and its correlation with visual impairment.

Methods

This cross-sectional study included 24 eyes of 24 patients with PD and 23 eyes of 23 healthy controls. All participants underwent ophthalmic examination, visual evoked potential (VEP) test, 25-item National Eye Institute Visual Function Questionnaire (NEI VFQ-25), and optical coherence tomography angiography (OCTA) examination. The correlation between retinal microvascular density and visual parameter was evaluated using Spearman correlation analysis, and the area under receiver operating characteristic curve (AUROC) was calculated.

Results

Parkinson’s disease patients had prolonged P100 latency (P = 0.041), worse vision-related quality of life (composite score and 3 of 12 subscales in NEI VFQ-25), and decreased vessel density (VD) in all sectors of 3-mm-diameter region (all P < 0.05) compared with healthy controls. There were no statistical differences in the ganglion cell-inner plexiform layer (GCIPL) thickness and retinal nerve fiber layer (RNFL) thickness between the two groups. A negative correlation was found between P100 latency and nasal and superior sectors of macular VD in a 3-mm-diameter region (r = −0.328, P = 0.030; r = −0.302, and P = 0.047, respectively). Macular VD in a 3-mm-diameter region showed diagnostic capacities to distinguish PD patients from healthy controls (AUROCs, ranging from 0.655 to 0.723).

Conclusion

This study demonstrated that decreased retinal microvascular density was correlated with visual impairment in PD patients. Retinal microvasculature change may occur earlier than visual decline and retinal structure change and has the potential to be a promising diagnostic marker for early PD.

Retinal Flow Density Changes in Early-stage Parkinson's Disease Investigated by Swept-Source Optical Coherence Tomography Angiography

Background: Parkinson's Disease (PD) is the second-most common neurodegenerative disease affecting the elderly population. The eye has been referred to as a window to the brain due to its inseparable relationship with the central nervous system. The development of Swept-Source Optical Coherence Tomography (SS-OCT) and Optical Coherence Tomography Angiography (OCTA) technologies has offered us a better imaging modality to study the impact of PD on the retina.Method: Seventy-five eyes of 42 early-stage PD patients and 150 eyes of 75 matched healthy controls were enrolled in the current study. We performed SS-OCT and SS-OCTA to assess retinal nerve fiber layer (RNFL), ganglion cell layer (GCL) + inner plexiform layer (IPL), internal nuclear layer (INL) thickness, and retinal flow density and flow ratio.Results: Our study indicates decreasing superficial and deep flow density in most regions of the retina. Superficial and deep flow parameters were also associated with RNFL, GCL+IPL, and INL thickness. ROC analysis reveals superficial flow density demonstrated an Area Under Curve (AUC) of 0.688, which is greater than deep flow density and retinal thickness measurements.Conclusion: To the best of our knowledge, we are the first study using SS-OCT and SS-OCTA to study superficial and deep retinal flow changes in early-stage PD patients. Our study suggests decreasing retinal flow density provides greater diagnostic power than retinal thickness measurements in the early stage of PD. SS-OCTA parameters could potentially serve as imaging biomarkers in PD diagnosis and staging.

Relating Response Inhibition, Brain Connectivity, and Freezing of Gait in People with Parkinson's Disease

OBJECTIVE

Freezing of gait (FoG) in Parkinson's disease (PD) has been associated with response inhibition. However, the relationship between response inhibition, neural dysfunction, and PD remains unclear. We assessed response inhibition and microstructural integrity of brain regions involved in response inhibition [right hemisphere inferior frontal cortex (IFC), bilateral pre-supplementary motor areas (preSMA), and subthalamic nuclei (STN)] in PD subjects with and without FoG and elderly controls.

METHOD

Twenty-one people with PD and FoG (PD-FoG), 18 without FoG (PD-noFoG), and 19 age-matched controls (HC) completed a Stop-Signal Task (SST) and MRI scan. Probabilistic fiber tractography assessed structural integrity (fractional anisotropy, FA) among IFC, preSMA, and STN regions.

RESULTS

Stop-signal performance did not differ between PD and HC, nor between PD-FoG and PD-noFoG. Differences in white matter integrity were observed across groups (.001 < p < .064), but were restricted to PD versus HC groups; no differences in FA were observed between PD-FoG and PD-noFoG (p > .096). Interestingly, worse FoG was associated with higher (better) mean FA in the r-preSMA, (β = .547, p = .015). Microstructural integrity of the r-IFC, r-preSMA, and r-STN tracts correlated with stop-signal performance in HC (p ≤ .019), but not people with PD.

CONCLUSION

These results do not support inefficient response inhibition in PD-FoG. Those with PD exhibited white matter loss in the response inhibition network, but this was not associated with FoG, nor with response inhibition deficits, suggesting FoG-specific neural changes may occur outside the response inhibition network. As shown previously, white matter loss was associated with response inhibition in elderly controls, suggesting PD may disturb this relationship.

Abnormal Vision-Based Displacement Perception in Parkinson's Disease

In this work, we investigate the effect of Parkinson’s disease (PD), and common corresponding therapies on vision-based perception of motion, a critical perceptual ability required for performing a wide range of activities of daily livings. While PD has been recognized as mainly a motor disorder, sensory manifestation of PD can also play a major role in the resulting disability. In this paper, for the first time, the effect of disease duration and common therapies on vision-based perception of displacement were investigated. The study is conducted in a movement-independent manner, to reject the shadowing effects and isolate the targeted perceptual disorder to the maximum possible extent. Data was collected using a computerized graphical tool on 37 PD patients [6 early-stage de novo, 25 mid-stage using levodopa therapy, six later-stage using deep brain stimulation (DBS)] and 15 control participants. Besides the absolute measurement of perception through a psychometric analysis on two tested position reference magnitudes, we also investigated the linearity in perception using Weber’s fraction. The results showed that individuals with PD displayed significant perceptual impairments compared to controls, though early-stage patients were not impaired. Mid-stage patients displayed impairments at the greater of the two tested reference magnitudes, while late-stage patients were impaired at both reference magnitudes. Levodopa and DBS use did not cause statistically significant differences in absolute displacement perception. The findings suggest abnormal visual processing in PD increasing with disease development, perhaps contributing to sensory-based impairments of PD such as bradykinesia, visuospatial deficits, and abnormal object recognition.

Robot-induced hallucinations in Parkinson's disease depend on altered sensorimotor processing in fronto-temporal network

Hallucinations in Parkinson's disease (PD) are disturbing and frequent non-motor symptoms and constitute a major risk factor for psychosis and dementia. We report a robotics-based approach applying conflicting sensorimotor stimulation, enabling the induction of presence hallucinations (PHs) and the characterization of a subgroup of patients with PD with enhanced sensitivity for conflicting sensorimotor stimulation and robot-induced PH. We next identify the fronto-temporal network of PH by combining MR-compatible robotics (and sensorimotor stimulation in healthy participants) and lesion network mapping (neurological patients without PD). This PH-network was selectively disrupted in an additional and independent cohort of patients with PD, predicted the presence of symptomatic PH, and associated with cognitive decline. These robotics-neuroimaging findings extend existing sensorimotor hallucination models to PD and reveal the pathological cortical sensorimotor processes of PH in PD, potentially indicating a more severe form of PD that has been associated with psychosis and cognitive decline.