Spinocerebellar ataxia type 12 identified in two Italian families may mimic sporadic ataxia

Investigation of Spinocerebellar Ataxia (SCA) Disease in Iranian Patients and Accurate Trinucleotide Repeat Detection in the SCA3 by TP-PCR Method

SCA (spinocerebellar ataxia) which is autosomal dominantly transferred is a subset of inherited cerebellar ataxia. These progressive neurological diseases have clinical features of ataxia and are derived from the destruction of the cerebellum. These diseases can also affect other areas, including the brainstem. Frequent proliferation of CAG nucleotides can encode polyglutamine and, as a result, produce the toxic polyglutamine (poly Q) protein that leads to many types of SCAs. They are categorized based on specific genetic mutations. The main symptoms of SCA, gait ataxia and incoordination, nystagmus, vision problems, and dysarthria, can be mentioned. In this study, 31 Iranians who were suspected of SCA disease were clinically diagnosed from November 2019 to September 2021. For these 31 patients suspected of spinocerebellar ataxia, PCR was performed, and the analysis was based on vertical electrophoresis. For SCA3 patients, the TP-PCR technique was carried out and evaluated by capillary electrophoresis. For all 31 patients, PCR function was successful according to the results attained by conventional PCR. The number of three nucleotide replications was within the normal range for 22 people, and nine patients were reported. Studies showed that three people suspected of SCA were infected with SCA3 according to the TP-PCR technique, and this was while seven people were diagnosed with SCA3 using the PCR method. As the purpose of this test is to provide a more accurate diagnostic method and prenatal diagnosis of this disease, the TP-PCR method proved to be more suitable when applied for the diagnosis of abnormal trinucleotides CAG in spinocerebellar ataxia type 3.

Tremor in Spinocerebellar Ataxia: A Scoping Review

Background

Spinocerebellar ataxia (SCA) denotes an expanding list of autosomal dominant cerebellar ataxias. Although tremor is an important aspect of the clinical spectrum of the SCAs, its prevalence, phenomenology, and pathophysiology are unknown.

Objectives

This review aims to describe the various types of tremors seen in the different SCAs, with a discussion on the pathophysiology of the tremors, and the possible treatment modalities.

Methods

The authors conducted a literature search on PubMed using search terms including tremor and the various SCAs. Relevant articles were included in the review after excluding duplicate publications.

Results

While action (postural and intention) tremors are most frequently associated with SCA, rest and other rare tremors have also been documented. The prevalence and types of tremors vary among the different SCAs. SCA12, common in certain ethnic populations, presents a unique situation, where the tremor is typically the principal manifestation. Clinical manifestations of SCAs may be confused with essential tremor or Parkinson's disease. The pathophysiology of tremors in SCAs predominantly involves the cerebellum and its networks, especially the cerebello-thalamo-cortical circuit. Additionally, connections with the basal ganglia, and striatal dopaminergic dysfunction may have a role. Medical management of tremor is usually guided by the phenomenology and associated clinical features. Deep brain stimulation surgery may be helpful in treatment-resistant tremors.

Conclusions

Tremor is an elemental component of SCAs, with diverse phenomenology, and emphasizes the role of the cerebellum in tremor. Further studies will be useful to delineate the clinical, pathophysiological, and therapeutic aspects of tremor in SCAs.

Essential Tremor Within the Broader Context of Other Forms of Cerebellar Degeneration

Essential tremor (ET) has recently been reconceptualized by many as a degenerative disease of the cerebellum. Until now, though, there has been no attempt to frame it within the context of these diseases. Here, we compare the clinical and postmortem features of ET with other cerebellar degenerations, thereby placing it within the broader context of these diseases. Action tremor is the hallmark feature of ET. Although often underreported in the spinocerebellar ataxias (SCAs), action tremors occur, and it is noteworthy that in SCA12 and 15, they are highly prevalent, often severe, and can be the earliest disease manifestation, resulting in an initial diagnosis of ET in many cases. Intention tremor, sometimes referred to as "cerebellar tremor," is a common feature of ET and many SCAs. Other features of cerebellar dysfunction, gait ataxia and eye motion abnormalities, are seen to a mild degree in ET and more markedly in SCAs. Several SCAs (e.g., SCA5, 6, 14, and 15), like ET, follow a milder and more protracted disease course. In ET, numerous postmortem changes have been localized to the cerebellum and are largely confined to the cerebellar cortex, preserving the cerebellar nuclei. Purkinje cell loss is modest. Similarly, in SCA3, 12, and 15, Purkinje cell loss is limited, and in SCA12 and 15, there is preservation of cerebellar nuclei and relative sparing of other central nervous system regions. Both clinically and pathologically, there are numerous similarities and intersection points between ET and other disorders of cerebellar degeneration.

Spasmodic dysphonia as a presenting symptom of spinocerebellar ataxia type 12

Autosomal dominant spinocerebellar ataxia (SCA) type 12 is a rare SCA characterized by a heterogeneous phenotype. Action tremor of the upper limbs is the most common presenting sign and cerebellar signs can appear subsequently. In many cases, minor signs, like dystonia, can be predominant even at onset. Laryngeal dystonia (spasmodic dysphonia) has been observed only in one case of SCA12 and never reported at disease onset. We present a 61-year-old female who developed spasmodic dysphonia followed by dystonic tremor and subsequent ataxia diagnosed with SCA12. Thus, spasmodic dysphonia can be a presenting symptom of SCA12.

Clinical Characterization of Genetically Diagnosed Cases of Spinocerebellar Ataxia Type 12 from India

https://onlinelibrary.wiley.com/page/journal/23301619/homepage/mdc312551-sup-v001_1.htm.

BACKGROUND

Spinocerebellar ataxia type 12 (SCA12) is a rare form of an autosomal-dominant ataxic disorder associated with an expansion of CAG repeat length. Here, we present a large case series of patients with SCA12 and describe a wide range of typical and rare symptoms.

METHODS

Twenty-one consecutive patients with genetically proven SCA12 underwent detailed neurological examination. We assessed clinical characteristics using validated rating scales for evaluating motor features in SCA. Nonmotor symptoms and quality of life were assessed using appropriate, validated scales. Correlations of CAG repeat length with both severity score and age of onset were explored.

RESULTS

The mean age of onset was 51 years, and most patients were descendants of a single, endogamous Indian community (Agarwal). Tremor was the most common initial presenting symptom (90%). Hand dystonia was present in 14 of 21 patients, and most patients in the cohort presented with gait disturbance. Neuropsychiatric manifestations were common coexisting features. The CAG repeat length was significantly correlated (r = -0.760; P = 0.0001) with early age of onset, but not with disease severity. Tremor affected the quality of life in 18 of 21 patients, because they had difficulty in handling liquids.

CONCLUSIONS

Tremor was the most common, nonataxic symptom at initial presentation in patients with SCA12. Proximal upper limb tremor, typically with high amplitude and low frequency, can raise a strong diagnostic suspicion. Associated hand dystonia was a common coexisting motor feature. Various nonmotor features were also observed in several cases which require therapeutic attention.

Repeat expansion diseases

More than 40 diseases, most of which primarily affect the nervous system, are caused by expansions of simple sequence repeats dispersed throughout the human genome. Expanded trinucleotide repeat diseases were discovered first and remain the most frequent. More recently tetra-, penta-, hexa-, and even dodeca-nucleotide repeat expansions have been identified as the cause of human disease, including some of the most common genetic disorders seen by neurologists. Repeat expansion diseases include both causes of myotonic dystrophy (DM1 and DM2), the most common genetic cause of amyotrophic lateral sclerosis/frontotemporal dementia (C9ORF72), Huntington disease, and eight other polyglutamine disorders, including the most common forms of dominantly inherited ataxia, the most common recessive ataxia (Friedreich ataxia), and the most common heritable mental retardation (fragile X syndrome). Here I review distinctive features of this group of diseases that stem from the unusual, dynamic nature of the underlying mutations. These features include marked clinical heterogeneity and the phenomenon of clinical anticipation. I then discuss the diverse molecular mechanisms driving disease pathogenesis, which vary depending on the repeat sequence, size, and location within the disease gene, and whether the repeat is translated into protein. I conclude with a brief clinical and genetic description of individual repeat expansion diseases that are most relevant to neurologists.

Design, synthesis, immunocytochemistry evaluation, and molecular docking investigation of several 4-aminopyridine derivatives as potential neuroprotective agents for treating Parkinson's disease

Neuroprotection refers to the relative preservation of neuronal structure and function. Neuroprotective agents refer to substances that are capable of preserving brain function and structure. Currently, there are no neuroprotective agents available that can effectively relieve the progression of Parkinson's disease. In this work, five novel 4-aminopyridine derivatives, including three amides and two ureas, were designed, synthesized, and evaluated using the rat PC12 mice pheochromocytoma cell line as an in vitro model. As well as human Rho kinase inhibitory experiment was performed. Among them, compound 3, which exhibited high cell viability, low cytotoxicity and good efficacy of inhibition on α-synuclein, oxidation, inflammation and Rho kinase, was profound as potential agents for Parkinson's disease (PD).

Neuropathology and Cellular Pathogenesis of Spinocerebellar Ataxia Type 12

OBJECTIVE

SCA12 is a progressive autosomal-dominant disorder, caused by a CAG/CTG repeat expansion in PPP2R2B on chromosome 5q32, and characterized by tremor, gait ataxia, hyperreflexia, dysmetria, abnormal eye movements, anxiety, depression, and sometimes cognitive impairment. Neuroimaging has demonstrated cerebellar and cortical atrophy. We now present the neuropathology of the first autopsied SCA12 brain and utilize cell models to characterize potential mechanisms of SCA12 neurodegeneration.

METHODS

A fixed SCA12 brain was examined using gross, microscopic, and immunohistochemical methods. The effect of the repeat expansion on PPP2R2B Bβ1 expression was examined in multiple cell types by transient transfection of constructs containing the PPP2R2B Bβ1 promoter region attached to a luciferase reporter. The neurotoxic effect of PPP2R2B overexpression was examined in transfected rat primary neurons.

RESULTS

Neuropathological investigation revealed enlarged ventricles, marked cerebral cortical atrophy and Purkinje cell loss, less-prominent cerebellar and pontine atrophy, and neuronal intranuclear ubiquitin-positive inclusions, consistent with Marinesco bodies, which did not stain for long polyglutamine tracts, alpha-synuclein, tau, or transactive response DNA-binding protein 43. Reporter assays demonstrated that the region of PPP2R2B containing the repeat functions as a promoter, and that promoter activity increases with longer repeat length and is dependent on cell type, repeat sequence, and sequence flanking the repeat. Overexpression of PPP2R2B in primary cortical neurons disrupted normal morphology.

CONCLUSIONS

SCA12 involves extensive, but selective, neurodegeneration distinct from Alzheimer's disease, synucleinopathies, tauopathies, and glutamine expansion diseases. SCA12 neuropathology may arise from the neurotoxic effect of repeat-expansion-induced overexpression of PPP2R2B.

Magnetic resonance imaging biomarkers in patients with progressive ataxia: current status and future direction

A diagnostic challenge commonly encountered in neurology is that of an adult patient presenting with ataxia. The differential is vast and clinical assessment alone may not be sufficient due to considerable overlap between different causes of ataxia. Magnetic resonance (MR)-based biomarkers such as voxel-based morphometry, MR spectroscopy, diffusion-weighted and diffusion-tensor imaging and functional MR imaging are gaining great attention for their potential as indicators of disease. A number of studies have reported correlation with clinical severity and underlying pathophysiology, and in some cases, MR imaging has been shown to allow differentiation of conditions causing ataxia. However, despite recent advances, their sensitivity and specificity vary. In addition, questions remain over their validity and reproducibility, especially when applied in routine clinical practice. This article extensively reviews the current literature regarding MR-based biomarkers for the patient with predominantly adult-onset ataxia. Imaging features characteristic of a particular ataxia are provided and features differentiating ataxia groups and subgroups are discussed. Finally, discussion will turn to the feasibility of applying these biomarkers in routine clinical practice.

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.

Recent advances in the genetics of cerebellar ataxias

The hereditary cerebellar ataxias are a clinically and genetically heterogeneous group of disorders that primarily affect the cerebellum; often there are additional features such as neuropathy, cognitive decline, or maculopathy that help define the clinical subtype of ataxia. They are commonly classified according to their mode of inheritance into autosomal dominant, autosomal recessive, X-linked, and mitochondrial forms. Great advances have been made in understanding the genetics of cerebellar ataxias in the last 15 years. At least 36 different forms of ADCA are known, 20 autosomal-recessive, two X-linked, and several forms of ataxia associated with mitochondrial defects are known to date. However, in about 40 % of suspected genetically determined ataxia cases, the underlying genetic defect remains undetermined. Although the majority of disease genes have been found in the last two decades, over the last 2 years the genetics has undergone a methodological revolution. New DNA sequencing technologies are enabling us to investigate the whole or large targeted proportions of the genome in a rapid, affordable, and comprehensive way. Exome and targeted sequencing has recently identified four new genes causing ataxia: TGM6, ANO10, SYT14, and rundataxin. This approach is likely to continue to discover new ataxia genes and make screening of existing genes more effective. Translating the genetic findings into isolated and overlapping disease pathways will help stratify patient groups and identify therapeutic targets for ataxia that have so far remained undiscovered.

The spinocerebellar ataxias: clinical aspects and molecular genetics

Spinocerebellar ataxias (SCAs) are a highly heterogeneous group of inherited neurological disorders, based on clinical characterization alone with variable degrees of cerebellar ataxia often accompanied by additional cerebellar and noncerebellar symptoms which in most cases defy differentiation. Molecular causative deficits in at least 31 genes underlie the clinical symptoms in the SCAs by triggering cerebellar and, very frequently, brain stem dysfunction. The identification of the causative molecular deficits enables the molecular diagnosis of the different SCA subtypes and facilitates genetic counselling. Recent scientific advances are shedding light into developing therapeutic strategies. The scope of this chapter is to provide updated details of the spinocerebellar ataxias with particular emphasis on those aspects aimed at facilitating the clinical and genetic diagnoses.

Spinocerebellar ataxia type 31 exists in northeast China

Spinocerebellar ataxia type 31 (SCA31), is a recently defined subtype of autosomal dominant cerebellar ataxia (ADCA) characterized by late-onset pure cerebellar ataxia. SCA31 is common in Japan but whether or not it exists in other countries is still unclear. In this study, the authors describe a sporadic Chinese patient with SCA31. Although the cardinal clinical features, i.e., late-onset cerebellar ataxia and hearing impairment in our sporadic patient were similar to those described previously in Japan, mild axonal sensorimotor neuropathy was identified in our SCA31 patient, which is somewhat distinct from most prior reports of the disease. This is the first report of SCA31 in China; thus, extending the ethnic association beyond families of Japanese origin. In addition, our study suggests that the clinical features of SCA31 might be broader than previously thought.

Autosomal dominant cerebellar ataxia type I: a review of the phenotypic and genotypic characteristics

Type I autosomal dominant cerebellar ataxia (ADCA) is a type of spinocerebellar ataxia (SCA) characterized by ataxia with other neurological signs, including oculomotor disturbances, cognitive deficits, pyramidal and extrapyramidal dysfunction, bulbar, spinal and peripheral nervous system involvement. The global prevalence of this disease is not known. The most common type I ADCA is SCA3 followed by SCA2, SCA1, and SCA8, in descending order. Founder effects no doubt contribute to the variable prevalence between populations. Onset is usually in adulthood but cases of presentation in childhood have been reported. Clinical features vary depending on the SCA subtype but by definition include ataxia associated with other neurological manifestations. The clinical spectrum ranges from pure cerebellar signs to constellations including spinal cord and peripheral nerve disease, cognitive impairment, cerebellar or supranuclear ophthalmologic signs, psychiatric problems, and seizures. Cerebellar ataxia can affect virtually any body part causing movement abnormalities. Gait, truncal, and limb ataxia are often the most obvious cerebellar findings though nystagmus, saccadic abnormalities, and dysarthria are usually associated. To date, 21 subtypes have been identified: SCA1-SCA4, SCA8, SCA10, SCA12-SCA14, SCA15/16, SCA17-SCA23, SCA25, SCA27, SCA28 and dentatorubral pallidoluysian atrophy (DRPLA). Type I ADCA can be further divided based on the proposed pathogenetic mechanism into 3 subclasses: subclass 1 includes type I ADCA caused by CAG repeat expansions such as SCA1-SCA3, SCA17, and DRPLA, subclass 2 includes trinucleotide repeat expansions that fall outside of the protein-coding regions of the disease gene including SCA8, SCA10 and SCA12. Subclass 3 contains disorders caused by specific gene deletions, missense mutation, and nonsense mutation and includes SCA13, SCA14, SCA15/16, SCA27 and SCA28. Diagnosis is based on clinical history, physical examination, genetic molecular testing, and exclusion of other diseases. Differential diagnosis is broad and includes secondary ataxias caused by drug or toxic effects, nutritional deficiencies, endocrinopathies, infections and post-infection states, structural abnormalities, paraneoplastic conditions and certain neurodegenerative disorders. Given the autosomal dominant pattern of inheritance, genetic counseling is essential and best performed in specialized genetic clinics. There are currently no known effective treatments to modify disease progression. Care is therefore supportive. Occupational and physical therapy for gait dysfunction and speech therapy for dysarthria is essential. Prognosis is variable depending on the type of ADCA and even among kindreds.