Eye Movement Deficits Are Consistent with a Staging Model of pTDP-43 Pathology in Amyotrophic Lateral Sclerosis

Exploring oculomotor challenges in amyotrophic lateral sclerosis: a comprehensive review

Traditionally understood as a motor neuron disease, amyotrophic lateral sclerosis (ALS) is now recognized to involve broader neurodegenerative processes, including the oculomotor system. This narrative review summarizes current evidence on oculomotor dysfunction in ALS, with a focus on its relationship to disease-related motor and cognitive impairments. Specifically, the review examines key eye-tracking (ET) metrics, including saccades, smooth pursuit, and fixation, highlighting their potential to reflect both motor and extramotor degeneration. Notably, patients with bulbar-onset ALS exhibit more pronounced oculomotor impairments. By synthesizing findings on the connection between oculomotor dysfunction and cognitive decline, this review underscores the potential of ET as a noninvasive tool for assessing ALS progression. Oculomotor metrics, as part of a broader understanding of ALS's impact on multiple neural networks, may offer valuable insights to refine patient assessment and care strategies, particularly in advanced disease stages.

[Oculomotor disorders in patients with amyotrophic lateral sclerosis]

Oculomotor disorders are not typical manifestations of amyotrophic lateral sclerosis (ALS). Occasionally, this disease is associated with vertical gaze paresis, presenting a distinct type as «ALS+progressive supranuclear palsy». Studies using eye-tracking methods have revealed a variety of subclinical oculomotor disorders in this disease. These disorders can manifest as changes in reflex and voluntary saccades, antisaccades, smooth tracking eye movements, and fixations. A significant association between oculomotor disorders and clinical manifestations of ALS was reported. The occurrence of oculomotor disorders indicates the involvement of broader neuroanatomical structures, including the prefrontal cortex and basal ganglia. The lack of consistency in the data from different studies and their limited number emphasize the need for further research in this area.

Exploring amyotrophic lateral sclerosis through the visual system: A systematic review

BACKGROUND AND PURPOSE

The human visual system relies on neural networks throughout the brain that are easily accessible for tests exploring eye structures and movements. Over the past two decades, investigations have been carried out on both afferent and efferent components of the visual system in people with amyotrophic lateral sclerosis (ALS). This approach might represent an innovative biomarker research strategy to better characterise the phenotypic variability of ALS. The purpose of this review was to determine whether exploring the visual system of patients with ALS (pwALS) is an effective strategy.

METHODS

The Medline and Web of science databases were searched for studies with terms relating to ALS and vision. Of 1146 references identified, 43 articles were included.

RESULTS

In this review article, both afferent and efferent components of the visual system were found to be impaired in pwALS in the absence of visual complaint, thereby contributing to the hypothesis that ALS is a multisystem disease with sensory involvement. Of note, some areas of the eye remain unexplored (i.e., tears, and retinal function using electroretinography).

CONCLUSIONS

According to the findings available in the literature, investigating the oculomotor system and exploring the ocular surface could represent two key promising strategies to identify new diagnostic biomarkers in pwALS. Further longitudinal studies are needed to identify relevant indicators of disease progression and response to therapeutic intervention.

Changes in saccadic intrusions over time as an objective biomarker to follow ALS disease progression

Objective: Saccadic Intrusions (SIs) are abnormal eye movements during gaze fixation. Studies have indicated the clinical relevance of SIs, especially of square wave jerks (SWJ) in ALS. We used a software-based platform to extract SIs as a part of an interventional drug trial. The objective was to examine SIs' change over time as a potential biomarker of ALS disease progression. Methods: 28 ALS patients (61.95 ± 8.6 years) were assessed with the revised ALS Functional Rating Scale (ALSFRS-R) and with an oculometric test. Changes of SIs over time and correlations with ALSFRS-R and its bulbar subscale were calculated. A power calculation was conducted to understand the practical implications of results. Results: A significant increase of SWJ over trial duration was observed, with an increase in frequency (mean rise of 0.14 ± 0.28, p < 0.01), amplitude (0.001 ± 0.0016 degrees, p < 0.005), overall duration of SWJ (0.13 ± 0.25, in %, p < 0.01), and in their relative part out of all intrusions (0.18 ± 0.32, in %, p < 0.005). Negative correlations were found with the bulbar subscale (R=-0.43, -0.41, -0.39 and -0.47, respectively, p < 0.001). The required sample size for observing a 40% reduction in bulbar aspects when using the oculometric test (α = 0.05 and β = 0.8), was found to be 150 patients per arm, compared with 200 patients using the bulbar subscale. Conclusions: Evaluation of saccadic intrusions during fixation was able to detect disease progression over time, correlated with ALSFRS-R bulbar subscale. Eye movements can potentially serve as an objective biomarker in ALS clinical trials and reduce the required sample size to show clinical effect of therapies.

Oculomotor atypicalities in motor neurone disease: a systematic review

Introduction

Cognitive dysfunction is commonplace in Motor Neurone Disease (MND). However, due to the prominent motor symptoms in MND, assessing patients' cognitive function through traditional cognitive assessments, which oftentimes require motoric responses, may become increasingly challenging as the disease progresses. Oculomotor pathways are apparently resistant to pathological degeneration in MND. As such, abnormalities in oculomotor functions, largely driven by cognitive processes such as saccades and smooth pursuit eye movement, may be reflective of frontotemporal cognitive deficits in MND. Thus, saccadic and smooth pursuit eye movements may prove to be ideal mechanistic markers of cognitive function in MND.

Methods

To ascertain the utility of saccadic and smooth pursuit eye movements as markers of cognitive function in MND, this review summarizes the literature concerning saccadic and smooth pursuit eye movement task performance in people with MND.

Results and discussion

Of the 22 studies identified, noticeable patterns suggest that people with MND can be differentiated from controls based on antisaccade and smooth pursuit task performance, and thus the antisaccade task and smooth pursuit task may be potential candidates for markers of cognition in MND. However, further studies which ascertain the concordance between eye tracking measures and traditional measures of cognition are required before this assumption is extrapolated, and clinical recommendations are made.

Systematic review registration

https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=376620, identifier CRD42023376620.

An EEG & eye-tracking dataset of ALS patients & healthy people during eye-tracking-based spelling system usage

This research presents a dataset consisting of electroencephalogram and eye tracking recordings obtained from six patients with amyotrophic lateral sclerosis (ALS) in a locked-in state and one hundred seventy healthy individuals. The ALS patients exhibited varying degrees of disease progression, ranging from partial mobility and weakened speech to complete paralysis and loss of speech. Despite these physical impairments, the ALS patients retained good eye function, which allowed them to use a virtual keyboard for communication. Data from ALS patients was recorded multiple times at their homes, while data from healthy individuals was recorded once in a laboratory setting. For each data recording, the experimental design involved nine recording sessions per participant, each corresponding to a common human action or demand. This dataset can serve as a valuable benchmark for several applications, such as improving spelling systems with brain-computer interfaces, investigating motor imagination, exploring motor cortex function, monitoring motor impairment progress in patients undergoing rehabilitation, and studying the effects of ALS on cognitive and motor processes.

Self-Recording of Eye Movements in Amyotrophic Lateral Sclerosis Patients Using a Smartphone Eye-Tracking App

Introduction

Amyotrophic lateral sclerosis (ALS) can affect various eye movements, making eye tracking a potential means for disease monitoring. In this study, we evaluated the feasibility of ALS patients self-recording their eye movements using the "EyePhone," a smartphone eye-tracking application.

Methods

We prospectively enrolled ten participants and provided them with an iPhone equipped with the EyePhone app and a PowerPoint presentation with step-by-step recording instructions. The goal was for the participants to record their eye movements (saccades and smooth pursuit) without the help of the study team. Afterward, a trained physician administered the same tests using video-oculography (VOG) goggles and asked the participants to complete a questionnaire regarding their self-recording experience.

Results

All participants successfully completed the self-recording process without assistance from the study team. Questionnaire data indicated that participants viewed self-recording with EyePhone favorably, considering it easy and comfortable. Moreover, 70% indicated that they prefer self-recording to being recorded by VOG goggles.

Conclusion

With proper instruction, ALS patients can effectively use the EyePhone to record their eye movements, potentially even in a home environment. These results demonstrate the potential for smartphone eye-tracking technology as a viable and self-administered tool for monitoring disease progression in ALS, reducing the need for frequent clinic visits.

Impairment of oculomotor functions in patients with early to advanced amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) can result into an incomplete locked in state (iLIS), in which communication depends on eye tracking computer devices. Oculomotor function impairments in ALS have been reported, but there is little research, particularly with respect to patients in iLIS. In the present study, we compared reflexive and executive oculomotor function by means of an eye tracking test battery between three groups: advanced ALS patients in iLIS (n = 22), patients in early to middle ALS stages (n = 44) and healthy subjects (n = 32). Patients with ALS showed significant deteriorations in oculomotor functions, with stronger impairments in iLIS. More specifically, ALS patients produced visually guided prosaccades with longer latencies and more frequent hypometria compared to healthy subjects. Longest latencies were obtained in iLIS patients, with a stronger prolongation for vertical than for horizontal prosaccades. ALS patients made more antisaccade errors and generated antisaccades with longer latencies. Smooth pursuit was also impaired in ALS. In the earlier ALS stages, bulbar onset patients presented stronger antisaccade and smooth pursuit deficits than spinal onset patients. Our findings reveal a relevant deterioration of important oculomotor functions in ALS, which increases in iLIS. It includes impairments of reflexive eye movements to loss of executive inhibitory control, indicating a progressing pathological involvement of prefrontal, midbrain and brainstem areas. The assessment of oculomotor functions may therefore provide clinically relevant bio- and progression marker, particularly in advanced ALS.

Biomarkers in amyotrophic lateral sclerosis: current status and future prospects

Disease heterogeneity in amyotrophic lateral sclerosis poses a substantial challenge in drug development. Categorization based on clinical features alone can help us predict the disease course and survival, but quantitative measures are also needed that can enhance the sensitivity of the clinical categorization. In this Review, we describe the emerging landscape of diagnostic, categorical and pharmacodynamic biomarkers in amyotrophic lateral sclerosis and their place in the rapidly evolving landscape of new therapeutics. Fluid-based markers from cerebrospinal fluid, blood and urine are emerging as useful diagnostic, pharmacodynamic and predictive biomarkers. Combinations of imaging measures have the potential to provide important diagnostic and prognostic information, and neurophysiological methods, including various electromyography-based measures and quantitative EEG-magnetoencephalography-evoked responses and corticomuscular coherence, are generating useful diagnostic, categorical and prognostic markers. Although none of these biomarker technologies has been fully incorporated into clinical practice or clinical trials as a primary outcome measure, strong evidence is accumulating to support their clinical utility.

Altered Gaze Control During Emotional Face Exploration in Patients With Amyotrophic Lateral Sclerosis

OBJECTIVES

Up to 50% of patients with amyotrophic lateral sclerosis (ALS) present with cognitive problems and behavioral dysfunctions including recognition of human faces presenting different emotions. We investigated whether impaired processing of emotional faces is associated with abnormal scan paths during visual exploration.

METHODS

Cognitively unimpaired patients with ALS (n = 45) and matched healthy controls (n = 37) underwent neuropsychological assessment and video-based eye tracking. Eye movements were recorded while participants visually explored faces expressing different emotions (neutral, disgusted, happy, fearful, and sad) and houses mimicking faces.

RESULTS

Compared with controls, patients with ALS fixated significantly longer to regions which are not relevant for emotional information when faces expressed fear (p = 0.007) and disgust (p = 0.006), whereas the eyes received less attention in faces expressing disgust (p = 0.041). Fixation duration in any area of interest was not significantly associated with the cognitive state or clinical symptoms of disease severity.

DISCUSSION

In cognitively unimpaired patients with ALS, altered gaze patterns while visually exploring faces expressing different emotions might derive from impaired top-down attentional control with possible involvement of subliminal frontotemporal areas. This may account for indistinctness in emotion recognition reported in previous studies because nonsalient features retrieve more attention compared with salient areas. Current findings may indicate distinct emotion processing dysfunction of ALS pathology, which may be different from, for example, executive dysfunction.

Retinal vessels as a window on amyotrophic lateral sclerosis pathophysiology: A systematic review

Amyotrophic lateral sclerosis (ALS) is a rare fatal motor neuron disease. Although many potential mechanisms have been proposed, the pathophysiology of the disease remains unknown. Currently available treatments can only delay the progression of the disease and prolong life expectancy by a few months. There is still no definitive cure for ALS, and the development of new treatments is limited by a lack of understanding of the underlying biological processes that trigger and promote neurodegeneration. Several scientific results suggest a neurovascular impairment in ALS providing perspectives for the development of new biomarkers and treatments. In this article, we performed a systematic review using PRISMA guidelines including PubMed, EmBase, GoogleScholar, and Web of Science Core Collection to analyze the scientific literature published between 2000 and 2021 discussing the neurocardiovascular involvement and ophthalmologic abnormalities in ALS. In total, 122 articles were included to establish this systematic review. Indeed, microvascular pathology seems to be involved in ALS, affecting all the neurovascular unit components. Retinal changes have also been recently highlighted without significant alteration of the visual pathways. Despite the peripheral location of the retina, it is considered as an extension of the central nervous system (CNS) as it displays similarities to the brain, the inner blood-retinal barrier, and the blood-brain barrier. This suggests that the eye could be considered as a 'window' into the brain in many CNS disorders. Thus, studying ocular manifestations of brain pathologies seems very promising in understanding neurodegenerative disorders, mainly ALS. Optical coherence tomography angiography (OCT-A) could therefore be a powerful approach for exploration of retinal microvascularization allowing to obtain new diagnostic and prognostic biomarkers of ALS.

Different saccadic profile in bulbar versus spinal-onset amyotrophic lateral sclerosis

Two clinical phenotypes characterize the onset of amyotrophic lateral sclerosis (ALS): the spinal variant, with symptoms beginning in the limbs, and the bulbar variant, affecting firstly speech and swallowing. The two variants show some distinct features in the histopathology, localization and prognosis, but to which extent they really differ clinically and pathologically remains to be clarified. Recent neuropathological and neuroimaging studies have suggested a broader spreading of the neurodegenerative process in ALS, extending beyond the motor areas, toward other cortical and deep grey matter regions, many of which are involved in visual processing and saccadic control. Indeed, a wide range of eye movement deficits have been reported in ALS, but they have never been used to distinguish the two ALS variants. Since quantifying eye movements is a very sensitive and specific method for the study of brain networks, we compared different saccadic and visual search behaviours across spinal ALS patients (n = 12), bulbar ALS patients (n = 6) and healthy control subjects (n = 13), along with cognitive and MRI measures, with the aim to define more accurately the two patients subgroups and possibly clarify a different underlying neural impairment. We found separate profiles of visually-guided saccades between spinal (short saccades) and bulbar (slow saccades) ALS, which could result from the pathologic involvement of different pathways. We suggest an early involvement of the parieto-collicular-cerebellar network in spinal ALS and the fronto-brainstem circuit in bulbar ALS. Overall, our data confirm the diagnostic value of the eye movements analysis in ALS and add new insight on the involved neural networks.

Eye Movement Abnormalities in Amyotrophic Lateral Sclerosis in a Tunisian Cohort

Few studies have reported abnormal ocular movements in cases of amyotrophic lateral sclerosis (ALS) and their link with other disease features. Our study aimed to describe and analyse eye movement abnormalities in ALS patients. Specifically, we set out to investigate the correlation between non-motor signs and oculomotor impairment in order to understand the pathogenesis of the disease. All ALS patients seen from 2018 to 2020 in the department of Neurology of Razi hospital underwent the recording of saccadic eye movements. Results were compared with healthy controls. Sixty-two patients were included. Altered saccadic eye movements (72.6%) correlated with tongue atrophy and bladder dysfunction. The most common finding was altered smooth pursuit (56.5%), which showed correlation with bladder dysfunction and altered frontal assessment battery (FAB) scores. Prolonged latencies of horizontal saccades (34%) correlated with sensory and extrapyramidal signs. Our study is the first to examine the characteristics of eye movements in a large African cohort of ALS patients and to show correlations with extra-motor clinical signs. Our findings showed extra-motor cortex dysfunction in ALS with greater frequency of eye movement abnormalities in comparison with previous studies. Altered horizontal pursuit, the core abnormality, confirmed the extension of the neurodegenerative process to the frontal and prefrontal cortices. Prolonged horizontal saccade latencies reflect mainly the involvement of the parietal eye field. Anti-saccadic abnormalities were the least common finding and showed, paradoxically, no link with executive dysfunction.

Multimodal in vivo staging in amyotrophic lateral sclerosis using artificial intelligence

Background

The underlying neuropathological process of amyotrophic lateral sclerosis (ALS) can be classified in a four‐stage sequential pTDP‐43 cerebral propagation scheme. Using diffusion tensor imaging (DTI), in vivo imaging of these stages has already been shown to be feasible for the specific corticoefferent tract systems. Because both cognitive and oculomotor dysfunctions are associated with microstructural changes at the brain level in ALS, a cognitive and an oculomotor staging classification were developed, respectively. The association of these different in vivo staging schemes has not been attempted to date.

Methods

A total of 245 patients with ALS underwent DTI, video‐oculography, and cognitive testing using Edinburgh Cognitive and Behavioral ALS Screen (ECAS). A set of tract‐related diffusion metrics, cognitive, and oculomotor parameters was selected for further analysis. Hierarchical and k‐means clustering algorithms were used to obtain an optimal cluster solution.

Results

According to cluster analysis, differentiation of patients with ALS into four clusters resulted: Cluster A showed the highest fractional anisotropy (FA) values and thereby the best performances in executive oculomotor tasks and cognitive tests, whereas cluster D showed the lowest FA values, the lowest ECAS scores, and the worst executive oculomotor performance across all clusters. Clusters B and C showed intermediate results regarding parameter values.

Discussion

In a multimodal dataset of technical assessments of brain structure and function in ALS, an artificial intelligence‐based cluster analysis showed high congruence of DTI, executive oculomotor function, and neuropsychological performance for mapping in vivo correlates of neuropathological spreading.

Eye Movement Abnormalities in Amyotrophic Lateral Sclerosis

It is generally believed that eye movements are completely spared in amyotrophic lateral sclerosis (ALS). Although a series of eye movement abnormalities has been recognized in recent years, the findings are highly controversial, and bulbar disabilities should be considered in relation to eye movement abnormalities. The present study aimed to determine whether eye movement abnormalities are present in ALS and, if so, to investigate their characteristics and their association with bulbar disability in ALS patients. A total of 60 patients and 30 controls were recruited and underwent the standardized evaluations of the oculomotor system using videonystagmography. Square-wave jerks (OR: 16.20, 95% CI: 3.50−74.95, p < 0.001) and abnormal cogwheeling during smooth pursuit (OR: 14.04, 95% CI: 3.00−65.75, p = 0.001) were more frequently observed in ALS patients than in the control subjects. In subgroup analyses, square-wave jerks (OR: 26.51, 95% CI: 2.83−248.05, p = 0.004) and abnormal cogwheeling during smooth pursuit (OR: 6.56, 95% CI: 1.19−36.16, p = 0.031) were found to be more common in ALS patients with bulbar involvement (n = 44) than in those without bulbar involvement (n = 16). There were no significant differences in the investigated eye movement parameters between bulbar-onset (n = 12) and spinal-onset patients (n = 48). ALS patients showed a range of eye movement abnormalities, affecting mainly the ocular fixation and smooth pursuit systems. Our pioneering study indicates that the region of involvement could better indicate the pathophysiological essence of the abnormalities than the type of onset pattern in ALS. Eye movement abnormalities may be potential clinical markers for objectively evaluating upper brainstem or supratentorial cerebral lesion neurodegeneration in ALS.

Association of Clinically Evident Eye Movement Abnormalities With Motor and Cognitive Features in Patients With Motor Neuron Disorders

BACKGROUND AND OBJECTIVES

Although oculomotor abnormalities (OMAs) are not usually considered prominent features of amyotrophic lateral sclerosis (ALS), they may represent potential clinical markers of neurodegeneration, especially when investigated together with cognitive and behavioral alterations. The aim of our study was to identify patterns of clinically evident OMAs in patients with ALS and to correlate such findings with cognitive-behavioral data.

METHODS

Three consecutive inpatient cohorts of Italian patients with ALS and controls were retrospectively evaluated to assess the frequency of OMAs and cognitive-behavioral alterations. The ALS population was divided into a discovery cohort and a replication cohort. Controls included a cohort of cognitively impaired individuals and patients with Alzheimer disease (AD). Participants underwent bedside eye movement evaluation to determine the presence and pattern of OMAs. Cognitive assessment was performed with a standard neuropsychological battery (discovery ALS cohort and AD cohort) and the Italian Edinburgh Cognitive and Behavioural ALS Screen (ECAS) (replication ALS cohort).

RESULTS

We recruited 864 individuals with ALS (635 discovery, 229 replication), 798 who were cognitively unimpaired and 171 with AD. OMAs were detected in 10.5% of our ALS cohort vs 1.6% of cognitively unimpaired controls (p = 1.2 × 10^-14) and 11.4% of patients with AD (p = NS). The most frequent deficits were smooth pursuit and saccadic abnormalities. OMA frequency was higher in patients with bulbar onset, prominent upper motor neuron signs, and advanced disease stages. Cognitive dysfunction was significantly more frequent in patients with OMAs in both ALS cohorts (p = 1.1 × 10^-25). Furthermore, OMAs significantly correlated with the severity of cognitive impairment and with pathologic scores at the ECAS ALS-specific domains. Last, OMAs could be observed in 35.0% of cognitively impaired patients with ALS vs 11.4% of patients with AD (p = 6.4 × 10^-7), suggesting a possible involvement of frontal oculomotor areas in ALS.

CONCLUSION

Patients with ALS showed a range of clinically evident OMAs, and these alterations were significantly correlated with cognitive, but not behavioral, changes. OMAs may be a marker of neurodegeneration, and bedside assessment represents a rapid, highly specific tool for detecting cognitive impairment in ALS.

Diagnostic value of video-oculography in progressive supranuclear palsy: a controlled study in 100 patients

Background

The eponymous feature of progressive supranuclear palsy (PSP) is oculomotor impairment which is one of the relevant domains in the Movement Disorder Society diagnostic criteria.

Objective

We aimed to investigate the value of specific video-oculographic parameters for the use as diagnostic markers in PSP.

Methods

An analysis of video-oculography recordings of 100 PSP patients and 49 age-matched healthy control subjects was performed. Gain of smooth pursuit eye movement and latency, gain, peak eye velocity, asymmetry of downward and upward velocities of saccades as well as rate of saccadic intrusions were analyzed.

Results

Vertical saccade velocity and saccadic intrusions allowed for the classification of about 70% and 56% of the patients, respectively. By combining both parameters, almost 80% of the PSP patients were covered, while vertical velocity asymmetry was observed in approximately 34%. All parameters had a specificity of above 95%. The sensitivities were lower with around 50–60% for the velocity and saccadic intrusions and only 27% for vertical asymmetry.

Conclusions

In accordance with oculomotor features in the current PSP diagnostic criteria, video-oculographic assessment of vertical saccade velocity and saccadic intrusions resulted in very high specificity. Asymmetry of vertical saccade velocities, in the opposite, did not prove to be useful for diagnostic purposes.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00415-021-10522-9.

Eye movement alterations in presymptomatic C9orf72 expansion gene carriers

Objective

The clinical manifestation of amyotrophic lateral sclerosis (ALS) is characterized by motor neuron degeneration, whereas frontotemporal dementia (FTD) patients show alterations of behavior and cognition. Both share repeat expansions in C9orf72 as the most prevalent genetic cause. Before disease-defining symptoms onset, structural and functional changes at cortical level may emerge in C9orf72 carriers. Here, we characterized oculomotor parameters and their association to neuropsychological domains in apparently asymptomatic individuals with mutations in ALS/FTD genes.

Patients and methods

Forty-eight carriers of ALS genes, without any clinical symptoms underwent video-oculographic examination, including 22 subjects with C9orf72 mutation, 17 with SOD1, and 9 with other ALS associated gene mutations (n = 3 KIF5A; n = 3 FUS/FUS + TBK1; n = 1 NEK1; n = 1 SETX; n = 1 TDP43). A total of 17 subjects underwent a follow-up measurement. Data were compared to 54 age- and gender-matched healthy controls. Additionally, mutation carriers performed a neuropsychological assessment.

Results

In comparison to controls, the presymptomatic subjects performed significantly worse in executive oculomotor tasks such as the ability to perform correct anti-saccades. A gene mutation subgroup analysis showed that dysfunctions in C9orf72 carriers were much more pronounced than in SOD1 carriers. The anti-saccade error rate of ALS mutation carriers was associated with cognitive deficits: this correlation was increased in subjects with C9orf72 mutation, whereas SOD1 carriers showed no associations.

Conclusion

In C9orf72 carriers, executive eye movement dysfunctions, especially the increased anti-saccade error rate, were associated with cognitive impairment and unrelated to time. These oculomotor impairments are in support of developmental deficits in these mutations, especially in prefrontal areas.

Preserved eye movements in adults with spinal muscular atrophy

INTRODUCTION

Spinal muscular atrophy (SMA) most prominently affects proximal limb and bulbar muscles. Despite older case descriptions, ocular motor neuron palsies or other oculomotor abnormalities are not considered part of the phenotype.

METHODS

We investigated oculomotor function by testing saccadic eye movements of 15 patients with SMA. Their performance was compared with that of age-matched healthy controls. Horizontal rightward and leftward saccades were recorded by means of video-oculography, whereas subjects looked at light-emitting diode targets placed at ±5°, ±10°, and ±15° eccentricities.

RESULTS

No differences in saccade amplitude gains, peak velocities, peak velocity-to-amplitude ratios, or durations were observed between controls and patients. More specifically, for 5° target eccentricities, patients had a mean saccadic peak velocity of 153°/s, whereas for 10° and 15° these values were 268°/s and 298°/s, respectively. The corresponding mean peak velocities of the control group were 151°/s, 264°/s, and 291°/s.

DISCUSSION

Our results indicate that patients with SMA perform fast and accurate horizontal saccades without evidence of extraocular muscle weakness. These quantitative oculomotor data corroborate clinical experience that neuro-ophthalmic symptoms in SMA are not common and, if present, should prompt suspicion for an alternative neuromuscular disorder.

Ocular Involvement Occurs Frequently at All Stages of Amyotrophic Lateral Sclerosis: Preliminary Experience in a Large Italian Cohort

Background and Purpose

The study aimed to obtain optometric findings of amyotrophic lateral sclerosis (ALS) patients in different stages of the disease, and to determine the relation between ocular data and ALS-related features; that is, functional and cognitive impairment and staging.

Methods

The optometric protocol included tests of the ocular motility [broad-H test and Northeastern State University College of Optometry (NSUCO) test], near point of convergence (NPC), error refraction, best-corrected visual acuity, and binocular visual alignment, and an ocular symptoms questionnaire. The functional measures included the Amyotrophic Lateral Sclerosis Functional Rating Scale–revised (ALSFRS-r) and Milano-Torino staging (MiToS), and cognitive impairment was assessed using the Edinburgh Cognitive and Behavioural ALS Screen (ECAS). Demographic and clinical features were also collected, including whether the patients used an eye-tracking communication device (ETCD).

Results

Two-hundred consecutive ALS patients (median age of 64 years, 118 males and 82 females) in different stages of disease were recruited. Nearly 70% of patients reported at least one ocular symptom, and the use of an ETCD was found to be significantly related to the presence of most symptoms. Moreover, the severely symptomatic group was characterized by significantly lower ALSFRS-r total and subscale scores, and higher MiToS. Abnormal NPC values were significantly related to lower ALSFRS-r total and bulbar-subscale scores. Patients with acceptable NSUCO test values exhibited significantly higher ECAS scores.

Conclusions

The presence of ocular alteration in patients in different stages of ALS supports the idea that this is a multisystem disorder and emphasizes the importance of optometric evaluations in multidisciplinary assessments to address ocular impairment early in the disease process.

A dataset of EEG and EOG from an auditory EOG-based communication system for patients in locked-in state

The dataset presented here contains recordings of electroencephalogram (EEG) and electrooculogram (EOG) from four advanced locked-in state (LIS) patients suffering from ALS (amyotrophic lateral sclerosis). These patients could no longer use commercial eye-trackers, but they could still move their eyes and used the remnant oculomotor activity to select letters to form words and sentences using a novel auditory communication system. Data were recorded from four patients during a variable range of visits (from 2 to 10), each visit comprised of 3.22 ± 1.21 days and consisted of 5.57 ± 2.61 sessions recorded per day. The patients performed a succession of different sessions, namely, Training, Feedback, Copy spelling, and Free spelling. The dataset provides an insight into the progression of ALS and presents a valuable opportunity to design and improve assistive and alternative communication technologies and brain-computer interfaces. It might also help redefine the course of progression in ALS, thereby improving clinical judgement and treatment.

Auditory Electrooculogram-based Communication System for ALS Patients in Transition from Locked-in to Complete Locked-in State

Patients in the transition from locked-in (i.e., a state of almost complete paralysis with voluntary eye movement control, eye blinks or twitches of face muscles, and preserved consciousness) to complete locked-in state (i.e., total paralysis including paralysis of eye-muscles and loss of gaze-fixation, combined with preserved consciousness) are left without any means of communication. An auditory communication system based on electrooculogram (EOG) was developed to enable such patients to communicate. Four amyotrophic lateral sclerosis patients in transition from locked-in state to completely locked-in state, with ALSFRS-R score of 0, unable to use eye trackers for communication, learned to use an auditory EOG-based communication system. The patients, with eye-movement amplitude between the range of ±200μV and ±40μV, were able to form complete sentences and communicate independently and freely, selecting letters from an auditory speller system. A follow-up of one year with one patient shows the feasibility of the proposed system in long-term use and the correlation between speller performance and eye-movement decay. The results of the auditory speller system have the potential to provide a means of communication to patient populations without gaze fixation ability and with low eye-movement amplitude range.

An overview of screening instruments for cognition and behavior in patients with ALS: selecting the appropriate tool for clinical practice

Objective: Patients with amyotrophic lateral sclerosis (ALS) not only show motor deficits, but may also have cognitive and/or behavioral impairments. Recognizing these impairments is crucial as they are associated with lower quality of life, shorter survival, and increased caregiver burden. Therefore, ALS-specific neuropsychological screening instruments have been developed that can account for motor and speech difficulties. This study provides an overview and comparison of these screeners. Methods: A systematic review was conducted using Medline and Embase. Articles describing cognitive/behavioral screening instruments assessed in ALS patients were included. Screening instruments were compared on multiple factors, such as domains, adaptability, required time, and validation. Results: We included 99 articles, reporting on nine cognitive screeners (i.e. ACE-R, ALS-BCA, ALS-CBS, ECAS, FAB, MMSE, MoCA, PSSFTS, and UCSF-SB), of which five ALS-specific. Furthermore, eight behavioral screeners (i.e. ALS-FTD-Q, AES, BBI, DAS, FBI, FrSBe, MiND-B, and NPI) were reported on, of which three ALS-specific. Conclusion: Considering the broad range of cognitive domains, adaptability, and satisfying validity, the ALS-CBS and ECAS appear to be the most suitable screeners to detect cognitive and behavioral changes in ALS. The BBI appears to be the best option to screen for behavioral changes in ALS, since all relevant domains are assessed, motor-related problems are considered, and has a satisfactory validity. The MiND-B and ALS-FTD-Q are promising as well. In general, all screening instruments would benefit from additional validation research to gain greater insights into test characteristics and to aid clinicians in selecting screening tools for use in clinical practice.

Saccadic intrusions in amyotrophic lateral sclerosis (ALS)

The attempt to quietly fixate at a small visual object is continuously interrupted by a variety of fixational eye movements comprising, among others, a continuum of saccadic intrusions (SI) which range in size from microsaccades with amplitudes ≤0.25° to larger refixation saccades of up to about 2°. The size and frequency of SI varies considerably among individuals and is known to increase in neurodegenerative diseases such as progressive supranuclear palsy (PSP), and amyotrophic lateral sclerosis (ALS). However, studies of ALS disagree whether also the frequency of SI increases. We undertook an analysis of SI in 119 ALS patients and 47 age-matched healthy controls whose eye movements during fixation and tests of executive functions (e.g antisaccades) had been recorded by video-oculography according to standardised procedures. SI were categorised according to their spatio-temporal patterns as stair case, back-and-forth and square wave jerks (a subcategory of back-and-forth). The SI of patients and controls were qualitatively similar (same direction preferences, similar differences between patterns), but were enlarged in ALS. Notably however, no increase of SI frequency could be demonstrated. Yet, there were clear correlations with parameters such as eye blink rate or errors in a delayed saccade task that suggest an impairment of inhibitory mechanisms, in keeping with the notion of a frontal dysfunction in ALS. However, it remains unclear how the impairment of inhibitory mechanisms in ALS could selectively increase the amplitude of intrusions without changing their frequency of occurrence.

Cursive Eye-Writing With Smooth-Pursuit Eye-Movement Is Possible in Subjects With Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder causing a progressive motor weakness of all voluntary muscles, whose progression challenges communication modalities such as handwriting or speech. The current study investigated whether ALS subjects can use Eye-On-Line (EOL), a novel eye-operated communication device allowing, after training, to voluntarily control smooth-pursuit eye-movements (SPEM) so as to eye-write in cursive. To that aim, ALS participants (n = 12) with preserved eye-movements but impaired handwriting were trained during six on-site visits. The primary outcome of the study was the recognition of eye-written digits (0-9) from ALS and healthy control subjects by naïve "readers." Changes in oculomotor performance and the safety of EOL were also evaluated. At the end of the program, 69.4% of the eye-written digits from 11 ALS subjects were recognized by naïve readers, similar to the 67.3% found for eye-written digits from controls participants, with however, large inter-individual differences in both groups of "writers." Training with EOL was associated with a transient fatigue leading one ALS subject to drop out the study at the fifth visit. Otherwise, itching eyes was the most common adverse event (3 subjects). This study shows that, despite the impact of ALS on the motor system, most ALS participants could improve their mastering of eye-movements, so as to produce recognizable eye-written digits, although the eye-traces sometimes needed smoothing to ease digit legibility from both ALS subjects and control participants. The capability to endogenously and voluntarily generate eye-traces using EOL brings a novel way to communicate for disabled individuals, allowing creative personal and emotional expression.

In vivo assessment of retinal vessel pathology in amyotrophic lateral sclerosis

BACKGROUND

Changes in skin and muscle small blood vessels (SBVs) and microvascular structures of the brain have been reported in patients with amyotrophic lateral sclerosis (ALS). A direct assessment of brain SBVs in vivo is currently not feasible. Retinal vessels are considered a "mirror" of brain SBVs. In this study, we used optic coherence tomography (OCT)-based measurements to detect changes in retinal blood vessels of ALS patients compared to those of healthy controls.

METHODS

We analysed Spectralis-OCT images of 34 ALS patients and 20 HCs. The inner wall thickness (IWT), outer wall thickness (OWT), and lumen diameter (LD) of retinal vessels were assessed using intensity-based measurements. In addition, the different retinal layers were analysed using automated segmentation software. The correlations between the various retinal layers and clinical parameters [e.g., disease duration and revised ALS functional rating scale (ALS-FRS-R)] were examined.

RESULTS

The OWT of retinal vessels was higher in ALS patients than in HCs (p = 0.04). There were no differences in the IWT, LD. ALS patients showed a thinning of the outer nuclear layer (ONL) compared to HCs (median 1.63 vs. 1.77, p = 0.002). The whole retinal thickness negatively correlated with the ALS-FRS scale (r = 0.3, p = 0.03).

CONCLUSION

Our study reports retinal vessel pathology in ALS patients. These changes may be related to those observed in SBVs in skin and muscle biopsies. Furthermore, we report a thinning of the ONL in ALS, revealing a possible affection of rods and cones function in ALS.

Is there a glucose metabolic signature of spreading TDP-43 pathology in amyotrophic lateral sclerosis?

BACKGROUND

Recently, four neuropathological stages of amyotrophic lateral sclerosis (ALS) with spreading of transactive response DNA-binding protein-43 pathology were described. Although 18F-FDG PET has been useful in diagnosis and prognosis of ALS patients, in-vivo disease staging using glucose metabolic patterns across the different ALS stages has not been attempted so far. In this study, we investigated whether the discriminant brain regions of the neuropathological stage model can be translated to metabolic patterns for in-vivo staging of ALS. Furthermore, we examined the correlation of these metabolic patterns with disease duration, the Revised ALS Functional Rating Scale (ALSFRS-R) and the forced vital capacity (FVC).

METHODS

A total of 146 ALS patients (age 66.0±11.0 years; 86 male, 60 female) were divided into four metabolic stages depending on glucose metabolism in discriminant regions of neuropathological stages. 18F-FDG data were analysed voxel-based to compare local metabolic patterns between different stages. Additionally, correlation analyses were performed between pathologic stage and clinical parameters.

RESULTS

Relative hypometabolism was present in regions known to be affected from the post-mortem pathological spread model, but relative hypermetabolism was also observed across the different ALS stages. In particular, stage 4 reflected a different frontotemporal pattern discordant with mere progression of stage 1-3, which may point to a potential different subgroup in ALS. Furthermore, metabolic stage correlated with disease duration (Spearman's ρ=-0.21, P=0.01) and FVC (Spearman's ρ=-0.24, P=0.04).

CONCLUSIONS

The neuropathological ALS stages correspond to discriminative regional brain glucose metabolism patterns correlating with disease duration and forced vital capacity. Furthermore, metabolic stage 4 may represents a separate group of ALS progression towards frontotemporal dementia.

Cortical influences drive amyotrophic lateral sclerosis

The early motor manifestations of sporadic amyotrophic lateral sclerosis (ALS), while rarely documented, reflect failure of adaptive complex motor skills. The development of these skills correlates with progressive evolution of a direct corticomotoneuronal system that is unique to primates and markedly enhanced in humans. The failure of this system in ALS may translate into the split hand presentation, gait disturbance, split leg syndrome and bulbar symptomatology related to vocalisation and breathing, and possibly diffuse fasciculation, characteristic of ALS. Clinical neurophysiology of the brain employing transcranial magnetic stimulation has convincingly demonstrated a presymptomatic reduction or absence of short interval intracortical inhibition, accompanied by increased intracortical facilitation, indicating cortical hyperexcitability. The hallmark of the TDP-43 pathological signature of sporadic ALS is restricted to cortical areas as well as to subcortical nuclei that are under the direct control of corticofugal projections. This provides anatomical support that the origins of the TDP-43 pathology reside in the cerebral cortex itself, secondarily in corticofugal fibres and the subcortical targets with which they make monosynaptic connections. The latter feature explains the multisystem degeneration that characterises ALS. Consideration of ALS as a primary neurodegenerative disorder of the human brain may incorporate concepts of prion-like spread at synaptic terminals of corticofugal axons. Further, such a concept could explain the recognised widespread imaging abnormalities of the ALS neocortex and the accepted relationship between ALS and frontotemporal dementia.

Disease-modifying and symptomatic treatment of amyotrophic lateral sclerosis

In this review, we summarize the most important recent developments in the treatment of amyotrophic lateral sclerosis (ALS). In terms of disease-modifying treatment options, several drugs such as dexpramipexole, pioglitazone, lithium, and many others have been tested in large multicenter trials, albeit with disappointing results. Therefore, riluzole remains the only directly disease-modifying drug. In addition, we discuss antisense oligonucleotides (ASOs) as a new and potentially causal treatment option. Progress in symptomatic treatments has been more important. Nutrition and ventilation are now an important focus of ALS therapy. Several studies have firmly established that noninvasive ventilation improves patients' quality of life and prolongs survival. On the other hand, there is still no consensus regarding best nutritional management, but big multicenter trials addressing this issue are currently ongoing. Evidence regarding secondary symptoms like spasticity, muscle cramps or sialorrhea remains generally scarce, but some new insights will also be discussed. Growing evidence suggests that multidisciplinary care in specialized clinics improves survival.

Regional microstructural damage and patterns of eye movement impairment: a DTI and video-oculography study in neurodegenerative parkinsonian syndromes

Characteristic alterations of eye movement control are a common feature of neurodegenerative parkinsonism, including Parkinson's disease (PD), progressive supranuclear palsy (PSP), and multiple system atrophy (MSA). Regional microstructural alterations as assessed by diffusion tensor imaging (DTI) have been reported in PD, PSP, and MSA. Therefore, we investigated the specific association between eye movement disturbances and microstructural impairment in these diseases. Video-oculographic recordings of smooth pursuit and visually guided reactive saccades as well as fractional anisotropy (FA) maps computed from whole-brain DTI data were analyzed for 36 PD, 30 PSP, 18 MSA patients, and 23 matched healthy control subjects. In PSP, peak eye velocity was pathologically slowed compared to controls (p < 0.001) and correlated significantly with microstructural impairment in the midbrain (p < 0.001, corrected). Smooth pursuit eye movements were substantially disturbed in MSA mainly by characteristic 'catch-up' saccades resulting in significantly reduced pursuit gain (p < 0.001, corrected), and the shape of saccadized pursuit in MSA was significantly correlated with FA reductions in the middle cerebral peduncle (p < 0.001, FDR corrected). The prevalence of saccadic intrusions as a measure for inhibitory control was significantly increased in PD compared with controls (p < 0.001), but was uncorrelated with FA in cortical and subcortical white matter. Eye movement disturbances in PSP and MSA-but not in PD-are associated with diagnosis-specific regional microstructural alterations in the white matter. The non-invasive quantified oculomotor function analysis can give clues to the underlying structural connectivity network pathology and underpins its role as a technical marker in PSP and MSA.

Intrinsic functional connectivity alterations in progressive supranuclear palsy: Differential effects in frontal cortex, motor, and midbrain networks

BACKGROUND

The topography of functional network changes in progressive supranuclear palsy can be mapped by intrinsic functional connectivity MRI. The objective of this study was to study functional connectivity and its clinical and behavioral correlates in dedicated networks comprising the cognition-related default mode and the motor and midbrain functional networks in patients with PSP.

METHODS

Whole-brain-based "resting-state" functional MRI and high-resolution T1-weighted magnetic resonance imaging data together with neuropsychological and video-oculographic data from 34 PSP patients (22 with Richardson subtype and 12 with parkinsonian subtype) and 35 matched healthy controls were subjected to network-based functional connectivity and voxel-based morphometry analysis.

RESULTS

After correction for global patterns of brain atrophy, the group comparison between PSP patients and controls revealed significantly decreased functional connectivity (P < 0.05, corrected) in the prefrontal cortex, which was significantly correlated with cognitive performance (P = 0.006). Of note, midbrain network connectivity in PSP patients showed increased connectivity with the thalamus, on the one hand, whereas, on the other hand, lower functional connectivity within the midbrain was significantly correlated with vertical gaze impairment, as quantified by video-oculography (P = 0.004). PSP Richardson subtype showed significantly increased functional motor network connectivity with the medial prefrontal gyrus.

CONCLUSIONS

PSP-associated neurodegeneration was attributed to both decreased and increased functional connectivity. Decreasing functional connectivity was associated with worse behavioral performance (ie, dementia severity and gaze palsy), whereas the pattern of increased functional connectivity may be a potential adaptive mechanism. © 2017 International Parkinson and Movement Disorder Society.

Patterns of Eye Movement Impairment Correlate with Regional Brain Atrophy in Neurodegenerative Parkinsonism

BACKGROUND

One common feature of neurodegenerative parkinsonism including Parkinson's disease (PD), multisystem atrophy (MSA), and progressive supranuclear palsy (PSP) is altered eye movement control. Characteristic regional structural atrophy patterns in MRI can be observed in PD, MSA, and PSP.

OBJECTIVE

To investigate the association between eye movement disturbances and regional brain atrophy in patients with PD, MSA, and PSP.

METHODS

High-resolution 3-dimensional T1-weighted MRI images and video-oculographic recordings (EyeLink®) were obtained from 39 PD, 32 PSP, and 18 MSA patients and 24 matched healthy control subjects. Automatic regional volumetric assessment was performed using atlas-based volumetry (ABV).

RESULTS

The prevalence of saccadic intrusions as a measure of inhibitory control was significantly increased in PD patients compared to controls (p < 0.001) and negatively correlated with whole brain volume, cerebral brain volume, and occipital lobe volume (p = 0.0057, p = 0.0049, and p = 0.0059, respectively; all p values are false discovery rate corrected). In MSA, smooth pursuit was disturbed by characteristic "catch-up" saccades (p < 0.001) and it was significantly correlated with cerebellar volume (p = 0.004) and pontine volume (p < 0.001). The hallmark of PSP was pathologically slowed vertical peak eye velocities (p < 0.001); the lower the peak eye velocity, the more marked midbrain atrophy (p = 0.007).

CONCLUSIONS

Foci of regional atrophy correlated with disease-specific eye movement alterations in all investigated parkinsonian syndromes. Oculomotor impairment in PD, predominantly the result of executive dysfunction, was linked to cerebral atrophy. Impairment in the corresponding oculomotor pathways was associated with atrophy of pontocerebellar oculomotor structures in MSA and midbrain atrophy in PSP.

An eye-tracking controlled neuropsychological battery for cognitive assessment in neurological diseases

Traditional cognitive assessment in neurological conditions involving physical disability is often prevented by the presence of verbal-motor impairment; to date, an extensive motor-verbal-free neuropsychological battery is not available for such purposes. We adapted a set of neuropsychological tests, assessing language, attentional abilities, executive functions and social cognition, for eye-tracking (ET) control, and explored its feasibility in a sample of healthy participants. Thirty healthy subjects performed a neuropsychological assessment, using an ET-based neuropsychological battery, together with standard "paper and pencil" cognitive measures for frontal (Frontal Assessment Battery-FAB) and working memory abilities (Digit Sequencing Task) and for global cognitive efficiency (Montreal Cognitive Assessment-MoCA). Psychological measures of anxiety (State-Trait Anxiety Inventory-Y-STAI-Y) and depression (Beck Depression Inventory-BDI) were also collected, and a usability questionnaire was administered. Significant correlations were observed between the "paper and pencil" screening of working memory abilities and the ET-based neuropsychological measures. The ET-based battery also correlated with the MoCA, while poor correlations were observed with the FAB. Usability aspects were found to be influenced by both working memory abilities and psychological components. The ET-based neuropsychological battery developed could provide an extensive assessment of cognitive functions, allowing participants to perform tasks independently from the integrity of motor or verbal channels. Further studies will be aimed at investigating validity and usability components in neurological populations with motor-verbal impairments.

Functional connectivity changes resemble patterns of pTDP-43 pathology in amyotrophic lateral sclerosis

‘Resting-state’ fMRI allows investigation of alterations in functional brain organization that are associated with an underlying pathological process. We determine whether abnormal connectivity in amyotrophic lateral sclerosis (ALS) in a priori-defined intrinsic functional connectivity networks, according to a neuropathological staging scheme and its DTI-based tract correlates, permits recognition of a sequential involvement of functional networks. ‘Resting-state’ fMRI data from 135 ALS patients and 56 matched healthy controls were investigated for the motor network (corresponding to neuropathological stage 1), brainstem (stage 2), ventral attention (stage 3), default mode/hippocampal network (stage 4), and primary visual network (as the control network) in a cross-sectional analysis and longitudinally in a subgroup of 27 patients after 6 months. Group comparison from cross-sectional and longitudinal data revealed significantly increased functional connectivity (p < 0.05, corrected) in all four investigated networks (but not in the control network), presenting as a network expansion that was correlated with physical disability. Increased connectivity of functional networks, as investigated in a hypothesis-driven approach, is characterized by network expansions and resembled the pattern of pTDP-43 pathology in ALS. However, our data did not allow for the recognition of a sequential involvement of functional connectivity networks at the individual level.

Eye-Tracking Control to Assess Cognitive Functions in Patients with Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder with pathological involvement of upper and lower motoneurons, subsequently leading to progressive loss of motor and speech abilities. In addition, cognitive functions are impaired in a subset of patients. To evaluate these potential deficits in severely physically impaired ALS patients, eye-tracking is a promising means to conduct cognitive tests. The present article focuses on how eye movements, an indirect means of communication for physically disabled patients, can be utilized to allow for detailed neuropsychological assessment. The requirements, in terms of oculomotor parameters that have to be met for sufficient eye-tracking in ALS patients are presented. The properties of stimuli, including type of neuropsychological tests and style of presentation, best suited to successfully assess cognitive functioning, are also described. Furthermore, recommendations regarding procedural requirements are provided. Overall, this methodology provides a reliable, easy to administer and fast approach for assessing cognitive deficits in patients who are unable to speak or write such as patients with severe ALS. The only confounding factor might be deficits in voluntary eye movement control in a subset of ALS patients.