Ataxias in Brazil: 17 years of experience in an ataxia center.

BACKGROUND: Cerebellar ataxias comprise sporadic and genetic etiologies. Ataxia may also be a presenting feature in hereditary spastic paraplegias (HSPs). OBJECTIVE: To report a descriptive analysis of the frequency of different forms of cerebellar ataxia evaluated over 17 years in the Ataxia Unit of Universidade Federal de São Paulo, Brazil. METHODS: Charts of patients who were being followed from January 2007 to December 2023 were reviewed. We used descriptive statistics to present our results as frequencies and percentages of the overall analysis. Diagnosed patients were classified according to the following 9 groups: sporadic ataxia, spinocerebellar ataxias (SCAs), other autosomal dominant cerebellar ataxias, autosomal recessive cerebellar ataxias (ARCAs), mitochondrial ataxias, congenital ataxias, X-linked ataxias, HSPs, and others. RESULTS: There were 1,332 patients with ataxias or spastic paraplegias. Overall, 744 (55.85%) of all cases were successfully diagnosed: 101 sporadic ataxia, 326 SCAs, 20 of other autosomal dominant cerebellar ataxias, 186 ARCAs, 6 X-linked ataxias, 2 mitochondrial ataxias, 4 congenital ataxias, and 51 HSPs. CONCLUSION: This study describes the frequency of cerebellar ataxias in a large group of patients followed for the past 17 years, of whom 55% obtained a definitive clinical or molecular diagnosis. Future demographic surveys in Brazil or Latin American remain necessary.

ANTECEDENTES: Ataxias cerebelares compreendem as etiologias esporádicas e genéticas. Ataxia também pode ser uma característica das paraplegias espásticas hereditárias (HSPs). OBJETIVO: Relatar uma análise descritiva da frequência das diferentes formas de ataxias cerebelares avaliadas ao longo de 17 anos no Setor da Ataxias da Universidade Federal de São Paulo, Brasil. MéTODOS: Prontuários de pacientes acompanhados de janeiro de 2007 a dezembro de 2023 foram revisados. Usamos análise descritiva para apresentar nossos resultados como frequências e percentuais. Os pacientes foram classificados de acordo com os 9 grupos seguintes: ataxias esporádicas, ataxias espinocerebelares (SCA), outras ataxias cerebelares autossômicas dominantes, ataxias cerebelares autossômicas recessivas (ARCA), ataxias mitocondriais, ataxias congênitas, ataxias ligadas ao X, PEH e outros. RESULTADOS: Foram avaliados 1.332 pacientes. Desse total, 744 tiveram um diagnóstico definitivo: 101 ataxias esporádicas, 326 SCA, 20 outras ataxias cerebelares autossômicas dominantes, 186 (ARCA), 6 ataxias ligadas ao X, 2 ataxias mitocondriais, 4 ataxias congênitas e 51 HSP. CONCLUSãO: Esse estudo descreve a frequência e a etiologia das ataxias em um grande grupo de pacientes acompanhados nos últimos 17 anos, dos quais 55% obtiveram diagnóstico clínico ou molecular definitivos. Estudos demográficos futuros do Brasil ou da América Latina continuam sendo necessários.

Feasibility of a randomized, sham-controlled pilot study for accelerated rTMS-treatment of the cerebellum plus physiotherapy in CANVAS patients.

BACKGROUND: Cerebellar ataxia, neuropathy and bilateral vestibular areflexia (CANVAS) is a rare neurodegenerative disease affecting the cerebellum, the peripheral nervous system and the vestibular system. Due to the lack of approved drugs, therapy comprises physiotherapy and speech therapy. Transcranial magnetic stimulation is a promising non-invasive therapeutic option to complement classical symptomatic therapies. OBJECTIVE: To test feasibility of the combination of transcranial magnetic stimulation using an accelerated protocol and standard symptomatic therapy in patients with CANVAS. METHODS: Eight patients with genetically confirmed CANVAS were assigned to either verum or sham cerebellar transcranial magnetic stimulation using an accelerated protocol. Treatment duration was limited to 5 days. Additionally, patients in both groups received symptomatic therapy (speech and physiotherapy) for the duration of the study. RESULTS: All patients completed the stimulation protocol. Adverse events were rare. Ataxia severity improved in the verum group only. CONCLUSION: The combination of transcranial magnetic stimulation and classic symptomatic therapy is feasible in a neuro-rehabilitation setting and potentially ameliorates ataxia severity.

Compound Heterozygous Mutations of SACS in a Korean Cohort Study of Charcot-Marie-Tooth Disease Concurrent Cerebellar Ataxia and Spasticity.

Mutations in the SACS gene are associated with autosomal recessive spastic ataxia of Charlevoix-Saguenay disease (ARSACS) or complex clinical phenotypes of Charcot-Marie-Tooth disease (CMT). This study aimed to identify SACS mutations in a Korean CMT cohort with cerebellar ataxia and spasticity by whole exome sequencing (WES). As a result, eight pathogenic SACS mutations in four families were identified as the underlying causes of these complex phenotypes. The prevalence of CMT families with SACS mutations was determined to be 0.3%. All the patients showed sensory, motor, and gait disturbances with increased deep tendon reflexes. Lower limb magnetic resonance imaging (MRI) was performed in four patients and all had fatty replacements. Of note, they all had similar fatty infiltrations between the proximal and distal lower limb muscles, different from the neuromuscular imaging feature in most CMT patients without SACS mutations who had distal dominant fatty involvement. Therefore, these findings were considered a characteristic feature in CMT patients with SACS mutations. Although further studies with more cases are needed, our results highlight lower extremity MRI findings in CMT patients with SACS mutations and broaden the clinical spectrum. We suggest screening for SACS in recessive CMT patients with complex phenotypes of ataxia and spasticity.

Optimizing Rare Disease Gait Classification through Data Balancing and Generative AI: Insights from Hereditary Cerebellar Ataxia.

The interpretability of gait analysis studies in people with rare diseases, such as those with primary hereditary cerebellar ataxia (pwCA), is frequently limited by the small sample sizes and unbalanced datasets. The purpose of this study was to assess the effectiveness of data balancing and generative artificial intelligence (AI) algorithms in generating synthetic data reflecting the actual gait abnormalities of pwCA. Gait data of 30 pwCA (age: 51.6 ± 12.2 years; 13 females, 17 males) and 100 healthy subjects (age: 57.1 ± 10.4; 60 females, 40 males) were collected at the lumbar level with an inertial measurement unit. Subsampling, oversampling, synthetic minority oversampling, generative adversarial networks, and conditional tabular generative adversarial networks (ctGAN) were applied to generate datasets to be input to a random forest classifier. Consistency and explainability metrics were also calculated to assess the coherence of the generated dataset with known gait abnormalities of pwCA. ctGAN significantly improved the classification performance compared with the original dataset and traditional data augmentation methods. ctGAN are effective methods for balancing tabular datasets from populations with rare diseases, owing to their ability to improve diagnostic models with consistent explainability.

Coexistence of Retinitis Pigmentosa and Ataxia in Patients with PHARC, PCARP, and Oliver-McFarlane Syndromes.

Retinitis pigmentosa (RP) is an inherited retinal dystrophy caused by the loss of photoreceptors and retinal pigment epithelial atrophy, leading to severe visual impairment or blindness. RP can be classified as nonsyndromic or syndromic with complex clinical phenotypes. Three unrelated Polish probands affected with retinitis pigmentosa coexisting with cerebellar ataxia were recruited for this study. Clinical heterogeneity and delayed appearance of typical disease symptoms significantly prolonged the patients' diagnostic process. Therefore, many clinical and genetic tests have been performed in the past. Here, we provide detailed clinical and genetic analysis results of the patients. Whole-exome sequencing (WES) and targeted NGS analysis allow the identification of four novel and two previously reported variants in the following genes: ABHD12, FLVCR1, and PNPLA6. The use of next-generation sequencing (NGS) methods finally allowed for confirmation of the clinical diagnosis. Ultra-rare diseases such as PHARC, PCARP, and Oliver-McFarlane syndromes were diagnosed in patients, respectively. Our findings confirmed the importance of the application of next-generation sequencing methods, especially in ultra-rare genetic disorders with overlapping features.

3-Acetylpyridine-induced ataxic-like motor impairments are associated with plastic changes in the Purkinje cells of the rat cerebellum.

Ataxias are characterized by aberrant movement patterns closely related to cerebellar dysfunction. Purkinje cell axons are the sole outputs from the cerebellar cortex, and dysfunctional activity of Purkinje cells has been associated with ataxic movements. However, the synaptic characteristics of Purkinje cells in cases of ataxia are not yet well understood. The nicotinamide antagonist 3-acethylpyridine (3-AP) selectively destroys inferior olivary nucleus neurons so it is widely used to induce cerebellar ataxia. Five days after 3-AP treatment (65mg/kg) in adult male Sprague-Dawley rats, motor incoordination was revealed through BBB and Rotarod testing. In addition, in Purkinje cells from lobules V-VII of the cerebellar vermis studied by the Golgi method, the density of dendritic spines decreased, especially the thin and mushroom types. Western blot analysis showed a decrease in AMPA and PSD-95 content with an increase of the α-catenin protein, while GAD-67 and synaptophysin were unchanged. Findings suggest a limited capacity of Purkinje cells to acquire and consolidate afferent excitatory inputs and an aberrant, rigid profile in the movement-related output patterns of Purkinje neurons that likely contributes to the motor-related impairments characteristic of cerebellar ataxias.

[Subacute ataxia associated with cerebellar ataxia, neuropathy and vestibular areflexia (CANVAS)]. / Ataxia subaguda asociada a ataxia cerebelosa, neuropatía y arreflexia vestibular (CANVAS).

Cerebellar ataxia, neuropathy, and vestibular areflexia syndrome (CANVAS) is a late onset neurodegenerative disorder. Its genetic basis has recently been identified in the gene encoding a subunit of the Replication Factor C (RFC1). We present the case of a 62-year-old woman who experienced a history of a biphasic presentation of imbalance and gait disorders, with rapid onset of symptoms followed by slow and progressive neurological deterioration. The diagnostic process was challenging, and numerous tests were conducted to rule out acquired and genetic causes of ataxia, leading to a diagnosis of late-onset idiopathic cerebellar ataxia. Subsequently, vestibular function tests identified severe bilateral vestibulopathy. This led to considering CANVAS among the diagnoses, which was ultimately confirmed through genetic testing (biallelic expansion of the pentanucleotide AAGGG in the RFC1 gene). This case highlights the importance of this new described genetic disease and its subacute presentation variant, emphasizing the relevance of objective vestibular function tests in idiopathic ataxias to achieve proper diagnosis and eventual genetic counseling for offspring.

El síndrome de ataxia cerebelosa, neuropatía y arreflexia vestibular (CANVAS) es un trastorno neurodegenerativo progresivo que se manifiesta en etapas tardías de la vida. Su base genética ha sido recientemente identificada en el gen que codifica la subunidad 1 del factor C de replicación (RFC1). Presentamos el caso de una mujer de 62 años con una historial de desequilibrio y deterioro de la marcha de presentación bifásica, con un inicio rápido de los síntomas seguido de un deterioro neurológico lento y progresivo. El proceso diagnóstico fue complejo y se realizaron numerosas pruebas para descartar causas adquiridas y genéticas de la ataxia, arribando al diagnóstico de ataxia cerebelosa de inicio tardío idiopática. Ulteriormente, las pruebas de función vestibular identificaron una grave vestibulopatía bilateral. Esto llevó a considerar el CANVAS entre los diagnósticos, que finalmente fue confirmado mediante pruebas genéticas (expansión bialélica del penta-nucleótido AAGGG en el gen RFC1). Este caso subraya la importancia de esta nueva enfermedad genética y su variante de presentación subaguda y enfatiza la relevancia de las pruebas objetivas de función vestibular en las ataxias consideradas idiopáticas para lograr un diagnóstico adecuado y un eventual asesoramiento genético a la descendencia.

Discovery of a de novo ITPR1 missense mutation in a patient with early-onset cerebellar ataxia: A rare case report of spinocerebellar ataxia 29.

BACKGROUND: Spinocerebellar ataxia 29 (SCA29) is a rare genetic disorder characterized by early-onset ataxia, gross motor delay, and infantile hypotonia, and is primarily associated with variants in the ITPR1 gene. Cases of SCA29 in Asia are rarely reported, limiting our understanding of this disease. METHODS: A female Korean infant, demonstrating clinical features of SCA29, underwent evaluation and rehabilitation at our outpatient clinic from the age of 3 months to the current age of 4 years. Trio-based genome sequencing tests were performed on the patient and her biological parents. RESULTS: The infant initially presented with macrocephaly, hypotonia, and nystagmus, with nonspecific findings on initial neuroimaging. Subsequent follow-up revealed gross motor delay, early onset ataxia, strabismus, and cognitive impairment. Further neuroimaging revealed atrophy of the cerebellum and vermis, and genetic analysis revealed a de novo pathogenic heterozygous c.800C>T, p.Thr267Met missense mutation in the ITPR1 gene (NM_001378452.1). CONCLUSION: This is the first reported case of SCA29 in a Korean patient, expanding the genetic and phenotypic spectrum of ITPR1-related ataxias. Our case highlights the importance of recognizing early-onset ataxic symptoms, central hypotonia, and gross motor delays with poor ocular fixation, cognitive deficits, and isolated cerebellar atrophy as crucial clinical indicators of SCA29.

[A case of autoimmune glial fibrillary acidic protein astrocytopathy with various symptoms such as optic disc edema and cerebellar ataxia].

A 59-year-old man had developed visual abnormality, nausea, headache, and weight loss since three months before. The ophthalmologist found severe optic disc edema in both eyes, and referred him to our hospital. The patient had mild cerebellar ataxia. Increased cerebrospinal fluid pressure, increased protein and cell counts, positive oligoclonal band, and contrast-enhanced head MRI showed multiple linear perivascular radial gadolinium enhancement around bilateral lateral ventricles. His subjective and objective findings significantly improved with steroid treatment. The cerebrospinal fluid was found to be positive for glial fibrillary acidic protein (GFAP) antibodies, and a diagnosis of GFAP astrocytopathy was obtained. When optic edema or radial contrast effects was observed on contrast-enhanced MRI, GFAP astrocytopathy should be considerd. Prompt immunotherapy is required to circumvent the development of permanent visual impairment.

Neuroglobin overexpression in cerebellar neurons of Harlequin mice improves mitochondrial homeostasis and reduces ataxic behavior.

Neuroglobin, a member of the globin superfamily, is abundant in the brain, retina, and cerebellum of mammals and localizes to mitochondria. The protein exhibits neuroprotective capacities by participating in electron transfer, oxygen supply, and protecting against oxidative stress. Our objective was to determine whether neuroglobin overexpression can be used to treat neurological disorders. We chose Harlequin mice, which harbor a retroviral insertion in the first intron of the apoptosis-inducing factor gene resulting in the depletion of the corresponding protein essential for mitochondrial biogenesis. Consequently, Harlequin mice display degeneration of the cerebellum and suffer from progressive blindness and ataxia. Cerebellar ataxia begins in Harlequin mice at the age of 4 months and is characterized by neuronal cell disappearance, bioenergetics failure, and motor and cognitive impairments, which aggravated with aging. Mice aged 2 months received adeno-associated viral vectors harboring the coding sequence of neuroglobin or apoptosis-inducing factor in both cerebellar hemispheres. Six months later, Harlequin mice exhibited substantial improvements in motor and cognitive skills; probably linked to the preservation of respiratory chain function, Purkinje cell numbers and connectivity. Thus, without sharing functional properties with apoptosis-inducing factor, neuroglobin was efficient in reducing ataxia in Harlequin mice.

Reduced sensitivity to future consequences underlies gambling decision in cerebellar ataxia.

INTRODUCTION: Previous research has identified that people with cerebellar ataxia (CA) showed impaired reward-related decision-making in the Iowa Gambling Task (IGT). To investigate the mechanisms underlying this impairment, we examined CA participants' combination of performance in the IGT, which predominantly tests reward seeking, and the modified IGT (mIGT), which mainly assesses punishment avoidance. METHODS: Fifty participants with CA and one hundred controls completed the IGT and mIGT. Task performance in each of the five twenty-trial blocks was compared between groups and the learning rates were assessed with simple linear regressions. Each participant's IGT score and mIGT score were compared. RESULTS: CA participants performed worse than controls in both the IGT and the mIGT, especially in the last block (IGT: -0.24 ± 10.05 vs. 3.88 ± 10.31, p = 0.041; mIGT: 2.72 ± 7.62 vs. 8.65 ± 8.64, p < 0.001). In contrast to the controls, those with CA did not significantly improve their scores over time in either task. Controls performed better in the mIGT than the IGT, while CA participants' scores in the two tasks showed no significant difference. IGT and mIGT performance did not correlate with ataxia severity or depressive symptoms. CONCLUSION: Individuals with CA showed impaired performance in both the IGT and mIGT, which indicates disruption in both short-term reward seeking and short-term punishment avoidance. Therefore, these results suggest that reduced sensitivity to long-term consequences drives the risky decision-making in CA.

Case report: Isolated brainstem-cerebellar symptoms in a patient with anti-NMDA receptor encephalitis.

Cerebellar ataxia is an uncommon and atypical manifestation of anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis, often accompanied by seizures, psychiatric symptoms, and cognitive deficits. Previous cases of isolated brainstem-cerebellar symptoms in patients with anti-NMDAR encephalitis have not been documented. This report presents a case of anti-NMDAR encephalitis in which the patient exhibited cerebellar ataxia, nystagmus, diplopia, positive bilateral pathological signs, and hemiparesthesia with no other accompanying symptoms or signs. The presence of positive CSF anti-NMDAR antibodies further supports the diagnosis. Other autoantibodies were excluded through the use of cell-based assays. Immunotherapy was subsequently administered, leading to a gradual recovery of the patient.

Clinical and Molecular Spectrum of Autosomal Recessive CA8-Related Cerebellar Ataxia.

BACKGROUND: Based on a limited number of reported families, biallelic CA8 variants have currently been associated with a recessive neurological disorder named, cerebellar ataxia, mental retardation, and dysequilibrium syndrome 3 (CAMRQ-3). OBJECTIVES: We aim to comprehensively investigate CA8-related disorders (CA8-RD) by reviewing existing literature and exploring neurological, neuroradiological, and molecular observations in a cohort of newly identified patients. METHODS: We analyzed the phenotype of 27 affected individuals from 14 families with biallelic CA8 variants (including data from 15 newly identified patients from eight families), ages 4 to 35 years. Clinical, genetic, and radiological assessments were performed, and zebrafish models with ca8 knockout were used for functional analysis. RESULTS: Patients exhibited varying degrees of neurodevelopmental disorders (NDD), along with predominantly progressive cerebellar ataxia and pyramidal signs and variable bradykinesia, dystonia, and sensory impairment. Quadrupedal gait was present in only 10 of 27 patients. Progressive selective cerebellar atrophy, predominantly affecting the superior vermis, was a key diagnostic finding in all patients. Seven novel homozygous CA8 variants were identified. Zebrafish models demonstrated impaired early neurodevelopment and motor behavior on ca8 knockout. CONCLUSION: Our comprehensive analysis of phenotypic features indicates that CA8-RD exhibits a wide range of clinical manifestations, setting it apart from other subtypes within the category of CAMRQ. CA8-RD is characterized by cerebellar atrophy and should be recognized as part of the autosomal-recessive cerebellar ataxias associated with NDD. Notably, the presence of progressive superior vermis atrophy serves as a valuable diagnostic indicator. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

A 52-Year-Old Woman With Dysarthria, Ataxia, Xanthelasmas, and Miliary Pulmonary Nodules.

CASE PRESENTATION: A 52-year-old woman with no significant medical history was referred to our hospital for expedited workup of progressive dysarthria and ataxia over the past year. Prior CT angiography of the head and neck showed no relevant neurologic findings but did reveal miliary lesions in the lung apices, which was later confirmed via dedicated CT chest scan (Fig 1). Review of systems was negative for any respiratory, constitutional, or rheumatologic symptoms, except for new xanthelasma-like lesions over her forehead. She previously had smoked with 20 pack-years and had no TB risk factors. MRI of the face showed a 21-mm mass within the left external temporal fascia. MRI of the head showed diffuse leptomeningeal enhancement, right frontal lobe enhancement, and cerebellar and brainstem T2/fluid-attenuated inversion recovery hyperintensity, which prompted her admission to hospital.

Immune Ataxias: The Continuum of Latent Ataxia, Primary Ataxia and Clinical Ataxia.

The clinical category of immune-mediated cerebellar ataxias (IMCAs) is now recognized after 3 decades of clinical and experimental research. The cerebellum gathers about 60% of neurons in the brain, is enriched in numerous plasticity mechanisms, and presents a large variety of antigens at the neuroglial level: ion channels and related proteins, synaptic adhesion/organizing proteins, transmitter receptors, and glial cells. Cerebellar circuitry is especially vulnerable to immune attacks. After the loss of immune tolerance, IMCAs present in an acute or subacute manner with various combinations of a vestibulocerebellar syndrome (VCS), a cerebellar motor syndrome (CMS), and a cerebellar cognitive affective syndrome/Schmahmann's syndrome (CCAS/SS). IMCAs include gluten ataxia (GA), post-infectious cerebellitis (PIC), Miller Fisher syndrome (MFS), paraneoplastic cerebellar degeneration (PCD), opsoclonus myoclonus syndrome (OMS), anti-glutamic acid decarboxylase (anti-GAD) ataxia, and glial fibrillary acidic protein (GFAP) astrocytopathy (GFAP-A). In addition, multiple sclerosis (MS), acute disseminated encephalomyelitis (ADEM), Behçet disease, and collagen-vascular disorders may also present with cerebellar symptoms when lesions involve cerebellar afferences/efferences. Patients whose clinical profiles do not fit with IMCAs are now gathered in the group of primary autoimmune cerebellar ataxias (PACAs). Latent auto-immune cerebellar ataxia (LACA) refers to a clinical stage with a slow progressive course and a lack of obvious auto-immune background. At a pre-symptomatic stage, patients remain asymptomatic, whereas at the prodromal stage aspecific symptoms occur, announcing the symptomatic neuronal loss. LACA corresponds to a time-window where an intervention could lead to preservation of plasticity mechanisms. Patients may evolve from LACA to PACA and typical IMCAs, highlighting a continuum. Immune ataxias represent a model to elucidate the sequence of events leading to destruction of cerebellar neuronal reserve and develop novel strategies aiming to restore plasticity mechanisms.

Bilateral vestibulopathy as the initial presentation of CANVAS.

Cerebellar ataxia with neuropathy and vestibular areflexia syndrome (CANVAS) is a slowly progressing autosomal recessive ataxic disorder linked to an abnormal biallelic intronic (most commonly) AAGGG repeat expansion in the replication factor complex subunit 1 (RFC1). While the clinical diagnosis is relatively straightforward when the three components of the disorder are present, it becomes challenging when only one of the triad (cerebellar ataxia, neuropathy or vestibular areflexia) manifests. Isolated cases of Bilateral Vestibulopathy (BVP) or vestibular areflexia that later developed the other components of CANVAS have not been documented. We report four cases of patients with chronic imbalance and BVP that, after several years, developed cerebellar and neuropathic deficits with positive genetic testing for RFC1. Our report supports the concept that CANVAS should be considered in every patient with BVP of unknown etiology, even without the presence of the other triad components. This is especially important given that about 50% of cases in many BVP series are diagnosed as idiopathic, some of which may be undiagnosed CANVAS.

Spinocerebellar ataxia 27B (SCA27B), a frequent late-onset cerebellar ataxia.

Genetic cerebellar ataxias are still a diagnostic challenge, and yet not all of them have been identified. Very recently, in early 2023, a new cause of late-onset cerebellar ataxia (LOCA) was identified, spinocerebellar ataxia 27B (SCA27B). This is an autosomal dominant ataxia due to a GAA expansion in intron 1 of the FGF14 gene. Thanks to the many studies carried out since its discovery, it is now possible to define the clinical phenotype, its particularities, and the progression of SCA27B. It has also been established that it is one of the most frequent causes of LOCA. The core phenotype of the disease consists of slowly progressive late-onset ataxia with cerebellar syndrome, oculomotor disorders including downbeat nystagmus, and episodic symptoms such as diplopia. Therapeutic approaches have been proposed, including acetazolamide, and 4-aminopyridine, the latter with a better benefit/tolerance profile.