Neurological aspects of human glycosylation disorders

This review presents principles of glycosylation, describes the relevant glycosylation pathways and their related disorders, and highlights some of the neurological aspects and issues that continue to challenge researchers. More than 100 rare human genetic disorders that result from deficiencies in the different glycosylation pathways are known today. Most of these disorders impact the central and/or peripheral nervous systems. Patients typically have developmental delays/intellectual disabilities, hypotonia, seizures, neuropathy, and metabolic abnormalities in multiple organ systems. Among these disorders there is great clinical diversity because all cell types differentially glycosylate proteins and lipids. The patients have hundreds of misglycosylated products, which afflict a myriad of processes, including cell signaling, cell-cell interaction, and cell migration. This vast complexity in glycan composition and function, along with the limited availability of analytic tools, has impeded the identification of key glycosylated molecules that cause pathologies. To date, few critical target proteins have been pinpointed.

A clinical approach to the diagnosis of patients with leukodystrophies and genetic leukoencephelopathies

Leukodystrophies (LD) and genetic leukoencephalopathies (gLE) are disorders that result in white matter abnormalities in the central nervous system (CNS). Magnetic resonance (MR) imaging (MRI) has dramatically improved and systematized the diagnosis of LDs and gLEs, and in combination with specific clinical features, such as Addison's disease in Adrenoleukodystrophy or hypodontia in Pol-III related or 4H leukodystrophy, can often resolve a case with a minimum of testing. The diagnostic odyssey for the majority LD and gLE patients, however, remains extensive--many patients will wait nearly a decade for a definitive diagnosis and at least half will remain unresolved. The combination of MRI, careful clinical evaluation and next generation genetic sequencing holds promise for both expediting the diagnostic process and dramatically reducing the number of unresolved cases. Here we present a workflow detailing the Global Leukodystrophy Initiative (GLIA) consensus recommendations for an approach to clinical diagnosis, including salient clinical features suggesting a specific diagnosis, neuroimaging features and molecular genetic testing. We also discuss recommendations on the use of broad-spectrum next-generation sequencing in instances of ambiguous MRI or clinical findings. We conclude with a proposal for systematic trials of genome-wide agnostic testing as a first line diagnostic in LDs and gLEs given the increasing number of genes associated with these disorders.

Consensus statement on preventive and symptomatic care of leukodystrophy patients

Leukodystrophies are inherited disorders whose primary pathophysiology consists of abnormal deposition or progressive disruption of brain myelin. Leukodystrophy patients manifest many of the same symptoms and medical complications despite the wide spectrum of genetic origins. Although no definitive cures exist, all of these conditions are treatable. This report provides the first expert consensus on the recognition and treatment of medical and psychosocial complications associated with leukodystrophies. We include a discussion of serious and potentially preventable medical complications and propose several preventive care strategies. We also outline the need for future research to prioritize clinical needs and subsequently develop, validate, and optimize specific care strategies.

Case definition and classification of leukodystrophies and leukoencephalopathies

OBJECTIVE

An approved definition of the term leukodystrophy does not currently exist. The lack of a precise case definition hampers efforts to study the epidemiology and the relevance of genetic white matter disorders to public health.

METHOD

Thirteen experts at multiple institutions participated in iterative consensus building surveys to achieve definition and classification of disorders as leukodystrophies using a modified Delphi approach.

RESULTS

A case definition for the leukodystrophies was achieved, and a total of 30 disorders were classified under this definition. In addition, a separate set of disorders with heritable white matter abnormalities but not meeting criteria for leukodystrophy, due to presumed primary neuronal involvement and prominent systemic manifestations, was classified as genetic leukoencephalopathies (gLE).

INTERPRETATION

A case definition of leukodystrophies and classification of heritable white matter disorders will permit more detailed epidemiologic studies of these disorders.

Disease specific therapies in leukodystrophies and leukoencephalopathies

Leukodystrophies are a heterogeneous, often progressive group of disorders manifesting a wide range of symptoms and complications. Most of these disorders have historically had no etiologic or disease specific therapeutic approaches. Recently, a greater understanding of the pathologic mechanisms associated with leukodystrophies has allowed clinicians and researchers to prioritize treatment strategies and advance research in therapies for specific disorders, some of which are on the verge of pilot or Phase I/II clinical trials. This shifts the care of leukodystrophy patients from the management of the complex array of symptoms and sequelae alone to targeted therapeutics. The unmet needs of leukodystrophy patients still remain an overwhelming burden. While the overwhelming consensus is that these disorders collectively are symptomatically treatable, leukodystrophy patients are in need of advanced therapies and if possible, a cure.

High-throughput Toroidal Grating Beamline for Photoelectron Spectroscopy at CAMD

A 5 meter toroidal grating (5m-TGM) beamline has been commissioned to deliver 28 mrad of bending magnet radiation to an ultrahigh vacuum endstation chamber to facilitate angle resolved photoelectron spectroscopy. The 5m-TGM beamline is equipped with Au-coated gratings with 300, 600 and 1200 lines/mm providing monochromatized synchrotron radiation in the energy ranges 25-70 eV, 50-120 eV and 100-240 eV, respectively. The beamline delivers excellent flux (~1014-1017 photons/sec/100mA) and a combined energy resolution of 189 meV for the beamline (at 1.0 mm slit opening) and HA-50 hemispherical analyzer was obtained at the Fermi level of polycrystalline gold crystal. Our preliminary photoelectron spectroscopy results of phenol adsorption on TiO2 (110) surface reveals the metal ion (Ti) oxidation.

Niemann-Pick type C Suspicion Index tool: analyses by age and association of manifestations

OBJECTIVE

The Suspicion Index (SI) screening tool was developed to identify patients suspected of having Niemann-Pick disease type C (NP-C). The SI provides a risk prediction score (RPS) based on NP-C manifestations within and across domains (visceral, neurological, and psychiatric). The aim of these subanalyses was to further examine the discriminatory power of the SI by age and manifestation-associations by NP-C suspicion-level and leading manifestations.

METHODS

The original retrospectively collected data were split into three patient age groups, where NP-C-positive cases were >16 years (n = 30), 4-16 years (n = 18), and <4 years (n = 23), and patients' RPS were analyzed by logistic regression. Co-occurrence of manifestations within groups of suspicion level (low, medium, high) and leading manifestations (presence/absence of ataxia, cognitive decline, psychosis, and splenomegaly) were analyzed descriptively.

RESULTS

NP-C-positive cases versus controls showed strong discriminatory power of RPS. Area under the receiver operating characteristic curve was 0.964 (>16 years) and 0.981 (4-16 years) but weaker 0.562 for infants (<4 years). Patients with RPS <70 were characterized by a lack of psychiatric manifestations and low levels of neurological involvement, suggestive of a preneurological phase of the disease. In patients >4 years, prominent leading manifestation-associations were ataxia with dystonia, dysarthria/dysphagia, and cognitive decline. Psychosis was associated with dysarthria/dysphagia but also with cognitive decline and treatment-resistant psychiatric symptoms.

CONCLUSIONS

The SI tool maintains strong discriminatory power in patients >4 years but is not as useful for infants <4 years. The SI is also informative regarding the association and co-occurrence of manifestations in patients with NP-C.

Genetic screening for Niemann-Pick disease type C in adults with neurological and psychiatric symptoms: findings from the ZOOM study

Niemann–Pick disease type C (NP-C) is a rare, autosomal-recessive, progressive neurological disease caused by mutations in either the NPC1 gene (in 95% of cases) or the NPC2 gene. This observational, multicentre genetic screening study evaluated the frequency and phenotypes of NP-C in consecutive adult patients with neurological and psychiatric symptoms. Diagnostic testing for NP-C involved NPC1 and NPC2 exonic gene sequencing and gene dosage analysis. When available, results of filipin staining, plasma cholestane-3β,5α,6β-triol assays and measurements of relevant sphingolipids were also collected. NPC1 and NPC2 gene sequencing was completed in 250/256 patients from 30 psychiatric and neurological reference centres across the EU and USA [median (range) age 38 (18–90) years]. Three patients had a confirmed diagnosis of NP-C; two based on gene sequencing alone (two known causal disease alleles) and one based on gene sequencing and positive filipin staining. A further 12 patients displayed either single mutant NP-C alleles (8 with NPC1 mutations and 3 with NPC2 mutations) or a known causal disease mutation and an unclassified NPC1 allele variant (1 patient). Notably, high plasma cholestane-3β,5α,6β-triol levels were observed for all NP-C cases (n = 3). Overall, the frequency of NP-C patients in this study [1.2% (95% CI; 0.3%, 3.5%)] suggests that there may be an underdiagnosed pool of NP-C patients among adults who share common neurological and psychiatric symptoms.

Posterior reversible encephalopathy syndrome and hemorrhage associated with tacrolimus in a pediatric heart transplantation recipient

Posterior reversible encephalopathy syndrome (PRES) is a disorder characterized by gray and white matter abnormalities in the temporal, parietal, and occipital lobes of the brain. Its etiology has been attributed to renal failure, immunosuppressive drugs such as cyclosporine and tacrolimus, and other potential entities leading to acute hypertension. Clinical findings include headaches, altered mental status, seizures, visual changes, and focal neurologic deficits. We report the case of a child who developed PRES with intracerebral and subarachnoid hemorrhages associated with tacrolimus exposure 10 days after heart transplantation for restrictive cardiomyopathy. The patient initially presented with complex partial seizures, headache, agitation, and hypertension. Head MRI was suggestive of PRES along with intracerebral and subarachnoid hemorrhages. Tacrolimus was discontinued and blood pressure was controlled. The patient's encephalopathy resolved, but he has had ongoing neurologic symptoms secondary to hemorrhage. Generally, PRES is less common in children than in the adult population and is a rare complication of calcineurin inhibitors (CNI). Presentation with secondary hemorrhage also can occur. In children receiving CNIs presenting with new neurologic symptoms, PRES should be considered as prompt discontinuation of the offending agent can induce resolution of symptoms. Children can develop hemorrhage in the context of PRES, leading to increased morbidity.

Views of recently first-certified US child neurologists on their residency training

We surveyed child neurologists first certified in "Neurology with Special Qualification in Child Neurology" by the American Board of Psychiatry and Neurology (ABPN) between 2001 and 2010 using a 24-item questionnaire. Respondents (n = 204, 54% response rate) were between the ages of 30 and 59 years (54% male), and 68% completed adult neurology training in a 10- to 12-month, primarily inpatient block. Sixty-two percent of the sample completed subspecialty fellowship training and 82% currently reported practicing within a hospital or hospital-based/owned clinic. Current practice data showed just 3% provide general neurology services to adults. A majority reported using adult neurology residency training "less than weekly" and believed the ideal model for residency training in diagnosis and management of both common and rare neurologic conditions would involve less time in adult neurology and more time (mean 6 months) in child neurology, most prominently in genetics and developmental and behavioral areas.

Disease and patient characteristics in NP-C patients: findings from an international disease registry

BACKGROUND

Niemann-Pick disease type C (NP-C) is a rare neurovisceral disease characterized by progressive neurodegeneration and premature death. We report data recorded at enrolment in an ongoing international NP-C registry initiated in September 2009 to describe disease natural history, clinical course and treatment experience of NP-C patients in clinical practice settings.

METHODS

The NPC Registry is a prospective observational cohort study. Participating sites are encouraged to evaluate all consecutive patients with a confirmed diagnosis of NP-C, regardless of their treatment status. All patients undergo clinical assessments and medical care as determined by their physicians. Data are collected through a secure internet-based data collection system.

RESULTS

As of 19th March, 2012, 163 patients have been enrolled in centres across 14 European countries, Australia, Brazil and Canada. The mean (SD) age at enrolment was 19.6 (13.0) years. In general there was a long lag time between the mean (SD) age at neurological onset (10.9 (9.8) years) and age at diagnosis (15.0 (12.2) years). Among all enrolled patients, 107 were diagnosed based on combined genetic testing and filipin staining. Sixteen (11%) out of 145 patients with available age-at-neurological-onset data had early-infantile neurological onset, 45 (31%) had late-infantile onset; 45 (31%) had juvenile onset and 39 (27%) had adolescent/adult onset. The frequencies of neonatal jaundice, hepatomegaly and/or splenomegaly during infancy were greatest among early-infantile patients, and decreased with increasing age at neurological onset. The most frequent neurological manifestations were: ataxia (70%), vertical supranuclear gaze palsy (VSGP; 70%), dysarthria (66%), cognitive impairment (62%), dysphagia (52%). There were no notable differences in composite NP-C disability scores between age-at-neurological-onset groups. Miglustat therapy at enrolment was recorded in 117/163 (72%) patients.

CONCLUSIONS

Approximately two-thirds of this NP-C cohort had infantile or juvenile onset of neurological manifestations, while the remaining third presented in adolescence or adulthood. While systemic symptoms were most common among patients with early-childhood onset disease, they were also common among patients with adolescent/adult onset. The profiles of neurological manifestations in this Registry were in line with previous publications.

Gangliosidoses

The gangliosidoses comprise a family of lysosomal storage diseases characterized by the accumulation of complex glycosphingolipids in the nervous system and other tissues, secondary to the deficient activity of lysosomal hydrolases or their associated activator proteins. GM1 and GM2 gangliosidosis are associated with deficiency of β-galactosidase and β-hexosaminidase respectively. All gangliosidoses are characterized by progressive neurodegeneration, the severity of which is proportional to the residual enzyme activity. The GM1 gangliosidoses are characterized by dysostosis, organomegaly and coarsening in their most severe forms, whereas children with classic infantile GM2 gangliosidosis (Tay-Sachs disease) are usually spared systemic involvement, except in the case of the Sandhoff variant, in which organomegaly may occur. Cherry-red macular spots occur in the early onset forms of the gangliosidoses, but are less frequently seen in the less severe, later onset phenotypes. Macrocephaly, an exaggerated startle response, cognitive decline, seizures, ataxia, and progressive muscular atrophy may occur in different forms of gangliosidosis. The diagnosis is made by assay of enzyme activity, and can be confirmed by mutation analysis. Carrier screening for Tay-Sachs disease has been remarkably successful in reducing the incidence of this disease in the at-risk Ashkenazi population. There are no proven disease-modifying therapies for the gangliosidoses.

Dysphagia as a risk factor for mortality in Niemann-Pick disease type C: systematic literature review and evidence from studies with miglustat

Niemann-Pick disease type C (NP-C) is a rare neurovisceral disease characterised by progressive neurological deterioration and premature death, and has an estimated birth incidence of 1:120,000. Mutations in the NPC1 gene (in 95% of cases) and the NPC2 gene (in approximately 4% of cases) give rise to impaired intracellular lipid metabolism in a number of tissues, including the brain. Typical neurological manifestations include vertical supranuclear gaze palsy, saccadic eye movement abnormalities, cerebellar ataxia, dystonia, dysmetria, dysphagia and dysarthria. Oropharyngeal dysphagia can be particularly problematic as it can often lead to food or fluid aspiration and subsequent pneumonia. Epidemiological data suggest that bronchopneumonia subsequent to food or fluid aspiration is a major cause of mortality in NP-C and other neurodegenerative disorders. These findings indicate that a therapy capable of improving or stabilising swallowing function might reduce the risk of aspiration pneumonia, and could have a positive impact on patient survival. Miglustat, currently the only approved disease-specific therapy for NP-C in children and adults, has been shown to stabilise key neurological manifestations in NP-C, including dysphagia. In this article we present findings from a systematic literature review of published data on bronchopneumonia/aspiration pneumonia as a cause of death, and on the occurrence of dysphagia in NP-C and other neurodegenerative diseases. We then examine the potential links between dysphagia, aspiration, pneumonia and mortality with a view to assessing the possible effect of miglustat on patient lifespan.

Recommendations for the diagnosis and management of Niemann-Pick disease type C: an update

Niemann-Pick disease type C (NP-C) is a rare inherited neurovisceral disease caused by mutations in either the NPC1 (in 95% of cases) or the NPC2 gene (in around 5% of cases), which lead to impaired intracellular lipid trafficking and accumulation of cholesterol and glycosphingolipids in the brain and other tissues. Characteristic neurological manifestations of NP-C include saccadic eye movement (SEM) abnormalities or vertical supranuclear gaze palsy (VSGP), cerebellar signs (ataxia, dystonia/dysmetria, dysarthria and dysphagia) and gelastic cataplexy. Epileptic seizures are also common in affected patients. Typically, neurological disease onset occurs during childhood, although an increasing number of cases are being detected and diagnosed during adulthood based on late-onset neurological signs and psychiatric manifestations. Categorization of patients according to age at onset of neurological manifestations (i.e. early-infantile, late-infantile, juvenile and adolescent/adult-onset) can be useful for the evaluation of disease course and treatment responses. The first international guidelines for the clinical management of NP-C in children and adults were published in 2009. Since that time a significant amount of data regarding the epidemiology, detection/diagnosis, and treatment of NP-C has been published. Here, we report points of consensus among experts in the diagnosis and treatment of NP-C based on a follow-up meeting in Paris, France in September 2011. This article serves as an update to the original guidelines providing, among other things, further information on detection/diagnostic methods, potential new methods of monitoring disease progression, and therapy. Treatment goals and the application of disease-specific therapy with miglustat are also re-evaluated.

Neurology of inherited glycosylation disorders

Congenital disorders of glycosylation comprise most of the nearly 70 genetic disorders known to be caused by impaired synthesis of glycoconjugates. The effects are expressed in most organ systems, and most involve the nervous system. Typical manifestations include structural abnormalities (eg, rapidly progressive cerebellar atrophy), myopathies (including congenital muscular dystrophies and limb-girdle dystrophies), strokes and stroke-like episodes, epileptic seizures, developmental delay, and demyelinating neuropathy. Patients can also have neurological symptoms associated with coagulopathies, immune dysfunction with or without infections, and cardiac, renal, or hepatic failure, which are common features of glycosylation disorders. The diagnosis of congenital disorder of glycosylation should be considered for any patient with multisystem disease and in those with more specific phenotypic features. Measurement of concentrations of selected glycoconjugates can be used to screen for many of these disorders, and molecular diagnosis is becoming more widely available in clinical practice. Disease-modifying treatments are available for only a few disorders, but all affected individuals benefit from early diagnosis and aggressive management.

Epilepsy in children--when should we think neurometabolic disease?

Seizures are often the first manifestation of central nervous system dysfunction and are common in many inborn errors of metabolism, especially in neonates, infants, and children. A high index of suspicion is required to diagnose inborn errors of metabolism as the cause of seizures. It is also important to recognize these metabolic disorders early, as specific disease-modifying treatments are available for some with favorable long-term outcomes. This review discusses the classification of metabolic disorders as a cause of seizures based on pathogenesis and age and proposes a tiered approach for cost-effective diagnosis of metabolic disorders.

Massive expansion of SCA2 with autonomic dysfunction, retinitis pigmentosa, and infantile spasms

OBJECTIVE

To provide clinical data on a cohort of 6 patients with massive expansion (>200 CAG repeats) of spinocerebellar ataxia type 2 (SCA2) and investigate possible pathways of pathogenesis using bioinformatics analysis of ATXN2 networks.

METHODS

We present data on 6 patients with massive expansion of SCA2 who presented in infancy with variable combinations of hypotonia, global developmental delay, infantile spasms, and retinitis pigmentosa. ATXN2 is known to interact with a network of synaptic proteins. To investigate pathways of pathogenesis, we performed bioinformatics analysis on ATXN2 combined with known genes associated with infantile spasms, retinitis pigmentosa, and synaptic function.

RESULTS

All patients had a progressive encephalopathy with autonomic dysfunction, 4 had retinitis pigmentosa, and 3 had infantile spasms. The bioinformatics analysis led to several interesting findings. First, an interaction between ATXN2 and SYNJ1 may account for the development of retinitis pigmentosa. Second, dysfunction of postsynaptic vesicle endocytosis may be important in children with this progressive encephalopathy. Infantile spasms may be associated with interactions between ATXN2 and the postsynaptic structural proteins MAGI2 and SPTAN1.

CONCLUSIONS

Severe phenotype in children with massive expansion of SCA2 may be due to a functional deficit in protein networks in the postsynapse, specifically involving vesicle endocytosis.

An unusual presentation of copper metabolism disorder and a possible connection with Niemann-Pick type C

Abnormal copper metabolism has been linked with neurological disorders, such as Wilson and Menkes disease. Another disorder causing symptoms similar to copper metabolism disorder is Niemann-Pick type C. However, a definite pathophysiological connection between Niemann-Pick type C and copper metabolism disorders has never been established. The authors present an adolescent with an unusual presentation of copper deficiency-dysarthria, ataxia, and vertical gaze paresis, without significant cognitive degeneration or pathological magnetic resonance imaging (MRI). The patient was found to carry 2 mutations in the NPC1 gene. A possible link, explaining how copper deficiency might induce the Niemann-Pick phenotype might involve overproduction of cholesterol and inhibition of acid sphingomyelinase. We suggest that copper metabolism disorders be included in the differential diagnosis for ataxia and dysarthria, even in cases with unusual presentations. Moreover, should the connection between copper and Niemann-Pick be validated, screening for copper metabolism disorders may be advisable in Niemann-Pick type C patients and vice-versa.

Miglustat in adult and juvenile patients with Niemann-Pick disease type C: long-term data from a clinical trial

A randomized, controlled trial of miglustat indicated that miglustat (Zavesca) stabilized neurological disease over 12 months in adult and juvenile patients with Niemann-Pick disease type C (NP-C). We report data from a non-controlled, open-label extension to this initial randomized trial. All patients completing the randomized trial were allowed to continue treatment in a 12-month, non-controlled open-label extension. Those completing 12 months of extension therapy could continue further on miglustat in a 'continued extension' phase. From a total of 29 patients in the randomized phase (mean [+/-SD] age 24.6+/-9.1 ears; 52% female), 21 completed 12 months of therapy with miglustat (17 of whom received miglustat in the initial randomized phase, and four in the extension phase), and 15 patients (all from the miglustat-randomized group) completed 24 months on miglustat. Mean horizontal saccadic eye movement velocity (HSEM-alpha) indicated improvement in the 12-month miglustat group, and stabilization in the 24-month group; swallowing was improved or stable in 86% and in up to 93%, respectively. Ambulation was stabilized in both the 12- and 24-month groups. In an exploratory disease stability analysis of prospective data on key parameters of disease progression (HSEM-alpha, swallowing, ambulation and cognition), 13/19 (68%) patients receiving >or= 12 months' miglustat therapy had stable disease. Among all patients receiving >or= 1 dose of miglustat (n=28), the most frequent adverse events were diarrhoea, weight decrease, flatulence and tremor. Overall, these data suggest that long-term miglustat therapy stabilizes neurological disease and is well tolerated in adult and juvenile patients with NP-C.

Long-term miglustat therapy in children with Niemann-Pick disease type C

Niemann-Pick disease type C is a rare, genetic disease associated with impaired intracellular lipid trafficking and progressive neurological symptoms. Miglustat slowed disease progression in a 12-month randomized trial in juveniles and adults with Niemann-Pick disease type C, and in a parallel, noncontrolled study in affected children. Here, the authors report the open-label extension to the pediatric study. Patients aged 4 to 12 years received open-label miglustat (dose adjusted for body surface area) for an initial 12 months, during a further 12-month extension, and a long-term, continued extension phase. Efficacy assessments included horizontal saccadic eye movement, swallowing, and ambulation. Ten children completed 24 months' treatment. Horizontal saccadic eye movement, ambulation, and swallowing were stabilized at 24 months. Analysis of key parameters of disease progression showed disease stability in 8 of 10 patients (80%). Miglustat stabilized neurological disease progression in pediatric patients with Niemann-Pick disease type C, with comparable safety and tolerability to that observed in adults and juveniles.

Cerebral and cerebellar white matter abnormalities with magnetic resonance imaging in a child with Feingold syndrome

Feingold syndrome is a rare autosomal dominant condition that is characterized by variable expressivity of microcephaly, limb malformations, esophageal atresia, and a host of other malformations. This syndrome results from mutations in the MYCN proto-oncogene. Few examples of cross-sectional imaging of the brain in these patients are found in the literature. We present a patient who was found to have areas of cerebral and cerebellar white matter hyperintensity with T2 weighted magnetic resonance (MR) imaging. To the best of our knowledge, this finding has not been previously described. While the significance and pathologic basis of this finding are unknown, its recognition is important since it has potential to be confused with imaging findings in other conditions. Moreover, it is likely to be observed in the future due to increased use of MR imaging.

Spiral analysis in Niemann-Pick disease type C

Spiral analysis is a computerized method of analyzing upper limb motor physiology through the quantification of spiral drawing. The objective of this study was to determine whether spirals drawn by patients with Niemann-Pick disease type C (NPC) could be distinguished from those of controls, and to physiologically characterize movement abnormalities in NPC. Spiral data consisting of position, pressure, and time were collected from 14 NPC patients and 14 age-matched controls, and were analyzed by the Mann-Whitney U test. NPC spirals were characterized by: lower speed (2.67 vs. 9.56 cm/s, P < 0.001) and acceleration (0.10 vs. 2.04 cm/s(2), P < 0.001), higher loop width variability (0.88 vs. 0.28, P < 0.001), tremor (5/10 vs. 0/10 trials in the dominant hand, P < 0.001), and poor overall spiral rating (2.53 vs. 0.70, P < 0.005). NPC spirals also exhibited sustained drawing pressure profiles that were abnormally invariant with time. Other features, such as the tightness of loop widths, were normal. Our findings reveal that differing aspects of tremor, Parkinsonism, ataxia, and dystonia are quantifiable in NPC patients.

Linear clinical progression, independent of age of onset, in Niemann-Pick disease, type C

Niemann-Pick disease, type C is a neurodegenerative, lysosomal storage disorder with a broad clinical spectrum and a variable age of onset. The absence of a universally accepted clinical outcome measure is an impediment to the design of a therapeutic trial for NPC. Thus, we developed a clinical severity scale to characterize and quantify disease progression. Clinical signs and symptoms in nine major (ambulation, cognition, eye movement, fine motor, hearing, memory, seizures, speech, and swallowing) and eight minor (auditory brainstem response, behavior, gelastic cataplexy, hyperreflexia, incontinence, narcolepsy, psychiatric, and respiratory problems) domains were scored. Data were collected from 18 current NPC patients and were extracted from records of 19 patients. Both patient cohorts showed a linear increase in severity scores over time. Cross-sectional evaluation of current patients showed a linear increase in the severity score. Longitudinal chart review of historical data demonstrated that although age of onset varied significantly, the rate of progression appeared linear, independent of age of onset, and similar in all patients. Combining the data from both cohorts, disease progression could be modeled by the following equation: ŝ(t0+x) = ŝ(t0) + 1.87x; where ŝ(t0) is the initial score and ŝ(t0+x) is the predicted future score after x years. Our observation that disease progression is similar across patients and independent of age of onset is consistent with a biphasic pathological model for NPC. This scale may prove useful in the characterization of potential biomarkers, and as an outcome measure to monitor disease progression in NPC patients.

Myelination disturbance in a patient with hyperuricemia and hyperserotoninemia combined with 18q deletion syndrome

We previously reported a male patient with an 18q21.3 deletion, hyperuricemia and typical symptoms of the Lesch-Nyhan syndrome who lacked hypoxanthine-guanine-phosphoribosyl-transferase (HGPRT) deficiency. The patient developed progressive peripheral neuropathy in additon to his profound mental retardation and self-injurious behavior. At the age of 23 years MR imaging revealed globally delayed myelination with relative sparing of the corpus callosum and frontal lobes. They were focal hyperintensities suggestive of gliosis. Multimodality evoked potentials found evidence of impaired central and peripheral conduction. Single photon emission computed tomographic (SPECT) imaging demonstrated left frontal hyperperfusion and under it a temporoparietal hypoperfusion.

Miglustat in patients with Niemann-Pick disease Type C (NP-C): a multicenter observational retrospective cohort study

Miglustat has been shown to stabilize disease progression in children, juveniles and adults with Niemann-Pick disease type C (NP-C), a rare genetic disorder characterized by progressive neurological deterioration. We report findings from a retrospective observational cohort study assessing the effects of miglustat on neurological disease progression in patients treated in the clinical practice setting. Data from all NP-C patients prescribed miglustat at 25 expert centers were evaluated using a disease disability scale. The scale analyzed four key parameters of neurological disease progression in NP-C (ambulation, manipulation, language, swallowing). Mean individual parameter scores and a composite score were calculated at baseline (time of diagnosis) and up to 4 follow-up visits. Overall, 66 patients were included (mean [SD] age at diagnosis, 9.7 [7.6] years, and at treatment start, 12.8 [9.5] years). The median (range) miglustat exposure was 1.46 (0.05-4.51) years. Mean annual progression was +0.11 score units/year from diagnosis to treatment start, indicating disease progression prior to therapy, and decreasing to -0.01 score units/year from treatment start to last clinic visit, indicating stabilization. Stabilization of neurological disease on miglustat was observed in all age groups, but the magnitude of the effect was greater in patients diagnosed in late childhood and in juveniles and adults. Stabilization of neurological disease was also observed in a subset of 19 patients with extended pre-treatment information. Overall, these data support previous clinical trial findings indicating clinically relevant beneficial effects of miglustat on neurological disease progression in patients with NP-C.

Subclinical seizures in children diagnosed with localization-related epilepsy: clinical and EEG characteristics

OBJECTIVE

Subclinical seizures (SCSs) are characterized by paroxysmal rhythmic epileptiform discharges that evolve in time and space in the absence of objective clinical manifestation or report of a seizure. The aim of this study was to evaluate the frequency and characteristics of SCSs in children with localization-related epilepsy (LRE).

METHODS

The results of video/EEG monitoring were reviewed to identify patients with SCS. We identified 187 children diagnosed with LRE, in 32 of whom SCSs were reported in the EEG recording.

RESULTS

SCSs were reported only in the children who had received a diagnosis of either symptomatic or cryptogenic LRE. All children had a history of clinical seizure(s). The ictal onset of SCSs was most frequent from the temporal and frontal lobes. SCSs were lateralized to the left hemispheres in 19, right hemisphere in 8, and both hemispheres independently in 5 children. SCSs were more often reported in young children, and associated with a history of developmental delay, infantile spasms, and frequent seizures. EEG abnormalities included background slowing and lack of normal sleep architecture in addition to the epileptiform activity. Seizure freedom was reported less often in children with SCSs. Six patients seizure free at the time of the admission were found to have SCSs.

CONCLUSION

Subclinical seizures are not uncommon in children with LRE, in particular, with younger age, developmental disability, and medically refractory clinical course. Video/EEG monitoring will be informative in selected children with LRE to assess the seizure frequency more accurately.

Recommendations on the diagnosis and management of Niemann-Pick disease type C

Niemann-Pick disease type C (NP-C) is a lysosomal storage disease in which impaired intracellular lipid trafficking leads to excess storage of cholesterol and glycosphingolipids in the brain and other tissues. It is characterized clinically by a variety of progressive, disabling neurological symptoms including clumsiness, limb and gait ataxia, dysarthria, dysphagia and cognitive deterioration (dementia). Until recently, there has been no disease-modifying therapy available for NP-C, with treatment limited to supportive measures. In most countries, NP-C is managed through specialist centers, with non-specialist support provided locally. However, effective patient support is hampered by the absence of national or international clinical management guidelines. In this paper, we seek to address this important gap in the current literature. An expert panel was convened in Paris, France in January 2009 to discuss best care practices for NP-C. This commentary reviews current literature on key aspects of the clinical management of NP-C in children, juveniles and adults, and provides recommendations based on consensus between the experts at the meeting.

Limbic encephalitis associated with anti-GAD antibody and common variable immune deficiency

A variety of autoantibodies have been identified with complex neurological disorders including limbic encephalitis. The underlying trigger for the immune-mediated process and the role of autoantibodies in the pathogenesis of limbic encephalitis remain to be clarified. Here, we report a 16-year-old female who was diagnosed with acute-onset non-neoplastic limbic encephalitis. The initial treatment with pulse doses of i.v. methylprednisolone improved the neurological symptoms. During the next 12 months, progressive decline was reported in her academic functioning and seizure control. Additional diagnostic evaluation revealed no evidence of malignancy or central nervous system infection but circulating anti-GAD antibodies were present in the serum and cerebrospinal fluid. Intravenous gammaglobulin infusion was initiated and continued monthly. Intravenous and oral steroids were added to the intravenous immunoglobulin treatment because of the worsening course and seizures, despite treatment with antiepileptic medications. Screening for quantitative immunoglobulins demonstrated hypogammaglobulinaemia with low immunoglobulin M and G in addition to low immunoglobulin A levels. There was a lack of protective pneumococcal antibody titers before and after immunization. Therefore, common variable immunodeficiency was suspected despite there being no history of recurrent infections. To our knowledge, this is the first report describing a possible link between immune-mediated limbic encephalitis and immune deficiency.

IGF system in children with congenital disorders of glycosylation

OBJECTIVE

The function of IGF system components is affected by their glycosylation status in vitro. However, little is known about the role of glycosylation status of these components in vivo. In this study we determined the impact of glycosylation on the endocrine IGF system in children with the rare syndrome of congenital disorders of glycosylation (CDG).

DESIGN

Analyses of serum samples from children with CDG and healthy controls.

PATIENTS

Children with CDG (N = 12) were recruited as part of a separate clinical study of mannose therapy at the Mayo Clinic. Serum from control children (N = 11) were obtained as routine samples before discard.

MEASUREMENTS

Levels and glycosylation state of components of the IGF system and ability to form physiologically relevant ternary complexes composed of IGF, IGFBP-3, and an acid-labile subunit (ALS).

RESULTS

Serum levels of IGF-1, IGF-2, ALS, and IGFBP-3 were reduced (P < 0.05) in children with CDG when compared to controls. Immunoblot analysis showed incomplete glycosylation of ALS and IGFBP-3 and impaired ternary complex formation in CDG. Partial normalization of ALS and IGFBP-3 glycosylation was associated with improvement in linear growth in a child with CDG-Ib during initiation of oral mannose therapy.

CONCLUSIONS

Inadequate glycosylation of IGFBP-3 and ALS has a negative effect on the function of these proteins in vivo. This study provides the first evidence in humans for the importance of glycosylation on components of the IGF system.

Newborn screening for Krabbe disease: the New York State model

Krabbe disease is a rare inherited neurologic disorder affecting the central and peripheral nervous systems. The disease has four phenotypes: early infantile, later onset, adolescent, and adult. The only known treatment is hematopoietic stem cell transplantation, which is, in the early infantile form of the disease, most beneficial if performed before onset of clinical symptoms. In August 2006, New York State began screening all newborns for Krabbe disease. A rapid and accurate technique for assessing galactocerebrosidase activity and performing DNA mutation analysis had been developed. Interpreting these results was limited, however, because neither enzyme activity nor genetic mutation reliably predicts phenotype. A series of initiatives were therefore developed by a multidisciplinary group of neurologists, geneticists, metabolic pediatricians, neurodevelopmental pediatricians, and transplant physicians (the Krabbe Consortium of New York State) to enhance the effectiveness of the newborn screening program. A standardized clinical evaluation protocol was designed based on the available literature, criteria for transplantation for the early infantile phenotype were formulated, a clinical database and registry was developed, and a study of developmental and functional outcomes was instituted. This multidisciplinary standardized approach to evaluating infants who have positive results on newborn screening may serve as a model for other states as they begin the process of screening for Krabbe disease and other lysosomal storage disorders.

Long-term outcome of symptomatic infantile spasms established by video-electroencephalography (EEG) monitoring

In this study, we examine the long-term clinical outcome of children with symptomatic infantile spasm. The children between 2 and 18 years of age diagnosed with symptomatic infantile spasms were reviewed. Sixty-eight children (age range, 2-13 years; mean, 4.5 years) met the inclusion criteria. Children who underwent epilepsy surgery were excluded. Age of onset for infantile spasms ranged from 1 to 24 months (mean, 7.1 months). Developmental delay was noted in all; there was seizure freedom in 14 children (20.5%). Infantile spasms were reported as the only seizure type in 10 (14.5%) children older than age 2 years. During the follow-up; symptomatic generalized epilepsy was diagnosed in 23 children (34%) and focal epilepsy in 21 (31%). The long-term outcome of these children remains unchanged in the majority of the children with symptomatic infantile spasms. We could not establish any risk factor that might be related to favorable or adverse outcome.

The frequency of non-epileptic spells in children: results of video-EEG monitoring in a tertiary care center

RATIONALE

the diagnosis of non-epileptic spells (NES) in children can be challenging, even for experienced clinicians. Our objective was to describe the characteristics of such events.

METHODS

this was a retrospective study conducted from January 2004 to December 2006. Inclusion criteria were age >1 month and <18 years and the diagnosis of NES established by video-EEG monitoring.

RESULTS

among 746 monitored children (1203 recorded video-EEG sessions), 109 (14.6%) had NES. The mean age of patients with NES was 6.6 years (range 0.1-18). Seventy patients were diagnosed with NES alone; the remaining 39 with both NES and epilepsy. Developmental delay was more frequent among patients with a co-morbid diagnosis of epilepsy (p<0.001). Similar clinical events were reported in both of these groups, save for crying spells/irritability which was more common in children with epilepsy. Frequent manifestations of NES included staring spells in preschool children, crying/irritability, tremor and eye deviation in young children and preschoolers, and limb shaking in adolescents. All of the patients with epilepsy and 19 (27%) of those without epilepsy were receiving antiepileptic drugs.

CONCLUSION

our data highlights the importance of accurate diagnosis of NES toward the appropriate treatment of affected children.

Miglustat for treatment of Niemann-Pick C disease: a randomised controlled study

BACKGROUND

Niemann-Pick type C disease (NPC) is an inherited neurodegenerative disorder characterised by an intracellular lipid-trafficking defect with secondary accumulation of glycosphingolipids. Miglustat, a small iminosugar, reversibly inhibits glucosylceramide synthase, which catalyses the first committed step of glycosphingolipid synthesis. Miglustat is able to cross the blood-brain barrier, and is thus a potential therapy for neurological diseases. We aimed to establish the effect of miglustat on several markers of NPC severity.

METHODS

Patients aged 12 years or older who had NPC (n=29) were randomly assigned to receive either miglustat 200 mg three times a day (n=20) or standard care (n=9) for 12 months. 12 children younger than 12 years of age were included in an additional cohort; all received miglustat at a dose adjusted for body surface area. All participants were then treated with miglustat for an additional year in an extension study. The primary endpoint was horizontal saccadic eye movement (HSEM) velocity, based on its correlation with disease progression. This study is registered as an International Standard Randomised Controlled Trial, number ISRCTN26761144.

FINDINGS

At 12 months, HSEM velocity had improved in patients treated with miglustat versus those receiving standard care; results were significant when patients taking benzodiazepines were excluded (p=0.028). Children showed an improvement in HSEM velocity of similar size at 12 months. Improvement in swallowing capacity, stable auditory acuity, and a slower deterioration in ambulatory index were also seen in treated patients older than 12 years. The safety and tolerability of miglustat 200 mg three times a day in study participants was consistent with previous trials in type I Gaucher disease, where half this dose was used.

INTERPRETATION

Miglustat improves or stabilises several clinically relevant markers of NPC. This is the first agent studied in NPC for which there is both animal and clinical data supporting a disease modifying benefit.

Scurvy and rickets masked by chronic neurologic illness: revisiting "psychologic malnutrition"

The North American epidemic of overeating, combined with a sedentary lifestyle, has led to a growing prevalence of obesity, diabetes, and the "metabolic syndrome" in children. Excessive caloric intake does not imply adequate nutrition, and vitamin-deficiency syndromes still occur in some American children. Here we describe cases of scurvy and vitamin D deficiency in 2 children with cognitive disorders. Thorough dietary histories suggested the diagnosis in each patient and, had they been obtained at presentation, would likely have obviated invasive diagnostic workup, unnecessary stress to the patients and their families, and significant functional disability. Overnutrition and malnutrition may coexist, particularly among those with abnormal cognition or autistic spectrum disorders. Classic nutritional deficiencies must not be omitted from the differential diagnosis. A comprehensive dietary history and screening for vitamin deficiencies in at-risk children are important aspects of preventive health care and are essential for prompt diagnosis and treatment.

Kinematic analysis of motor dysfunction in Niemann-Pick type C

OBJECTIVE

To provide the first descriptive analysis of upper limb motor physiology in Niemann-Pick Type C disease (NP-C).

METHODS

Fifteen patients with confirmed NP-C underwent motor physiology testing using accelerometry and surface EMG (sEMG). Tremor amplitude and frequency were quantified using accelerometry, and sEMG was examined for abnormal patterns consistent with various movement disorders.

RESULTS

Forty-seven percent of patients had postural tremor in the upper limbs, generally bilateral, with frequencies ranging from 0.3 to 3 Hz, and an average amplitude of 1.20+/-0.98 mm. Eighty-seven percent of patients had bilateral action tremor with frequencies ranging from 2.0 to 3.7 Hz, and an average amplitude of 5.25+/-3.76 mm. sEMG revealed long but variable duration, variable amplitude muscle burst discharges during action in some patients, as well as short high frequency irregularly timed bursts in others.

CONCLUSIONS

Accelerometric findings correlated with the clinical findings were most consistent with cerebellar outflow tremors. sEMG revealed a mix of dystonic, myoclonic and choreiform movements.

SIGNIFICANCE

These quantitative methods may serve as ancillary measures of disease pathophysiology, markers of change over time, and methods to evaluate efficacy, and side effects, of new treatments as they are developed.

Metabolic mimics: the disorders of N-linked glycosylation

N-linked glycosylation is essential for normal cellular function. Defects have now been described in eighteen genes that participate in the process. All give rise to complex multisystem diseases which, with a few exceptions, primarily involve the nervous system. Frequent features of these disorders include developmental delay, ataxia, seizures, stroke-like episodes, recurrent infections, coagulopathy and dysmorphism. Most cases can be detected by screening carbohydrate-deficient transferrin, but definitive diagnosis requires enzymatic and molecular confirmation, frequently in collaboration with a research glycobiologist.

Therapy of Niemann–Pick disease, type C

Niemann-Pick disease, type C (NPC) is a progressive autosomal recessive neurodegenerative disease, characterized by late endosomal-lysosomal accumulation of multiple lipid molecules in association with abnormal tubulovesicular trafficking. The major gene product, NPC1 protein, is not suitable for transduction therapies, and gene replacement or repair is not yet practicable for NPC and related disorders. Attempts at therapy to date have focused on reduction of the accumulating molecules that are presumed to have direct or indirect toxic effects. More recent insights into the pathophysiology of NPC raise the possibility of small molecule therapies to interdict pathways triggering apoptosis and related routes to cell death and dysfunction.

The pathophysiology and mechanisms of NP-C disease

The molecular isolation of NPC1 and NPC2, the genes defective in patients with Niemann-Pick disease type C (NP-C), has heralded in an exponential increase in our understanding of this syndrome and thus of human intracellular sterol transport. Despite this, neither the mechanisms of action nor the substrates for these putative transporters have been defined. In this overview, we describe our perspectives on the current awareness of the genetic determination and cellular biology of this syndrome, with emphasis on the underlying events that lead to neurodegeneration and the manner in which they might eventually be treated.