Inherited cerebellar ataxia in childhood: a pattern-recognition approach using brain MRI

An overview of early-onset cerebellar ataxia: a practical guideline

Early onset ataxias (EOAs) are a heterogeneous group of rare neurological disorders that not only involve the central and peripheral nervous system but also involve other organs. They are mainly manifested by degeneration or abnormal development of the cerebellum occurring before the age of 25 years and typically the pattern of inheritance is autosomal recessive.The diagnosis of autosomal recessive cerebellar ataxias (ARCAs) is confirmed by the clinical, laboratory, electrophysiological examination, neuroimaging findings, and mutation analysis when the causative gene is detected. Correct diagnosis is crucial for appropriate genetic counseling, estimating the prognosis, and, in some cases, pharmacological intervention. The wide variety of genotypes with a heterogeneous phenotypic manifestation makes the diagnostic work-up challenging, time-consuming, and expensive, not only for the clinician but also for the children and their parents. In this review, we focused on the step-by-step approach in which cerebellar ataxia is a prominent sign. We also outline the most common disorders in ataxias with early-onset manifestations.

Ataxia in Neurometabolic Disorders

Ataxia is a movement disorder that manifests during the execution of purposeful movements. It results from damage to the structures of the cerebellum and its connections or the posterior cords of the spinal cord. It should be noted that, in addition to occurring as part of many diseases, pediatric ataxia is a common symptom in neurometabolic diseases. To date, there are more than 150 inherited metabolic disorders that can manifest as ataxia in children. Neuroimaging studies (magnetic resonance imaging of the head and spinal cord) are essential in the diagnosis of ataxia, and genetic studies are performed when metabolic diseases are suspected. It is important to remember that most of these disorders are progressive if left untreated. Therefore, it is crucial to include neurometabolic disorders in the differential diagnosis of ataxia, so that an early diagnosis can be made. Initiating prompt treatment influences positive neurodevelopmental outcomes.

ACR Appropriateness Criteria® Ataxia-Child

Childhood ataxia may be due to multifactorial causes of impairment in the coordination of movement and balance. Acutely presenting ataxia in children may be due to infectious, inflammatory, toxic, ischemic, or traumatic etiology. Intermittent or episodic ataxia in children may be manifestations of migraine, benign positional vertigo, or intermittent metabolic disorders. Nonprogressive childhood ataxia suggests a congenital brain malformation or early prenatal or perinatal brain injury, and progressive childhood ataxia indicates inherited causes or acquired posterior fossa lesions that result in gradual cerebellar dysfunction. CT and MRI of the central nervous system are the usual modalities used in imaging children presenting with ataxia, based on the clinical presentation. This document provides initial imaging guidelines for a child presenting with acute ataxia with or without a history of recent trauma, recurrent ataxia with interval normal neurological examination, chronic progressive ataxia, and chronic nonprogressive ataxia. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances in which peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

Combined Genome, Transcriptome and Metabolome Analysis in the Diagnosis of Childhood Cerebellar Ataxia

Ataxia in children is a common clinical sign of numerous neurological disorders consisting of impaired coordination of voluntary muscle movement. Its most common form, cerebellar ataxia, describes a heterogeneous array of neurologic conditions with uncountable causes broadly divided as acquired or genetic. Numerous genetic disorders are associated with chronic progressive ataxia, which complicates clinical management, particularly on the diagnostic stage. Advances in omics technologies enable improvements in clinical practice and research, so we proposed a multi-omics approach to aid in the genetic diagnosis and molecular elucidation of an undiagnosed infantile condition of chronic progressive cerebellar ataxia. Using whole-exome sequencing, RNA-seq, and untargeted metabolomics, we identified three clinically relevant mutations (rs141471029, rs191582628 and rs398124292) and an altered metabolic profile in our patient. Two POLR1C diagnostic variants already classified as pathogenic were found, and a diagnosis of hypomyelinating leukodystrophy was achieved. A mutation on the MMACHC gene, known to be associated with methylmalonic aciduria and homocystinuria cblC type, was also found. Additionally, preliminary metabolome analysis revealed alterations in our patient's amino acid, fatty acid and carbohydrate metabolism. Our findings provided a definitive genetic diagnosis reinforcing the association between POLR1C mutations and hypomyelinating leukodystrophy and highlighted the relevance of multi-omics approaches to the disease.

Clinical, Cognitive and Behavioural Assessment in Children with Cerebellar Disorder

Cerebellar disorders are characterised clinically by specific signs and symptoms, often associated with neurodevelopmental disorder. While the clinical signs of cerebellar disorders are clearly recognisable in adults and have a precise anatomo-functional correlation, in children the semiotics are less clear and vary with age because of the particular nature of the cerebellum’s maturation. Unlike other structures of the central nervous system, this begins at a later stage of foetal development and extends over a longer period of time, even after birth. As a result, the typical signs of cerebellar dysfunction will only become evident when the cerebellar functions have become integrated into the complex circuits of the central nervous system. This means that poor motor coordination in the very early years of life may not necessarily correlate with cerebellar dysfunction, and this may also be encountered in healthy children. The cerebellum’s role in cognitive and emotional functions relies on its structure and the complexity of its connections. Cognitive and behavioral impairment in cerebellar disorders can be the results of acquired lesions or the action of genetic and environmental risk factors, to which the cerebellum is particularly vulnerable considering its pattern of development. In the pathological setting, early evidence of cerebellar damage may be very vague, due, partly, to spontaneous compensation phenomena and the vicarious role of the connecting structures (an expression of the brain’s plasticity). Careful clinical assessment will nonetheless enable appropriate instrumental procedures to be arranged. It is common knowledge that the contribution of neuroimaging is crucial for diagnosis of cerebellar conditions, and neurophysiological investigations can also have a significant role. The ultimate goal of clinicians is to combine clinical data and instrumental findings to formulate a precise diagnostic hypothesis, and thus request a specific genetic test in order to confirm their findings, wherever possible.

Early Onset Ataxia with Comorbid Dystonia: Clinical, Anatomical and Biological Pathway Analysis Expose Shared Pathophysiology

In degenerative adult onset ataxia (AOA), dystonic comorbidity is attributed to one disease continuum. However, in early adult onset ataxia (EOA), the prevalence and pathogenesis of dystonic comorbidity (EOAD⁺), are still unclear. In 80 EOA-patients, we determined the EOAD⁺-prevalence in association with MRI-abnormalities. Subsequently, we explored underlying biological pathways by genetic network and functional enrichment analysis. We checked pathway-outcomes in specific EOAD⁺-genotypes by comparing results with non-specifically (in-silico-determined) shared genes in up-to-date EOA, AOA and dystonia gene panels (that could concurrently cause ataxia and dystonia). In the majority (65%) of EOA-patients, mild EOAD⁺-features concurred with extra-cerebellar MRI abnormalities (at pons and/or basal-ganglia and/or thalamus (p = 0.001)). Genetic network and functional enrichment analysis in EOAD⁺-genotypes indicated an association with organelle- and cellular-component organization (important for energy production and signal transduction). In non-specifically, in-silico-determined shared EOA, AOA and dystonia genes, pathways were enriched for Krebs-cycle and fatty acid/lipid-metabolic processes. In frequently occurring EOAD⁺-phenotypes, clinical, anatomical and biological pathway analyses reveal shared pathophysiology between ataxia and dystonia, associated with cellular energy metabolism and network signal transduction. Insight in the underlying pathophysiology of heterogeneous EOAD⁺-phenotype-genotype relationships supports the rationale for testing with complete, up-to-date movement disorder gene lists, instead of single EOA gene-panels.

ACR Appropriateness Criteria® Ataxia

Ataxia can result from an abnormality in the cerebellum, spinal cord, peripheral nerves, and/or vestibular system. Pathology involving the brain, such as infarct or hydrocephalus, can also present with ataxia as part of the symptom constitution, or result in symptoms that mimic ataxia. Clinical evaluation by history and careful neurological examination is important to help with lesion localization, and helps determine where imaging should be focused. In the setting of trauma with the area of suspicion in the brain, a head CT without intravenous contrast is the preferred initial imaging choice. If vascular injury is suspected, CTA of the neck can be helpful. When the area of suspicion is in the spine, CT or MRI of the spine can be considered to assess for bony or soft-tissue injury, respectively. In the setting of ataxia unrelated to recent trauma, MRI is the preferred imaging modality, tailored to assess the brain or spine depending on the area of suspected pathology. The use of intravenous contrast is generally helpful. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Main inherited neurodegenerative cerebellar ataxias, how to recognize them using magnetic resonance imaging?

Ataxia is a neurodegenerative disease resulting from brainstem, cerebellar, and/or spinocerebellar tracts impairments. Symptoms onset could vary widely from childhood to late-adulthood. Autosomal cerebellar ataxias are considered as one of the most complex group in neurogenetics. In addition to their genetic heterogeneity, there is an important phenotypic variability in the expression of cerebellar impairment, complicating the genetic mutation research. A pattern recognition approach using brain MRI measures of atrophy, hyperintensities and iron-induced hypointensity of the dentate nuclei, could be therefore helpful in guiding genetic research. This review will discuss a pattern recognition approach that, associated with the age at disease onset, and clinical manifestations, may help neuroradiologists differentiate the most frequent profiles of ataxia.

Childhood hereditary ataxias: experience from a tertiary referral university hospital in Turkey

Hereditary ataxias are a group of genetic disorders that are progressive and heterogeneous. The purpose of this study was to develop a practical and time-efficient approach to diagnosing childhood hereditary ataxias by analyzing characteristics and final diagnosis at a tertiary referral clinic for pediatric neurology. 196 patients admitted to the pediatric neurology department were included. The medical records were examined for demographic features, neurological, laboratory, electrophysiological, cranial imaging, and pathological findings, and for genetic studies. Patients were divided into two groups based on whether a final diagnosis was made. The undiagnosed and diagnosed groups consisted of 157 (81.1%) and 39 (19.9%) patients, respectively. The two groups differed in terms of levels of history of consanguineous marriage and mental and motor development before diagnosis, absence of deep tendon reflexes, and the presence of polyneuropathic changes detected by electromyelography (EMG), abnormal visual evoked potentials (VEPs), electroretinography (ERG), and muscle biopsy. To the best of our knowledge, this is the first study involving a large spectrum of diseases related to autosomal recessive ataxias in childhood in Turkey. One out of five patients with hereditary childhood ataxias can be diagnosed with clinical and laboratory and electrodiagnostic examination, especially with the help of imaging facilities, while genetic analysis is not possible for every child. Cranial magnetic resonance imaging followed by EMG provides the most important clues for the diagnosis of hereditary childhood ataxias.

Imaging of Creutzfeldt-Jakob Disease: Imaging Patterns and Their Differential Diagnosis

Diagnosis of sporadic Creutzfeldt-Jakob disease (sCJD) remains a challenge because of the large variability of the clinical scenario, especially in its early stages, which may mimic several reversible or treatable disorders. The molecular basis of prion disease, as well as its brain propagation and the pathogenesis of the illness, have become better understood in recent decades. Several reports have listed recognizable clinical features and paraclinical tests to supplement the replicable diagnostic criteria in vivo. Nevertheless, we lack specific data about the differential diagnosis of CJD at imaging, mainly regarding those disorders evolving with similar clinical features (mimicking disorders). This review provides an update on the neuroimaging patterns of sCJD, emphasizing the relevance of magnetic resonance (MR) imaging, summarizing the clinical scenario and molecular basis of the disease, and highlighting clinical, genetic, and imaging correlations in different subtypes of prion diseases. A long list of differential diagnoses produces a comprehensive pictorial review, with the aim of enabling radiologists to identify typical and atypical patterns of sCJD. This review reinforces distinguishable imaging findings and confirms diffusion-weighted imaging (DWI) features as pivotal in the diagnostic workup of sCJD, as these findings enable radiologists to reliably recognize this rare but invariably lethal disease. A probable diagnosis is justified when expected MR imaging patterns are demonstrated and CJD-mimicking disorders are confidently ruled out. ^©RSNA, 2017.

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.

Role of neuroimaging in the diagnosis of hereditary cerebellar ataxias in childhood

Hereditary ataxias are a heterogeneous group of neurodegenerative disorders, characterized by cerebellar ataxia as the main clinical feature, and a large spectrum of neurological-associated symptoms and possible multi-organ affection. Image-based approaches to hereditary ataxias in childhood have already been proposed. The aim of this review is to yield the main reports of neuroimaging patterns and diagnostic algorithms and compare them with the results from our study of 23 young patients addressed for ataxia, with subsequent genetic or metabolic diagnosis.

Neuroimaging Findings and Repeat Neuroimaging Value in Pediatric Chronic Ataxia

BACKGROUND

Chronic ataxia, greater than two months in duration, is encountered relatively commonly in clinical pediatric neurology practise and presents with diagnostic challenges. It is caused by multiple and diverse disorders. Our aims were to describe the neuroimaging features and the value of repeat neuroimaging in pediatric chronic ataxia to ascertain their contribution to the diagnosis and management.

MATERIALS AND METHODS

A retrospective charts and neuroimaging reports review was undertaken in 177 children with chronic ataxia. Neuroimaging in 130 of 177 patients was also reviewed.

RESULTS

Nineteen patients had head computed tomography only, 103 brain magnetic resonance imaging only, and 55 had both. Abnormalities in the cerebellum or other brain regions were associated with ataxia. Neuroimaging was helpful in 73 patients with 30 disorders: It was diagnostic in 9 disorders, narrowed down the diagnostic possibilities in 14 disorders, and revealed important but non-diagnostic abnormalities, e.g. cerebellar atrophy in 7 disorders. Having a normal magnetic resonance imaging scan was mostly seen in genetic diseases or in the early course of ataxia telangiectasia. Repeat neuroimaging, performed in 108 patients, was generally helpful in monitoring disease evolution and in making a diagnosis. Neuroimaging was not directly helpful in 36 patients with 10 disorders or by definition the 55 patients with unknown disease etiology.

CONCLUSIONS

Normal or abnormal neuroimaging findings and repeat neuroimaging are very valuable in the diagnosis and management of disorders associated with pediatric chronic ataxia.

Reliability of phenotypic early-onset ataxia assessment: a pilot study

AIM

To investigate the interobserver agreement on phenotypic early-onset ataxia (EOA) assessment and to explore whether the Scale for Assessment and Rating of Ataxia (SARA) could provide a supportive marker.

METHOD

Seven movement disorder specialists provided independent phenotypic assessments of potentially ataxic motor behaviour in 40 patients (mean age 15y [range 5-34]; data derived from University Medical Center Groningen medical records 1998-2012). We determined interobserver agreement by Fleiss' kappa. Furthermore, we compared percentage SARA subscores ([subscore/total score]×100%) between 'indisputable' (primary ataxia recognition by at least six observers) and 'mixed' (ataxia recognition, unfulfilling 'indisputable' criteria) EOA phenotypes.

RESULTS

Agreement on phenotypic EOA assessment was statistically significant (p<0.001), but of moderate strength (Fleiss' kappa=0.45; 95% CI 0.38-0.51). During mild disease progression, percentage SARA gait subscores discriminated between 'indisputable' and 'mixed' EOA phenotypes. In patients with percentage SARA gait subscores >30%, primary ataxia was more frequently present than in those with subscores <30% (p=0.001).

INTERPRETATION

Among movement-disorder professionals from different disciplines, interobserver agreement on phenotypic EOA recognition is of limited strength. SARA gait subscores can provide a supportive discriminative marker between EOA phenotypes. Hopefully, future phenotypic insight will contribute to the inclusion of uniform, high-quality data in international EOA databases.

Brain imaging and genetic risk in the pediatric population, part 1: inherited metabolic diseases

In this article, the genotype-MR phenotype correlation of the most common or clinically important inherited metabolic diseases (IMD) in the pediatric population is reviewed. A nonsystematic search of the PubMed/Medline database of relevant studies about "genotype-phenotype correlation" in IMD was performed. Some MR phenotypes related to specific gene mutations were found, such as bilateral hypertrophy of inferior olives in patients harboring POLG and SURF1 mutations, and central lesions in the cervical spinal cord in patients with nonketotic hyperglycinemia harboring GLRX5 gene mutation.

A case of McLeod phenotype of neuroacanthocytosis brain MR features and literature review

Huntington's disease and neuroacanthocytosis may present similar clinical and MRI features. It is important to differentiate these findings since treatment and prognosis vary vastly between them. The aim of this article is to familiarize radiologists with the differentiating features of Huntington's disease and various diseases comprising neuroacanthocytosis. A 40-year-old Indian man with extrapyramidal symptoms was referred for MRI. The clinical diagnosis was Huntington's disease, but there were a few atypical clinical features such as a history of biting the tongue, tics, marked hyporeflexia and lower limb muscle wasting. MR showed atrophy of the caudate nucleus and putamen with iron deposition in the basal ganglia, which can be seen in Huntington's disease and in neuroacanthocytosis. An increased blood acanthocyte level was subsequently confirmed. Further work-up revealed increased serum creatine phosphokinase levels, normal serum lipoprotein levels and depressed K cell antigen activity on serological studies, confirming the diagnosis of McLeod syndrome. McLeod syndrome is one of the distinct phenotypes of neuroacanthocytosis. Neuroacanthocytosis is a group of disorders with increased serum acanthocyte counts and neurological involvement. Various causes of neuroacanthocytosis are discussed. It is important to consider the possibility of neuroacanthocytosis when features typical of Huntington's disease are encountered on imaging.