Prevalence of hereditary ataxia and spastic paraplegia in southeast Norway: a population-based study

AP2A2 mutation and defective endocytosis in a Malian family with hereditary spastic paraplegia

Hereditary spastic paraplegia (HSP) comprises a large group of neurogenetic disorders characterized by progressive lower extremity spasticity. Neurological evaluation and genetic testing were completed in a Malian family with early-onset HSP. Three children with unaffected consanguineous parents presented with symptoms consistent with childhood-onset complicated HSP. Neurological evaluation found lower limb weakness, spasticity, dysarthria, seizures, and intellectual disability. Brain MRI showed corpus callosum thinning with cortical and spinal cord atrophy, and an EEG detected slow background in the index patient. Whole exome sequencing identified a homozygous missense variant in the adaptor protein (AP) complex 2 alpha-2 subunit (AP2A2) gene. Western blot analysis showed reduced levels of AP2A2 in patient-iPSC derived neuronal cells. Endocytosis of transferrin receptor (TfR) was decreased in patient-derived neurons. In addition, we observed increased axon initial segment length in patient-derived neurons. Xenopus tropicalis tadpoles with ap2a2 knockout showed cerebral edema and progressive seizures. Immunoprecipitation of the mutant human AP-2-appendage alpha-C construct showed defective binding to accessory proteins. We report AP2A2 as a novel genetic entity associated with HSP and provide functional data in patient-derived neuron cells and a frog model. These findings expand our understanding of the mechanism of HSP and improve the genetic diagnosis of this condition.

Genotype-specific spinal cord damage in spinocerebellar ataxias: an ENIGMA-Ataxia study

BACKGROUND

Spinal cord damage is a feature of many spinocerebellar ataxias (SCAs), but well-powered in vivo studies are lacking and links with disease severity and progression remain unclear. Here we characterise cervical spinal cord morphometric abnormalities in SCA1, SCA2, SCA3 and SCA6 using a large multisite MRI dataset.

METHODS

Upper spinal cord (vertebrae C1-C4) cross-sectional area (CSA) and eccentricity (flattening) were assessed using MRI data from nine sites within the ENIGMA-Ataxia consortium, including 364 people with ataxic SCA, 56 individuals with preataxic SCA and 394 nonataxic controls. Correlations and subgroup analyses within the SCA cohorts were undertaken based on disease duration and ataxia severity.

RESULTS

Individuals in the ataxic stage of SCA1, SCA2 and SCA3, relative to non-ataxic controls, had significantly reduced CSA and increased eccentricity at all examined levels. CSA showed large effect sizes (d>2.0) and correlated with ataxia severity (r<-0.43) and disease duration (r<-0.21). Eccentricity correlated only with ataxia severity in SCA2 (r=0.28). No significant spinal cord differences were evident in SCA6. In preataxic individuals, CSA was significantly reduced in SCA2 (d=1.6) and SCA3 (d=1.7), and the SCA2 group also showed increased eccentricity (d=1.1) relative to nonataxic controls. Subgroup analyses confirmed that CSA and eccentricity are abnormal in early disease stages in SCA1, SCA2 and SCA3. CSA declined with disease progression in all, whereas eccentricity progressed only in SCA2.

CONCLUSIONS

Spinal cord abnormalities are an early and progressive feature of SCA1, SCA2 and SCA3, but not SCA6, which can be captured using quantitative MRI.

Identification of novel variations in three cases with rare inherited neuromuscular disorder

Inherited neuromuscular disorder (IND) is a broad-spectrum, clinically diverse group of diseases that are caused due to defects in the neurosystem, muscles and related tissue. Since IND may originate from mutations in hundreds of different genes, the resulting heterogeneity of IND is a great challenge for accurate diagnosis and subsequent management. Three pediatric cases with IND were enrolled in the present study and subjected to a thorough clinical examination. Next, a genetic investigation was conducted using whole-exome sequencing (WES). The suspected variants were validated through Sanger sequencing or quantitative fluorescence PCR assay. A new missense variant of the Spastin (SPAST) gene was found and analyzed at the structural level using molecular dynamics (MD) simulations. All three cases presented with respective specific clinical manifestations, which reflected the diversity of IND. WES detected the diagnostic variants in all 3 cases: A compound variation comprising collagen type VI α3 chain (COL6A3) (NM_004369; exon19):c.6322G>T(p.E1208*) and a one-copy loss of COL6A3:exon19 in Case 1, which are being reported for the first time; a de novo SPAST (NM_014946; exon8):c.1166C>A(p.T389K) variant in Case 2; and a de novo Duchenne muscular dystrophy (NM_004006; exon11):c.1150-17_1160delACTTCCTTCTTTGTCAGGGGTACATGATinsC variant in Case 3. The structural and MD analyses revealed that the detected novel SPAST: c.1166C>A(p.T389K) variant mainly altered the intramolecular hydrogen bonding status and the protein segment's secondary structure. In conclusion, the present study expanded the IND mutation spectrum. The study not only detailed the precise diagnoses of these cases but also furnished substantial grounds for informed consultations. The approach involving the genetic evaluation strategy using WES for variation screening followed by validation using appropriate methods is beneficial due to the considerable heterogeneity of IND.

Epidemiology of Spinocerebellar Ataxias in Europe

Spinocerebellar ataxias (SCAs) are a heterogenous group of rare neurodegenerative conditions sharing an autosomal dominant pattern of inheritance. More than 40 SCAs have been genetically determined. However, a systematic review of SCA epidemiology in Europe is still missing. Here we performed a narrative review of the literature on the epidemiology of the most common SCAs in Europe. PubMed, Embase, and MEDLINE were searched from inception until 1 April 2023. All English peer-reviewed articles published were considered and then filtered by abstract examination and subsequently by full text reading. A total of 917 original articles were retrieved. According to the inclusion criteria and after reviewing references for useful papers, a total of 35 articles were included in the review. Overall, SCA3 is the most frequent spinocerebellar ataxia in Europe. Its frequency is strikingly higher in Portugal, followed by Germany, France, and Netherlands. None or few cases were described in Italy, Russia, Poland, Serbia, Finland, and Norway. SCA1 and SCA2 globally displayed similar frequencies, and are more prevalent in Italy, United Kingdom, Poland, Serbia, and France.

KCNJ3 is a novel candidate gene for autosomal dominant pure hereditary spastic paraplegia identified using whole genome sequencing

Hereditary spastic paraplegia (HSP) is a group of familial diseases characterized by progressive corticospinal tract degeneration. Clinically, patients present with lower-limb spasticity and weakness. To date, more than 80 genetic HSP types have been identified. Despite advances in molecular genetics, novel HSP gene discoveries are ongoing, with a low genetic diagnostic yield. In this study, we aimed to determine pathogenic variants in a family with HSP, which was not diagnosed through conventional genetic testing. We clinically characterized a large family and conducted whole genome sequencing (WGS) analysis of four affected and three unaffected individuals in the family to identify the genetic cause of HSP. This family had autosomal dominant pure (uncomplicated) late childhood-onset HSP. The patients' symptoms accelerated between the ages of 20 and 30. Brain magnetic resonance images typically showed white matter changes, a thin corpus callosum, and cerebellar atrophy. We identified a heterozygous missense variant, KCNJ3 c.1297T>G (p.Leu433Val), through WGS and family genetic analysis, confirmed by Sanger sequencing. We suggest that the identification of KCNJ3 c.1297T>G (p.Leu433Val) constitutes the discovery of a potential novel gene responsible for HSP in this family. This is the first study to report the possible role of a KCNJ3 variant in HSP pathogenesis. Our findings further expand the phenotypic and genotypic spectrum of HSP.

Genetic aspects of ataxias in a cohort of Turkish patients

INTRODUCTION

Ataxia is one of the clinical findings of the movement disorder disease group. Although there are many underlying etiological reasons, genetic etiology has an increasing significance thanks to the recently developing technology. The aim of this study is to present the variants detected in WES analysis excluding non-genetic causes, in patients with ataxia.

METHODS

Thirty-six patients who were referred to us with findings of ataxia and diagnosed through WES or other molecular genetic analysis methods were included in our study. At the same time, information such as the onset time of the complaints, consanguinity status between parents, and the presence of relatives with similar symptoms were evaluated. If available, the patient's biochemical and radiological test results were presented.

RESULTS

Thirty-six patients were diagnosed through WES or CES. The rate of detected autosomal recessive inheritance disease was 80.5%, while that of autosomal dominant inheritance disease was 19.5%. Abnormal cerebellum was detected on brain MRI images in 26 patients, while polyneuropathy was detected on EMG in eleven of them. While the majority of the patients were compatible with similar cases reported in the literature, five patients had different/additional features (variants in MCM3AP, AGTPBP1, GDAP2, and SH3TC2 genes).

CONCLUSIONS

The diagnosis of ataxia patients with unknown etiology is made possible thanks to these clues. Consideration of a genetic approach is recommended in patients with ataxia of unknown etiology.

A Novel SPAST Variant Associated with Isolated Spastic Paraplegia

Genetic variants in SPAST are the most common cause of hereditary spastic paraplegia (HSP), entitled spastic paraplegia type 4 (SPG4). Inheritance is autosomal dominant, and age of onset can vary from childhood to adulthood. Pathogenic SPAST variants are often observed in isolated cases, likely due to reduced penetrance and clinical variability. We report an isolated case of SPG4 associated with a novel likely pathogenic variant in SPAST. A 38-year-old woman presented with an eight-year history of progressive difficulty walking. Neurological examination revealed spastic paraparesis in the absence of upper motor neuron dysfunction, sensory deficits, or intellectual disability. Magnetic resonance imaging (MRI) of the brain and spinal cord was normal. No family members had similar complaints. Genetic analysis revealed a novel heterozygous sequence variant in SPAST, c.1751A > G p.(Asp584Gly) (NM_014946.4). The affected amino acid is highly conserved among orthologue and paralogue species. Four other nucleotide substitutions predicted to affect the same amino acid, a "hot spot", have been reported previously in adult-onset HSP. This report describes a novel SPAST variant in a female with HSP without a known family history of the disorder.

Cohort analysis of novel SPAST variants in SPG4 patients and implementation of in vitro and in vivo studies to identify the pathogenic mechanism caused by splicing mutations

Introduction

Pure hereditary spastic paraplegia (SPG) type 4 (SPG4) is caused by mutations of SPAST gene. This study aimed to analyze SPAST variants in SPG4 patients to highlight the occurrence of splicing mutations and combine functional studies to assess the relevance of these variants in the molecular mechanisms of the disease.

Methods

We performed an NGS panel in 105 patients, in silico analysis for splicing mutations, and in vitro minigene assay.

Results and discussion

The NGS panel was applied to screen 105 patients carrying a clinical phenotype corresponding to upper motor neuron syndrome (UMNS), selectively affecting motor control of lower limbs. Pathogenic mutations in SPAST were identified in 12 patients (11.42%), 5 missense, 3 frameshift, and 4 splicing variants. Then, we focused on the patients carrying splicing variants using a combined approach of in silico and in vitro analysis through minigene assay and RNA, if available. For two splicing variants (i.e., c.1245+1G>A and c.1414-2A>T), functional assays confirm the types of molecular alterations suggested by the in silico analysis (loss of exon 9 and exon 12). In contrast, the splicing variant c.1005-1delG differed from what was predicted (skipping exon 7), and the functional study indicates the loss of frame and formation of a premature stop codon. The present study evidenced the high splice variants in SPG4 patients and indicated the relevance of functional assays added to in silico analysis to decipher the pathogenic mechanism.

Hereditary spastic paraplegia in Mali: epidemiological and clinical features

BACKGROUND AND PURPOSE

Hereditary spastic paraplegia (HSP) is a group of neurodegenerative diseases divided into pure and complex forms, with spasticity in lower limbs only, or associated with other neurologic and non-neurologic manifestations, respectively. Although widely reported in other populations, very little data exist in sub-Saharan Africa.

METHODS

Patients with neurodegenerative features were evaluated over a 19-month period at the Department of Neurology, Teaching Hospital of Point "G", Bamako, Mali. The diagnosis of HSP was considered based on family history and the absence of other known non-genetic causes. Genetic analysis including candidate gene and whole exome sequencing was performed and variant pathogenicity was tested using prediction tools and ACMG guidelines.

RESULTS

Of the 170 families with hereditary neurological disorders enrolled, 16 had features consistent with HSP, a frequency of 9%. The average age of onset was 14.7 years with 46% starting before age 6. The male/female ratio was 2.6:1. Complex forms were seen in 75% of cases, and pure forms in 25%. Pyramidal findings were present in all patients. Associated features included mental retardation, peripheral neuropathy, epilepsy, oculomotor impairment and urinary urgency. Most patients were treated with a muscle relaxant and physical therapy, and restorative surgery was done in one. Genetic testing identified novel variants in three families (19%).

CONCLUSION

This study confirms the clinical variability of HSPs and adds African data to the current literature.

Parkinsonism in complex neurogenetic disorders: lessons from hereditary dementias, adult-onset ataxias and spastic paraplegias

Parkinsonism is a syndrome characterized by bradykinesia in combination with either rest tremor, rigidity, or both. These features are the cardinal manifestations of Parkinson's disease, the most common cause of parkinsonism, and atypical parkinsonian disorders. However, parkinsonism can be a manifestation of complex neurological and neurodegenerative genetically determined disorders, which have a vast and heterogeneous motor and non-motor phenotypic features. Hereditary dementias, adult-onset ataxias and spastic paraplegias represent only few of this vast group of neurogenetic diseases. This review will provide an overview of parkinsonism's clinical features within adult-onset neurogenetic diseases which a neurologist could face with. Understanding parkinsonism and its characteristics in the context of the aforementioned neurological conditions may provide insights into pathophysiological mechanisms and have important clinical implications, including diagnostic and therapeutic aspects.

Outcome Measures and Biomarkers for Clinical Trials in Hereditary Spastic Paraplegia: A Scoping Review

Hereditary spastic paraplegia (HSP) is characterized by progressive lower limb spasticity. There is no disease-modifying treatment currently available. Therefore, standardized, validated outcome measures to facilitate clinical trials are urgently needed. We performed a scoping review of outcome measures and biomarkers for HSP to provide recommendations for future studies and identify areas for further research. We searched Embase, Medline, Scopus, Web of Science, and the Central Cochrane database. Seventy studies met the inclusion criteria, and eighty-three outcome measures were identified. The Spastic Paraplegia Rating Scale (SPRS) was the most widely used (27 studies), followed by the modified Ashworth Scale (18 studies) and magnetic resonance imaging (17 studies). Patient-reported outcome measures (PROMs) were infrequently used to assess treatment outcomes (28% of interventional studies). Diffusion tensor imaging, gait analysis and neurofilament light chain levels were the most promising biomarkers in terms of being able to differentiate patients from controls and correlate with clinical disease severity. Overall, we found variability and inconsistencies in use of outcome measures with a paucity of longitudinal data. We highlight the need for (1) a standardized set of core outcome measures, (2) validation of existing biomarkers, and (3) inclusion of PROMs in HSP clinical trials.

Plasma Neurofilament Light Chain Is Elevated in Adaptor Protein Complex 4-Related Hereditary Spastic Paraplegia

BACKGROUND

Adaptor protein complex 4-associated hereditary spastic paraplegia (AP-4-HSP) is caused by pathogenic biallelic variants in AP4B1, AP4M1, AP4E1, and AP4S1.

OBJECTIVE

The aim was to explore blood markers of neuroaxonal damage in AP-4-HSP.

METHODS

Plasma neurofilament light chain (pNfL) and glial fibrillary acidic protein (GFAP) levels were measured in samples from patients and age- and sex-matched controls (NfL: n = 46 vs. n = 46; GFAP: n = 14 vs. n = 21) using single-molecule array assays. Patients' phenotypes were systematically assessed using the AP-4-HSP natural history study questionnaires, the Spastic Paraplegia Rating Scale, and the SPATAX disability score.

RESULTS

pNfL levels increased in AP-4-HSP patients, allowing differentiation from controls (Mann-Whitney U test: P = 3.0e-10; area under the curve = 0.87 with a 95% confidence interval of 0.80-0.94). Phenotypic cluster analyses revealed a subgroup of individuals with severe generalized-onset seizures and developmental stagnation, who showed differentially higher pNfL levels (Mann-Whitney U test between two identified clusters: P = 2.5e-6). Plasma GFAP levels were unchanged in patients with AP-4-HSP.

CONCLUSIONS

pNfL is a potential disease marker in AP-4-HSP and can help differentiate between phenotypic subgroups. © 2023 International Parkinson and Movement Disorder Society.

Spastic paraplegia is the main manifestation of a spinocerebellar ataxia type 8 lineage in China: a case report and review of literature

The diagnosis and treatment of cerebellar atrophy remain challenging owing to its nonspecific symptoms and laboratory indicators. Three patients with spinocerebellar ataxia type 8 caused by ATXN8OS were found among the 16 people in the studied family. The clinical manifestations of the patients included progressive spastic paraplegia of the lower extremities, mild ataxia, mild cognitive impairment, and cerebellar atrophy. After administering antispasmodic rehabilitation treatment, using oral drugs, botulinum toxin injection, baclofen pump, and other systems in our hospital, the patients' lower extremity spasticity was significantly relieved. To our knowledge, till date, this is the first domestic report of spinocerebellar ataxia type 8 affecting a family, caused by ATXN8OS with spasticity onset in early childhood. Manifestations of the disease included spastic dyskinesia (in early disease stages) and cerebellar atrophy. Through systematic rehabilitation, the daily life of patients with this movement disorder was improved. This case report adds to the literature on spinocerebellar ataxia type 8 by summarizing its features.

Clinical and genetic spectrum of hereditary spastic paraplegia in Chinese children

AIM

To explore the clinical and genetic spectrum of hereditary spastic paraplegia (HSP) in Chinese children.

METHOD

This retrospective study was conducted between January 2014 and October 2021 in children clinically diagnosed with either pure HSP (pHSP) or complex HSP (cHSP).

RESULTS

We investigated 45 children (32 males, 13 females; mean age [SD] at symptom onset 4 years [7 months]). clinically diagnosed with HSP and identified genetic causes in 35 patients. Most patients with autosomal dominant HSP had pHSP (16/18), whereas most patients with autosomal recessive HSP tended to have cHSP (14/16). SPG11 was the most common autosomal recessive subtype, followed by FA2H/SPG35, whereas SPAST/SPG4 was the most frequent cause of autosomal dominant HSP. Two patients with CPT1C mutations presented with a complex phenotype. Meanwhile, 10 patients were found to have likely pathogenic variants/variants of uncertain clinical significance in six genes related to HSP.

INTERPRETATION

SPG11 and SPG4 were the most frequent subtypes in Chinese children with autosomal recessive HSP and autosomal dominant HSP. However, the prevalence of SPG4 was much lower than that in adults, which might be explained by the late onset of the disease. On the other hand, FA2H/SPG35 was common in our cohort, while it contributed to only a small proportion of adult cases, which might be explained by its rapid progression and early death in some patients. We also expanded the genetic and clinical spectra of SPG73.

Toward the Definition of Patient-Reported Outcome Measurements in Hereditary Spastic Paraplegia

Background and Objectives

Hereditary spastic paraplegias (HSPs) are a heterogeneous group of rare neurodegenerative diseases, characterized by a progressive spastic paraparesis. Currently, there is a HSP-specific clinician-reported outcome measure (CROM) called Spastic Paraplegia Rating Scale (SPRS). There are, however, no specific patient-reported outcome measures (PROMs) for HSP. In the present cohort study, we prospectively follow up a well-examined Austrian HSP cohort using validated rating scales and compared PROM with disease-specific and non-disease-specific CROM.

Methods

Patients were recruited and followed up at the Center for Rare Movement Disorders, Innsbruck, Austria. CROM included the SPRS, Scale for the Assessment and Rating of Ataxia (SARA), Barthel Index (BI), and Mini-Mental State Examination (MMSE). PROM included the EQ-5D questionnaire and the Patient Health Questionnaire 9 (PHQ-9). Standardized response means (SRMs) were calculated for all scales at follow-up (FU) after 1 year.

Results

A total of 55 patients (36 males) with HSP were included in the study. FU was performed for 30 patients (21 males). Apart from females reporting more problems in the EQ-5D domain of anxiety and depression (p = 0.008), other clinician-reported outcomes (CROs) or patient-reported outcomes (PROs) did not differ significantly across sex. SPRS showed significant correlations with SARA (p < 0.001), mainly driven by the gait item, as well as the BI. Although SPRS did not correlate with EQ-5D visual analogue scale and PHQ-9 scores, several EQ-5D domains correlated significantly with SPRS. At FU, SPRS showed the highest responsiveness (SRM 1.11), followed by SARA (SRM 0.47). Neither MMSE nor PRO significantly increased at FU.

Discussion

In this study, we present an Austrian cohort of patients with HSP and a prospective study evaluating correlations of CRO and PRO as well as their progression. Demographics from our cohort are comparable with several other European cohort studies. Our data highlight the capabilities of the SPRS to show clinical progression and warrant consideration of ataxia rating scales such as SARA in HSP cohorts. We also show that the generic PROMs are not suitable to detect change in HSP, and thus, we propose to create a disease-specific PROM fully depicting the effect of HSP on the patients' lives.

ConvNets for automatic detection of polyglutamine SCAs from brain MRIs: state of the art applications

Polyglutamine spinocerebellar ataxias (polyQ SCAs) are a group of neurodegenerative diseases, clinically and genetically heterogeneous, characterized by loss of balance and motor coordination due to dysfunction of the cerebellum and its connections. The diagnosis of each type of polyQ SCA, alongside with genetic tests, includes medical images analysis, and its automation may help specialists to distinguish between each type. Convolutional neural networks (ConvNets or CNNs) have been recently used for medical image processing, with outstanding results. In this work, we present the main clinical and imaging features of polyglutamine SCAs, and the basics of CNNs. Finally, we review studies that have used this approach to automatically process brain medical images and may be applied to SCAs detection. We conclude by discussing the possible limitations and opportunities of using ConvNets for SCAs diagnose in the future.

Gait classification in a population of adults with hereditary spastic paresis

BACKGROUND

Classification of gait in adults with hereditary spastic paresis is limited. Our aim was to use a previously established system to classify gait.

METHODS

Forty-nine participants were retrospectively recruited and grouped into existing classifications based on sagittal plane knee joint kinematic data extracted from a 3D analysis. Waveform analysis was used to compare the grouped data to determine if and where differences in the subjective classifications appeared.

FINDINGS

Classification of gait patterns in adults with hereditary spastic paresis is successful. Differences between groups in line with the classification system were confirmed by statistical analysis. Crouch gait is illustrated by a flexed knee throughout stance phase. Recurvatum gait is dominated by knee hyperextension in mid-late stance. Stiff-knee gait demonstrates limited knee range of motion in stance and jump-knee gait is characterised by less knee flexion in early and mid-stance phase than all groups. Sagittal plane hip and ankle kinematics compliment group differences at the knee joint. The jump-knee group is more flexed at the hip than all groups during loading response phase and mid-stance; and the recurvatum group is more extended at the hip than the crouch, jump-knee, and stiff-knee groups during mid and late-stance phase. There is less ankle dorsiflexion throughout stance phase in the recurvatum group than in all other groups.

INTERPRETATION

Sagittal plane knee joint kinematic data can be subjectively used to classify gait features in adults with hereditary spastic paresis. Novel analysis show hip and ankle sagittal plane kinematics can be used to further assist classification.

Childhood-onset hereditary spastic paraplegia and its treatable mimics

Early-onset forms of hereditary spastic paraplegia and inborn errors of metabolism that present with spastic diplegia are among the most common "mimics" of cerebral palsy. Early detection of these heterogenous genetic disorders can inform genetic counseling, anticipatory guidance, and improve outcomes, particularly where specific treatments exist. The diagnosis relies on clinical pattern recognition, biochemical testing, neuroimaging, and increasingly next-generation sequencing-based molecular testing. In this short review, we summarize the clinical and molecular understanding of: 1) childhood-onset and complex forms of hereditary spastic paraplegia (SPG5, SPG7, SPG11, SPG15, SPG35, SPG47, SPG48, SPG50, SPG51, SPG52) and, 2) the most common inborn errors of metabolism that present with phenotypes that resemble hereditary spastic paraplegia.

A systematic review of disease prevalence, health-related quality of life, and economic outcomes associated with Friedreich's Ataxia

INTRODUCTION

Friedreich ataxia (FA) is a rare, inherited neuromuscular disease characterized by an early onset and progressive limb and gait ataxia. Currently, there are no approved treatments for FA. It is important to understand the burden of FA, including its extent and the most salient elements. The objective of this study is therefore to systematically review the literature regarding the aspects of prevalence, health-related quality of life (HRQoL), and economic outcomes that are associated with FA, and to subsequently identify relevant knowledge gaps.

METHODS

Three systematic literature reviews were conducted to assess publications regarding FA prevalence, HRQoL, and economic outcomes. Search strategies were implemented in MEDLINE (Ovid) and EMBASE databases; study selection and quality assessment were conducted using current best practices. For each review, study characteristics and findings were summarized.

RESULTS

A total of 36 studies were included. Review of prevalence studies (n = 22) indicated variation in the number of cases by region, and many regions were not represented at all. Regarding HRQoL (n = 12 studies), physical domains were consistently impacted, although findings regarding other domains and overall HRQoL were less clear. Cost studies (n = 2) encompassed 4 regions and revealed that costs related to the provision of care, including non-medical direct costs and indirect costs, accounted for the majority of FA-related costs.

DISCUSSION

Findings from this systematic review revealed several knowledge gaps that would preclude the conduct of a robust assessment of the benefits and outcomes associated with a disease-modifying FA therapy. Additional understanding regarding patient and caregiver HRQoL and costs is required.

A Comprehensive Triple-Repeat Primed PCR and a Long-Range PCR Agarose-Based Assay for Improved Genotyping of Guanine-Adenine-Adenine Repeats in Friedreich Ataxia

Friedreich ataxia is a rare autosomal recessive, neuromuscular degenerative disease caused by an expansion of a trinucleotide [guanine-adenine-adenine (GAA)] repeat in intron 1 of the FXN gene. It is common in the White population, characterized by progressive gait and limb ataxia, lack of tendon reflexes in the legs, loss of position sense, and hypertrophic cardiomyopathy. Detection and genotyping of the trinucleotide repeat length is important for the diagnosis and prognosis of the disease. A two-tier genotyping assay with an improved triple-repeat primed PCR (TR-PCR) for alleles <200 GAA repeats (±1 to 5 repeats) and an agarose gel-based, long-range PCR (LR-PCR) assay to genotype expanded alleles >200 GAA repeats (±50 repeats) is described. Of the 1236 DNA samples tested using TR-PCR, 31 were identified to have expanded alleles >200 repeats and were reflexed to the LR-PCR procedure for confirmation and quantification. The TR-PCR assay described herein is a diagnostic genotyping assay that reduces the need for further testing. The LR-PCR component is a confirmatory test for true homozygous and heterozygous samples with normal and expanded alleles, as indicated by the TR-PCR assay. The use of this two-tier method offers a comprehensive evaluation to detect and genotype the smallest and largest number of GAA repeats, improving the classification of FXN alleles as normal, mutable normal, borderline, and expanded alleles.

Interacting with AP1 complex mutated synergin gamma (SYNRG) reveals a novel coatopathy in the form of complicated hereditary spastic paraplegia

BACKGROUND

Today, it is known that about 80 genes are involved in the etiology of hereditary spastic paraplegia. However, there are many cases whose etiology could not be determined by extensive genetic tests such as whole-exome sequencing, clinical exome.

METHODS

Candidate genes were determined, since no clinically illuminating variant was detected in the whole-exome sequencing analysis of three patients, two of whom were siblings, with a complex hereditary spastic paraplegia phenotype.

RESULTS

The p.Leu1202Pro variant in the SYNRG gene in the 1st and 2nd cases, and the p.Gly533* variant in the 3rd case were homozygous.

DISCUSSION

We suggest that the SYNRG gene interacting with AP-1 (adaptor-related protein) from the AP complex family may cause the complex hereditary spastic paraplegia phenotype with extensive clinical spectrum. It may be important to evaluate SYNRG gene variants in patients with hereditary spastic paraplegia whose etiology has not been clarified.

An integrated modelling methodology for estimating global incidence and prevalence of hereditary spastic paraplegia subtypes SPG4, SPG7, SPG11, and SPG15

Background

Hereditary spastic paraplegias (HSPs) are progressively debilitating neurodegenerative disorders that follow heterogenous patterns of Mendelian inheritance. Available epidemiological evidence provides limited incidence and prevalence data, especially at the genetic subtype level, preventing a realistic estimation of the true social burden of the disease. The objectives of this study were to (1) review the literature on epidemiology of HSPs; and (2) develop an epidemiological model of the prevalence of HSP, focusing on four common HSP genetic subtypes at the country and region-level.

Methods

A model was constructed estimating the incidence at birth, survival, and prevalence of four genetic subtypes of HSP based on the most appropriate published literature. The key model parameters were assessed by HSP clinical experts, who provided feedback on the validity of assumptions. A model was then finalized and validated through comparison of outputs against available evidence. The global, regional, and national prevalence and patient pool were calculated per geographic region and per genetic subtype.

Results

The HSP global prevalence was estimated to be 3.6 per 100,000 for all HSP forms, whilst the estimated global prevalence per genetic subtype was 0.90 (SPG4), 0.22 (SPG7), 0.34 (SPG11), and 0.13 (SPG15), respectively. This equates to an estimated 3365 (SPG4) and 872 (SPG11) symptomatic patients, respectively, in the USA.

Conclusions

This is the first epidemiological model of HSP prevalence at the genetic subtype-level reported at multiple geographic levels. This study offers additional data to better capture the burden of illness due to mutations in common genes causing HSP, that can inform public health policy and healthcare service planning, especially in regions with higher estimated prevalence of HSP.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12883-022-02595-4.

The natural history of ataxia-telangiectasia (A-T): A systematic review

BACKGROUND

Ataxia-telangiectasia is an autosomal recessive, multi-system, and life-shortening disease caused by mutations in the ataxia-telangiectasia mutated gene. Although widely reported, there are no studies that give a comprehensive picture of this intriguing condition.

OBJECTIVES

Understand the natural history of ataxia-telangiectasia (A-T), as reported in scientific literature.

SEARCH METHODS

107 search terms were identified and divided into 17 searches. Each search was performed in PubMed, Ovid SP (MEDLINE) 1946-present, OVID EMBASE 1980 -present, Web of Science core collection, Elsevier Scopus, and Cochrane Library.

SELECTION CRITERIA

All human studies that report any aspect of A-T.

DATA COLLECTION AND ANALYSIS

Search results were de-duplicated, data extracted (including author, publication year, country of origin, study design, population, participant characteristics, and clinical features). Quality of case-control and cohort studies was assessed by the Newcastle-Ottawa tool. Findings are reported descriptively and where possible data collated to report median (interquartile range, range) of outcomes of interest.

MAIN RESULTS

1314 cases reported 2134 presenting symptoms. The most common presenting symptom was abnormal gait (1160 cases; 188 studies) followed by recurrent infections in classical ataxia-telangiectasia and movement disorders in variant ataxia-telangiectasia. 687 cases reported 752 causes of death among which malignancy was the most frequently reported cause. Median (IQR, range) age of death (n = 294) was 14 years 0 months (10 years 0 months to 23 years 3 months, 1 year 3 months to 76 years 0 months).

CONCLUSIONS

This review demonstrates the multi-system involvement in A-T, confirms that neurological symptoms are the most frequent presenting features in classical A-T but variants have diverse manifestations. We found that most individuals with A-T have life limited to teenage or early adulthood. Predominance of case reports, and case series demonstrate the lack of robust evidence to determine the natural history of A-T. We recommend population-based studies to fill this evidence gap.

Systematic Analysis of Brain MRI Findings in Adaptor Protein Complex 4-Associated Hereditary Spastic Paraplegia

BACKGROUND AND OBJECTIVES

AP-4-associated hereditary spastic paraplegia (AP-4-HSP: SPG47, SPG50, SPG51, SPG52) is an emerging cause of childhood-onset hereditary spastic paraplegia and mimic of cerebral palsy. This study aims to define the spectrum of brain MRI findings in AP-4-HSP and to investigate radioclinical correlations.

METHODS

We performed a systematic qualitative and quantitative analysis of 107 brain MRI studies from 76 individuals with genetically confirmed AP-4-HSP and correlation with clinical findings including surrogates of disease severity.

RESULTS

We define AP-4-HSP as a disorder of gray and white matter and demonstrate that abnormal myelination is common and that metrics of reduced white matter volume correlate with severity of motor symptoms. We identify a common diagnostic imaging signature consisting of (1) a thin splenium of the corpus callosum, (2) an absent or thin anterior commissure, (3) characteristic signal abnormalities of the forceps minor ("ears of the grizzly sign"), and (4) periventricular white matter abnormalities. The presence of 2 or more of these findings has a sensitivity of ∼99% for detecting AP-4-HSP; the combination of all 4 is found in ∼45% of cases. Compared to other HSPs with a thin corpus callosum, the absent anterior commissure appears to be specific to AP-4-HSP. Our analysis identified a subset of patients with polymicrogyria, underscoring the role of AP-4 in early brain development. These patients displayed a higher prevalence of seizures and status epilepticus, many at a young age.

DISCUSSION

Our findings define the MRI spectrum of AP-4-HSP, providing opportunities for early diagnosis, identification of individuals at risk for complications, and a window into the role of the AP-4 complex in brain development and neurodegeneration.

Current Status of Gene Therapy Research in Polyglutamine Spinocerebellar Ataxias

Polyglutamine spinocerebellar ataxias (PolyQ SCAs) are a group of 6 rare autosomal dominant diseases, which arise from an abnormal CAG repeat expansion in the coding region of their causative gene. These neurodegenerative ataxic disorders are characterized by progressive cerebellar degeneration, which translates into progressive ataxia, the main clinical feature, often accompanied by oculomotor deficits and dysarthria. Currently, PolyQ SCAs treatment is limited only to symptomatic mitigation, and no therapy is available to stop or delay the disease progression, which culminates with death. Over the last years, many promising gene therapy approaches were investigated in preclinical studies and could lead to a future treatment to stop or delay the disease development. Here, we summed up the most promising of these therapies, categorizing them in gene augmentation therapy, gene silencing strategies, and gene edition approaches. While several of the reviewed strategies are promising, there is still a gap from the preclinical results obtained and their translation to clinical studies. However, there is an increase in the number of approved gene therapies, as well as a constant development in their safety and efficacy profiles. Thus, it is expected that in a near future some of the promising strategies reviewed here could be tested in a clinical setting and if successful provide hope for SCAs patients.

Genetic and Epidemiological Study of Adult Ataxia and Spastic Paraplegia in Eastern Quebec

OBJECTIVE

To estimate the minimum prevalence of adult hereditary ataxias (HA) and spastic paraplegias (HSP) in Eastern Quebec and to evaluate the proportion of associated mutations in identified genes.

METHODS

We conducted a descriptive cross-sectional study of patients who met clinical criteria for the diagnosis of HA (n = 241) and HSP (n = 115) in the East of the Quebec province between January 2007 and July 2019. The primary outcome was the prevalence per 100,000 persons with a 95% confidence interval (CI). The secondary outcome was the frequency of mutations identified by targeted next-generation sequencing (NGS) approach. Minimum carrier frequency for identified variants was calculated based on allele frequency values and the Hardy-Weinberg (HW) equation.

RESULTS

The minimum prevalence of HA in Eastern Quebec was estimated at 6.47/100 000 [95% CI; 6.44-6.51]; divided into 3.73/100 000 for autosomal recessive (AR) ataxias and 2.67/100 000 for autosomal dominant (AD) ataxias. The minimum prevalence of HSP was 4.17/100 000 [95% CI; 4.14-4.2]; with 2.05/100 000 for AD-HSP and 2.12/100 000 for AR-HSP. In total, 52.4% of patients had a confirmed genetic diagnosis. AR cerebellar ataxia type 1 (2.67/100 000) and AD spastic paraplegia SPG4 (1.18/100 000) were the most prevalent disorders identified. Mutations were identified in 23 genes and molecular alterations in 7 trinucleotides repeats expansion; the most common mutations were c.15705-12 A > G in SYNE1 and c.1529C > T (p.A510V) in SPG7.

CONCLUSIONS

We described the minimum prevalence of genetically defined adult HA and HSP in Eastern Quebec. This study provides a framework for international comparisons and service planning.

Familiarity with Hereditary Spastic Paraplegia (HSP) and Differentiation of Upper Body Gait Characteristics between Children with HSP and Spastic Diplegic Cerebral Palsy

AIMS

The aim of this two-part, prospective study was to determine therapist familiarity with HSP and examine diagnostic accuracy between individuals with HSP and those with Spastic Diplegic Cerebral Palsy (SD-CP).

METHODS

Part-one surveyed physical therapists (PT) and physical therapist assistants (PTA) throughout Texas to determine familiarity with HSP and its gait deviations. Part-two examined accuracy in differential diagnosis of HSP versus SD-CP using gait analysis and the effects of an educational module on upper body gait deviations observed in individuals with HSP.

RESULTS

Both PTs and PTAs indicated a high degree (≥73.2%) of unfamiliarity with HSP. While a majority of respondents (≥88.7%) indicated use of observational gait analysis in clinical practice, ≥92.5% indicated never receiving instruction on HSP or its associated gait deviations. Whole group analysis revealed diagnostic accuracy increased 21.7% post educational module. In addition, individual case diagnostic accuracy yielded significant improvement in 14 out of 20 cases.

CONCLUSIONS

Physical and occupational therapists are in a unique position to assist with the identification and distinction of HSP from CP. This study demonstrated that brief instruction on common upper body gait deviations seen in individuals with HSP may improve a clinician's ability to distinguish SD-CP from HSP via gait analysis.

Defining the clinical, molecular and imaging spectrum of adaptor protein complex 4-associated hereditary spastic paraplegia

Bi-allelic loss-of-function variants in genes that encode subunits of the adaptor protein complex 4 (AP-4) lead to prototypical yet poorly understood forms of childhood-onset and complex hereditary spastic paraplegia: SPG47 (AP4B1), SPG50 (AP4M1), SPG51 (AP4E1) and SPG52 (AP4S1). Here, we report a detailed cross-sectional analysis of clinical, imaging and molecular data of 156 patients from 101 families. Enrolled patients were of diverse ethnic backgrounds and covered a wide age range (1.0-49.3 years). While the mean age at symptom onset was 0.8 ± 0.6 years [standard deviation (SD), range 0.2-5.0], the mean age at diagnosis was 10.2 ± 8.5 years (SD, range 0.1-46.3). We define a set of core features: early-onset developmental delay with delayed motor milestones and significant speech delay (50% non-verbal); intellectual disability in the moderate to severe range; mild hypotonia in infancy followed by spastic diplegia (mean age: 8.4 ± 5.1 years, SD) and later tetraplegia (mean age: 16.1 ± 9.8 years, SD); postnatal microcephaly (83%); foot deformities (69%); and epilepsy (66%) that is intractable in a subset. At last follow-up, 36% ambulated with assistance (mean age: 8.9 ± 6.4 years, SD) and 54% were wheelchair-dependent (mean age: 13.4 ± 9.8 years, SD). Episodes of stereotypic laughing, possibly consistent with a pseudobulbar affect, were found in 56% of patients. Key features on neuroimaging include a thin corpus callosum (90%), ventriculomegaly (65%) often with colpocephaly, and periventricular white-matter signal abnormalities (68%). Iron deposition and polymicrogyria were found in a subset of patients. AP4B1-associated SPG47 and AP4M1-associated SPG50 accounted for the majority of cases. About two-thirds of patients were born to consanguineous parents, and 82% carried homozygous variants. Over 70 unique variants were present, the majority of which are frameshift or nonsense mutations. To track disease progression across the age spectrum, we defined the relationship between disease severity as measured by several rating scales and disease duration. We found that the presence of epilepsy, which manifested before the age of 3 years in the majority of patients, was associated with worse motor outcomes. Exploring genotype-phenotype correlations, we found that disease severity and major phenotypes were equally distributed among the four subtypes, establishing that SPG47, SPG50, SPG51 and SPG52 share a common phenotype, an 'AP-4 deficiency syndrome'. By delineating the core clinical, imaging, and molecular features of AP-4-associated hereditary spastic paraplegia across the age spectrum our results will facilitate early diagnosis, enable counselling and anticipatory guidance of affected families and help define endpoints for future interventional trials.

Evidence and practices of the use of next generation sequencing in patients with undiagnosed autosomal dominant cerebellar ataxias: a review

Autosomal dominant cerebellar ataxias (ADCA) are heterogeneous diseases with a highly variable phenotype and genotype. They can be divided into episodic ataxia and spinocerebellar ataxia (SCA); the latter is considered the prototype of the ADCA. Most of the ADCA are caused by polyglutamine expansions, mainly SCA 1, 2, 3, 6, 7, 17 and Dentatorubral-pallidoluysian atrophy (DRPLA). However, 30% of patients remain undiagnosed after testing for these most common SCA. Recently, several studies have demonstrated that the new generation of sequencing methods are useful for the diagnose of these patients. This review focus on searching evidence on the literature, its usefulness in clinical practice and future perspectives.

Genetic mutation analysis of hereditary spastic paraplegia: A retrospective study

Hereditary spastic paraplegias are heterogeneous disorders with diversified clinical manifestations, and genetic testing is important for the diagnosis and typing of hereditary spastic paraplegias.Gene panel sequencing containing 55 hereditary spastic paraplegias-related genes was performed to screen the pathogenic genes for hereditary spastic paraplegias. Sanger sequencing was adopted to validate if the family member carried the same pathogenic gene as the proband.Fifteen out of 53 patients carried mutation(s) in the screened hereditary spastic paraplegias-related genes. Among the 23 identified mutations, only one mutation had been previously reported as a pathogenic mutation. In the pedigree of case 6, the proband, his mother and uncle all carried the same novel deletion mutation (c.1459delA) at SPAST gene. Based on the pedigree, the disease was inherited in an AD pattern. In the pedigree of case 53, the family disease may be in an X-linked recessive inheritance pattern. The proband (case 53) carried two novel mutations in ALT1 gene and L1CAM gene (c.2511C>A), respectively. The L1CAM gene is the causative gene for the SPG1 X-linked recessive-hereditary spastic paraplegias.Our data confirm the genetic heterogeneity of hereditary spastic paraplegias, and SPG4/SPAST were the most frequent forms. The pathogenicity of the novel mutations is worth to be further investigated.

Determinants of age at onset in a Portuguese cohort of autosomal dominant spastic paraplegia

BACKGROUND

Hereditary spastic paraplegias present a high variability of age at onset, ranging from childhood to older age. Our objective was to identify the determinants of age at onset in autosomal dominant HSP (AD-HSP) in a large cohort of patients and families.

METHODS

We included 239 patients from 89 families identified in the Portuguese multisource population-based survey of hereditary ataxias and spastic paraplegias. Patients were systematically examined by a team of neurologists, admitted for complete clinical workup and tested for SPG3, SPG4 and SPG31.

RESULTS

Average age at onset was 38.2 years in the first generation, 32.3 years in the second and 17.5 years in the third, with a significant decrease of average age at onset between generations (p < .001). A decrease in the average age at onset was seen in all genotypes (SPG4: p < .001; SPG3: p = .15; SPG31: p < .001). In families with more than one generation (n = 38), this decrease was observed in 78.9%. In multivariate linear regression model, the independent effect of generation in anticipation of age at onset was confirmed (p < .001), adjusting for family, genotype and mutation. We also observed a significant lower age at onset in patients with missense versus truncating mutations (p = .015) in patients with SPG4.

CONCLUSION

These results confirm the impact of missense mutations in an earlier age at onset in SPG4 patients. Even though the age at onset could be affected by subjectivity, our results are consistent with the presence of an anticipation phenomenon in AD-HSP.

Nationwide prevalence of primary dystonia, progressive ataxia and hereditary spastic paraplegia

OBJECTIVE

To determine the nationwide prevalence of primary dystonia, ataxia and hereditary spastic paraplegia (HSP) in Sweden.

METHODS

We extracted data on all patients who were registered in The National Patient Register (NPR) in Sweden (population 9.64 million) at least twice during five consecutive years with a diagnosis of primary dystonia, ataxia or HSP. We excluded patients with an additional diagnosis possibly indicating secondary causes, and determined the proportion of wrongly diagnosed patients at our own tertiary center by patient examination or chart review. We analyzed patients' age and disorder subtypes, geographical distribution of patients within Sweden and the country of birth of all patients.

RESULTS

Nationwide, we identified 4239 patients (31.6% male) with a diagnosis of primary dystonia. Of 347 patients with dystonia at our center, 20.2% may have had a different final diagnosis. Extrapolation of this uncertainty rate to the national population resulted in a prevalence for primary dystonia of 35.1/100,000. There were 672 patients (49.6% male) with ataxia in NPR, and the diagnostic uncertainty rate among 81 patients in our center was 13.6% (prevalence 6.0/100,000). HSP was diagnosed in 235 patients nationwide (52.3% male, prevalence 2.4/100,000). Patients were distributed relatively evenly throughout the country. The proportions of patients with these diagnoses who were born outside of Sweden were lower (8.0-12.7%) than the proportion of all Swedish residents born abroad (15.9%).

CONCLUSIONS

In this large, nationwide study, the prevalence of dystonia was high compared to previous studies, which partly may be explained by the high coverage of NPR.

Ascending Axonal Degeneration of the Corticospinal Tract in Pure Hereditary Spastic Paraplegia: A Cross-Sectional DTI Study

Objective: To identify structural white matter alterations in patients with pure hereditary spastic paraplegia (HSP) using high angular resolution diffusion tensor imaging (DTI). Methods: We examined 37 individuals with high resolution DTI, 20 patients with pure forms of hereditary spastic paraplegia and 17 age and gender matched healthy controls. DTI was performed using a 3 T clinical scanner with whole brain tract-based spatial statistical (TBSS) analysis of the obtained fractional anisotropy (FA) data as well as a region-of-interest (ROI)-based analysis of affected tracts including the cervical spinal cord. We further conducted correlation analyses between DTI data and clinical characteristics. Results: TBSS analysis in HSP patients showed significantly decreased fractional anisotropy of the corpus callosum and the corticospinal tract compared to healthy controls. ROI-based analysis confirmed significantly lower FA in HSP compared to controls in the internal capsule (0.77 vs. 0.80, p = 0.048), the corpus callosum (0.84 vs. 0.87, p = 0.048) and the cervical spinal cord (0.72 vs. 0.79, p = 0.003). FA values of the cervical spinal cord significantly correlated with disease duration. Conclusion: DTI metrics of the corticospinal tract from the internal capsule to the cervical spine suggest microstructural damage and axonal degeneration of motor neurons. The CST at the level of the cervical spinal cord is thereby more severely affected than the intracranial part of the CST, suggesting an ascending axonal degeneration of the CST. Since there is a significant correlation with disease duration, FA may serve as a future progression marker for assessment of the disease course in HSP.

A clinical diagnostic algorithm for early onset cerebellar ataxia

Early onset cerebellar Ataxia (EOAc) comprises a large group of rare heterogeneous disorders. Determination of the underlying etiology can be difficult given the broad differential diagnosis and the complexity of the genotype-phenotype relationships. This may change the diagnostic work-up into a time-consuming, costly and not always rewarding task. In this overview, the Childhood Ataxia and Cerebellar Group of the European Pediatric Neurology Society (CACG-EPNS) presents a diagnostic algorithm for EOAc patients. In seven consecutive steps, the algorithm leads the clinician through the diagnostic process, including EOA identification, application of the Inventory of Non-Ataxic Signs (INAS), consideration of the family history, neuro-imaging, laboratory investigations, genetic testing by array CGH and Next Generation Sequencing (NGS). In children with EOAc, this algorithm is intended to contribute to the diagnostic process and to allow uniform data entry in EOAc databases.

Nonmotor symptoms in spinocerebellar ataxias (SCAs)

Nonmotor symptoms (NMS) have been increasingly recognized in a number of neurodegenerative diseases with a burden of disability that parallels or even surpasses that induced by motor symptoms. As NMS have often been poorly recognized and inadequately treated, much of the most recent developments in the investigation of these disorders has focused on the recognition and quantification of NMS, which will form the basis of improved clinical care for these complex cases. NMS have been only sparsely investigated in a limited number of spinocerebellar ataxias (SCAs), particularly SCA3, and have not been systematically reviewed for other forms of SCAs. The aim of the present study was to review the available literature on the presence of NMS among different types of SCAs.

Hereditary Myelopathies

PURPOSE OF REVIEW

Hereditary myelopathies are very diverse genetic disorders, and many of them represent a widespread neurodegenerative process rather than isolated spinal cord dysfunction. This article reviews various types of inherited myelopathies, with emphasis on hereditary spastic paraplegias and spastic ataxias.

RECENT FINDINGS

The ever-growing number of myelopathy-causing genes and broadening of phenotype-genotype correlations makes the molecular diagnosis of inherited myelopathies a daunting task. This article emphasizes the main phenotypic clusters among inherited myelopathies that can facilitate the diagnostic process. This article focuses on newly identified genetic causes and the most important identifying clinical features that can aid the diagnosis, including the presence of a characteristic age of onset and additional neurologic signs such as leukodystrophy, thin corpus callosum, or amyotrophy.

SUMMARY

The exclusion of potentially treatable causes of myelopathy remains the most important diagnostic step. Syndromic diagnosis can be supported by molecular diagnosis, but the genetic diagnosis at present does not change the management. Moreover, a negative genetic test does not exclude the diagnosis of a hereditary myelopathy because comprehensive molecular testing is not yet available, and many disease-causing genes remain unknown.

Clinical features and genetic spectrum in Chinese patients with recessive hereditary spastic paraplegia

Background

Although many causative genes of hereditary spastic paraplegia (HSP) have been uncovered in recent years, there are still approximately 50% of HSP patients without genetically diagnosis, especially in autosomal recessive (AR) HSP patients. Rare studies have been performed to determine the genetic spectrum and clinical profiles of recessive HSP patients in the Chinese population.

Methods

In this study, we investigated 24 Chinese index AR/sporadic patients by targeted next-generation sequencing (NGS), Sanger sequencing and multiplex ligation-dependent probe amplification (MLPA). Further functional studies were performed to identify pathogenicity of those uncertain significance variants.

Results

We identified 11 mutations in HSP related genes including 7 novel mutations, including two (p.V1979_L1980delinsX, p.F2343 fs) in SPG11, two (p.T55 M, p.S308 T) in AP5Z1, one (p.S242 N) in ALDH18A1, one (p.D597fs) in GBA2, and one (p.Q486X) in ATP13A2 in 8 index patients and their family members. Mutations in ALDH18A1, AP5Z1, CAPN1 and ATP13A2 genes were firstly reported in the Chinese population. Furthermore, the clinical phenotypes of the patients carrying mutations were described in detail. The mutation (p.S242 N) in ALDH18A1 decreased enzyme activity of P5CS and mutations (p.T55 M, p.S308 T) in AP5Z1 induced lysosomal dysfunction.

Conclusion

Our results expanded the genetic spectrum and clinical profiles of AR-HSP patients and further demonstrated the efficiency and reliability of targeted NGS diagnosing suspected HSP patients.

Electronic supplementary material

The online version of this article (10.1186/s40035-019-0157-9) contains supplementary material, which is available to authorized users.

Hereditary spastic paraplegia type 35 in a family from Mali

Variants in FA2H have been associated with a wide range of phenotypes including hereditary spastic paraplegia type 35 (SPG35); however, genetically confirmed cases have not been reported in Africa. We report here the first African family with a variant in the FA2H gene causing SPG35. Four affected siblings with consanguineous parents presented with walking difficulty at age 2-3 and progressive limb weakness. They became wheelchair-bound 2 years after disease onset. Neurological examination confirmed lower greater than upper limb weakness and atrophy, brisk reflexes throughout, and spasticity with scissor legs. The patients also had choking, urinary urgency, and mental retardation. A brain MRI showed thin corpus callosum and periventricular leucodystrophy. Testing of 58 SPG genes showed a homozygous variant in FA2H at the exon 5 donor site c.786+1G>A, which has previously been shown to cause skipping of exons 5 and 6 of the gene transcript. This variant segregated with the disease in the family. This variant has been reported previously with a similar phenotype and slow progression in a population with different background. Here, we confirm its pathogenicity and expand its genetic epidemiology. Studying diverse populations may help to increase understanding of the disease mechanism and ultimately lead to therapeutic targets.

Aminopyridines and Acetyl-DL-leucine: New Therapies in Cerebellar Disorders

Cerebellar ataxia is a frequent and often disabling syndrome severely impairing motor functioning and quality of life. Patients suffer from reduced mobility, and restricted autonomy, experiencing an even lower quality of life than, e.g., stroke survivors. Aminopyridines have been demonstrated viable for the symptomatic treatment of certain forms of cerebellar ataxia. This article will give an outline of the present pharmacotherapy of different cerebellar disorders. As a current key-therapy for the treatment of downbeat nystagmus 4-aminopyridine (4-AP) is suggested for the treatment of downbeat nystagmus (5-10 mg Twice a day [TID]), a frequent type of persisting nystagmus, due to a compromise of the vestibulo-cerebellum. Studies with animals have demonstrated, that a nonselective blockage of voltage-gated potassium channels (mainly Kv1.5) increases Purkinje- cell (PC) excitability. In episodic ataxia type 2 (EA2), which is frequently caused by mutations of the PQ-calcium channel, the efficacy of 4-AP (5-10 mg TID) has been shown in a randomized controlled trial (RCT). 4-AP was well tolerated in the recommended dosages. 4-AP was also effective in elevating symptoms in cerebellar gait ataxia of different etiologies (2 case series). A new treatment option for cerebellar disease is the amino-acid acetyl-DL-leucine, which has significantly improved cerebellar symptoms in three case series. There are on-going randomized controlled trials for cerebellar ataxia (acetyl-DL-leucine vs placebo; ALCAT), cerebellar gait disorders (SR-form of 4-AP vs placebo; FACEG) and EA2 (sustained-release/SR-form of 4-AP vs acetazolamide vs placebo; EAT2TREAT), which will provide new insights into the pharmacological treatment of cerebellar disorders.

Genetics, Mechanisms, and Therapeutic Progress in Polyglutamine Spinocerebellar Ataxias

Autosomal dominant cerebellar ataxias (ADCAs) are a group of neurodegenerative disorders characterized by degeneration of the cerebellum and its connections. All ADCAs have progressive ataxia as their main clinical feature, frequently accompanied by dysarthria and oculomotor deficits. The most common spinocerebellar ataxias (SCAs) are 6 polyglutamine (polyQ) SCAs. These diseases are all caused by a CAG repeat expansion in the coding region of a gene. Currently, no curative treatment is available for any of the polyQ SCAs, but increasing knowledge on the genetics and the pathological mechanisms of these polyQ SCAs has provided promising therapeutic targets to potentially slow disease progression. Potential treatments can be divided into pharmacological and gene therapies that target the toxic downstream effects, gene therapies that target the polyQ SCA genes, and stem cell replacement therapies. Here, we will provide a review on the genetics, mechanisms, and therapeutic progress in polyglutamine spinocerebellar ataxias.

[Common forms of hereditary spastic paraplegias]

A group of hereditary spastic paraplegias includes about 80 spastic paraplegia genes (SPG): forms with identified (almost 70) or only mapped (about 10) genes. Methods of next generation sequencing (NGS), along with new SPG discovering, modify knowledge about earlier delineated SPG. Clinical and genetic characteristics of common autosomal dominant (SPG4, SPG3, SPG31) and autosomal recessive (SPG11, SPG7, SPG15) forms are presented.

Clinical Trial Designs and Measures in Hereditary Spastic Paraplegias

Hereditary spastic paraplegias (HSPs) are a large group of genetically-diverse neurologic disorders characterized clinically by a common feature of lower extremity spasticity and gait difficulties. Current therapies are predominantly symptomatic, and even then usually provide inadequate relief of symptoms. Going forward, HSP therapeutics development requires a systematic analysis of quantifiable measures and tools to assess treatment response. This review summarizes promising therapeutic targets, assessment measures, and previous clinical trials for the HSPs. Oxidative stress, signaling pathways, microtubule dynamics, and gene rescue/replacement have been proposed as potential treatment targets or modalities. Quantitative evaluation of pre-clinical rodent HSP models emphasize rotarod performance, foot base angle, grip strength, stride length, beam walking, critical speed, and body weight. Clinical measures of HSP in humans include 10-m gait velocity, the Spastic Paraplegia Rating Scale (SPRS), Ashworth Spasticity Scale, Fugl-Meyer Scale, timed up-and-go, and the Gillette Functional Assessment Questionnaire. We conducted a broad search for past clinical trials in HSPs and identified trials that investigated pharmacological agents including atorvastatin, gabapentin, L-threonine, botulinum toxin, dalfampridine, methylphenidate, and baclofen. We provide recommendations for future HSP treatment directions based on these prior research experiences as well as regulatory insight.

Homocarnosinosis: A historical update and findings in the SPG11 gene

OBJECTIVES

A family with homocarnosinosis was reported in the literature in 1976. Three affected siblings had spastic paraplegia, retinitis pigmentosa, mental retardation, and cerebrospinal fluid (CSF) homocarnosine concentrations 20 times higher than in controls. Based on the clinical findings and new genetic techniques, we have been able to establish a precise genetic diagnosis.

METHOD

The medical records were re-evaluated, and genetic analyses were performed post-mortem in this original family. SNP array-based whole genome homozygosity mapping and Sanger sequencing of the SPG11 gene were performed. Seven additional Norwegian SPG11 patients and their disease-causing variants and clinical findings were evaluated. Homocarnosine levels in CSF were measured in four of these seven patients.

RESULTS

A homozygous pathogenic splice-site variant in the SPG11 gene, c.2316 + 1G>A, was found. The clinical findings in the original family correlate with the heterogeneous SPG11 phenotype. The same variant was found in seven other Norwegian SPG11 patients, unrelated to the original family, either as homozygous or compound heterozygous constellation. Normal homocarnosine levels were found in the CSF of all unrelated SPG11 patients.

CONCLUSIONS

A re-evaluation of the clinical symptoms and findings in the original family correlates with the SPG11 phenotype. The increased levels of homocarnosine do not seem to be a biomarker for SPG11 in our patients. Homocarnosinosis is still a biochemical aberration with unknown clinical significance.