Cognition in Friedreich's ataxia: a behavioral and multimodal imaging study

Subtypes of cognitive impairment in cerebellar disease identified by cross-diagnostic cluster-analysis: results from a German multicenter study

BACKGROUND

Cognitive and neuropsychiatric impairment, known as cerebellar cognitive affective syndrome (CCAS), may be present in cerebellar disorders. This study identified distinct CCAS subtypes in cerebellar patients using cluster analysis.

METHODS

The German CCAS-Scale (G-CCAS-S), a brief screening test for CCAS, was assessed in 205 cerebellar patients and 200 healthy controls. K-means cluster analysis was applied to G-CCAS-S data to identify cognitive clusters in patients. Demographic and clinical variables were used to characterize the clusters. Multiple linear regression quantified their relative contribution to cognitive performance. The ability of the G-CCAS-S to correctly distinguish between patients and controls was compared across the clusters.

RESULTS

Two clusters explained the variance of cognitive performance in patients' best. Cluster 1 (30%) exhibited severe impairment. Cluster 2 (70%) displayed milder dysfunction and overlapped substantially with that of healthy controls. Cluster 1 patients were on average older, less educated, showed more severe ataxia and more extracerebellar involvement than cluster 2 patients. The cluster assignment predicted cognitive performance even after adjusting for all other covariates. The G-CCAS-S demonstrated good discriminative ability for cluster 1, but not for cluster 2.

CONCLUSIONS

The variance of cognitive impairment in cerebellar disorders is best explained by one severely affected and one mildly affected cluster. Cognitive performance is not only predicted by demographic/clinical characteristics, but also by cluster assignment itself. This indicates that factors that have not been captured in this study likely have effects on cognitive cerebellar functions. Moreover, the CCAS-S appears to have a relative weakness in identifying patients with only mild cognitive deficits.

STUDY REGISTRATION

The study has prospectively been registered at the German Clinical Study Register ( https://www.drks.de ; DRKS-ID: DRKS00016854).

Exploring neuropsychiatric symptoms in Friedreich ataxia

Neuropsychiatric symptoms (NPS) are common in hereditary ataxias as a part of the cerebellar cognitive affective syndrome. In Friedreich ataxia (FRDA), one of the most common hereditary ataxias, depressive symptoms were previously reported, but little is known about other NPS. We aimed to study the presence and severity of a broad range of NPS in individuals with FRDA and assess the relationship between the NPS and the disease severity, cognition, and quality of life and to examine the concordance between the NPS reported by the patients and by their informants. Mild Behavioral Impairment Checklist (MBI-C), a questionnaire designed for screening NPS in the early stages of neurodegenerative diseases, was administered to informants of individuals with FRDA and healthy controls and to people with FRDA themselves. Compared to healthy controls, patients with FRDA scored significantly higher in the total MBI-C score, emotion dysregulation domain (corresponding to depression and anxiety), and decreased motivation domain. When assessed by caregiver, the total MBI-C score and several NPS domains correlated with activities of daily living. Only psychotic symptoms were related to ataxia severity and general cognition. When endorsed by patients, only the relation between few MBI-C domains and quality of life was observed. We found slight to moderate agreement between informant-rated and patient-rated scores. NPS, particularly emotion dysregulation and decreased motivation, are common and clinically relevant in FRDA and should receive more attention due to their potential impact on quality of life and the possibility of therapeutic intervention.

Cognitive impairment associated with cerebellar volume loss in spinocerebellar ataxia type 3

BACKGROUND

Many neuroscience and neurology studies have forced a reconsideration of the traditional motor-related scope of cerebellar function, which has now expanded to include various cognitive functions. Spinocerebellar ataxia type 3 (SCA3; the most common hereditary ataxia) is neuropathologically characterized by cerebellar atrophy and frequently presents with cognitive impairment.

OBJECTIVE

To characterize cognitive impairment in SCA3 and investigate the cerebellum-cognition associations.

METHODS

This prospective, cross-sectional cohort study recruited 126 SCA3 patients and 41 healthy control individuals (HCs). Participants underwent a brain 3D T1-weighted images as well as neuropsychological tests. Voxel-based morphometry (VBM) and region of interest (ROI) approaches were performed on the 3D T1-weighted images. CERES was used to automatically segment cerebellums. Patients were grouped into cognitively impaired (CI) and cognitively preserved (CP), and clinical and MRI parameters were compared. Multivariable regression models were fitted to examine associations between cerebellar microstructural alterations and cognitive domain impairments.

RESULTS

Compared to HCs, SCA3 patients showed cognitive domain impairments in information processing speed, verbal memory, executive function, and visuospatial perception. Between CI and CP subgroups, the CI subgroup was older and had lower education, as well as higher severity scores. VBM and ROI analyses revealed volume loss in cerebellar bilateral lobule VI, right lobule Crus I, and right lobule IV of the CI subgroup, and all these cerebellar lobules were associated with the above cognitive domain impairments.

CONCLUSIONS

Our findings demonstrate the multiple cognitive domain impairments in SCA3 patients and indicate the responsible cerebellar lobules for the impaired cognitive domain(s).

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.

Neuropsychiatric symptoms in spinocerebellar ataxias and Friedreich ataxia

Apart from its role in motor coordination, the importance of the cerebellum in cognitive and affective processes has been recognized in the past few decades. Spinocerebellar ataxias (SCA) and Friedreich ataxia (FRDA) are rare neurodegenerative diseases of the cerebellum presenting mainly with a progressive loss of gait and limb coordination, dysarthria, and other motor disturbances, but also a range of cognitive and neuropsychiatric symptoms. This narrative review summarizes the current knowledge on neuropsychiatric impairment in SCA and FRDA. We discuss the prevalence, clinical features and treatment approaches in the most commonly reported domains of depression, anxiety, apathy, agitation and impulse dyscontrol, and psychosis. Since these symptoms have a considerable impact on patients' quality of life, we argue that further research is mandated to improve the detection and treatment options of neuropsychiatric co-morbidities in ataxia patients.

Reduced cerebello-cerebral functional connectivity correlates with disease severity and impaired white matter integrity in Friedreich ataxia

Friedreich ataxia (FRDA) is a rare, inherited neurodegenerative disease characterised in most cases by progressive and debilitating motor dysfunction. Degeneration of cerebellar white matter pathways have been previously reported, alongside indications of cerebello-cerebral functional alterations. In this work, we examine resting-state functional connectivity changes within cerebello-cerebral circuits, and their associations with disease severity (Scale for the Assessment and Rating of Ataxia [SARA]), psychomotor function (speeded and paced finger tapping), and white matter integrity (diffusion tensor imaging) in 35 adults with FRDA and 45 age and sex-matched controls. Voxel-wise seed-based functional connectivity was assessed for three cerebellar cortical regions (anterior lobe, lobules I-V; superior posterior lobe, lobules VI-VIIB; inferior posterior lobe, lobules VIIIA-IX) and two dentate nucleus seeds (dorsal and ventral). Compared to controls, people with FRDA showed significantly reduced connectivity between the anterior cerebellum and bilateral pre/postcentral gyri, and between the superior posterior cerebellum and left dorsolateral PFC. Greater disease severity correlated with lower connectivity in these circuits. Lower anterior cerebellum-motor cortex functional connectivity also correlated with slower speeded finger tapping and less fractional anisotropy in the superior cerebellar peduncles, internal capsule, and precentral white matter in the FRDA cohort. There were no significant between-group differences in inferior posterior cerebellar or dentate nucleus connectivity. This study indicates that altered cerebello-cerebral functional connectivity is associated with functional status and white matter damage in cerebellar efferent pathways in people with FRDA, particularly in motor circuits.

Social concepts and the cerebellum: behavioural and functional connectivity signatures in cerebellar ataxic patients

Neurocognitive research on social concepts underscores their reliance on fronto-temporo-limbic regions mediating broad socio-cognitive skills. Yet, the field has neglected another structure increasingly implicated in social cognition: the cerebellum. The present exploratory study examines this link combining a novel naturalistic text paradigm, a relevant atrophy model and functional magnetic resonance imaging. Fifteen cerebellar ataxia (CA) patients with focal cerebellar atrophy and 29 matched controls listened to a social text (highlighting interpersonal events) as well as a non-social text (focused on a single person's actions), and answered comprehension questionnaires. We compared behavioural outcomes between groups and examined their association with cerebellar connectivity. CA patients showed deficits in social text comprehension and normal scores in the non-social text. Also, social text outcomes in controls selectively correlated with connectivity between the cerebellum and key regions subserving multi-modal semantics and social cognition, including the superior and medial temporal gyri, the temporal pole and the insula. Conversely, brain-behaviour associations involving the cerebellum were abolished in the patients. Thus, cerebellar structures and connections seem involved in processing social concepts evoked by naturalistic discourse. Such findings invite new theoretical and translational developments integrating social neuroscience with embodied semantics. This article is part of the theme issue 'Concepts in interaction: social engagement and inner experiences'.

A natural history study to track brain and spinal cord changes in individuals with Friedreich's ataxia: TRACK-FA study protocol

INTRODUCTION

Drug development for neurodegenerative diseases such as Friedreich's ataxia (FRDA) is limited by a lack of validated, sensitive biomarkers of pharmacodynamic response in affected tissue and disease progression. Studies employing neuroimaging measures to track FRDA have thus far been limited by their small sample sizes and limited follow up. TRACK-FA, a longitudinal, multi-site, and multi-modal neuroimaging natural history study, aims to address these shortcomings by enabling better understanding of underlying pathology and identifying sensitive, clinical trial ready, neuroimaging biomarkers for FRDA.

METHODS

200 individuals with FRDA and 104 control participants will be recruited across seven international study sites. Inclusion criteria for participants with genetically confirmed FRDA involves, age of disease onset ≤ 25 years, Friedreich's Ataxia Rating Scale (FARS) functional staging score of ≤ 5, and a total modified FARS (mFARS) score of ≤ 65 upon enrolment. The control cohort is matched to the FRDA cohort for age, sex, handedness, and years of education. Participants will be evaluated at three study visits over two years. Each visit comprises of a harmonized multimodal Magnetic Resonance Imaging (MRI) and Spectroscopy (MRS) scan of the brain and spinal cord; clinical, cognitive, mood and speech assessments and collection of a blood sample. Primary outcome measures, informed by previous neuroimaging studies, include measures of: spinal cord and brain morphometry, spinal cord and brain microstructure (measured using diffusion MRI), brain iron accumulation (using Quantitative Susceptibility Mapping) and spinal cord biochemistry (using MRS). Secondary and exploratory outcome measures include clinical, cognitive assessments and blood biomarkers.

DISCUSSION

Prioritising immediate areas of need, TRACK-FA aims to deliver a set of sensitive, clinical trial-ready neuroimaging biomarkers to accelerate drug discovery efforts and better understand disease trajectory. Once validated, these potential pharmacodynamic biomarkers can be used to measure the efficacy of new therapeutics in forestalling disease progression.

CLINICAL TRIAL REGISTRATION

ClinicalTrails.gov Identifier: NCT04349514.

Increased brain tissue sodium concentration in Friedreich ataxia: A multimodal MR imaging study

In patients with Friedreich ataxia, structural MRI is typically used to detect abnormalities primarily in the brainstem, cerebellum, and spinal cord. The aim of the present study was to additionally investigate possible metabolic changes in Friedreich ataxia using in vivo sodium MRI that may precede macroanatomical alterations, and to explore potential associations with clinical parameters of disease progression. Tissue sodium concentration across the whole brain was estimated from sodium MRI maps acquired at 3 T and compared between 24 patients with Friedreich ataxia (21-57 years old, 13 females) and 23 controls (21-60 years old, 12 females). Tensor-based morphometry was used to assess volumetric changes. Total sodium concentrations and volumetric data in brainstem and cerebellum were correlated with clinical parameters, such as severity of ataxia, activity of daily living and disability stage, age, age at onset, and disease duration. Compared to controls, patients showed reduced brain volume in the right cerebellar lobules I-V (difference in means: -0.039% of total intracranial volume [TICV]; Cohen's d = 0.83), cerebellar white matter (WM) (-0.105%TICV; d = 1.16), and brainstem (-0.167%TICV; d = 1.22), including pons (-0.102%TICV; d = 1.00), medulla (-0.036%TICV; d = 1.72), and midbrain (-0.028%TICV; d = 1.05). Increased sodium concentration was additionally detected in the total cerebellum (difference in means: 2.865 mmol; d = 0.68), and in several subregions with highest effect sizes in left (5.284 mmol; d = 1.01) and right cerebellar lobules I-V (5.456 mmol; d = 1.00), followed by increases in the vermis (4.261 mmol; d = 0.72), and in left (2.988 mmol; d = 0.67) and right lobules VI-VII (2.816 mmol; d = 0.68). In addition, sodium increases were also detected in all brainstem areas (3.807 mmol; d = 0.71 to 5.42 mmol; d = 1.19). After controlling for age, elevated total sodium concentrations in right cerebellar lobules IV were associated with younger age at onset (r = -0.43) and accordingly with longer disease duration in patients (r = 0.43). Our findings support the potential of in vivo sodium MRI to detect metabolic changes of increased total sodium concentration in the cerebellum and brainstem, the key regions in Friedreich ataxia. In addition to structural changes, sodium changes were present in cerebellar hemispheres and vermis without concomitant significant atrophy. Given the association with age at disease onset or disease duration, metabolic changes should be further investigated longitudinally and in larger cohorts of early disease stages to determine the usefulness of sodium MRI as a biomarker for early neuropathological changes in Friedreich ataxia and efficacy measure for future clinical trials.

The CCAS-scale in hereditary ataxias: helpful on the group level, particularly in SCA3, but limited in individual patients

Background

A brief bedside test has recently been introduced by Hoche et al. (Brain, 2018) to screen for the Cerebellar Cognitive Affective Syndrome (CCAS) in patients with cerebellar disease.

Objective

This multicenter study tested the ability of the CCAS-Scale to diagnose CCAS in individual patients with common forms of hereditary ataxia.

Methods

A German version of the CCAS-Scale was applied in 30 SCA3, 14 SCA6 and 20 FRDA patients, and 64 healthy participants matched for age, sex, and level of education. Based on original cut-off values, the number of failed test items was assessed, and CCAS was considered possible (one failed item), probable (two failed items) or definite (three failed items). In addition a total sum raw score was calculated.

Results

On a group level, failed items were significantly higher and total sum scores were significantly lower in SCA3 patients compared to matched controls. SCA6 and FRDA patients performed numerically below controls, but respective group differences failed to reach significance. The ability of the CCAS-Scale to diagnose CCAS in individual patients was limited to severe cases failing three or more items. Milder cases failing one or two items showed a great overlap with the performance of controls exhibiting a substantial number of false-positive test results. The word fluency test items differentiated best between patients and controls.

Conclusions

As a group, SCA3 patients performed below the level of SCA6 and FRDA patients, possibly reflecting additional cerebral involvement. Moreover, the application of the CCAS-Scale in its present form results in a high number of false-positive test results, that is identifying controls as patients, reducing its usefulness as a screening tool for CCAS in individual patients.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00415-022-11071-5.

The cognitive profile of Friedreich ataxia: a systematic review and meta-analysis

BACKGROUND

Study the cognitive profile of individuals with Friedreich ataxia (FRDA) and seek evidence for correlations between clinical, genetic and imaging characteristics and neuropsychological impairments.

METHODS

Based on PRISMA guidelines, a meta-analysis was realized using the Pubmed and Scopus databases to identify studies (1950-2021) reporting neuropsychological test results in genetically confirmed FRDA and control participants in at least one of the following cognitive domains: attention/executive, language, memory and visuo-spatial functions as well as emotion. Studies using identical outcomes in a minimum of two studies were pooled. Pooled effect sizes were calculated with Cohen's d.

RESULTS

Eighteen studies were included. Individuals with FRDA displayed significantly lower performance than individuals without FRDA in most language, attention, executive function, memory visuospatial function, emotion regulation and social cognitive tasks. Among the included studies, thirteen studies examined the relationship between neuropsychological test results and clinical parameters and reported significant association with disease severity and six studies reviewed the relationship between neuroimaging measures and cognitive performance and mainly reported links between reduced cognitive performance and changes in cerebellar structure.

CONCLUSIONS

Individuals with FRDA display significantly lower performances in many cognitive domains compared to control participants. The spectrum of the cognitive profile alterations in FRDA and its correlation with disease severity and cerebellar structural parameters suggest a cerebellar role in the pathophysiology of FRDA cognitive impairments.

Functional MRI Studies in Friedreich's Ataxia: A Systematic Review

Friedreich's ataxia (FRDA) is an inherited neurodegenerative movement disorder with early onset, widespread cerebral and cerebellar pathology, and no cure still available. Functional MRI (fMRI) studies, although currently limited in number, have provided a better understanding of brain changes in people with FRDA. This systematic review aimed to provide a critical overview of the findings and methodologies of all fMRI studies conducted in genetically confirmed FRDA so far, and to offer recommendations for future study designs. About 12 cross-sectional and longitudinal fMRI studies, included 198 FRDA children and young adult patients and, 205 healthy controls (HCs), according to the inclusion criteria. Details regarding GAA triplet expansion and demographic and clinical severity measures were widely reported. fMRI designs included motor and cognitive task paradigms, and resting-state studies, with widespread changes in functionally activated areas and extensive variability in study methodologies. These studies highlight a mixed picture of both hypoactivation and hyperactivation in different cerebral and cerebellar brain regions depending on fMRI design and cohort characteristics. Functional changes often correlate with clinical variables. In aggregate, the findings provide support for cerebro-cerebellar loop damage and the compensatory mechanism hypothesis. Current literature indicates that fMRI is a valuable tool for gaining in vivo insights into FRDA pathology, but addressing that its limitations would be a key to improving the design, interpretation, and generalizability of studies in the future.

Longitudinal investigation of brain activation during motor tasks in Friedreich ataxia: 24-month data from IMAGE-FRDA

Friedreich ataxia (FRDA) is a progressive autosomal recessive disease. While motor dysfunction is the primary neurological hallmark, little is known about the underlying neurobiological changes associated with motor deficits over the course of disease. We investigated the hypothesis that progressive functional changes in both the cerebellum and cerebrum are related to longitudinal changes in performance on complex motor tasks in individuals with FRDA. Twenty-two individuals with FRDA and 28 controls participated over 24 months. The longitudinal investigation included finger tapping tasks with different levels of complexity (i.e., visually cued, multi-finger; self-paced, single finger), performed in conjunction with fMRI acquisitions, to interrogate changes in the neurobiology of motor and attentional brain networks including the cerebellum and cerebrum. We demonstrated evidence for significant longitudinal decreased cerebral fMRI activity over time in individuals with FRDA, relative to controls, during an attentionally-demanding motor task (visually cued tapping of multiple fingers) in six cerebral regions: right and left superior frontal gyri, right superior temporal gyrus, right primary somatosensory area, right anterior cingulate cortex, and right medial frontal gyrus. Importantly, longitudinal decreased activity was associated with more severe disease status at baseline, higher GAA1 repeat length and earlier age of onset. These findings suggest a dynamic pattern of neuronal activity in motor, attention and executive control networks over time in individuals with FRDA, which is associated with increased disease severity at baseline, increased GAA1 repeat length and earlier age at onset.

Central Nervous System Therapeutic Targets in Friedreich Ataxia

Friedreich ataxia (FRDA) is an autosomal recessive inherited multisystem disease, characterized by marked differences in the vulnerability of neuronal systems. In general, the proprioceptive system appears to be affected early, while later in the disease, the dentate nucleus of the cerebellum and, to some degree, the corticospinal tracts degenerate. In the current era of expanding therapeutic discovery in FRDA, including progress toward novel gene therapies, a deeper and more specific consideration of potential treatment targets in the nervous system is necessary. In this work, we have re-examined the neuropathology of FRDA, recognizing new issues superimposed on classical findings, and dissected the peripheral nervous system (PNS) and central nervous system (CNS) aspects of the disease and the affected cell types. Understanding the temporal course of neuropathological changes is needed to identify areas of modifiable disease progression and the CNS and PNS locations that can be targeted at different time points. As most major targets of long-term therapy are in the CNS, this review uses multiple tools for evaluation of the importance of specific CNS locations as targets. In addition to clinical observations, the conceptualizations in this study include physiological, pathological, and imaging approaches, and animal models. We believe that this review, through analysis of a more complete set of data derived from multiple techniques, provides a comprehensive summary of therapeutic targets in FRDA.

Brain Structure and Degeneration Staging in Friedreich Ataxia: Magnetic Resonance Imaging Volumetrics from the ENIGMA-Ataxia Working Group

Objective

Friedreich ataxia (FRDA) is an inherited neurological disease defined by progressive movement incoordination. We undertook a comprehensive characterization of the spatial profile and progressive evolution of structural brain abnormalities in people with FRDA.

Methods

A coordinated international analysis of regional brain volume using magnetic resonance imaging data charted the whole‐brain profile, interindividual variability, and temporal staging of structural brain differences in 248 individuals with FRDA and 262 healthy controls.

Results

The brainstem, dentate nucleus region, and superior and inferior cerebellar peduncles showed the greatest reductions in volume relative to controls (Cohen d = 1.5–2.6). Cerebellar gray matter alterations were most pronounced in lobules I–VI (d = 0.8), whereas cerebral differences occurred most prominently in precentral gyri (d = 0.6) and corticospinal tracts (d = 1.4). Earlier onset age predicted less volume in the motor cerebellum (r_max = 0.35) and peduncles (r_max = 0.36). Disease duration and severity correlated with volume deficits in the dentate nucleus region, brainstem, and superior/inferior cerebellar peduncles (r_max = −0.49); subgrouping showed these to be robust and early features of FRDA, and strong candidates for further biomarker validation. Cerebral white matter abnormalities, particularly in corticospinal pathways, emerge as intermediate disease features. Cerebellar and cerebral gray matter loss, principally targeting motor and sensory systems, preferentially manifests later in the disease course.

Interpretation

FRDA is defined by an evolving spatial profile of neuroanatomical changes beyond primary pathology in the cerebellum and spinal cord, in line with its progressive clinical course. The design, interpretation, and generalization of research studies and clinical trials must consider neuroanatomical staging and associated interindividual variability in brain measures. ANN NEUROL 2021;90:570–583

Longitudinal structural brain changes in Friedreich ataxia depend on disease severity: the IMAGE-FRDA study

BACKGROUND

Friedreich ataxia is an inherited neurodegenerative disease, with cerebral and cerebellar pathology evident. Despite an increased understanding of its neuropathology, disease progression in this disease remains poorly understood. This study aimed to characterise longitudinal change in brain structure using a multi-modal approach across cerebral and cerebellar grey and white matter.

METHODS

T1-weighted, diffusion-tensor, and magnetisation transfer magnetic resonance images were obtained from 28 individuals with Friedreich ataxia and 29 age- and gender-matched controls at two time-points, 2 years apart. Region-of-interest and exploratory between-group comparisons assessed changes in brain macrostructure (cerebellar lobule volume, cerebral cortical thickness/gyrification, brain white matter volume) and microstructure (white matter fractional anisotropy, mean/axial/radial diffusivity, magnetisation transfer ratio). Rates of change were correlated against change in neurological severity, Time 1 severity, and onset age.

RESULTS

Individuals with Friedreich ataxia had a greater rate of white matter volume loss than controls in the superior cerebellar peduncles and right peri-thalamic/posterior cerebral regions, and greater reduction in left primary motor cortex gyrification. Greater cerebellar/brainstem white matter volume loss and right dorsal premotor gyrification loss was observed amongst individuals with less severe neurological symptoms at Time 1. Conversely, cerebral atrophy and changes in axial diffusivity were observed in individuals with more severe Time 1 symptoms. Progression in radial diffusivity was more pronounced amongst individuals with earlier disease onset. Greater right ventral premotor gyrification loss correlated with greater neurological progression.

CONCLUSION

Heterogeneity in Friedreich ataxia progression is observed at the neurobiological level, with evidence of earlier cerebellar and later cerebral degeneration.

Longitudinal Study of Cognitive Functioning in Friedreich's Ataxia

OBJECTIVE

Friedreich's ataxia (FRDA) is the most common hereditary ataxia. It is a neurodegenerative disorder, characterized by progressive ataxia. FRDA is also associated with cognitive impairments. To date, the evolution of cognitive functioning is unknown. Our aim was to investigate the changes in the cognitive functioning of FRDA patients over an average eight-year timeframe. In addition, we aimed to study the relationship between cognitive changes and clinical variables.

METHODS

Twenty-nine FRDA patients who had been part of the sample of a previous study participated in the present study. The mean average time between the two assessments was 8.24 years. The participants completed an extensive battery of neuropsychological tests chosen to examine cognitive functioning in various cognitive domains: processing speed, attention, working memory, executive functions, verbal and visual memory, visuoperceptive and visuospatial skills, visuoconstructive functions and language.

RESULTS

At follow-up, cerebellar symptoms had worsened, and patients presented greater disability. Differences between baseline and follow-up were observed in motor and cognitive reaction times, several trials of the Stroop test, semantic fluency, and block designs. No other cognitive changes were observed. Deterioration in simple cognitive reactions times and block designs performance correlated with the progression of cerebellar symptoms.

CONCLUSIONS

Our study has demonstrated for the first time that patients with FRDA experience a significant decline over time in several cognitive domains. Specifically, after an eight-year period, FRDA patients worsened in processing speed, fluency, and visuoconstructive skills. This progression is unlikely to be due to greater motor or speech impairment.

Emotional disorders and the cerebellum: Neurobiological substrates, neuropsychiatry, and therapeutic implications

The notion that the cerebellum is devoted exclusively to motor control has been replaced by a more sophisticated understanding of its role in neurological function, one that includes cognition and emotion. Early clinical reports, as well as physiological and behavioral studies in animal models, raised the possibility of a nonmotor role for the cerebellum. Anatomical studies demonstrate cerebellar connectivity with the distributed neural circuits linked with autonomic, sensorimotor, vestibular, associative, and limbic/paralimbic brain areas. Identification of the cerebellar cognitive affective syndrome in adults and children underscored the clinical relevance of the role of the cerebellum in cognition and emotion. It opened new avenues of investigation into higher-order deficits that accompany the ataxias and other cerebellar diseases, as well as the contribution of cerebellar dysfunction to neuropsychiatric and neurocognitive disorders. Brain imaging studies have demonstrated the complexity of cerebellar functional topography, revealing a double representation of the sensorimotor cerebellum in the anterior lobe and lobule VIII and a triple cognitive representation in the cerebellar posterior lobe, as well as representation in the cerebellum of the intrinsic connectivity networks identified in the cerebral hemispheres. This paradigm shift in thinking about the cerebellum has been advanced by the theories of dysmetria of thought and the universal cerebellar transform, harmonizing the dual anatomic realities of homogeneously repeating cerebellar cortical microcircuitry set against the heterogeneous and topographically arranged cerebellar connections with extracerebellar structures. This new appreciation of cerebellar incorporation into circuits that subserve cognition and emotion mandates a deeper understanding of the cerebellum by practitioners in behavioral neurology and neuropsychiatry because it impacts the understanding and diagnosis of disorders of emotion and intellect and has potential for novel cerebellar-based approaches to therapy.

Longitudinal Increases in Cerebral Brain Activation During Working Memory Performance in Friedreich Ataxia: 24-Month Data from IMAGE-FRDA

Friedreich ataxia (FRDA) has been associated with functional abnormalities in cerebral and cerebellar networks, particularly in the ventral attention network. However, how functional alterations change with disease progression remains largely unknown. Longitudinal changes in brain activation, associated with working memory performance (N-back task), and grey matter volume were assessed over 24 months in 21 individuals with FRDA and 28 healthy controls using functional and structural magnetic resonance imaging, respectively. Participants also completed a neurocognitive battery assessing working memory (digit span), executive function (Stroop, Haylings), and set-shifting (Trail Making Test). Individuals with FRDA displayed significantly increased brain activation over 24 months in ventral attention brain regions, including bilateral insula and inferior frontal gyrus (pars triangularis and pars opercularis), compared with controls, but there was no difference in working memory (N-back) performance between groups. Moreover, there were no significant differences in grey matter volume changes between groups. Significant correlations between brain activations and both clinical severity and age at disease onset were observed in FRDA individuals only at 24 months. There was significant longitudinal decline in Trail Making Test (TMT) difference score (B-A) in individuals with FRDA, compared with controls. These findings provide the first evidence of increased longitudinal activation over time in the cerebral cortex in FRDA, compared with controls, despite comparable working memory performance. This finding represents a possible compensatory response in the ventral attention network to help sustain working memory performance in individuals with FRDA.

Cerebellar cognitive disorder parallels cerebellar motor symptoms in Friedreich ataxia

Dentate nuclei (DN) are involved in cerebellar modulation of motor and cognitive functions, whose impairment causes ataxia and cerebellar cognitive affective syndrome (CCAS). Friedreich ataxia (FRDA) disease progression relates to degeneration of the dentate nucleus and dentato‐thalamic pathways, causing cerebellar ataxia. Volumetric MRI also shows mild loss in the cerebellar cortex, brainstem, and motor cortex. Cognitive deficits occur in FRDA, but their relationship with ataxia progression is not fully characterized. We found a significant positive correlation between severity of patients’ ataxia and more marked CCAS as assessed with the CCAS‐Scale. This relation could be related to progressive DN impairment.

Multiple mechanisms underpin cerebral and cerebellar white matter deficits in Friedreich ataxia: The IMAGE-FRDA study

Friedreich ataxia is a progressive neurodegenerative disorder with reported abnormalities in cerebellar, brainstem, and cerebral white matter. White matter structure can be measured using in vivo neuroimaging indices sensitive to different white matter features. For the first time, we examined the relative sensitivity and relationship between multiple white matter indices in Friedreich ataxia to more richly characterize disease expression and infer possible mechanisms underlying the observed white matter abnormalities. Diffusion-tensor, magnetization transfer, and T1-weighted structural images were acquired from 31 individuals with Friedreich ataxia and 36 controls. Six white matter indices were extracted: fractional anisotropy, diffusivity (mean, axial, radial), magnetization transfer ratio (microstructure), and volume (macrostructure). For each index, whole-brain voxel-wise between-group comparisons and correlations with disease severity, onset age, and gene triplet-repeat length were undertaken. Correlations between pairs of indices were assessed in the Friedreich ataxia cohort. Spatial similarities in the voxel-level pattern of between-group differences across the indices were also assessed. Microstructural abnormalities were maximal in cerebellar and brainstem regions, but evident throughout the brain, while macroscopic abnormalities were restricted to the brainstem. Poorer microstructure and reduced macrostructural volume correlated with greater disease severity and earlier onset, particularly in peri-dentate nuclei and brainstem regions. Microstructural and macrostructural abnormalities were largely independent. Reduced fractional anisotropy was most strongly associated with axial diffusivity in cerebral tracts, and magnetization transfer in cerebellar tracts. Multiple mechanisms likely underpin white matter abnormalities in Friedreich ataxia, with differential impacts in cerebellar and cerebral pathways.

Resistance, vulnerability and resilience: A review of the cognitive cerebellum in aging and neurodegenerative diseases

In the context of neurodegeneration and aging, the cerebellum is an enigma. Genetic markers of cellular aging in cerebellum accumulate more slowly than in the rest of the brain, and it generates unknown factors that may slow or even reverse neurodegenerative pathology in animal models of Alzheimer's Disease (AD). Cerebellum shows increased activity in early AD and Parkinson's disease (PD), suggesting a compensatory function that may mitigate early symptoms of neurodegenerative pathophysiology. Perhaps most notably, different parts of the brain accumulate neuropathological markers of AD in a recognized progression and generally, cerebellum is the last brain region to do so. Taken together, these data suggest that cerebellum may be resistant to certain neurodegenerative mechanisms. On the other hand, in some contexts of accelerated neurodegeneration, such as that seen in chronic traumatic encephalopathy (CTE) following repeated traumatic brain injury (TBI), the cerebellum appears to be one of the most susceptible brain regions to injury and one of the first to exhibit signs of pathology. Cerebellar pathology in neurodegenerative disorders is strongly associated with cognitive dysfunction. In neurodegenerative or neurological disorders associated with cerebellar pathology, such as spinocerebellar ataxia, cerebellar cortical atrophy, and essential tremor, rates of cognitive dysfunction, dementia and neuropsychiatric symptoms increase. When the cerebellum shows AD pathology, such as in familial AD, it is associated with earlier onset and greater severity of disease. These data suggest that when neurodegenerative processes are active in the cerebellum, it may contribute to pathological behavioral outcomes. The cerebellum is well known for comparing internal representations of information with observed outcomes and providing real-time feedback to cortical regions, a critical function that is disturbed in neuropsychiatric disorders such as intellectual disability, schizophrenia, dementia, and autism, and required for cognitive domains such as working memory. While cerebellum has reciprocal connections with non-motor brain regions and likely plays a role in complex, goal-directed behaviors, it has proven difficult to establish what it does mechanistically to modulate these behaviors. Due to this lack of understanding, it's not surprising to see the cerebellum reflexively dismissed or even ignored in basic and translational neuropsychiatric literature. The overarching goals of this review are to answer the following questions from primary literature: When the cerebellum is affected by pathology, is it associated with decreased cognitive function? When it is intact, does it play a compensatory or protective role in maintaining cognitive function? Are there theoretical frameworks for understanding the role of cerebellum in cognition, and perhaps, illnesses characterized by cognitive dysfunction? Understanding the role of the cognitive cerebellum in neurodegenerative diseases has the potential to offer insight into origins of cognitive deficits in other neuropsychiatric disorders, which are often underappreciated, poorly understood, and not often treated.

The Cerebellar Cognitive Affective/Schmahmann Syndrome: a Task Force Paper

Sporadically advocated over the last two centuries, a cerebellar role in cognition and affect has been rigorously established in the past few decades. In the clinical domain, such progress is epitomized by the "cerebellar cognitive affective syndrome" ("CCAS") or "Schmahmann syndrome." Introduced in the late 1990s, CCAS reflects a constellation of cerebellar-induced sequelae, comprising deficits in executive function, visuospatial cognition, emotion-affect, and language, over and above speech. The CCAS thus offers excellent grounds to investigate the functional topography of the cerebellum, and, ultimately, illustrate the precise mechanisms by which the cerebellum modulates cognition and affect. The primary objective of this task force paper is thus to stimulate further research in this area. After providing an up-to-date overview of the fundamental findings on cerebellar neurocognition, the paper substantiates the concept of CCAS with recent evidence from different scientific angles, promotes awareness of the CCAS as a clinical entity, and examines our current insight into the therapeutic options available. The paper finally identifies topics of divergence and outstanding questions for further research.

Neurochemical profiles in hereditary ataxias: A meta-analysis of Magnetic Resonance Spectroscopy studies

Magnetic resonance spectroscopy (MRS) is applied to investigate the neurochemical profiles of degenerative hereditary ataxias. This meta-analysis provides a quantitative review and reappraisal of MRS findings in spinocerebellar ataxias (SCA) and Friedreich ataxia (FA) available to date. From each study, changes in N-acetyl aspartate (NAA), choline-containing compounds (Cho) and myo-Inositol (mI) ratios to total creatine (Cr) were calculated for groups of patients (1499 patients in total: SCA1 = 223, SCA2 = 298, SCA3 = 711, SCA6 = 165, and FA = 102) relative to their own control group, mostly in cerebellum and pons. SCA1, 2, 3, 6, and FA patients showed overall decreased NAA/Cr compared to controls. Decreased Cho/Cr was visible in SCA1, 2, and 3 and elevated mI/Cr in SCA2 patients in cerebellum. In SCA6 and FA Cho/Cr and mI/Cr did not differ with respect to controls but SCA6 patients indicated higher Cho/Cr compared to SCA1 patients in cerebellum. SCA2 subjects showed the lowest NAA/Cr and Cho/Cr in cerebellum and the highest mI/Cr compared to controls and other genotypes, and therefore the most promising results for a potential biomarker.

Pattern of Cerebellar Atrophy in Friedreich's Ataxia-Using the SUIT Template

Whole-brain voxel-based morphometry (VBM) studies revealed patterns of patchy atrophy within the cerebellum of Friedreich's ataxia patients, missing clear clinico-anatomic correlations. Studies so far are lacking an appropriate registration to the infratentorial space. To circumvent these limitations, we applied a high-resolution atlas template of the human cerebellum and brainstem (SUIT template) to characterize regional cerebellar atrophy in Friedreich's ataxia (FRDA) on 3-T MRI data. We used a spatially unbiased voxel-based morphometry approach together with T2-based manual segmentation, T2 histogram analysis, and atlas generation of the dentate nuclei in a representative cohort of 18 FRDA patients and matched healthy controls. We demonstrate that the cerebellar volume in FRDA is generally not significantly different from healthy controls but mild lobular atrophy develops beyond normal aging. The medial parts of lobule VI, housing the somatotopic representation of tongue and lips, are the major site of this lobular atrophy, which possibly reflects speech impairment. Extended white matter affection correlates with disease severity across and beyond the cerebellar inflow and outflow tracts. The dentate nucleus, as a major site of cerebellar degeneration, shows a mean volume loss of about 30%. Remarkably, not the atrophy but the T2 signal decrease of the dentate nuclei highly correlates with disease duration and severity.

Protocol of a randomized, double-blind, placebo-controlled, parallel-group, multicentre study of the efficacy and safety of nicotinamide in patients with Friedreich ataxia (NICOFA)

Introduction

Currently, no treatment that delays with the progression of Friedreich ataxia is available. In the majority of patients Friedreich ataxia is caused by homozygous pathological expansion of GAA repeats in the first intron of the FXN gene. Nicotinamide acts as a histone deacetylase inhibitor. Dose escalation studies have shown, that short term treatment with dosages of up to 4 g/day increase the expression of FXN mRNA and frataxin protein up to the levels of asymptomatic heterozygous gene carriers. The long-term effects and the effects on clinical endpoints, activities of daily living and quality of life are unknown.

Methods

The aim of the NICOFA study is to investigate the efficacy and safety of nicotinamide for the treatment of Friedreich ataxia over 24 months. An open-label dose adjustment wash-in period with nicotinamide (phase A: weeks 1–4) to the individually highest tolerated dose of 2–4 g nicotinamide/day will be followed by a 2 (nicotinamide group): 1 (placebo group) randomization (phase B: weeks 5–104). In the nicotinamide group, patients will continue with their individually highest tolerated dose between 2 and 4 g/d per os once daily and the placebo group patients will be receiving matching placebo. Safety assessments will consist of monitoring and recording of all adverse events and serious adverse events, regular monitoring of haematology, blood chemistry and urine values, regular measurement of vital signs and the performance of physical examinations including cardiological signs. The primary outcome is the change in the Scale for the Assessment and Rating of Ataxia (SARA) over time as compared with placebo in patients with Friedreich ataxia based on the linear mixed effect model (LMEM) model. Secondary endpoints are measures of quality of life, functional motor and cognitive measures, clinician’s and patient’s global impression-change scales as well as the up-regulation of the frataxin protein level, safety and survival/death.

Perspective

The NICOFA study represents one of the first attempts to assess the clinical efficacy of an epigenetic therapeutic intervention for this disease and will provide evidence of possible disease modifying effects of nicotinamide treatment in patients with Friedreich ataxia.

Trial registration

EudraCT-No.: 2017-002163-17, ClinicalTrials.govNCT03761511.

The Cerebellar Cognitive Affective/Schmahmann Syndrome: a Task Force Paper

Sporadically advocated over the last two centuries, a cerebellar role in cognition and affect has been rigorously established in the past few decades. In the clinical domain, such progress is epitomized by the "cerebellar cognitive affective syndrome" ("CCAS") or "Schmahmann syndrome." Introduced in the late 1990s, CCAS reflects a constellation of cerebellar-induced sequelae, comprising deficits in executive function, visuospatial cognition, emotion-affect, and language, over and above speech. The CCAS thus offers excellent grounds to investigate the functional topography of the cerebellum, and, ultimately, illustrate the precise mechanisms by which the cerebellum modulates cognition and affect. The primary objective of this task force paper is thus to stimulate further research in this area. After providing an up-to-date overview of the fundamental findings on cerebellar neurocognition, the paper substantiates the concept of CCAS with recent evidence from different scientific angles, promotes awareness of the CCAS as a clinical entity, and examines our current insight into the therapeutic options available. The paper finally identifies topics of divergence and outstanding questions for further research.

Fourth Ventricle Enlargement in Chiari Malformation Type I

OBJECTIVE

How Chiari malformation type I (CM-I) affects posterior fossa brain structures and produces various symptoms remains unclear. The fourth ventricle is surrounded by critical structures required for normal function. The foramen of Magendie can be obstructed in CM-I; therefore, fourth ventricle changes may occur. To test this hypothesis, we assessed fourth ventricle volume in CM-I compared with healthy controls.

METHODS

Using our database from 2007-2016, we studied 72 patients with CM-I and 30 age-matched healthy control subjects. Fourth and lateral ventricle volumes and posterior fossa volumes (PFV) were assessed and correlated with clinical signs and symptoms. Statistical analysis was performed.

RESULTS

Patients with CM-I had larger fourth ventricle volumes compared with control subjects (1.31 vs. 0.95 mL; P = 0.012). There were no differences in lateral ventricle volume or PFV. CM-I fourth ventricle volume was associated with tonsillar descent (P = 0.030). CM-I fourth ventricle volume variance was larger than healthy controls (F_71,29 = 8.33; P < 0.0001). Patients with CM-I with severe signs and symptoms had a significantly larger fourth ventricle than patients with CM-I with mild signs and symptoms (1.565 vs. 1.015 mL; P = 0.0002).

CONCLUSIONS

The fourth ventricle can be enlarged in CM-I independent of lateral ventricle size and is associated with greater tonsillar descent. Most importantly, fourth ventricle enlargement was associated with a worse clinical and radiographic presentation independent of PFV. Fourth ventricle enlargement can affect critical structures and may be a mechanism contributing to symptoms unexplained by tonsil descent. Fourth ventricle enlargement is a useful adjunct in assessing CM-I.

The Cerebellum in Frontotemporal Dementia: a Meta-Analysis of Neuroimaging Studies

Frontotemporal dementia (FTD) is a neurodegenerative brain disorder primarily affecting the frontal and/or temporal lobes. Three main subtypes have been recognized: behavioural-variant FTD (bvFTD), semantic dementia (SD), and progressive nonfluent aphasia (PNFA), each of which has a distinct clinical and cognitive profile. Although the role of the cerebellum in cognition is increasingly accepted, knowledge of cerebellar changes across neuroimaging modalities and their contribution to behavioural and cognitive changes in FTD syndromes is currently scant. We conducted an anatomical/activation likelihood estimation (ALE) meta-analysis in 53 neuroimaging studies (structural MRI: 42; positron emission tomography: 6; functional MRI: 4; single-photon emission computed tomography: 1) to identify the patterns of cerebellar changes and their relations to profiles of behavioural and cognitive deficits in FTD syndromes. Overall, widespread bilateral cerebellar changes were found in FTD and notably the patterns were subtype specific. In bvFTD, ALE peaks were identified in the bilateral Crus, left lobule VI, right lobules VIIb and VIIIb. In SD, focal cerebellar changes were located in the left Crus I and lobule VI. A separate ALE meta-analysis on PNFA studies was not performed due to the limited number of studies available. In addition, the ALE analysis indicated that bilateral Crus I and Crus II were associated with behavioural disruption and cognitive dysfunction. This ALE meta-analysis provides the quantification of the location and extent of cerebellar changes across the main FTD syndromes, which in turn provides evidence of cerebellar contributions to behavioural and cognitive changes in FTD. These results bring new insights into the mechanisms mediating FTD symptomatology.

Emotion Recognition and Psychological Comorbidity in Friedreich's Ataxia

Friedreich's ataxia (FRDA) is an autosomal recessive disease presenting with ataxia, corticospinal signs, peripheral neuropathy, and cardiac abnormalities. Little effort has been made to understand the psychological and emotional burden of the disease. The aim of our study was to measure patients' ability to recognize emotions using visual and non-verbal auditory hints, and to correlate this ability with psychological, neuropsychological, and neurological variables. We included 20 patients with FRDA, and 20 age, sex, and education matched healthy controls (HC). We measured emotion recognition using the Geneva Emotion Recognition Test (GERT). Neuropsychological status was assessed measuring memory, executive functions, and prosopagnosia. Psychological tests were Patient Health Questionnaire-9 (PHQ-9), State Trait Anxiety Inventory-state/-trait (STAI-S/-T), and Structured Clinical Interview for DSM Disorders II. FRDA patients scored worse at the global assessment and showed impaired immediate visuospatial memory and executive functions. Patients presented lower STAI-S scores, and similar scores at the STAI-T, and PHQ-9 as compared to HC. Three patients were identified with personality disorders. Emotion recognition was impaired in FRDA with 29% reduction at the total GERT score (95% CI - 44.8%, - 12.6%; p < 0.001; Cohen's d = 1.2). Variables associated with poor GERT scores were the 10/36 spatial recall test, the Ray Auditory Verbal Learning Test, the Montreal Cognitive Assessment, and the STAI-T (R² = 0.906; p < 0.001). FRDA patients have impaired emotion recognition that may be secondary to neuropsychological impairment. Depression and anxiety were not higher in FRDA as compared to HC and should not be considered as part of the disease.

Personality and Neuropsychological Profiles in Friedreich Ataxia

Friedreich ataxia, an autosomal recessive mitochondrial disease, is the most frequent inherited ataxia. Many studies have attempted to identify cognitive and affective changes associated with the disease, but conflicting results have been obtained, depending on the tests used and because many of the samples studied were very small. We investigated personality and neuropsychological characteristics in a cohort of 47 patients with genetically confirmed disease. The neuropsychological battery assessed multiple cognition domains: processing speed, attention, working memory, executive functions, verbal memory, vocabulary, visual reasoning, emotional recognition, and social cognition. Personality was assessed with the Temperament and Character Inventory, and depressive symptoms were assessed with the Beck Depression Inventory. We found deficits of sustained attention, processing speed, semantic capacities, and verbal fluency only partly attributable to motor deficit or depressed mood. Visual reasoning, memory, and learning were preserved. Emotional processes and social cognition were unimpaired. We also detected a change in automatic processes, such as reading. Personality traits were characterized by high persistence and low self-transcendence. The mild cognitive impairment observed may be a developmental rather than degenerative problem, due to early cerebellum dysfunction, with the impairment of cognitive and emotional processing. Disease manifestations at crucial times for personality development may also have an important impact on personality traits.

Neuroimaging Applications in Chronic Ataxias

Magnetic resonance imaging (MRI), single photon emission computed tomography (SPECT) and positron emission tomography (PET) are the main instruments for neuroimaging investigation of patients with chronic ataxia. MRI has a predominant diagnostic role in the single patient, based on the visual detection of three patterns of atrophy, namely, spinal atrophy, cortical cerebellar atrophy and olivopontocerebellar atrophy, which correlate with the aetiologies of inherited or sporadic ataxia. In fact spinal atrophy is observed in Friedreich ataxia, cortical cerebellar atrophy in Ataxia Telangectasia, gluten ataxia and Sporadic Adult Onset Ataxia and olivopontocerebellar atrophy in Multiple System Atrophy cerebellar type. The 39 types of dominantly inherited spinocerebellar ataxias show either cortical cerebellar atrophy or olivopontocerebellar atrophy. T2 or T2* weighted MR images can contribute to the diagnosis by revealing abnormally increased or decreased signal with a characteristic distribution. These include symmetric T2 hyperintensity of the posterior and lateral columns of the cervical spinal cord in Friedreich ataxia, diffuse and symmetric hyperintensity of the cerebellar cortex in Infantile Neuro-Axonal Dystrophy, symmetric hyperintensity of the peridentate white matter in Cerebrotendineous Xanthomatosis, and symmetric hyperintensity of the middle cerebellar peduncles and peridentate white matter, cerebral white matter and corpus callosum in Fragile X Tremor Ataxia Syndrome. Abnormally decreased T2 or T2* signal can be observed with a multifocal distribution in Ataxia Telangectasia and with a symmetric distribution in the basal ganglia in Multiple System Atrophy. T2 signal hypointensity lining diffusely the outer surfaces of the brainstem, cerebellum and cerebrum enables diagnosis of superficial siderosis of the central nervous system. The diagnostic role of nuclear medicine techniques is smaller. SPECT and PET show decreased uptake of radiotracers investigating the nigrostriatal system in Multiple System Atrophy and in patients with Fragile X Tremor Ataxia Syndrome. Semiquantitative or quantitative MRI, SPECT and PET data describing structural, microstructural and functional changes of the cerebellum, brainstem, and spinal cord have been widely applied to investigate physiopathological changes in patients with chronic ataxias. Moreover they can track diseases progression with a greater sensitivity than clinical scales. So far, a few small-size and single center studies employed neuroimaging techniques as surrogate markers of treatment effects in chronic ataxias.

Functional and Structural Brain Damage in Friedreich's Ataxia

Friedreich's ataxia (FRDA) is a rare hereditary neurodegenerative disorder caused by a GAA repeat expansion in the FXN gene. There is still no cure or quantitative biomarkers reliaby correlating with the progression rate and disease severity. Investigation of functional and structural alterations characterizing white (WM) and gray matter (GM) in FRDA are needed prerequisite to monitor progression and response to treatment. Here we report the results of a multimodal cross-sectional MRI study of FRDA including Voxel-Based Morphometry (VBM), diffusion-tensor imaging (DTI), functional MRI (fMRI), and a correlation analysis with clinical severity scores. Twenty-one early-onset FRDA patients and 18 age-matched healthy controls (HCs) were imaged at 3T. All patients underwent a complete cognitive and clinical assessment with ataxia scales. VBM analysis showed GM volume reduction in FRDA compared to HCs bilaterally in lobules V, VI, VIII (L>R), as well as in the crus of cerebellum, posterior lobe of the vermis, in the flocculi and in the left tonsil. Voxel-wise DTI analysis showed a diffuse fractional anisotropy reduction and mean, radial, axial (AD) diffusivity increase in both infratentorial and supratentorial WM. ROI-based analysis confirmed the results showing differences of the same DTI metrics in cortico-spinal-tracts, forceps major, corpus callosum, posterior thalamic radiations, cerebellar penduncles. Additionally, we observed increased AD in superior (SCP) and middle cerebellar peduncles. The WM findings correlated with age at onset (AAO), short-allelle GAA, and disease severity. The intragroup analysis of fMRI data from right-handed 14 FRDA and 15 HCs showed similar findings in both groups, including activation in M1, insula and superior cerebellar hemisphere (lobules V-VIII). Significant differences emerged only during the non-dominant hand movement, with HCs showing a stronger activation in the left superior cerebellar hemisphere compared to FRDA. Significant correlations were found between AAO and the fMRI activation in cerebellar anterior and posterior lobes, insula and temporal lobe. Our multimodal neuroimaging protocol suggests that MRI is a useful tool to document the extension of the neurological impairment in FRDA.

Nonataxia symptoms in Friedreich Ataxia: Report from the Registry of the European Friedreich's Ataxia Consortium for Translational Studies (EFACTS)

OBJECTIVE

To provide a systematic evaluation of the broad clinical variability in Friedreich ataxia (FRDA), a multisystem disorder presenting mainly with afferent ataxia but also a complex phenotype of nonataxia symptoms.

METHODS

From the large database of the European Friedreich's Ataxia Consortium for Translational Studies, 650 patients with genetically confirmed FRDA were included. Detailed data of medical history documentation, questionnaires, and reports on clinical features were analyzed to provide in-depth description of the clinical profile and frequency rates of phenotypical features with a focus on differences between typical-onset and late-onset FRDA. Logistic regression modeling was used to identify predictors for the presence of the most common clinical features.

RESULTS

The most frequent clinical features beyond afferent ataxia were abnormal eye movements (90.5%), scoliosis (73.5%), deformities of the feet (58.8%), urinary dysfunction (42.8%), cardiomyopathy and cardiac hypertrophy (40.3%), followed by decreased visual acuity (36.8%); less frequent features were, among others, depression (14.1%) and diabetes (7.1%). Most of these features were more common in the typical-onset group compared to the late-onset group. Logistic regression models for the presence of these symptoms demonstrated the predictive value of GAA repeat length on the shorter allele and age at onset, but also severity of ataxia signs, sex, and presence of neonatal problems.

CONCLUSIONS

This joint European effort demonstrates the multisystem nature of this neurodegenerative disease encompassing most the central nervous, neuromuscular, cardiologic, and sensory systems. A distinct and deeper knowledge of this rare and chronic disease is highly relevant for clinical practice and designs of clinical trials.

Action Semantics at the Bottom of the Brain: Insights From Dysplastic Cerebellar Gangliocytoma

Recent embodied cognition research shows that access to action verbs in shallow-processing tasks becomes selectively compromised upon atrophy of the cerebellum, a critical motor region. Here we assessed whether cerebellar damage also disturbs explicit semantic processing of action pictures and its integration with ongoing motor responses. We evaluated a cognitively preserved 33-year-old man with severe dysplastic cerebellar gangliocytoma (Lhermitte-Duclos disease), encompassing most of the right cerebellum and the posterior part of the left cerebellum. The patient and eight healthy controls completed two semantic association tasks (involving pictures of objects and actions, respectively) that required motor responses. Accuracy results via Crawford’s modified t-tests revealed that the patient was selectively impaired in action association. Moreover, reaction-time analysis through Crawford’s Revised Standardized Difference Test showed that, while processing of action concepts involved slower manual responses in controls, no such effect was observed in the patient, suggesting that motor-semantic integration dynamics may be compromised following cerebellar damage. Notably, a Bayesian Test for a Deficit allowing for Covariates revealed that these patterns remained after covarying for executive performance, indicating that they were not secondary to extra-linguistic impairments. Taken together, our results extend incipient findings on the embodied functions of the cerebellum, offering unprecedented evidence of its crucial role in processing non-verbal action meanings and integrating them with concomitant movements. These findings illuminate the relatively unexplored semantic functions of this region while calling for extensions of motor cognition models.

Impact of Drosophila Models in the Study and Treatment of Friedreich's Ataxia

Drosophila melanogaster has been for over a century the model of choice of several neurobiologists to decipher the formation and development of the nervous system as well as to mirror the pathophysiological conditions of many human neurodegenerative diseases. The rare disease Friedreich’s ataxia (FRDA) is not an exception. Since the isolation of the responsible gene more than two decades ago, the analysis of the fly orthologue has proven to be an excellent avenue to understand the development and progression of the disease, to unravel pivotal mechanisms underpinning the pathology and to identify genes and molecules that might well be either disease biomarkers or promising targets for therapeutic interventions. In this review, we aim to summarize the collection of findings provided by the Drosophila models but also to go one step beyond and propose the implications of these discoveries for the study and cure of this disorder. We will present the physiological, cellular and molecular phenotypes described in the fly, highlighting those that have given insight into the pathology and we will show how the ability of Drosophila to perform genetic and pharmacological screens has provided valuable information that is not easily within reach of other cellular or mammalian models.

Cognitive and functional connectivity alterations in Friedreich's ataxia

Objective

The aim of this study was to perform the first resting-state functional MRI (RS-fMRI) analysis in Friedreich's ataxia (FRDA) patients to assess possible brain functional connectivity (FC) differences in these patients, and test their correlations with neuropsychological performances.

Methods

In total, 24 FRDA patients (M/F: 15/9, mean age 31.3 ± 15.0) and 24 healthy controls (HC; M/F: 15/9, mean age 30.7 ± 15.5) were enrolled in this cross-sectional study. All patients underwent a thorough neuropsychological battery, investigating different cognitive domains. RS-fMRI data were analyzed using a seed-based approach, probing the FC of cortical areas potentially referable to specific executive and cognitive functions compromised in FRDA.

Results

Compared to HC, FRDA patients showed overall worse neuropsychological scores in several domains, including global cognitive assessment, spatial memory, visuoperception and visuospatial functions, and executive functions. Analysis of RS-fMRI data showed a higher FC in FRDA patients compared to HC between paracingulate gyri and the medial frontal gryrus, between the superior frontal gyrus and bilateral angular gyri, and between the middle temporal gyrus and the cingulate gyrus, with a reduced FC between the medial frontal gryrus and the cerebellum.

Interpretation

We found a reduction in FC between frontal areas and the contralateral cerebellar cortex in FRDA, in line with the known alteration in cerebello-cortical pathway in this condition. On the other hand, a higher FC between different cortical areas was shown, possibly reflecting a compensatory phenomenon. These results, in conjunction with clinical findings, may shed new light on the pattern of supratentorial and infratentorial involvement, and on dynamics of brain plasticity in this disease.

Perceived fatigue and energy are independent unipolar states: Supporting evidence

Persistent fatigue is a common problem (∼20-45% of U.S. population), with higher prevalence and severity in people with medical conditions such as cancer, depression, fibromyalgia, heart failure, sleep apnea and multiple sclerosis. There are few FDA-approved treatments for fatigue and great disagreement on how to measure fatigue, with over 250 instruments used in research. Many instruments define fatigue as "a lack of energy", thus viewing energy and fatigue states as opposites on a single bipolar continuum. In this paper, we hypothesize that energy and fatigue are distinct perceptual states, should be measured using separate unipolar scales, have different mechanisms, and deficits should be treated using tailored therapies. Energy and fatigue independence has been found in both exploratory and confirmatory factor analysis studies. Experiments in various fields, including behavioral pharmacology and exercise science, often find changes in energy and not fatigue, or vice versa. If the hypothesis that energy and fatigue are independent is correct, there are likely different mechanisms that drive energy and fatigue changes. Energy could be increased by elevated dopamine and norepinephrine transmission and binding. Fatigue could be increased by elevated brain serotonin and inflammatory cytokines and reduced histamine binding. The hypothesis could be tested by an experiment that attempts to produce simultaneously high ratings of energy and fatigue (such as with two drugs using a randomized, double-blind, placebo-controlled design), which would offer strong evidence against the common viewpoint of a bipolar continuum. If the hypothesis is correct, prior literature using bipolar instruments will be limited, and research on the prevalence, mechanisms, and treatment of low energy and elevated fatigue as separate conditions will be needed. In the immediate future, measuring both energy and fatigue using unipolar measurement tools may improve our understanding of these states and improve therapeutic outcomes.

Depressive symptoms in Friedreich ataxia

Background/Objective: Almost no attention has been paid to depression in Friedreich ataxia (FRDA), a highly disabling cerebellar degenerative disease. Our aim was to study the presence and the profile of depressive symptoms in FRDA and their relationship with demographic-disease variables and cognitive processing speed. Method: The study groups consisted of 57 patients with a diagnosis of FRDA. The Beck Depression Inventory-II was used to assess symptoms of depression. Speed of information processing was measured with a Choice Reaction time task. Results: The mean BDI score for patients was significantly higher than the mean score in the general population. Twenty one percent of participants scored in the moderate/severe range. A Cognitive-Affective score and a Somatic-Motivational score was calculated for each patient. Patients’ scores in both dimensions were significantly higher than the scores in the general population. Demographic and disease variables were not related with symptoms of depression, except for severity of ataxia. Depressive symptoms predict cognitive reaction times. The greater proportion of variance was explained by the Cognitive-Affective dimension. Conclusions: Our data show that both somatic-motivational and cognitive affective symptoms of depression are frequent in individuals with FRDA. In addition, depressive symptoms may influence cognition, especially, the cognitive and affective symptoms.

Measuring Inhibition and Cognitive Flexibility in Friedreich Ataxia

Friedreich ataxia (FRDA) is an autosomal recessive neurodegenerative disorder with subtle impact on cognition. Inhibitory processes and cognitive flexibility were examined in FRDA by assessing the ability to suppress a predictable verbal response. We administered the Hayling Sentence Completion Test (HSCT), the Trail Making Test, and the Stroop Test to 43 individuals with FRDA and 42 gender- and age-matched control participants. There were no significant group differences in performance on the Stroop or Trail Making Test whereas significant impairment in cognitive flexibility including the ability to predict and inhibit a pre-potent response as measured in the HSCT was evident in individuals with FRDA. These deficits did not correlate with clinical characteristics of FRDA (age of disease onset, disease duration, number of guanine-adenine-adenine repeats on the shorter or larger FXN allele, or Friedreich Ataxia Rating Scale score), suggesting that such impairment may not be related to the disease process in a straightforward way. The observed specific impairment of inhibition and predictive capacity in individuals with FRDA on the HSCT task, in the absence of impairment in associated executive functions, supports cerebellar dysfunction in conjunction with disturbance to cortico-thalamo-cerebellar connectivity, perhaps via inability to access frontal areas necessary for successful task completion.

Cerebral compensation during motor function in Friedreich ataxia: The IMAGE-FRDA study

BACKGROUND

Friedreich ataxia is characterized by progressive motor incoordination that is linked to peripheral, spinal, and cerebellar neuropathology. Cerebral abnormalities are also reported in Friedreich ataxia, but their role in disease expression remains unclear.

METHODS

In this cross-sectional functional magnetic resonance imaging study, 25 individuals with Friedreich ataxia and 33 healthy controls performed simple (self-paced single-finger) and complex (visually cued multifinger) tapping tasks to respectively gauge basic and attentionally demanding motor behavior. For each task, whole brain functional activations were compared between groups and correlated with disease severity and offline measures of motor dexterity.

RESULTS

During simple finger tapping, cerebral hyperactivation in individuals with Friedreich ataxia at the lower end of clinical severity and cerebral hypoactivation in those more severely affected was observed in premotor/ventral attention brain regions, including the supplementary motor area and anterior insula. Greater activation in this network correlated with greater offline finger tapping precision. Complex, attentionally demanding finger tapping was also associated with cerebral hyperactivation, but in this case within dorsolateral prefrontal regions of the executive control network and superior parietal regions of the dorsal attention system. Greater offline motor precision was associated with less activation in the dorsal attention network.

DISCUSSION

Compensatory activity is evident in the cerebral cortex in individuals with Friedreich ataxia. Early compensation followed by later decline in premotor/ventral attention systems demonstrates capacity-limited neural reserve, while the additional engagement of higher order brain networks is indicative of compensatory task strategies. Network-level changes in cerebral brain function thus potentially serve to mitigate the impact of motor impairments in Friedreich ataxia. © 2017 International Parkinson and Movement Disorder Society.