Balance Control Impairments in Usher Syndrome.

OBJECTIVES: To explore postural disability in Usher Syndrome (USH) patients using temporal posturographic analysis to better elucidate sensory compensation strategies of deafblind patients for posture control and correlate the Activities-specific Balance Confidence (ABC) scale with posturographic variables. DESIGN: Thirty-four genetically confirmed USH patients (11 USH1, 21 USH2, 2 USH 4) from the Otolaryngology Outpatient Clinic and 35 controls were prospectively studied using both classical and wavelet temporal analysis of center of pressure (CoP) under different visual conditions on static and dynamic platforms. The functional impact of balance was assessed with the ABC scale. Classical data in the spatial domain, Sensorial Organization Test, and frequency analysis of the CoP were analyzed. RESULTS: On unstable surfaces, USH1 had greater CoP surface area with eyes open (38.51 ± 68.67) and closed (28.14 ± 31.64) versus controls (3.31 ± 4.60), p < 0.001 and (7.37 ± 7.91), p < 0.001, respectively. On an unstable platform, USH consistently showed increased postural sway, with elevated angular velocity versus controls with eyes open (USH1 [44.94 ± 62.54]; USH2 [55.64 ± 38.61]; controls [13.4 ± 8.57]) (p = 0.003; p < 0.001) and closed (USH1 [60.36 ± 49.85], USH2 [57.62 ± 42.36]; controls [27.31 ± 19.79]) (p = 0.002; p = 0.042). USH visual impairment appears to be the primary factor influencing postural deficits, with a statistically significant difference observed in the visual Sensorial Organization Test ratio for USH1 (80.73 ± 40.07, p = 0.04) and a highly significant difference for USH2 (75.48 ± 31.67, p < 0.001) versus controls (100). In contrast, vestibular (p = 0.08) and somatosensory (p = 0.537) factors did not reach statistical significance. USH exhibited lower visual dependence than controls (30.31 ± 30.08) (USH1 [6 ± 11.46], p = 0.004; USH2 [8 ± 14.15], p = 0.005). The postural instability index, that corresponds to the ratio of spectral power index and canceling time, differentiated USH from controls on unstable surface with eyes open USH1 (3.33 ± 1.85) p < 0.001; USH2 (3.87 ± 1.05) p < 0.002; controls (1.91 ± 0.85) and closed USH1 (3.91 ± 1.65) p = 0.005; USH2 (3.92 ± 1.05) p = 0.045; controls (2.74 ± 1.27), but not USH1 from USH2. The canceling time in the anteroposterior direction in lower zone distinguished USH subtypes on stable surface with optokinetic USH1 (0.88 ± 1.03), USH2 (0.29 ± 0.23), p = 0.026 and on unstable surface with eyes open USH1 (0.56 ± 1.26), USH2 (0.072 ± 0.09), p = 0.036. ABC scale could distinguish between USH patients and controls, but not between USH subtypes and it correlated with CoP surface area on unstable surface with eyes open only in USH1(ρ = 0.714, p = 0.047). CONCLUSIONS: USH patients, particularly USH1, exhibited poorer balance control than controls on unstable platform with eyes open and appeared to rely more on proprioceptive information while suppressing visual input. USH2 seems to use different multisensory balance strategies that do not align as well with the ABC scale. The advanced analysis provided insights into sensory compensation strategies in USH subtypes.

A link between synaptic plasticity and reorganization of brain activity in Parkinson's disease.

The link between synaptic plasticity and reorganization of brain activity in health and disease remains a scientific challenge. We examined this question in Parkinson's disease (PD) where functional up-regulation of postsynaptic D2 receptors has been documented while its significance at the neural activity level has never been identified. We investigated cortico-subcortical plasticity in PD using the oculomotor system as a model to study reorganization of dopaminergic networks. This model is ideal because this system reorganizes due to frontal-to-parietal shifts in blood oxygen level-dependent (BOLD) activity. We tested the prediction that functional activation plasticity is associated with postsynaptic dopaminergic modifications by combining positron emission tomography/functional magnetic resonance imaging to investigate striatal postsynaptic reorganization of dopamine D2 receptors (using 11C-raclopride) and neural activation in PD. We used covariance (connectivity) statistics at molecular and functional levels to probe striato-cortical reorganization in PD in on/off medication states to show that functional and molecular forms of reorganization are related. D2 binding across regions defined by prosaccades showed increased molecular connectivity between both caudate/putamen and hyperactive parietal eye fields in PD in contrast with frontal eye fields in controls, in line with the shift model. Concerning antisaccades, parietal-striatal connectivity dominated in again in PD, unlike frontal regions. Concerning molecular-BOLD covariance, a striking sign reversal was observed: PD patients showed negative frontal-putamen functional-molecular associations, consistent with the reorganization shift, in contrast with the positive correlations observed in controls. Follow-up analysis in off-medication PD patients confirmed the negative BOLD-molecular correlation. These results provide a link among BOLD responses, striato-cortical synaptic reorganization, and neural plasticity in PD.

Posterior semicircular canal cupulolithiasis during acute pontomedullary demyelination.

Positional vertigo poses a diagnostic challenge in people with multiple sclerosis (MS). The characteristics of positional nystagmus and its response to repositioning manoeuvres are usually sufficient to diagnose benign paroxysmal positional vertigo (BPPV). However, certain BPPV variants respond poorly to repositioning manoeuvres and their nystagmus pattern can resemble that of central positional vertigo caused by infratentorial demyelination. This diagnostic difficulty is particularly challenging if positional vertigo occurs during an MS relapse. We describe a woman with MS who developed a sixth nerve palsy and gaze-evoked nystagmus, caused by demyelination near or within areas classically involved in central positional vertigo. However, she also had positional vertigo from coincident BPPV (and not central positional vertigo). This was initially a treatment resistant-posterior semicircular canal cupulolithiasis but it later progressed to a posterior semicircular canal canalolithiasis, with symptoms promptly resolving after a repositioning manoeuvre.

Agreement between mechanical and digital skinfold callipers.

Background: Skinfold callipers are often used in clinical practice to estimate subcutaneous adipose tissue thickness. Recently, LipoTool emerged as a potential digital system to measure skinfolds, however comparisons with competing equipment are lacking. Aim: The aim of this study was to test the agreement between two competing skinfold callipers (digital and mechanical). Methods: The sample included 22 healthy male adult participants. A certified observer measured eight skinfolds twice using different skinfold callipers (digital and mechanical). Differences between equipment were tested using Wilcoxon signed rank test The distribution of error was examined using the normality test Results: Differences between skinfold callipers were significantly in five skinfolds: triceps (Z = -3.546; P < 0.001), subscapular (Z = -3.984; P < 0.001), suprailiac (Z = 3.024; P = 0.002), supraspinale (Z = 3.885; P < 0.001), abdominal (Z z = -2.937; P = 0.003), thigh (Z = -2.224; P = 0.026) and calf (Z = -2.052; P = 0.040). Differences between callipers were constant. Conclusions: Mechanical and digital callipers tended to record different values of skinfold thickness. Clinical examination should consider equipment-related variation in fat mass estimation.

Pharmacotherapy of cerebellar and vestibular disorders.

PURPOSE OF REVIEW: Major therapeutic advances have been made in patients with episodic and progressive cerebellar ataxias, downbeat nystagmus and some vestibular disorders. We provide an update review on this subject highlighting important research findings from the last two years. RECENT FINDINGS: Recently, the use of omaveloxolone for 2 years significantly improved upright stability in Friedreich's ataxia patients. In an open-label study, N-acetyl-l-leucine administered for 6-weeks significantly improved clinical impression of change, ataxia, and quality of life in patients with Niemann-Pick disease type C1. A 12-week treatment with dalfampridine was associated with improved standing balance in a subgroup of patients with multiple sclerosis. A gluten-free diet alone improved ataxia in half of patients with antiglutamic acid decarboxylase (GAD) ataxia, suggesting that gluten sensitivity might be part of the underlying pathogenesis in anti-GAD ataxia. In a head-to-head trial, both prolonged-release 4-aminopyridine (4-AP) and acetazolamide effectively reduced the attacks up to 60% in patients with episodic ataxia type 2 (EA2), albeit 4-AP had fewer adverse effects. Small observational studies have shown that patients with episodic vestibular syndrome who cannot be diagnosed as definite or probable vestibular migraine, might still improve vestibular symptoms following preventive treatment for migraine. The use of vitamin D supplementation in benign paroxysmal positional vertigo, steroids in acute unilateral vestibulopathy, and betahistine in Ménière's disease patients remains controversial. SUMMARY: Although the use of several therapies is being established in the treatment of cerebellar and vestibular disorders, there is an urgent need for prospective controlled therapeutic trials.

Cognitive impairment and markers of optical neurodegeneration in early multiple sclerosis.

INTRODUCTION: Cognitive impairment and retinal atrophy have been proposed as two potential markers of neurodegeneration in multiple sclerosis (MS). We aimed at assessing the relation between peripapillary retinal nerve fiber layer (pRNFL) and macular ganglion cell layer (mGCL) atrophy and cognitive performance in early MS. METHODS: This is a multicenter cross-sectional study on patients with early MS (clinically isolated syndrome and relapsing-remitting MS), with an EDSS score ≤ 3.0. Patients with previous optic neuritis, other ocular diseases, psychiatric illness, or recent relapse were excluded. All patients underwent standardized optical coherence tomography (OCT) and neuropsychological evaluation with validated tests for MS patients. Cognitive impairment was defined as having two cognitive tasks below age- and education-adjusted norms. RESULTS: We recruited 52 patients with early MS, with an average age of 37 years (SD = 10.5), an average disease duration of 3.69 years (SD = 2.3), and a median EDSS of 1.0 (IQR = 0.5). In this sample, 15/52 patients presented cognitive impairment. Regarding OCT measurements, 7/52 patients had an average pRNFL below the 5th percentile and 2/52 had an average mGCL below the 5th percentile. The average pRNFL thickness was comparable in cognitively impaired and cognitively preserved patients (100.3 µm vs 103.1 µm, p = 0.52); the average mGCL thickness had also similar values between groups (50.5 µm vs 53 µm, p = 0.38). CONCLUSIONS: Cognitive impairment was frequent in our sample of early MS. However, no association with reduced pRNFL or mGCL thickness was found. When compared to OCT, cognitive assessment could provide an earlier marker of neurodegeneration in MS.

Static and Dynamic Ocular Motor Abnormalities as Potential Biomarkers in Spinocerebellar Ataxia Type 3.

While dynamic ocular motor abnormalities (e.g., gaze-evoked nystagmus (GEN), low optokinetic nystagmus (OKN), pursuit and vestibulo-ocular reflex (VOR) gains, and dysmetric saccades) have been shown to be potential biomarkers in spinocerebellar ataxia type 3 (SCA3), the value of static abnormalities (e.g., convergent [esodeviation] and divergent strabismus [exodeviation]) is unknown. Moreover, studies on dynamic abnormalities in SCA3 usually do not take into account the existence of potential abduction-adduction asymmetries in patients with degenerative ataxia. Thirty-eight patients with genetically confirmed SCA3 (24 females; mean age ± SD, 49.8± 12.2 years) and 22 healthy controls (12 females, p = 0.589; mean age ± SD, 50.7± 12.5 years, p = 0.651) underwent clinical and video-oculographic assessment. A p value < 0.002 (between- and within-group analyses) and < 0.001 (correlation analysis) was considered significant. Patients showed larger esodeviation at distance (p < 0.001), became more esodeviated in lateral gaze (p < 0.001), and their near exodeviation correlated with scale for the assessment and rating of ataxia (SARA) score (p = 0.004). Pursuit, OKN, and VOR gains were lower in patients, both for their adducting and abducting components (p < 0.001). Saccades showed higher velocities (p < 0.001), abducting saccades showed lower amplitude (p < 0.001), and adducting saccades tended to show greater vertical bias (p = 0.018) in patients. Abducting saccades showed relatively lower velocity (p < 0.001) and lower amplitude (p = 0.015) than abducting saccades within patients. All dynamic ocular motor abnormalities except saccades correlated with SARA score, CAG repeat number, and/or disease duration (p < 0.001). Static and dynamic ocular motor abnormalities are potential biomarkers in SCA3. SCA3 studies using saccades should take into account the existence of potential abduction-adduction asymmetries.

Labyrinthine haemorrhage secondary to cerebral venous thrombosis.

Cerebral venous thrombosis (CVT) can rarely present with acute ipsilateral cochlear and/or vestibular loss, to date always in the absence of a clear local otogenic process evidenced by magnetic resonance imaging (MRI). This association has been putatively attributed to inner ear anoxia due to blockage of inner ear venous drainage. We present a nonreported case of thrombosis of the left transverse and sigmoid sinuses presenting with acute unilateral vestibulopathy in which MRI disclosed concurrent ipsilateral labyrinthine haemorrhage. A 69-year-old female presented with acute vertigo without hearing loss or other accompanying neurological symptoms. Bedside examination revealed spontaneous right-beating nystagmus and an impaired left head impulse response, with an otherwise normal neurological examination. Audiometry and head and ear computed tomography were unremarkable, whereas MRI showed a nonenhancing hyperintensity of the left inner ear consistent with labyrinthine haemorrhage, and additional venography disclosed thrombosis of the left transverse and sigmoid sinuses. Oral anticoagulation was started, and the patient experienced gradual improvement of symptoms. The current case provides support for the existence of inner ear anoxia in CVT cases presenting with acute ipsilateral vestibular loss, which can ultimately be complicated by secondary bleeding, as seen in our patient. Importantly, presentation in our case closely mimicked that of peripheral vestibular neuritis, and only MRI venography enabled us to make a prompt diagnosis. This raises an important question as to when a diagnosis of vestibular neuritis can be made securely in the absence of MRI assessment with or without venography to completely discard labyrinthine haemorrhage with or without CVT.

The Use of Video-Head Impulse Test in Different Head Positions in Vertical Nystagmus and Ataxia Associated with Probable Thiamine Deficiency.

Upward and downward bias of eye movement signals in the semicircular canals (SCC)- and/or otolith-related central pathways have been proposed to explain the occurrence of vertical nystagmus (downbeat nystagmus [DBN] and upbeat nystagmus [UBN]) and its frequent modulation with head position. Video-head impulse test (VHIT), usually performed in upright position, is a recent development for measuring SCC function. We performed longitudinal nystagmus and VHIT assessments in different head positions in a patient with probable thiamine deficiency, in order to explore a possible relationship between the positional behavior of vertical nystagmus and SCC function. Initially, UBN in upright position changed to DBN in prone position and remained relatively unchanged in supine position. This was associated with both anterior and posterior SCC hyperactive responses in upright position, and a relative enhancement of the anterior SCC responses in prone position and the posterior SCC responses in supine position. Over 1 year, in prone position, change from UBN to DBN and the enhancement of anterior SCC responses remained, while in supine position, UBN either decreased or changed to DBN, when compared to upright position. This was associated with a relative enhancement of the anterior SCC responses in supine position, albeit inconsistently, and the presence of posterior SCC hypoactive responses in all positions, including prone. While not contradicting a primary otolithic dysfunction in the genesis of UBN change to DBN with head position, we provide evidence for positional modulation of SCC function in thiamine deficiency and a possible relationship with nystagmus positional behavior.

Disabling Central Paroxysmal Positioning Upbeat Nystagmus and Vertigo Associated With the Presence of Anti-Glutamic Acid Decarboxylase Antibodies.

An immune attack by anti-glutamic acid decarboxylase (GAD) antibodies is believed to cause a deficiency in gamma-aminobutyric acid-mediated neurotransmission in the cerebellum. This, in turn, leads to several eye movement disorders, including spontaneous downbeat (DBN) and periodic alternating nystagmus. We describe a 68-year-old diabetic woman with disabling paroxysmal positioning upbeat nystagmus (UBN) exclusively in the supine position, associated with asymptomatic spontaneous DBN, alternating skew deviation and hyperactive vestibulo-ocular reflex responses on head impulse testing, in whom high titers of anti-GAD antibodies were detected. After treatment with intravenous immunoglobulin, a complete resolution of positioning UBN and spontaneous DBN occurred, along with a decrease in anti-GAD antibody titers. Positioning UBN in this case may reflect a transient disinhibition of the central vestibular pathways carrying posterior semicircular canal signals, due to lack of normal inhibitory input from the cerebellar nodulus/uvula. Immunoglobulin restored cerebellar inhibitory output, possibly by improving gamma-aminobutyric acid neurotransmission.

Ocular neuromyotonia.

Ocular neuromyotonia is a rare, albeit treatable, ocular motor disorder, characterised by recurrent brief episodes of diplopia due to tonic extraocular muscle contraction. Ephaptic transmission in a chronically damaged ocular motor nerve is the possible underlying mechanism. It usually improves with carbamazepine. A 53-year-old woman presented with a 4-month history of recurrent episodes of binocular vertical diplopia (up to 40/day), either spontaneously or after sustained downward gaze. Between episodes she had a mild left fourth nerve palsy. Sustained downward gaze consistently triggered downward left eye tonic deviation, lasting around 1 min. MR scan of the brain was normal. She improved on starting carbamazepine but developed a rash that necessitated stopping the drug. Switching to lacosamide controlled her symptoms.

Dynamic modeling of bone metastasis, microenvironment and therapy: Integrating parathyroid hormone (PTH) effect, anti-resorptive and anti-cancer therapy.

Bone is a common site for the development of metastasis, as its microenvironment provides the necessary conditions for the growth and proliferation of cancer cells. Several mathematical models to describe the bone remodeling process and how osteoclasts and osteoblasts coupled action ensures bone homeostasis have been proposed and further extended to include the effect of cancer cells. The model proposed here includes the influence of the parathyroid hormone (PTH) as capable of triggering and regulating the bone remodeling cycle. It also considers the secretion of PTH-related protein (PTHrP) by cancer cells, which stimulates the production of receptor activator of nuclear factor kappa-B ligand (RANKL) by osteoblasts that activates osteoclasts, increasing bone resorption and the subsequent release of growth factors entrapped in the bone matrix, which induce tumor growth, giving rise to a self-perpetuating cycle known as the vicious cycle of bone metastases. The model additionally describes how the presence of metastases contributes to the decoupling between bone resorption and formation. Moreover, the effects of anti-cancer and anti-resorptive treatments, through chemotherapy and the administration of bisphosphonates or denosumab, are also included, along with their corresponding pharmacokinetics (PK) and pharmacodynamics (PD). The simulated models, available at http://sels.tecnico.ulisboa.pt/software/, are able to describe bone remodeling cycles, the growth of bone metastases and how treatment can effectively reduce tumor burden on bone and prevent loss of bone strength.

Visual Cortex Plasticity Following Peripheral Damage To The Visual System: fMRI Evidence.

Over the last two decades, functional magnetic resonance imaging (fMRI) has become a powerful research method to investigate cortical visual plasticity. Abnormal fMRI response patterns have been occasionally detected in the visually deprived cortex of patients with bilateral retinal diseases. Controversy remains whether these observations indicate structural reorganization of the visual cortex or unmasking of previously silent cortico-cortical connections. In optic nerve diseases, there is weak evidence showing that early visual cortex seems to lack reorganization, while higher-order visual areas undergo plastic changes which may contribute to optimise visual function. There is however accumulating imaging evidence demonstrating trans-synaptic degeneration of the visual cortex in patients with disease of the anterior visual pathways. This may preclude the use of restorative treatments in these patients. Here, we review and update the body of fMRI evidence on visual cortical plasticity.