3T sodium MR imaging in Alzheimer's disease shows stage-dependent sodium increase influenced by age and local brain volume.

INTRODUCTION: Application of MRI in clinical routine mainly addresses structural alterations. However, pathological changes at a cellular level are expected to precede the occurrence of brain atrophy clusters and of clinical symptoms. In this context, 23Na-MRI examines sodium changes in the brain as a potential metabolic parameter. Recently, we have shown that 23Na-MRI at ultra-high-field (7 T) was able to detect increased tissue sodium concentration (TSC) in Alzheimer's disease (AD). In this work, we aimed at assessing AD-pathology with 23Na-MRI in a larger cohort and on a clinical 3T MR scanner. METHODS: We used a multimodal MRI protocol on 52 prodromal to mild AD patients and 34 cognitively healthy control subjects on a clinical 3T MR scanner. We examined the TSC, brain volume, and cortical thickness in association with clinical parameters. We further compared TSC with intra-individual normalized TSC for the reduction of inter-individual TSC variability resulting from physiological as well as experimental conditions. Normalized TSC maps were created by normalizing each voxel to the mean TSC inside the brain stem. RESULTS: We found increased normalized TSC in the AD cohort compared to elderly control subjects both on global as well as on a region-of-interest-based level. We further confirmed a significant association of local brain volume as well as age with TSC. TSC increase in the left temporal lobe was further associated with the cognitive state, evaluated via the Montreal cognitive assessment (MoCA) screening test. An increase of normalized TSC depending on disease stage reflected by the Clinical Dementia Rating (CDR) was found in our AD patients in temporal lobe regions. In comparison to classical brain volume and cortical thickness assessments, normalized TSC had a higher discriminative power between controls and prodromal AD patients in several regions of the temporal lobe. DISCUSSION: We confirm the feasibility of 23Na-MRI at 3T and report an increase of TSC in AD in several regions of the brain, particularly in brain regions of the temporal lobe. Furthermore, to reduce inter-subject variability caused by physiological factors such as circadian rhythms and experimental conditions, we introduced normalized TSC maps. This showed a higher discriminative potential between different clinical groups in comparison to the classical TSC analysis. In conclusion, 23Na-MRI represents a potential translational imaging marker applicable e.g.for diagnostics and the assessment of intervention outcomes in AD even under clinically available field strengths such as 3T. Implication of 23Na-MRI in association with other metabolic imaging marker needs to be further elucidated.

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.

Increased neural motor activation and functional reorganization in patients with idiopathic rapid eye movement sleep behavior disorder.

INTRODUCTION: Altered brain activity and functional reorganization patterns during self-initiated movements have been reported in early pre-motor and motor stages of Parkinson's disease. The aim of this study was to investigate whether similar alterations can be observed in patients with idiopathic REM-sleep behavior disorder (RBD). METHODS: 13 polysomnography-confirmed male and right-handed RBD patients and 13 healthy controls underwent a bilateral hand-movement fMRI task including internally selected (INT) and externally-guided (EXT) movement conditions for each hand. We examined functional activity and connectivity differences between groups and task-conditions, structural differences using voxel-based morphometry, as well as associations between functional activity and clinical variables. RESULTS: No group differences were observed in fMRI-task performance or in voxel-based morphometry. Both groups showed faster reaction times and exhibited greater neural activation when movements were internally selected compared to externally-guided tasks. Compared to controls, RBD patients displayed stronger activation in the dorsolateral prefrontal cortex and primary somatosensory cortex during INT-tasks, and in the right fronto-insular cortex during EXT-tasks performed with the non-dominant hand. Stronger activation in RBD patients was associated with cognitive and olfactory impairment. Connectivity analysis demonstrated overall less interregional coupling in patients compared to controls. In particular, patients showed reduced temporo-cerebellar, occipito-cerebellar and intra-cerebellar connectivity, but stronger connectivity in fronto-cerebellar and fronto-occipital pathways. CONCLUSION: The observed stronger activation during hand-movement tasks and connectivity changes in RBD may reflect early compensatory and reorganization patterns in order to preserve motor functioning. Our findings may contribute to a better understanding and prognosis of prodromal stages of α-synucleinopathies.

Clinical predictors and neural correlates for compromised swallowing safety in Huntington disease.

BACKGROUND AND PURPOSE: Dysphagia is one of the most common and important complications in Huntington disease (HD), frequently leading to aspiration pneumonia and mortality. Objective estimates of prevalence using instrumental diagnostics and data on neural correlates of dysphagia in HD are scarce or lacking entirely. Similarly, its correlation with other clinical markers is still not fully known. We aimed at defining clinical risk factors and neural correlates for compromised swallowing safety in HD more precisely. METHODS: Thirty-four HD subjects (16 female, Shoulson & Fahn Stage I-IV, two premanifest) underwent a full clinical-neurological examination including the cranial nerves, the Unified Huntington's Disease Rating Scale total motor score, and the Mini-Mental State Examination. Fiberoptic endoscopic evaluation of swallowing (FEES) was performed by a trained speech and language therapist. Twenty-six subjects additionally underwent a high-resolution anatomical magnetic resonance imaging (MRI) scan (T1, 3-T Siemens Prisma). Moreover, we correlated clinical and atrophy (MRI) measures with swallowing safety levels as judged by the validated Penetration-Aspiration Scale. RESULTS: FEES showed penetration or aspiration in 70.6%. Using partial correlation, no significant correlations were found between swallowing safety and any of the clinical markers after correcting for disease duration and CAG repeat length. Voxel-based morphometry demonstrated atrophy associated with compromised swallowing safety in a network of parietothalamocerebellar areas related to sensorimotor communication, notably excluding striatum. CONCLUSIONS: Our results characterise dysphagia in HD as a disorder of communication between sensory and motor networks involved in swallowing. This finding and high rates of silent aspiration argue in favor of instrumental swallowing evaluation early in the disease.

Impact of gender and genetics on emotion processing in Parkinson's disease - A multimodal study.

•Understanding of the phenotypic heterogeneity of Parkinson's disease is needed.•Gender and genetics determine manifestation and progression of Parkinson's disease.•Altered emotion processing in Parkinson's disease is specific to male patients.•This is influenced by endocrinal and genetic factors in both genders.•This finding may impact the diagnosis and treatment of emerging clinical features.

Brain atrophy measures in preclinical and manifest spinocerebellar ataxia type 2.

Objective: Spinocerebellar ataxia type 2 (SCA2) is an autosomal dominantly inherited neurodegenerative disease mainly affecting the cerebellum and brainstem. In this Cuban-German research collaboration, we aimed to characterize atrophy patterns and associations with clinical measures in preclinical and manifest SCA2. Methods: In this study, 16 nonmanifest SCA2 mutation carriers, 26 manifest patients with SCA2, and 18 healthy control subjects underwent magnetic resonance imaging, as well as genetic and clinical characterization including assessment of ataxia (Scale for the Assessment and Rating of Ataxia) and saccade velocity in Cuba were enrolled. Semiautomated quantitative volumetry of the cerebellum and brainstem, subdivided into the medulla oblongata, the pontine brainstem, and mesencephalon was performed. Additionally, the anteroposterior diameter of the pontine brainstem was measured. Results: Analysis of volumetric data revealed degeneration of the cerebellum and brainstem, in particular of pontine volumes and the anteroposterior diameter of the pons, in both manifest SCA2 patients and individuals at risk for SCA2 compared to controls. Comparing patients with nonataxic preclinical SCA2 mutation carriers, we found more pronounced reductions of the pontine brainstem and cerebellum in manifest SCA2. Volumetric data further showed associations with CAG repeat length and predicted age of onset in preclinical SCA2 individuals, and by trend with ataxia signs in patients. Although saccade velocity was associated with reduction in the pontine brainstem in preclinical and manifest SCA2, reduced ability to suppress interfering stimuli measured by the Stroop task was related to cerebellar volume loss in patients. Interpretation: Preclinical SCA2 mutation carriers exhibit brain abnormalities, which could be targeted as surrogate parameters for disease progression and in future preventive trials.

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

OBJECTIVE: Friedreich's ataxia (FRDA) is a spinocerebellar degenerative disorder, in which cognitive deficits are sparsely explored. In this behavioral and multimodal magnetic resonance imaging (MRI) study, we investigated the neurocognitive profile and cortico-cerebellar dysfunctions underlying executive functioning in individuals with FRDA. METHODS: 22 FRDA patients and 22 controls were clinically and neuropsychologically examined. Fifteen of each underwent structural and functional MRI using a verbal-fluency task with phonemic and semantic conditions. Gray (GM) and white matter (WM) alterations were assessed by means of voxel-based morphometry and diffusion-tensor imaging. RESULTS: The neuropsychological profile demonstrated deficits in verbal fluency, working memory and social cognition. Functional MRI data showed most pronounced group-differences in phonemic fluency with patients exhibiting enhanced activity in the cerebellum (VI, Crus I), fronto-insular, premotor and temporo-occipital regions. The semantic condition only revealed reduced activity in the anterior cerebellum; for overt speech, we found increased activity in the motor cortex. Functional connectivity-analysis showed higher co-activation within cerebellar and cortical regions, respectively, and impaired interregional coupling between the cerebellum and fronto-insular cortex for phonemic processing, which was also related to poorer task performance. GM reduction in FRDA was mainly found in lobule VI, whereas WM degeneration was more pronounced including brainstem, cerebellum, and cortex. Decreased cerebellar GM was associated with enhanced activity in the fronto-insular cortex, while loss of WM integrity may translate cortico-cerebellar pathway disruptions. INTERPRETATION: The pattern of increased neural response with both cerebellar and cortical involvement underlying executive functioning indicates functional reorganization driven by disease-related structural damage in FRDA.

Increased cerebral water content in hemodialysis patients.

Little information is available on the impact of hemodialysis on cerebral water homeostasis and its distribution in chronic kidney disease. We used a neuropsychological test battery, structural magnetic resonance imaging (MRI) and a novel technique for quantitative measurement of localized water content using 3T MRI to investigate ten hemodialysis patients (HD) on a dialysis-free day and after hemodialysis (2.4±2.2 hours), and a matched healthy control group with the same time interval. Neuropsychological testing revealed mainly attentional and executive cognitive dysfunction in HD. Voxel-based-morphometry showed only marginal alterations in the right inferior medial temporal lobe white matter in HD compared to controls. Marked increases in global brain water content were found in the white matter, specifically in parietal areas, in HD patients compared to controls. Although the global water content in the gray matter did not differ between the two groups, regional increases of brain water content in particular in parieto-temporal gray matter areas were observed in HD patients. No relevant brain hydration changes were revealed before and after hemodialysis. Whereas longer duration of dialysis vintage was associated with increased water content in parieto-temporal-occipital regions, lower intradialytic weight changes were negatively correlated with brain water content in these areas in HD patients. Worse cognitive performance on an attention task correlated with increased hydration in frontal white matter. In conclusion, long-term HD is associated with altered brain tissue water homeostasis mainly in parietal white matter regions, whereas the attentional domain in the cognitive dysfunction profile in HD could be linked to increased frontal white matter water content.

Neural correlates of impaired emotion processing in manifest Huntington's disease.

The complex phenotype of Huntington's disease (HD) encompasses motor, psychiatric and cognitive dysfunctions, including early impairments in emotion recognition. In this first functional magnetic resonance imaging study, we investigated emotion-processing deficits in 14 manifest HD patients and matched controls. An emotion recognition task comprised short video clips displaying one of six basic facial expressions (sadness, happiness, disgust, fear, anger and neutral). Structural changes between patients and controls were assessed by means of voxel-based morphometry. Along with deficient recognition of negative emotions, patients exhibited predominantly lower neural response to stimuli of negative valences in the amygdala, hippocampus, striatum, insula, cingulate and prefrontal cortices, as well as in sensorimotor, temporal and visual areas. Most of the observed reduced activity patterns could not be explained merely by regional volume loss. Reduced activity in the thalamus during fear correlated with lower thalamic volumes. During the processing of sadness, patients exhibited enhanced amygdala and hippocampal activity along with reduced recruitment of the medial prefrontal cortex. Higher amygdala activity was related to more pronounced amygdala atrophy and disease burden. Overall, the observed emotion-related dysfunctions in the context of structural neurodegeneration suggest both disruptions of striatal-thalamo-cortical loops and potential compensation mechanism with greater disease severity in manifest HD.

Altered resting-state connectivity in Huntington's disease.

Huntington's disease (HD) is an autosomal dominantly inherited neurodegenerative disorder characterized by motor, cognitive, and psychiatric symptoms. Using resting-state fMRI (rs-fMRI) we investigated the functional integrity of resting-state networks (RSN) in HD. 17 HD and 19 matched control participants were examined at a 3 Tesla MR scanner. After controlling for structural degeneration by means of voxel-based morphometry, task-free rs-fMRI data were analyzed using Independent Component Analysis (ICA) and a dual-regression approach in the context of genetic and clinical parameters. Further, we evaluated HD-related differences in interregional connectivity between networks. RSN analysis showed a significant increase in intrinsic functional connectivity in the HD sample compared with controls, including the thalamus, striatum, prefrontal, premotor, and parietal maps. A subset of the Default Mode Network (DMN) was also affected. In the HD cohort, motor impairment correlated with higher network connectivity in mainly motor and parietal cortices. Deteriorating total functional capacity was additionally associated with higher connectivity in the striatum, thalamus, insular and frontal areas. This pattern of increased activity in intrinsic functional networks might suggest a reduced ability of intra-network differentiation with clinical disease progression in HD. Finally, results showed reduced long-range connectivity between parietal ICA components in HD compared to controls, indicating impaired functional coupling between interregional networks in HD. Our data demonstrates that functional connectivity is profoundly altered in HD, both within and between RSN. Rs-fMRI analysis may provide additional valuable insights into neuronal dysfunctions beyond HD-related structural degeneration and disruptions of functional circuits in HD.

Diminished activation of motor working-memory networks in Parkinson's disease.

Parkinson's disease (PD) is characterized by typical extrapyramidal motor features and increasingly recognized non-motor symptoms such as working memory (WM) deficits. Using functional magnetic resonance imaging (fMRI), we investigated differences in neuronal activation during a motor WM task in 23 non-demented PD patients and 23 age- and gender-matched healthy controls. Participants had to memorize and retype variably long visuo-spatial stimulus sequences after short or long delays (immediate or delayed serial recall). PD patients showed deficient WM performance compared to controls, which was accompanied by reduced encoding-related activation in WM-related regions. Mirroring slower motor initiation and execution, reduced activation in motor structures such as the basal ganglia and superior parietal cortex was detected for both immediate and delayed recall. Increased activation in limbic, parietal and cerebellar regions was found during delayed recall only. Increased load-related activation for delayed recall was found in the posterior midline and the cerebellum. Overall, our results demonstrate that impairment of WM in PD is primarily associated with a widespread reduction of task-relevant activation, whereas additional parietal, limbic and cerebellar regions become more activated relative to matched controls. While the reduced WM-related activity mirrors the deficient WM performance, the additional recruitment may point to either dysfunctional compensatory strategies or detrimental crosstalk from "default-mode" regions, contributing to the observed impairment.

Genotype-specific patterns of atrophy progression are more sensitive than clinical decline in SCA1, SCA3 and SCA6.

Spinocerebellar ataxias are dominantly inherited disorders that are associated with progressive brain degeneration, mainly affecting the cerebellum and brainstem. As part of the multicentre European integrated project on spinocerebellar ataxias study, 37 patients with spinocerebellar ataxia-1, 19 with spinocerebellar ataxia-3 and seven with spinocerebellar ataxia-6 were clinically examined and underwent magnetic resonance imaging at baseline and after a 2-year follow-up. All patients were compared with age-matched and gender-matched healthy control subjects. Magnetic resonance imaging analysis included three-dimensional volumetry and observer-independent longitudinal voxel-based morphometry. Volumetry revealed loss of brainstem, cerebellar and basal ganglia volume in all genotypes. Most sensitive to change was the pontine volume in spinocerebellar ataxia-1, striatal volume in spinocerebellar ataxia-3 and caudate volume in spinocerebellar ataxia-6. Sensitivity to change, as measured by standard response mean, of the respective MRI measures was greater than that of the most sensitive clinical measure, the Scale for the Assessment and Rating of Ataxia. Longitudinal voxel-based morphometry revealed greatest grey matter loss in the cerebellum and brainstem in spinocerebellar ataxia-1, in the putamen and pallidum in spinocerebellar ataxia-3 and in the cerebellum, thalamus, putamen and pallidum in spinocerebellar ataxia-6. There was a mild correlation between CAG repeat length and volume loss of the bilateral cerebellum and the pons in spinocerebellar ataxia-1. Quantitative volumetry and voxel-based morphometry imaging demonstrated genotype-specific patterns of atrophy progression in spinocerebellar ataxias-1, 3 and 6, and they showed a high sensitivity to detect change that was superior to clinical scales. These structural magnetic resonance imaging findings have the potential to serve as surrogate markers, which might help to delineate quantifiable endpoints and non-invasive methods for rapid and reliable data acquisition, encouraging their use in clinical trials.

Differential activation of memory-relevant brain regions during a dialysis cycle.

Cognitive impairment is a common and largely undiagnosed finding in a significant number of dialysis patients. These alterations may result from concomitant cerebrovascular disease, hemodynamic instability, the uremic milieu, or changes induced by the dialysis process. In order to gain further insight into this, we recruited 12 stable chronic hemodialysis patients (without clinical neurological disease) and an age- and gender-matched cohort of 12 control individuals (without renal or neurological problems) in a prospective, single-center study. In order to disentangle the influence of dialysis itself on memory function, each dialysis patient was tested twice: once immediately before dialysis following a long weekend (t1) and again the day after this dialysis (t2). The control individuals were tested in the same time frame. Neuropsychological testing found that the control individuals performed significantly better in verbal learning, motor speed, task switching, verbal comprehension, word fluency, spatial visualization, spatial perception, and reasoning; all independent of the time point. Functional magnetic resonance imaging of the whole brain in seven hemodialysis patients found significantly more bilateral activation of the hippocampus during the verbal working memory task at t2 relative to t1 compared with their seven matched control counterparts. Thus, our study found differential and task-specific activation of memory-relevant brain areas during a dialysis cycle.

Ageing-related changes of neural activity associated with spatial contextual memory.

Neuropsychological studies provide evidence for an ageing-related decline of memory for contextual information related to remembered items. Using event-related fMRI we investigated the neural correlates of ageing-related changes during encoding and retrieval of spatial contextual memory. Eighteen young and 17 older subjects were included in the analysis (mean age 24 and 60 years, respectively). Although young and older subjects recognised the same amount of items during retrieval, spatial context memory for remembered items was superior in younger subjects. In both groups, left parahippocampal activity during encoding predicted contextual memory performance during retrieval. During encoding, an interaction between age and success of spatial context encoding was found in the left fusiform gyrus. During retrieval, the left hippocampal formation showed higher activity for successful than for unsuccessful spatial context retrieval as well as an interaction between age and spatial context judgement. Both findings are likely to underlie the contextual memory deficit observed in older subjects.