Quantification of gray matter changes in the cerebral cortex after isolated cerebellar damage: a voxel-based morphometry study

Modulating mental state recognition by anodal tDCS over the cerebellum

Increasing evidence from neuroimaging and clinical studies has demonstrated cerebellar involvement in social cognition components, including the mentalizing process. The aim of this study was to apply transcranial direct current stimulation (tDCS) to modulate cerebellar excitability to investigate the role the cerebellum plays in mental state recognition. Forty-eight healthy subjects were randomly assigned to different groups in which anodal, cathodal, or sham tDCS (2 mA for 20 min) was delivered centering the electrode on the vermis to stimulate the posterior portion of the cerebellum. The ability to attribute mental states to others was tested before and after tDCS using a digital version of the 'Reading the Mind in the Eyes test', which includes visual perceptive and motor stimuli as control conditions. Correct response and reaction times (RTs) were recorded. The results revealed a significant reduction in RTs between the baseline and post-stimulation sessions after cerebellar anodal tDCS only for mental state stimuli (Wilcoxon test p = 0.00055), whereas no significant effect was found in the cathodal or sham conditions or for visual perceptive and motor stimuli. Overall, our study suggests that cerebellar anodal tDCS might selectively improve mental state recognition and constitute an effective strategy to positively modulate the mentalizing process.

Mapping the Cerebellar Cognitive Affective Syndrome in Patients with Chronic Cerebellar Strokes

The cerebellar cognitive affective syndrome (CCAS) has been consistently described in patients with acute/subacute cerebellar injuries. However, studies with chronic patients have had controversial findings that have not been explored with new cerebellar-target tests, such as the CCAS scale (CCAS-S). The objective of this research is to prove and contrast the usefulness of the CCAS-S and the Montreal Cognitive Assessment (MoCA) test to evaluate cognitive/affective impairments in patients with chronic acquired cerebellar lesions, and to map the cerebellar areas whose lesions correlated with dysfunctions in these tests. CCAS-S and MoCA were administrated to 22 patients with isolated chronic cerebellar strokes and a matched comparison group. The neural bases underpinning both tests were explored with multivariate lesion-symptom mapping (LSM) methods. MoCA and CCAS-S had an adequate test performance with efficient discrimination between patients and healthy volunteers. However, only impairments determined by the CCAS-S resulted in significant regional localization within the cerebellum. Specifically, patients with chronic cerebellar lesions in right-lateralized posterolateral regions manifested cognitive impairments inherent to CCAS. These findings concurred with the anterior-sensorimotor/posterior-cognitive dichotomy in the human cerebellum and revealed clinically intra- and cross-lobular significant regions (portions of right lobule VI, VII, Crus I-II) for verbal tasks that overlap with the "language" functional boundaries in the cerebellum. Our findings prove the usefulness of MoCA and CCAS-S to reveal cognitive impairments in patients with chronic acquired cerebellar lesions. This study extends the understanding of long-term CCAS and introduces multivariate LSM methods to identify clinically intra- and cross-lobular significant regions underpinning chronic CCAS.

Impairments in Emotion Recognition and Risk-Taking Behavior After Isolated, Cerebellar Stroke

An increasing amount of research has shown a cerebellar involvement in higher order cognitive functions, including emotional processing and decision-making. However, it has not been investigated whether impairments in facial emotion recognition, which could be a marker of impaired emotional experiences, are related to risky decision-making in these patients. Therefore, we aimed to investigate facial emotion recognition and risky decision-making in these patients as well as to investigate a relationship between these constructs. Thirteen patients with a discrete, isolated, cerebellar lesion as a consequence of a stroke were included in the study. Emotion recognition was assessed with the Facial Expressions of Emotions—Stimuli and Test (FEEST). Risk-taking behavior was assessed with the Action Selection Test (AST). Furthermore, 106 matched healthy controls performed the FEEST and 20 matched healthy controls performed the AST. Compared with healthy controls, patients were significantly worse in the recognition of emotional expressions and they took significantly more risks. In addition, a worse ability to recognize fearful facial expressions was strongly related to an increase in risky decisions in the AST. Therefore, we suggest that tests of emotion recognition should be incorporated into the neuropsychological assessment after cerebellar stroke to boost detection and treatment of these impairments in these patients.

Prospective investigation of cerebellar cognitive affective syndrome in a previously non-demented population of acute cerebellar stroke

OBJECTIVE

In this prospective study, we aimed to investigate the presence and evolution of cerebellar cognitive affective syndrome in a cohort of isolated cerebellar stroke with no known cognitive or psychiatric impairment. We tried to distinguish the unconfounded effect of cerebellar lesions on neuropsychological processing.

METHODS

After a meticulous exclusion procedure based on possible confounders, we recruited 14 patients and 13 age-matched healthy controls to the study, prospectively. All of the patients had a detailed initial neuropsychological assessment at the first week and a follow-up assessment at the 4th month after stroke.

RESULTS

The prevalence of cognitive or behavioral-affective abnormalities in our cohort were 86% and 64% respectively. The patients exhibited mild and transient affective-behavioral abnormalities except for depressive symptoms that persisted in the subacute stage. They scored lower in general cognitive performance as revealed by mini mental test (p=0.001). Memory, executive functions, attention and working memory, central processing speed, and linguistic abilities were impaired (p<0.001; p=0.001; p=0.007; p=0.05; p<0.001 respectively). Improvement was evident only in memory domain of the cognitive functions in the subacute stage. Cognitive impairment was more likely with a medial or posterolateral infarct (p=0.014). Behavioral-affective abnormalities were not associated with a specific location in our cohort. Age seemed to negatively correlate with the recovery in general cognitive performance on the follow-up.

CONCLUSIONS

These findings show that acute denervation of cerebellocortical projections leads to mild affective-behavioral abnormalities, and full-blown cerebellar cognitive affective syndrome is rare. However, cognition was significantly affected after an acute cerebellar infarct even in a previously healthy, non-demented pure population.

Preterm infants with isolated cerebellar hemorrhage show bilateral cortical alterations at term equivalent age

The cerebellum is connected to numerous regions of the contralateral side of the cerebrum. Motor and cognitive deficits following neonatal cerebellar hemorrhages (CbH) in extremely preterm neonates may be related to remote cortical alterations, following disrupted cerebello-cerebral connectivity as was previously shown within six CbH infants. In this retrospective case series study, we used MRI and advanced surface-based analyses to reconstruct gray matter (GM) changes in cortical thickness and cortical surface area in extremely preterm neonates (median age = 26; range: 24.9-26.7 gestational weeks) with large isolated unilateral CbH (N = 5 patients). Each CbH infant was matched with their own preterm infant cohort (range: 20-36 infants) based on sex and gestational age at birth. On a macro level, our data revealed that the contralateral cerebral hemisphere of CbH neonates did not show less cortical thickness or cortical surface area than their ipsilateral cerebral hemisphere at term. None of the cases differed from their matched cohort groups in average cortical thickness or average cortical surface area in the ipsilateral or contralateral cerebral hemisphere. On a micro (i.e. vertex) level, we established high variability in significant local cortical GM alteration patterns across case-cohort groups, in which the cases showed thicker or bigger volume in some regions, among which the caudal middle frontal gyrus, insula and parahippocampal gyrus, and thinner or less volume in other regions, among which the cuneus, precuneus and supratentorial gyrus. This study highlights that cerebellar injury during postnatal stages may have  widespread bilateral influence on the early maturation of cerebral cortical regions, which implicate complex cerebello-cerebral interactions to be present at term birth.

The therapeutic effect of treatment with RehaCom software on verbal performance in patients with multiple sclerosis

Multiple sclerosis (MS) is characterized by central nervous system lesions that lead to neurological dysfunctions including fatigue, depression and anxiety. MS is affecting almost 2.3 million people around the world, with the significant highest prevalence in the North America. MS also affects different cognitive abilities, such as attention, memory and executive functions. Furthermore, a significant impairment in verbal fluency and naming abilities in patients with MS has been reported. RehaCom, is a software that has improvement effects on cognitive functions. The goal of this research is to investigate the effect of treatment with RehaCom on verbal performance in patients with MS. To select the participants, 60 patients with MS who referred to our clinic were chosen randomly and divided into Control (n = 30) and Experimental (n = 30) groups. The participants in the experimental group were treated by RehaCom software for 10 sessions during 5 weeks (2 sessions per week and each session was 1 h). Controlled Oral Word Association Test (COWAT) and California Verbal Learning Test - Second Edition (CVLT-II), were used to assess verbal performance (verbal fluency, and verbal learning and memory) at weeks 0 (baseline), 5 (post-test) and 10 (follow-up). The results showed that, treatment with RehaCom improved verbal performance in patient with MS, at both post-test and follow-up stages. In conclusion, treatment with RehaCom cognitive rehabilitation software can improve verbal fluency, and verbal learning and memory in patient with MS, possibly by affecting the brain regions involved in language performance.

Cerebellar dentate nucleus functional connectivity with cerebral cortex in Alzheimer's disease and memory: a seed-based approach

Alzheimer's disease (AD) is a chronic neurodegenerative disorder characterized by specific patterns of gray and white matter damage and cognitive/behavioral manifestations. The cerebellum has also been implicated in the pathophysiology of AD. Because the cerebellum is known to have strong functional connectivity (FC) with associative cerebral cortex regions, it is possible to hypothesize that it is incorporated into intrinsic FC networks relevant to cognitive manifestation of AD. In the present study, the cerebellar dentate nucleus, the largest cerebellar nucleus and the major output channel to the cerebral cortex, was chosen as the region of interest to test potential cerebellocerebral FC alterations and correlations with patients' memory impairment in a group of patients with AD. Compared to controls, patients with AD showed an increase in FC between the dentate nucleus and regions of the lateral temporal lobe. This study demonstrates that lower memory performances in AD may be related to altered FC within specific cerebellocortical functional modules, thus suggesting the cerebellar contribution to AD pathophysiology and typical memory dysfunctions.

Stroke and potential benefits of brain-computer interface

To treat stroke and, in particular, to alleviate the personal and social burden of stroke survivors is a main challenge for neuroscience research. Advancements in the knowledge of neurobiologic mechanisms subserving stroke-related damage and recovery provide key data to guide clinicians to tailor interventions to specific patient's needs. How does the brain-computer interface (BCI) fit into this scenario? A technique created to allow completely paralyzed individuals to control the environment recently introduced a new line of development: to provide a means to possibly control formation and changes in the brain network organization. In a sort of revolution, similar to the change from geocentric to heliocentric planet organization envisioned by Copernicus, we are facing a critical change in BCI research, moving from a brain to computer direction to a computer to brain one. This direction change will profoundly open up new avenues for BCI research and clinical applications. In this chapter, we address this change and discuss present and future applications of this new line idea of BCI use in stroke.

Motor and cognitive impairments in spinocerebellar ataxia type 7 and its correlations with cortical volumes

Spinocerebellar Ataxia Type 7 (SCA7) is a neurodegenerative disorder caused by cytosine-adenine-guanine (CAG) repeat expansion. It is clinically characterized by ataxia and visual loss. To date, little is known about SCA7 cognitive impairments and its relationship with grey matter volume (GMV) changes. The aim of this study was to explore SCA7 patients' performance in specific components of auditory-verbal neuropsychological tests and to correlate their scores with genetic mutation, severity of ataxia and GMV. We assessed verbal memory and verbal fluency proficiencies in 31 genetically confirmed SCA7 patients, and compared their results with 32 healthy matched volunteers; we also correlated CAG repeats and severity of motor symptoms with performance in the auditory-verbal tests. SCA7 patients exhibited deficiencies in several components of these cognitive tasks, which were independent of motor impairments and showed no relation to CAG repeats. Based on Resonance Images performed in 27 patients we found association between ataxia severity and GMV in "sensoriomotor" cerebellum, as well as correlations of impaired verbal memory and semantic fluency scores with GMV in association cortices, including the right parahippocampal gyrus. To our knowledge, this is the first report of deficits in the organization of semantic information and in the evocation of verbal material, as well as greater susceptibility to proactive interference in SCA7 patients. These findings bring novel information about specific cognitive abilities in SCA7 patients, particularly verbal memory and fluency, and their relation with GMV variations in circumscribed brain regions, including association cortices known to have functional relationships with the cerebellum.

Structural cerebellar correlates of cognitive functions in spinocerebellar ataxia type 2

Spinocerebellar ataxia type 2 (SCA2) is an autosomal dominant neurodegenerative disease involving the cerebellum and characterized by a typical motor syndrome. In addition, the presence of cognitive impairment is now widely acknowledged as a feature of SCA2. Given the extensive connections between the cerebellum and associative cerebral areas, it is reasonable to hypothesize that cerebellar neurodegeneration associated with SCA2 may impact on the cerebellar modulation of the cerebral cortex, thus resulting in functional impairment. The aim of the present study was to investigate and quantitatively map the pattern of cerebellar gray matter (GM) atrophy due to SCA2 neurodegeneration and to correlate that with patients' cognitive performances. Cerebellar GM maps were extracted and compared between SCA2 patients (n = 9) and controls (n = 33) by using voxel-based morphometry. Furthermore, the relationship between cerebellar GM atrophy and neuropsychological scores of the patients was assessed. Specific cerebellar GM regions were found to be affected in patients. Additionally, GM loss in cognitive posterior lobules (VI, Crus I, Crus II, VIIB, IX) correlated with visuospatial, verbal memory and executive tasks, while additional correlations with motor anterior (V) and posterior (VIIIA, VIIIB) lobules were found for the tasks engaging motor and planning components. Our results provide evidence that the SCA2 neurodegenerative process affects the cerebellar cortex and that MRI indices of atrophy in different cerebellar subregions may account for the specificity of cognitive symptomatology observed in patients, as result of a cerebello-cerebral dysregulation.

Brain volumetric analysis and cortical thickness in adults with saccadic intrusions (ocular flutter or opsoclonus-myoclonus syndrome)

OBJECTIVES

Ocular flutter (OF) and opsoclonus are considered a continuum with a similar pathogenesis. Due to the rarity of this disease in the adult population, little is known about the brain morphological changes in the chronic phase of the disease.

PATIENTS AND METHODS

Six magnetic resonance imaging from adults with previous history of OF/Opsoclonus and 12 healthy patients (paired by age and sex) were analyzed in order to identify the long term cortical thickness pattern in this rare disease by using Freesurfer.

RESULTS

Patients with OF/Opsoclonus showed reduced cerebellum cortical volume with a subsequent diminution in total cerebellar volume. White mater cerebellum volume was not modified. In addition, we have also identified a significant supratentorial gray matter volume decrease in OF/Opsoclonus patients, involving both the cortical and the subcortical gray matter.

CONCLUSIONS

OF/Opsoclonus in adults may be associated with cortical and subcortical gray matter atrophy, as well as decreased cerebellar cortical volume. Further larger prospective studies are necessary to confirm these results.

Microstructural analyses of the posterior cerebellar lobules in relapsing-onset multiple sclerosis and their implication in cognitive impairment

BACKGROUND

The posterior cerebellar lobules seem to be the anatomical substrate of cognitive cerebellar processes, but their microstructural alterations in multiple sclerosis (MS) remain unclear.

OBJECTIVES

To correlate diffusion metrics in lobules VI to VIIIb in persons with clinically isolated syndrome (PwCIS) and in cognitively impaired persons with MS (CIPwMS) with their cognitive performances.

METHODS

Sixty-nine patients (37 PwCIS, 32 CIPwMS) and 36 matched healthy subjects (HS) underwent 3T magnetic resonance imaging, including 3D T1-weighted and diffusion tensor imaging (DTI). Fractional anisotropy (FA) and mean diffusivity (MD) were calculated within each lobule and in the cerebellar peduncles. We investigated the correlations between cognitive outcomes and the diffusion parameters of cerebellar sub-structures and performed multiple linear regression analysis to predict cognitive disability.

RESULTS

FA was generally lower and MD was higher in the cerebellum and specifically in the vermis Crus II, lobules VIIb and VIIIb in CIPwMS compared with PwCIS and HS. In hierarchical regression analyses, 31% of the working memory z score variance was explained by FA in the left lobule VI and in the left superior peduncle. Working memory was also associated with MD in the vermis Crus II. FA in the left lobule VI and right VIIIa predicted part of the information processing speed (IPS) z scores.

CONCLUSION

DTI indicators of cerebellar microstructural damage were associated with cognitive deficits in MS. Our results suggested that cerebellar lobular alterations have an impact on attention, working memory and IPS.

Bilateral effects of unilateral cerebellar lesions as detected by voxel based morphometry and diffusion imaging

Over the last decades, the importance of cerebellar processing for cortical functions has been acknowledged and consensus was reached on the strict functional and structural cortico-cerebellar interrelations. From an anatomical point of view strictly contralateral interconnections link the cerebellum to the cerebral cortex mainly through the middle and superior cerebellar peduncle. Diffusion MRI (dMRI) based tractography has already been applied to address cortico-cerebellar-cortical loops in healthy subjects and to detect diffusivity alteration patterns in patients with neurodegenerative pathologies of the cerebellum. In the present study we used dMRI-based tractography to determine the degree and pattern of pathological changes of cerebellar white matter microstructure in patients with focal cerebellar lesions. Diffusion imaging and high-resolution volumes were obtained in patients with left cerebellar lesions and in normal controls. Middle cerebellar peduncles and superior cerebellar peduncles were reconstructed by multi fiber diffusion tractography. From each tract, measures of microscopic damage were assessed, and despite the presence of unilateral lesions, bilateral diffusivity differences in white matter tracts were found comparing patients with normal controls. Consistently, bilateral alterations were also evidenced in specific brain regions linked to the cerebellum and involved in higher-level functions. This could be in line with the evidence that in the presence of unilateral cerebellar lesions, different cognitive functions can be affected and they are not strictly linked to the side of the cerebellar lesion.

Neural substrates of motor and cognitive dysfunctions in SCA2 patients: A network based statistics analysis

Spinocerebellar ataxia type 2 (SCA2) is an autosomal dominant neurodegenerative disease characterized by a progressive cerebellar syndrome, which can be isolated or associated with extracerebellar signs. It has been shown that patients affected by SCA2 present also cognitive impairments and psychiatric symptoms.

The cerebellum is known to modulate cortical activity and to contribute to distinct functional networks related to higher-level functions beyond motor control. It is therefore conceivable that one or more networks, rather than isolated regions, may be dysfunctional in cerebellar degenerative diseases and that an abnormal connectivity within specific cerebello-cortical regions might explain the widespread deficits typically observed in patients.

In the present study, the network-based statistics (NBS) approach was used to assess differences in functional connectivity between specific cerebellar and cerebral “nodes” in SCA2 patients. Altered inter-nodal connectivity was found between more posterior regions in the cerebellum and regions in the cerebral cortex clearly related to cognition and emotion. Furthermore, more anterior cerebellar lobules showed altered inter-nodal connectivity with motor and somatosensory cerebral regions. The present data suggest that in SCA2 a cerebellar dysfunction affects long-distance cerebral regions and that the clinical symptoms may be specifically related with connectivity changes between motor and non-motor cerebello-cortical nodes.

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A cerebellar dysfunction affects long-distance cerebral regions in SCA2 patients.

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Connectivity changes affect sensorimotor and cognitive cerebello-cortical nodes.

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Cerebellar symptoms may be related to altered cerebello-cerebral connectivity.

Impact of cerebellar atrophy on cortical gray matter and cerebellar peduncles as assessed by voxel-based morphometry and high angular resolution diffusion imaging

In recent years the cerebellum has been attributed amore important role in higher-level functions than previously believed. We examined a cohort of patients suffering from cerebellar atrophy resulting in ataxia, with two main objectives: first to investigate which regions of the cerebrum were affected by the cerebellar degeneration, and second to assess whether diffusion magnetic resonance imaging (dMRI) metrics within the medial (MCP) and superior cerebellar peduncle (SCP) - namely fractional anisotropy (FA) and radial diffusivity (RD) - could be used as a biomarker in patients with this condition. Structural and dMRI data of seven patients with cerebellar atrophy (2 with spinocerebellar atrophy type 2, 1 with Friedreich's ataxia, 4 with idiopathic cerebellar ataxia) and no visible cortical lesions or cortical atrophy were investigated with Freesurfer and voxel-based morphometry (VBM) of gray matter (GM) as well as MCP and SCP FA maps. Correlations of MCP and SCP mean FA with ataxia scores and subscores were also evaluated. Freesurfer showed that patients had significantly reduced volume of the thalamus, ventral diencephalon and pallidum. VBM also demonstrated significantly lower local GM volumes in patients, notably in the head of the caudate nucleus, posterior cingulate gyrus and orbitofrontal cortex bilaterally, as well as in Broca's area in the left hemisphere, and a significant increase in RD in the MCP and SCP of both hemispheres. A significant correlation was found between MCP mean FA and total ataxia score (R=-0.7, p=0.03), and subscores for kinetic functions (R=-0.74, p=0.03) and oculomotor disorders (R=-0.70, p=0.04). The regions of the cerebrum found to have significantly lower local GM volumes have been described to be involved in higher-level cerebellar functions such as initiation of voluntary movements, emotional control, memory retrieval and general cognition. Our findings corroborate recent research pointing to a more extensive corticocerebellar system than previously thought. The significant difference in the MCP and SCP dMRI metrics between patients and controls as well as the significant correlation with ataxia total score and subscores support the use of dMRI metrics as an imaging biomarker for cerebellar degeneration and ataxia.

Location of lesion determines motor vs. cognitive consequences in patients with cerebellar stroke

Cerebellar lesions can cause motor deficits and/or the cerebellar cognitive affective syndrome (CCAS; Schmahmann's syndrome). We used voxel-based lesion-symptom mapping to test the hypothesis that the cerebellar motor syndrome results from anterior lobe damage whereas lesions in the posterolateral cerebellum produce the CCAS. Eighteen patients with isolated cerebellar stroke (13 males, 5 females; 20-66 years old) were evaluated using measures of ataxia and neurocognitive ability. Patients showed a wide range of motor and cognitive performance, from normal to severely impaired; individual deficits varied according to lesion location within the cerebellum. Patients with damage to cerebellar lobules III-VI had worse ataxia scores: as predicted, the cerebellar motor syndrome resulted from lesions involving the anterior cerebellum. Poorer performance on fine motor tasks was associated primarily with strokes affecting the anterior lobe extending into lobule VI, with right-handed finger tapping and peg-placement associated with damage to the right cerebellum, and left-handed finger tapping associated with left cerebellar damage. Patients with the CCAS in the absence of cerebellar motor syndrome had damage to posterior lobe regions, with lesions leading to significantly poorer scores on language (e.g. right Crus I and II extending through IX), spatial (bilateral Crus I, Crus II, and right lobule VIII), and executive function measures (lobules VII-VIII). These data reveal clinically significant functional regions underpinning movement and cognition in the cerebellum, with a broad anterior-posterior distinction. Motor and cognitive outcomes following cerebellar damage appear to reflect the disruption of different cerebro-cerebellar motor and cognitive loops.

The role of the cerebellum in multiple sclerosis

In multiple sclerosis (MS), cerebellar signs and symptoms as well as cognitive dysfunction are frequent and contribute to clinical disability with only poor response to symptomatic treatment. The current consensus paper highlights the broad range of clinical signs and symptoms of MS patients, which relate to cerebellar dysfunction. There is considerable evidence of cerebellar involvement in MS based on clinical, histopathological as well as structural and functional magnetic resonance imaging (MRI) studies. The review of the recent literature, however, also demonstrates a high variability of results. These discrepancies are, at least partially, caused by the use of different techniques and substantial heterogeneity among the patient cohorts in terms of disease duration, number of patients, and progressive vs. relapsing disease courses. Moreover, the majority of studies were cross-sectional, providing little insight into the dynamics of cerebellar involvement in MS. Some links between the histopathological changes, the structural and functional abnormalities as captured by MRI, cerebellar dysfunction, and the clinical consequences are starting to emerge and warrant further study. A consensus is formed that this line of research will benefit from advances in neuroimaging techniques that allow to trace cerebellar involvement at higher resolution. Using a prospective study design, multimodal high-resolution cerebellar imaging is highly promising, particularly in patients who present with radiologically or clinically isolated syndromes or newly diagnosed MS.

The neurocognitive profile of the cerebellum in multiple sclerosis

In recent years, a high number of studies have demonstrated that neuropsychological functions are altered in multiple sclerosis (MS) patients with cerebellar lesions, mainly including attention, working memory and verbal fluency. Since the present literature is often elusive on this topic, we aim to provide a comprehensive report about the real impact of cerebellar damages (evaluated as volume, lesions or connectivity measures) on cognitive functions. In particular in this review, we report and discuss recent works from 2009 to 2015, which have demonstrated the key role of the cerebellum in cognitive impairment of MS patients.

Cerebellar damage impairs executive control and monitoring of movement generation

Executive control of motor responses is a psychological construct of the executive system. Several studies have demonstrated the involvement of the cerebral cortex, basal ganglia, and thalamus in the inhibition of actions and monitoring of performance. The involvement of the cerebellum in cognitive function and its functional interaction with basal ganglia have recently been reported. Based on these findings, we examined the hypothesis of cerebellar involvement in executive control by administering a countermanding task in patients with focal cerebellar damage. The countermanding task requires one to make a movement in response to a 'go' signal and to halt it when a 'stop' signal is presented. The duration of the go process (reaction time; RT), the duration of the stop process (stop signal reaction time; SSRT), and their relationship, expressed by a psychometric function, are recorded as measures of executive control. All patients had longer go process duration in general and in particular, as a proactive control, as demonstrated by the increase in RT after erroneously performed stop trials. Further, they were defective in the slope of the psychometric function indicating a difficulty on triggering the stop process, although the SSRT did not differ from controls. Notably, their performance was worse when lesions affected deep cerebellar nuclei. Our results support the hypothesis that the cerebellum regulates the executive control of voluntary actions. We speculate that its activity is attributed to specific cerebellar influence over the cortico-striatal loop.

MR imaging and cognitive correlates of relapsing-remitting multiple sclerosis patients with cerebellar symptoms

Multiple sclerosis (MS) is a demyelinating disease affecting the central nervous system, frequently associated with cognitive impairments. Damages of the cerebellum are very common features of patients with MS, although the impact of this clinical factor is generally neglected. Recent evidence from our group demonstrated that MS patients with cerebellar damages are characterized by selective cognitive dysfunctions related to attention and language abilities. Here, we aimed at investigating the presence of neuroanatomical abnormalities in relapsing-remitting MS patients with (RR-MSc) and without (RR-MSnc) cerebellar signs. Twelve RR-MSc patients, 14 demographically, clinically, and radiologically, matched RR-MSnc patients and 20 controls were investigated. All patients underwent neuropsychological assessment. After refilling of FLAIR lesions on the 3D T1-weighted images, VBM was performed using SPM8 and DARTEL. A correlation analysis was performed between VBM results and neuropsychological variables characterizing RR-MSc patients. Despite a similar clinical status, RR-MSc patients were characterized by more severe cognitive damages in attention and language domains with respect to RR-MSnc and controls. With respect to controls, RR-MSnc patients were characterized by a specific atrophy of the bilateral thalami that became more widespread (including motor cortex) in the RR-MSc group (FWE < 0.05). However, consistent with their well-defined neuropsychological deficits, RR-MSc group showed atrophies in the prefrontal and temporal cortical areas when directly compared with RR-MSnc group. Our results demonstrated that RR-MS patients having cerebellar signs were characterized by a distinct neuroanatomical profile, mainly involving cortical regions underpinning executive functions and verbal fluency.

Neurochemical deficits in the cerebellar vermis in child offspring of parents with bipolar disorder

OBJECTIVES

We aimed to compare concentrations of N-acetyl aspartate, myo-inositol, and other neurometabolites in the cerebellar vermis of offspring at risk for bipolar disorder (BD) and healthy controls to examine whether changes in these neuronal metabolite concentrations occur in at-risk offspring prior to the onset of mania.

METHODS

A total of 22 children and adolescents aged 9-17 years with a familial risk for bipolar I or II disorder [at-risk offspring with non-bipolar I disorder mood symptoms (AR)], and 25 healthy controls (HC) were examined using proton magnetic resonance spectroscopy at 3T to study metabolite concentrations in an 8-cc voxel in the cerebellar vermis.

RESULTS

Decreased myo-inositol and choline concentrations in the vermis were seen in the AR group compared to HC (p<0.01).

CONCLUSIONS

Decreased cellular metabolism and interference with second messenger pathways may be present in the cerebellar vermis in youth at risk for BD as evident by decreased myo-inositol and choline concentrations in this region. These results may be limited by a cross-sectional design, co-occurring diagnoses, and medication exposure. Longitudinal studies are necessary to determine whether early neurochemical changes can predict the development of mania. Improved methods for identifying children with certain neurochemical vulnerabilities may inform preventive and early intervention strategies prior to the onset of mania.

Past, present and future therapeutics for cerebellar ataxias

Cerebellar ataxias are a group of disabling neurological disorders. Patients exhibit a cerebellar syndrome and can also present with extra-cerebellar deficits, namely pigmentary retinopathy, extrapyramidal movement disorders, pyramidal signs, cortical symptoms (seizures, cognitive impairment/behavioural symptoms), and peripheral neuropathy. Recently, deficits in cognitive operations have been unraveled. Cerebellar ataxias are heterogeneous both at the phenotypic and genotypic point of view. Therapeutical trials performed during these last 4 decades have failed in most cases, in particular because drugs were not targeting a deleterious pathway, but were given to counteract putative defects in neurotransmission. The identification of the causative mutations of many hereditary ataxias, the development of relevant animal models and the recent identifications of the molecular mechanisms underlying ataxias are impacting on the development of new drugs. We provide an overview of the pharmacological treatments currently used in the clinical practice and we discuss the drugs under development.

The Bereitschaftspotential in essential tremor

OBJECTIVE

Essential tremor (ET) is an involuntary postural oscillation. It is unclear to which extent motor cortical activity in preparation of volitional movement is abnormal in ET. We measured the Bereitschaftspotential (BP) to address this question.

METHODS

Given the known influence of the cerebello-dentato-thalamo-cortical projection in the generation of the BP, patients were divided into two groups, defined by purely postural tremor (ET(PT)) or additional presence of intention tremor (ET(IT)) and compared to healthy controls. BP was recorded during self-paced rapid wrist extension movements.

RESULTS

The late BP (500-0 ms before movement onset) was increased over the mid-frontal area in ET(PT), whereas it was reduced over the mid-parietal area in ET(IT) when compared to healthy controls. In addition, the late BP was reduced over a widespread centro-parietal area in ET(IT) compared to ET(PT).

CONCLUSIONS

Findings suggest that presence vs. absence of cerebellar signs (intention tremor) in ET results in differential affection of volitional preparatory motor cortical activity. The BP increase in ET(PT) may indicate compensatory activity, whereas the widespread centro-parietal BP reduction in ET(IT) suggests dysfunction of the cerebello-dentato-thalamo-cortical projection.

SIGNIFICANCE

Reduction of the late BP amplitude may serve as a surrogate marker for dysfunction of the cerebello-dentato-thalamo-cortical projection in ET.