Evolution of structural neuroimaging biomarkers in a series of adult patients with Niemann-Pick type C under treatment

Characterization of central manifestations in patients with Niemann-Pick disease type C

PURPOSE

Niemann-Pick disease type C (NPC) is a rare lysosomal storage disease characterized by progressive neurodegeneration and neuropsychiatric symptoms. This study investigated pathophysiological mechanisms underlying motor deficits, particularly speech production, and cognitive impairment.

METHODS

We prospectively phenotyped 8 adults with NPC and age-sex-matched healthy controls using a comprehensive assessment battery, encompassing clinical presentation, plasma biomarkers, hand-motor skills, speech production, cognitive tasks, and (micro-)structural and functional central nervous system properties through magnetic resonance imaging.

RESULTS

Patients with NPC demonstrated deficits in fine-motor skills, speech production timing and coordination, and cognitive performance. Magnetic resonance imaging revealed reduced cortical thickness and volume in cerebellar subdivisions (lobule VI and crus I), cortical (frontal, temporal, and cingulate gyri) and subcortical (thalamus and basal ganglia) regions, and increased choroid plexus volumes in NPC. White matter fractional anisotropy was reduced in specific pathways (intracerebellar input and Purkinje tracts), whereas diffusion tensor imaging graph theory analysis identified altered structural connectivity. Patients with NPC exhibited altered activity in sensorimotor and cognitive processing hubs during resting-state and speech production. Canonical component analysis highlighted the role of cerebellar-cerebral circuitry in NPC and its integration with behavioral performance and disease severity.

CONCLUSION

This deep phenotyping approach offers a comprehensive systems neuroscience understanding of NPC motor and cognitive impairments, identifying potential central nervous system biomarkers.

The Niemann-Pick type diseases – A synopsis of inborn errors in sphingolipid and cholesterol metabolism

Disturbances of lipid homeostasis in cells provoke human diseases. The elucidation of the underlying mechanisms and the development of efficient therapies represent formidable challenges for biomedical research. Exemplary cases are two rare, autosomal recessive, and ultimately fatal lysosomal diseases historically named "Niemann-Pick" honoring the physicians, whose pioneering observations led to their discovery. Acid sphingomyelinase deficiency (ASMD) and Niemann-Pick type C disease (NPCD) are caused by specific variants of the sphingomyelin phosphodiesterase 1 (SMPD1) and NPC intracellular cholesterol transporter 1 (NPC1) or NPC intracellular cholesterol transporter 2 (NPC2) genes that perturb homeostasis of two key membrane components, sphingomyelin and cholesterol, respectively. Patients with severe forms of these diseases present visceral and neurologic symptoms and succumb to premature death. This synopsis traces the tortuous discovery of the Niemann-Pick diseases, highlights important advances with respect to genetic culprits and cellular mechanisms, and exposes efforts to improve diagnosis and to explore new therapeutic approaches.

Targeting neurological abnormalities in lysosomal storage diseases

Central nervous system (CNS) abnormalities and corresponding neurological and psychiatric symptoms are frequently observed in lysosomal storage disorders (LSDs). The genetic background of individual LSDs is indeed unique to each illness. However, resulting defective lysosomal function within the CNS can transition normal cellular processes (i.e., autophagy) into aberrant mechanisms, facilitating overlapping downstream consequences including neurocircuitry dysfunction, neurodegeneration as well as sensory, motor, cognitive, and psychological symptoms. Here, the neurological and biobehavioral phenotypes of major classes of LSDs are discussed alongside therapeutic strategies in development that aim to tackle neuropathology among other disease elements. Finally, focused ultrasound blood-brain barrier opening is proposed to enhance therapeutic delivery thereby overcoming the key hurdle of central distribution of disease modifying therapies in LSDs.

International consensus on clinical severity scale use in evaluating Niemann-Pick disease Type C in paediatric and adult patients: results from a Delphi Study

Background

Several scales have been developed in the past two decades to evaluate Niemann–Pick disease Type C (NPC) severity in clinical practice and trials. However, a lack of clarity concerning which scale to use in each setting is preventing the use of standardised assessments across the world, resulting in incomparable data sets and clinical trial outcome measures. This study aimed to establish agreed approaches for the use of NPC severity scales in clinical practice and research.

Methods

A Delphi method of consensus development was used, comprising three survey rounds. In Round 1, participants were asked nine multiple-choice and open-ended questions to gather opinions on the six severity scales and domains. In Rounds 2 and 3, questions aimed to gain consensus on the opinions revealed in Round 1 using a typical Likert scale.

Results

Nineteen experts, active in NPC paediatric and adult research and treatment, participated in this study. Of these, 16/19 completed Rounds 1 and 2 and 19/19 completed Round 3. Consensus (defined as ≥ 70% agreement or neutrality, given the study aim to identify the severity scales that the clinical community would accept for international consistency) was achieved for 66.7% of the multiple-choice questions in Round 2 and 83% of the multiple-choice questions in Round 3. Consensus was almost reached (68%) on the use of the 5-domain NPCCSS scale as the first choice in clinical practice. Consensus was reached (74%) for the 17-domain NPCCSS scale as the first choice in clinical trial settings, but the domains measured in the 5-domain scale should be prioritised as the primary endpoints. Experts called for educational and training materials on how to apply the NPCCSS (17- and 5-domains) for clinicians working in NPC.

Conclusions

In achieving a consensus on the use of the 17-domain NPCCSS scale as the first choice for assessing clinical severity of NPC in clinical trial settings but prioritising the domains in the 5-domain NPCCSS scale for routine clinical practice, this study can help to inform future discussion around the use of the existing NPC clinical severity scales. For routine clinical practice, the study helps provide clarity on which scale is favoured by a significant proportion of a representative body of experts, in this case, the 5-domain NPCCSS scale.

Neurodegeneration in Niemann-Pick Type C Disease: An Updated Review on Pharmacological and Non-Pharmacological Approaches to Counteract Brain and Cognitive Impairment

Niemann–Pick type C (NPC) disease is an autosomal recessive storage disorder, characterized by abnormal sequestration of unesterified cholesterol in the late endo-lysosomal system of cells. Progressive neurological deterioration and the onset of symptoms, such as ataxia, seizures, cognitive decline, and severe dementia, are pathognomonic features of the disease. In addition, different pathological similarities, including degeneration of hippocampal and cortical neurons, hyperphosphorylated tau, and neurofibrillary tangle formation, have been identified between NPC disease and other neurodegenerative pathologies. However, the underlying pathophysiological mechanisms are not yet well understood, and even a real cure to counteract neurodegeneration has not been identified. Therefore, the combination of current pharmacological therapies, represented by miglustat and cyclodextrin, and non-pharmacological approaches, such as physical exercise and appropriate diet, could represent a strategy to improve the quality of life of NPC patients. Based on this evidence, in our review we focused on the neurodegenerative aspects of NPC disease, summarizing the current knowledge on the molecular and biochemical mechanisms responsible for cognitive impairment, and suggesting physical exercise and nutritional treatments as additional non-pharmacologic approaches to reduce the progression and neurodegenerative course of NPC disease.

Brain hypometabolic changes in 14 adolescent-adult patients with Niemann-Pick disease type C assessed by 18F-fluorodeoxyglucose positron emission tomography

OBJECTIVE

Niemann Pick disease type C (NPC) is a rare progressive neurovisceral lysosomal disorder caused by autosomal recessive mutations in the NPC1 or NPC2 genes. 18F-fluorodeoxyglucose (FDG) is a positron-emitting glucose analogue for non-invasive imaging of brain metabolism. FDG PET is commonly used for dementia imaging but its specific application to NPC is rarely described.

METHODS

This is a retrospective study of all baseline brain FDG PET performed for NPC patients. Images were assessed using a normal database statistical comparison of metabolic changes expressed in standard deviations and three-dimensional Stereotactic Surface Projection maps. Typical hypometabolic patterns in NPC were identified. We further investigated any correlation between the degree of regional brain hypometabolism and the Iturriaga clinical severity scale.

RESULTS

Brain FDG PET images of 14 adolescent-adult NPC patients were analysed, with mean age of 35 years. We found significant frontal lobe hypometabolism in 12 patients (86%), thalamic hypometabolism in eight patients (57%) and variable parietal lobe hypometabolism in 13 patients (93%). Hypometabolic changes were usually bilateral and symmetric. Ten out of 13 ataxic patients showed cerebellar or thalamic hypometabolism (sensitivity 77%, specificity 100%). Linear regression analysis showed frontal lobe hypometabolism to have the best correlation with the Iturriaga clinical scale (R² = 0.439; p = 0.01).

CONCLUSIONS

We found bilateral symmetric hypometabolism of the frontal lobes, thalami and parietal lobes (especially posterior cingulate gyrus) to be typical of adolescent-adult NPC. Ataxia was commonly associated with cerebellar or thalamic hypometabolism. Frontal lobe hypometabolism showed the best inverse correlation with clinical severity.

Do heterozygous mutations of Niemann-Pick type C predispose to late-onset neurodegeneration: a review of the literature

BACKGROUND/METHODS

Monogenic diseases are important models for the study of neurodegenerative diseases, such as Parkinson's disease (PD) and dementia. Notably, for some disorders, homozygosity is associated with a complex metabolic disease, while heterozygosity predisposes to late-onset neurodegeneration. For instance, biallelic glucocerebrosidase gene mutations cause Gaucher's disease, while heterozygous mutations are a common genetic risk factor for late-onset PD. Little is known about similar risks of related diseases, such as Niemann-Pick type C (NPC). Given that both conditions map into related, i.e., lysosomal, pathways, we hypothesize a similar risk of single-NPC gene mutations. Indeed, there is increasing evidence based on clinical observations in humans and animal studies. Here we review the current knowledge of NPC heterozygosity.

RESULTS

Family history studies suggest a high proportion of late-onset neurodegenerative diseases in NPC families. We identified 19 cases with heterozygous NPC mutations in the literature who presented with a neurodegenerative disease, including levodopa-responsive PD, atypical parkinsonism (PSP, CBD), dystonia or dementia with a mean age at onset of about 57 years (range 8-87). Consistent splenomegaly and mildly abnormal filipin staining results have also been reported in heterozygous gene mutation carriers. Imaging and pathological data support this notion.

DISCUSSION/CONCLUSION

This finding has wider implications in so far as NPC-related forms of Parkinsonian syndromes, dementia, motor neuron disease and other neurodegenerative disorders may benefit from NPC-mechanistic therapies, in particular related to lysosomal dysfunction. Further research is warranted to generate systematic data of heterozygous mutation carriers, including longitudinal data.

Phenotype, treatment practice and outcome in the cobalamin-dependent remethylation disorders and MTHFR deficiency: Data from the E-HOD registry

AIM

To explore the clinical presentation, course, treatment and impact of early treatment in patients with remethylation disorders from the European Network and Registry for Homocystinurias and Methylation Defects (E-HOD) international web-based registry.

RESULTS

This review comprises 238 patients (cobalamin C defect n = 161; methylenetetrahydrofolate reductase deficiency n = 50; cobalamin G defect n = 11; cobalamin E defect n = 10; cobalamin D defect n = 5; and cobalamin J defect n = 1) from 47 centres for whom the E-HOD registry includes, as a minimum, data on medical history and enrolment visit. The duration of observation was 127 patient years. In 181 clinically diagnosed patients, the median age at presentation was 30 days (range 1 day to 42 years) and the median age at diagnosis was 3.7 months (range 3 days to 56 years). Seventy-five percent of pre-clinically diagnosed patients with cobalamin C disease became symptomatic within the first 15 days of life. Total homocysteine (tHcy), amino acids and urinary methylmalonic acid (MMA) were the most frequently assessed disease markers; confirmatory diagnostics were mainly molecular genetic studies. Remethylation disorders are multisystem diseases dominated by neurological and eye disease and failure to thrive. In this cohort, mortality, thromboembolic, psychiatric and renal disease were rarer than reported elsewhere. Early treatment correlates with lower overall morbidity but is less effective in preventing eye disease and cognitive impairment. The wide variation in treatment hampers the evaluation of particular therapeutic modalities.

CONCLUSION

Treatment improves the clinical course of remethylation disorders and reduces morbidity, especially if started early, but neurocognitive and eye symptoms are less responsive. Current treatment is highly variable. This study has the inevitable limitations of a retrospective, registry-based design.

Psychiatric and Cognitive Symptoms Associated with Niemann-Pick Type C Disease: Neurobiology and Management

Niemann-Pick disease type C (NPC) is a lysosomal storage disorder that presents with a spectrum of clinical manifestations from infancy and childhood or in early or mid-adulthood. Progressive neurological symptoms including ataxia, dystonia and vertical gaze palsy are a hallmark of the disease, and psychiatric symptoms such as psychosis and mood disorders are common. These latter symptoms often present early in the course of NPC and thus these patients are often diagnosed with a major psychotic or affective disorder before neurological and cognitive signs present and the diagnosis is revised. The commonalities and characteristics of psychotic symptoms in both NPC and schizophrenia may share neuronal pathways and mechanisms and provide potential targets for research in both disorders. The neurobiology of NPC and its relationship to the pattern of neuropsychiatric and cognitive symptoms is described in this review. A number of neurobiological models are proposed as mechanisms by which NPC causes psychiatric and cognitive symptoms, informed from models proposed in schizophrenia and other metabolic disorders. There are a number of symptomatic and illness-modifying treatments for NPC currently available. The current evidence is discussed; focussing on two medications which have shown promise, miglustat and hydroxypropyl-β-cyclodextrin.

Neuroimaging Findings in Lysosomal Disorders: 2018 Update

Lysosomal storage disorders are a heterogeneous group of genetic diseases characterized by defective function in one of the lysosomal enzymes. In this review paper, we describe neuroradiological findings and clinical characteristics of neuronopathic lysosomal disorders with a focus on differential diagnosis. New insights regarding pathogenesis and therapeutic perspectives are also briefly discussed.

Treatment with chenodeoxycholic acid in cerebrotendinous xanthomatosis: clinical, neurophysiological, and quantitative brain structural outcomes

BACKGROUND

Cerebrotendinous xanthomatosis (CTX) is a rare neurodegenerative disease related to sterols metabolism. It affects both central and peripheral nervous systems but treatment with chenodeoxycholic acid (CDCA) has been reported to stabilize clinical scores and improve nerve conduction parameters. Few quantitative brain structural studies have been conducted to assess the effect of CDCA in CTX.

METHODS AND RESULTS

We collected retrospectively clinical, neurophysiological, and quantitative brain structural data in a cohort of 14 patients with CTX treated by CDCA over a mean period of 5 years. Plasma cholestanol levels normalized under treatment with CDCA within a few months. We observed a significant clinical improvement in patients up to 25 years old, whose treatment was initiated less than 15 years after the onset of neurological symptoms. Conversely, patients whose treatment was initiated more than 25 years after neurological disease onset continued their clinical deterioration. Eleven patients presented with a length-dependent peripheral neuropathy, whose electrophysiological parameters improved significantly under CDCA. Volumetric analyses in a subset of patients showed no overt volume loss under CDCA. Moreover, diffusion weighted imaging showed improved fiber integrity of the ponto-cerebellar and the internal capsule with CDCA. CDCA was well tolerated in all patients with CTX.

CONCLUSION

CDCA may reverse the pathophysiological process in patients with CTX, especially if treatment is initiated early in the disease process. Besides tendon xanthoma, this study stresses the need to consider plasma cholestanol measurement in any patient with infantile chronic diarrhea and/or jaundice, juvenile cataract, learning disability and/or autism spectrum disorder, pyramidal signs, cerebellar syndrome or peripheral neuropathy.

Reduced Intracranial Volume in Fabry Disease: Evidence of Abnormal Neurodevelopment?

Introduction: Lysosomal storage disorders (LSD) are often characterized by abnormal brain development, reflected by a reduction of intracranial volume (ICV). The aim of our study was to perform a volumetric analysis of intracranial tissues in Fabry Disease (FD), investigating possible reductions of ICV as a potential expression of abnormal brain development in this condition.

Materials and Methods: Forty-two FD patients (15 males, mean age 43.3 ± 13.0 years) were enrolled along with 38 healthy controls (HC) of comparable age and sex. Volumetric MRI data were segmented using SPM12 to obtain intracranial tissue volumes, from which ICV values were derived.

Results: Mean ICV of FD patients was 8.1% smaller compared to the control group (p < 5·10⁻⁵). Unlike what typically happens in neurodegenerative disorders, no significant differences emerged when comparing between the two groups the fractional volumes of gray matter, white matter and CSF (i.e., normalized by ICV), consistent with a harmonious volumetric reduction of intracranial structures.

Discussion: The present results suggest that in FD patients an abnormality of brain development is present, expanding the current knowledge about central nervous system involvement in FD, further emphasizing the importance of an early diagnosis.

Miglustat in Niemann-Pick disease type C patients: a review

OBJECTIVE

Niemann-Pick disease type C (NP-C) is a rare, autosomal recessive, neurodegenerative disease associated with a wide variety of progressive neurological manifestations. Miglustat is indicated for the treatment of progressive neurological manifestations in both adults and children. Since approval in 2009 there has been a vast growth in clinical experience with miglustat. The effectiveness of miglustat has been assessed using a range of measures.

METHODS

Comprehensive review of published data from studies of cellular neuropathological markers and structural neurological indices in the brain, clinical impairment/disability, specific clinical neurological manifestations, and patient survival.

RESULTS

Cranial diffusion tensor imaging and magnetic resonance spectroscopy studies have shown reduced levels of choline (a neurodegeneration marker), and choline/N-acetyl aspartate ratio (indicating increased neuronal viability) in the brain during up to 5 years of miglustat therapy, as well as a slowing of reductions in fractional anisotropy (an axonal/myelin integrity marker). A 2-year immunoassay study showed significant reductions in CSF-calbindin during treatment, indicating reduced cerebellar Purkinje cell loss. Magnetic resonance imaging studies have demonstrated a protective effect of miglustat on cerebellar and subcortical structure that correlated with clinical symptom severity. Numerous cohort studies assessing core neurological manifestations (impaired ambulation, manipulation, speech, swallowing, other) using NP-C disability scales indicate neurological stabilization over 2-8 years, with a trend for greater benefits in patients with older (non-infantile) age at neurological onset. A randomized controlled trial and several cohort studies have reported improvements or stabilization of saccadic eye movements during 1-5 years of therapy. Swallowing was also shown to improve/remain stable during the randomized trial (up to 2 years), as well as in long-term observational cohorts (up to 6 years). A meta-analysis of dysphagia - a potent risk factor for aspiration pneumonia and premature death in NP-C - demonstrated a survival benefit with miglustat due to improved/stabilized swallowing function.

CONCLUSIONS

The effects of miglustat on neurological NP-C manifestations has been assessed using a range of approaches, with benefits ranging from cellular changes in the brain through to visible clinical improvements and improved survival.

Recent neuroimaging, neurophysiological, and neuropathological advances for the understanding of NPC

Niemann–Pick disease type C (NPC) is a rare autosomal recessive lysosomal storage disorder with extensive biological, molecular, and clinical heterogeneity. Recently, numerous studies have tried to shed light on the pathophysiology of the disease, highlighting possible disease pathways common to other neurodegenerative disorders, such as Alzheimer’s disease and frontotemporal dementia, and identifying possible candidate biomarkers for disease staging and response to treatment. Miglustat, which reversibly inhibits glycosphingolipid synthesis, has been licensed in the European Union and elsewhere for the treatment of NPC in both children and adults. A number of ongoing clinical trials might hold promise for the development of new treatments for NPC. The objective of the present work is to review and evaluate recent literature data in order to highlight the latest neuroimaging, neurophysiological, and neuropathological advances for the understanding of NPC pathophysiology. Furthermore, ongoing developments in disease-modifying treatments will be briefly discussed.

Metabolic ataxias

The nervous system is vulnerable to intrinsic and extrinsic metabolic perturbations. In particular, the cerebellum, with its large Purkinje cells and its high density of neurons and glial cells, has high metabolic demand and is highly vulnerable to metabolic derangements. As a result, many disorders of intermediary metabolism will preferentially and sometimes selectively target the cerebellum. However, many of these disorders present in a multisystem fashion with ataxia being a part of the neurologic symptom complex. The presentation of these disorders depends on the time of onset and type of metabolic derangement. Early infantile or intrauterine-onset diseases will present in a young child typically with global hypotonia and both nystagmus and ataxia become more apparent later in life, while later-onset diseases usually present primarily with ataxia. It is important to note that the majority of these disorders are progressive if they are untreated. This chapter provides a review of acquired and genetic metabolic disorders that target the cerebellum, and discusses their diagnostic evaluation and therapy.

Cognitive impairment profile in adult patients with Niemann pick type C disease

Background

Cognitive impairment is one of the core symptoms of Niemann Pick type C (NPC) disease, but few data concerning the neuropsychological profile of NPC patients are available. The aim of our study was to characterize cognitive impairments in NPC disease and to assess the evolution of these symptoms and the impact of miglustat on cognitive follow-up.

Methods

We conducted a retrospective study of 21 adult patients diagnosed with NPC disease. Neuropsychological data (global cognitive efficiency, language, attention, executive functions, praxis, and visuoconstructive functions tests) were retrieved to describe the cognitive profile of patients. Cognitive impairment scores over time were assessed under treatment by miglustat.

Results

The majority of patients (90%) were impaired in one or more cognitive function. Executive functions and attention were the most impaired cognitive functions. Conversely, storage in the episodic memory was preserved in 61.5% of cases. Mean neuropsychological scores were stable during the period under miglustat (mean of 3.8 years).

Conclusions

This study is one of the first to assess the cognitive profile of adult NPC patients. This profile is not specific to attention and executive dysfunctions; however, the preservation of storage in the episodic memory is promising for cognitive remediation. Further studies are needed to confirm the role of miglustat on cognition, but in this study, patients were stable under this treatment.

Patient with Niemann-Pick disease type C: over 20 years' follow-up

We report a 37-year-old woman with Niemann-Pick disease type C (NPC) 1. At the age of 8 years, she presented slow running followed by both fingers dystonia at the age of 10 years. At the age of 16 years, she developed declined scholastic achievement. On her first visit at the age of 17 years, she showed dystonia, ataxic gait and vertical supranuclear gaze palsy. We suspected it was NPC. She presented atrophies in the frontal lobes, brainstem and cerebellum in a brain MRI. She presented hepatomegalies and splenomegalies in an abdominal CT. At the age of 26 years, she undertook perpetually tracheal fistula because of recurrent aspiration pneumonia. Diagnosis of NPC1 was made by filipin staining and existence of foamy cells in the bone marrow and NPC1 gene analysis. We obtained informed consent of genetic analysis. Miglustat therapy was started at the age of 32 years. Improvements in swallowing capacity and in muscle tonus were seen.

Longitudinal Changes in White Matter Fractional Anisotropy in Adult-Onset Niemann-Pick Disease Type C Patients Treated with Miglustat

Niemann-Pick disease type C (NPC) is a rare neurometabolic disorder resulting in impaired intracellular lipid trafficking. The only disease-modifying treatment currently available is miglustat, an iminosugar that inhibits the accumulation of lipid metabolites in neurons and other cells. This longitudinal diffusion tensor imaging (DTI) study examined how the rate of white matter change differed between treated and non-treated adult-onset NPC patient groups. Nine adult-onset NPC patients (seven undergoing treatment with miglustat, two not treated) underwent DTI neuroimaging. Rates of change in white matter structure as indexed by Tract-Based Spatial Statistics (TBSS) of fractional anisotropy were compared between treated and untreated patients. Treated patients were found to have a significantly slower rate of white matter change in the corticospinal tracts, the thalamic radiation and the inferior longitudinal fasciculus. This is further evidence that miglustat treatment may have a protective effect on white matter structure in the adult-onset form of the disease.