Ocular Involvement in Friedreich Ataxia Patients and its Relationship with Neurological Disability, a Follow-up Study

Progression of Retinal Ganglion Cell and Nerve Fiber Layer Loss in Spinocerebellar Ataxia 3 Patients

Spectral domain optical coherence tomography (SD-OCT) allows noninvasive measurements of retinal neuron layers. Here, we evaluate the relationship between clinical features and anatomical SD-OCT measurements in patients with spinocerebellar ataxia type 3 (SCA3) and how they change with time. A retrospective review was conducted on SCA3 patients. Clinical variables such as disease duration, number of CAG repeats, and the Scale for the Assessment and Rating of Ataxia (SARA) score were correlated with SD-OCT measurements, including retinal nerve fiber layer (RNFL) thickness, ganglion cell complex (GCC) thickness, macular volume (MV), and central macular thickness (CMT). Seventeen SCA3 patients with an average follow-up of 44.9 months were recruited. Clinical features with significant baseline correlations with SD-OCT measurements included disease duration (CMT r =  - 0.590; GCC r =  - 0.585), SARA score (CMT r =  - 0.560; RNFL r =  - 0.390), and number of CAG repeats (MV r =  - 0.552; RNFL r =  - 0.503; GCC r =  - 0.493). The annual rate of change of the SARA score during follow-up was associated with that of both the MV (r =  - 0.494; p = 0.005) and GCC thickness (r =  - 0.454; p = 0.012). High disability (stages 2 and 3) was independently inversely associated with the annual change in MV (ß coefficient - 17.09; p = 0.025). This study provides evidence of an association between clinical features and objective anatomical measurements obtained by SD-OCT in SCA3 patients. MV and GCC thickness could serve as potential biomarkers of disease severity, as their rates of decrease seem to be related to a worsening in the SARA score. These findings highlight the potential of SD-OCT as a noninvasive tool for assessing disease severity and progression in SCA3 patients.

Health-Related Quality of Life in Patients with Inherited Ataxia in Ireland

Inherited cerebellar ataxias (CA) are heterogeneous progressive neurological conditions associated with significant functional limitations. This study aimed to assess the implications of inherited CA on patients' self-reported quality of life (QoL) and impairments in work and activities. 129 individuals with ataxia responded to a survey focused on QoL. Health-related QoL was measured using the RAND 36-Item Short Form Survey. An adaptation of the validated Work Productivity and Activity Impairment questionnaire was used to assess the effect of health on work productivity and ability to perform activities over the past week. Nine percent of respondents were currently employed. Individuals with inherited ataxia experienced significant activity impairment, and 75% required professional or informal care. Health-related quality of life (HRQoL) was significantly worse in all areas for the individuals with inherited ataxia compared with Irish population normative values. Participants with Friedreich's ataxia (n = 56) demonstrated worse physical functioning then those with undetermined ataxia (n = 55). Female gender, younger age at symptom onset, current employment, retirement due to age or ataxia, and living in a long-term care facility were associated with higher sub-scores in different domains of HRQoL, while disease duration correlated with worse physical functioning sub-scores. This study is the first cross-sectional study on HRQoL in patients with inherited ataxia in Ireland. It highlights high rates of unemployment, difficulty with daily activities and physical functioning limitations, which is worse than comparative international studies. Given the limited therapeutic options currently available, optimising HRQoL is an important aspect of managing ataxia.

Alzheimer's disease: a continuum with visual involvements

Introduction

Alzheimer's disease (AD) is the most common form of dementia affecting the central nervous system, and alteration of several visual structures has been reported. Structural retinal changes are usually accompanied by changes in visual function in this disease. The aim of this study was to analyse the differences in visual function at different stages of the pathology (family history group (FH+), mild cognitive impairment (MCI), mild AD and moderate AD) in comparison with a control group of subjects with no cognitive decline and no family history of AD.

Methods

We included 53 controls, 13 subjects with FH+, 23 patients with MCI, 25 patients with mild AD and, 21 patients with moderate AD. All were ophthalmologically healthy. Visual acuity (VA), contrast sensitivity (CS), colour perception, visual integration, and fundus examination were performed.

Results

The analysis showed a statistically significant decrease in VA, CS and visual integration score between the MCI, mild AD and moderate AD groups compared to the control group. In the CS higher frequencies and in the colour perception test (total errors number), statistically significant differences were also observed in the MCI, mild AD and moderate AD groups with respect to the FH+ group and also between the control and AD groups. The FH+ group showed no statistically significant difference in visual functions compared to the control group. All the test correlated with the Mini Mental State Examination score and showed good predictive value when memory decline was present, with better values when AD was at a more advanced stage.

Conclusion

Alterations in visual function appear in subjects with MCI and evolve when AD is established, being stable in the initial stages of the disease (mild AD and moderate AD). Therefore, visual psychophysical tests are a useful, simple and complementary tool to neuropsychological tests to facilitate diagnosis in the preclinical and early stages of AD.

Multimodal Analysis of the Visual Pathways in Friedreich's Ataxia Reveals Novel Biomarkers

BACKGROUND

Optic neuropathy is a near ubiquitous feature of Friedreich's ataxia (FRDA). Previous studies have examined varying aspects of the anterior and posterior visual pathways but none so far have comprehensively evaluated the heterogeneity of degeneration across different areas of the retina, changes to the macula layers and combined these with volumetric MRI studies of the visual cortex and frataxin level.

METHODS

We investigated 62 genetically confirmed FRDA patients using an integrated approach as part of an observational cohort study. We included measurement of frataxin protein levels, clinical evaluation of visual and neurological function, optical coherence tomography to determine retinal nerve fibre layer thickness and macular layer volume and volumetric brain MRI.

RESULTS

We demonstrate that frataxin level correlates with peripapillary retinal nerve fibre layer thickness and that retinal sectors differ in their degree of degeneration. We also shown that retinal nerve fibre layer is thinner in FRDA patients than controls and that this thinning is influenced by the AAO and GAA1. Furthermore we show that the ganglion cell and inner plexiform layers are affected in FRDA. Our MRI data indicate that there are borderline correlations between retinal layers and areas of the cortex involved in visual processing.

CONCLUSION

Our study demonstrates the uneven distribution of the axonopathy in the retinal nerve fibre layer and highlight the relative sparing of the papillomacular bundle and temporal sectors. We show that thinning of the retinal nerve fibre layer is associated with frataxin levels, supporting the use the two biomarkers in future clinical trials design. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Retinal fingerprints of ALS in patients: Ganglion cell apoptosis and TDP-43/p62 misplacement

Introduction

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by the progressive loss of motor neuron function. Although ophthalmic deficits are not considered a classic symptom of ALS, recent studies suggest that changes in retinal cells, similar to those in the spinal cord motor neurons, have been observed in postmortem human tissues and animal models.

Methods

In this study, we examined by immunofluorescence analysis the retinal cell layers of sporadic ALS patients in post-mortem retinal slices. We evaluated the presence of cytoplasmic TDP-43 and SQSTM1/p62 aggregates, activation of the apoptotic pathway, and microglia and astrocytes reactivity.

Results

We found in the retinal ganglion cell layer of ALS patients the increase of mislocalized TDP-43, SQSTM1/p62 aggregates, activation of cleaved caspase-3, and microglia density, suggesting that retinal changes can be used as an additional diagnostic tool for ALS.

Discussion

The retina is considered part of the central nervous system, and neurodegenerative changes in the brain may be accompanied by structural and possibly functional changes in the neuroretina and ocular vasculature. Therefore, using in vivo retinal biomarkers as an additional diagnostic tool for ALS may provide an opportunity to longitudinally monitor individuals and therapies over time in a noninvasive and cost-effective manner.

Longitudinal Assessment Using Optical Coherence Tomography in Patients with Friedreich's Ataxia

Ocular abnormalities occur frequently in Friedreich's ataxia (FRDA), although visual symptoms are not always reported. We evaluated a cohort of patients with FRDA to characterise the clinical phenotype and optic nerve findings as detected with optical coherence tomography (OCT). A total of 48 patients from 42 unrelated families were recruited. Mean age at onset was 13.8 years (range 4-40), mean disease duration 19.5 years (range 5-43), mean disease severity as quantified with the Scale for the Assessment and Rating of Ataxia 22/40 (range 4.5-38). All patients displayed variable ataxia and two-thirds had ocular abnormalities. Statistically significant thinning of average retinal nerve fibre layer (RNFL) and thinning in all but the temporal quadrant compared to controls was demonstrated on OCT. Significant RNFL and macular thinning was documented over time in 20 individuals. Disease severity and visual acuity were correlated with RNFL and macular thickness, but no association was found with disease duration. Our results highlight that FDRA is associated with subclinical optic neuropathy. This is the largest longitudinal study of OCT findings in FRDA to date, demonstrating progressive RNFL thickness decline, suggesting that RNFL thickness as measured by OCT has the potential to become a quantifiable biomarker for the evaluation of disease progression in FRDA.

An Eye on Movement Disorders

Eye disorders spanning a range of ocular tissue are common in patients with movement disorders. Highlighting these ocular manifestations will benefit patients and may even aid in diagnosis. In this educational review we outline the anatomy and function of the ocular tissues with a focus on the tissues most affected in movement disorders. We review the movement disorders associated with ocular pathology and where possible explore the underlying cellular basis thought to be driving the pathology and provide a brief overview of ophthalmic investigations available to the neurologist. This review does not cover intracranial primary visual pathways, higher visual function, or the ocular motor system.

Designing phase II clinical trials in Friedreich ataxia

INTRODUCTION

Friedreich ataxia (FRDA) is an autosomal recessive disorder caused by deficiency of frataxin, an essential mitochondrial protein involved in iron sulfur cluster biogenesis, oxidative phosphorylation and other processes. FRDA most notably affects the heart, sensory neurons, spinal cord, cerebellum, and other brain regions, and manifests clinically as ataxia, sensory loss, dysarthria, spasticity, and hypertrophic cardiomyopathy. Therapeutic approaches in FRDA have consisted of two different approaches: (1) augmenting or restoring frataxin production and (2) modulating a variety of downstream processes related to mitochondrial dysfunction, including reactive oxygen species production, ferroptosis, or Nrf2 activation.

AREAS COVERED

In this review, we summarize data from major phase II clinical trials in FRDA published between 2015 and 2020, which includes A0001/EPI743, Omaveloxolone, RT001, and Actimmune.

EXPERT OPINION

A growing number of drug candidates are being tested in phase II clinical trials for FRDA; however, most have not met their primary endpoints, and none have received FDA approval. In this review, we aim to summarize completed phase II clinical trials in FRDA, outlining critical lessons that have been learned and that should be incorporated into future trial design to ultimately optimize drug development in FRDA.

Neuro-Ophthalmological Findings in Friedreich's Ataxia

Friedreich ataxia (FRDA) is a progressive neurodegenerative disease caused by a severe autosomal recessive genetic disorder of the central nervous (CNS) and peripheral nervous system (PNS), affecting children and young adults. Its onset is before 25 years of age, with mean ages of onset and death between 11 and 38 years, respectively. The incidence is 1 in 30,000–50,000 persons. It is caused, in 97% of cases, by a homozygous guanine-adenine-adenine (GAA) trinucleotide mutation in the first intron of the frataxin (FXN) gene on chromosome 9 (9q13–q1.1). The mutation of this gene causes a deficiency of frataxin, which induces an altered inflow of iron into the mitochondria, increasing the nervous system’s vulnerability to oxidative stress. The main clinical signs include spinocerebellar ataxia with sensory loss and disappearance of deep tendon reflexes, cerebellar dysarthria, cardiomyopathy, and scoliosis. Diabetes, hearing loss, and pes cavus may also occur, and although most patients with FRDA do not present with symptomatic visual impairment, 73% present with clinical neuro-ophthalmological alterations such as optic atrophy and altered eye movement, among others. This review provides a brief overview of the main aspects of FRDA and then focuses on the ocular involvement of this pathology and the possible use of retinal biomarkers.

The Value of OCT and OCTA as Potential Biomarkers for Preclinical Alzheimer's Disease: A Review Study

Preclinical Alzheimer's disease (AD) includes cognitively healthy subjects with at least one positive biomarker: reduction in cerebrospinal fluid Aβ₄₂ or visualization of cerebral amyloidosis by positron emission tomography imaging. The use of these biomarkers is expensive, invasive, and not always possible. It has been shown that the retinal changes measured by optical coherence tomography (OCT) and OCT-angiography (OCTA) could be biomarkers of AD. Diagnosis in early stages before irreversible AD neurological damage takes place is important for the development of new therapeutic interventions. In this review, we summarize the findings of different published studies using OCT and OCTA in participants with preclinical AD. To date, there have been few studies on this topic and they are methodologically very dissimilar. Moreover, these include only two longitudinal studies. For these reasons, it would be interesting to unify the methodology, make the inclusion criteria more rigorous, and conduct longer longitudinal studies to assess the evolution of these subjects. If the results were consistent across repeated studies with the same methodology, this could provide us with insight into the value of the retinal changes observed by OCT/OCTA as potential reliable, cost-effective, and noninvasive biomarkers of preclinical AD.

Sensitivity of Neuroimaging Indicators in Monitoring the Effects of Interferon Gamma Treatment in Friedreich's Ataxia

The identification of efficient markers of disease progression and response to possibly effective treatments is a key priority for slowly progressive, rare and neurodegenerative diseases, such as Friedreich’s ataxia. Various imaging modalities have documented specific abnormalities in Friedreich’s ataxia that could be tracked to provide useful indicators of efficacy in clinical trials. Advanced MRI imaging (diffusion tensor imaging, DTI; functional MRI, fMRI; and resting-state fMRI, rs-fMRI) and retinal imaging (optical coherence tomography, OCT) were tested longitudinally in a small group of Friedreich’s ataxia patients participating in an open-label clinical trial testing the safety and the efficacy of 6-month treatment with interferon gamma. While the DTI indices documented the slow progression of fractional anisotropy loss, fMRI and rs-fMRI were significantly modified during and after treatment. The fMRI changes significantly correlated with the Scale for the Assessment and Rating of Ataxia, which is used to monitor clinical response. OCT documented the known thickness reduction of the retinal nerve fiber layer thickness, but there was no change over time. This pilot study provides indications for the potential utility of fMRI and rs-fMRI as ancillary measures in clinical trials for Friedreich’s ataxia.