The clinical diagnosis of autosomal dominant spinocerebellar ataxias

A novel CACNA1A R2201W variant in a woman with hemiplegic migraine

INTRODUCTION

Familial hemiplegic migraine type 1 (FHM1) is a monogenic rare disease that is characterized by migraine attacks accompanied by unilateral weakness and is caused by mutations in the CACNA1A gene. We report the case of a patient with a clinical history consistent with hemiplegic migraine who underwent genetic testing that revealed a variant in the CACNA1A gene.

CASE PRESENTATION

A 68-year-old woman was evaluated for progressive postural instability and subjective cognitive decline. She had suffered from recurrent migraine episodes accompanied by fully reversible unilateral weakness that had started around the age of thirty and had fully disappeared at the time of evaluation. Magnetic resonance imaging (MRI) showed an extensive leukoencephalopathy, with features suggestive of small vessel disease, significantly progressing over the years. Exome sequencing revealed the heterozygous variant c.6601C>T (p.Arg2201Trp) in the CACNA1A gene. This variant, located in a highly conserved region, causes the substitution of arginine with tryptophan at codon 2202 of exon 47, with a high likelihood of a damaging effect on protein activity and/or structure.

DISCUSSION

This is the first report describing the missense mutation c.6601C>T (p.Arg2201Trp) in heterozygosity in the CACNA1A gene in a patient with clinical features of hemiplegic migraine. The presence of a diffuse leukoencephalopathy on MRI is not typical of hemiplegic migraine and may suggest a phenotypic variant related to this mutation or result from the combined effect of the patient's comorbidities.

The genotype-phenotype correlations of the CACNA1A-related neurodevelopmental disorders: a small case series and literature reviews

BACKGROUND

Genotype-phenotype correlations of the CACNA1A-related neurodevelopmental disorders such as global developmental delay (GDD)/intellectual disability (ID), epileptic encephalopathy (EE), and autism spectrum disorder (ASD) are unknown. We aimed to summarize genotype-phenotype correlations and potential treatment for CACNA1A-related neurodevelopmental disorders.

METHODS

Six children diagnosed with CACNA1A-related neurodevelopmental disorders at Xiangya Hospital, Central South University from April 2018 to July 2021 were enrolled. The PubMed database was systematically searched for all reported patients with CACNA1A-related neurodevelopmental disorders until February 2023. Thereafter, we divided patients into several groups for comparison.

RESULTS

Six patients were recruited from our hospital. Three cases presented with epilepsy, five with GDD/ID, five with ataxia, and two with ASD. The variants included p.G701R, p.R279C, p.D1644N, p.Y62C, p.L1422Sfs*8, and p. R1664Q [two gain-of-function (GOF) and four loss-of-function (LOF) variants]. About 187 individuals with GDD/ID harboring 123 variants were found (case series plus data from literature). Of those 123 variants, p.A713T and p.R1664* were recurrent, 37 were LOF, and 7 were GOF. GOF variants were linked with severe-profound GDD/ID while LOF variants were associated with mild-moderate GDD/ID (p = 0.001). The p.A713T variant correlated with severe-profound GDD/ID (p = 0.003). A total of 130 epileptic patients harboring 83 variants were identified. The epileptic manifestations included status epilepticus (n = 64), provoked seizures (n = 49), focal seizures (n = 37), EE (n = 29), absence seizures (n = 26), and myoclonic seizures (n = 10). About 49 (42.20%) patients had controlled seizures while 67 (57.80%) individuals remained with refractory seizures. Status epilepticus correlated with variants located on S4, S5, and S6 (p = 0.000). Among the 83 epilepsy-related variants, 23 were recurrent, 32 were LOF, and 11 were GOF. Status epilepticus was linked with GOF variants (p = 0.000). LOF variants were associated with absence seizures (p = 0.000). Six patients died at an early age (3 months to ≤5 years). We found 18 children with ASD. Thirteen variants including recurrent ones were identified in those 18 cases. GOF changes were more linked to ASD.

CONCLUSION

The p.A713T variant is linked with severe-profound GDD/ID. More than half of CACNA1A-related epilepsy is refractory. The most common epileptic manifestation is status epilepticus, which correlates with variants located on S4, S5, and S6.

Validity of balance measures in cerebellar ataxia: A prospective study with 12-month follow-up

INTRODUCTION

Balance deficits are common in cerebellar ataxia. Determining which balance outcome measures are psychometrically strong for this population remains an unmet need.

OBJECTIVE

Evaluate the validity and responsiveness of two clinic-based balance measures [Berg Balance Scale (BBS) and balance sub-component of the Scale for the Assessment and Rating of Ataxia (SARA-bal)] and two laboratory-based balance measures [Sensory Organization Test (SOT) and Limits of Stability (LOS)] in cerebellar ataxia.

DESIGN

Prospective cohort study.

SETTING

Institutional study assessing 40 participants with cerebellar ataxia at baseline, 6, and 12 months.

MAIN OUTCOME MEASURES

Balance was assessed using the BBS, SARA-bal, SOT, and LOS; disease severity was assessed using the SARA; and Patients' Global Impression of Change (PGIC) was used to estimate responsiveness to disease progress at 6 and 12 months.

RESULTS

BBS and SARA-bal (Spearman's correlation coefficient, ρS = -0.89, p < 0.01) demonstrated strong criterion validity. Convergent validity was moderate to high (ρS range:-0.75 to 0.92) and external validity was low (ρS range:-0.75 to 0.11). Composite SOT scores (SOT-COM; ρS=0.29, p<0.01) and maximal excursion (MXE-LOS) in the forward (F) and right (R) directions of the LOS (ρS = 0.18, p < 0.01) demonstrated moderate to low criterion and convergent validity. The area under the receiver operating characteristic curve (AUC_ROC ) and its effect size (standard response mean [SRM]) for categorizing 'stable' and 'worsened' patients at 6 and 12 months were satisfactory for the BBS (AUC_ROC :0.75; SRM-Stable:1.06; SRM-Worsened:1.16), SARA-bal (AUC_ROC :0.76; SRM-Stable:0.86; SRM-Worsened:0.85), and MXE-LOS(R) (AUC_ROC :0.29; SRM-Stable:0.41; SRM-Worsened:1.39).

CONCLUSION

BBS and SARA-bal have moderate to strong criterion and convergent validity and adequate responsiveness to balance changes. Both laboratory-based measures (SOT and LOS) demonstrated a high floor effect. The SOT-COM and MXE-LOS(R) demonstrated moderate to low criterion validity, with only the MXE-LOS(R) displaying adequate responsiveness to balance changes after 6 and 12 months. This article is protected by copyright. All rights reserved.

MRI CNS Atrophy Pattern and the Etiologies of Progressive Ataxias

MRI shows the three archetypal patterns of CNS volume loss underlying progressive ataxias in vivo, namely spinal atrophy (SA), cortical cerebellar atrophy (CCA) and olivopontocerebellar atrophy (OPCA). The MRI-based CNS atrophy pattern was reviewed in 128 progressive ataxias. A CNS atrophy pattern was identified in 91 conditions: SA in Friedreich’s ataxia, CCA in 5 acquired and 72 (24 dominant, 47 recessive,1 X-linked) inherited ataxias, OPCA in Multi-System Atrophy and 12 (9 dominant, 2 recessive,1 X-linked) inherited ataxias. The MRI-based CNS atrophy pattern may be useful for genetic assessment, identification of shared cellular targets, repurposing therapies or the enlargement of drug indications in progressive ataxias.

Construction of Longitudinally Consistent 4D Infant Cerebellum Atlases Based on Deep Learning

Longitudinal infant dedicated cerebellum atlases play a fundamental role in characterizing and understanding the dynamic cerebellum development during infancy. However, due to the limited spatial resolution, low tissue contrast, tiny folding structures, and rapid growth of the cerebellum during this stage, it is challenging to build such atlases while preserving clear folding details. Furthermore, the existing atlas construction methods typically independently build discrete atlases based on samples for each age group without considering the within-subject temporal consistency, which is critical for large-scale longitudinal studies. To fill this gap, we propose an age-conditional multi-stage learning framework to construct longitudinally consistent 4D infant cerebellum atlases. Specifically, 1) A joint affine and deformable atlas construction framework is proposed to accurately build temporally continuous atlases based on the entire cohort, and rapidly warp the new images to the atlas space; 2) A longitudinal constraint is employed to enforce the within-subject temporal consistency during atlas building; 3) A Correntropy based regularization loss is further exploited to enhance the robustness of our framework. Our atlases are constructed based on 405 longitudinal scans from 187 healthy infants with age ranging from 6 to 27 months, and are compared to the atlases built by state-of-the-art algorithms. Results demonstrate that our atlases preserve more structural details and fine-grained cerebellum folding patterns, which ensure higher accuracy in subsequent atlas-based registration and segmentation tasks.

From Genotype to Phenotype: Expanding the Clinical Spectrum of CACNA1A Variants in the Era of Next Generation Sequencing

Ion channel dysfunction is a key pathological substrate of episodic neurological disorders. A classical gene associated to paroxysmal movement disorders is CACNA1A, which codes for the pore-forming subunit of the neuronal calcium channel P/Q. Non-polyglutamine CACNA1A variants underlie familial hemiplegic ataxia type 1 (FHM1) and episodic ataxia type 2 (EA2). Classical paroxysmal manifestations of FHM1 are migraine attacks preceded by motor aura consisting of hemiparesis, aphasia, and disturbances of consciousness until coma. Patients with EA2 suffer of recurrent episodes of vertigo, unbalance, diplopia, and vomiting. Beyond these typical presentations, several reports highlighted manifold clinical features associated with P/Q channelopathies, from chronic progressive cerebellar ataxia to epilepsy and psychiatric disturbances. These manifestations may often outlast the burden of classical episodic symptoms leading to pitfalls in the diagnostic work-up. Lately, the spreading of next generation sequencing techniques linked de novo CACNA1A variants to an even broader phenotypic spectrum including early developmental delay, autism spectrum disorders, epileptic encephalopathy, and early onset paroxysmal dystonia. The age-dependency represents a striking new aspect of these phenotypes und highlights a pivotal role for P/Q channels in the development of the central nervous system in a defined time window. While several reviews addressed the clinical presentation and treatment of FHM1 and EA2, an overview of the newly described age-dependent manifestations is lacking. In this Mini-Review we present a clinical update, delineate genotype-phenotype correlations as well as summarize evidence on the pathophysiological mechanisms underlying the expanded phenotype associated with CACNA1A variants.

Toward a unified analysis of cerebellum maturation and aging across the entire lifespan: A MRI analysis

Previous literature about the structural characterization of the human cerebellum is related to the context of a specific pathology or focused in a restricted age range. In fact, studies about the cerebellum maturation across the lifespan are scarce and most of them considered the cerebellum as a whole without investigating each lobule. This lack of study can be explained by the lack of both accurate segmentation methods and data availability. Fortunately, during the last years, several cerebellum segmentation methods have been developed and many databases comprising subjects of different ages have been made publically available. This fact opens an opportunity window to obtain a more extensive analysis of the cerebellum maturation and aging. In this study, we have used a recent state‐of‐the‐art cerebellum segmentation method called CERES and a large data set (N = 2,831 images) from healthy controls covering the entire lifespan to provide a model for 12 cerebellum structures (i.e., lobules I‐II, III, IV, VI, Crus I, Crus II, VIIB, VIIIA, VIIIB, IX, and X). We found that lobules have generally an evolution that follows a trajectory composed by a fast growth and a slow degeneration having sometimes a plateau for absolute volumes, and a decreasing tendency (faster in early ages) for normalized volumes. Special consideration is dedicated to Crus II, where slow degeneration appears to stabilize in elder ages for absolute volumes, and to lobule X, which does not present any fast growth during childhood in absolute volumes and shows a slow growth for normalized volumes.

Eye movement changes in autosomal dominant spinocerebellar ataxias

Oculomotor abnormalities are common findings in spinocerebellar ataxias (SCAs), a clinically heterogeneous group of neurodegenerative disorders with an autosomal dominant pattern of inheritance. Usually, cerebellar impairment accounts for most of the eye movement changes encountered; as the disease progresses, the involvement of extracerebellar structures typically seen in later stages may modify the oculomotor progression. However, ocular movement changes are rarely specific. In this regard, some important exceptions include the prominent slowing of horizontal eye movements in SCA2 and, to a lesser extent, in SCA3, SCA4, and SCA28, or the executive deficit in SCA2 and SCA17. Here, we report the eye movement abnormalities and neurological pictures of SCAs through a review of the literature. Genetic and neuropathological/neuroimaging aspects are also briefly discussed. Overall, the findings reported indicate that oculomotor analysis could be of help in differential diagnosis among SCAs and contribute to clarify the role of brain structures, particularly the cerebellum, in oculomotor control.

Cardiovascular autonomic testing in the work-up of cerebellar ataxia: insight from an observational single center study

Background

Cerebellar ataxias are a heterogeneous group of disorders of both genetic and non-genetic origin. In sporadic cases, two entities are recognized: multiple system atrophy of cerebellar type (MSA-C) and SAOA (sporadic adult-onset ataxia). The presence of severe cardiovascular autonomic failure reliably distinguishes MSA-C from other ataxias, but it may appear only late in the disease course.

Objective

To evaluate the diagnostic yield of cardiovascular autonomic function tests in the work-up of cerebellar ataxia.

Methods

We applied a cardiovascular autonomic tests battery in consecutive patients with neurodegenerative cerebellar ataxia and matched healthy controls. We recorded the presence of both orthostatic hypotension (OH) and blood pressure falls non-fulfilling the criteria of OH (non-OH BP). Sporadic cases were followed-up for an eventual conversion to MSA-C.

Results

Forty-two patients were recruited, 19 of whom with sporadic disease (2 probable MSA-C, 6 possible MSA-C, 11 SAOA). Sporadic and hereditary cases showed no difference concerning ataxia severity at baseline. At head-up tilt, non-OH BP falls were detected in nine patients, but not in controls. This finding was significantly more frequent in sporadic cases (p = 0.006) and was detected in five out of seven patients that during follow-up converted to possible/probable MSA-C. Findings at standing test were normal in four out of nine cases with non-OH BP falls at head-up tilt.

Conclusions

A complete cardiovascular autonomic battery with head-up tilt can detect early signs of BP dysregulation which may be missed at bed-side tests, thus warranting its application in the first line work-up of cerebellar ataxias.

Electronic supplementary material

The online version of this article (10.1007/s00415-019-09684-4) contains supplementary material, which is available to authorized users.

Neuroradiological Findings in the Spinocerebellar Ataxias

Background

The spinocerebellar ataxias (SCAs) are a group of autosomal dominant degenerative diseases characterized by cerebellar ataxia. Classified according to gene discovery, specific features of the SCAs – clinical, laboratorial, and neuroradiological (NR) – can facilitate establishing the diagnosis. The purpose of this study was to review the particular NR abnormalities in the main SCAs.

Methods

We conducted a literature search on this topic.

Results

The main NR characteristics of brain imaging (magnetic resonance imaging or computerized tomography) in SCAs were: (1) pure cerebellar atrophy; (2) cerebellar atrophy with other findings (e.g., pontine, olivopontocerebellar, spinal, cortical, or subcortical atrophy; “hot cross bun sign”, and demyelinating lesions); (3) selective cerebellar atrophy; (4) no cerebellar atrophy.

Discussion

The main NR abnormalities in the commonest SCAs, are not pathognomonic of any specific genotype, but can be helpful in limiting the diagnostic options. We are progressing to a better understanding of the SCAs, not only genetically, but also pathologically; NR is helpful in the challenge of diagnosing the specific genotype of SCA.

Spinocerebellar ataxias: prospects and challenges for therapy development

The spinocerebellar ataxias (SCAs) comprise more than 40 autosomal dominant neurodegenerative disorders that present principally with progressive ataxia. Within the past few years, studies of pathogenic mechanisms in the SCAs have led to the development of promising therapeutic strategies, especially for SCAs caused by polyglutamine-coding CAG repeats. Nucleotide-based gene-silencing approaches that target the first steps in the pathogenic cascade are one promising approach not only for polyglutamine SCAs but also for the many other SCAs caused by toxic mutant proteins or RNA. For these and other emerging therapeutic strategies, well-coordinated preparation is needed for fruitful clinical trials. To accomplish this goal, investigators from the United States and Europe are now collaborating to share data from their respective SCA cohorts. Increased knowledge of the natural history of SCAs, including of the premanifest and early symptomatic stages of disease, will improve the prospects for success in clinical trials of disease-modifying drugs. In addition, investigators are seeking validated clinical outcome measures that demonstrate responsiveness to changes in SCA populations. Findings suggest that MRI and magnetic resonance spectroscopy biomarkers will provide objective biological readouts of disease activity and progression, but more work is needed to establish disease-specific biomarkers that track target engagement in therapeutic trials. Together, these efforts suggest that the development of successful therapies for one or more SCAs is not far away.

A diagnostic decision tree for adult cerebellar ataxia based on pontine magnetic resonance imaging

Cerebellar ataxias (CAs) are heterogeneous conditions often require differential diagnosis. This study aimed to establish a diagnostic decision tree for differentiating CAs based on pontine MRI findings. Two-hundred and two consecutive ataxia patients were clinically classified into 4 groups: (1) spinocerebellar ataxia (SCA) with brainstem involvement (SCA-BSI), (2) Pure cerebellar SCA, (3) cerebellar dominant multiple system atrophy (MSA-c), and (4) Other CA. Signal intensity in pons was graded into 3 types: hot cross bun sign (HCBS), pontine midline linear T2-hyperintensity (PMH), or normal. The distance ratio of pontine base to tegmentum, named "BT-ratio", was measured. The presence of HCBS indicated either MSA-c with a specificity of 97.7%, or SCA2. When PMH was observed, a BT-ratio above 3.54 strongly indicated SCA-BSI, namely Machado-Joseph disease, SCA1, or dentatorubral-pallidoluysian atrophy, whereas a BT-ratio below 3.54 indicated MSA-c or SCA2. When the signal intensity was normal, a BT-ratio above 3.52 indicated SCA-BSI, whereas a BT-ratio below 3.52 suggested Pure cerebellar SCA or Other CA with pure cerebellar type. The decision tree was confirmed useful in a different 30 CA patients. We propose that differential diagnosis of CAs can be supported by combining pontine MRI signal intensity changes and BT-ratio.

Postural Tremor and Ataxia Progression in Spinocerebellar Ataxias

BACKGROUND

Postural tremor can sometimes occur in spinocerebellar ataxias (SCAs). However, the prevalence and clinical characteristics of postural tremor in SCAs are poorly understood, and whether SCA patients with postural tremor have different ataxia progression is not known.

METHODS

We studied postural tremor in 315 patients with SCA1, 2, 3, and 6 recruited from the Clinical Research Consortium for Spinocerebellar Ataxias (CRC-SCA), which consists of 12 participating centers in the United States, and we evaluated ataxia progression in these patients from January 2010 to August 2012.

RESULTS

Among 315 SCA patients, postural tremor was most common in SCA2 patients (SCA1, 5.8%; SCA2, 27.5%; SCA3, 12.4%; SCA6, 16.9%; p = 0.007). SCA3 patients with postural tremor had longer CAG repeat expansions than SCA3 patients without postural tremor (73.67 ± 3.12 vs. 70.42 ± 3.96, p = 0.003). Interestingly, SCA1 and SCA6 patients with postural tremor had a slower rate of ataxia progression (SCA1, β = -0.91, p < 0.001; SCA6, β = -1.28, p = 0.025), while SCA2 patients with postural tremor had a faster rate of ataxia progression (β = 1.54, p = 0.034). We also found that the presence of postural tremor in SCA2 patients could be influenced by repeat expansions of ATXN1 (β = -1.53, p = 0.037) and ATXN3 (β = 0.57, p = 0.018), whereas postural tremor in SCA3 was associated with repeat lengths in TBP (β = 0.63, p = 0.041) and PPP2R2B (β = -0.40, p = 0.032).

DISCUSSION

Postural tremor could be a clinical feature of SCAs, and the presence of postural tremor could be associated with different rates of ataxia progression. Genetic interactions between ataxia genes might influence the brain circuitry and thus affect the clinical presentation of postural tremor.

MTCL1 plays an essential role in maintaining Purkinje neuron axon initial segment

The axon initial segment (AIS) is a specialized domain essential for neuronal function, the formation of which begins with localization of an ankyrin-G (AnkG) scaffold. However, the mechanism directing and maintaining AnkG localization is largely unknown. In this study, we demonstrate that in vivo knockdown of microtubule cross-linking factor 1 (MTCL1) in cerebellar Purkinje cells causes loss of axonal polarity coupled with AnkG mislocalization. MTCL1 lacking MT-stabilizing activity failed to restore these defects, and stable MT bundles spanning the AIS were disorganized in knockdown cells. Interestingly, during early postnatal development, colocalization of MTCL1 with these stable MT bundles was observed prominently in the axon hillock and proximal axon. These results indicate that MTCL1-mediated formation of stable MT bundles is crucial for maintenance of AnkG localization. We also demonstrate that Mtcl1 gene disruption results in abnormal motor coordination with Purkinje cell degeneration, and provide evidence suggesting possible involvement of MTCL1 dysfunction in the pathogenesis of spinocerebellar ataxia.

A longitudinal investigation into cognition and disease progression in spinocerebellar ataxia types 1, 2, 3, 6, and 7

Background

The natural history of clinical symptoms in the spinocerebellar ataxias (SCA)s has been well characterised. However there is little longitudinal data comparing cognitive changes in the most common SCA subtypes over time. The present study provides a preliminary longitudinal characterisation of the clinical and cognitive profiles in patients with SCA1, SCA2, SCA3, SCA6 and SCA7, with the aim of elucidating the role of the cerebellum in cognition.

Methods

13 patients with different SCAs all caused by CAG repeat expansion (SCA1, n = 2; SCA2, n = 2; SCA3, n = 2; SCA6, n = 4; and SCA7, n = 3) completed a comprehensive battery of cognitive and mood assessments at two time points, a mean of 7.35 years apart. All patients were evaluated clinically using the Scale for the Rating and Assessment of Ataxia (SARA) and the Inventory of Non-Ataxia Signs (INAS). Patients underwent structural MRI imaging at follow-up.

Results

Clinical scale scores increased in all patients over time, most prominently in the SCA1 (SARA) and SCA3 (INAS) groups. New impairments on neuropsychological tests were most commonly observed with executive functions, speed, attention, visual memory and Theory of Mind. Results suggest possible differences in cognitive decline in SCA subtypes, with the most rapid cognitive decline observed in the SCA1 patients, and the least in the SCA6 patients, congruent with observed patterns of motor deterioration. Minimal changes in mood were observed, and MRI measures of atrophy did not correlate with cognitive decline.

Conclusion

As well as increasing physical impairment, cognitive decline over time appears to be a distinct aspect of the SCA phenotype, in keeping with the cerebellar cognitive-affective syndrome. Our data suggest a trend of cognitive decline that is different for each SCA subtype, and for the majority is related to the severity of cerebellar motor impairment.

Electronic supplementary material

The online version of this article (doi:10.1186/s13023-016-0447-6) contains supplementary material, which is available to authorized users.

High relative frequency of SCA1 in Poland reflecting a potential founder effect

Spinocerebellar ataxias (SCAs) have irregular distributions worldwide. SCA1 is the most frequent in Poland, and no cases of SCA3 of Polish origin has yet been identified. In view of such patterns of SCAs occurrence, the relative frequency, geographical distribution and a possible founder effect of SCA1 were investigated. DNA samples of 134 probands with SCA1 and 228 controls were analysed. The genotyping of four markers, D6S89, D6S109, D6S274, D6S288, around the ATXN1 gene (SCA1) and sequencing of the selected variant of D6S89 were performed. The relative frequency of SCA1 was 68 %. The studied SCA1 pedigrees were irregularly distributed, with the highest concentration in Central Poland. Haplotyping revealed the association of ATXN1 gene mutation with a 197-bp variant of D6S89 marker (63 % of probands) and with a 184-bp variant of DS6274 (50.7 % of probands). Out of 61 SCA1 probands from Mazowieckie, 41 carried the same 197-bp variant. SCA1 relative frequency in Poland shows the highest value compared with the data from other countries worldwide. Due to the association with the mutation obtained for the investigated markers and the SCA1 pedigrees concentration in Central Poland, we hypothesise that it represents a potential founder effect.

Ataxias with Autosomal, X-Chromosomal or Maternal Inheritance

Heredoataxias are a group of genetic disorders with a cerebellar syndrome as the leading clinical manifestation. The current classification distinguishes heredoataxias according to the trait of inheritance into autosomal dominant, autosomal recessive, X-linked, and maternally inherited heredoataxias. The autosomal dominant heredoataxias are separated into spinocerebellar ataxias (SCA1-8, 10-15, 17-23, 25-30, and dentato-rubro-pallido-luysian atrophy), episodic ataxias (EA1-7), and autosomal dominant mitochondrial heredoataxias (Leigh syndrome, MIRAS, ADOAD, and AD-CPEO). The autosomal recessive ataxias are separated into Friedreich ataxia, ataxia due to vitamin E deficiency, ataxia due to Abeta-lipoproteinemia, Refsum disease, late-onset Tay-Sachs disease, cerebrotendineous xanthomatosis, spinocerebellar ataxia with axonal neuropathy, ataxia telangiectasia, ataxia telangiectasia-like disorder, ataxia with oculomotor apraxia 1 and 2, spastic ataxia of Charlevoix-Saguenay, Cayman ataxia, Marinesco-Sjögren syndrome, and autosomal recessive mitochondrial ataxias (AR-CPEO, SANDO, SCAE, AHS, IOSCA, MEMSA, LBSL CoQ-deficiency, PDC-deficiency). Only two of the heredoataxias, fragile X/tremor/ataxia syndrome, and XLSA/A are transmitted via an X-linked trait. Maternally inherited heredoataxias are due to point mutations in genes encoding for tRNAs, rRNAs, respiratory chain subunits or single large scale deletions/duplications of the mitochondrial DNA and include MELAS, MERRF, KSS, PS, MILS, NARP, and non-syndromic mitochondrial disorders. Treatment of heredoataxias is symptomatic and supportive and may have a beneficial effect in single patients.

**Please see page 424 for abbreviation list.

Rapid automatic segmentation of the human cerebellum and its lobules (RASCAL)--implementation and application of the patch-based label-fusion technique with a template library to segment the human cerebellum

Reliable and fast segmentation of the human cerebellum with its complex architecture of lobes and lobules has been a challenge for the past decades. Emerging knowledge of the functional integration of the cerebellum in various sensori-motor and cognitive-behavioral circuits demands new automatic segmentation techniques, with accuracies similar to manual segmentations, but applicable to large subject numbers in a reasonable time frame. This article presents the development and application of a novel pipeline for rapid automatic segmentation of the human cerebellum and its lobules (RASCAL) combining patch-based label-fusion and a template library of manually labeled cerebella of 16 healthy controls from the International Consortium for Brain Mapping (ICBM) database. Leave-one-out experiments revealed a good agreement between manual and automatic segmentations (Dice kappa = 0.82). Intraclass correlation coefficients (ICC) were calculated to test reliability of segmented volumes and were highest (ICC > 0.9) for global measures (total and hemispherical grey and white matter) followed by larger lobules of the posterior lobe (ICC > 0.8). Further we applied the pipeline to all 152 young healthy controls of the ICBM database to look for hemispheric and gender differences. The results demonstrated larger native space volumes in men then women (mean (± SD) total cerebellar volume in women = 217 cm(3) (± 26), men = 259 cm(3) (± 29); P < 0.001). Significant gender-by-hemisphere interaction was only found in stereotaxic space volumes for white matter core (men > women) and anterior lobe volume (women > men). This new method shows great potential for the precise and efficient analysis of the cerebellum in large patient cohorts.

Spinocerebellar ataxias type 8, 12, and 17 and dentatorubro-pallidoluysian atrophy in Czech ataxic patients

Spinocerebellar ataxias (SCAs) are a heterogeneous group of neurodegenerative disorders currently associated with 27 genes. The most frequent types are caused by expansions in coding CAG repeats. The frequency of SCA subtypes varies among populations. We examined the occurrence of rare SCAs, SCA8, SCA12, SCA17 and dentatorubro-pallidoluysian atrophy (DRPLA), in the Czech population from where the data were missing. We analyzed causal gene expansions in 515 familial and sporadic ataxic patients negatively tested for SCA1-3 and SCA6-7. Pathogenic SCA8 and SCA17 expansions were identified in eight and five patients, respectively. Tay-Sachs disease was later diagnosed in one patient with an SCA8 expansion and the diagnosis of multiple sclerosis (MS) was suspected in two other patients with SCA8 expansions. These findings are probably coincidental, although the participation of SCA8 expansions in the susceptibility to MS and disease progression cannot be fully excluded. None of the patients had pathogenic SCA12 or DRPLA expansions. However, three patients had intermediate SCA12 alleles out of the normal range with 36 and 43 CAGs. Amyotrophic lateral sclerosis (ALS) was probable in the patient with 43 CAGs. This coincidence is remarkable, especially in the context with the recently identified predisposing role of longer SCA2 alleles in ALS. Five families with SCA17 represent a significant portion of ataxic patients and this should be reflected in the diagnostics of SCAs in the Czech population. SCA8 expansions must be considered after careful clinical evaluation.

Next-generation sequencing diagnostics for neurological diseases/disorders: from a clinical perspective

Neurological diseases encompass a broad, heterogeneous group of disorders ranging from pediatric neurodevelopmental diseases to late-onset neurodegenerative diseases, most of which are poorly understood and few of which are curable. Most of these diseases have a genetic basis and thus are expected to be amenable to genetic or genomic analysis by next-generation sequencing (NGS). While the advancement of contemporary technologies (such as NGS) is exciting, translating this tool into actual benefit for patients and clinicians can be challenging. In a clinical setting, a sequencing test that is fast, non-invasive, cheap and with perfect specificity would be ideal. However, in practice, there are several hurdles and caveats to consider even before a NGS diagnostic testing can be optimally applied. Proper definition of clinical phenotype, selection of the most appropriate subjects and the clinical setting, optimization of both sensitivity and specificity of the test, evaluation of the availability of the infrastructure and expertise, and consideration of economic, ethical and legal issues are vital in the final application of NGS diagnostic screening in the clinics.

Mouse models of polyglutamine diseases in therapeutic approaches: review and data table. Part II

Mouse models of human diseases are created both to understand the pathogenesis of the disorders and to find successful therapies for them. This work is the second part in a series of reviews of mouse models of polyglutamine (polyQ) hereditary disorders and focuses on in vivo experimental therapeutic approaches. Like part I of the polyQ mouse model review, this work is supplemented with a table that contains data from experimental studies of therapeutic approaches in polyQ mouse models. The aim of this review was to characterize the benefits and outcomes of various therapeutic strategies in mouse models. We examine whether the therapeutic strategies are specific to a single disease or are applicable to more than one polyQ disorder in mouse models. In addition, we discuss the suitability of mouse models in therapeutic approaches. Although the majority of therapeutic studies were performed in mouse models of Huntington disease, similar strategies were also used in other disease models.

Cerebellar ataxia: pathophysiology and rehabilitation

This series of articles for rehabilitation in practice aims to cover a knowledge element of the rehabilitation medicine curriculum. Nevertheless they are intended to be of interest to a multidisciplinary audience. The competency addressed in this article is 'The trainee consistently demonstrates a knowledge of management approaches for specific impairments including spasticity, ataxia.'

Clinical and genetic analysis of spinocerebellar ataxia in Mali

BACKGROUND

Autosomal dominant cerebellar ataxia, currently denominated spinocerebellar ataxia (SCAs), represents a heterogeneous group of neurodegenerative disorders affecting the cerebellum and its connections. We describe the clinical and molecular findings in 16 patients originating from Malian families, who suffer from progressive cerebellar ataxia syndrome.

METHODS AND RESULTS

Molecular analysis allows genetic profiles of SCA to be distinguished. In seven patients, SCA type 2 (CAG) mutation was expanded from 39 to 43 repeats. SCA type 7 (CAG) mutation was confirmed in six patients. Mutations were expanded from 49 to 59 repeats. In three patients, SCA type3 was diagnosed and CAG mutation was expanded to 73 repeats.

CONCLUSIONS

Our data suggest that the most frequent types of SCA are SCA2 and SCA7. However, further studies are needed to confirm these preliminary results.

Vestibulo-cerebellar disease impairs the central representation of self-orientation

Transformation of head-fixed otolith signals into a space-fixed frame of reference is essential for perception of self-orientation and ocular motor control. In monkeys the nodulus and ventral uvula of the vestibulo-cerebellum facilitate this transformation by computing an internal estimate of direction of gravity. These experimental findings motivated the hypothesis that degeneration of the vestibulo-cerebellum in humans alter perceptual and ocular motor functions that rely on accurate estimates of gravity, such as subjective visual vertical (SVV), static ocular counterroll (OCR), and gravity-dependent modulation of vertical ocular drifts. We assessed the SVV, OCR, and spontaneous vertical ocular drifts in 12 patients with chronic vestibulo-cerebellar disease and in 10 controls. Substantially increased variability in estimated SVV was noted in the patients. Furthermore, gravity-dependent modulation of spontaneous vertical ocular drifts along the pitch plane was significantly (p < 0.05) larger in the patients. However, the gain and variability of static OCR and errors in SVV were not significantly different. In conclusion, in chronic vestibulo-cerebellar disease SVV and OCR remain intact except for an abnormal variability in the perception of verticality and impaired stabilization of gaze mediated by the otoliths. These findings suggest that OCR and perceived vertical are relatively independent from the cerebellum unless there is a cerebellar imbalance like an acute unilateral cerebellar stroke. The increased trial-to-trial SVV variability may be a general feature of cerebellar disease since a function of the cerebellum may be to compensate for such. SVV variability might be useful to monitor disease progression and treatment response in patients.

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.

Cerebellar disorders--at the crossroad of molecular pathways and diagnosis

Our understanding of the pathogenesis of cerebellar ataxias has started several decades ago and is continuously growing. The numerous mechanisms of cerebellar dysfunction are being discovered by numerous groups of researchers worldwide. Neuronal damage results from a complex interaction of metabolic pathways, which leads to symptoms observed in cerebellar disorders. The main mechanisms at the molecular level are the following: impairment of DNA repair and replication, deregulation of transcription/deficits of processing/transport of RNA, abnormal protein transport and misfolding, aggregates both at the nuclear and cytosolic level, activation of caspases, apoptosis, involvement of autophagic mechanisms, oxidative stress and mitochondrial dysfunction, excitotoxicity, abnormal lipid metabolism, impaired axonal transport and vesicle trafficking, and defects of the neurotransmission. The convergence of the current clinical classification with molecular findings is expected. This integration is a basic substrate for the rationale development of therapies.

The spinocerebellar ataxias

Slowly progressive ataxia accompanied by cerebellar degeneration is often genetic in origin. The past 15 years have witnessed a revolution in our understanding of the causes of dominantly inherited ataxias, now known as the spinocerebellar ataxias (SCAs). Nearly 30 distinct genetic causes of SCA are known, numbered chronologically in order of discovery. All SCAs display classic cerebellar signs, and many display disabling noncerebellar features, most commonly brainstem dysfunction. Eye movement abnormalities are common, reflecting cerebellar and brainstem degeneration. Visual loss from retinal degeneration is rare in SCA, occurring most commonly and profoundly in SCA7. Although the SCAs are relentlessly progressive and currently untreatable, recent scientific advances have begun to shed light on various disease mechanisms that may lead to preventive therapies.

Animal models of human cerebellar ataxias: a cornerstone for the therapies of the twenty-first century

Cerebellar ataxias represent a group of disabling neurological disorders. Our understanding of the pathogenesis of cerebellar ataxias is continuously expanding. A considerable number of laboratory animals with neurological mutations have been reported and numerous relevant animal models mimicking the phenotype of cerebellar ataxias are becoming available. These models greatly help dissecting the numerous mechanisms of cerebellar dysfunction, a major step for the assessment of therapeutics targeting a given deleterious pathway and for the screening of old or newly synthesized chemical compounds. Nevertheless, differences between animal models and human disorders should not be overlooked and difficulties in terms of characterization should not be occulted. The identification of the mutations of many hereditary ataxias, the development of valuable animal models, and the recent identifications of the molecular mechanisms underlying cerebellar disorders represent a combination of key factors for the development of anti-ataxic innovative therapies. It is anticipated that the twenty-first century will be the century of effective therapies in the field of cerebellar ataxias. The animal models are a cornerstone to reach this goal.

Current advances in lesion-symptom mapping of the human cerebellum

While high-resolution structural magnetic resonance imaging (MRI) combined with newer analysis methods has become a powerful tool in human cerebral lesion studies, comparatively few studies have used these advanced imaging techniques to study lesions of the human cerebellum and their associated symptoms. This review will summarize the methodology of MRI-based lesion-symptom mapping of the human cerebellum and discuss its potential for gaining insights into cerebellar function. The investigation of patients with defined focal lesions yields the greatest potential for obtaining meaningful correlations between lesion site and behavioral deficits. In smaller groups of patients overlay plots and subtraction analysis are good options. If larger groups of patients are available, different statistical techniques have been introduced to compare behavior and lesion site on a voxel-by-voxel basis. Although localization in degenerative cerebellar disorders is less accurate because of the diffuse nature of the disease, certain information about the supposed function of larger subdivisions of the cerebellum can be gained. Examples are given which show that lesion-symptom mapping allows to investigate the function of the intermediate zone and cerebellar nuclei. We conclude that meaningful correlations between lesion site and behavioral data can be obtained in patients with degenerative as well as focal cerebellar disorders.