Update on the Pharmacotherapy of Cerebellar Ataxia and Nystagmus

GAA-FGF14 ataxia (SCA27B): phenotypic profile, natural history progression and 4-aminopyridine treatment response

Ataxia due to an autosomal dominant intronic GAA repeat expansion in FGF14 [GAA-FGF14 ataxia, spinocerebellar ataxia 27B (SCA27B)] has recently been identified as one of the most common genetic late-onset ataxias. We here aimed to characterize its phenotypic profile, natural history progression, and 4-aminopyridine (4-AP) treatment response. We conducted a multi-modal cohort study of 50 GAA-FGF14 patients, comprising in-depth phenotyping, cross-sectional and longitudinal progression data (up to 7 years), MRI findings, serum neurofilament light (sNfL) levels, neuropathology, and 4-AP treatment response data, including a series of n-of-1 treatment studies. GAA-FGF14 ataxia consistently presented as late-onset [60.0 years (53.5-68.5), median (interquartile range)] pancerebellar syndrome, partly combined with afferent sensory deficits (55%) and dysautonomia (28%). Dysautonomia increased with duration while cognitive impairment remained infrequent, even in advanced stages. Cross-sectional and longitudinal assessments consistently indicated mild progression of ataxia [0.29 Scale for the Assessment and Rating of Ataxia (SARA) points/year], not exceeding a moderate disease severity even in advanced stages (maximum SARA score: 18 points). Functional impairment increased relatively slowly (unilateral mobility aids after 8 years in 50% of patients). Corresponding to slow progression and low extra-cerebellar involvement, sNfL was not increased relative to controls. Concurrent second diseases (including progressive supranuclear palsy neuropathology) represented major individual aggravators of disease severity, constituting important caveats for planning future GAA-FGF14 trials. A treatment response to 4-AP with relevance for everyday living was reported by 86% of treated patients. A series of three prospective n-of-1 treatment experiences with on/off design showed marked reduction in daily symptomatic time and symptom severity on 4-AP. Our study characterizes the phenotypic profile, natural history progression, and 4-AP treatment response of GAA-FGF14 ataxia. It paves the way towards large-scale natural history studies and 4-AP treatment trials in this newly discovered, possibly most frequent, and treatable late-onset ataxia.

Targeting Ion Channels and Purkinje Neuron Intrinsic Membrane Excitability as a Therapeutic Strategy for Cerebellar Ataxia

In degenerative neurological disorders such as Parkinson's disease, a convergence of widely varying insults results in a loss of dopaminergic neurons and, thus, the motor symptoms of the disease. Dopamine replacement therapy with agents such as levodopa is a mainstay of therapy. Cerebellar ataxias, a heterogeneous group of currently untreatable conditions, have not been identified to have a shared physiology that is a target of therapy. In this review, we propose that perturbations in cerebellar Purkinje neuron intrinsic membrane excitability, a result of ion channel dysregulation, is a common pathophysiologic mechanism that drives motor impairment and vulnerability to degeneration in cerebellar ataxias of widely differing genetic etiologies. We further propose that treatments aimed at restoring Purkinje neuron intrinsic membrane excitability have the potential to be a shared therapy in cerebellar ataxia akin to levodopa for Parkinson's disease.

A dynamical method to objectively assess infantile nystagmus based on eye tracking. A pilot study

PURPOSE

The purpose of this research is to propose a new method for the easy, inexpensive and objective quantification of nystagmus using eye-tracking records collected during a simple reading task that could be implantable in clinical practice to assess patients with nystagmus.

METHODS

This is a prospective, observational pilot study. Eye movements of 4 nystagmus patients and 9 healthy children during a reading task (a paragraph with 82 words) on a 15'' monitor were collected and compared. Data are time series indicating the gaze position on the screen. Two quantifiers were proposed: IndS (based on the speed of movements) and IndF (based on the variation of the gaze trajectory).

RESULTS

The indices proposed reflect differences in the behavior of eye movements between the two groups. Nystagmus patients present higher values of IndS - indicating smaller number of slow movements (16% of movements with speeds <0.33 1/s for nystagmus and 85% for the control group, with p = 0.01) - and higher values of IndF - indicating higher gaze fluctuation (p = 0.01). Differences were not related with reading speed as show the mean and standard deviation: the nystagmus group required 115±45 s to complete the task and the control group 151±85 s; p = 0.73.

CONCLUSIONS

The proposed indices provide a new method that allows an objective assessment of nystagmus, with potential use in clinical and research practice to improve the follow-up of patients by monitoring the nystagmus over time or treatment.

Chlorzoxazone Alleviates Experimental Autoimmune Encephalomyelitis via Inhibiting IL-6 Secretion of Dendritic Cells

Multiple sclerosis (MS) is a chronic inflammatory demyelinating autoimmune disease with chronic inflammatory demyelination of the CNS. Experimental autoimmune encephalomyelitis (EAE) is an important animal model to study MS, with many pathological phenomena similar to MS. Th17 cells are important regulators of EAE and MS pathogenesis. Most cytokines needed for Th cell development are secreted by APCs, such as dendritic cells (DCs). Consequently, MS could be improved by inhibiting cytokine secretion from DCs. In this study, we reported that chlorzoxazone could ameliorate EAE pathogenesis via inhibiting IL-6 production by DCs. The EAE signs in the chlorzoxazone-treated group of mice were relieved, which was mainly manifested as lower clinical scores, a decrease in the number of immune cells, and a reduction of demyelination in the CNS. Moreover, the proportion of Th17 cells in the spleen and CNS decreased significantly. In vitro experiments showed that chlorzoxazone treatment significantly reduced DC-derived IL-6 production. In the DC-T cell coculture experiment, significantly decreased Th17 differentiation was observed after chlorzoxazone treatment. In addition, mass spectrometric analysis was performed to elucidate the mechanism by which chlorzoxazone affected EAE and DC function. We showed that the effect of chlorzoxazone on inhibiting the secretion of IL-6 by DCs may be mediated via the AMP-activated protein kinase pathway. Overall, our study elucidated the key role of chlorzoxazone in regulating EAE pathogenesis and suggested that it might be used as a new drug for MS patients.

Use of Dalfampridine in a Young Child with Episodic Ataxia Type 2

Episodic ataxia type 2 (EA2) is a rare autosomal dominant disorder associated with mutations of the CACNA1A gene. 1 Because there is no curative therapy available, EA2 is typically managed symptomatically. First line treatment has typically been with acetazolamide. 2 Dalfampridine has also been noted to decrease the frequency and duration of ataxic attacks in patients ranging in age from adolescence through adulthood. 3 , 4 The efficacy and dosing of dalfampridine has not yet been studied in younger pediatric populations. The lack of published experience in younger children can and has led to these patients going without potentially safe and effective treatment. Thus, we describe an 8-year-old girl with EA2 and a confirmed CACNA1A gene mutation whose symptoms had been previously unrelieved by acetazolamide. She was subsequently trialed on dalfampridine and experienced symptomatic relief at a dose of 0.3 mg/kg.

Downbeat nystagmus: a clinical review of diagnosis and management

PURPOSE OF REVIEW

This review will extensively cover the clinical manifestations, causes, diagnostic evaluation, and management strategies of downbeat nystagmus (DBN).

RECENT FINDINGS

Historically, MRI to assess for structural lesions at the cervicomedullary junction has been the primary diagnostic test in the evaluation of DBN since the 1980s. In recent years, there is increasing awareness of nonstructural causes of DBN including gluten ataxia, nutritional deficiencies, and paraneoplastic syndromes, among others. Medical management with aminopyridines has become first-line therapy in addition to disease-specific therapies.

SUMMARY

DBN is a common form of acquired nystagmus and the differential diagnosis remains broad, including both benign and potentially fatal causes. For practical purposes, the causes can be categorized as structural vs. nonstructural with MRI as the ideal, initial diagnostic study to differentiate the two. General therapeutic options include pharmacotherapy to enhance Purkinje cell function, strabismus surgery or prisms to shift null points, and behavioural changes. Disease-specific treatment is necessarily broad, though a significant proportion of patients will be idiopathic.

[Options for the symptomatic treatment of chronic neurological gait disorders]

Gait and mobility impairments are common and relevant in patients with chronic neurological disorders. It reduces the health-related quality of life and induces falls with morbidity. Symptomatic treatment options are therefore necessary in order to improve the health status of patients with neurological disorders.By means of a selective literature research focusing on studies with specific gait-related outcome measures. We discuss the differential treatment options for (1) hypokinetic gait disorders (Parkinson´s disease, Normal pressure hydrocephalus, vascular encephalopathy), (2) gait unsteadiness with ataxia (sensory and cerebellar ataxia), and (3) gait with spasticity and paresis (due to multiple sclerosis). Therapeutical options for the symptomatic treatment of gait disorders comprise non-pharmacological and pharmacological approaches. Both address the functional domains of "locomotion", "postural control", "modulation" and "adaptability" of gait.Pharmacological options are orientated to pathophysiology of the underlying diseases. Supportive physiotherapeutic interventions offer broader and unspecific options for treatment. Clinical conditions that specifically disturb the execution of locomotion or gait can also be addressed by the provision of physical therapy or supportive devices.Effective options for the symptomatic treatment of patients with neurological gait disorders are available. Applications of options addressing the pathophysiology of the underlying disease, a functional domain-based exercise and physiotherapy program, and the provision of walking aides for specific symptoms that further worsen gait performance can be recommended.

Placebo response in degenerative cerebellar ataxias: a descriptive review of randomized, placebo-controlled trials

Placebo response in degenerative cerebellar ataxias (CAs) has never been studied despite the large number of randomized controlled trials (RCTs) that have been conducted. In this descriptive review, we aimed to examine the placebo response in patients with CAs. We performed a literature search on PubMed for RCTs on CAs that were published from 1977 to January 2020 and collected data on the changes from the baseline to the endpoint on various objective ataxia-associated clinical rating scales. We reviewed 56 clinical trials, finally including 35 parallel-group studies and excluding 21 cross-over studies. The included studies were categorized as follows: (1) studies showing significant improvements in one or more ataxia scales in the placebo groups (n = 3); (2) studies reporting individual placebo responders with improvements in one or more ataxia scales in the placebo groups (n = 5)-the overall proportion of placebo responders was 31.9%; (3) studies showing mean changes in the direction of improvement in at least one ataxia scale in the placebo groups, though not statistically significant (n = 19); (4) studies showing no placebo response in any of the ataxia scales in the placebo groups (n = 4); (5) studies where data on the placebo groups were unavailable (n = 9). This review demonstrated the placebo response in patients with CAs on various objective ataxia scales. Our study emphasizes that the placebo response should be considered when designing, analyzing, and interpreting clinical trials and in clinical practice in CA patients.

Noninvasive Cerebellar Stimulation as a Complement Tool to Pharmacotherapy

BACKGROUND

Cerebellar ataxias represent a wide and heterogeneous group of diseases characterized by balance and coordination disturbance, dysarthria, dyssynergia and adyadococinesia, caused by a dysfunction in the cerebellum. In recent years there has been growing interest in discovering therapeutical strategy for specific forms of cerebellar ataxia. Together with pharmacological studies, there has been growing interest in non-invasive cerebellar stimulation techniques to improve ataxia and limb coordination. Both transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) are non-invasive techniques to modulate cerebro and cerebellar cortex excitability using magnetic or electric fields.

METHODS

Here we aim to review the most relevant studies regarding the application of TMS and tDCS for the treatment of cerebellar ataxia.

CONCLUSION

As pharmacological strategies were shown to be effective in specific forms of cerebellar ataxia and are not devoid of collateral effects, non-invasive stimulation may represent a promising strategy to improve residual cerebellar circuits functioning and a complement tool to pharmacotherapy.

Efficacy of acetylleucine in vertigo and dizziness: a systematic review of randomised controlled trials

PURPOSE

To assess the efficacy of acetylleucine to improve or stop an attack of vertigo and dizziness (vertigo/dizziness).

METHODS

Systematic review by 2 independent reviewers. Consultation of the Medline, Cochrane and ClinicalTrials.gov databases until September 2018. Keywords used: Acetylleucine, Tanganil®, Acetyl-DL-leucine, Acetyl-leucine. Trial selection: randomised controlled trials (RCTs) comparing acetylleucine against placebo.

RESULTS

Up until 2018, no RCTs have been published on the efficacy of acetylleucine in vertigo/dizziness.

CONCLUSION

There is no solid evidence of the efficacy of acetylleucine in vertigo/dizziness. Given its frequent prescription and the cost generated for the French social security system, high-quality randomised trials should be carried out to assess its efficacy.

Clinical and electrophysiological results of eye muscle surgery in 17 patients with downbeat nystagmus

Purpose

To test the hypothesis that eye muscle surgery in treatment of patients with acquired downbeat nystagmus results in improvement measures of visual and ocular motor function.

Methods

This is a prospective, interventional case series analysis of clinical and electrophyisological data before and after eye muscle surgery in 17 patients with acquired downbeat nystagmus who did not respond to medical treatments. Outcome measures included: 1) routine demography and clinical characteristics, 2) subjective oscillopsia (SO), 3) binocular best-corrected visual acuity in the null position (BVA), 3) primary position strabismic deviation (SD), 5) anomalous head posture (AHP), 6) contrast sensitivity function (CS), and 7) nystagmus slow phase velocity (SPV). All patients were followed at least 12 months. Parametric and non-parametric statistical analysis of outcome measure data above pre- and post-treatment were perfomed using standard software on grouped data using computerized software.

Results

Patients' age ranged from 5 to 85 years (average 27 years). About 59% were male. Follow up ranged from 1-10 years (average 2.0 years). Around 70% had an associated central nervous systemic diagnosis, 100% had an AHP, oscillopsia and decreased CS, 53% had other eye disease, and 59% had strabismus. There were no complications from surgery. There were signficant post-treatment improvements in mean/median group BVA, SO, SD, AHP, CS, and SPV.

Conclusion

This study supports the hypothesis that eye muscle surgery as treatments for patients with acquired downbeat nystagmus can result in improvements in multiple aspects of ocular motor and visual functions.

Oculomotor Disturbances in Patients with Chronic Nonspecific Spinal Pain

Objective

There is increasing evidence that the cerebellum has a role in pain processing. The present study investigates whether chronic pain patients, who are likely to have altered pain processing, exhibit signs of subtle cerebellar dysfunction. We used oculomotor tasks to assess dysfunction of the associated neuronal networks, including the cerebellum.

Methods

Thirty patients with chronic nonspecific spinal pain and 30 age- and sex-matched controls were enrolled. Using a head-mounted eye tracker (EyeSeeCam), eye movements were quantified during predictable and unpredictable saccade and smooth pursuit tasks in the horizontal plane.

Results

The initial latency and the velocity variability of smooth pursuit were significantly increased in the chronic spinal pain patients compared with controls (initial latency: 198 ± 20 vs 185 ± 11 ms, P < 0.01; slow phase velocity standard deviation: 3.31 ± 1.02 vs 2.70 ± 0.83°/s, P < 0.05). Moreover, the latency of predictable saccades was prolonged in patients (rightward: 161 ± 20 vs 152 ± 12 ms, P < 0.05; leftward: 164 ± 22 vs 153 ± 18 ms, P = 0.05).

Conclusions

Our results show that chronic spinal pain patients display subtle but significant oculomotor changes as compared with healthy controls. Considering the networks involved in the generation of saccades and smooth pursuit, the results would be consistent with a dysfunction of cerebellar regions, especially parts of the cerebellar hemispheres. Alternatively, they could also point toward a dysfunction in the frontal eye field and/or pontine oculomotor nuclei.

Eye Movement Abnormalities in Multiple Sclerosis: Pathogenesis, Modeling, and Treatment

Multiple sclerosis (MS) commonly causes eye movement abnormalities that may have a significant impact on patients’ disability. Inflammatory demyelinating lesions, especially occurring in the posterior fossa, result in a wide range of disorders, spanning from acquired pendular nystagmus (APN) to internuclear ophthalmoplegia (INO), among the most common. As the control of eye movements is well understood in terms of anatomical substrate and underlying physiological network, studying ocular motor abnormalities in MS provides a unique opportunity to gain insights into mechanisms of disease. Quantitative measurement and modeling of eye movement disorders, such as INO, may lead to a better understanding of common symptoms encountered in MS, such as Uhthoff’s phenomenon and fatigue. In turn, the pathophysiology of a range of eye movement abnormalities, such as APN, has been clarified based on correlation of experimental model with lesion localization by neuroimaging in MS. Eye movement disorders have the potential of being utilized as structural and functional biomarkers of early cognitive deficit, and possibly help in assessing disease status and progression, and to serve as platform and functional outcome to test novel therapeutic agents for MS. Knowledge of neuropharmacology applied to eye movement dysfunction has guided testing and use of a number of pharmacological agents to treat some eye movement disorders found in MS, such as APN and other forms of central nystagmus.

Cerebellar ataxia

The cerebellum plays an integral role in the control of limb and ocular movements, balance, and walking. Cerebellar disorders may be classified as sporadic or hereditary with clinical presentation varying with the extent and site of cerebellar damage and extracerebellar signs. Deficits in balance and walking reflect the cerebellum's proposed role in coordination, sensory integration, coordinate transformation, motor learning, and adaptation. Cerebellar dysfunction results in increased postural sway, hypermetric postural responses to perturbations and optokinetic stimuli, and postural responses that are poorly coordinated with volitional movement. Gait variability is characteristic and may arise from a combination of balance impairments, interlimb incoordination, and incoordination between postural activity and leg movement. Intrinsic problems with balance lead to a high prevalence of injurious falls. Evidence for pharmacologic management is limited, although aminopyridines reduce attacks in episodic ataxias and may have a role in improving gait ataxia in other conditions. Intensive exercises targeting balance and coordination lead to improvements in balance and walking but require ongoing training to maintain/maximize any effects. Noninvasive brain stimulation of the cerebellum may become a useful adjunct to therapy in the future. Walking aids, orthoses, specialized footwear and seating may be required for more severe cases of cerebellar ataxia.

Gait ataxia in humans: vestibular and cerebellar control of dynamic stability

During human locomotion, vestibular feedback control is fundamental for maintaining dynamic stability and adapting the gait pattern to external circumstances. Within the supraspinal locomotor network, the cerebellum represents the key site for the integration of vestibular feedback information. The cerebellum is further important for the fine-tuning and coordination of limb movements during walking. The aim of this review article is to highlight the shared structural and functional sensorimotor principles in vestibular and cerebellar locomotion control. Vestibular feedback for the maintenance of dynamic stability is integrated into the locomotor pattern via midline, caudal cerebellar structures (vermis, flocculonodular lobe). Hemispheric regions of the cerebellum facilitate feed-forward control of multi-joint coordination and higher locomotor functions. Characteristic features of the gait disorder in patients with vestibular deficits or cerebellar ataxia are increased levels of spatiotemporal gait variability in the fore-aft and the medio-lateral gait dimension. In the fore-aft dimension, pathologic increases of gait fluctuations critically depend on the locomotion speed and predominantly manifest during slow walking velocities. This feature is associated with an increased risk of falls in both patients with vestibular hypofunction as well as patients with cerebellar ataxia. Pharmacological approaches for the treatment of vestibular or cerebellar gait ataxia are currently not available. However, new promising options are currently tested in randomized, controlled trials (fampridine/FACEG; acetyl-DL-leucine/ALCAT).

Symptomatic treatment in multiple sclerosis-interim analysis of a nationwide registry

OBJECTIVE

To analyze symptomatic treatment in patients with multiple sclerosis (MS).

BACKGROUND

Multiple sclerosis is a chronic inflammatory disease of the central nervous system, with accumulating disability symptoms like spasticity, voiding disorders, depression, and pain might occur.

MATERIAL AND METHODS

The nationwide German MS registry was initiated 2001 under guidance of the German MS society (Deutsche MS Gesellschaft). This study was performed as an interim analysis to lay foundation for future work on this topic. A subcohort of 5113 patients was assessed for this interim analysis. The mean age of the patients was 45.3 years; mean EDSS was 4.2. More than two-third of the enrolled patients were females (70.9%).

RESULTS

Most frequent symptoms were fatigue (60%), followed by spasticity (52.5%) and voiding disorders (51.7%). The likelihood of treatment was highest for epileptic disorders (68.8%), spasticity (68.5%), pain (60.7%), and depression (58.9%). Multivariate regression analysis showed that retirement was the strongest factor predictive for antispastic treatment (β=.061, P=.005).

CONCLUSION

Almost all patients in this analysis suffer from symptoms due to advanced MS. Treatment for the various symptoms differed tremendously. The likelihood of treatment correlated with the availability of effective therapeutic agents. Clinicians should put more awareness on MS symptoms. Symptomatic treatment may improve quality of life.

Aminopyridines for the treatment of neurologic disorders

PURPOSE OF REVIEW

To identify the different indications for the treatment of neurologic disorders with the potassium channel blockers 4-aminopyridine (4-AP) and 3,4-diaminopyridine (3,4-DAP).

RECENT FINDINGS

4-AP is an effective symptomatic treatment for downbeat nystagmus (DBN), episodic ataxia type 2 (EA2) (5-10 mg TID), and impaired gait in multiple sclerosis (MS) (10 mg BID). 3,4-DAP (5 mg/d-20 mg TID) improves symptoms in Lambert-Eaton myasthenic syndrome (LEMS) (randomized placebo-controlled trials for all 4 entities). 4-AP may also be effective in cerebellar gait ataxia of different etiologies (2 case series), upbeat nystagmus, and limb ataxia in MS (single cases). In the recommended dosages, they are well tolerated. The assumed mode of action is a blockade of mainly Kv_1.5: in DBN, this increases the excitability of Purkinje cells (PC), and in EA2, restores the precision of resting discharge of PC. In MS, 4-AP improves the conduction of action potentials in demyelinated axons, and in LEMS, 3,4-DAP facilitates the transmission at the neuromuscular endplate by prolonging the action potential duration.

SUMMARY

There is sufficient evidence that APs are indicated for the symptomatic treatment of DBN, EA2, gait ataxia due to MS and cerebellar disorders, and LEMS with a reasonable risk-benefit profile.

Cerebellum: from Fundamentals to Translational Approaches. The Seventh International Symposium of the Society for Research on the Cerebellum

In terms of cerebellar research and ataxiology, a most fascinating period is currently going on. Numerous academic groups are now focusing their innovative research on the so-called little brain, hidden at the bottom of our brain. Indeed, its unique anatomical features make the cerebellum a wonderful window to address major questions about the central nervous system. The seventh international symposium of the SRC was held in Brussels at the Palace of Academies from May 8 to 10, 2015. The main goal of this dense symposium was to gather in a 2-day meeting senior researchers of exceptional scientific quality and talented junior scientists from all over the world working in the multidisciplinary field of cerebellar research. Fundamental and clinical researchers shared the latest knowledge and developments in this rapidly growing field. New ideas, addressed in a variety of inspiring talks, provoked a vivid debate. Advances in genetics, development, electrophysiology, neuroimaging, neurocognition and affect, as well as in the cerebellar ataxias and the controversies on the roles and functions of the cerebellum were presented. The Ferdinando Rossi lecture and the key-note lecture were delivered by Jan Voogd and Chris De Zeeuw, respectively. Contacts between researchers of different neuroscientific disciplines established a robust basis for novel trends and promising new cooperations between researchers and their centers spread all over the world.