Vestibular Migraine of Childhood and Recurrent Vertigo of Childhood: Diagnostic criteria Consensus document of the Committee for the Classification of Vestibular Disorders of the Bárány Society and the International Headache Society

This paper describes the diagnostic criteria for “Vestibular Migraine of Childhood”, “probable Vestibular Migraine of Childhood” and “Recurrent Vertigo of Childhood” as put forth by the Committee for the Classification of Vestibular Disorders of the Bárány Society (ICVD) and the Migraine Classification subgroup of the International Headache Society. Migraine plays an important role in some subgroups of children with recurrent vertigo. In this classification paper a spectrum of three disorders is described in which the migraine component varies from definite to possibly absent. These three disorders are: Vestibular Migraine of Childhood, probable Vestibular Migraine of Childhood and Recurrent Vertigo of Childhood. The criteria for Vestibular Migraine of Childhood (VMC) include (A) at least five episodes with vestibular symptoms of moderate or severe intensity, lasting between five minutes and 72 hours, (B) a current or past history of migraine with or without aura, and (C) at least half of episodes are associated with at least one migraine feature. Probable Vestibular Migraine of Childhood (probable VMC) is considered when at least three episodes with vestibular symptoms of moderate or severe intensity, lasting between five minutes and 72 hours, are accompanied by at least criterion B or C from the VMC criteria. Recurrent Vertigo of Childhood (RVC) is diagnosed in case of at least three episodes with vestibular symptoms of moderate or severe intensity, lasting between 1 minute and 72 hours, and none of the criteria B and C for VMC are applicable. For all disorders, the age of the individual needs to be below 18 years old. It is recommended that future research should particularly focus on RVC, in order to investigate and identify possible subtypes and its links or its absence thereof with migraine.

Natural History, Phenotypic Spectrum, and Discriminative Features of Multisystemic RFC1 Disease

Objective

To delineate the full phenotypic spectrum, discriminative features, piloting longitudinal progression data, and sample size calculations of replication factor complex subunit 1 (RFC1) repeat expansions, recently identified as causing cerebellar ataxia, neuropathy, vestibular areflexia syndrome (CANVAS).

Methods

Multimodal RFC1 repeat screening (PCR, Southern blot, whole-exome/genome sequencing–based approaches) combined with cross-sectional and longitudinal deep phenotyping in (1) cross-European cohort A (70 families) with ≥2 features of CANVAS or ataxia with chronic cough (ACC) and (2) Turkish cohort B (105 families) with unselected late-onset ataxia.

Results

Prevalence of RFC1 disease was 67% in cohort A, 14% in unselected cohort B, 68% in clinical CANVAS, and 100% in ACC. RFC1 disease was also identified in Western and Eastern Asian individuals and even by whole-exome sequencing. Visual compensation, sensory symptoms, and cough were strong positive discriminative predictors (>90%) against RFC1-negative patients. The phenotype across 70 RFC1-positive patients was mostly multisystemic (69%), including dysautonomia (62%) and bradykinesia (28%) (overlap with cerebellar-type multiple system atrophy [MSA-C]), postural instability (49%), slow vertical saccades (17%), and chorea or dystonia (11%). Ataxia progression was ≈1.3 Scale for the Assessment and Rating of Ataxia points per year (32 cross-sectional, 17 longitudinal assessments, follow-up ≤9 years [mean 3.1 years]) but also included early falls, variable nonlinear phases of MSA-C–like progression (SARA points 2.5–5.5 per year), and premature death. Treatment trials require 330 (1-year trial) and 132 (2-year trial) patients in total to detect 50% reduced progression.

Conclusions

RFC1 disease is frequent and occurs across continents, with CANVAS and ACC as highly diagnostic phenotypes yet as variable, overlapping clusters along a continuous multisystemic disease spectrum, including MSA-C-overlap. Our natural history data help to inform future RFC1 treatment trials.

Classification of Evidence

This study provides Class II evidence that RFC1 repeat expansions are associated with CANVAS and ACC.

A master protocol to investigate a novel therapy acetyl-L-leucine for three ultra-rare neurodegenerative diseases: Niemann-Pick type C, the GM2 gangliosidoses, and ataxia telangiectasia

BACKGROUND

The lack of approved treatments for the majority of rare diseases is reflective of the unique challenges of orphan drug development. Novel methodologies, including new functionally relevant endpoints, are needed to render the development process more feasible and appropriate for these rare populations and thereby expedite the approval of promising treatments to address patients' high unmet medical need. Here, we describe the development of an innovative master protocol and primary outcome assessment to investigate the modified amino acid N-acetyl-L-leucine (Sponsor Code: IB1001) in three separate, multinational, phase II trials for three ultra-rare, autosomal-recessive, neurodegenerative disorders: Niemann-Pick disease type C (NPC), GM2 gangliosidoses (Tay-Sachs and Sandhoff disease; "GM2"), and ataxia telangiectasia (A-T).

METHODS/DESIGN

The innovative IB1001 master protocol and novel CI-CS primary endpoints were developed through a close collaboration between the Industry Sponsor, Key Opinion Leaders, representatives of the Patient Communities, and National Regulatory Authorities. As a result, the open-label, rater-blinded study design is considerate of the practical limitations of recruitment and retention of subjects in these ultra-orphan populations. The novel primary endpoint, the Clinical Impression of Change in Severity© (CI-CS), accommodates the heterogenous clinical presentation of NPC, GM2, and A-T: at screening, the principal investigator appoints for each patient a primary anchor test (either the 8-m walk test (8MWT) or 9-hole peg test of the dominant hand (9HPT-D)) based on his/her unique clinical symptoms. The anchor tests are videoed in a standardized manner at each visit to capture all aspects related to the patient's functional performance. The CI-CS assessment is ultimately performed by independent, blinded raters who compare videos of the primary anchor test from three periods: baseline, the end of treatment, and the end of a post-treatment washout. Blinded to the time point of each video, the raters make an objective comparison scored on a 7-point Likert scale of the change in the severity of the patient's neurological signs and symptoms from video A to video B. To investigate both the symptomatic and disease-modifying effects of treatment, N-acetyl-L-leucine is assessed during two treatment sequences: a 6-week parent study and 1-year extension phase.

DISCUSSION

The novel CI-CS assessment, developed through a collaboration of all stakeholders, is advantageous in that it better ensures the primary endpoint is functionally relevant for each patient, is able to capture small but meaningful clinical changes critical to the patients' quality of life (fine-motor skills; gait), and blinds the primary outcome assessment. The results of these three trials will inform whether N-acetyl-L-leucine is an effective treatment for NPC, GM2, and A-T and can also serve as a new therapeutic paradigm for the development of future treatments for other orphan diseases.

TRIAL REGISTRATION

The three trials (IB1001-201 for Niemann-Pick disease type C (NPC), IB1001-202 for GM2 gangliosidoses (Tay-Sachs and Sandhoff), IB1001-203 for ataxia telangiectasia (A-T)) have been registered at www.clinicaltrials.gov (NCT03759639; NCT03759665; NCT03759678), www.clinicaltrialsregister.eu (EudraCT: 2018-004331-71; 2018-004406-25; 2018-004407-39), and https://www.germanctr.de (DR KS-ID: DRKS00016567; DRKS00017539; DRKS00020511).

Diagnosing vestibular hypofunction: an update

Unilateral or bilateral vestibular hypofunction presents most commonly with symptoms of dizziness or postural imbalance and affects a large population. However, it is often missed because no quantitative testing of vestibular function is performed, or misdiagnosed due to a lack of standardization of vestibular testing. Therefore, this article reviews the current status of the most frequently used vestibular tests for canal and otolith function. This information can also be used to reach a consensus about the systematic diagnosis of vestibular hypofunction.

Acetyl-leucine slows disease progression in lysosomal storage disorders

Acetyl-dl-leucine is a derivative of the branched chain amino acid leucine. In observational clinical studies, acetyl-dl-leucine improved symptoms of ataxia, in particular in patients with the lysosomal storage disorder, Niemann-Pick disease type C1. Here, we investigated acetyl-dl-leucine and its enantiomers acetyl-l-leucine and acetyl-d-leucine in symptomatic Npc1^-/- mice and observed improvement in ataxia with both individual enantiomers and acetyl-dl-leucine. When acetyl-dl-leucine and acetyl-l-leucine were administered pre-symptomatically to Npc1^-/- mice, both treatments delayed disease progression and extended life span, whereas acetyl-d-leucine did not. These data are consistent with acetyl-l-leucine being the neuroprotective enantiomer. Altered glucose and antioxidant metabolism were implicated as one of the potential mechanisms of action of the l-enantiomer in Npc1^-/- mice. When the standard of care drug miglustat and acetyl-dl-leucine were used in combination significant synergy resulted. In agreement with these pre-clinical data, when Niemann-Pick disease type C1 patients were evaluated after 12 months of acetyl-dl-leucine treatment, rates of disease progression were slowed, with stabilization or improvement in multiple neurological domains. A beneficial effect of acetyl-dl-leucine on gait was also observed in this study in a mouse model of GM2 gangliosidosis (Sandhoff disease) and in Tay-Sachs and Sandhoff disease patients in individual-cases of off-label-use. Taken together, we have identified an unanticipated neuroprotective effect of acetyl-l-leucine and underlying mechanisms of action in lysosomal storage diseases, supporting its further evaluation in clinical trials in lysosomal disorders.

Nystagmus goggles: how to use them, what you find and what it means

A fundamental characteristic of peripheral vestibular nystagmus, in particular horizontal nystagmus, is that it is suppressed by visual fixation. This means that a patient with a vertigo attack of peripheral vestibular origin might have no obvious spontaneous nystagmus on clinical examination. Goggles that reduce or remove visual fixation allow the cliniican to observe nystagmus in this situation. Nystagmus goggles are essential for any clinician dealing with dizzy patients. Here, we discuss why this is so and how easy it is to acquire and use them.

High-risk Allele for Herpes Labialis Severity at the IFNL3/4 Locus is Associated With Vestibular Neuritis

Objective: Vestibular neuritis (VN) is a peripheral vestibular disorder leading to a sudden loss of unilateral vestibular function. Although the underlying etiological mechanisms for disease development are not yet known, there is evidence that a latent infection with herpes simplex virus type 1 (HSV-1) might be involved. The polymorphism rs12979860 has been associated with the severity of recurrent herpes labialis and hepatitis C virus (HCV) clearance and treatment outcome and is located within the first intron of the IFNL4 gene on chromosome 19.q13.2. This case control study was conducted to evaluate the association of rs12979860 with VN occurrence.

Methods: DNA was extracted from EDTA blood of 151 VN patients and 1,775 healthy controls. Genotyping of rs12979860 was performed using iPLEX and MassARRAY Matrix Assisted Laser Desorption Ionization—Time of Flight (MALDI-TOF) mass spectrometry. For association analyses, an additive, dominant and recessive logistic regression model was calculated, using age and sex as covariates.

Results: A significant association of rs12979860 with VN was obtained for the additive [OR = 1.51 (1.18–1.92); p = 9.23 × 10⁻⁴] and dominant models [OR = 2.15 (1.48–3.13); p = 5.86 × 10⁻⁵], with the T allele being more frequent in the VN group.

Conclusion: By detecting a significant association of the rs12979860-T risk allele for herpes labialis severity with susceptibility to VN, this study gives further indirect evidence for an involvement of HSV-1 in VN pathology, thereby strengthening the virus hypothesis.

Management of Lateral Semicircular Canal Benign Paroxysmal Positional Vertigo

Benign paroxysmal positional vertigo (BPPV) is the most common cause of peripheral vestibular vertigo. It is caused by free-floating otoconia moving freely in one of the semicircular canals (canalolithiasis) or by otoliths adhered to the cupula (cupulolithiasis). The posterior canal is the most common canal affected, followed by the lateral canal. Diagnosis of the side affected is critical for successful treatment; therefore, suppressing visual fixation is essential to examination of these patients' eye movement. On the basis of our experience, we have adopted the Zuma maneuver and the modified Zuma maneuver for both apogeotropic and geotropic variants of lateral canal BPPV. Knowledge of the anatomy and pathophysiologic mechanisms of the semicircular canals is essential for correct management of these patients. Hence, using a single maneuver and its modification may facilitate daily neurotological practice.

The gait disorder in primary orthostatic tremor

OBJECTIVE

To uncover possible impairments of walking and dynamic postural stability in patients with primary orthostatic tremor (OT).

METHODS

Spatiotemporal gait characteristics were quantified in 18 patients with primary OT (mean age 70.5 ± 5.9 years, 10 females) and 18 age-matched healthy controls. One-third of patients reported disease-related fall events. Walking performance was assessed on a pressure-sensitive carpet under seven conditions: walking at preferred, slow, and maximal speed, with head reclination or eyes closed, and while performing a cognitive or motor dual-task paradigm.

RESULTS

Patients exhibited a significant gait impairment characterized by a broadened base of support (p = 0.018) with increased spatiotemporal gait variability (p = 0.010). Walking speed was moderately reduced (p = 0.026) with shortened stride length (p = 0.001) and increased periods of double support (p = 0.001). Gait dysfunction became more pronounced during slow walking (p < 0.001); this was not present during fast walking. Walking with eyes closed aggravated gait disability as did walking during cognitive dual task (p < 0.001).

CONCLUSION

OT is associated with a specific gait disorder with a staggering wide-based walking pattern indicative of a sensory and/or a cerebellar ataxic gait. The aggravation of gait instability during visual withdrawal and the normalization of walking with faster speeds further suggest a proprioceptive or vestibulo-cerebellar deficit as the primary source of gait disturbance in OT. In addition, the gait decline during cognitive dual task may imply cognitive processing deficits. In the end, OT is presumably a complex network disorder resulting in a specific spino-cerebello-frontocortical gait disorder that goes beyond mere tremor networks.

Hemodynamic orthostatic dizziness/vertigo: Diagnostic criteria

This paper presents the diagnostic criteria for hemodynamic orthostatic dizziness/vertigo to be included in the International Classification of Vestibular Disorders (ICVD). The aim of defining diagnostic criteria of hemodynamic orthostatic dizziness/vertigo is to help clinicians to understand the terminology related to orthostatic dizziness/vertigo and to distinguish orthostatic dizziness/vertigo due to global brain hypoperfusion from that caused by other etiologies. Diagnosis of hemodynamic orthostatic dizziness/vertigo requires: A) five or more episodes of dizziness, unsteadiness or vertigo triggered by arising or present during upright position, which subsides by sitting or lying down; B) orthostatic hypotension, postural tachycardia syndrome or syncope documented on standing or during head-up tilt test; and C) not better accounted for by another disease or disorder. Probable hemodynamic orthostatic dizziness/vertigo is defined as follows: A) five or more episodes of dizziness, unsteadiness or vertigo triggered by arising or present during upright position, which subsides by sitting or lying down; B) at least one of the following accompanying symptoms: generalized weakness/tiredness, difficulty in thinking/concentrating, blurred vision, and tachycardia/palpitations; and C) not better accounted for by another disease or disorder. These diagnostic criteria have been derived by expert consensus from an extensive review of 90 years of research on hemodynamic orthostatic dizziness/vertigo, postural hypotension or tachycardia, and autonomic dizziness. Measurements of orthostatic blood pressure and heart rate are important for the screening and documentation of orthostatic hypotension or postural tachycardia syndrome to establish the diagnosis of hemodynamic orthostatic dizziness/vertigo.

Medical and Paramedical Care of Patients With Cerebellar Ataxia During the COVID-19 Outbreak: Seven Practical Recommendations of the COVID 19 Cerebellum Task Force

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV2), the cause of the current pandemic coronavirus disease 2019 (COVID-19), primarily targets the respiratory system. Some patients also experience neurological signs and symptoms ranging from anosmia, ageusia, headache, nausea, and vomiting to confusion, encephalitis, and stroke. Approximately 36% of those with severe COVID-19 experience neurological complications. The virus may enter the central nervous system through the olfactory nerve in the nasal cavity and damage neurons in the brainstem nuclei involved in the regulation of respiration. Patients with cerebellar ataxia (CA) are particularly vulnerable to severe outcome if they contract COVID-19 because of the complexity of their disease, the presence of comorbidities, and their use of immunosuppressive therapies. Most CA patients burdened by progressive neurologic deficits have substantially impaired mobility and other essential functions, for which they rely heavily on ambulatory services, including rehabilitation and psychosocial care. Cessation of these interventions because of isolation restrictions places the CA patient population at risk of further deterioration. This international panel of ataxia experts provides recommendations for neurologists caring for patients with CA, emphasizing a pro-active approach designed to maintain their autonomy and well-being: continue long-term medications, promote rehabilitation efforts, utilize the technology of virtual visits for regular contact with healthcare providers, and pay attention to emotional and psychosocial health. Neurologists should play an active role in decision-making in those CA cases requiring escalation to intensive care and resuscitation. Multi-disciplinary collaboration between care teams is always important, and never more so than in the context of the current pandemic.

Vestibular Disorders

BACKGROUND

Recent research findings have improved the understanding of the diagnosis, pathophysiology, genetics, etiology, and treatment of peripheral, central, and functional vestibular vertigo syndromes.

METHOD

A literature search, with special attention to the current classification, treatment trials, Cochrane analyses, and other meta-analyses.

RESULTS

There are internationally accepted diagnostic criteria for benign positional paroxysmal vertigo, Menière's disease, bilateral vestibulopathy, vestibular paroxysmia, and functional dizziness. Whether an acute vestibular syndrome is central or peripheral can usually be determined rapidly on the basis of the history and the clinical examination. "Cere - bellar vertigo" is a clinically important entity. For bilateral vestibulopathy, balance training is an effective treatment. For Menière's disease, preventive treatment with betahistine (48 mg and 144 mg per day) is not superior to placebo. For vestibular paroxysmia, oxcarbazepine has been shown to be effective. Treatments that are probably effective for functional dizziness include vestibular rehabilitation, cognitive behavioral therapy, and serotonin reuptake inhibitors.

CONCLUSION

The diagnostic assessment of vestibular syndromes is much easier for clinicians now that it has been internationally standardized. There is still a lack of randomized, controlled trials on the treatment of, for example, Menière's disease, vestibular migraine, and "cerebellar vertigo."

Clinical, ocular motor, and imaging profile of Niemann-Pick type C heterozygosity

Objective

To characterize subclinical abnormalities in asymptomatic heterozygote NPC1 mutation carriers as markers of neurodegeneration.

Methods

Motor function, cognition, mood, sleep, and smell function were assessed in 20 first-degree heterozygous relatives of patients with Niemann-Pick disease type C (NPC) (13 male, age 52.7 ± 9.9 years). Video-oculography and abdominal ultrasound with volumetry were performed to assess oculomotor function and size of liver and spleen. NPC biomarkers in blood were analyzed. 18F-fluorodesoxyglucose PET was performed (n = 16) to detect patterns of brain hypometabolism.

Results

NPC heterozygotes recapitulated characteristic features of symptomatic NPC disease and demonstrated the oculomotor abnormalities typical of NPC. Hepatosplenomegaly (71%) and increased cholestantriol (33%) and plasma chitotriosidase (17%) levels were present. The patients also showed signs seen in other neurodegenerative diseases, including hyposmia (20%) or pathologic screening for REM sleep behavior disorder (24%). Cognitive function was frequently impaired, especially affecting visuoconstructive function, verbal fluency, and executive function. PET imaging revealed significantly decreased glucose metabolic rates in 50% of participants, affecting cerebellar, anterior cingulate, parieto-occipital, and temporal regions, including 1 with bilateral abnormalities.

Conclusion

NPC heterozygosity, which has a carrier frequency of 1:200 in the general population, is associated with abnormal brain metabolism and functional consequences. Clinically silent heterozygous gene variations in NPC1 may be a risk factor for late-onset neurodegeneration, similar to the concept of heterozygous GBA mutations underlying Parkinson disease.

Unexpected differences in the pharmacokinetics of N-acetyl-DL-leucine enantiomers after oral dosing and their clinical relevance

The enantiomers of many chiral drugs not only exhibit different pharmacological effects in regard to targets that dictate therapeutic and toxic effects, but are also handled differently in the body due to pharmacokinetic effects. We investigated the pharmacokinetics of the enantiomers of N-acetyl-leucine after administration of the racemate (N-acetyl-DL-leucine) or purified, pharmacologically active L-enantiomer (N-acetyl-L-leucine). The results suggest that during chronic administration of the racemate, the D-enantiomer would accumulate, which could have negative effects. Compounds were administered orally to mice. Plasma and tissue samples were collected at predetermined time points (0.25 to 8 h), quantified with liquid chromatography/mass spectrometry, and pharmacokinetic constants were calculated using a noncompartmental model. When administered as the racemate, both the maximum plasma concentration (Cmax) and the area under the plasma drug concentration over time curve (AUC) were much greater for the D-enantiomer relative to the L-enantiomer. When administered as the L-enantiomer, the dose proportionality was greater than unity compared to the racemate, suggesting saturable processes affecting uptake and/or metabolism. Elimination (ke and T1/2) was similar for both enantiomers. These results are most readily explained by inhibition of uptake at an intestinal carrier of the L-enantiomer by the D-enantiomer, and by first-pass metabolism of the L-, but not D-enantiomer, likely by deacetylation. In brain and muscle, N-acetyl-L-leucine levels were lower than N-acetyl-D-leucine, consistent with rapid conversion into L-leucine and utilization by normal leucine metabolism. In summary, the enantiomers of N-acetyl-leucine exhibit large, unexpected differences in pharmacokinetics due to both unique handling and/or inhibition of uptake and metabolism of the L-enantiomer by the D-enantiomer. Taken together, these results have clinical implications supporting the use of N-acetyl-L-leucine instead of the racemate or N-acetyl-D-leucine, and support the research and development of only N-acetyl-L-leucine.

Results and lessons learnt from a randomized controlled trial: prophylactic treatment of vestibular migraine with metoprolol (PROVEMIG)

Background

Vestibular migraine (VM) is the most frequent cause of recurrent spontaneous attacks of vertigo causally related to migraine. The objective of the Prophylactic treatment of vestibular migraine with metoprolol (PROVEMIG) trial was to demonstrate that metoprolol succinate is superior to placebo in the prevention of episodic vertigo- and migraine-related symptoms in patients with VM.

Methods

This phase III, two-arm, parallel-group, double-blind, randomized placebo-controlled trial was designed to be conducted at tertiary referral centres at neurology and ear, nose and throat departments of eight German university hospitals. The planned sample size was a total of 266 patients to be allocated. Adults aged 18 years or above diagnosed with probable or definitive VM according to the Neuhauser criteria 2001 were randomly assigned 1:1 to 6 months blinded metoprolol (maintenance dosage of 95 mg daily) or placebo. The primary efficacy outcome was the self-reported number of vertiginous attacks per 30 days documented by means of a paper-based daily symptom diary. The pre-specified time period of primary interest was defined as months 4 to 6. Secondary outcomes included the patient-reported number of migraine days and vertigo days, the Dizziness Handicap Inventory, and clinical assessments. Adverse events were reported throughout the whole 9-month study period.

Results

At the time of trial termination, no evidence for a difference in the incidence of vertiginous attacks between groups was detected. For the full analysis set, the incidence rate ratio was 0.983 (95% confidence interval (CI) 0.902–1.071) for metoprolol versus placebo. In both groups, there was a significant decline over time in the overall monthly vertigo attacks by a factor of 0.830 (95% CI 0.776–0.887). Results were consistent for all subjective and objective key measures of efficacy. The treatment was well tolerated with no unexpected safety findings.

Conclusions

After randomizing 130 patients PROVEMIG had to be discontinued because of poor participant accrual not related to the tolerability of the study medication or safety concerns; no treatment benefit of metoprolol over placebo could be established. Additional preparatory work is much needed in the development, psychometric evaluation and interpretation of clinically meaningful end points in trials on episodic syndromes like VM taking into consideration the complexity of this disease entity comprising two domains (vertigo- and headache-related disability).

Trial registration

EudraCT, 2009-013701-34. Prospectively registered on 8 April 2011.

Cerebellar Dizziness and Vertigo: Etiologies, Diagnostic Assessment, and Treatment

Cerebellar dizziness and vertigo account for approximately 10% of diagnoses in a tertiary dizziness center. This term summarizes a large group of disorders with chronic (degenerative, hereditary, acquired cerebellar ataxias), recurrent (episodic ataxias), or acute (stroke, inflammation) presentations. Key to the diagnosis is a comprehensive examination of central ocular motor and vestibular function. Patients with cerebellar dizziness and vertigo usually show a pattern of deficits in smooth pursuit, gaze-holding, saccade accuracy, or fixation-suppression of the vestibulo-ocular reflex. Central fixation nystagmus (e.g., downbeat nystagmus), gaze-evoked nystagmus, central positional nystagmus, or head-shaking nystagmus with cross-coupling (i.e., horizontal head shaking causing inappropriate vertical nystagmus) occurs frequently. Overlap syndromes with peripheral vestibular disorders, such as cerebellar ataxia, neuropathy, and vestibular areflexia, exist rarely. Posturography and gait analysis can contribute to diagnostic differentiation, estimation of the risk of falls, as well as quantification of progression and treatment effects. Patients with cerebellar dizziness and vertigo should receive multimodal treatment, including balance training, occupational therapy, and medication.

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

BACKGROUND/METHODS

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

RESULTS

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

DISCUSSION/CONCLUSION

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

Worldwide survey on laboratory testing of vestibular function

Background

The function of the peripheral vestibular system can nowadays be quantified. The video head impulse test (vHIT) and caloric irrigation are used for the semicircular canals, cervical vestibular evoked myogenic potentials (cVEMP) for the sacculus, and ocular vestibular evoked myogenic potentials (oVEMP) for the utriculus. Because there is no agreement on normal and pathologic values, we performed a worldwide survey.

Methods

A web-based standardized survey questionnaire was used to collect data on "reference values" and "cutoff" values. Thirty-eight centers from all continents (except Africa) replied.

Results

"Reference values": vHIT: mean for the vestibulo-ocular reflex gain of the left horizontal canal 0.91 (range: 0.7-1.01) and of the left horizontal canal 0.92 (0.7-1.05); side difference 0.15 (0.25-0.3). Caloric irrigation: mean peak slow phase velocity of caloric-induced nystagmus for warm (44°C) water 18.65°/s (12-30°/s); cold (30°C) water 18.21°/s (10-25°/s). cVEMP: P13-N23 amplitude mean for the lower limit 28.67 μV (16-50 μV); upper limit 200 μV (50-350 μV). "Cutoff values": vHIT: side difference 0.26 (0.1-0.4), bilateral vestibulopathy <0.61 (0.3-0.8); unilateral vestibulopathy (UVP) <0.68 (0.4-0.8). Caloric irrigation pathologic side difference mean 25.93% (17.7%-40%) or 12°/sec (5-30°/s); side difference UVP 26.73% (20%-40%) or 29.8°/s (5-100°/s). cVEMP: P13/N23 amplitude mean lower cutoff 32.5 μV (15-50 μV), mean upper cutoff 125 μV (50-200 μV), asymmetry 36.08 μV (20-50 μV).

Conclusion

This worldwide survey showed a large variability in terms of reference and pathologic cutoff values in the 38 centers included. Therefore, standardization of how to achieve these values and agreement on which values should be used is highly warranted to guarantee a high quality of vestibular testing and interpretation of clinical and scientific results.

Presbyvestibulopathy: Diagnostic criteria Consensus document of the classification committee of the Bárány Society

This paper describes the diagnostic criteria for presbyvestibulopathy (PVP) by the Classification Committee of the Bárány Society. PVP is defined as a chronic vestibular syndrome characterized by unsteadiness, gait disturbance, and/or recurrent falls in the presence of mild bilateral vestibular deficits, with findings on laboratory tests that are between normal values and thresholds established for bilateral vestibulopathy.

The diagnosis of PVP is based on the patient history, bedside examination and laboratory evaluation. The diagnosis of PVP requires bilaterally reduced function of the vestibulo-ocular reflex (VOR). This can be diagnosed for the high frequency range of the VOR with the video-HIT (vHIT); for the middle frequency range with rotary chair testing; and for the low frequency range with caloric testing.

For the diagnosis of PVP, the horizontal angular VOR gain on both sides should be < 0.8 and > 0.6, and/or the sum of the maximal peak velocities of the slow phase caloric-induced nystagmus for stimulation with warm and cold water on each side should be < 25°/s and > 6°/s, and/or the horizontal angular VOR gain should be > 0.1 and < 0.3 upon sinusoidal stimulation on a rotatory chair.

PVP typically occurs along with other age-related deficits of vision, proprioception, and/or cortical, cerebellar and extrapyramidal function which also contribute and might even be required for the manifestation of the symptoms of unsteadiness, gait disturbance, and falls. These criteria simply consider the presence of these symptoms, along with documented impairment of vestibular function, in older adults.