Vertical supranuclear gaze palsy in Niemann-Pick type C disease

Supranuclear Palsy as an Initial Presentation of the Adult-Onset Niemann-Pick Type C

(1) Background: Niemann-Pick type C1 (NP-C1) is a lysosomal storage disorder that results in the defective trafficking of cholesterol and other cellular lipids in the endosomal-lysosomal pathway. This rare autosomal recessive disorder presents in three forms based on the age of onset. The adult form presents in patients greater than 15 years of age but is rarely seen after the age of 30. Common symptoms of the late adult-onset category of NP-C1 include progressive cognitive impairment and ataxia, with psychiatric and movement disorders presenting less frequently than in other forms of NP-C1. Dystonic movement disorders present most frequently, along with chorea, myoclonus, and parkinsonism. Herein, we present a rare case of NP-C1, diagnosed at age 35 with an initial symptom of supranuclear palsy. The goal of the presented case is to highlight the importance of the neurological examination and an inclusive differential diagnosis in patients with new-onset supranuclear palsy. (2) Methods: A single case report. (3) Results: A 46-year-old male with a past medical history of NP-C1 was admitted to the hospital for respiratory distress. He was noted to have a supranuclear gaze palsy with partially preserved voluntary saccades to the right. His mother revealed that he first had difficulty moving his eyes at the age of 34. After multiple consultations and genetic testing one year later, he was diagnosed with NP-C1. (4) Conclusions: Because NP-C1 affects many regions of the brain responsible for eye movements, neurological eye assessments can be a useful tool in diagnoses. Furthermore, eye movement abnormalities may be the initial presenting symptom of NP-C1, predisposing patients to misdiagnosis with progressive supranuclear palsy and other conditions that may mimic early-stage NP-C1. Definitive diagnosis is achieved through genetic testing. Filipin staining test was the gold standard in the past. The NP-C Suspicion Index was developed to assist in diagnoses, but its efficacy is unclear with late adult-onset NP-C1. Although no cure exists, early identification can facilitate an improved symptom management course for patients. Miglustat, a glucosylceramide synthase (GCS) inhibitor, is the approved therapy in Europe specific to NP-C1 for slowing and preventing the neurological manifestations of NP-C1. Delays between symptom onset and treatment initiation are likely to result in poorer outcomes and a progression of neurological symptoms. High doses may present tolerance concerns, especially in cases of delayed treatment and advanced neurological deficit.

Hepatomegaly and Splenomegaly: An Approach to the Diagnosis of Lysosomal Storage Diseases

Clinical findings of hepatomegaly and splenomegaly, the abnormal enlargement of the liver and spleen, respectively, should prompt a broad differential diagnosis that includes metabolic, congestive, neoplastic, infectious, toxic, and inflammatory conditions. Among the metabolic diseases, lysosomal storage diseases (LSDs) are a group of rare and ultrarare conditions with a collective incidence of 1 in 5000 live births. LSDs are caused by genetic variants affecting the lysosomal enzymes, transporters, or integral membrane proteins. As a result, abnormal metabolites accumulate in the organelle, leading to dysfunction. Therapeutic advances, including early diagnosis and disease-targeted management, have improved the life expectancy and quality of life of people affected by certain LSDs. To access these new interventions, LSDs must be considered in patients presenting with hepatomegaly and splenomegaly throughout the lifespan. This review article navigates the diagnostic approach for individuals with hepatosplenomegaly particularly focusing on LSDs. We provide hints in the history, physical exam, laboratories, and imaging that may identify LSDs. Additionally, we discuss molecular testing, arguably the preferred confirmatory test (over biopsy), accompanied by enzymatic testing when feasible.

Investigation of Brain Iron in Niemann-Pick Type C: A 7T Quantitative Susceptibility Mapping Study

BACKGROUND AND PURPOSE

While brain iron dysregulation has been observed in several neurodegenerative disorders, its association with the progressive neurodegeneration in Niemann-Pick type C is unknown. Systemic iron abnormalities have been reported in patients with Niemann-Pick type C and in animal models of Niemann-Pick type C. In this study, we examined brain iron using quantitative susceptibility mapping MR imaging in individuals with Niemann-Pick type C compared with healthy controls.

MATERIALS AND METHODS

A cohort of 10 patients with adolescent- and adult-onset Niemann-Pick type C and 14 age- and sex-matched healthy controls underwent 7T brain MR imaging with T1 and quantitative susceptibility mapping acquisitions. A probing whole-brain voxelwise comparison of quantitative susceptibility mapping between groups was conducted. Mean quantitative susceptibility mapping in the ROIs (thalamus, hippocampus, putamen, caudate nucleus, and globus pallidus) was further compared. The correlations between regional volume, quantitative susceptibility mapping values, and clinical features, which included disease severity on the Iturriaga scale, cognitive function, and the Social and Occupational Functioning Assessment Scale, were explored as secondary analyses.

RESULTS

We observed lower volume in the thalamus and voxel clusters of higher quantitative susceptibility mapping in the pulvinar nuclei bilaterally in patients with Niemann-Pick type C compared with the control group. In patients with Niemann-Pick type C, higher quantitative susceptibility mapping in the pulvinar nucleus clusters correlated with lower volume of the thalamus on both sides. Moreover, higher quantitative susceptibility mapping in the right pulvinar cluster was associated with greater disease severity.

CONCLUSIONS

Our findings suggest iron deposition in the pulvinar nucleus in Niemann-Pick type C disease, which is associated with thalamic atrophy and disease severity. This preliminary evidence supports the link between iron and neurodegeneration in Niemann-Pick type C, in line with existing literature on other neurodegenerative disorders.

Accuracy of clinical versus oculographic detection of pathological saccadic slowing

Saccadic slowing as a component of supranuclear saccadic gaze palsy is an important diagnostic sign in multiple neurologic conditions, including degenerative, inflammatory, genetic, or ischemic lesions affecting brainstem structures responsible for saccadic generation. Little attention has been given to the accuracy with which clinicians correctly identify saccadic slowing. We compared clinician (n = 19) judgements of horizontal and vertical saccade speed on video recordings of saccades (from 9 patients with slow saccades, 3 healthy controls) to objective saccade peak velocity measurements from infrared oculographic recordings. Clinician groups included neurology residents, general neurologists, and fellowship-trained neuro-ophthalmologists. Saccades with normal peak velocities on infrared recordings were correctly identified as normal in 57% (91/171; 171 = 9 videos × 19 clinicians) of clinician decisions; saccades determined to be slow on infrared recordings were correctly identified as slow in 84% (224/266; 266 = 14 videos × 19 clinicians) of clinician decisions. Vertical saccades were correctly identified as slow more often than horizontal saccades (94% versus 74% of decisions). No significant differences were identified between clinician training levels. Reliable differentiation between normal and slow saccades is clinically challenging; clinical performance is most accurate for detection of vertical saccade slowing. Quantitative analysis of saccade peak velocities enhances accurate detection and is likely to be especially useful for detection of mild saccadic slowing.

Measuring saccades in patients with Niemann-Pick type C: A comparison between video-oculography and a novel eye tracking test based on continuous psychophysics

Introduction

Vertical supranuclear gaze palsy is a key feature of Niemann-Pick type C (NP-C) and is commonly quantified using video-oculography (VOG). VOG requires sitting still for long times and performing specific tasks, thus it can be challenging or impossible for patients severely affected by movement disorders or cognitive impairment. To overcome this limitation, we measure saccades of NP-C patients using a fast eye tracking test based on continuous psychophysics and compare it to VOG.

Methods

Saccades of six NP-C patients and six age-matched controls were assessed using VOG and Standardized Oculomotor and Neuro-ophthalmic Disorders Assessment (SONDA). In SONDA, participants continuously track a semi-randomly moving dot on a computer screen while their gaze is being tracked. For both assessments, saccades were quantified using four conventional measures: amplitude, gain, latency, and peak velocity. Furthermore, SONDA's continuous measures were quantified with several novel spatio-temporal properties.

Results

In the NP-C patients, both methods revealed reduced amplitude, gain, peak velocity, and increased latency of vertical saccades compared to horizontal saccades and compared to healthy controls. Effect sizes obtained with SONDA were overall larger than those for VOG. SONDA's spatio-temporal properties showed similar trends.

Conclusion

SONDA reveals a deterioration of vertical saccades in NP-C patients that is consistent with VOG. SONDA's measures based on continuous psychophysics are consistent with traditional saccadic parameters and can potentially provide complementary information. SONDA shows larger effect sizes than VOG, suggesting that it provides robust and clinically relevant outcomes with a more intuitive task and shorter testing time.

Eye Movement Disorders in Movement Disorders

Oculomotor assessment is an essential element of the neurological clinical examination and is particularly important when evaluating patients with movements disorders. Most of the brain is involved in oculomotor control, and thus many neurological conditions present with oculomotor abnormalities. Each of the different classes of eye movements and their features can provide important information that can facilitate differential diagnosis. This educational review presents a clinical approach to eye movement abnormalities that are commonly seen in parkinsonism, ataxia, dystonia, myoclonus, tremor, and chorea. In parkinsonism, subtle signs such as prominent square wave jerks, impaired vertical optokinetic nystagmus, and/or the "round the houses" sign suggest early progressive supranuclear gaze palsy before vertical gaze is restricted. In ataxia, nystagmus is common, but other findings such as oculomotor apraxia, supranuclear gaze palsy, impaired fixation, or saccadic pursuit can contribute to diagnoses such as ataxia with oculomotor apraxia, Niemann-Pick type C, or ataxia telangiectasia. Opsoclonus myoclonus and oculopalatal myoclonus present with characteristic phenomenology and are usually easy to identify. The oculomotor exam is usually unremarkable in isolated dystonia, but oculogyric crisis is a medical emergency and should be recognized and treated in a timely manner. Gaze impersistence in a patient with chorea suggests Huntington's disease, but in a patient with dystonia or tremor, Wilson's disease is more likely. Finally, functional eye movements can reinforce the clinical impression of a functional movement disorder.

Applicability of quantitative oculomotor and SARA assessment in children

BACKGROUND

In clinical practice, eye movements can provide an early diagnostic marker for early onset ataxia (EOA). However, quantitative oculomotor assessment is not included in the most frequently used and age-validated ataxia rating scale in children, the Scale for the Assessment and Rating of Ataxia (SARA). We aimed to investigate the applicability of semi-quantitative eye movement assessment by the International Cooperative Ataxia Rating Scale (ICARS_OCM) and Ocular Motion Score (OMS_7-10) complementary to SARA measurements in children.

METHODS

In 52 typically developing children (aged 4-16 years; n = 4 per year of age), three independent assessors scored saccadic eye movements and ocular pursuit according to the ICARS_OCM and matching parameters from the OMS_7-10. For ICARS_OCM, we determined 1) construct validity for coordinated eye movements by correlation with OMS_7-10, ICARS_{EYE-HAND-COORDINATION} and SARA subscale scores, 2) agreement percentage and inter-rater agreement (Fleiss Kappa) and 3) age-dependency.

RESULTS

Spearman's rank correlations of ICARS_OCM with OMS_7-10 and ICARS- and SARA subscales were moderate to fair (all p < .001). Inter-rater agreement of ICARS-_OCM was 80.8%; (Fleiss Kappa: 0.411). ICARS_OCM scores revealed a similar exponentially decreasing association with age as the other SARA (sub)scores, reaching a plateau at 10 years of age.

INTERPRETATION

ICARS_OCM has a valid construct for the measurement of coordinated eye movement performance and is reliably assessable in children. ICARS_OCM reveals a similar age-dependent relationship as the other ataxia subscales, reflecting the physiological maturation of the cerebellum. In children, these data may implicate that ICARS_OCM can reliably contribute to coordination assessment, complementary to the SARA subscales.

A cross-sectional, prospective ocular motor study in 72 patients with Niemann-Pick disease type C

Objective

To characterize ocular motor function in patients with Niemann‐Pick disease type C (NPC).

Methods

In a multicontinental, cross‐sectional study we characterized ocular‐motor function in 72 patients from 12 countries by video‐oculography. Interlinking with disease severity, we also searched for ocular motor biomarkers. Our study protocol comprised reflexive and self‐paced saccades, smooth pursuit, and gaze‐holding in horizontal and vertical planes. Data were compared with those of 158 healthy controls (HC).

Results

Some 98.2% of patients generated vertical saccades below the 95% CI of the controls’ peak velocity. Only 46.9% of patients had smooth pursuit gain lower than that of 95% CI of HC. The involvement in both downward and upward directions was similar (51°/s (68.9, [32.7–69.3]) downward versus 78.8°/s (65.9, [60.8–96.8]) upward). Horizontal saccadic peak velocity and latency, vertical saccadic duration and amplitude, and horizontal position smooth pursuit correlated best to disease severity. Compensating strategies such as blinks to elicit saccades, and head and upper body movements to overcome the gaze palsy, were observed. Vertical reflexive saccades were more impaired and slower than self‐paced ones. Gaze‐holding was normal. Ocular‐motor performance depended on the age of onset and disease duration.

Conclusions

This is the largest cohort of NPC patients investigated for ocular‐motor function. Vertical supranuclear saccade palsy is the hallmark of NPC. Vertical upward and downward saccades are equally impaired. Horizontal saccadic peak velocity and latency, vertical saccadic duration and amplitude, and horizontal position smooth pursuit can be used as surrogate parameters for clinical trials. Compensating strategies can contribute to establishing a diagnosis.

Vertical saccadic palsy and foveal retinal thinning in Niemann-Pick disease type C

INTRODUCTION

Niemann-Pick type C (NPC) is a lysosomal storage disease that is progressive and life-limiting, with an estimated incidence of 1:120,000 live births. In addition to systemic manifestation with (hepato-)splenomegaly, there are a number of neurological manifestations (ataxia, dysarthria, dementia, cataplexy, epileptic seizures, and psychiatric disorders). Characteristic is vertical supranuclear gaze palsy, which is often overlooked. Early diagnosis and start of therapy improve quality of life. This study aimed to characterize oculomotor dysfunction of NPC patients, and to provide ophthalmologic data including retinal imaging.

METHODS

Eighteen patients with biochemically or genetically diagnosed NPC completed oculomotor and ophthalmologic examination. Ten of them performed saccadometry by infrared based video-oculography. Saccadic parameters were compared to 100 healthy controls, and were correlated with clinical variables. Another subgroup of eight patients received optical coherence tomography (OCT) of the optic disc and the macula, of which the segmented layers were analysed using a crude linear mixed model, and one adjusted for age, sex, and spherical equivalent.

RESULTS

Saccadometry revealed slowed peak velocity compared to controls most evident vertically. Peak velocity correlated negatively with SARA-Score, but correlation with clinical assessment of saccades was not significant. Clinical features in the assessment of vertical saccades were intensive blinking and head movements to initiate gaze changes, and lateral trajectory of the eyes. Macular OCT revealed significant total retinal thinning in the fovea, specifically of the outer nuclear layer and outer retinal layer. Para- and perifoveal retinal thicknesses, as well as peripapillary retinal nerve fibre layer were normal.

CONCLUSIONS

Foveal thinning was revealed in NPC. It remains to be shown, whether OCT will prove to be useful to monitor progression. Saccadic impairment reflects CNS involvement and therefore is a parameter to demonstrate the progression of NPC, and potentially also the efficacy of new therapies. Saccadometry, in contrast to clinical investigation, allows the precise evaluation of saccades.

Niemann-Pick Disease Type C Misdiagnosed as Cerebral Palsy: A Case Report

Niemann-Pick disease type C (NP-C) is a rare autosomal recessive neurovisceral lysosomal lipid storage disorder. The clinical manifestations of the disorder are variable. This report describes the case of a 27-month-old girl with NP-C whose condition had been misdiagnosed as spastic cerebral palsy (CP). She had spasticity, particularly at both ankles, and gait disturbance. Magnetic resonance imaging of the brain revealed findings suspicious of sequelae from a previous insult, such as periventricular leukomalacia, leading to the diagnosis of CP. However, she had a history of hepatosplenomegaly when she was a fetus and her motor development had deteriorated, with symptoms of vertical supranuclear gaze palsy, cataplexy, and ataxia developing gradually. Therefore, NP-C was considered and confirmed with a genetic study, which showed mutation of the NPC1 gene. Thus, if a child with CP-like symptoms presents with a deteriorating course and NP-C-specific symptoms, NP-C should be cautiously considered.

Expanded access with intravenous hydroxypropyl-β-cyclodextrin to treat children and young adults with Niemann-Pick disease type C1: a case report analysis

Background

Niemann-Pick Disease Type C (NPC) is an inherited, often fatal neurovisceral lysosomal storage disease characterized by cholesterol accumulation in every cell with few known treatments. Defects in cholesterol transport cause sequestration of unesterified cholesterol within the endolysosomal system. The discovery that systemic administration of hydroxypropyl-beta cyclodextrin (HPβPD) to NPC mice could release trapped cholesterol from lysosomes, normalize cholesterol levels in the liver, and prolong life, led to expanded access use in NPC patients. HPβCD has been administered to NPC patients with approved INDs globally since 2009.

Results

Here we present safety, tolerability and efficacy data from 12 patients treated intravenously (IV) for over 7 years with HPβCD in the US and Brazil. Some patients subsequently received intrathecal (IT) treatment with HPβCD following on average 13 months of IV HPβCD. Several patients transitioned to an alternate HPβCD. Moderately affected NPC patients treated with HPβCD showed slowing of disease progression. Severely affected patients demonstrated periods of stability but eventually showed progression of disease. Neurologic and neurocognitive benefits were seen in most patients with IV alone, independent of the addition of IT administration. Physicians and caregivers reported improvements in quality of life for the patients on IV therapy. There were no safety issues, and the drug was well tolerated and easy to administer.

Conclusions

These expanded access data support the safety and potential benefit of systemic IV administration of HPβCD and provide a platform for two clinical trials to study the effect of intravenous administration of HPβCD in NPC patients.

Slowed vertical saccades as a hallmark of hereditary spastic paraplegia type 7

Anecdotal oculomotor disturbances have been described in spastic paraplegia type 7 (SPG7). We investigated oculomotor and vestibular dysfunction in five patients with genetically verified SPG7. All five patients exhibited significantly slower velocities of vertical saccades compared to controls, but significantly faster than in progressive supranuclear palsy, with upward saccades being particularly affected. Horizontal saccades, cerebellar oculomotor markers, and vestibuloocular reflex seem to be variably affected. Thus, albeit subclinical in some cases, slowing of the vertical saccades may belong to the phenotype of SPG7 and may serve as a valuable biomarker for differentiation from spastic ataxias and atypical parkinsonism.

Behavioral Variant Frontotemporal Dementia Performance on a Range of Saccadic Tasks

BACKGROUND

Saccadic paradigms display changes across a number of degenerative conditions reflecting changes in the oculomotor pathway which in some conditions have been linked to disease presentation.

OBJECTIVE

To examine a novel range of saccadic paradigms in behavioral variant frontotemporal dementia (bvFTD).

METHODS

Prosaccade, predictive, self-paced, memory-guided, and anti-saccade tasks were examined in bvFTD patients and controls.

RESULTS

A significant increase in latency for the bvFTD group was seen in all tasks. Self-paced saccades are reduced in number, memory-guided saccades display an increase in errors. Predictive saccades show an increased latency that does not remain when prosaccade latency changes are accounted for. While changes were seen across a range of paradigms, no individual task completely separated bvFTD from control participants.

CONCLUSION

bvFTD patients as a group display a number of changes on saccadic testing which may reflect the frontal lobe changes seen in this condition.

Slow saccades in cerebellar disease

Eye movements are frequently considered diagnostic markers indicating involvement of the cerebellum. Impaired amplitude of saccades (saccade dysmetria), impaired gaze holding function (horizontal or downbeat nystagmus), and interrupted (choppy) pursuit are typically considered hallmarks of cerebellar disorders. While saccade dysmetria is a frequently considered abnormality, the velocity of saccades are rarely considered part of the constellation of cerebellar involvement. Reduced saccade velocity, frequently called “slow saccades” are typically seen in a classic disorder of the midbrain called progressive supranuclear palsy. It is also traditionally diagnostic of spinocerebellar ataxia type 2. In addition to its common causes, the slowness of vertical saccades is not rare in cerebellar disorders. Frequently this phenomenology is seen in multisystem involvement that substantially involves the cerebellum. In this review we will first discuss the physiological basis and the biological need for high saccade velocities. In subsequent sections we will discuss disorders of cerebellum that are known to cause slowing of saccades. We will then discuss possible pathology and novel therapeutic strategies.

Screening for Niemann-Pick Type C Disease in a Memory Clinic Cohort

Niemann-Pick type C disease (NPC) is a neurovisceral lysosomal storage disorder with a heterogeneous phenotype including ataxia, cognitive impairment, impairment of vertical saccades, and psychiatric symptoms, among many others. Based on clinical, genetic, and biomarker findings, recent guidelines put forward a screening for atypical and oligosymptomatic forms of NPC in clinical niches with an increased risk. Here, we report methods and results of a negative screening study in the niche of a memory clinic. We retrospectively and prospectively identified 83 patients with unclassified cognitive impairment (15 dementia, 46 mild cognitive impairment, and 22 progressive subjective cognitive decline) before 60 years of age (82 patients between 41 and 60 years). We explored the prevalence of clinical features compatible with NPC and measured plasma levels of chitotriosidase and cholestantriol. The NPC suspicion index indicated high probability for NPC in 3 and moderate probability in 16 patients. Prevalent (>5%) neurological and psychiatric features were depression, seizures, ataxia, dysarthria, and psychotic symptoms. Vertical gaze palsy without parkinsonism was observed in one patient. Cholestantriol levels were only abnormal in one patient. Chitotriosidase levels were susceptible to slight elevations that were reproducible in only two of five patients. Our study does not exclude NPC among memory clinic patients. Instead, we suggest conducting prospective screening studies in younger cohorts that include a focused neurological examination. Excluding minor cognitive impairment and discarding depression as an independent disease symptom probably further improve screening effectivity but may delay or miss therapeutic options in early or mild disease.

Oculomotor apraxia and disrupted sleep with nocturnal ballistic bouts in ADCY5-related disease

OBJECTIVE

To characterise the distinctive eye movement disorder and the sleep-related dyskinesia in Adenylate cyclase 5 (ADCY5) related disease.

METHODS

Formal eye movement examination and video-polysomnography in a cohort of patients with ADCY5 mutations.

RESULTS

All three patients had an eye movement disorder characterised by oculomotor apraxia with gaze limitation most prominently in the vertical plane. All patients had disrupted sleep architecture with reduced sleep efficiency due to frequent and prolonged arousals and awakenings in the context of dyskinesia, which could arise from any sleep stage. The nocturnal movements could last up to 30 min and be more severe than those seen during day-time.

CONCLUSION

Nocturnal exacerbations of dyskinesia ("ballistic bouts") seem to be a characteristic feature of the disease, affect the quality of life of patients and therefore require awareness and symptomatic treatment approaches. Apraxia of eye movements, with predominant difficulties in the vertical plane, was a common finding in our patients with ADCY5 mutations. These features may prompt the diagnosis and help to distinguish ADCY5-related disease from other childhood-onset hyperkinetic movement disorders.

Oculomotor abnormalities in children with Niemann-Pick type C

Niemann-Pick type C (NP-C) is a rare recessive disorder associated with progressive supranuclear gaze palsy. Degeneration occurs initially for vertical saccades and later for horizontal saccades. There are studies of oculomotor degeneration in adult NP-C patients [1, 2] but no comparable studies in children. We used high-resolution video-based eye tracking to record monocular vertical and horizontal eye movements in 2 neurological NP-C patients (children with clinically observable oculomotor abnormalities) and 3 pre-neurological NP-C patients (children without clinically observable oculomotor abnormalities). Saccade onset latency, saccade peak velocity and saccade curvature were compared to healthy controls (N=77). NP-C patients had selective impairments of vertical saccade peak velocity and vertical saccade curvature, with slower peak velocities and greater curvature. Changes were more pronounced in neurological than pre-neurological patients, showing that these measures are sensitive to disease progress, but abnormal curvature and slowed downward saccades were present in both groups, showing that eye-tracking can register disease-related changes before these are evident in a clinical exam. Both slowing, curvature and the detailed characteristics of the curvature we observed are predicted by the detailed characteristics of RIMLF population codes. Onset latencies were not different from healthy controls. High-resolution video-based eye tracking is a promising sensitive and objective method to measure NP-C disease severity and neurological onset. It may also help evaluate responses to therapeutic interventions.

Oculomotor and Vestibular Findings in Gaucher Disease Type 3 and Their Correlation with Neurological Findings

Objectives

To evaluate the function of the oculomotor and vestibular systems and to correlate these findings with the clinical status of patients with Gaucher disease type 3 (GD3). The goal of this cross-sectional and longitudinal study was to find oculomotor biomarkers for future clinical trials.

Methods

Twenty-six patients with GD3 were assessed for eligibility and 21 were able to perform at least one task. Horizontal and vertical reflexive saccades, smooth pursuit, gaze-holding, optokinetic nystagmus, and horizontal vestibulo-ocular reflex (VOR) were examined by video-oculography/video-head impulse test and compared concurrently with 33 healthy controls. The Scale for the Assessment and Rating of Ataxia (SARA), the modified Severity Scoring Tool (mSST), and Grooved Pegboard Test (GPT) were administered to assess overall neurological function. Eleven patients were also re-assessed after 1 year.

Results

Nine out of 17 patients exhibited gaze-holding deficits. One patient had upbeat nystagmus. Three patients presented with bilateral abducens palsy in combination with central oculomotor disorders, suggesting a bilateral involvement of the abducens nucleus. Horizontal angular VOR gain was reduced in all patients (0.66 ± 0.37) compared with controls (1.1 ± 0.11, p < 0.001). Most strongly correlated with clinical rating scales were peak velocity of downward saccades (SARA: ρ = −0.752, p < 0.0005; mSST: ρ = −0.611, p = 0.003; GPT: ρ = −0.649, p = 0.005) and duration of vertical saccades (SARA: ρ = 0.806, p < 0.001; mSST: ρ = 0.700, p < 0.0005; GPT: ρ = 0.558, p = 0.02) together with the VOR gain (SARA: ρ = −0.63, p = 0.016; mSST: ρ = −0.725, p = 0.003; GPT: ρ = −0.666, p = 0.004). Vertical smooth pursuit gain decreased significantly at follow-up.

Interpretation

This study shows neuronal degeneration of the brainstem and cerebellum with combined involvement of both supranuclear and nuclear oculomotor structures and the vestibular system in GD3. We also identified oculomotor parameters that correlate with the neurological status and can be used as biomarkers in future clinical trials.

Basic and translational neuro-ophthalmology of visually guided saccades: disorders of velocity

INTRODUCTION

Saccades are rapid, yoked eye movements in an effort to direct a target over fovea. The complex circuitry of saccadic eye movements has been exhaustively described. As a result clinicians can elegantly localize the pathology if it falls on the neuraxis responsible for saccades. Traditionally saccades are studied with their quantitative characteristics such as amplitude, velocity, duration, direction, latency and accuracy.

AREAS COVERED

Amongst all subtypes, the physiology of the visually guided saccades is most extensively studied. Here we will review the basic and pertinent neuro-anatomy and physiology of visually guided saccade and then discuss common or classic disorders affecting the velocity of visually guided saccades. We will then discuss the basic mechanism for saccade slowing in these disorders.

EXPERT COMMENTARY

Prompt appreciation of disorders of saccade velocity is critical to reach appropriate diagnosis. Disorders of midbrain, cerebellum, or basal ganglia can lead to prolonged transition time during gaze shift and decreased saccade velocity.

Clinical Approach to Supranuclear Brainstem Saccadic Gaze Palsies

Failure of brainstem supranuclear centers for saccadic eye movements results in the clinical presence of a brainstem-mediated supranuclear saccadic gaze palsy (SGP), which is manifested as slowing of saccades with or without range of motion limitation of eye movements and as loss of quick phases of optokinetic nystagmus. Limitation in the range of motion of eye movements is typically worse with saccades than with smooth pursuit and is overcome with vestibular–ocular reflexive eye movements. The differential diagnosis of SGPs is broad, although acute-onset SGP is most often from brainstem infarction and chronic vertical SGP is most commonly caused by the neurodegenerative condition progressive supranuclear palsy. In this review, we discuss the brainstem anatomy and physiology of the brainstem saccade-generating network; we discuss the clinical features of SGPs, with an emphasis on insights from quantitative ocular motor recordings; and we consider the broad differential diagnosis of SGPs.

Saccadic Impairments in Patients with the Norrbottnian Form of Gaucher's Disease Type 3

Background

Chronic neuronopathic Gaucher’s disease type 3 (GD3) is relatively frequent in northern Sweden. Besides multiple other neurological symptoms, horizontal gaze palsy or oculomotor apraxia is common in GD3.

Objective

To characterize the saccades in patients with Norrbottnian GD3 with respect to their neurological and cognitive status using a computer-based eye-tracking technique.

Methods

Horizontal and vertical reflexive saccades as well as antisaccades of nine GD3 patients [4M/5F; 41.1 ± 11.0 years; modified severity scoring tool (mSST): 9.3 ± 5.4; Montreal Cognitive Assessment (MoCA): 24.0 ± 4.2] and age-matched controls were analyzed using EyeBrain T2, a head-mounted binocular eye tracker. Systematic clinical assessment included the mSST, a valid tool for monitoring the neurological progression in GD3 and MoCA.

Results

In Norrbottnian GD3 patients, gain, peak, and average velocity (107.5°/s ± 41.8 vs. 283.9°/s ± 17.0; p = 0.0009) of horizontal saccades were reduced compared to healthy controls (HCs). Regarding vertical saccades, only the average velocity of downward saccades was decreased (128.6°/s ± 63.4 vs. 244.1°/s ± 50.8; p = 0.004). Vertical and horizontal saccadic latencies were increased (294.3 ms ± 37.0 vs. 236.5 ms ± 22.4; p = 0.005) and the latency of horizontal reflexive saccades was correlated with the mSST score (R² = 0.80; p = 0.003). The latency of antisaccades showed association to MoCA score (R² = 0.70; p = 0.009). GD3 patients made more errors in the antisaccade task (41.5 ± 27.6% vs. 5.2 ± 5.8%; p = 0.005), and the error rate tended to correlate with the cognitive function measured in MoCA score (p = 0.06).

Conclusion

The mean age of 41 years of our GD3 cohort reflects the increased life expectancy of patients in the Norrbottnian area compared to other GD3 cohorts. Marked impairment of horizontal saccades was evident in all patients, whereas vertical saccades showed distinct impairment of downward velocity. Latency of reflexive saccades was associated with the severity of neurological symptoms. Increased latency and error rate in the antisaccade task were linked to cognitive impairment. The assessment of saccades provides markers for neurological and neuropsychological involvement in Norrbottnian GD3.

The hidden Niemann-Pick type C patient: clinical niches for a rare inherited metabolic disease

BACKGROUND

Niemann-Pick disease type C (NP-C) is a rare, inherited neurodegenerative disease of impaired intracellular lipid trafficking. Clinical symptoms are highly heterogeneous, including neurological, visceral, or psychiatric manifestations. The incidence of NP-C is under-estimated due to under-recognition or misdiagnosis across a wide range of medical fields. New screening and diagnostic methods provide an opportunity to improve detection of unrecognized cases in clinical sub-populations associated with a higher risk of NP-C. Patients in these at-risk groups ("clinical niches") have symptoms that are potentially related to NP-C, but go unrecognized due to other, more prevalent clinical features, and lack of awareness regarding underlying metabolic causes.

METHODS

Twelve potential clinical niches identified by clinical experts were evaluated based on a comprehensive, non-systematic review of literature published to date. Relevant publications were identified by targeted literature searches of EMBASE and PubMed using key search terms specific to each niche. Articles published in English or other European languages up to 2016 were included.

FINDINGS

Several niches were found to be relevant based on available data: movement disorders (early-onset ataxia and dystonia), organic psychosis, early-onset cholestasis/(hepato)splenomegaly, cases with relevant antenatal findings or fetal abnormalities, and patients affected by family history, consanguinity, and endogamy. Potentially relevant niches requiring further supportive data included: early-onset cognitive decline, frontotemporal dementia, parkinsonism, and chronic inflammatory CNS disease. There was relatively weak evidence to suggest amyotrophic lateral sclerosis or progressive supranuclear gaze palsy as potential niches.

CONCLUSIONS

Several clinical niches have been identified that harbor patients at increased risk of NP-C.

Two Siblings with Adolescent/Adult Onset Niemann-Pick Disease Type C in Korea

Niemann-Pick disease, type C (NP-C), is caused by NPC1 or NPC2 gene mutations. Progressive neurological, psychiatric, and visceral symptoms are characteristic. Here, we present cases of a brother (Case 1) and sister (Case 2) in their mid-20s with gait disturbance and psychosis. For the Case 1, neurological examination revealed dystonia, ataxia, vertical supranuclear-gaze palsy (VSGP), and global cognitive impairment. Case 2 showed milder, but similar symptoms, with cortical atrophy. Abdominal computed tomography showed hepatosplenomegaly in both cases. NPC1 gene sequencing revealed compound heterozygote for exon 9 (c.1552C>T [R518W]) and exon 18 (c.2780C>T [A927V]). Filipin-staining tests were also positive. When a young patient with ataxia or dystonia shows VSGP, NP-C should be considered.

Observational cohort study of the natural history of Niemann-Pick disease type C in the UK: a 5-year update from the UK clinical database

BACKGROUND

Niemann-Pick disease type C (NP-C) is a rare neurovisceral lipid storage disorder characterised by progressive, disabling neurological symptoms and premature death in most patients. During the last decade, national cohort studies have accrued a great deal of data on the symptomatology and natural history of NP-C.

METHODS

In an observational cohort study, we present a substantial update based on the clinical presentation and follow-up of all known UK-based patients with a confirmed diagnosis of NP-C who have been tracked on an electronic database at the Department of Genetic Medicine, University of Manchester, UK. Patients were stratified according to accepted age-at-neurological-onset categories. Data on patients' clinical signs and symptoms, medical history and genetic studies are summarised using descriptive methods.

RESULTS

A total of 146 patients with NP-C were included, representing the full known UK NP-C cohort, as observed from database information between 1999 and the end of 2011: 72 patients (49 %) were alive at the end of the observation period. Among a total of 116 patients (79 %) who possessed at least one identified, disease-causing NP-C gene mutation, 114 (98 %) had NPC1 and two (2 %) had NPC2 mutations. Overall, 53/194 (27 %) identified mutations were novel. Six patients (4 %) had an early, non-neurological neonatal onset form of NP-C. The numbers (%) of patients with accepted age-at-neurological onset forms were: 8 (5 %) early-infantile onset, 51 (35 %) late-infantile onset, 42 (29 %) juvenile onset, and 25 (17 %) adolescent/adult onset. Fourteen patients diagnosed based on visceral symptoms and/or sibling history, confirmed in most cases by genetic analysis, did not have any neurological manifestations at last follow up (11 patients with mean [SD] age at last follow up 2.5 [1.8] years: 3 with mean [SD] age at death 20.8 [15.9] years). A total of 51 patients (35 %) received miglustat therapy. The mean (SD) overall treatment duration up to the end of the observation period was 2.6 (2.3) years.

CONCLUSIONS

This UK cohort is the largest national NP-C cohort reported to date, and confirms the wide phenotypic variability of the disease, as reported in other countries. Further analyses are required to assess the impact of miglustat therapy on neurological disease progression.

The diagnostic value of saccades in movement disorder patients: a practical guide and review

Saccades are rapid eye movements designed to shift the fovea to objects of visual interest. Abnormalities of saccades offer important clues in the diagnosis of a number of movement disorders. In this review, we explore the anatomy of horizontal and vertical saccades, discuss practical aspects of their examination, and review how saccadic abnormalities in hyperkinetic and hypokinetic movement disorders aid in diagnosis, with video demonstration of classic examples. Documentation of the ease of saccade initiation, range of motion and conjugacy of saccades, speed and accuracy of saccades, dynamic saccadic trajectory, and the presence or absence of saccadic intrusions and oscillations are important components of this exam. We also provide a practical algorithm to demonstrate the value of saccades in the differential diagnosis of the movement disorders patient.

Lacritin and other autophagy associated proteins in ocular surface health

Advantage may be taken of macroautophagy ('autophagy') to promote ocular health. Autophagy continually captures aged or damaged cellular material for lysosomal degradation and recyling. When autophagic flux is chronically elevated, or alternatively deficient, health suffers. Chronic elevation of flux and stress are the consequence of inflammatory cytokines or of dry eye tears but not normal tears invitro. Exogenous tear protein lacritin transiently accelerates flux to restore homeostasis invitro and corneal health invivo, and yet the monomeric active form of lacritin appears to be selectively deficient in dry eye. Tissue transglutaminase-dependent cross-linking of monomer decreases monomer quantity and monomer affinity for coreceptor syndecan-1 thereby abrogating activity. Tissue transglutaminase is elevated in dry eye. Mutation of arylsulfatase A, arylsulfatase B, ceroid-lipofuscinosis neuronal 3, mucolipin, or Niemann-Pick disease type C1 respectively underlie several diseases of apparently insufficient autophagic flux that affect the eye, including: metachromatic leukodystrophy, mucopolysaccharidosis type VI, juvenile-onset Batten disease, mucolipidosis IV, and Niemann-Pick type C associated with myelin sheath destruction of corneal sensory and ciliary nerves and of the optic nerve; corneal clouding, ocular hypertension, glaucoma and optic nerve atrophy; accumulation of 'ceroid-lipofuscin' in surface conjunctival cells, and in ganglion and neuronal cells; decreased visual acuity and retinal dystrophy; and neurodegeneration. For some, enzyme or gene replacement, or substrate reduction, therapy is proving to be successful. Here we discuss examples of restoring ocular surface homeostasis through alteration of autophagy, with particular attention to lacritin.

Central ocular motor disorders, including gaze palsy and nystagmus

An impairment of eye movements, or nystagmus, is seen in many diseases of the central nervous system, in particular those affecting the brainstem and cerebellum, as well as in those of the vestibular system. The key to diagnosis is a systematic clinical examination of the different types of eye movements, including: eye position, range of eye movements, smooth pursuit, saccades, gaze-holding function and optokinetic nystagmus, as well as testing for the different types of nystagmus (e.g., central fixation nystagmus or peripheral vestibular nystagmus). Depending on the time course of the signs and symptoms, eye movements often indicate a specific underlying cause (e.g., stroke or neurodegenerative or metabolic disorders). A detailed knowledge of the anatomy and physiology of eye movements enables the physician to localize the disturbance to a specific area in the brainstem (midbrain, pons or medulla) or cerebellum (in particular the flocculus). For example, isolated dysfunction of vertical eye movements is due to a midbrain lesion affecting the rostral interstitial nucleus of the medial longitudinal fascicle, with impaired vertical saccades only, the interstitial nucleus of Cajal or the posterior commissure; common causes with an acute onset are an infarction or bleeding in the upper midbrain or in patients with chronic progressive supranuclear palsy (PSP) and Niemann-Pick type C (NP-C). Isolated dysfunction of horizontal saccades is due to a pontine lesion affecting the paramedian pontine reticular formation due, for instance, to brainstem bleeding, glioma or Gaucher disease type 3; an impairment of horizontal and vertical saccades is found in later stages of PSP, NP-C and Gaucher disease type 3. Gaze-evoked nystagmus (GEN) in all directions indicates a cerebellar dysfunction and can have multiple causes such as drugs, in particular antiepileptics, chronic alcohol abuse, neurodegenerative cerebellar disorders or cerebellar ataxias; purely vertical GEN is due to a midbrain lesion, while purely horizontal GEN is due to a pontomedullary lesion. The pathognomonic clinical sign of internuclear ophthalmoplegia is an impaired adduction while testing horizontal saccades on the side of the lesion in the ipsilateral medial longitudinal fascicule. The most common pathological types of central nystagmus are downbeat nystagmus (DBN) and upbeat nystagmus (UBN). DBN is generally due to cerebellar dysfunction affecting the flocculus bilaterally (e.g., due to a neurodegenerative disease). Treatment options exist for a few disorders: miglustat for NP-C and aminopyridines for DBN and UBN. It is therefore particularly important to identify treatable cases with these conditions.

Niemann-Pick disease type C symptomatology: an expert-based clinical description

Niemann-Pick disease type C (NP-C) is a rare, progressive, irreversible disease leading to disabling neurological manifestations and premature death. The estimated disease incidence is 1:120,000 live births, but this likely represents an underestimate, as the disease may be under-diagnosed due to its highly heterogeneous presentation. NP-C is characterised by visceral, neurological and psychiatric manifestations that are not specific to the disease and that can be found in other conditions. The aim of this review is to provide non-specialists with an expert-based, detailed description of NP-C signs and symptoms, including how they present in patients and how they can be assessed. Early disease detection should rely on seeking a combination of signs and symptoms, rather than isolated findings. Examples of combinations which are strongly suggestive of NP-C include: splenomegaly and vertical supranuclear gaze palsy (VSGP); splenomegaly and clumsiness; splenomegaly and schizophrenia-like psychosis; psychotic symptoms and cognitive decline; and ataxia with dystonia, dysarthria/dysphagia and cognitive decline. VSGP is a hallmark of NP-C and becomes highly specific of the disease when it occurs in combination with other manifestations (e.g. splenomegaly, ataxia). In young infants (<2 years), abnormal saccades may first manifest as slowing and shortening of upward saccades, long before gaze palsy onset. While visceral manifestations tend to predominate during the perinatal and infantile period (2 months-6 years of age), neurological and psychiatric involvement is more prominent during the juvenile/adult period (>6 years of age). Psychosis in NP-C is atypical and variably responsive to treatment. Progressive cognitive decline, which always occurs in patients with NP-C, manifests as memory and executive impairment in juvenile/adult patients. Disease prognosis mainly correlates with the age at onset of the neurological signs, with early-onset forms progressing faster. Therefore, a detailed and descriptive picture of NP-C signs and symptoms may help improve disease detection and early diagnosis, so that therapy with miglustat (Zavesca(®)), the only available treatment approved to date, can be started as soon as neurological symptoms appear, in order to slow disease progression.

Treatment of Niemann--pick type C disease by histone deacetylase inhibitors

Niemann-Pick type C disease (NPC) is a devastating, recessive, inherited disorder that causes accumulation of cholesterol and other lipids in late endosomes and lysosomes. Mutations in 2 genes, NPC1 and NPC2, are responsible for the disease, which affects about 1 in 120,000 live births. About 95% of patients have mutations in NPC1, a large polytopic membrane protein that is normally found in late endosomes. More than 200 missense mutations in NPC1 have been found in NPC patients. The disease is progressive, typically leading to death before the age of 20 years, although some affected individuals live well into adulthood. The disease affects peripheral organs, including the liver, spleen, and lungs, but the most severe symptoms are associated with neurological disease. There are some palliative treatments that slow progression of NPC disease. Recently, it was found that histone deacetylase (HDAC) inhibitors that are effective against HDACs 1, 2, and 3 can reduce the cholesterol accumulation in fibroblasts derived from NPC patients with mutations in NPC1. One example is vorinostat. As vorinostat is a Food and Drug Administration-approved drug for treatment of cutaneous T-cell lymphoma, this opens up the possibility that HDAC inhibitors could be repurposed for treatment of this rare disease. The mechanism of action of the HDAC inhibitors requires further study, but these drugs increase the level of the NPC1 protein. This may be due to post-translational stabilization of the NPC1 protein, allowing it to be transported out of the endoplasmic reticulum.

Unusually prominent horizontal gaze palsy in a case of Niemann-Pick type C disease

Niemann-Pick Type C disease (NPC) is a rare inherited metabolic disorder characterized by lipid accumulation and systemic manifestations due to multiple organ involvement. Only a few cases of NPC have been reported so far from India. Varying presentations and often lack of access to complex diagnostic tests have leaded to initial misdiagnosis on few occasions. We here report a provisionally diagnosed case of NPC with prominent horizontal gaze palsy along with characteristic vertical gaze palsy and normal findings on microscopic examination of skin biopsy specimen.