Cerebrotendinous Xanthomatosis: A practice review of pathophysiology, diagnosis, and treatment

Cerebrotendinous Xanthomatosis represents a rare and underdiagnosed inherited neurometabolic disorder due to homozygous or compound heterozygous variants involving the CYP27A1 gene. This bile acid metabolism disorder represents a key potentially treatable neurogenetic condition due to the wide spectrum of neurological presentations in which it most commonly occurs. Cerebellar ataxia, peripheral neuropathy, spastic paraparesis, epilepsy, parkinsonism, cognitive decline, intellectual disability, and neuropsychiatric disturbances represent some of the most common neurological signs observed in this condition. Despite representing key features to increase diagnostic index suspicion, multisystemic involvement does not represent an obligatory feature and can also be under evaluated during diagnostic work-up. Chenodeoxycholic acid represents a well-known successful therapy for this inherited metabolic disease, however its unavailability in several contexts, high costs and common use in patients at late stages of disease course limit more favorable neurological outcomes for most individuals. This review article aims to discuss and highlight the most recent and updated knowledge regarding clinical, pathophysiological, neuroimaging, genetic and therapeutic aspects related to Cerebrotendinous Xanthomatosis.

Copy number variations in SPAST and ATL1 are rare among Brazilians

Copy number variations (CNV) may represent a significant proportion of SPG4 and SPG3A diagnosis, the most frequent autosomal dominant subtypes of hereditary spastic paraplegias (HSP). We aimed to assess the frequency of CNVs in SPAST and ATL1 and to update the molecular epidemiology of HSP families in southern Brazil. A cohort study that included 95 Brazilian index cases with clinical suspicion of HSP was conducted between April 2011 and September 2022. Multiplex Ligation Dependent Probe Amplification (MLPA) was performed in 41 cases without defined diagnosis by different massive parallel sequencing techniques (MPS). Diagnosis was obtained in 57/95 (60%) index cases, 15/57 (26.3%) being SPG4. Most frequent autosomal recessive HSP subtypes were SPG7 followed by SPG11, SPG76 and cerebrotendinous xanthomatosis. No CNVs in SPAST and ATL1 were found. Copy number variations are rare among SPG4 and SPG3A families in Brazil. Considering the possibility of CNVs detection by specific algorithms with MPS data, we consider that this is likely the most cost-effective approach to investigate CNVs in these genes in low-risk populations, with MLPA being reserved as an orthogonal confirmatory test.

Diagnostic reasoning in neurogenetics: a general approach

Establishing the definitive diagnosis of a neurogenetic disease is usually a complex task. However, like any type of clinical diagnostic reasoning, an organized process of development and consideration of diagnostic hypotheses may guide neurologists and medical geneticists to solve this difficult task. The aim of the present review is to propose a general method for diagnostic reasoning in neurogenetics, with the definition of the main neurological syndrome and its associated topographical diagnosis, followed by the identification of major and secondary neurological syndromes, extraneurological findings, and inheritance pattern. We also discuss general rules and knowledge requirements of the ordering physician to request genetic testing and information on how to interpret genetic variants in a genetic report. By guiding the requests for genetic testing according to an organized model of diagnostic reasoning and with the availability of specific treatments, clinicians may find greater resoluteness and efficacy in the diagnostic investigation, shortening the struggle of patients for a definitive diagnosis.

Evoked potentials as biomarkers of hereditary spastic paraplegias: A case-control study

Introduction

The Hereditary Spastic Paraplegias (HSP) are a group of genetic diseases that lead to slow deterioration of locomotion. Clinical scales seem to have low sensitivity in detecting disease progression, making the search for additional biomarkers a paramount task. This study aims to evaluate the role of evoked potentials (EPs) as disease biomarkers of HSPs.

Methods

A single center cross-sectional case-control study was performed, in which 18 individuals with genetic diagnosis of HSP and 21 healthy controls were evaluated. Motor evoked potentials (MEP) obtained with transcranial magnetic stimulation and somatosensory evoked potentials (SSEP) were performed in lower (LL) and upper limbs (UL).

Results

Central motor conduction time in lower limbs (CMCT-LL) was prolonged in HSP subjects, with marked reductions in MEP-LL amplitudes when compared to the control group (p<0.001 for both comparisons). CMCT-UL was 3.59ms (95% CI: 0.73 to 6.46; p = 0.015) prolonged and MEP-UL amplitudes were reduced (p = 0.008) in the HSP group. SSEP-LL latencies were prolonged in HSP subjects when compared to controls (p<0.001), with no statistically significant differences for upper limbs (p = 0.147). SSEP-UL and SSEP-LL latencies presented moderate to strong correlations with age at onset (Rho = 0.613, p = 0.012) and disease duration (Rho = 0.835, p<0.001), respectively. Similar results were obtained for the SPG4 subgroups of patients.

Conclusion

Motor and somatosensory evoked potentials can adequately differentiate HSP individuals from controls. MEP were severely affected in HSP subjects and SSEP-LL latencies were prolonged, with longer latencies being related to more severe disease. Future longitudinal studies should address if SSEP is a sensitive disease progression biomarker for HSP.

Friedreich Ataxia: Diagnostic Yield and Minimal Frequency in South Brazil

Friedreich ataxia (FRDA) is an autosomal recessive disorder due to mutations in the FXN gene. FRDA is characterized by the classical triad of ataxia, absent reflexes, and Babinski sign, but atypical presentations might also occur. Our aims were to describe the proportion of FRDA diagnoses in suspected families living in Rio Grande do Sul, South Brazil, and to estimate a minimum frequency of symptomatic subjects. Subjects that were evaluated by molecular analysis for FRDA at the Hospital de Clínicas de Porto Alegre were identified in our files. Patients' clinical manifestation and phenotypes were described and compared. The number of FRDA subjects alive in the last 5 years was determined. One hundred fifty-six index cases (families) were submitted to evaluation of GAA repeats at FXN since 1997: 27 were confirmed as FRDA patients. Therefore, the diagnostic yield was 17.3%. Proportion of classical, late onset, and retained reflexes subphenotypes were similar to those described by other studies. A minimum prevalence was estimated as 0.20:100.000 inhabitants. In conclusion, we verified that this FRDA population displayed the usual clinical characteristics, but with a lower period prevalence than those obtained in populations from Europe.

Autosomal recessive spastic ataxia of Charlevoix-Saguenay: a family report from South Brazil

Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is an early-onset, neurodegenerative disorder caused by mutations in SACS, firstly reported in Quebec, Canada. The disorder is typically characterized by childhood onset ataxia, spasticity, neuropathy and retinal hypermyelination. The clinical picture of patients born outside Quebec, however, is often atypical. In the present article, the authors describe clinical and neuroradiological findings that raised the suspicion of an ARSACS diagnosis in two female cousins with Germanic background from Rio Grande do Sul, Brazil. We present a review on the neuroimaging, ophthalmologic and neurophysiologic clues for ARSACS diagnosis. The early-onset, slowly progressive, spastic-ataxia phenotype of reported patients was similar to ARSACS patients from Quebec. The SACS sequencing revealed the novel homozygous c.5150_5151insA frameshift mutation confirming the ARSACS diagnosis. ARSACS is a frequent cause of early onset ataxia/spastic-ataxia worldwide, with unknown frequency in Brazil.

PRES with asymptomatic spinal cord involvement. Is this scenario more common than we know?

INTRODUCTION

Posterior reversible encephalopathy syndrome (PRES) is an entity characterized by neurologic symptoms such as headaches, altered mental status, seizures and visual changes, and it is associated with white matter vasogenic edema predominantly affecting the posterior occipital and parietal lobes of the brain.

CASE REPORT

A 19-year-old patient developed PRES after the use of chemotherapy for a testicular teratocarcinoma and after the development of a blood pressure elevation.

DISCUSSION

Few cases described the involvement of the spinal cord in this syndrome. In the majority of these cases, the spinal cord involvement was asymptomatic or with few symptoms of spinal cord disease.