Genetic background of apparently idiopathic sporadic cerebellar ataxia

Identification of m.3243A>G mitochondrial DNA mutation in patients with cerebellar ataxia

BACKGROUND

The mitochondrial DNA m.3243A>G mutation can affect mitochondrial function and lead to a wide phenotypic spectrum, including mitochondrial encephalopathy with lactic acidosis and stroke-like episodes (MELAS) syndrome, diabetes mellitus, hearing impairment, cardiac involvement, epilepsy, migraine, myopathy, and cerebellar ataxia. However, m.3243A>G has been rarely reported in patients with cerebellar ataxia as their predominant manifestation. The aim of this study is to investigate the prevalence and clinical features of m.3243A>G in a Taiwanese cohort of cerebellar ataxia with unknown genetic diagnosis.

METHODS

This retrospective cohort study conducted the mutation analysis of m.3243A>G by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) in 232 unrelated Han Chinese patients with genetically-undetermined cerebellar ataxia. The clinical presentation and neuroimaging features of patients with m.3243A>G mutation-related cerebellar ataxia were characterized.

RESULTS

We identified two patients harboring m.3243A>G mutation. These patients have suffered from apparently sporadic and slowly progressive cerebellar ataxia since age 52 and 35 years, respectively. Both patients had diabetes mellitus and/or hearing impairment. The neuroimaging studies revealed generalized brain atrophy with predominantly cerebellar involvement in both individuals and bilateral basal ganglia calcifications in one of the patients.

CONCLUSION

Mitochondrial m.3243A>G mutation accounted for 0.9% (2/232) of genetically-undetermined cerebellar ataxia in the Han Chinese cohort in Taiwan. These findings highlight the importance of investigating m.3243A>G in patients with genetically-undetermined cerebellar ataxia.

Multiple system atrophy-cerebellar: A case report and literature review

We reported a case of a 48-year-old female patient admitted to the hospital due to balance disorder which progressed rapidly within 1 week. Cerebral magnetic resonance imaging showed significant atrophy and hyperintensities at the middle cerebellar peduncles and the "hot cross bun" sign of the pons. The final diagnosis was probable multiple system atrophy, cerebellar subtype. The clinical and imaging findings will be discussed as well as a brief literature review.

A novel clinicopathologic entity causing rapidly progressive cerebellar ataxia?

Sporadic, adult-onset cerebellar ataxia is a disease with multiple etiologies. In addition to cortical cerebellar atrophy (CCA), which is often used for the pathological diagnosis, other terms such as idiopathic late-onset cerebellar ataxia (ILOCA) and sporadic adult-onset ataxia of unknown etiology (SAOA) have been used to refer to this disorder. These names describe key features of the disease, including degeneration limited to the cerebellar cortex (with or without secondary involvement of inferior olivary nuclei), a slowly progressive ataxia, and absence of a clear etiology, such as multiple system atrophy, as well as paraneoplastic, autoimmune, infectious and inherited ataxias. In this Point of View article, we describe two patients with sporadic, adult-onset ataxia with rapidly progressive disease course in addition to extracerebellar symptoms resembling prion disease, including the reevaluation of one patient who was previously reported. Pathological findings are mostly consistent with CCA, but also have degenerative changes in the thalamus. Whole genome sequencing in two patients with rapidly progressive CCA did not reveal any pathogenic variants associated with cerebellar ataxia. Although the underlying etiology behind rapidly progressive CCA is unknown, we suggest that the unique combination of clinical and pathological features of CAA with a short disease course defines a new disease entity, rapidly progressive cerebellar cortical and thalamic degeneration. This viewpoint article draws attention to this rare sporadic cerebellar ataxia with the hope that highlighting clinical and pathologic findings in a typical case will lead to improved recognition and research.

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.

Mechanisms of Ethanol-Induced Cerebellar Ataxia: Underpinnings of Neuronal Death in the Cerebellum

Ethanol consumption remains a major concern at a world scale in terms of transient or irreversible neurological consequences, with motor, cognitive, or social consequences. Cerebellum is particularly vulnerable to ethanol, both during development and at the adult stage. In adults, chronic alcoholism elicits, in particular, cerebellar vermis atrophy, the anterior lobe of the cerebellum being highly vulnerable. Alcohol-dependent patients develop gait ataxia and lower limb postural tremor. Prenatal exposure to ethanol causes fetal alcohol spectrum disorder (FASD), characterized by permanent congenital disabilities in both motor and cognitive domains, including deficits in general intelligence, attention, executive function, language, memory, visual perception, and communication/social skills. Children with FASD show volume deficits in the anterior lobules related to sensorimotor functions (Lobules I, II, IV, V, and VI), and lobules related to cognitive functions (Crus II and Lobule VIIB). Various mechanisms underlie ethanol-induced cell death, with oxidative stress and endoplasmic reticulum (ER) stress being the main pro-apoptotic mechanisms in alcohol abuse and FASD. Oxidative and ER stresses are induced by thiamine deficiency, especially in alcohol abuse, and are exacerbated by neuroinflammation, particularly in fetal ethanol exposure. Furthermore, exposure to ethanol during the prenatal period interferes with neurotransmission, neurotrophic factors and retinoic acid-mediated signaling, and reduces the number of microglia, which diminishes expected cerebellar development. We highlight the spectrum of cerebellar damage induced by ethanol, emphasizing physiological-based clinical profiles and biological mechanisms leading to cell death and disorganized development.

Milestones in genetics of cerebellar ataxias

Cerebellar ataxias (CAs) comprise a group of rare, neurological disorders characterized by extensive phenotypic and genetic heterogeneity. The core clinical feature is the cerebellar syndrome, which is often accompanied by other neurological or non-neurological signs. In the last 30 years, our understanding of the CA etiology has increased significantly, and numerous ataxia-associated genes have been discovered. Conventional variants or tandem repeat expansions, localized in the coding or non-coding DNA sequences, lead to hereditary ataxia, which can display different patterns of inheritance. Advances in molecular techniques have enabled a rapid and cost-effective detection of causative variants in a significant number of CA patients. However, despite performing extensive investigations, a definite diagnosis is still unknown in the majority of affected individuals. In this review, we discuss the major advances in the genetics of CAs over the last 30 years, focusing on the impact of next-generation sequencing on the genetic landscape of childhood- and adult-onset CAs. Additionally, we outline possible directions for further genetic research in hereditary and sporadic CAs in the era of increasing application of whole-genome sequencing and genome-wide association studies in various neurological disorders.

Genetic ataxias: update on classification and diagnostic approaches

Ataxia encompasses a large group of rare disorders characterized by irregular movements, decreased coordination, imbalance, kinetic tremor, wide-based stance, and dysarthria. Evaluating ataxia can be challenging considering the volume of disorders and their complex pathologies involving diverse genetic and clinical factors. This is a comprehensive review of the genetic ataxia literature, presenting updated guidelines for differential diagnosis. Age, time course, and family history provide initial guidance for evaluation of ataxia. As genetic testing is increasingly utilized, new genes are discovered and phenotypes for existing disorders are expanded. This review assists physicians by offering a diagnostic roadmap for suspected hereditary ataxia based on the current literature.

Rapid Molecular Screen of Spinocerebellar Ataxia Types 1, 2, and 3 by Triplet-Primed PCR and Melting Curve Analysis

The autosomal dominantly inherited spinocerebellar ataxias (SCAs) can be caused by dynamic mutations of short tandem repeats within various genes. Because of the significant clinical overlap among the various SCA types, molecular screening of multiple genetic loci by fluorescent PCR and capillary electrophoresis is necessary to identify the causative repeat expansion. We describe a simple, rapid, and inexpensive strategy to screen for CAG repeat expansion mutations at the ATXN1, ATXN2, and ATXN3 loci using melting curve analysis of triplet-primed PCR products. Plasmid DNAs of known repeat sizes were used to generate threshold melt peak temperatures, which rapidly and effectively distinguish samples carrying an expanded allele from those carrying nonexpanded alleles. Melting curve analysis-positive samples were confirmed by capillary electrophoresis sizing of the triplet-primed PCR products. All three assays achieved 100% sensitivity, with 95% CIs of 67.86% to 100% (SCA1), 74.65% to 100% (SCA2), and 91.58% to 100% (SCA3). The SCA1 assay also achieved 100% specificity (95% CI, 97.52%-100%), whereas the SCA2 and SCA3 assays achieved specificity of 99.46% (95% CI, 96.56%-99.97%) and 99.32% (95% CI, 95.70%-99.96%), respectively. These screening assays provide robust and highly accurate detection of expanded alleles and are amenable to large-scale screening while minimizing the need for capillary electrophoresis sizing for every sample.

The Value of Sacral Reflex and Sympathetic Skin Reflex in the Diagnosis of Multiple System Atrophy P-Type

Objectives

To observe the characteristics of sacral reflex and sympathetic skin reflex in patients with Parkinson's disease (PD) and multiple system atrophy P-type (MSA-P) and to analyze their value as a differential diagnostic method.

Methods

The data of 30 healthy people, 58 PD patients, and 52 MSA-P patients from the First Affiliated Hospital of Wenzhou Medical University were collected. Electrophysiological bulbocavernosus reflex (BCR) and sympathetic skin response (SSR) were evaluated using the Keypoint EMG/EP system. The latency period, amplitude, and extraction rate of BCR and SSR were compared between the control, PD, and MSA-P groups.

Results

The incidence of the related autonomic damage in the PD group was lower than that of the MSA-P group. For BCR, the latency period was shorter and the amplitude and elicitation rates were lower in the PD group than in the MSA-P group. For SSR, the latency period was longer in the MSA-P and PD groups than in the control group, but the difference was not statistically significant.

Conclusion

SSR cannot be used to assess autonomic nerve function. PD patients can have clinical symptoms similar to those of MSA-P patients, but the incidence is lower. Both MSA-P and PD patients have a damage to the BCR arc, but the MSA-P patients have a more severe damage.

Investigating the Clinical Significance and Research Discrepancies of Balance Training in Degenerative Cerebellar Disease: A Systematic Review

OBJECTIVE

The aims of this study were to understand the clinical significance of balance training in degenerative cerebellar disease and to analyze inconsistencies among published data.

DESIGN

Five databases were searched from inception to October 8, 2019. Cochrane guidelines informed review methods, and Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed. The Australian National Health and Medical Research Council Evidence Hierarchy, PEDro scale, and Joanna Briggs Institute Critical Appraisal Tools were used to evaluate methodological quality. Outcome measures examined included ataxia severity, gait speed, and balance.

RESULTS

Fourteen articles were identified that met inclusion criteria. The quality of evidence was moderate to high, with recent articles being of higher quality. Nine of 12 articles showed statistical improvements in ataxia severity (reduction ranging from 1.4 to 2.8 in the Scale for the Assessment and Rating of Ataxia points), three of eight showed statistical improvements in gait speed (average increase of 0.1 m/sec), and six of nine showed improvements in balance measures (average increase of 1.75 in Berg Balance Scale and 1.5 in Dynamic Gait Index).

CONCLUSION

Most studies showed statistical and clinically significant ataxia severity improvements in subjects who performed balance training. The amount of balance challenge and frequency of training were important factors in determining the extent of training benefit. Gait speed may also improve if walking exercises are included in the balance training, but more studies need to be conducted. Balance measures statistically improved with training, but these improvements did not meet criteria for clinical significance.

TO CLAIM CME CREDITS

Complete the self-assessment activity and evaluation online at http://www.physiatry.org/JournalCME CME OBJECTIVES: Upon completion of this article, the reader should be able to: (1) Describe the cause(s) of discrepancies in the literature regarding the benefits of balance training in degenerative cerebellar disease; (2) Determine if benefits from balance training are clinically meaningful for individuals with cerebellar degeneration; and (3) Understand the best practices gleaned from the current literature regarding balance training for these diseases.

LEVEL

Advanced ACCREDITATION: The Association of Academic Physiatrists is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.The Association of Academic Physiatrists designates this Journal-based CME activity for a maximum of 1.0 AMA PRA Category 1 Credit(s)™. Physicians should only claim credit commensurate with the extent of their participation in the activity.

Expanding the genotype-phenotype correlation of childhood sensory polyneuropathy of genetic origin

Pure sensory polyneuropathy of genetic origin is rare in childhood and hence important to document the clinical and genetic etiologies from single or multi-center studies. This study focuses on a retrospective chart-review of neurological examinations and genetic and electrodiagnostic data of confirmed sensory polyneuropathy in subjects at a tertiary-care Children's Hospital from 2013 to 2019. Twenty subjects were identified and included. Neurological examination and electrodiagnostic testing showed gait-difficulties, absent tendon reflexes, decreased joint-position, positive Romberg's test and large fiber sensory polyneuropathy on sensory nerve conduction studies in all patients associated with lower-extremity spasticity (6), cardiac abnormalities or cardiomyopathy (5), developmental delay (4), scoliosis (3), epilepsy (3) and hearing-difficulties (2). Confirmation of genetic diagnosis in correlation with clinical presentation was obtained in all cases (COX20 n = 2, HADHA n = 2, POLG n = 1, FXN n = 4, ATXN2 n = 3, ATM n = 3, GAN n = 2, SPG7 n = 1, ZFYVE26 n = 1, FH n = 1). Our single-center study shows genetic sensory polyneuropathies associated with progressive neurodegenerative disorders such as mitochondrial ataxia, Friedreich ataxia, spinocerebellar ataxia type 2, ataxia telangiectasia, spastic paraplegia, giant axonal neuropathy, and fumarate hydratase deficiency. We also present our cohort data in light of clinical features reported for each gene-specific disease subtype in the literature and highlight the importance of genetic testing in the relevant clinical context of electrophysiological findings of peripheral sensory polyneuropathy.

Construction of induced pluripotent stem cell line (ZZUi0017-A) from the fibroblast cells of a female patient with CACNA1A mutation by unintegrated reprogramming approach

Ataxia is a common clinical symptom of neurodegenerative diseases, such as spinocerebellar ataxia, Parkinson's disease. Spinocerebellar ataxia includes more than 40 types. In clinical work, we collected the clinical data and skin tissue of one patient with SCA6 who have definitive genetic test results. More than that, we reprogrammed the patient derived fibroblast cells to induced pluripotent stem cells (iPSCs) to construct a SCA6 pathological cell model. The cell line was proved having good pluripotency through detection of pluripotent marker and teratoma formation. This iPS cell line is a special cell model for revealing mechanism and identifying potential therapeutic targets.

Prominent White Matter Involvement in Multiple System Atrophy of Cerebellar Type

BACKGROUND

Sporadic degenerative ataxia patients fall into 2 major groups: multiple system atrophy with predominant cerebellar ataxia (MSA-C) and sporadic adult-onset ataxia (SAOA). Both groups have cerebellar volume loss, but little is known about the differential involvement of gray and white matter in MSA-C when compared with SAOA.

OBJECTIVES

The objective of this study was to identify structural differences of brain gray and white matter between both patient groups.

METHODS

We used magnetic resonance imaging to acquire T1-weighted images and diffusion tensor images from 12 MSA-C patients, 31 SAOA patients, and 55 healthy controls. Magnetic resonance imaging data were analyzed with voxel-based-morphometry, tract-based spatial statistics, and tractography-based regional diffusion tensor images analysis.

RESULTS

Whole-brain and cerebellar-focused voxel-based-morphometry analysis showed gray matter volume loss in both patient groups when compared with healthy controls, specifically in the cerebellar areas subserving sensorimotor functions. When compared with controls, the SAOA and MSA-C patients showed white matter loss in the cerebellum, whereas brainstem white matter was reduced only in the MSA-C patients. The tract-based spatial statistics revealed reduced fractional anisotropy within the pons and cerebellum in the MSA-C patients both in comparison with the SAOA patients and healthy controls. In addition, tractography-based regional analysis showed reduced fractional anisotropy along the corticospinal tracts in MSA-C, but not SAOA.

CONCLUSION

Although in our cohort extent and distribution of gray and white matter loss were similar between the MSA-C and SAOA patients, magnetic resonance imaging data showed prominent microstructural white matter involvement in the MSA-C patients that was not present in the SAOA patients. Our findings highlight the significance of microstructural white matter changes in the differentiation between both conditions. © 2020 The Authors. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

[Diagnostic algorithm for autosomal recessive ataxia]

AIM

To develop a complex algorithm for autosomal recessive ataxia (ARA) diagnosis applicable for Russian patients with degenerative ataxias.

MATERIAL AND METHODS

48 patients with of presumably degenerative ataxias were examined. Clinical evaluation was performed with the use of the SARA and ICARS scales (for ataxia) and MoCA (cognitive functions), and a set of laboratory tests was carried out, including electromyography, brain MRI, and DNA analysis of mutations responsible for Friedreich's disease and spinocerebellar ataxias (SCAs) types 1, 2, 3, 6 and 17. 28 patients underwent mutation screening using a multigenic MPS panel.

RESULTS

8 patients (16.7%) with non-hereditary causes of ataxia were identified: cerebellar alcoholic degeneration (n = 6) and multiple system atrophy of cerebellar type (n = 2); 3 patients (6.3%) with genetic ataxias were identified using routine DNA tests, such as with SCA type 1, 2 and 17, and 9 (18.8%) patients with Friedreich's disease. The MPS panel enabled molecular diagnosis of ARA in 8 patients (28.6%): ataxia-telangiectasia (n = 2), SANDO syndrome (n = 2), ataxia with oculomotor apraxia type 2 (n = 1), SCAR10 (n = 1), SCAR16 (n = 1), and atypical form of neuroaxonal dystrophy (n = 1). The diagnosis was not established in 20 patients.

CONCLUSION

We have proposed an appropriate algorithm for degenerative ataxia diagnosis which is recommended to be used when examining patients with sporadic and autosomal recessive cases of the disorders with dyscoordination of movements.

Quantifying iron deposition in the cerebellar subtype of multiple system atrophy and spinocerebellar ataxia type 6 by quantitative susceptibility mapping

We used quantitative susceptibility mapping (QSM) to assess the brain iron deposition in 28 patients with the cerebellar subtype of multiple system atrophy (MSA-C), nine patients with spinocerebellar ataxia type 6 (SCA6), and 23 healthy controls. Two reviewers independently measured the mean QSM values in brain structures including the putamen, globus pallidus, caudate nucleus, red nucleus, substantia nigra, and cerebellar dentate nucleus. A receiver operating characteristics (ROC) analysis was performed to assess the diagnostic usefulness of the QSM measurements. The QSM values in the substantia nigra were significantly higher in the MSA-C group compared to the HC group (p = .007). The QSM values in the cerebellar dentate nucleus were significantly higher in MSA-C than those in the SCA6 and HC groups (p < .001), and significantly lower in the SCA6 patients compared to the HCs (p = .027). The QSM values in the cerebellar dentate nucleus were correlated with disease duration in MSA-C, but inversely correlated with disease duration in SCA6. In the ROC analysis, the QSM values in the cerebellar dentate nucleus showed excellent accuracy for differentiating MSA-C from SCA6 (area under curve [AUC], 0.925), and good accuracy for differentiating MSA-C from healthy controls (AUC 0.834). QSM can identify increased susceptibility of the substantia nigra and cerebellar dentate nucleus in MSA-C patients. These results suggest that an increase in iron accumulation in the cerebellar dentate nucleus may be secondary to the neurodegeneration associated with MSA-C.

Spinocerebellar ataxia

The spinocerebellar ataxias (SCAs) are a genetically heterogeneous group of autosomal dominantly inherited progressive disorders, the clinical hallmark of which is loss of balance and coordination accompanied by slurred speech; onset is most often in adult life. Genetically, SCAs are grouped as repeat expansion SCAs, such as SCA3/Machado-Joseph disease (MJD), and rare SCAs that are caused by non-repeat mutations, such as SCA5. Most SCA mutations cause prominent damage to cerebellar Purkinje neurons with consecutive cerebellar atrophy, although Purkinje neurons are only mildly affected in some SCAs. Furthermore, other parts of the nervous system, such as the spinal cord, basal ganglia and pontine nuclei in the brainstem, can be involved. As there is currently no treatment to slow or halt SCAs (many SCAs lead to premature death), the clinical care of patients with SCA focuses on managing the symptoms through physiotherapy, occupational therapy and speech therapy. Intense research has greatly expanded our understanding of the pathobiology of many SCAs, revealing that they occur via interrelated mechanisms (including proteotoxicity, RNA toxicity and ion channel dysfunction), and has led to the identification of new targets for treatment development. However, the development of effective therapies is hampered by the heterogeneity of the SCAs; specific therapeutic approaches may be required for each disease.

Idiopathic cerebellar ataxia (IDCA): Diagnostic criteria and clinical analyses of 63 Japanese patients

Cortical cerebellar atrophy (CCA) and multiple system atrophy with predominant cerebellar ataxia (MSA-C) are the two major forms of adult-onset sporadic ataxia. Contrary to MSA-C, there are neither diagnostic criteria nor neuroimaging features pathognomonic for CCA. Therefore, it is assumed that the category of CCA in the Japanese national registry include heterogeneous cerebellar ataxic disorders. To refine this category in more detail, we here used a clinical-based term, "idiopathic cerebellar ataxia (IDCA)", and proposed its diagnostic criteria. We collected 346 consecutive patients with the core features of the criteria (sporadic, insidious-onset and slowly progressive cerebellar ataxia in adults, and cerebellar atrophy on brain imaging). Of these, 212 (61.3%) were diagnosed with probable or possible MSA, and 30, who did not meet the diagnostic criteria for MSA at examination, were also excluded because of MRI findings suggestive of MSA. Twenty two were proven to have hereditary spinocerebellar ataxias by genetic testing, and 19 had secondary ataxias. Finally, the remaining 63 (18.2%) were diagnosed with IDCA. The mean (standard deviation) age at onset was 57.2 (10.8) years. Of these, 25 (39.7%) showed pure cerebellar ataxia, and the remaining 38 (60.3%) had some of extracerebellar features including abnormal tendon reflexes (46.0%), positive Babinski sign (9.5%), sensory disturbance (12.7%), cognitive impairment (9.5%), and involuntary movements (7.9%). Our results show that IDCA refined by the diagnostic criteria still includes clinically and genetically heterogeneous ataxic disorders. More extensive genetic analyses will be of significance for further clarification of this group.

Multiple System Atrophy: An Oligodendroglioneural Synucleinopathy1

Multiple system atrophy (MSA) is an orphan, fatal, adult-onset neurodegenerative disorder of uncertain etiology that is clinically characterized by various combinations of parkinsonism, cerebellar, autonomic, and motor dysfunction. MSA is an α-synucleinopathy with specific glioneuronal degeneration involving striatonigral, olivopontocerebellar, and autonomic nervous systems but also other parts of the central and peripheral nervous systems. The major clinical variants correlate with the morphologic phenotypes of striatonigral degeneration (MSA-P) and olivopontocerebellar atrophy (MSA-C). While our knowledge of the molecular pathogenesis of this devastating disease is still incomplete, updated consensus criteria and combined fluid and imaging biomarkers have increased its diagnostic accuracy. The neuropathologic hallmark of this unique proteinopathy is the deposition of aberrant α-synuclein in both glia (mainly oligodendroglia) and neurons forming glial and neuronal cytoplasmic inclusions that cause cell dysfunction and demise. In addition, there is widespread demyelination, the pathogenesis of which is not fully understood. The pathogenesis of MSA is characterized by propagation of misfolded α-synuclein from neurons to oligodendroglia and cell-to-cell spreading in a "prion-like" manner, oxidative stress, proteasomal and mitochondrial dysfunction, dysregulation of myelin lipids, decreased neurotrophic factors, neuroinflammation, and energy failure. The combination of these mechanisms finally results in a system-specific pattern of neurodegeneration and a multisystem involvement that are specific for MSA. Despite several pharmacological approaches in MSA models, addressing these pathogenic mechanisms, no effective neuroprotective nor disease-modifying therapeutic strategies are currently available. Multidisciplinary research to elucidate the genetic and molecular background of the deleterious cycle of noxious processes, to develop reliable biomarkers and targets for effective treatment of this hitherto incurable disorder is urgently needed.

The Etiologies of Chronic Progressive Cerebellar Ataxia in a Korean Population

Background and Purpose

The etiologies and frequencies of cerebellar ataxias vary between countries. Our primary aim was to determine the frequency of each diagnostic group of cerebellar ataxia patients in a Korean population.

Methods

We reviewed the medical records of patients who were being followed up between November 1994 and February 2016. We divided patients with cerebellar ataxias into familial and non-familial groups and analyzed the frequency of each etiology. Finally, we categorized patients into genetic, sporadic, secondary, and suspected genetic, but undetermined ataxia.

Results

A total of 820 patients were included in the study, among whom 136 (16.6%) familial patients and 684 (83.4%) non-familial cases were identified. Genetic diagnoses confirmed 98/136 (72%) familial and 72/684 (11%) nonfamilial patients. The overall etiologies of progressive ataxias comprised 170 (20.7%) genetic, 516 (62.9%) sporadic, 43 (5.2%) secondary, and 91 (11.1%) undetermined ataxia. The most common cause of ataxia was multiple-system atrophy (57.3%). In the genetic group, the most common etiology was spinocerebellar ataxia (152/170, 89.4%) and the most common subtype was spinocerebellar ataxia-3.38 of 136 familial and 53 of 684 sporadic cases (91/820, 11.1%) were undetermined ataxia.

Conclusions

This is the largest epidemiological study to analyze the frequencies of various cerebellar ataxias in a Korean population based on the large database of a tertiary hospital movement-disorders clinic in South Korea. These data would be helpful for clinicians in constructing diagnostic strategies and counseling for patients with cerebellar ataxias.

Mortality Statistics and their Contribution to Improving the Knowledge of Rare Diseases Epidemiology: The Example of Hereditary Ataxia in Europe

Official mortality statistics provide population-based data and serve to improve epidemiological knowledge of rare diseases (RDs), by helping with the description of the natural history of the disease. They are an important complement of registries and estimates of disease burden and costs. At the same time, they heighten both the visibility of these diseases and the interest in their study and the search for treatments that may increase survival. This chapter contains a European analysis of hereditary ataxia mortality, which considers the time trend in different countries and the geographical variability in risk of death. Despite the limitations of applying this data source to RDs, mortality statistics share criteria which facilitate international comparisons and are of great utility for obtaining sufficiently uniform and robust time series for analysis of low-prevalence diseases.

The Diagnosis and Natural History of Multiple System Atrophy, Cerebellar Type

The objective of this study was to identify key features differentiating multiple system atrophy cerebellar type (MSA-C) from idiopathic late-onset cerebellar ataxia (ILOCA). We reviewed records of patients seen in the Massachusetts General Hospital Ataxia Unit between 1992 and 2013 with consensus criteria diagnoses of MSA-C or ILOCA. Twelve patients had definite MSA-C, 53 had possible/probable MSA-C, and 12 had ILOCA. Autonomic features, specifically urinary urgency, frequency, and incontinence with erectile dysfunction in males, differentiated MSA-C from ILOCA throughout the disease course (p = 0.005). Orthostatic hypotension developed later and differentiated MSA-C from ILOCA (p < 0.01). REM sleep behavior disorder (RBD) occurred early in possible/probable MSA-C (p < 0.01). Late MSA-C included pathologic laughing and crying (PLC, p < 0.01), bradykinesia (p = 0.01), and corticospinal findings (p = 0.01). MRI distinguished MSA-C from ILOCA by atrophy of the brainstem (p < 0.01) and middle cerebellar peduncles (MCP, p = 0.02). MSA-C progressed faster than ILOCA: by 6 years, MSA-C walker dependency was 100 % and ILOCA 33 %. MSA-C survival was 8.4 ± 2.5 years. Mean length of ILOCA illness to date is 15.9 ± 6.4 years. A sporadic onset, insidiously developing cerebellar syndrome in midlife, with autonomic features of otherwise unexplained bladder dysfunction with or without erectile dysfunction in males, and atrophy of the cerebellum, brainstem, and MCP points strongly to MSA-C. RBD and postural hypotension confirm the diagnosis. Extrapyramidal findings, corticospinal tract signs, and PLC are helpful but not necessary for diagnosis. Clarity in early MSA-C diagnosis can prevent unnecessary investigations and facilitate therapeutic trials.

Clinical and genetic characteristics of sporadic adult-onset degenerative ataxia

Objective:

To define the clinical phenotype and natural history of sporadic adult-onset degenerative ataxia and to identify putative disease-causing mutations.

Methods:

The primary measure of disease severity was the Scale for the Assessment and Rating of Ataxia (SARA). DNA samples were screened for mutations using a high-coverage ataxia-specific gene panel in combination with next-generation sequencing.

Results:

The analysis was performed on 249 participants. Among them, 83 met diagnostic criteria of clinically probable multiple system atrophy cerebellar type (MSA-C) at baseline and another 12 during follow-up. Positive MSA-C criteria (4.94 ± 0.74, p < 0.0001) and disease duration (0.22 ± 0.06 per additional year, p = 0.0007) were associated with a higher SARA score. Forty-eight participants who did not fulfill MSA-C criteria and had a disease duration of >10 years were designated sporadic adult-onset ataxia of unknown etiology/non-MSA (SAOA/non-MSA). Compared with MSA-C, SAOA/non-MSA patients had lower SARA scores (13.6 ± 6.0 vs 16.0 ± 5.8, p = 0.0200) and a slower annual SARA increase (1.1 ± 2.3 vs 3.3 ± 3.2, p = 0.0013). In 11 of 194 tested participants (6%), a definitive or probable genetic diagnosis was made.

Conclusions:

Our study provides quantitative data on the clinical phenotype and progression of sporadic ataxia with adult onset. Screening for causative mutations with a gene panel approach yielded a genetic diagnosis in 6% of the cohort.

ClinicalTrials.gov registration:

NCT02701036.

Rehabilitation for Individuals With Genetic Degenerative Ataxia: A Systematic Review

BACKGROUND

Treatment of genetic degenerative ataxia is currently based on symptom management and maintenance of function. However, utilization of rehabilitation is limited due to a lack of evidence supporting its efficacy.

OBJECTIVE

This systematic review evaluated rehabilitation interventions for individuals with genetic degenerative ataxia. In addition, long-term outcomes from rehabilitation and optimal duration and intensity of rehabilitation were examined.

METHODS

A comprehensive search of 4 databases (MEDLINE, CINAHL, PEDro, and Cochrane) identified randomized, nonrandomized controlled, and cohort studies published from inception through to January 2016. The studies included at least one measure examining function, ataxia, balance, or gait. Methodological quality was assessed with the Australian National Health and Medical Research Council (NHMRC) Hierarchy of Evidence and the randomized controlled trials were rated according to the PEDro scale.

RESULTS

Seventeen studies met eligibility criteria. Five randomized controlled trials were included; however, the majority were classified as level III-3 and IV studies. Of 292 participants included, 148 had autosomal dominant ataxia, and 85 had autosomal recessive ataxia. Rehabilitation interventions included coordination and balance training, multifaceted inpatient rehabilitation, a cycling regime, balance exercises with technology assisted biofeedback, respiratory muscle training, and treadmill training. Two studies examined adjuncts to rehabilitation. Fifteen of the 17 studies demonstrated a statistically significant improvement in at least 1 outcome measuring ataxia, function, gait, or balance. Less than half of the studies included assessment of long-term outcomes and follow-up time frames varied considerably.

CONCLUSION

There is consistent evidence that rehabilitation improves function, mobility, ataxia, and balance in genetic degenerative ataxia.

Deciphering the causes of sporadic late-onset cerebellar ataxias: a prospective study with implications for diagnostic work

The management of sporadic late-onset cerebellar ataxias represents a very heterogeneous group of patients and remains a challenge for neurologist in clinical practice. We aimed at describing the different causes of sporadic late-onset cerebellar ataxias that were diagnosed following standardized, exhaustive investigations and the population characteristics according to the aetiologies as well as at evaluating the relevance of these investigations. All patients consecutively referred to our centre due to sporadic, progressive cerebellar ataxia occurring after 40 years of age were included in the prospective, observational study. 80 patients were included over a 2 year period. A diagnosis was established for 52 patients (65%) corresponding to 18 distinct causes, the most frequent being cerebellar variant of multiple system atrophy (n = 29). The second most frequent cause was inherited diseases (including spinocerebellar ataxias, late-onset Friedreich's disease, SLC20A2 mutations, FXTAS, MELAS, and other mitochondrial diseases) (n = 9), followed by immune-mediated or other acquired causes. The group of patient without diagnosis showed a slower worsening of ataxia (p < 0.05) than patients with multiple system atrophy. Patients with later age at onset experienced faster progression of ataxia (p = 0.001) and more frequently parkinsonism (p < 0.05) than patients with earlier onset. Brain MRI, DaT scan, genetic analysis and to some extent muscle biopsy, thoracic-abdominal-pelvic tomodensitometry, and cerebrospinal fluid analysis were the most relevant investigations to explore sporadic late-onset cerebellar ataxia. Sporadic late-onset cerebellar ataxias should be exhaustively investigated to identify the underlying causes that are numerous, including inherited causes, but dominated by multiple system atrophy.

Determination of Genotypic and Phenotypic Characteristics of Friedreich's Ataxia and Autosomal Dominant Spinocerebellar Ataxia Types 1, 2, 3, and 6

INTRODUCTION

This study aimed to analyze the genotypic characteristics of Friedreich's ataxia (FA) and autosomal dominant ataxias [such as spinocerebellar ataxia (SCA) types 1, 2, 3, and 6] using molecular and biological methods in hereditary cerebellar ataxia considering both clinical and electrophysiological findings.

METHODS

The study included 129 indexed cases, who applied to the neurology department and were diagnosed with hereditary cerebellar ataxia through clinical, laboratory, and electrophysiological findings, and 15 sibling patients who were diagnosed through family scanning (144 cases in total); their genetic analyses were also performed. Detailed physical and neurological examinations, pedigree analyses, electroneurography, evoked potentials, cerebral-spinal magnetic resonance imaging, and echocardiographic analyses were performed for all cases. Blood samples were collected from patients, and the genotypic characteristics of autosomal dominant SCA types 1, 2, 3, and 6 were investigated. Statistical analyses were performed with the Statistical Package for the Social Sciences (SPSS Inc; Chicago, IL, USA) 17.0.

RESULTS

Almost 50% of patients were defined as FA. Moreover, two SCA1 cases and one SCA6 case were detected.

CONCLUSION

In our study, 47.2% of patients with FA had developed hereditary cerebellar ataxia. Ground and autosomal dominant-linked SCA1 and SCA6 were each detected in one family. These data suggest that patients with cerebellar ataxia of hereditary origin should be primarily examined for FA.

Idiopathic very late-onset cerebellar ataxia: a Brazilian case series

The authors present a Brazilian case series of eight patients with idiopathic very-late onset (mean 75.5 years old) cerebellar ataxia, featuring predominantly gait ataxia, associated with cerebellar atrophy.

METHOD

26 adult patients with a diagnosis of idiopathic late onset cerebellar ataxia were analyzed in a Brazilian ataxia outpatient clinic and followed regularly over 20 years. Among them, 8 elderly patients were diagnosed as probable very late onset cerebellar ataxia. These patients were evaluated with neurological, ophthalmologic and Mini-Mental Status examinations, brain MRI, and EMG.

RESULTS

62.5% of patients were males, mean age was 81.9 years-old, and mean age of onset was 75.5 years. Gait cerebellar ataxia was observed in all patients, as well as, cerebellar atrophy on brain MRI. Mild cognitive impairment and visual loss, due to macular degeneration, were observed in 50% of cases. Chorea was concomitantly found in 3 patients.

CONCLUSION

We believe that this condition is similar the one described by Marie-Foix-Alajouanine presenting with mild dysarthria, associated with gait ataxia, and some patients had cognitive dysfunction and chorea.

Genetics Underlying Atypical Parkinsonism and Related Neurodegenerative Disorders

Atypical parkinsonism syndromes, such as dementia with Lewy bodies, multiple system atrophy, progressive supranuclear palsy and corticobasal degeneration, are neurodegenerative diseases with complex clinical and pathological features. Heterogeneity in clinical presentations, possible secondary determinants as well as mimic syndromes pose a major challenge to accurately diagnose patients suffering from these devastating conditions. Over the last two decades, significant advancements in genomic technologies have provided us with increasing insights into the molecular pathogenesis of atypical parkinsonism and their intriguing relationships to related neurodegenerative diseases, fueling new hopes to incorporate molecular knowledge into our diagnostic, prognostic and therapeutic approaches towards managing these conditions. In this review article, we summarize the current understanding of genetic mechanisms implicated in atypical parkinsonism syndromes. We further highlight mimic syndromes relevant to differential considerations and possible future directions.

Diagnosis and differential diagnosis of MSA: boundary issues

Because the progression of multiple system atrophy (MSA) is usually rapid and there still is no effective cause-related therapy, early and accurate diagnosis is important for the proper management of patients as well as the development of neuroprotective agents. However, despite the progression in the field of MSA research in the past few years, the diagnosis of MSA in clinical practice still relies largely on clinical features and there are limitations in terms of sensitivity and specificity, especially in the early course of the disease. Furthermore, recent pathological, clinical, and neuroimaging studies have shown that (1) MSA can present with a wider range of clinical and pathological features than previously thought, including features considered atypical for MSA; thus, MSA can be misdiagnosed as other diseases, and conversely, disorders with other etiologies and pathologies can be clinically misdiagnosed as MSA; and (2) several investigations may help to improve the diagnosis of MSA in clinical practice. These aspects should be taken into consideration when revising the current diagnostic criteria. This is especially true given that disease-modifying treatments for MSA are under investigation.

Dynamic Cerebrospinal Fluid Flow on MRI in Cortical Cerebellar Atrophy and Multiple System Atrophy-cerebellar Type

OBJECTIVE

The purpose of this study was to examine a new MRI technology, dynamic cerebrospinal fluid (CSF) flow, to examine sporadic cerebellar ataxia patients with cortical cerebellar atrophy (CCA) and multiple system atrophy-cerebellar type (MSA-C).

METHODS

Nine CCA patients (3 men and 6 women; mean age: 64.2±6.9 years) and 31 MSA-C patients (13 men and 18 women; mean age: 62.7±6.8 years) were examined by a dynamic CSF flow analysis. All CSF flow data were evaluated by phase contrast-MRI using a 1.5T MRI scanner. The CSF flow was calculated by 15 images in the equidistant MRI sequence which was taken through a cardiac cycle.

RESULTS

Compared with the CCA patients, the absolute values of the mean velocity of the MSA-C patients were significantly reduced at time points 5 (CCA, 0.24±0.14 cm/s; MSA-C, 0.13±0.11 cm/s; (*) p<0.05) and 13 (CCA, -0.60±0.37 cm/s; MSA-C, -0.31±0.17 cm/s; (**) p<0.01). Significant correlations in Spearman's rank correlation coefficient were also found in MSA-C patients between the disease duration and the difference between the maximum and minimum velocities (Vheight) (r=-0.429, (*) p<0.05), the minimum velocity of the CSF (Vmin) (r=0.486, (**) p<0.01) or the length of the minor axis of the pons (r=-0.529, (**) p<0.01). The linear regressions between the disease duration and Vheight or Vmin revealed a significant strong correlation only in the MSA-C patients.

CONCLUSION

The present CSF flow study showed for the first time that Vheight and Vmin revealed good correlations with the disease duration in the MSA-C patients. Furthermore, the velocity of the prepontine CSF flow tended to decrease in the MSA-C patients compared with the CCA patients, suggesting that this particular CSF flow analysis may be a new surrogate marker for differentiating both types of cerebellar ataxia.

Multiple system atrophy of the cerebellar type: clinical state of the art

Multiple system atrophy (MSA) is a late-onset, sporadic neurodegenerative disorder clinically characterized by autonomic failure and either poorly levodopa-responsive parkinsonism or cerebellar ataxia. It is neuropathologically defined by widespread and abundant central nervous system α-synuclein-positive glial cytoplasmic inclusions and striatonigral and/or olivopontocerebellar neurodegeneration. There are two clinical subtypes of MSA distinguished by the predominant motor features: the parkinsonian variant (MSA-P) and the cerebellar variant (MSA-C). Despite recent progress in understanding the pathobiology of MSA, investigations into the symptomatology and natural history of the cerebellar variant of the disease have been limited. MSA-C presents a unique challenge to both clinicians and researchers alike. A key question is how to distinguish early in the disease course between MSA-C and other causes of adult-onset cerebellar ataxia. This is a particularly difficult question, because the clinical framework for conceptualizing and studying sporadic adult-onset ataxias continues to undergo flux. To date, several investigations have attempted to identify clinical features, imaging, and other biomarkers that may be predictive of MSA-C. This review presents a clinically oriented overview of our current understanding of MSA-C with a focus on evidence for distinguishing MSA-C from other sporadic, adult-onset ataxias.

EFNS/ENS Consensus on the diagnosis and management of chronic ataxias in adulthood

BACKGROUND AND OBJECTIVES

The ataxias are a challenging group of neurological diseases due the aetiological heterogeneity and the complexity of the genetic subtypes. This guideline focuses on the heredodegenerative ataxias. The aim is to provide a peer-reviewed evidence-based guideline for clinical neurologists and other specialist physicians responsible for the care of patients with ataxia.

METHODS

This guideline is based on systematic evaluations of the relevant literature and on three consensus meetings of the task force.

DIAGNOSIS

If acquired causes are ruled out, and if the disease course is rather slowly progressive, a (heredo)degenerative disease is likely. A positive family history gives much guidance. In the case of a dominant family history, first line genetic screening is recommended for spinocerebellar ataxia (SCA) 1, 2, 3, 6, 7 and 17 (level B), and in Asian patients also for dentatorubral-pallidoluysian atrophy (DRPLA). In the case of recessive disease, a stepwise diagnostic work-up is recommended, including both biochemical markers and targeted genetic testing, particularly aimed at Friedreich's ataxia, ataxia telangiectasia, ataxia due to vitamin E deficiency, polymerase gamma gene (POLG gene, various mutations), autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) and ataxia with oculomotor apraxia (AOA) types 1 and 2. If family history is negative, we still advise to screen for the more common dominant and recessive ataxias. In addition, if onset is below 45 years we recommend the full work-up for recessive ataxias; if onset is above 45 years we recommend to screen for fragile X mental retardation 1 FMR1 premutations (good practice points). In sporadic cases with an onset after 30 years, a diagnosis of multiple system atrophy should be considered (good practice point). In particular the genetic work-up will change over the upcoming years due to the diagnostic utility of new techniques such as gene panel diagnostics based on next generation sequencing for routine work-up, or even whole exome and genome sequencing for selected cases.

TREATMENT

Some of the rare recessive ataxias are treatable, but for most of the heredodegenerative ataxias treatment is purely symptomatic. Idebenone is not effective in Friedreich's ataxia (level A). Riluzole (level B) and amantadine (level C) might provide symptomatic relief, irrespective of exact etiology. Also, varenicline for SCA3 patients (level B) can be considered. There is level Class II evidence to recommend physiotherapy, and Class III data to support occupational therapy.

De novo mutations in ataxin-2 gene and ALS risk

Pathogenic CAG repeat expansion in the ataxin-2 gene (ATXN2) is the genetic cause of spinocerebellar ataxia type 2 (SCA2). Recently, it has been associated with Parkinsonism and increased genetic risk for amyotrophic lateral sclerosis (ALS). Here we report the association of de novo mutations in ATXN2 with autosomal dominant ALS. These findings support our previous conjectures based on population studies on the role of large normal ATXN2 alleles as the source for new mutations being involved in neurodegenerative pathologies associated with CAG expansions. The de novo mutations expanded from ALS/SCA2 non-risk alleles as proven by meta-analysis method. The ALS risk was associated with SCA2 alleles as well as with intermediate CAG lengths in the ATXN2. Higher risk for ALS was associated with pathogenic CAG repeat as revealed by meta-analysis.

Hereditäre Ataxien

Hereditäre Ataxien stellen aufgrund der Vielfalt der möglichen genetischen Ursachen eine große diagnostische Herausforderung für die medizinische Genetik dar. Dieses Problem wird dadurch verstärkt, dass zwar die Zahl der neu identifizierten Gene in den letzten 3 Jahren durch neue Sequenziertechnologien rasant zugenommen hat, häufig jedoch nur wenige Familien weltweit Mutationen in diesen Genen aufweisen, d. h. sie extrem selten sind. Der vorliegende Artikel gibt eine Übersicht über dominante und rezessive Ataxien und berücksichtigt dabei auch die neu identifizierten Ataxie-Gene. Um den Anforderungen einer praktisch-orientierten genetischen Diagnostik gerecht zu werden, versuchen wir dabei auch, Häufigkeitseinschätzungen der betroffenen Genorte zu geben und – sofern möglich – phänotypische Eigenschaften und Biomarker zu definieren, die eine genetische Diagnostik erfolgversprechend leiten können, insbesondere bei rezessiven Ataxien. Diese diagnostischen Indikatoren werden in Form von diagnostischen Pfaden zusammengefasst, die eine Orientierung bei der mehrstufigen genetischen Diagnostik dominanter und rezessiver Ataxien geben sollen. Aufgrund der Vielzahl der Genkandidaten und des großen phänotypischen Überlappungsbereichs wird es in den meisten Fällen jedoch am zeiteffizientesten und kostengünstigsten sein, Panel-Untersuchungen mittels Next-Generation-Sequencing-Technologien durchzuführen.

Clinical features, neurogenetics and neuropathology of the polyglutamine spinocerebellar ataxias type 1, 2, 3, 6 and 7

The spinocerebellar ataxias type 1 (SCA1), 2 (SCA2), 3 (SCA3), 6 (SCA6) and 7 (SCA7) are genetically defined autosomal dominantly inherited progressive cerebellar ataxias (ADCAs). They belong to the group of CAG-repeat or polyglutamine diseases and share pathologically expanded and meiotically unstable glutamine-encoding CAG-repeats at distinct gene loci encoding elongated polyglutamine stretches in the disease proteins. In recent years, progress has been made in the understanding of the pathogenesis of these currently incurable diseases: Identification of underlying genetic mechanisms made it possible to classify the different ADCAs and to define their clinical and pathological features. Furthermore, advances in molecular biology yielded new insights into the physiological and pathophysiological role of the gene products of SCA1, SCA2, SCA3, SCA6 and SCA7 (i.e. ataxin-1, ataxin-2, ataxin-3, α-1A subunit of the P/Q type voltage-dependent calcium channel, ataxin-7). In the present review we summarize our current knowledge about the polyglutamine ataxias SCA1, SCA2, SCA3, SCA6 and SCA7 and compare their clinical and electrophysiological features, genetic and molecular biological background, as well as their brain pathologies. Furthermore, we provide an overview of the structure, interactions and functions of the different disease proteins. On the basis of these comprehensive data, similarities, differences and possible disease mechanisms are discussed.

Spinocerebellar ataxia type 12

SCA12 is a late-onset, autosomal dominant, slowly progressive disorder. Action tremor is the usual presenting sign. Subsequent development of ataxia and hyperreflexia suggests spinocerebellar ataxia. In the index SCA12 kindred, which resides in North America and is of German ancestry, parkinsonism, anxiety, depression, and cognitive dysfunction are not uncommon. SCA12 is linked to a CAG repeat expansion mutation in exon 7 of PPP2R2B, a gene that encodes Bβ, a regulatory subunit of protein phosphatase 2A (PP2A). CAG repeats number 7-28 in normal individuals and 55-78 in SCA12 patients. The mechanism by which this mutation leads to SCA12 has not been determined. The CAG expansion in PPP2R2B has promoter function in vitro. CAG length correlates with increased Bβ expression. There is no evidence that this CAG expansion results in polyglutamine production. In addition to the North. American SCA12 kindred, multiple SCA12 families have been found in Northern India that are not related to the index SCA12 kindred. SCA12 has been reported, rarely, in Singapore and China. Action tremor, anxiety, and depression in SCA12 have responded to usual treatments for these disorders. SCA12 may be considered in patients who present with action tremor and later develop signs of cerebellar and cortical dysfunction.

Sporadic adult-onset ataxia of unknown etiology

Sporadic adult-onset ataxia of unknown etiology (SAOA) denotes the non-hereditary degenerative adult-onset ataxia disorders that are distinct from multiple system atrophy (MSA). Rather than being a defined disease entity, SAOA has to be regarded as a group of disorders of unknown etiology that are defined by a common clinical syndrome and the exclusion of known disease causes. Epidemiological studies have revealed prevalence rates ranging from 2.2 to 8.4 per 100000, which are higher than those of hereditary ataxias. Clinically, SAOA is characterized by a slowly progressive cerebellar syndrome starting around the age of 50 years. About one-third of SAOA patients have either polyneuropathy or pyramidal tract involvement accompanying cerebellar ataxia. Cognitive impairment is not the rule, and, if present, is only mild. More than half of SAOA patients have signs of mild autonomic dysfunction that do not meet the criteria of severe autonomic failure required for a diagnosis of MSA. Neuropathological and imaging studies show an isolated cerebellar cortical degeneration with no or only mild brainstem involvement. There is no established therapy for SAOA.

Frequency of KCNC3 DNA variants as causes of spinocerebellar ataxia 13 (SCA13)

Background

Gain-of function or dominant-negative mutations in the voltage-gated potassium channel KCNC3 (Kv3.3) were recently identified as a cause of autosomal dominant spinocerebellar ataxia. Our objective was to describe the frequency of mutations associated with KCNC3 in a large cohort of index patients with sporadic or familial ataxia presenting to three US ataxia clinics at academic medical centers.

Methodology

DNA sequence analysis of the coding region of the KCNC3 gene was performed in 327 index cases with ataxia. Analysis of channel function was performed by expression of DNA variants in Xenopus oocytes.

Principal Findings

Sequence analysis revealed two non-synonymous substitutions in exon 2 and five intronic changes, which were not predicted to alter splicing. We identified another pedigree with the p.Arg423His mutation in the highly conserved S4 domain of this channel. This family had an early-onset of disease and associated seizures in one individual. The second coding change, p.Gly263Asp, subtly altered biophysical properties of the channel, but was unlikely to be disease-associated as it occurred in an individual with an expansion of the CAG repeat in the CACNA1A calcium channel.

Conclusions

Mutations in KCNC3 are a rare cause of spinocerebellar ataxia with a frequency of less than 1%. The p.Arg423His mutation is recurrent in different populations and associated with early onset. In contrast to previous p.Arg423His mutation carriers, we now observed seizures and mild mental retardation in one individual. This study confirms the wide phenotypic spectrum in SCA13.

The 'hot cross bun' sign in the patients with spinocerebellar ataxia

BACKGROUND AND PURPOSE

The 'hot cross bun' sign (HCBS), typically seen in the patients with multiple system atrophy, refers to a cruciform hyperintensity in the pons on T2-weighted MRI. Little is known about its pathological basis and prevalence in other degenerative cerebellar diseases and healthy population. We investigate the frequency of HCBS in the patients with spinocerebellar ataxia (SCA) and healthy controls.

METHODS

The presence of HCBS on T2-weighted axial MRIs from 138 SCA patients (three SCA1, 35 SCA2, 76 SCA3, 18 SCA6, one SCA7, three SCA8, and two SCA17) and 102 healthy controls was evaluated retrospectively.

RESULTS

The overall prevalence of HCBS in the SCA patients is 8.7%, but the frequency varies in different subtypes: 25.7% in SCA2, 1.3% in SCA3, and none in SCA6 or healthy controls. Notably, one patient with SCA7 and one with SCA8 were also found to have HCBS.

CONCLUSIONS

The differential list of HCBS should be expanded to include SCA7 and SCA8. The elucidation of frequency of HCBS in various SCA subtypes may help prioritize the genetic testing in late-onset dominant ataxia.