Hereditary spastic paraparesis type 46 (SPG46): new GBA2 variants in a large Italian case series and review of the literature

Hereditary spastic paraparesis (HSP) is a group of central nervous system diseases primarily affecting the spinal upper motor neurons, with different inheritance patterns and phenotypes. SPG46 is a rare, early-onset and autosomal recessive HSP, linked to biallelic GBA2 mutations. About thirty families have been described worldwide, with different phenotypes like complicated HSP, recessive cerebellar ataxia or Marinesco-Sjögren Syndrome. Herein, we report five SPG46 patients harbouring five novel GBA2 mutations, the largest series described in Italy so far. Probands were enrolled in five different centres and underwent neurological examination, clinical cognitive assessment, column imaging for scoliosis assessment, ophthalmologic examination, brain imaging, GBA2 activity in peripheral blood cells and genetic testing. Their phenotype was consistent with HSP, with notable features like upper gaze palsy and movement disorders. We review demographic, genetic, biochemical and clinical information from all documented cases in the existing literature, focusing on the global distribution of cases, the features of the syndrome, its variable presentation, new potential identifying features and the significance of measuring GBA2 enzyme activity.

Hereditary spastic paraparesis type 18 (SPG18): new ERLIN2 variants in a series of Italian patients, shedding light upon genetic and phenotypic variability

INTRODUCTION

Hereditary spastic paraparesis (HSP) is a group of central nervous system diseases primarily affecting the spinal upper motor neurons, with different inheritance patterns and phenotypes. SPG18 is a rare, early-onset, complicated HSP, first reported as linked to biallelic ERLIN2 mutations. Recent cases of late-onset, pure HSP with monoallelic ERLIN2 variants prompt inquiries into the zygosity of such genetic conditions. The observed relationship between phenotype and mode of inheritance suggests a potential dominant negative effect of mutated ERLIN2 protein, potentially resulting in a milder phenotype. This speculation suggests that a wider range of HSP genes could be linked to various inheritance patterns.

PURPOSE AND BACKGROUND

With documented cases of HSP loci exhibiting both dominant and recessive patterns, this study emphasizes that the concept of zygosity is no longer a limiting factor in the establishment of molecular diagnoses for HSP. Recent cases have demonstrated phenoconversion in SPG18, from HSP to an amyotrophic lateral sclerosis (ALS)-like syndrome.

METHODS AND RESULTS

This report highlights two cases out of five exhibiting HSP-ALS phenoconversion, discussing an observed prevalence in autosomal dominant SPG18. Additionally, the study emphasizes the relatively high incidence of the c.502G>A variant in monoallelic SPG18 cases. This mutation appears to be particularly common in cases of HSPALS phenoconversion, indicating its potential role as a hotspot for a distinctive SPG18 phenotype with an ALS-like syndrome.

CONCLUSIONS

Clinicians need to be aware that patients with HSP may show ALS signs and symptoms. On the other hand, HSP panels must be included in genetic testing methods for instances of familial ALS.

Individual perception of environmental factors that influence lower limbs spasticity in inherited spastic paraparesis

BACKGROUND

Phenotypic variability is a consistent finding in neurogenetics and therefore applicable to hereditary spastic paraparesis. Identifying reasons for this variability is a challenge. We hypothesized that, in addition to genetic modifiers, extrinsic factors influence variability.

OBJECTIVES

Our aim was to describe the clinical variability in hereditary spastic paraparesis from the person's perspective. Our goals were to identify individual and environmental factors that influence muscle tone disorders and derive interventions which could improve spasticity.

METHODS

This study was based on self-assessments with questions on nominal and ordinal scales completed by participants with hereditary spastic paraparesis. A questionnaire was completed either in-person in the clinic or electronically via lay organization websites.

RESULTS

Among the 325 responders, most had SPG4/SPAST (n = 182, 56%) with a mean age at onset of 31.7 (SD 16.7) years and a mean disease duration of 23 (SD 13.6) years at the time of participation. The 2 factors identified as improving spasticity for > 50% of the responders were physiotherapy (193/325, 59%), and superficial warming (172/308, 55%). Half of the responders (n = 164, 50%) performed physical activity at least once a month and up to once a week. Participants who reported physiotherapy as effective were significantly more satisfied with ≥ 3 sessions per week. Psychologically stressful situations (246/319, 77%) and cold temperatures (202/319, 63%) exacerbated spasticity for most participants.

CONCLUSION

Participants perceived that physiotherapy reduced spasticity and that the impact of physiotherapy on spasticity was much greater than other medical interventions. Therefore, people should be encouraged to practice physical activity at least 3 times per week. This study reported participants' opinions: in hereditary spastic paraparesis only functional treatments exist, therefore the participant's expertise is of particular importance.

Hereditary spastic paraparesis (HSP) presenting as cerebral palsy due to ADD3 variant with mechanistic insight provided by a Drosophila γ-adducin model

INTRODUCTION

Cerebral palsy (CP) causes neurological disability in early childhood. Hypoxic-ischaemic injury plays a major role in its aetiology, nevertheless, genetic and epigenetic factors may contribute to the clinical presentation. Mutations in ADD3 (encoding γ-adducin) gene have been described in a monogenic form of spastic quadriplegic cerebral palsy (OMIM 601568).

METHODS

We studied a sixteen-year-old male with spastic diplegia. Several investigations including neurometabolic testing, brain and spine magnetic resonance imaging (MRI) and CGH-Array were normal. Further, clinical genetics assessment and Whole Exome Sequencing (WES) gave the diagnosis. We generated an animal model using Drosophila to study the effects of γ-adducin loss and gain of function.

RESULTS

WES revealed a biallelic variant in the ADD3 gene, NM_016824.5(ADD3): c.1100G>A, p.(Gly367Asp). Mutations in this gene have been described as an ultra-rare autosomal recessive which is a known form of inherited cerebral palsy. Molecular modelling suggests that this mutation leads to a loss of structural integrity of γ-adducin and is therefore expected to result in a decreased level of functional protein. Pan-neuronal over-expression or knock-down of the Drosophila ortholog of ADD3 called hts caused a reduction of life span and impaired locomotion thereby phenocopying aspects of the human disease.

CONCLUSION

Our animal experiments present a starting point to understand the biological processes underpinning the clinical phenotype and pathogenic mechanisms, to gain insights into potential future methods for treating or preventing ADD3 related spastic quadriplegic cerebral palsy.

Monoallelic KIF1A-related disorders: a multicenter cross sectional study and systematic literature review

BACKGROUND

Monoallelic variants in the KIF1A gene are associated with a large set of clinical phenotypes including neurodevelopmental and neurodegenerative disorders, underpinned by a broad spectrum of central and peripheral nervous system involvement.

METHODS

In a multicenter study conducted in patients presenting spastic gait or complex neurodevelopmental disorders, we analyzed the clinical, genetic and neuroradiological features of 28 index cases harboring heterozygous variants in KIF1A. We conducted a literature systematic review with the aim to comparing our findings with previously reported KIF1A-related phenotypes.

RESULTS

Among 28 patients, we identified nine novel monoallelic variants, and one a copy number variation encompassing KIF1A. Mutations arose de novo in most patients and were prevalently located in the motor domain. Most patients presented features of a continuum ataxia-spasticity spectrum with only five cases showing a prevalently pure spastic phenotype and six presenting congenital ataxias. Seventeen mutations occurred in the motor domain of the Kinesin-1A protein, but location of mutation did not correlate with neurological and imaging presentations. When tested in 15 patients, muscle biopsy showed oxidative metabolism alterations (6 cases), impaired respiratory chain complexes II + III activity (3/6) and low CoQ10 levels (6/9). Ubiquinol supplementation (1gr/die) was used in 6 patients with subjective benefit.

CONCLUSIONS

This study broadened our clinical, genetic, and neuroimaging knowledge of KIF1A-related disorders. Although highly heterogeneous, it seems that manifestations of ataxia-spasticity spectrum disorders seem to occur in most patients. Some patients also present secondary impairment of oxidative metabolism; in this subset, ubiquinol supplementation therapy might be appropriate.

The use of intrathecal baclofen for management of spasticity in hereditary spastic paraparesis: A case series

Hereditary Spastic Paraparesis (HSP) causes lower limb spasticity, pain and limits ambulation resulting in a negative impact on an individual's quality of life. This case series evaluates the use of Intra-thecal Baclofen (ITB) on 5 ambulant children with HSP. Our results suggest ITB is associated with a reduction in spasticity and a trend towards improvement in patient-reported quality of life and achievement of personalised goals. This was evidenced with lower Modified Ashworth Scale (MAS) scores and increasing values using the Cerebral Palsy Quality of Life (CPQoL) tool and Goal Attainment Scale (GAS). ITB was not associated with any major immediate or longer-term adverse effects. Overall, our study supports the role of ITB, used in a goal-directed manner, in the management of children and young people with HSP where other standard treatment options have been unsuccessful.

Exome sequencing implicates a novel heterozygous missense variant in DSTYK in autosomal dominant lower urinary tract dysfunction and mild hereditary spastic paraparesis

Introduction

DSTYK encodes dual serine/threonine and tyrosine protein kinase. DSTYK has been associated with autosomal-dominant congenital anomalies of the kidney and urinary tract and with autosomal-recessive hereditary spastic paraplegia type 23. Here, we report a father and his two dizygotic twin sons carrying a novel heterozygous missense variant in DSTYK, presenting with early onset lower urinary tract dysfunction due to dysfunctional voiding. Moreover, in the later course of the disease, both sons presented with bilateral spasticity in their lower limbs, brisk reflexes, and absence seizures.

Materials and methods

Exome sequencing in the affected father and his affected sons was performed. The sons presented clinically with urinary hesitancy, dysfunctional voiding, and night incontinence till adolescence, while the father reported difficulty in voiding. In the sons, cystoscopy excluded urethral valves and revealed hypertrophy of the bladder neck and trabeculated bladder. Additionally, both sons were diagnosed with absence epilepsy in early childhood. Filtering of exome data focused on rare (MAF < 0.01%), autosomal-dominant variants, predicted to be deleterious, residing in highly conserved regions of the exome.

Results

Exome analysis identified a novel, heterozygous missense variant (c.271C>A (p.Leu91Met)) in DSTYK segregating with the disease. In silico prediction analyses uniformly rated the variant to be deleterious suggesting the variant to be disease-causing in the family.

Conclusion

To the best of our knowledge, this is the first report of early onset dysfunctional voiding, seizures, and bilateral spasticity of the lower limbs associated with a novel heterozygous dominant missense variant in DSTYK.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40348-021-00122-y.

Corticospinal tract and motor cortex degeneration in pure hereditary spastic paraparesis type 4 (SPG4)

Objective: SPG4 is an autosomal dominant pure form of hereditary spastic paraplegia (HSP) caused by mutations in the SPAST gene. HSP is considered an upper motor neuron disorder characterized by progressive retrograde degeneration, or "dying-back" phenomenon, of the corticospinal tract's longest axons. Neuroimaging studies mainly focus on white matter changes and, although previous studies reported cortical thinning in complicated HSP forms, cortical changes remain unclear in SPG4 patients. This work aimed to compare changes in white matter microstructure and cortical thickness between 12 SPG4 patients and 22 healthy age-matched controls. We also explore whether white matter alterations are related to cortical thickness and their correlation with clinical symptoms. Methods: we used fixel-based analysis, an advanced diffusion-weighted imaging technique, and probabilistic tractography of the corticospinal tracts. We also analyzed cortical morphometry using whole-brain surface-based and atlas-based methods in sensorimotor areas. Results: SPG4 patients showed bilateral involvement in the corticospinal tracts; this was more intense in the distal portion than in the upper segments and was associated with the degree of clinical impairment. We found a significant correlation between disease severity and fiber density and cross-section of the corticospinal tracts. Furthermore, corticospinal tract changes were significantly correlated with bilateral cortical thinning in the precentral gyrus in SPG4 patients. Conclusions: Our data point to axonal damage of the corticospinal motor neurons in SPG4 patients might be related to cortical thinning in motor regions.

Neuroimaging patterns in paediatric onset hereditary spastic paraplegias

Hereditary spastic paraplegias (HSPs) are a clinically and genetically heterogeneous group of neurodegenerative disorders characterized by progressive spasticity and weakness of the lower limbs with a notable phenotypic variation and an autosomal recessive (AR), autosomal dominant (AD), and X-linked inheritance pattern. The recent clinical use of next generation sequencing methods has facilitated the diagnostic approach to HSPs, but the diagnosis remains quite challenging considering its wide clinical and genetic heterogeneity. In this scenario, magnetic resonance imaging (MRI) emerges as a valuable tool in helping to exclude mimicking disorders and to guide genetic testing. The aim of this study is to investigate the presence of possible patterns of morphostructural MRI findings that may provide relevant clues for a specific genetic HSP subtype. In our cohort, for example, white matter abnormalities were the most common finding followed by the thinning of the corpus callosum, which, interestingly, presented different thinning characteristics depending on the HSP subtype.

Clinical and genetic update of hereditary spastic paraparesis

Hereditary spastic paraparesis is a group of inherited neurological diseases characterized by underlying wide genetic heterogeneity. It should be suspected if there is a positive familial history, a common genetic alteration (i.e. SPG4, the most overall frequent form), or association with other signs, such as cerebellar ataxia (i.e. SPG7), early cognitive impairment or even cognitive deficit (i.e. SPG11), or peripheral neuropathy (i.e. SACS). The natural history is known for certain genetic subgroups, with genotype-phenotype correlations partially explaining childhood or late onset. However, the search for genetic modifying factors, in addition to the causal pathogenic variant or environmental influencers, is still needed. Novel approaches to provide etiological treatment are in the pipeline for SPG11. Symptomatic treatments are available but would benefit from randomized controlled trials.

A new paraplegin mutation in a patient with primary progressive multiple sclerosis

Primary progressive multiple sclerosis (PPMS) presents with clinical signs of slowly progressive long tract dysfunction that can overlap with neurodegenerative disorders, such as hereditary spastic paraplegia (HSP). Herein, we present two siblings in whom we have identified a novel mutation in the paraplegin (SPG7) gene. The proband, a 49-year-old woman, presented with a five-year history of progressive spastic paraparesis and ataxia. Brain MRI showed mild cerebellar atrophy. The genetic study revealed a homozygous mutation in the SPG7 gene, that led to the diagnosis of HSP. Four years previously, the younger brother had complained of slowly progressive spastic-ataxic gait, that started one year before; MRI had disclosed multiple areas of white matter hyperintensity with contrast enhancement. A diagnosis of active PPMS was made, and the patient started Disease-Modifying Therapy with further clinical and radiological stability. Once a genetic diagnosis was achieved in his sister, the patient underwent SPG7 testing, which disclosed the same mutation. Whether MS is a mimicry of HSP or it represents "double trouble" condition in this patient, it remains undetermined.

Genotype-phenotype correlations of adult-onset PLA2G6-associated Neurodegeneration: case series and literature review

Background

Phospholipase A2 group VI (PLA2G6) mutations associated with neurodegeneration (PLAN) manifest as heterogeneous neurodegenerative disorders with variable ages of onset. The genotype-phenotype correlation is not well-established. We aim to describe three adult patients with PLAN and combined these data with results from previous studies to elucidate adult-onset PLA2G6 phenotype-genotype correlations.

Case presentations

The first index patient presented with dystonia-parkinsonism starting at age 31 years, accompanied by major depression and cognitive decline. Genetic analysis using targeted next generation sequencing (NGS) panel, Sanger sequencing, and segregation analyses revealed a compound heterozygous mutation, c.991G > T (p.D331Y)/c.1077G > A (M358IfsX), in PLA2G6. The other two patients had levodopa-responsive, early-onset parkinsonism, starting in their late twenties. Both patients had homozygous c.991G > T (p.D331Y) mutations in PLA2G6. Patient characteristics of our reported 3 cases were compared to those of 32 previously described (2008 to 2019) patients with adult-onset PLAN. Among the combined cohort of 35 patients with adult-onset PLAN, 14 had dystonia-parkinsonism, 17 had early-onset Parkinson’s disease, 3 had hereditary spastic paraparesis, and one had ataxia. The c.991G > T (p. D331Y) mutation was almost exclusively found in Chinese patients, suggesting a common founder effect. All patients with homozygous p.D331Y mutations had levodopa-responsive, early-onset PD (100%); while other mutations mostly led to dystonia-parkinsonism, ataxia, spasticity, and combine psychiatric comorbidities.

Conclusions

We showed that adult-onset PLAN could present as purely parkinsonism features, without brain iron accumulation, particularly patients with homozygous p.D331Y mutations. Compound heterozygous mutations, including heterozygous p.D331Y, produced heterogeneous phenotypes, without obvious levodopa responsiveness.

Postural stability during gait for adults with hereditary spastic paraparesis

Individuals with hereditary spastic paraparesis (HSP) are often impaired in their ability to control posture as a result of the neurological and musculoskeletal implications of their condition. This research aimed to assess postural stability during gait in a group of adults with HSP. Ten individuals with HSP and 10 healthy controls underwent computerized gait analysis while walking barefoot along a 10-m track. Two biomechanics methods were used to assess stability: the center of pressure and center of mass separation (COP-COM) method, and the extrapolated center of mass (XCOM) method. Spatiotemporal and kinematic variables were also investigated. The XCOM method identified deficits in mediolateral stability for the HSP group at both heel strike and mid-stance. The group with HSP also had slower walking velocity, lower cadence, more time spent in double stance, larger step widths, and greater lateral trunk flexion than the control group. These results suggest that individuals with HSP adjust characteristics of their gait to minimize the instability arising from their impairments but have residual deficits in mediolateral stability. This may result in an increased risk of falls, particularly in the sideways direction.

SLC2A1 mutations are a rare cause of pediatric-onset hereditary spastic paraplegia

SLC2A1 mutations cause glucose transporter type 1 deficiency syndrome, whose phenotypic spectrum is a continuum, ranging from classic to variant phenotypes, the latter accounting for about 10% of cases. Very few SLC2A1-mutated patients with a spastic paraplegia phenotype have been reported so far, and they are associated with paroxysmal choreo-athetosis (i.e., DYT9). The authors describe two sporadic children with pure and complex hereditary spastic paraplegia (HSP) without paroxysmal non-epileptic movement disorders harboring heterozygous de novo SLC2A1 pathogenic variants. These patients have been identified by a targeted panel for HSP among 140 pediatric- and adult-onset unrelated cases with pure and complex HSP, thus indicating an overall prevalence of 1.4% of SLC2A1 mutations, which increases to 3% if only pediatric-onset patients are considered. The implications of these findings in the diagnostic work-up of HSP patients are discussed.

Cerebrospinal Fluid Neurofilaments May Discriminate Upper Motor Neuron Syndromes: A Pilot Study

BACKGROUND

Patients presenting with upper motor neuron (UMN) signs may widely diverge in prognosis, ranging from amyotrophic lateral sclerosis (ALS) to primary lateral sclerosis (PLS) and hereditary spastic paraplegia (hSP). Neurofilaments are emerging as potential diagnostic and prognostic biomarkers for ALS, but the diagnosis of UMN syndromes still relies mostly on clinical long-term observation and on familiarity or genetic confirmation.

OBJECTIVES

To test whether phosphorylated neurofilament heavy chain (pNfH) may discriminate different UMN syndromes at diagnosis and to test their prognostic role among these diseases.

METHODS

We measured the cerebrospinal fluid (CSF) and serum pNfH of 30 patients presenting with UMN signs and diagnosed with ALS, hSP, and PLS, plus 9 healthy controls (HC).

RESULTS

ALS patients had higher levels of pNfH in CSF and serum compared to HC (p < 0.001 and p < 0.001 in CSF and serum, respectively) and PLS (p = 0.015 and p = 0.038) and hSP (p = 0.003 and p = 0.001) patients. PLS and hSP patients had similar CSF and serum pNfH concentrations, but a higher CSF pNfH concentration, compared to HC (p = 0.002 and p = 0.003 for PLS and hSP, respectively). Receiver operating characteristic curves for discriminating ALS from PLS and hSP showed an area under the curve of 0.79 for CSF and 0.81 for serum. In multivariable survival analysis including relevant clinical factors CSF pNfH represented the strongest variable predicting survival (HR 40.43; 95% CI 3.49-467.79, p = 0.003) independently of clinical group.

CONCLUSIONS

Despite some statistical instability of the results due to limitations in sample size, our study supports the role of CSF pNfH as a prognostic biomarker for motor neuron diseases presenting with UMN signs. A potential power to discriminate between ALS and other UMN syndromes at presentation, and between all of the examined MND and HC, has been detected for both CSF and serum pNfH.

Three novel mutations in 20 patients with hereditary spastic paraparesis

Hereditary spastic paraparesis (HSP) constitutes both genetic and clinically heterogeneous group of upper motor neuron diseases. Half of the individuals with autosomal dominant (AD) HSP have mutations in SPAST, ATL1, and REEP1 genes. This study was conducted to elucidate the genetic etiology of patients with the pure type AD-HSP diagnosis. The patient group consisted of 23 individuals from 6 families in Turkey. In the first step of work, Sanger sequencing (SS) was performed in ATL1, SPAST, and REEP1 genes and the second phase whole-exome sequencing (WES) was performed following SS analysis for the patients with no detected mutations in these genes. The results of this study revealed that in ATL1, 6 patients have previously reported c.776C > A mutation and 6 patients have novel c.470 T > C mutation. In SPAST, 3 patients have novel c.1072G > C mutation and 2 patients have novel c.1099-1G > C mutation. WES was performed in three patients, who had no detected mutation in these genes with SS analysis. In this approach, as previously reported c.1859 T > C mutation in KIAA0196 was detected, and it was confirmed with the patient's relatives by SS. In three of patients, no HSP-associated variant could be identified in SS and WES. With this study, the molecular genetic etiology in 20 of 23 (87%) individuals that were included in this study with the utilization of SS and WES was elucidated. Utilization of SS and WES methods have enabled the identification of genetic etiology of HSP further with appropriate genetic counseling that was provided to the patients.

Increased lower limb muscle coactivation reduces gait performance and increases metabolic cost in patients with hereditary spastic paraparesis

BACKGROUND

The aim of this study was to investigate the lower limb muscle coactivation and its relationship with muscles spasticity, gait performance, and metabolic cost in patients with hereditary spastic paraparesis.

METHODS

Kinematic, kinetic, electromyographic and energetic parameters of 23 patients and 23 controls were evaluated by computerized gait analysis system. We computed ankle and knee antagonist muscle coactivation indexes throughout the gait cycle and during the subphases of gait. Energy consumption and energy recovery were measured as well. In addition to the correlation analysis between coactivation indexes and clinical variables, correlations between coactivation indexes and time-distance, kinematic, kinetic, and energetic parameters were estimated.

FINDINGS

Increased coactivity indexes of both knee and ankle muscles throughout the gait cycle and during the subphases of gait were observed in patients compared with controls. Energetic parameters were significantly higher in patients than in controls. Both knee and ankle muscle coactivation indexes were positively correlated with knee and ankle spasticity (Ashworth score), respectively. Knee and ankle muscle coactivation indexes were both positively correlated with energy consumption and both negatively correlated with energy recovery.

INTERPRETATION

Positive correlations between the Ashworth score and lower limb muscle coactivation suggest that abnormal lower limb muscle coactivation in patients with hereditary spastic paraparesis reflects a primary deficit linked to lower limb spasticity. Furthermore, these abnormalities influence the energetic mechanisms during walking. Identifying excessive muscle coactivation may be helpful in individuating the rehabilitative treatments and designing specific orthosis to restrain spasticity.

Hereditary Spastic Paraplegia: Clinical and Genetic Hallmarks

Hereditary spastic paraplegia comprises a wide and heterogeneous group of inherited neurodegenerative and neurodevelopmental disorders resulting from primary retrograde dysfunction of the long descending fibers of the corticospinal tract. Although spastic paraparesis and urinary dysfunction represent the most common clinical presentation, a complex group of different neurological and systemic compromise has been recognized recently and a growing number of new genetic subtypes were described in the last decade. Clinical characterization of individual and familial history represents the main step during diagnostic workup; however, frequently, few and unspecific data allows a low rate of definite diagnosis based solely in clinical and neuroimaging basis. Likewise, a wide group of neurological acquired and inherited disorders should be included in the differential diagnosis and properly excluded after a complete laboratorial, neuroimaging, and genetic evaluation. The aim of this review article is to provide an extensive overview regarding the main clinical and genetic features of the classical and recently described subtypes of hereditary spastic paraplegia (HSP).

SPG2 mimicking multiple sclerosis in a family identified using next generation sequencing

Several single gene disorders can potentially be overlooked in the differential diagnostic evaluation of patients with multiple sclerosis (MS). Pelizaeus-Merzbacher disease and spastic paraplegia type 2 are allelic X-linked disorders associated with defective myelination of the central nervous system and mutations in PLP1. Neurological symptoms are occasionally observed in female carriers of these mutations. Two women - the proposita (Pt1) and her mother (Pt2) - reported walking difficulties since adolescence and showed progressive cognitive decline. Their neurological examinations revealed spastic gait, pyramidal tract involvement and distal muscle atrophy in the legs. Peripheral neuropathy and diffuse white matter (WM) changes on brain MRI were also observed. Both patients had a preliminary diagnosis of primary progressive MS. Using a targeted method in next generation sequencing, the novel heterozygous c.210T>G/p.Y70* in PLP1 was identified in Pt2. The same mutation was also found in Pt1 but not in five healthy relatives. The mutation showed moderate-to-severe skewed X inactivation in tissues, and Western blotting revealed a significant reduction of PLP1 and DM20 in the sural nerve of Pt2. In conclusion a mother and daughter presented an X-linked dominant disorder with skewed X inactivation. The authors suggest that PLP1 testing might be considered in the evaluation of women with spastic paraparesis, cognitive decline and WM changes.

TECPR2 mutations cause a new subtype of familial dysautonomia like hereditary sensory autonomic neuropathy with intellectual disability

BACKGROUND

TECPR2 was first described as a disease causing gene when the c.3416delT frameshift mutation was found in five Jewish Bukharian patients with similar features. It was suggested to constitute a new subtype of complex hereditary spastic paraparesis (SPG49).

RESULTS

We report here 3 additional patients from unrelated non-Bukharian families, harboring two novel mutations (c.1319delT, c.C566T) in this gene. Accumulating clinical data clarifies that in addition to intellectual disability and evolving spasticity the main disabling feature of this unique disorder is autonomic-sensory neuropathy accompanied by chronic respiratory disease and paroxysmal autonomic events.

CONCLUSION

We suggest that the disease should therefore be classified as a new subtype of hereditary sensory-autonomic neuropathy. The discovery of additional mutations in non-Bukharian patients implies that this disease might be more common than previously appreciated and should therefore be considered in undiagnosed cases of intellectual disability with autonomic features and respiratory symptoms regardless of demographic origin.

The effect of hydrotherapy treatment on gait characteristics of hereditary spastic paraparesis patients

BACKGROUND

Hereditary spastic paraparesis (HSP) is a group of neurological disorders characterised by slowly progressive increasing muscle tone, predominantly in the lower limbs, with relatively preserved power. This leads to progressive difficulties in motor control and walking.

OBJECTIVE

The purpose of this study was to evaluate the effectiveness of hydrotherapy treatment when used as a means to increase locomotor function in individuals with late onset HSP. This paper discusses the analysis of the effect on gait characteristics.

METHODS

Nine people with HSP were asked to participate in pre- and post-hydrotherapy gait analyses. Ground reaction force and motion trajectories were recorded and used to calculate spatiotemporal gait parameters, joint angles and moments.

RESULTS

The normalised joint kinematics and kinetics profile revealed that the biomechanics of people with HSP were similar to that of controls for most of the joints, but with lower range of motion. Walking speed increased significantly (11%) after the course of hydrotherapy. Though part of this was achieved through increased ROM there was also a further increase in hip internal rotation and in peak hip extension moment.

CONCLUSIONS

Although participants had increased walking speed and step length, it appears that hydrotherapy increases the ability to perform compensatory strategies rather than resulting in a more typical kinematic and kinetic approach.

A clinical and genetic perspective from Tuscany

OBJECTIVE

Hereditary spastic paraparesis or paraplegias (HSPs) are a group of neurogenetic conditions with prominent involvement of the pyramidal tracts. Aim of this study is the clinical and molecular characterization of a cohort of patients with HSP. Moreover, we aim to study the minimum prevalence of HSP in our area and to propose a schematic diagnostic approach to HSP patients based on the available data from the literature.

METHODS

Retrospective/perspective study on the subjects with clinical signs and symptoms indicative of pure or complicated HSP, in whom other possible diagnosis were excluded by appropriate neuroradiological, neurophysiologic and laboratory studies, who have been evaluated by the Neurogenetic Service of our Clinic in last two years (2011-2012).

RESULTS

45 patients were identified. The minimum prevalence of HSP in our area was of about 2.17-3.43/100,000. The SF-36 (quality of life) and SPRS (disease progression) scores were inversely related; the time-saving, four-stage scale of motor disability could predict the SPRS scores with a high statistical significance, and we encourage its use in HSP. Our study confirms SPG4 as the major cause of HSP. All SPG4 patients had a pure HSP phenotype, and the dominant inheritance was evident in the great majority of these subjects. SPG7 was the second genetic cause. Other genotypes were rarer (SPG10, SPG11, SPG17).

CONCLUSION

Exact molecular diagnosis will allow a more accurate patient counseling and, hopefully, will lead to specific, targeted, therapeutic options for these chronic, still incurable diseases.

Balance dysfunction in hereditary and spontaneous spastic paraparesis

OBJECTIVE

To determine how postural sway is affected in people with spastic paraparesis (pwSP) and the impact of different impairments.

METHODS

In 20 pwSP and 18 matched healthy controls standing postural sway was measured with eyes open and closed. Vibration threshold, isometric ankle and hip muscle strength and ankle stiffness with the participant at rest or preactivating the muscle was measured.

RESULTS

Antero-posterior (AP) and medio-lateral (ML) sway was higher in pwSP. Muscle strength was reduced and ankle stiffness increased in pwSP. Increased vibratory threshold was seen in 35% of participants. Higher total ankle stiffness (R2=0.44) was associated with lower AP sway with eyes open whilst hip abductor weakness was associated with increased ML sway with eyes open (R2=0.36) or closed (R2=0.47) or AP sway with the eyes closed (R2=0.48).

CONCLUSIONS

The degree of postural sway was related to muscle paresis of the hip abductors particularly in the ML direction and under conditions of reduced sensory input. People with higher total ankle stiffness have less AP sway suggesting that this may help to stabilise the body.

Does calf muscle spasticity contribute to postural imbalance? A study in persons with pure hereditary spastic paraparesis

OBJECTIVES

The contribution of spasticity to postural imbalance in patients with upper motor neuron syndrome is still unclear. This study aimed to evaluate the responses to support-surface perturbations in patients with hereditary spastic paraparesis (HSP). These patients typically suffer from bilateral spasticity with relatively preserved muscle strength of the lower limbs. Particularly toes-up rotations were expected to be destabilizing due to insufficient suppression of calf muscle stretch reflexes.

METHODS

Participants were seventeen symptomatic community-dwelling patients with autosomal dominant pure HSP and seventeen healthy controls. All patients had increased muscle tone of the triceps surae (TS) but no muscle contractures. Perturbations were applied by rotating or translating a platform with increasing intensity in four sagittal-plane directions. The primary outcome was maximum intensity ('limit of stability') sustained without stepping or grabbing in each type of perturbation. Leg muscle tone and strength were assessed with the Modified Ashworth Scale and Medical Research Council (MRC) scale, respectively.

RESULTS

For toes-up perturbations, limits of stability in patients were substantially lower than in controls, which were related to TS muscle tone but not to tibialis anterior (TA) strength. Toes-down rotations were indiscriminative. For backward perturbations, patients also had lower limits of stability, unrelated to TA strength or TS muscle tone. In forward perturbations, patients with TS strength MRC 4 were less stable than patients with normal TS strength and controls.

CONCLUSION

Calf muscle spasticity and weakness differently contribute to postural imbalance in patients with HSP. This notion could have implications for the clinical management of spasticity.