Eye movements in amyotrophic lateral sclerosis and its mimics: a review with illustrative cases

Supra- and infra-tentorial degeneration patterns in primary lateral sclerosis: a multimodal longitudinal neuroradiology study

BACKGROUND

Primary lateral sclerosis (PLS) is traditionally solely associated with progressive upper motor neuron dysfunction manifesting in limb spasticity, gait impairment, bulbar symptoms and pseudobulbar affect. Recent studies have described frontotemporal dysfunction in some patients resulting in cognitive manifestations. Cerebellar pathology is much less well characterised despite sporadic reports of cerebellar disease.

METHODS

A multi-timepoint, longitudinal neuroimaging study was conducted to characterise the evolution of both intra-cerebellar disease burden and cerebro-cerebellar connectivity. The volumes of deep cerebellar nuclei, cerebellar cortical volumes, cerebro-cerebellar structural and functional connectivity were assessed longitudinally in a cohort of 43 individuals with PLS.

RESULTS

Cerebello-frontal, -temporal, -parietal, -occipital and cerebello-thalamic structural disconnection was detected at baseline based on radial diffusivity (RD) and cerebello-frontal decoupling was also evident based on fractional anisotropy (FA) alterations. Functional connectivity changes were also detected in cerebello-frontal, parietal and occipital projections. Volume reductions were identified in the vermis, anterior lobe, posterior lobe, and crura. Among the deep cerebellar nuclei, the dorsal dentate was atrophic. Longitudinal follow-up did not capture statistically significant progressive changes. Significant primary motor cortex atrophy and inter-hemispheric transcallosal degeneration were also captured.

CONCLUSIONS

PLS is not only associated with upper motor neuron dysfunction, but cerebellar cortical volume loss and deep cerebellar nuclear atrophy can also be readily detected. In addition to intra-cerebellar disease burden, cerebro-cerebellar connectivity alterations also take place. Our data add to the evolving evidence of widespread neurodegeneration in PLS beyond the primary motor regions. Cerebellar dysfunction in PLS is likely to exacerbate bulbar, gait and dexterity impairment and contribute to pseudobulbar affect.

Downbeat nystagmus: a clinical and pathophysiological review

Downbeat nystagmus (DBN) is a neuro-otological finding frequently encountered by clinicians dealing with patients with vertigo. Since DBN is a finding that should be understood because of central vestibular dysfunction, it is necessary to know how to frame it promptly to suggest the correct diagnostic-therapeutic pathway to the patient. As knowledge of its pathophysiology has progressed, the importance of this clinical sign has been increasingly understood. At the same time, clinical diagnostic knowledge has increased, and it has been recognized that this sign may occur sporadically or in association with others within defined clinical syndromes. Thus, in many cases, different therapeutic solutions have become possible. In our work, we have attempted to systematize current knowledge about the origin of this finding, the clinical presentation and current treatment options, to provide an overview that can be used at different levels, from the general practitioner to the specialist neurologist or neurotologist.

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.

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.

Saccadic oscillations as a biomarker of clinical symptoms in amyotrophic lateral sclerosis

BACKGROUND

Among eye movements in amyotrophic lateral sclerosis (ALS), we identified the characteristics of square-wave jerks (SWJs) seen during times without visual fixation (VF) and analyzed their relationships with clinical parameters.

MATERIALS AND METHODS

Clinical symptoms were evaluated and eye movements were tested using electronystagmography in 15 patients with ALS (10 men, 5 women; mean age, 66.9 ± 10.5 years). SWJs with and without VF were recorded, and their characteristics were identified. Relationships between each SWJ parameter and clinical symptoms were evaluated. Results were compared with eye movement data from 18 healthy individuals.

RESULTS

The frequency of SWJs without VF was significantly higher in the ALS group than in the healthy group (P < 0.001). When the condition was changed from VF to no-VF in the ALS group, the frequency of SWJs was significantly higher in healthy subjects (P = 0.004). A positive correlation was seen between frequency of SWJs and percentage predicted forced vital capacity (%FVC) (R = 0.546, P = 0.035).

CONCLUSION

The frequency of SWJs was higher with VF in healthy people, and was suppressed without VF. In contrast, the frequency of SWJs was not suppressed without VF in ALS patients. This suggests that SWJs without VF have some clinical significance in ALS patients. Moreover, a relationship was noted between the parameters of SWJs without VF in ALS patients and results of pulmonary function tests, suggesting that SWJs during times without VF may offer a clinical parameter of ALS.

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.

Oculomotor Dysfunction in Motor Neuron Disease

INTRODUCTION

Though eye movements are relatively spared in motor neuron disease (MND), recent literature suggests patients may exhibit oculomotor dysfunction (OD). Frontal lobe involvement has been postulated based on oculomotor pathway anatomy and clinical overlap of amyotrophic lateral sclerosis (ALS) with frontotemporal dementia. We examined oculomotor characteristics in patients with MND presenting to an ALS Center, hypothesizing that patients with prominent upper motor neuron involvement or pseudobulbar affect (PBA) may demonstrate greater OD.

METHODS

This was a single-center prospective observational study. Patients with diagnosis of MND were examined at bedside. Center for Neurologic Study-Liability Scale (CNS-LS) was administered to screen for pseudobulbar affect. Primary outcome was OD and the secondary outcome was the association between presence of OD in patients with MND experiencing symptoms of PBA or upper motor neuron dysfunction. Wilcoxon rank-sum scores and Fisher's exact tests were used to perform statistical analyses.

RESULTS

53 patients with MND underwent the clinical ophthalmic evaluation. On bedside examination, 34 patients (64.2%) presented with OD. There were no significant associations between locations of MND at presentation and the presence or type of OD. OD was associated with increased disease severity as measured by reduced FVC (p = 0.02). There was no significant association between OD and CNS-LS (p = 0.2).

DISCUSSION

Though our study did not find a significant association between OD and upper versus lower MND at presentation, OD may be useful as an additional clinical marker for advanced disease.

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.

Towards clinical application of implantable brain-computer interfaces for people with late-stage ALS: medical and ethical considerations

Individuals with amyotrophic lateral sclerosis (ALS) frequently develop speech and communication problems in the course of their disease. Currently available augmentative and alternative communication technologies do not present a solution for many people with advanced ALS, because these devices depend on residual and reliable motor activity. Brain-computer interfaces (BCIs) use neural signals for computer control and may allow people with late-stage ALS to communicate even when conventional technology falls short. Recent years have witnessed fast progression in the development and validation of implanted BCIs, which place neural signal recording electrodes in or on the cortex. Eventual widespread clinical application of implanted BCIs as an assistive communication technology for people with ALS will have significant consequences for their daily life, as well as for the clinical management of the disease, among others because of the potential interaction between the BCI and other procedures people with ALS undergo, such as tracheostomy. This article aims to facilitate responsible real-world implementation of implanted BCIs. We review the state of the art of research on implanted BCIs for communication, as well as the medical and ethical implications of the clinical application of this technology. We conclude that the contribution of all BCI stakeholders, including clinicians of the various ALS-related disciplines, will be needed to develop procedures for, and shape the process of, the responsible clinical application of implanted BCIs.

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.

Gaze-Contingent Eye-Tracking Training in Brain Disorders: A Systematic Review

Eye movement abnormalities in association with cognitive and emotional deficits have been described in neurological, neurodevelopmental, and psychiatric disorders. Eye-Tracking (ET) techniques could therefore enhance cognitive interventions by contingently providing feedback to patients. Since no consensus has been reached thus far on this approach, this study aimed at systematically reviewing the current evidence. This review was performed and reported according to PRISMA guidelines. Records were searched for in PubMed, Web of Science, and Scopus (1990–2021) through the following string: (‘Eye Tracking’ OR ‘Eye-Tracking’ OR ‘Oculomotor’) AND (‘Neuropsychol*’ OR ‘Cognitive’) AND (‘Rehabilitation’ OR ‘Training’ OR ‘Stimulation’). Study outcomes were thematically classified and qualitatively synthesized. A structured quality assessment was performed. A total of 24 articles were included, addressing neurodevelopmental (preterm infants and children with autism spectrum disorder, Rett syndrome, or ADHD; N = 14), psychiatric (mood and anxiety disorders or alcohol dependence; N = 7), and neurological conditions (stroke; N = 3). Overall, ET gaze-contingent training proved to be effective in improving cognitive and emotional alterations. However, population heterogeneity limits the generalizability of results. ET gaze-contingent protocols allow researchers to directly and dynamically train attentional functions; together with the recruitment of implicit, “bottom-up” strategies, these protocols are promising and possibly integrable with traditional cognitive approaches.

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.

Cerebellar degeneration in primary lateral sclerosis: an under-recognized facet of PLS

While primary lateral sclerosis (PLS) has traditionally been regarded as a pure upper motor neuron disorder, recent clinical, neuroimaging and postmortem studies have confirmed significant extra-motor involvement. Sporadic reports have indicated that in addition to the motor cortex and corticospinal tracts, the cerebellum may also be affected in PLS. Cerebellar manifestations are difficult to ascertain in PLS as the clinical picture is dominated by widespread upper motor neuron signs. The likely contribution of cerebellar dysfunction to gait disturbance, falls, pseudobulbar affect and dysarthria may be overlooked in the context of progressive spasticity. The objective of this study is the comprehensive characterization of cerebellar gray and white matter degeneration in PLS using multiparametric quantitative neuroimaging methods to systematically evaluate each cerebellar lobule and peduncle. Forty-two patients with PLS and 117 demographically-matched healthy controls were enrolled in a prospective MRI study. Complementary volumetric and voxelwise analyses revealed focal cerebellar alterations instead of global cerebellar atrophy. Bilateral gray matter volume reductions were observed in lobules III, IV and VIIb. Significant diffusivity alterations within the superior cerebellar peduncle indicate disruption of the main cerebellar outflow tracts. These findings suggest that the considerable intra-cerebellar disease-burden is coupled with concomitant cerebro-cerebellar connectivity disruptions. While cerebellar dysfunction is challenging to demonstrate clinically, cerebellar pathology is likely to be a significant contributor to disability in PLS.

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.

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.

Brain-computer interfaces for communication

Locked-in syndrome (LIS) is characterized by an inability to move or speak in the presence of intact cognition and can be caused by brainstem trauma or neuromuscular disease. Quality of life (QoL) in LIS is strongly impaired by the inability to communicate, which cannot always be remedied by traditional augmentative and alternative communication (AAC) solutions if residual muscle activity is insufficient to control the AAC device. Brain-computer interfaces (BCIs) may offer a solution by employing the person's neural signals instead of relying on muscle activity. Here, we review the latest communication BCI research using noninvasive signal acquisition approaches (electroencephalography, functional magnetic resonance imaging, functional near-infrared spectroscopy) and subdural and intracortical implanted electrodes, and we discuss current efforts to translate research knowledge into usable BCI-enabled communication solutions that aim to improve the QoL of individuals with LIS.

Functional neuroanatomy of the human eye movement network: a review and atlas

The human eye movement network is a complex system that requires the integration of sensory, motor, attentional, and executive processes. Here, we review the neuroanatomy of the eye movement network with an emphasis on functional neuroimaging applications. We consolidate the literature into a concise resource designed to be immediately accessible and applicable to diverse research interests, and present the novel Functional Oculomotor System (FOcuS) Atlas-a tool in stereotaxic space that will simplify and standardize the inclusion of the eye movement network in future functional neuroimaging studies. We anticipate this review and the FOcuS Atlas will facilitate increased examination of the eye movement network across disciplines leading to a thorough understanding of how eye movement network function contributes to higher-order cognition and how it is integrated with other brain networks. Furthermore, functional examination of the eye movement network in patient populations offers the potential for deeper insight into the role of eye movement circuitry in functional network activity, diagnostic assessments, and the indications for augmentative communication systems that rely on eye movement control.

Motor Neuron Susceptibility in ALS/FTD

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease characterized by the death of both upper and lower motor neurons (MNs) in the brain, brainstem and spinal cord. The neurodegenerative mechanisms leading to MN loss in ALS are not fully understood. Importantly, the reasons why MNs are specifically targeted in this disorder are unclear, when the proteins associated genetically or pathologically with ALS are expressed ubiquitously. Furthermore, MNs themselves are not affected equally; specific MNs subpopulations are more susceptible than others in both animal models and human patients. Corticospinal MNs and lower somatic MNs, which innervate voluntary muscles, degenerate more readily than specific subgroups of lower MNs, which remain resistant to degeneration, reflecting the clinical manifestations of ALS. In this review, we discuss the possible factors intrinsic to MNs that render them uniquely susceptible to neurodegeneration in ALS. We also speculate why some MN subpopulations are more vulnerable than others, focusing on both their molecular and physiological properties. Finally, we review the anatomical network and neuronal microenvironment as determinants of MN subtype vulnerability and hence the progression of ALS.

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.

An ERP-based BCI with peripheral stimuli: validation with ALS patients

Many studies reported that ERP-based BCIs can provide communication for some people with amyotrophic lateral sclerosis (ALS). ERP-based BCIs often present characters within a matrix that occupies the center of the visual field. However, several studies have identified some concerns with the matrix-based approach. This approach may lead to fatigue and errors resulting from flashing adjacent stimuli, and is impractical for users who might want to use the BCI in tandem with other software or feedback in the center of the monitor. In this paper, we introduce and validate an alternate ERP-based BCI display approach. By presenting stimuli near the periphery of the display, we reduce the adjacency problem and leave the center of the display available for feedback or other applications. Two ERP-based display approaches were tested on 18 ALS patients to: (1) compare performance between a conventional matrix speller paradigm (Matrix-P, mean visual angle 6°) and a new speller paradigm with peripherally distributed stimuli (Peripheral-P, mean visual angle 8.8°); and (2) assess performance while spelling 42 characters online continuously, without a break. In the Peripheral-P condition, 12 subjects attained higher than 80% feedback accuracy during online performance, and 7 of these subjects obtained higher than 90% accuracy. The experimental results showed that the Peripheral-P condition yielded performance comparable to the conventional Matrix-P condition (p > 0.05) in accuracy and information transfer rate. This paper introduces a new display approach that leaves the center of the monitor open for feedback and/or other display elements, such as movies, games, art, or displays from other AAC software or conventional software tools.

A Human⁻Machine Interface Based on Eye Tracking for Controlling and Monitoring a Smart Home Using the Internet of Things

People with severe disabilities may have difficulties when interacting with their home devices due to the limitations inherent to their disability. Simple home activities may even be impossible for this group of people. Although much work has been devoted to proposing new assistive technologies to improve the lives of people with disabilities, some studies have found that the abandonment of such technologies is quite high. This work presents a new assistive system based on eye tracking for controlling and monitoring a smart home, based on the Internet of Things, which was developed following concepts of user-centered design and usability. With this system, a person with severe disabilities was able to control everyday equipment in her residence, such as lamps, television, fan, and radio. In addition, her caregiver was able to monitor remotely, by Internet, her use of the system in real time. Additionally, the user interface developed here has some functionalities that allowed improving the usability of the system as a whole. The experiments were divided into two steps. In the first step, the assistive system was assembled in an actual home where tests were conducted with 29 participants without disabilities. In the second step, the system was tested with online monitoring for seven days by a person with severe disability (end-user), in her own home, not only to increase convenience and comfort, but also so that the system could be tested where it would in fact be used. At the end of both steps, all the participants answered the System Usability Scale (SUS) questionnaire, which showed that both the group of participants without disabilities and the person with severe disabilities evaluated the assistive system with mean scores of 89.9 and 92.5, respectively.

Effects of simulated visual acuity and ocular motility impairments on SSVEP brain-computer interface performance: An experiment with Shuffle Speller

Individuals with severe speech and physical impairments may have concomitant visual acuity impairments (VAI) or ocular motility impairments (OMI) impacting visual BCI use. We report on the use of the Shuffle Speller typing interface for an SSVEP BCI copy-spelling task under three conditions: simulated VAI, simulated OMI, and unimpaired vision. To mitigate the effect of visual impairments, we introduce a method that adaptively selects a user-specific trial length to maximize expected information transfer rate (ITR); expected ITR is shown to closely approximate the rate of correct letter selections. All participants could type under the unimpaired and simulated VAI conditions, with no significant differences in typing accuracy or speed. Most participants (31 of 37) could not type under the simulated OMI condition; some achieved high accuracy but with slower typing speeds. Reported workload and discomfort were low, and satisfaction high, under the unimpaired and simulated VAI conditions. Implications and future directions to examine effect of visual impairment on BCI use is discussed.

Progressive spasticity, supranuclear gaze palsy and postural instability, without parkinsonism: what's in a phenotype?

We present a series of patients with vertical supranuclear gaze palsy, postural instability with falls, and progressive spasticity, who mimic Progressive Supranuclear Palsy - Richardson's syndrome (PSP-R) but have no parkinsonism, and in whom dopamine transporter imaging is normal. We suggest possible aetiologies for this constellation of symptoms, discuss the possible origin of these signs and highlight this phenotype as it may mimic atypical parkinsonism and in particular PSP.

Abnormal Oculomotor Functions in Amyotrophic Lateral Sclerosis

BACKGROUND AND PURPOSE

Although traditionally regarded as spared, a range of oculomotor dysfunction has been recognized in amyotrophic lateral sclerosis (ALS) patients. ALS is nowadays considered as a neurodegenerative disorder of a third compartment comprising widespread areas of extra-motor brain including cerebellum. Our objective was to perform an observational study to examine for ocular motor dysfunction in patients with ALS and for any differences between bulbar-onset and spinal-onset patients.

METHODS

Thirty two ALS patients (bulbar onset: 10, spinal onset: 22) underwent the standardized systemic evaluations using video-oculography.

RESULTS

Oculomotor dysfunctions such as square wave jerks, saccadic dysmetria, abnormal cogwheeling smooth pursuits and head shaking and positional nystagmus of central origin have been observed in the ALS patients at a relatively early stage. Abnormal smooth pursuits and saccadic dysmetria were increased in the bulbar-onset compared to the spinal-onset (p<0.05).

CONCLUSIONS

These oculomotor abnormalities may be a marker of neuro-degeneration beyond motor neurons in ALS, especially in bulbar-onset disease. Future longitudinal studies of eye movement abnormalities have provided insights into the distribution and nature of the disease process.

Development of an electrooculogram-based human-computer interface using involuntary eye movement by spatially rotating sound for communication of locked-in patients

Individuals who have lost normal pathways for communication need augmentative and alternative communication (AAC) devices. In this study, we propose a new electrooculogram (EOG)-based human-computer interface (HCI) paradigm for AAC that does not require a user’s voluntary eye movement for binary yes/no communication by patients in locked-in state (LIS). The proposed HCI uses a horizontal EOG elicited by involuntary auditory oculogyric reflex, in response to a rotating sound source. In the proposed HCI paradigm, a user was asked to selectively attend to one of two sound sources rotating in directions opposite to each other, based on the user’s intention. The user’s intentions could then be recognised by quantifying EOGs. To validate its performance, a series of experiments was conducted with ten healthy subjects, and two patients with amyotrophic lateral sclerosis (ALS). The online experimental results exhibited high-classification accuracies of 94% in both healthy subjects and ALS patients in cases where decisions were made every six seconds. The ALS patients also participated in a practical yes/no communication experiment with 26 or 30 questions with known answers. The accuracy of the experiments with questionnaires was 94%, demonstrating that our paradigm could constitute an auxiliary AAC system for some LIS patients.

Eye Tracking Based Control System for Natural Human-Computer Interaction

Eye movement can be regarded as a pivotal real-time input medium for human-computer communication, which is especially important for people with physical disability. In order to improve the reliability, mobility, and usability of eye tracking technique in user-computer dialogue, a novel eye control system with integrating both mouse and keyboard functions is proposed in this paper. The proposed system focuses on providing a simple and convenient interactive mode by only using user's eye. The usage flow of the proposed system is designed to perfectly follow human natural habits. Additionally, a magnifier module is proposed to allow the accurate operation. In the experiment, two interactive tasks with different difficulty (searching article and browsing multimedia web) were done to compare the proposed eye control tool with an existing system. The Technology Acceptance Model (TAM) measures are used to evaluate the perceived effectiveness of our system. It is demonstrated that the proposed system is very effective with regard to usability and interface design.

EEG-Based Brain-Computer Interfaces for Communication and Rehabilitation of People with Motor Impairment: A Novel Approach of the 21 st Century

People with severe neurological impairments face many challenges in sensorimotor functions and communication with the environment; therefore they have increased demand for advanced, adaptive and personalized rehabilitation. During the last several decades, numerous studies have developed brain-computer interfaces (BCIs) with the goals ranging from providing means of communication to functional rehabilitation. Here we review the research on non-invasive, electroencephalography (EEG)-based BCI systems for communication and rehabilitation. We focus on the approaches intended to help severely paralyzed and locked-in patients regain communication using three different BCI modalities: slow cortical potentials, sensorimotor rhythms and P300 potentials, as operational mechanisms. We also review BCI systems for restoration of motor function in patients with spinal cord injury and chronic stroke. We discuss the advantages and limitations of these approaches and the challenges that need to be addressed in the future.

Brain-Computer Interface for Clinical Purposes: Cognitive Assessment and Rehabilitation

Alongside the best-known applications of brain-computer interface (BCI) technology for restoring communication abilities and controlling external devices, we present the state of the art of BCI use for cognitive assessment and training purposes. We first describe some preliminary attempts to develop verbal-motor free BCI-based tests for evaluating specific or multiple cognitive domains in patients with Amyotrophic Lateral Sclerosis, disorders of consciousness, and other neurological diseases. Then we present the more heterogeneous and advanced field of BCI-based cognitive training, which has its roots in the context of neurofeedback therapy and addresses patients with neurological developmental disorders (autism spectrum disorder and attention-deficit/hyperactivity disorder), stroke patients, and elderly subjects. We discuss some advantages of BCI for both assessment and training purposes, the former concerning the possibility of longitudinally and reliably evaluating cognitive functions in patients with severe motor disabilities, the latter regarding the possibility of enhancing patients' motivation and engagement for improving neural plasticity. Finally, we discuss some present and future challenges in the BCI use for the described purposes.

Clinical Spectrum of Amyotrophic Lateral Sclerosis (ALS)

Amyotrophic lateral sclerosis (ALS) is primarily characterized by progressive loss of motor neurons, although there is marked phenotypic heterogeneity between cases. Typical, or "classical," ALS is associated with simultaneous upper motor neuron (UMN) and lower motor neuron (LMN) involvement at disease onset, whereas atypical forms, such as primary lateral sclerosis and progressive muscular atrophy, have early and predominant involvement in the UMN and LMN, respectively. The varying phenotypes can be so distinctive that they would seem to have differing biology. Because the same phenotypes can have multiple causes, including different gene mutations, there may be multiple molecular mechanisms causing ALS, implying that the disease is a syndrome. Conversely, multiple phenotypes can be caused by a single gene mutation; thus, a single molecular mechanism could be compatible with clinical heterogeneity. The pathogenic mechanism(s) in ALS remain unknown, but active propagation of the pathology neuroanatomically is likely a primary component.

Fusion of P300 and eye-tracker data for spelling using BCI2000

OBJECTIVE

Various augmentative and alternative communication (AAC) devices have been developed in order to aid communication for individuals with communication disorders. Recently, there has been interest in combining EEG data and eye-gaze data with the goal of developing a hybrid (or 'fused') BCI (hBCI) AAC system. This work explores the effectiveness of a speller that fuses data from an eye-tracker and the P300 speller in order to create a hybrid P300 speller.

APPROACH

This hybrid speller collects both eye-tracking and EEG data in parallel, and the user spells characters on the screen in the same way that they would if they were only using the P300 speller. Online and offline experiments were performed. The online experiments measured the performance of the speller for sixteen non-disabled participants, while the offline simulations were used to assess the robustness of the hybrid system.

MAIN RESULTS

Online results showed that for fifteen non-disabled participants, using eye-gaze in a Bayesian framework with EEG data from the P300 speller improved accuracy ([Formula: see text], [Formula: see text], [Formula: see text] for estimated, medium and high variance configurations) and reduced the average number of flashes required to spell a character compared to the standard P300 speller that relies solely on EEG data ([Formula: see text], [Formula: see text], [Formula: see text] for estimated, medium and high variance configurations). Offline simulations indicate that the system provides more robust performance than a standalone eye gaze system.

SIGNIFICANCE

The results of this work on non-disabled participants shows the potential efficacy of hybrid P300 and eye-tracker speller. Further validation on the amyotrophic lateral sceloris population is needed to assess the benefit of this hybrid system.

Finger extension weakness and downbeat nystagmus motor neuron disease syndrome: A novel motor neuron disorder?

Introduction: Disturbances of eye movements are infrequently encountered in motor neuron diseases (MNDs) or motor neuropathies, and there is no known syndrome that combines progressive muscle weakness with downbeat nystagmus. Methods: To describe the core clinical features of a syndrome of MND associated with downbeat nystagmus, clinical features were collected from 6 patients. Results: All patients had slowly progressive muscle weakness and wasting in combination with downbeat nystagmus, which was clinically most obvious in downward and lateral gaze. Onset was in the second to fourth decade with finger extension weakness, progressing to other distal and sometimes more proximal muscles. Visual complaints were not always present. Electrodiagnostic testing showed signs of regional motor axonal loss in all patients. Discussion: The etiology of this syndrome remains elusive. Because finger extension weakness and downbeat nystagmus are the discriminating clinical features of this MND, we propose the name FEWDON‐MND syndrome. Muscle Nerve56: 1164–1168, 2017

Extra-motor abnormalities in amyotrophic lateral sclerosis: another layer of heterogeneity

INTRODUCTION

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disease defined by the presence of muscle weakness. The motor features of disease are heterogeneous in site of onset and progression. There are also extra-motor features in some patients. The genetic basis for extra-motor features is uncertain. The heterogeneity of ALS is an issue for clinical trials. Areas covered: This paper reviews the range and prevalence of extra-motor features associated with ALS, and highlights the current information about genetic associations with extra-motor features. Expert commentary: There are extra-motor features of ALS, but these are not found in all patients. The most common is cognitive abnormality. More data is required to ascertain whether extra-motor features arise with progression of disease. Extra-motor features are reported in patients with a range of causative genetic mutations, but are not found in all patients with these mutations. Further studies are required of the heterogeneity of ALS, and genotype/phenotype correlations are required, taking note of extra-motor features.

Basic and translational neuro-ophthalmology of visually guided saccades: disorders of velocity

Introduction

Saccades are rapid, yoked eye movements in an effort to direct a target over fovea. The complex circuitry of saccadic eye movements has been exhaustively described. As a result clinicians can elegantly localize the pathology if it falls on the neuraxis responsible for saccades. Traditionally saccades are studied with their quantitative characteristics such as amplitude, velocity, duration, direction, latency and accuracy.

Areas covered

Amongst all subtypes, the physiology of the visually guided saccades is most extensively studied. Here we will review the basic and pertinent neuro-anatomy and physiology of visually guided saccade and then discuss common or classic disorders affecting the velocity of visually guided saccades. We will then discuss the basic mechanism for saccade slowing in these disorders.

Expert commentary

Prompt appreciation of disorders of saccade velocity is critical to reach appropriate diagnosis. Disorders of midbrain, cerebellum, or basal ganglia can lead to prolonged transition time during gaze shift and decreased saccade velocity.

Self-regulation of brain rhythms in the precuneus: a novel BCI paradigm for patients with ALS

OBJECTIVE

Electroencephalographic (EEG) brain-computer interfaces (BCIs) hold promise in restoring communication for patients with completely locked-in stage amyotrophic lateral sclerosis (ALS). However, these patients cannot use existing EEG-based BCIs, arguably because such systems rely on brain processes that are impaired in the late stages of ALS. In this work, we introduce a novel BCI designed for patients in late stages of ALS based on high-level cognitive processes that are less likely to be affected by ALS.

APPROACH

We trained two ALS patients via EEG-based neurofeedback to use self-regulation of theta or gamma oscillations in the precuneus for basic communication. Because there is a tight connection between the precuneus and consciousness, precuneus oscillations are arguably generated by high-level cognitive processes, which are less likely to be affected by ALS than processes linked to the peripheral nervous system.

MAIN RESULTS

Both patients learned to self-regulate their precuneus oscillations and achieved stable online decoding accuracy over the course of disease progression. One patient achieved a mean online decoding accuracy in a binary decision task of 70.55% across 26 training sessions, and the other patient achieved 59.44% across 16 training sessions. We provide empirical evidence that these oscillations were cortical in nature and originated from the intersection of the precuneus, cuneus, and posterior cingulate.

SIGNIFICANCE

Our results establish that ALS patients can employ self-regulation of precuneus oscillations for communication. Such a BCI is likely to be available to ALS patients as long as their consciousness supports communication.

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.

Clinical characteristics and course of dying in patients with amyotrophic lateral sclerosis withdrawing from long-term ventilation

Non-invasive ventilation (NIV) or tracheotomy with invasive ventilation (TIV) are treatment options in ALS. However, a proportion of patients receiving long-term ventilation decide to have it withdrawn. The objective of this study was to analyse the clinical characteristics and palliative approaches in ALS patients withdrawing from long-term ventilation (WLTV). In a cohort study, two different palliative concepts in WLTV were studied: (1) augmented symptom control (ASC; sedation not intended) in patients with ventilator-free tolerance; (2) continuous deep sedation (CDS; sedation intended) in patients without ventilator-free tolerance. Results showed that WLTV was realised in 49 ALS patients (NIV = 13; TIV = 36). Mean daily ventilation was 23.4 h. The ALS Functional Rating Scale (ALSFRS-R) was low (5.6 of 48). Forty-one per cent of patients (n = 20) presented with ophthalmoplegia. ASC was performed in 20 patients, CDS in 29 patients. The mean time to death following disconnection was 32 (0.3-164) h during ASC and 0.3 (0.2-0.6) h in CDS. In conclusion, a low ALSFRS-R, high incidence of ophthalmoplegia and extended ventilator dependency were found before WLTV. The presence or absence of ventilator-free tolerance determined the approach to the management of symptoms, the setting for immediate end-of-life care and the course of dying in WLTV.

Association of a Locus in the CAMTA1 Gene With Survival in Patients With Sporadic Amyotrophic Lateral Sclerosis

IMPORTANCE

Amyotrophic lateral sclerosis (ALS) is a devastating adult-onset neurodegenerative disorder with a poor prognosis and a median survival of 3 years. However, a significant proportion of patients survive more than 10 years from symptom onset.

OBJECTIVE

To identify gene variants influencing survival in ALS.

DESIGN, SETTING, AND PARTICIPANTS

This genome-wide association study (GWAS) analyzed survival in data sets from several European countries and the United States that were collected by the Italian Consortium for the Genetics of ALS and the International Consortium on Amyotrophic Lateral Sclerosis Genetics. The study population included 4256 patients with ALS (3125 [73.4%] deceased) with genotype data extended to 7 174 392 variants by imputation analysis. Samples of DNA were collected from January 1, 1993, to December 31, 2009, and analyzed from March 1, 2014, to February 28, 2015.

MAIN OUTCOMES AND MEASURES

Cox proportional hazards regression under an additive model with adjustment for age at onset, sex, and the first 4 principal components of ancestry, followed by meta-analysis, were used to analyze data. Survival distributions for the most associated genetic variants were assessed by Kaplan-Meier analysis.

RESULTS

Among the 4256 patients included in the analysis (2589 male [60.8%] and 1667 female [39.2%]; mean [SD] age at onset, 59 [12] years), the following 2 novel loci were significantly associated with ALS survival: at 10q23 (rs139550538; P = 1.87 × 10-9) and in the CAMTA1 gene at 1p36 (rs2412208, P = 3.53 × 10-8). At locus 10q23, the adjusted hazard ratio for patients with the rs139550538 AA or AT genotype was 1.61 (95% CI, 1.38-1.89; P = 1.87 × 10-9), corresponding to an 8-month reduction in survival compared with TT carriers. For rs2412208 CAMTA1, the adjusted hazard ratio for patients with the GG or GT genotype was 1.17 (95% CI, 1.11-1.24; P = 3.53 × 10-8), corresponding to a 4-month reduction in survival compared with TT carriers.

CONCLUSIONS AND RELEVANCE

This GWAS robustly identified 2 loci at genome-wide levels of significance that influence survival in patients with ALS. Because ALS is a rare disease and prevention is not feasible, treatment that modifies survival is the most realistic strategy. Therefore, identification of modifier genes that might influence ALS survival could improve the understanding of the biology of the disease and suggest biological targets for pharmaceutical intervention. In addition, genetic risk scores for survival could be used as an adjunct to clinical trials to account for the genetic contribution to survival.

The selective anatomical vulnerability of ALS: 'disease-defining' and 'disease-defying' brain regions

A large multiparametric MRI study has been undertaken to evaluate anatomical patterns of basal ganglia, white matter and cortical grey matter involvement in ALS. Unaffected brain regions are mapped in patients with significant disability. Multiple white matter diffusivity measures, cortical grey matter density alterations, basal ganglia volumes and subcortical grey matter atrophy patterns are evaluated. Results demonstrated a strikingly selective anatomical vulnerability pattern in ALS that preferentially affects specific grey matter structures, commissural white matter tracts and basal ganglia regions, suggestive of networkwise neurodegeneration in ALS. In conclusion, ALS pathology exhibits predilection for selective and inter-connected anatomical sites that can be comprehensively characterized in vivo by multiparametric neuroimaging. The systematic characterization of unaffected brain regions in ALS has implications for the development of classifier analyses and elucidation of disease biology. The involvement and sparing of contiguous brain regions raises important pathophysiological, phylogenetic and ontogenetic questions regarding ALS pathogenesis and disease spread.

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

Background

The neuropathological process underlying amyotrophic lateral sclerosis (ALS) can be traced as a four-stage progression scheme of sequential corticofugal axonal spread. The examination of eye movement control gains deep insights into brain network pathology and provides the opportunity to detect both disturbance of the brainstem oculomotor circuitry as well as executive deficits of oculomotor function associated with higher brain networks.

Objective

To study systematically oculomotor characteristics in ALS and its underlying network pathology in order to determine whether eye movement deterioration can be categorized within a staging system of oculomotor decline that corresponds to the neuropathological model.

Methods

Sixty-eight ALS patients and 31 controls underwent video-oculographic, clinical and neuropsychological assessments.

Results

Oculomotor examinations revealed increased anti- and delayed saccades’ errors, gaze-palsy and a cerebellary type of smooth pursuit disturbance. The oculomotor disturbances occurred in a sequential manner: Stage 1, only executive control of eye movements was affected. Stage 2 indicates disturbed executive control plus ‘genuine’ oculomotor dysfunctions such as gaze-paly. We found high correlations (p<0.001) between the oculomotor stages and both, the clinical presentation as assessed by the ALS Functional Rating Scale (ALSFRS) score, and cognitive scores from the Edinburgh Cognitive and Behavioral ALS Screen (ECAS).

Conclusions

Dysfunction of eye movement control in ALS can be characterized by a two-staged sequential pattern comprising executive deficits in Stage 1 and additional impaired infratentorial oculomotor control pathways in Stage 2. This pattern parallels the neuropathological staging of ALS and may serve as a technical marker of the neuropathological spreading.

A Gaze Independent Brain-Computer Interface Based on Visual Stimulation through Closed Eyelids

A classical brain-computer interface (BCI) based on visual event-related potentials (ERPs) is of limited application value for paralyzed patients with severe oculomotor impairments. In this study, we introduce a novel gaze independent BCI paradigm that can be potentially used for such end-users because visual stimuli are administered on closed eyelids. The paradigm involved verbally presented questions with 3 possible answers. Online BCI experiments were conducted with twelve healthy subjects, where they selected one option by attending to one of three different visual stimuli. It was confirmed that typical cognitive ERPs can be evidently modulated by the attention of a target stimulus in eyes-closed and gaze independent condition, and further classified with high accuracy during online operation (74.58% ± 17.85 s.d.; chance level 33.33%), demonstrating the effectiveness of the proposed novel visual ERP paradigm. Also, stimulus-specific eye movements observed during stimulation were verified as reflex responses to light stimuli, and they did not contribute to classification. To the best of our knowledge, this study is the first to show the possibility of using a gaze independent visual ERP paradigm in an eyes-closed condition, thereby providing another communication option for severely locked-in patients suffering from complex ocular dysfunctions.

Eye-tracking in amyotrophic lateral sclerosis: A longitudinal study of saccadic and cognitive tasks

A relative preservation of eye movements is notable in ALS, but saccadic functions have not been studied longitudinally. ALS overlaps with FTD, typically involving executive dysfunction, and eye-tracking offers additional potential for the assessment of extramotor pathology where writing and speaking are both impaired. Eye-tracking measures (including anti-saccade, trail-making and visual search tasks) were assessed at six-monthly intervals for up to two years in a group of ALS (n = 61) and primary lateral sclerosis (n = 7) patients, compared to healthy age-matched controls (n = 39) assessed on a single occasion. Task performance was explored speculatively in relation to resting-state functional MRI (R-FMRI) network connectivity. Results showed that ALS patients were impaired on executive and visual search tasks despite normal basic saccadic function, and impairments in the PLS patients were unexpectedly often more severe. No significant progression was detected longitudinally in either group. No changes in R-FMRI network connectivity were identified in relation to patient performance. In conclusion, eye-tracking offers an objective means to assess extramotor cerebral involvement in ALS. The relative resistance of pure oculomotor function is confirmed, and higher-level executive impairments do not follow the same rate of decline as physical disability. PLS patients may have more cortical dysfunction than has been previously appreciated.

Development of an "eyes-closed" brain-computer interface system for communication of patients with oculomotor impairment

The goal of this study was to develop a new steady-state visual evoked potential (SSVEP)-based BCI system, which can be applied to disabled individuals with impaired oculomotor function. The developed BCI system allows users to express their binary intentions without needing to open their eyes. To present visual stimuli, we used a pair of glasses with two LEDs flickering at different frequencies. EEG spectral patterns were classified in real time while participants were attending to one of the presented visual stimuli with their eyes closed. Through offline experiments performed with 11 healthy participants, we confirmed that SSVEP responses could be modulated by visual selective attention to a specific light stimulus penetrating through the eyelids, and could be classified with accuracy high enough for use in a practical BCI system. After customizing the parameters of the proposed SSVEP-based BCI paradigm based on the offline analysis results, binary intentions of five healthy participants and one locked-in state patient were classified online. The average ITR of the online experiments reached to 10.83 bits/min with an average accuracy of 95.3 %. An online experiment applied to a patient with ALS showed a classification accuracy of 80 % and an ITR of 2.78 bits/min, demonstrating the practical feasibility of our BCI paradigm.

Eye-tracking controlled cognitive function tests in patients with amyotrophic lateral sclerosis: a controlled proof-of-principle study

Amyotrophic lateral sclerosis (ALS) primarily affects motor and speech abilities. In addition, cognitive functions are impaired in a subset of patients. There is a need to establish an eye movement-based method of neuropsychological assessment suitable for severely physically impaired patients with ALS. Forty-eight ALS patients and thirty-two healthy controls matched for age, sex and education performed a hand and speech motor-free version of the Raven's coloured progressive matrices (CPM) and the D2-test which had been especially adapted for eye-tracking control. Data were compared to a classical motor-dependent paper-pencil version. The association of parameters of the eye-tracking and the paper-pencil version of the tests and the differences between and within groups were studied. Subjects presented similar results in the eye-tracking and the corresponding paper-pencil versions of the CPM and D2-test: a correlation between performance accuracy for the CPM was observed for ALS patients (p < 0.001) and controls (p < 0.001) and in the D2-test for controls (p = 0.048), whereas this correlation did not reach statistical significance for ALS patients (p = 0.096). ALS patients performed worse in the CPM than controls in the eye-tracking (p = 0.053) and the paper-pencil version (p = 0.042). Most importantly, eye-tracking versions of the CPM (p < 0.001) and the D2-test (p = 0.024) reliably distinguished between more and less cognitively impaired patients. Eye-tracking-based neuropsychological testing is a promising approach for assessing cognitive deficits in patients who are unable to speak or write such as patients with severe ALS.