Sensitivity of Advanced Magnetic Resonance Imaging to Progression over Six Months in Early Spinocerebellar Ataxia.

BACKGROUND: Clinical trials for upcoming disease-modifying therapies of spinocerebellar ataxias (SCA), a group of rare movement disorders, lack endpoints sensitive to early disease progression, when therapeutics will be most effective. In addition, regulatory agencies emphasize the importance of biological outcomes. OBJECTIVES: READISCA, a transatlantic clinical trial readiness consortium, investigated whether advanced multimodal magnetic resonance imaging (MRI) detects pathology progression over 6 months in preataxic and early ataxic carriers of SCA mutations. METHODS: A total of 44 participants (10 SCA1, 25 SCA3, and 9 controls) prospectively underwent 3-T MR scanning at baseline and a median [interquartile range] follow-up of 6.2 [5.9-6.7] months; 44% of SCA participants were preataxic. Blinded analyses of annual changes in structural, diffusion MRI, MR spectroscopy, and the Scale for Assessment and Rating of Ataxia (SARA) were compared between groups using nonparametric testing. Sample sizes were estimated for 6-month interventional trials with 50% to 100% treatment effect size, leveraging existing large cohort data (186 SCA1, 272 SCA3) for the SARA estimate. RESULTS: Rate of change in microstructural integrity (decrease in fractional anisotropy, increase in diffusivities) in the middle cerebellar peduncle, corona radiata, and superior longitudinal fasciculus significantly differed in SCAs from controls (P < 0.005), with high effect sizes (Cohen's d = 1-2) and moderate-to-high responsiveness (|standardized response mean| = 0.6-0.9) in SCAs. SARA scores did not change, and their rate of change did not differ between groups. CONCLUSIONS: Diffusion MRI is sensitive to disease progression at very early-stage SCA1 and SCA3 and may provide a >5-fold reduction in sample sizes relative to SARA as endpoint for 6-month-long trials. © 2024 The Author(s). Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

The Cerebellar Cognitive Affective/Schmahmann Syndrome Scale in Spinocerebellar Ataxias.

The Cerebellar Cognitive Affective/Schmahmann Syndrome (CCAS) manifests as impaired executive control, linguistic processing, visual spatial function, and affect regulation. The CCAS has been described in the spinocerebellar ataxias (SCAs), but its prevalence is unknown. We analyzed results of the CCAS/Schmahmann Scale (CCAS-S), developed to detect and quantify CCAS, in two natural history studies of 309 individuals Symptomatic for SCA1, SCA2, SCA3, SCA6, SCA7, or SCA8, 26 individuals Pre-symptomatic for SCA1 or SCA3, and 37 Controls. We compared total raw scores, domain scores, and total fail scores between Symptomatic, Pre-symptomatic, and Control cohorts, and between SCA types. We calculated scale sensitivity and selectivity based on CCAS category designation among Symptomatic individuals and Controls, and correlated CCAS-S performance against age and education, and in Symptomatic patients, against genetic repeat length, onset age, disease duration, motor ataxia, depression, and fatigue. Definite CCAS was identified in 46% of the Symptomatic group. False positive rate among Controls was 5.4%. Symptomatic individuals had poorer global CCAS-S performance than Controls, accounting for age and education. The domains of semantic fluency, phonemic fluency, and category switching that tap executive function and linguistic processing consistently separated Symptomatic individuals from Controls. CCAS-S scores correlated most closely with motor ataxia. Controls were similar to Pre-symptomatic individuals whose nearness to symptom onset was unknown. The use of the CCAS-S identifies a high CCAS prevalence in a large cohort of SCA patients, underscoring the utility of the scale and the notion that the CCAS is the third cornerstone of clinical ataxiology.

Clinically Meaningful Magnetic Resonance Endpoints Sensitive to Preataxic Spinocerebellar Ataxia Types 1 and 3.

OBJECTIVE: This study was undertaken to identify magnetic resonance (MR) metrics that are most sensitive to early changes in the brain in spinocerebellar ataxia type 1 (SCA1) and type 3 (SCA3) using an advanced multimodal MR imaging (MRI) protocol in the multisite trial setting. METHODS: SCA1 or SCA3 mutation carriers and controls (n = 107) underwent MR scanning in the US-European READISCA study to obtain structural, diffusion MRI, and MR spectroscopy data using an advanced protocol at 3T. Morphometric, microstructural, and neurochemical metrics were analyzed blinded to diagnosis and compared between preataxic SCA (n = 11 SCA1, n = 28 SCA3), ataxic SCA (n = 14 SCA1, n = 37 SCA3), and control (n = 17) groups using nonparametric testing accounting for multiple comparisons. MR metrics that were most sensitive to preataxic abnormalities were identified using receiver operating characteristic (ROC) analyses. RESULTS: Atrophy and microstructural damage in the brainstem and cerebellar peduncles and neurochemical abnormalities in the pons were prominent in both preataxic groups, when patients did not differ from controls clinically. MR metrics were strongly associated with ataxia symptoms, activities of daily living, and estimated ataxia duration. A neurochemical measure was the most sensitive metric to preataxic changes in SCA1 (ROC area under the curve [AUC] = 0.95), and a microstructural metric was the most sensitive metric to preataxic changes in SCA3 (AUC = 0.92). INTERPRETATION: Changes in cerebellar afferent and efferent pathways underlie the earliest symptoms of both SCAs. MR metrics collected with a harmonized advanced protocol in the multisite trial setting allow detection of disease effects in individuals before ataxia onset with potential clinical trial utility for subject stratification. ANN NEUROL 2022.

The S-Factor, a New Measure of Disease Severity in Spinocerebellar Ataxia: Findings and Implications.

Spinocerebellar ataxias (SCAs) are progressive neurodegenerative disorders, but there is no metric that predicts disease severity over time. We hypothesized that by developing a new metric, the Severity Factor (S-Factor) using immutable disease parameters, it would be possible to capture disease severity independent of clinical rating scales. Extracting data from the CRC-SCA and READISCA natural history studies, we calculated the S-Factor for 438 participants with symptomatic SCA1, SCA2, SCA3, or SCA6, as follows: ((length of CAG repeat expansion - maximum normal repeat length) /maximum normal repeat length) × (current age - age at disease onset) × 10). Within each SCA type, the S-Factor at the first Scale for the Assessment and Rating of Ataxia (SARA) visit (baseline) was correlated against scores on SARA and other motor and cognitive assessments. In 281 participants with longitudinal data, the slope of the S-Factor over time was correlated against slopes of scores on SARA and other motor rating scales. At baseline, the S-Factor showed moderate-to-strong correlations with SARA and other motor rating scales at the group level, but not with cognitive performance. Longitudinally the S-Factor slope showed no consistent association with the slope of performance on motor scales. Approximately 30% of SARA slopes reflected a trend of non-progression in motor symptoms. The S-Factor is an observer-independent metric of disease burden in SCAs. It may be useful at the group level to compare cohorts at baseline in clinical studies. Derivation and examination of the S-factor highlighted challenges in the use of clinical rating scales in this population.

Neurochemical abnormalities in premanifest and early spinocerebellar ataxias.

OBJECTIVE: To investigate whether early neurochemical abnormalities are detectable by high-field magnetic resonance spectroscopy (MRS) in individuals with spinocerebellar ataxias (SCAs) 1, 2, 3, and 6, including patients without manifestation of ataxia. METHODS: A cohort of 100 subjects (N = 18-21 in each SCA group, including premanifest mutation carriers; mean score on the Scale for the Assessment and Rating of Ataxia [SARA] <10 for all genotypes, and 22 matched controls) was scanned at 7 Tesla to obtain neurochemical profiles of the cerebellum and brainstem. A novel multivariate approach (distance-weighted discrimination) was used to combine regional profiles into an "MRS score." RESULTS: MRS scores robustly distinguished individuals with SCA from controls, with misclassification rates of 0% (SCA2), 2% (SCA3), 5% (SCA1), and 17% (SCA6). Premanifest mutation carriers with estimated disease onset within 10 years had MRS scores in the range of early-manifest SCA subjects. Levels of neuronal and glial markers significantly correlated with SARA and an Activities of Daily Living score in subjects with SCA. Regional neurochemical alterations were different between SCAs at comparable disease severity, with SCA2 displaying the most extensive neurochemical abnormalities, followed by SCA1, SCA3, and SCA6. INTERPRETATION: Neurochemical abnormalities are detectable in individuals before manifest disease, which may allow premanifest enrollment in future SCA trials. Correlations with ataxia and quality-of-life scores show that neurochemical levels can serve as clinically meaningful endpoints in trials. Ranking of SCA types by degree of neurochemical abnormalities indicates that the neurochemistry may reflect synaptic function or density. Ann Neurol 2018;83:816-829.

Proceedings of the workshop on Cerebellum, Basal Ganglia and Cortical Connections Unmasked in Health and Disorder held in Brno, Czech Republic, October 17th, 2013.

The proceedings of the workshop synthesize the experimental, preclinical, and clinical data suggesting that the cerebellum, basal ganglia (BG), and their connections play an important role in pathophysiology of various movement disorders (like Parkinson's disease and atypical parkinsonian syndromes) or neurodevelopmental disorders (like autism). The contributions from individual distinguished speakers cover the neuroanatomical research of complex networks, neuroimaging data showing that the cerebellum and BG are connected to a wide range of other central nervous system structures involved in movement control. Especially, the cerebellum plays a more complex role in how the brain functions than previously thought.

Role of olivocerebellar system in timing without awareness.

The timing of events can be implicit or without awareness yet critical for task performance. However, the neural correlates of implicit timing are unknown. One system that has long been implicated in event timing is the olivocerebellar system, which originates exclusively from the inferior olive. By using event-related functional MRI in human subjects and a specially designed behavioral task, we examined the effect of the subjects' awareness of changes in stimulus timing on the olivocerebellar system response. Subjects were scanned while observing changes in stimulus timing that were presented near each subject's detection threshold such that subjects were aware of such changes in only approximately half the trials. The inferior olive and multiple areas within the cerebellar cortex showed a robust response to time changes regardless of whether the subjects were aware of these changes. Our findings provide support to the proposed role of the olivocerebellar system in encoding temporal information and further suggest that this system can operate independently of awareness and mediate implicit timing in a multitude of perceptual and motor operations, including classical conditioning and implicit learning.

SARA captures disparate progression and responsiveness in spinocerebellar ataxias.

BACKGROUND: The Scale for Assessment and Rating of Ataxia (SARA) is a widely used clinical scale to assess cerebellar ataxia but faces some criticisms about the relevancy of all its items. OBJECTIVES: To prepare for future clinical trials, we analyzed the progression of SARA and its items in several polyQ spinocerebellar ataxias (SCA) from various cohorts. METHODS: We included data from patients with SCA1, SCA2, SCA3, and SCA6 from four cohorts (EUROSCA, RISCA, CRC-SCA, and SPATAX) for a total of 850 carriers and 3431 observations. Longitudinal progression of the SARA and its items was measured. Cohort, stage and genetic effects were tested. We looked at the respective contribution of each item to the total scale. Sensitivity to change of the scale and the impact of item removal was evaluated by calculating sample sizes needed in various scenarios. RESULTS: Longitudinal progression was significantly different between cohorts in SCA1, SCA2 and SCA3, the EUROSCA cohort having the fastest progression. Advanced-stage patients were progressing slower in SCA2 and SCA6. Items were not contributing equally to the full scale through ataxia severity: gait, stance, hand movement, and heel-shin contributed the most in the early stage, and finger-chase, nose-finger, and sitting in later stages. Few items drove the sensitivity to the change of SARA, but changes in the scale structure could not improve its sensitivity in all populations. CONCLUSION: SARA and its item's progression pace showed high heterogeneity across cohorts and SCAs. However, no combinations of items improved the responsiveness in all SCAs or populations taken separately.

Fatigue Impacts Quality of Life in People with Spinocerebellar Ataxias.

BACKGROUND: Fatigue is a prevalent and debilitating symptom in neurological disorders, including spinocerebellar ataxias (SCAs). However, the risk factors of fatigue in the SCAs as well as its impact have not been well investigated. OBJECTIVES: To study the prevalence of fatigue in SCAs, the factors contributing to fatigue, and the influence of fatigue on quality of life. METHODS: Fatigue was assessed in 418 participants with SCA1, SCA2, SCA3, and SCA6 from the Clinical Research Consortium for the Study of Cerebellar Ataxia using the Fatigue Severity Scale. We conducted multi-variable linear regression models to examine the factors contributing to fatigue as well as the association between fatigue and quality of life. RESULTS: Fatigue was most prevalent in SCA3 (52.6%), followed by SCA1 (36.7%), SCA6 (35.7%), and SCA2 (35.6%). SCA cases with fatigue had more severe ataxia and worse depressive symptoms. In SCA3, those with fatigue had a longer disease duration and longer pathological CAG repeat numbers. In multi-variable models, depressive symptoms, but not ataxia severity, were associated with more severe fatigue. Fatigue, independent of ataxia and depression, contributed to worse quality of life in SCA3 and SCA6 at baseline, and fatigue continued affecting quality of life throughout the disease course in all types of SCA. CONCLUSIONS: Fatigue is a common symptom in SCAs and is closely related to depression. Fatigue significantly impacts patients' quality of life. Therefore, screening for fatigue should be considered a part of standard clinical care for SCAs.

FXN methylation predicts expression and clinical outcome in Friedreich ataxia.

OBJECTIVE: Friedreich ataxia (FA) is the most common ataxia and results from an expanded GAA repeat in the first intron of FXN. This leads to epigenetic modifications and reduced frataxin. We investigated the relationships between genetic, epigenetic, and clinical parameters in a large case-control study of FA. METHODS: Clinical data and samples were obtained from individuals with FA during annual visits to our dedicated FA clinic. GAA expansions were evaluated by polymerase chain reaction (PCR) and restriction endonuclease digest. DNA methylation was measured using bisulfite-based EpiTYPER MassARRAY (Sequenom, San Diego, CA). FXN expression was determined using real-time reverse transcriptase PCR. Significant correlations between the different parameters were examined using the nonparametric Spearman rank correlation coefficient, as well as univariate and multivariate regression modeling. RESULTS: Characteristic DNA methylation was identified upstream and downstream of the expansion, and validated in an independent FA cohort. Univariate and multivariate analyses showed significant inverse correlations between upstream methylation and FXN expression, and variation in downstream methylation and age of onset. FXN expression also inversely correlated with the Friedreich Ataxia Rating Scale score, an indicator of disease severity. INTERPRETATION: These novel findings provide compelling evidence for the link between the GAA expansion, the DNA methylation profile, FXN expression, and clinical outcome in FA. Epigenetic profiling of FXN could be used to gain greater insight into disease onset and progression, but also as a biomarker to learn more about specific treatment responses and pharmacological mechanism(s). This work also highlights the potential for developing therapies aimed at increasing frataxin levels to treat this debilitating disease.

Brain MRI detects early-stage alterations and disease progression in Friedreich ataxia.

Friedreich ataxia is a progressive neurodegenerative disorder characterized by cerebellar and spinal atrophy. However, studies to elucidate the longitudinal progression of the pathology in the brain are somewhat inconsistent and limited, especially for early-stage Friedreich ataxia. Using a multimodal neuroimaging protocol, combined with advanced analysis methods, we sought to identify macrostructural and microstructural alterations in the brain of patients with early-stage Friedreich ataxia to better understand its distribution patterns and progression. We enrolled 28 patients with Friedreich ataxia and 20 age- and gender-matched controls. Longitudinal clinical and imaging data were collected in the patients at baseline, 12, 24 and 36 months. Macrostructural differences were observed in patients with Friedreich ataxia, compared to controls, including lower volume of the cerebellar white matter (but not cerebellar grey matter), superior cerebellar peduncle, thalamus and brainstem structures, and higher volume of the fourth ventricle. Diffusion tensor imaging and fixel-based analysis metrics also showed microstructural differences in several brain regions, especially in the cerebellum and corticospinal tract. Over time, many of these macrostructural and microstructural alterations progressed, especially cerebellar grey and white matter volumes, and microstructure of the superior cerebellar peduncle, posterior limb of the internal capsule and superior corona radiata. In addition, linear regressions showed significant associations between many of those imaging metrics and clinical scales. This study provides evidence of early-stage macrostructural and microstructural alterations and of progression over time in the brain in Friedreich ataxia. Moreover, it allows to non-invasively map such brain alterations over a longer period (3 years) than any previous study, and identifies several brain regions with significant involvement in the disease progression besides the cerebellum. We show that fixel-based analysis of diffusion MRI data is particularly sensitive to longitudinal change in the cerebellar peduncles, as well as motor and sensory white matter tracts. In combination with other morphometric measures, they may therefore provide sensitive imaging biomarkers of disease progression for clinical trials.

Spinal cord magnetic resonance imaging and spectroscopy detect early-stage alterations and disease progression in Friedreich ataxia.

Friedreich ataxia is the most common hereditary ataxia. Atrophy of the spinal cord is one of the hallmarks of the disease. MRI and magnetic resonance spectroscopy are powerful and non-invasive tools to investigate pathological changes in the spinal cord. A handful of studies have reported cross-sectional alterations in Friedreich ataxia using MRI and diffusion MRI. However, to our knowledge no longitudinal MRI, diffusion MRI or MRS results have been reported in the spinal cord. Here, we investigated early-stage cross-sectional alterations and longitudinal changes in the cervical spinal cord in Friedreich ataxia, using a multimodal magnetic resonance protocol comprising morphometric (anatomical MRI), microstructural (diffusion MRI), and neurochemical (1H-MRS) assessments.We enrolled 28 early-stage individuals with Friedreich ataxia and 20 age- and gender-matched controls (cross-sectional study). Disease duration at baseline was 5.5 ± 4.0 years and Friedreich Ataxia Rating Scale total neurological score at baseline was 42.7 ± 13.6. Twenty-one Friedreich ataxia participants returned for 1-year follow-up, and 19 of those for 2-year follow-up (cohort study). Each visit consisted in clinical assessments and magnetic resonance scans. Controls were scanned at baseline only. At baseline, individuals with Friedreich ataxia had significantly lower spinal cord cross-sectional area (-31%, P = 8 × 10-17), higher eccentricity (+10%, P = 5 × 10-7), lower total N-acetyl-aspartate (tNAA) (-36%, P = 6 × 10-9) and higher myo-inositol (mIns) (+37%, P = 2 × 10-6) corresponding to a lower ratio tNAA/mIns (-52%, P = 2 × 10-13), lower fractional anisotropy (-24%, P = 10-9), as well as higher radial diffusivity (+56%, P = 2 × 10-9), mean diffusivity (+35%, P = 10-8) and axial diffusivity (+17%, P = 4 × 10-5) relative to controls. Longitudinally, spinal cord cross-sectional area decreased by 2.4% per year relative to baseline (P = 4 × 10-4), the ratio tNAA/mIns decreased by 5.8% per year (P = 0.03), and fractional anisotropy showed a trend to decrease (-3.2% per year, P = 0.08). Spinal cord cross-sectional area correlated strongly with clinical measures, with the strongest correlation coefficients found between cross-sectional area and Scale for the Assessment and Rating of Ataxia (R = -0.55, P = 7 × 10-6) and between cross-sectional area and Friedreich ataxia Rating Scale total neurological score (R = -0.60, P = 4 × 10-7). Less strong but still significant correlations were found for fractional anisotropy and tNAA/mIns. We report here the first quantitative longitudinal magnetic resonance results in the spinal cord in Friedreich ataxia. The largest longitudinal effect size was found for spinal cord cross-sectional area, followed by tNAA/mIns and fractional anisotropy. Our results provide direct evidence that abnormalities in the spinal cord result not solely from hypoplasia, but also from neurodegeneration, and show that disease progression can be monitored non-invasively in the spinal cord.

Distinct neurochemical profiles of spinocerebellar ataxias 1, 2, 6, and cerebellar multiple system atrophy.

Hereditary and sporadic neurodegenerative ataxias are movement disorders that affect the cerebellum. Robust and objective biomarkers are critical for treatment trials of ataxias. In addition, such biomarkers may help discriminate between ataxia subtypes because these diseases display substantial overlap in clinical presentation and conventional MRI. Profiles of 10-13 neurochemical concentrations obtained in vivo by high field proton magnetic resonance spectroscopy ((1)H MRS) can potentially provide ataxia-type specific biomarkers. We compared cerebellar and brainstem neurochemical profiles measured at 4 T from 26 patients with spinocerebellar ataxias (SCA1, N = 9; SCA2, N = 7; SCA6, N = 5) or cerebellar multiple system atrophy (MSA-C, N = 5) and 15 age-matched healthy controls. The Scale for the Assessment and Rating of Ataxia (SARA) was used to assess disease severity. The patterns of neurochemical alterations relative to controls differed between ataxia types. Myo-inositol levels in the vermis, myo-inositol, total N-acetylaspartate, total creatine, glutamate, glutamine in the cerebellar hemispheres and myo-inositol, total N-acetylaspartate, glutamate in the pons were significantly different between patient groups (Bonferroni corrected p < 0.05). The best MRS predictors were selected by a tree classification procedure and lead to 89% accurate classification of all subjects while the SARA scores overlapped considerably between patient groups. Therefore, this study demonstrated multiple neurochemical alterations in SCAs and MSA-C relative to controls and the potential for these neurochemical levels to differentiate ataxia types. Studies with higher numbers of patients and other ataxias are warranted to further investigate the clinical utility of neurochemical levels as measured by high-field MRS as ataxia biomarkers.

Measuring the rate of progression in Friedreich ataxia: implications for clinical trial design.

Friedreich ataxia is an autosomal recessive neurodegenerative disorder characterized by ataxia of all four limbs, dysarthria, and arreflexia. A variety of measures are currently used to quantify disease progression, including the Friedreich Ataxia Rating Scale, examiner-rated functional disability scales, self-reported activities of daily living and performance measures such as the timed 25-foot walk, 9-hole pegboard test, PATA speech test, and low-contrast letter acuity vision charts. This study examines the rate of disease progression over one and two years in a cohort of 236 Friedreich ataxia patients using these scales and performance measure composites. The Friedreich Ataxia Rating Scale and performance-measure composites captured disease progression, with a greater sensitivity to change over 2 years than over 1 year. The measures differed in their sensitivity to change and in possible bias. These results help to establish norms for progression in FRDA that can be useful in measuring the long-term success of therapeutic agents and defining sample-size calculations for double-blind clinical trials.

Neurochemical alterations in spinocerebellar ataxia type 1 and their correlations with clinical status.

Robust biomarkers of neurodegeneration are critical for testing of neuroprotective therapies. The clinical applicability of such biomarkers requires sufficient sensitivity to detect disease in individuals. Here we tested the sensitivity of high field (4 tesla) proton magnetic resonance spectroscopy ((1)H MRS) to neurochemical alterations in the cerebellum and brainstem in spinocerebellar ataxia type 1 (SCA1). We measured neurochemical profiles that consisted of 10 to 15 metabolite concentrations in the vermis, cerebellar hemispheres and pons of patients with SCA1 (N = 9) and healthy controls (N = 15). Total NAA (N-acetylaspartate + N-acetylaspartylglutamate, tNAA) and glutamate were lower and glutamine, myo-inositol and total creatine (creatine + phosphocreatine, tCr) were higher in patients relative to controls, consistent with neuronal dysfunction/loss, gliotic activity, and alterations in glutamate-glutamine cycling and energy metabolism. Changes in tNAA, tCr, myo-inositol, and glutamate levels were discernible in individual spectra and the tNAA/myo-inositol ratio in the cerebellar hemispheres and pons differentiated the patients from controls with 100% specificity and sensitivity. In addition, tNAA, myo-inositol, and glutamate levels in the cerebellar hemispheres and the tNAA and myo-inositol levels in the pons correlated with ataxia scores (Scale for the Assessment and Rating of Ataxia, SARA). Two other biomarkers measured in the cerebrospinal fluid (CSF) of a subset of the volunteers (F(2)-isoprostanes asa marker of oxidative stress and glial fibrillary acidic protein (GFAP) as a marker of gliosis) were not different between patients and controls. These data demonstrate that (1)H MRS biomarkers can be utilized to noninvasively assess neuronal and glial status in individual ataxia patients.

Sensitivity of Volumetric Magnetic Resonance Imaging and Magnetic Resonance Spectroscopy to Progression of Spinocerebellar Ataxia Type 1.

BACKGROUND: Spinocerebellar ataxia type 1 (SCA1) causes progressive degeneration of the cerebellum and brainstem. Volumetric magnetic resonance imaging (MRI) was shown to be more sensitive to disease progression than the most sensitive clinical measure, the Scale for the Assessment and Rating of Ataxia (SARA), in longitudinal studies, and magnetic resonance spectroscopy (MRS) was shown to detect neurochemical abnormalities with high sensitivity cross-sectionally in SCA1. OBJECTIVES: The objectives of this study were to compare the sensitivities to change of volumetric MRI, MRS, and SARA in a 3-year longitudinal study in SCA1. METHODS: A total of 16 early-to-moderate stage patients with SCA1 (SARA 0-14) and 21 matched healthy participants were scanned up to 3 times with 1.5-year intervals. Ataxia severity was assessed with SARA. T1-weighted images and magnetic resonance spectra from the cerebellar vermis, cerebellar white matter, and pons were acquired at 3T. RESULTS: The pontine total N-acetylaspartate-to-myo-inositol ratio was the most sensitive MRS measure to change (-3.9 ± 4.6%/yr in SCA1 vs. -0.3 ± 3.5%/yr in controls; P < 0.02), and the pontine volume was the most sensitive MRI measure to change (-2.6 ± 1.2%/yr in SCA1 vs. -0.1 ± 1.2 in controls; P < 0.02). Effect size (mean percent change/standard deviation of percent change) of pontine volume was highest (-2.13) followed by pontine N-acetylaspartate-to-myo-inositol ratio (-0.84) and SARA (+0.60). The pontine N-acetylaspartate-to-myo-inositol ratio was abnormal for 1 premanifest patient at all visits and predicted study withdrawal as a result of disease progression in 3 patients. CONCLUSION: Both MRI and MRS were more sensitive to disease progression than SARA in SCA1. Pontine volume was most sensitive to change, whereas MRS may have more sensitivity at the premanifest stage and predictive value for disease progression.

Analysis of the visual system in Friedreich ataxia.

To use optical coherence tomography (OCT) and contrast letter acuity to characterize vision loss in Friedreich ataxia (FRDA). High- and low-contrast letter acuity and neurological measures were assessed in 507 patients with FRDA. In addition, OCT was performed on 63 FRDA patients to evaluate retinal nerve fiber layer (RNFL) and macular thickness. Both OCT and acuity measures were analyzed in relation to genetic severity, neurologic function, and other disease features. High- and low-contrast letter acuity was significantly predicted by age and GAA repeat length, and highly correlated with neurological outcomes. When tested by OCT, 52.7% of eyes (n = 110) had RNFL thickness values below the fifth percentile for age-matched controls. RNFL thickness was significantly lowest for those with worse scores on the Friedreich ataxia rating scale (FARS), worse performance measure composite Z2 scores, and lower scores for high- and low-contrast acuity. In linear regression analysis, GAA repeat length and age independently predicted RNFL thickness. In a subcohort of participants, 21% of eyes from adult subjects (n = 29 eyes) had macular thickness values below the first percentile for age-matched controls, suggesting that macular abnormalities can also be present in FRDA. Low-contrast acuity and RNFL thickness capture visual and neurologic function in FRDA, and reflect genetic severity and disease progression independently. This suggests that such measures are useful markers of neurologic progression in FRDA.

Clinical characteristics of patients with spinocerebellar ataxias 1, 2, 3 and 6 in the US; a prospective observational study.

BACKGROUND: All spinocerebellar ataxias (SCAs) are rare diseases. SCA1, 2, 3 and 6 are the four most common SCAs, all caused by expanded polyglutamine-coding CAG repeats. Their pathomechanisms are becoming increasingly clear and well-designed clinical trials will be needed. METHODS: To characterize the clinical manifestations of spinocerebellar ataxia (SCA) 1, 2, 3 and 6 and their natural histories in the United States (US), we conducted a prospective multicenter study utilized a protocol identical to the European consortium study, using the Scale for the Assessment and Rating of Ataxia (SARA) score as the primary outcome, with follow-ups every 6 months up to 2 years. RESULTS: We enrolled 345 patients (60 SCA1, 75 SCA2, 138 SCA3 and 72 SCA6) at 12 US centers. SCA6 patients had a significantly later onset, and SCA2 patients showed greater upper-body ataxia than patients with the remaining SCAs. The annual increase of SARA score was greater in SCA1 patients (mean ± SE: 1.61 ± 0.41) than in SCA2 (0.71 ± 0.31), SCA3 (0.65 ± 0.24) and SCA6 (0.87 ± 0.28) patients (p = 0.049). The functional stage also worsened faster in SCA1 than in SCA2, 3 and 6 (p = 0.002). CONCLUSIONS: The proportions of different SCA patients in US differ from those in the European consortium study, but as in the European patients, SCA1 progress faster than those with SCA2, 3 and 6. Later onset in SCA6 and greater upper body ataxia in SCA2 were noted. We conclude that progression rates of these SCAs were comparable between US and Europe cohorts, suggesting the feasibility of international collaborative clinical studies.

Friedreich ataxia clinical outcome measures: natural history evaluation in 410 participants.

Friedreich ataxia is an autosomal recessive neurodegenerative disorder characterized by ataxia, dysarthria, and areflexia. The authors report the progress of a large international noninterventional cohort (n = 410), tracking the natural history of disease progression using the neurologic examination-based Friedreich Ataxia Rating Scale. The authors analyzed the rate of progression with cross-sectional analysis and longitudinal analysis over a 2-year period. The Friedreich Ataxia Rating Scale captured disease progression when used at 1 and 2 years following initial evaluation, with a lower ratio of standard deviation of change to mean change over 2 years of evaluation. However, modeling of disease progression identified substantial ceiling effects in the Friedreich Ataxia Rating Scale, suggesting this measure is most useful in subjects before maximal deficit is approached.

(1)H MR spectroscopy in Friedreich's ataxia and ataxia with oculomotor apraxia type 2.

BACKGROUND AND AIM: Friedreich's ataxia (FRDA) and ataxia with oculomotor apraxia type 2 (AOA2) are the two most frequent forms of autosomal recessive cerebellar ataxias. However, brain metabolism in these disorders is poorly characterized and biomarkers of the disease progression are lacking. We aimed at assessing the neurochemical profile of the pons, the cerebellar hemisphere and the vermis in patients with FRDA and AOA2 to identify potential biomarkers of these diseases. METHODS: Short-echo, single-voxel proton ((1)H) magnetic resonance spectroscopy data were acquired from 8 volunteers with FRDA, 9 volunteers with AOA2, and 38 control volunteers at 4T. Disease severity was assessed by the Friedreich's Ataxia Rating Scale (FARS). RESULTS: Neuronal loss/dysfunction was indicated in the cerebellar vermis and hemispheres in both diseases by lower total N-acetylaspartate levels than controls. The putative gliosis marker myo-inositol was higher than controls in the vermis and pons in AOA2 and in the vermis in FRDA. Total creatine, another potential gliosis marker, was higher in the cerebellar hemispheres in FRDA relative to controls. Higher glutamine in FRDA and lower glutamate in AOA2 than controls were observed in the vermis, indicating different mechanisms possibly leading to altered glutamatergic neurotransmission. In AOA2, total N-acetylaspartate levels in the cerebellum strongly correlated with the FARS score (p<0.01). CONCLUSION: Distinct neurochemical patterns were observed in the two patient populations, warranting further studies with larger patient populations to determine if the alterations in metabolite levels observed here may be utilized to monitor disease progression and treatment.