Double-blind crossover study of branched-chain amino acid therapy in patients with spinocerebellar degeneration

Dietary Supplementation With Branched Chain Amino Acids to Improve Sleep in Veterans With Traumatic Brain Injury: A Randomized Double-Blind Placebo-Controlled Pilot and Feasibility Trial

Study Objectives

Traumatic brain injury (TBI) is associated with chronic sleep disturbances and cognitive impairment. Our prior preclinical work demonstrated dietary supplementation with branched chain amino acids (BCAA: leucine, isoleucine, and valine), precursors to de novo glutamate production, restored impairments in glutamate, orexin/hypocretin neurons, sleep, and memory in rodent models of TBI. This pilot study assessed the feasibility and preliminary efficacy of dietary supplementation with BCAA on sleep and cognition in Veterans with TBI.

Methods

Thirty-two Veterans with TBI were prospectively enrolled in a randomized, double-blinded, placebo-controlled trial comparing BCAA (30 g, b.i.d. for 21-days) with one of two placebo arms (microcrystalline cellulose or rice protein, both 30 g, b.i.d. for 21-days). Pre- and post-intervention outcomes included sleep measures (questionnaires, daily sleep/study diaries, and wrist actigraphy), neuropsychological testing, and blood-based biomarkers related to BCAA consumption.

Results

Six subjects withdrew from the study (2/group), leaving 26 remaining subjects who were highly adherent to the protocol (BCAA, 93%; rice protein, 96%; microcrystalline, 95%; actigraphy 87%). BCAA were well-tolerated with few side effects and no adverse events. BCAA significantly improved subjective insomnia symptoms and objective sleep latency and wake after sleep onset on actigraphy.

Conclusion

Dietary supplementation with BCAA is a mechanism-based, promising intervention that shows feasibility, acceptability, and preliminary efficacy to treat insomnia and objective sleep disruption in Veterans with TBI. A larger scale randomized clinical trial is warranted to further evaluate the efficacy, dosing, and duration of BCAA effects on sleep and other related outcome measures in individuals with TBI.

Clinical Trial Registration

[http://clinicaltrials.gov/], identifier [NCT03990909].

Current and Emerging Treatment Modalities for Spinocerebellar Ataxias

INTRODUCTION

Spinocerebellar ataxias (SCA) are a group of rare neurodegenerative diseases that dramatically affect the lives of affected individuals and their families. Despite having a clear understanding of SCA's etiology, there are no current symptomatic or neuroprotective treatments approved by the FDA.

AREAS COVERED

Research efforts have greatly expanded the possibilities for potential treatments, including both pharmacological and non-pharmacological interventions. Great attention is also being given to novel therapeutics based in gene therapy, neurostimulation, and molecular targeting. This review article will address the current advances in the treatment of SCA and what potential interventions are on the horizon.

EXPERT OPINION

SCA is a highly complex and multifaceted disease family with the majority of research emphasizing symptomatic pharmacologic therapies. As pre-clinical trials for SCA and clinical trials for other neurodegenerative conditions illuminate the efficacy of disease modifying therapies such as AAV-mediated gene therapy and ASOs, the potential for addressing SCA at the pre-symptomatic stage is increasingly promising.

Pharmacological and non-pharmacological management of spinocerebellar ataxia: A systematic review

Spinocerebellar ataxias (SCA) comprise a rare, genetic subgroup within the degenerative ataxias and are dominantly inherited, with up to 48 recognized genetic subtypes. While an updated review on the management of degenerative ataxia is published recently, an evidence-based review focussed on the management of SCA is lacking. Here, we reviewed the pharmacological and non-pharmacological management of SCA by conducting a systematic review on Medline Ovid and Scopus. Of 29,284 studies identified, 47 studies (pharmacological: n = 25; non-pharmacological: n = 22) that predominantly involved SCA patients were included. Twenty studies had a high risk of bias based on the Cochrane's Collaboration risk of bias tool. As per the European Federation of Neurological Societies 2004 guideline for therapeutic intervention, the remaining 27 studies were of Class I (n = 4) and Class II (n = 23) evidence. Only two therapies had Level A recommendations for the management of ataxia symptoms: riluzole and immediate in-patient neurorehabilitation. Ten therapies had Level B recommendations for managing ataxia symptoms and require further investigations with better study design. These include high dose valproate acid, branched-chain amino acid, intravenous trehalose; restorative rehabilitation using cycling regimen and videogame; and cerebellar stimulations using transcranial direct current stimulation and transcranial magnetic stimulation. Lithium and coaching on psychological adjustment received Level B recommendation for depressive symptoms and quality of life, respectively. Heterogeneous study designs, different genotypes, and non-standardized clinical measures alongside short duration and small sample sizes may hamper meaningful clinical translation. Therefore, rating of recommendations only serve as points of reference.

Efficient Neuroprotective Rescue of Sacsin-Related Disease Phenotypes in Zebrafish

Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is a multisystem hereditary ataxia associated with mutations in SACS, which encodes sacsin, a protein of still only partially understood function. Although mouse models of ARSACS mimic largely the disease progression seen in humans, their use in the validation of effective therapies has not yet been proposed. Recently, the teleost Danio rerio has attracted increasing attention as a vertebrate model that allows rapid and economical screening, of candidate molecules, and thus combines the advantages of whole-organism phenotypic assays and in vitro high-throughput screening assays. Through CRISPR/Cas9-based mutagenesis, we generated and characterized a zebrafish sacs-null mutant line that replicates the main features of ARSACS. The sacs-null fish showed motor impairment, hindbrain atrophy, mitochondrial dysfunction, and reactive oxygen species accumulation. As proof of principle for using these mutant fish in high-throughput screening studies, we showed that both acetyl-DL-leucine and tauroursodeoxycholic acid improved locomotor and biochemical phenotypes in sacs^−/− larvae treated with these neuroprotective agents, by mediating significant rescue of the molecular functions altered by sacsin loss. Taken together, the evidence here reported shows the zebrafish to be a valuable model organism for the identification of novel molecular mechanisms and for efficient and rapid in vivo optimization and screening of potential therapeutic compounds. These findings may pave the way for new interventions targeting the earliest phases of Purkinje cell degeneration in ARSACS.

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.

Altered Plasma Acylcarnitines and Amino Acids Profile in Spinocerebellar Ataxia Type 7

Spinocerebellar ataxia type 7 (SCA7), a neurodegenerative disease characterized by cerebellar ataxia and retinal degeneration, is caused by an abnormal CAG repeat expansion in the ATXN7 gene coding region. The onset and severity of SCA7 are highly variable between patients, thus identification of sensitive biomarkers that accurately diagnose the disease and monitoring its progression are needed. With the aim of identified SCA7-specific metabolites with clinical relevance, we report for the first time, to the best of our knowledge, a metabolomics profiling of circulating acylcarnitines and amino acids in SCA7 patients. We identified 21 metabolites with altered levels in SCA7 patients and determined two different sets of metabolites with diagnostic power. The first signature of metabolites (Valine, Leucine, and Tyrosine) has the ability to discriminate between SCA7 patients and healthy controls, while the second one (Methionine, 3-hydroxytetradecanoyl-carnitine, and 3-hydroxyoctadecanoyl-carnitine) possess the capability to differentiate between early-onset and adult-onset patients, as shown by the multivariate model and ROC analyses. Furthermore, enrichment analyses of metabolic pathways suggest alterations in mitochondrial function, energy metabolism, and fatty acid beta-oxidation in SCA7 patients. In summary, circulating SCA7-specific metabolites identified in this study could serve as effective predictors of SCA7 progression in the clinics, as they are sampled in accessible biofluid and assessed by a relatively simple biochemical assay.

Comprehensive systematic review summary: Treatment of cerebellar motor dysfunction and ataxia: Report of the Guideline Development, Dissemination, and Implementation Subcommittee of the American Academy of Neurology

OBJECTIVE

To systematically review evidence regarding ataxia treatment.

METHODS

A comprehensive systematic review was performed according to American Academy of Neurology methodology.

CONCLUSIONS

For patients with episodic ataxia type 2, 4-aminopyridine 15 mg/d probably reduces ataxia attack frequency over 3 months (1 Class I study). For patients with ataxia of mixed etiology, riluzole probably improves ataxia signs at 8 weeks (1 Class I study). For patients with Friedreich ataxia or spinocerebellar ataxia (SCA), riluzole probably improves ataxia signs at 12 months (1 Class I study). For patients with SCA type 3, valproic acid 1,200 mg/d possibly improves ataxia at 12 weeks. For patients with spinocerebellar degeneration, thyrotropin-releasing hormone possibly improves some ataxia signs over 10 to 14 days (1 Class II study). For patients with SCA type 3 who are ambulatory, lithium probably does not improve signs of ataxia over 48 weeks (1 Class I study). For patients with Friedreich ataxia, deferiprone possibly worsens ataxia signs over 6 months (1 Class II study). Data are insufficient to support or refute the use of numerous agents. For nonpharmacologic options, in patients with degenerative ataxias, 4-week inpatient rehabilitation probably improves ataxia and function (1 Class I study); transcranial magnetic stimulation possibly improves cerebellar motor signs at 21 days (1 Class II study). For patients with multiple sclerosis-associated ataxia, the addition of pressure splints possibly has no additional benefit compared with neuromuscular rehabilitation alone (1 Class II study). Data are insufficient to support or refute use of stochastic whole-body vibration therapy (1 Class III study).

Scales for the clinical evaluation of cerebellar disorders

Clinical scales represent an important tool not only for the initial grading/scoring of disease and assessment of progression, but also for the quantification of therapeutic effects in clinical trials. There are several scales available for the clinical evaluation of cerebellar symptoms. While some scales have been developed and evaluated for specific cerebellar disorders such as Friedreich ataxia, others reliably capture cerebellar symptoms with no respect to the underlying etiology. Each scale has its strengths and weaknesses. Extensive scales are certainly useful for thorough documentation of specific features of certain phenotypes, but this gain of information is not always essential for the purpose of a study. Therefore, compact and manageable scales like the Scale for the Assessment and Rating of Ataxia (SARA) or Brief Ataxia Rating Scale (BARS) are often preferred compared to more complex scales in observational and therapeutic studies.

Molecular mechanism of Spinocerebellar Ataxia type 6: glutamine repeat disorder, channelopathy and transcriptional dysregulation. The multifaceted aspects of a single mutation

Spinocerebellar Ataxia type 6 (SCA6) is an autosomal dominant neurodegenerative disease characterized by late onset, slowly progressive, mostly pure cerebellar ataxia. It is one of three allelic disorders associated to CACNA1A gene, coding for the Alpha1 A subunit of P/Q type calcium channel Cav2.1 expressed in the brain, particularly in the cerebellum. The other two disorders are Episodic Ataxia type 2 (EA2), and Familial Hemiplegic Migraine type 1 (FHM1). These disorders show distinct phenotypes that often overlap but have different pathogenic mechanisms. EA2 and FHM1 are due to mutations causing, respectively, a loss and a gain of channel function. SCA6, instead, is associated with short expansions of a polyglutamine stretch located in the cytoplasmic C-terminal tail of the protein. This domain has a relevant role in channel regulation, as well as in transcription regulation of other neuronal genes; thus the SCA6 CAG repeat expansion results in complex pathogenic molecular mechanisms reflecting the complex Cav2.1 C-terminus activity. We will provide a short review for an update on the SCA6 molecular mechanism.

Effects of acetyl-DL-leucine in patients with cerebellar ataxia: a case series

No existing medication has yet been shown to convincingly improve cerebellar ataxia. Therefore, the identification of new drugs for its symptomatic treatment is desirable. The objective of this case series was to evaluate the efficacy of treatment of cerebellar ataxia with the amino acid acetyl-DL-leucine (Tanganil). Thirteen patients (eight males, median age 51 years) with degenerative cerebellar ataxia of different etiologies (SCA1/2, ADCA, AOA, SAOA) were treated with acetyl-DL-leucine (5 g/day) without titration for 1 week. Motor function was evaluated by changes in the Scale for the Rating and Assessment of Ataxia (SARA) and in the Spinocerebellar Ataxia Functional Index (SCAFI) during treatment compared to a baseline examination. Quality of life (EuroQol-5D-3L) and side effects were also assessed. Mean total SARA decreased remarkably (p = 0.002) from a baseline of 16.1 ± 7.1 to 12.8 ± 6.8 (mean ± SD) on medication. There were also significant improvements in sub-scores for gait (p = 0.022), speech (p = 0.007), finger-chase (p = 0.042), nose-finger-test (p = 0.035), rapid-alternating-movements (p = 0.002) and heel-to-shin (p = 0.018). Furthermore, patients showed better performance in the SCAFI consisting of the 8-m-walking-time (8 MW, p = 0.003), 9-Hole-Peg-Test of the dominant hand (9HPTD, p = 0.011) and the PATA rate (p = 0.005). Quality of life increased during treatment (p = 0.003). No side effects were reported. In conclusion, acetyl-DL-leucine significantly improved ataxic symptoms without side effects and therefore showed a good risk-benefit profile. These findings need to be confirmed in placebo-controlled trials.

Essential tremor: evolving clinicopathological concepts in an era of intensive post-mortem enquiry

Essential tremor (ET) is one of the most common neurological disorders. In recent years, as a result of systematic post-mortem examinations, our knowledge of the pathophysiology of this disease has grown substantially. Clearly identifiable structural changes (ie, Purkinje cell loss, Lewy bodies) have been observed in the brains of individuals with ET. These changes are not uniform and seem to follow several patterns, localising to the cerebellum itself or to a collection of brainstem neurons that synapse directly with Purkinje cells. Furthermore, these changes are similar to those seen in degenerative diseases. A wealth of clinical, epidemiological, and now post-mortem data indicate that this disease, or perhaps this family of diseases, is likely to be neurodegenerative. The molecular mechanisms that underlie these structural changes in ET are unknown. However, with more controlled, tissue-based studies being done, it is hoped that these mechanisms will be elucidated, thereby laying the foundation for the development of more targeted, effective pharmacotherapeutic interventions.

Reliability and validity of ICARS in focal cerebellar lesions

To evaluate the therapies for cerebellar diseases appropriate neurological assessment methods to measure severity of ataxia are required. Reliability and validity of the semiquantitative International Cooperative Ataxia Rating Scale (ICARS) has recently been examined in patients with degenerative ataxias. We evaluated reliability (internal consistency), criterion-related validity and internal construct validity of ICARS for the first time in patients with focal cerebellar lesions (68 patients with surgical lesions and 68 patients with ischemic lesions). For comparison 45 patients with degenerative cerebellar ataxia were included. We found an excellent Cronbach's alpha as a measurement for internal consistency which was independent from underlying disease. Criterion-related validity was high. Total ICARS score mirrored clearly the immediate postsurgical worsening and the improvement during the first 3 months after focal surgical and ischemic lesions, whereas in chronic state of focal and degenerative cerebellar disorders ICARS score remained nearly unchanged. Principal component analysis in patients with focal lesions revealed five distinct and clinically meaningful factors which corresponded to the four ICARS subscores and reflected the laterality of kinetic functions. In degenerative disorders, however, the items for the subscore "kinetic function" loaded to more than one factor. Total ICARS score seems to be a useful and valid measurement to describe the time course of ataxia in patients with focal and degenerative disorders affecting primarily the cerebellum. Validity of subscores however is good in focal, but not in degenerative disorders.

Reliability and validity of the International Cooperative Ataxia Rating Scale: A study in 156 spinocerebellar ataxia patients

To evaluate the efficacy of treatments in spinocerebellar ataxias (SCAs), appropriate clinical scales are required. This study evaluated metric properties of the International Cooperative Ataxia Rating Scale (ICARS) in 156 SCA patients and 8 controls. ICARS was found to be a reliable scale satisfying accepted criteria for interrater reliability, test-retest reliability, and internal consistency. Although validity testing was limited, we found evidence of validity of ICARS when ataxia disease stages and Barthel index were used as external criteria. On the other hand, our study revealed two major problems associated with the use of ICARS. First, the redundant and overlapping nature of several items gave rise to a considerable number of contradictory ratings. Second, a factorial analysis showed that the rating results were determined by four different factors that did not coincide with the ICARS subscales, thus questioning the justification of ICARS subscore analysis in clinical trials.

International cooperative ataxia rating scale (ICARS): Appropriate for studies of Friedreich's ataxia?

Clinicians require scientifically rigorous, clinically meaningful rating scales to evaluate the health impact of disease and treatment that cannot be measured using conventional laboratory instruments. This study evaluated the psychometric properties of the International Cooperative Ataxia Rating Scale (ICARS), a commonly used clinician-rated measure, in Friedreich's ataxia (FRDA). People with confirmed FRDA were assessed by using the ICARS. Two assumptions of its measurement model were tested: the legitimacy of reporting ICARS scores in FRDA, and the acceptability, reliability, and validity of total and subscale scores. Seventy-seven people with FRDA were assessed. The ICARS total score effectively satisfied all psychometric criteria tested. The posture and gait disturbances subscale also performed well. The other three subscales did not pass standard criteria for tests of scaling assumptions, reliability, and validity. This small study recommends only the use of the ICARS total score as a measure of FRDA. However, the extent to which this score quantifies the true extent of FRDA remains uncertain as our validity testing was limited, partly by the lack of appropriate validating measures. Further validity testing, and examination of responsiveness, is required before the ICARS can be recommended as an outcome measure for treatment trials of FDRA.

Branched-chain amino acids and brain function

Branched-chain amino acids (BCAAs) influence brain function by modifying large, neutral amino acid (LNAA) transport at the blood-brain barrier. Transport is shared by several LNAAs, notably the BCAAs and the aromatic amino acids (ArAAs), and is competitive. Consequently, when plasma BCAA concentrations rise, which can occur in response to food ingestion or BCAA administration, or with the onset of certain metabolic diseases (e.g., uncontrolled diabetes), brain BCAA concentrations rise, and ArAA concentrations decline. Such effects occur acutely and chronically. Such reductions in brain ArAA concentrations have functional consequences: biochemically, they reduce the synthesis and the release of neurotransmitters derived from ArAAs, notably serotonin (from tryptophan) and catecholamines (from tyrosine and phenylalanine). The functional effects of such neurochemical changes include altered hormonal function, blood pressure, and affective state. Although the BCAAs thus have biochemical and functional effects in the brain, few attempts have been made to characterize time-course or dose-response relations for such effects. And, no studies have attempted to identify levels of BCAA intake that might produce adverse effects on the brain. The only "model" of very high BCAA exposure is a very rare genetic disorder, maple syrup urine disease, a feature of which is substantial brain dysfunction but that probably cannot serve as a useful model for excessive BCAA intake by normal individuals. Given the known biochemical and functional effects of the BCAAs, it should be a straightforward exercise to design studies to assess dose-response relations for biochemical and functional effects and, in this context, to explore for adverse effect thresholds.

Update on nutritional supplementation with branched-chain amino acids

PURPOSE OF REVIEW

Branched-chain amino acids (BCAAs) have a peculiar role in whole-body nitrogen metabolism. BCAAs are not only a substrate for protein synthesis, but also modulate several components of the synthetic machinery and help to conserve muscle mass; accordingly, several conditions, characterized by protein loss and catabolic status, are likely to benefit from amino acid administration. In addition, the competitive action of BCAAs on amino acid transport across the blood-brain barrier may ultimately alter the synthesis of brain neurotransmitters, involved in neurological diseases.

RECENT FINDINGS

Both putative actions of BCAAs have been tested in controlled clinical studies in the last few years. The beneficial effects on nutrition were reported to improve muscle performance, reduce protein loss during bed-rest, favor weight loss in obesity, reduce catabolism in trauma patients and improve clinical outcomes in patients with advanced cirrhosis. In this last area, the effects on nutrition might be coupled with the effects on hepatic encephalopathy mediated by improved neurotransmission, successfully tested in mania, tardive dyskinesia and spinocerebellar degeneration.

SUMMARY

After 30 years of investigation with BCAAs, new studies each year provide further evidence supporting their beneficial effect in a variety of diseases. There is a need for long-term, randomized clinical studies, both in the prevention and in the treatment of various pathological conditions.

Eyeblink conditioning in patients with hereditary ataxia: a one-year follow-up study

Delay eyeblink conditioning was examined in patients with genetically-defined heredoataxias and age-matched control subjects. 24 patients with spinocerebellar ataxia type 6 (SCA6), type 3 (SCA3), and Friedreich's ataxia (FRDA) participated. SCA6 affects primarily the cerebellum, whereas extracerebellar involvement is common in SCA3 and FRDA. Testing was performed in three sessions six months apart. Severity of ataxia was defined based on the International Ataxia Cooperative Rating Scale (ICARS). As expected, cerebellar patients were significantly impaired in eyeblink conditioning compared to controls. Signs of retention and further learning across sessions were present in controls, but not in the cerebellar patients. In addition, findings of disturbed timing of conditioned responses were observed. Both onsets and peaks of the conditioned responses (CRs) occurred significantly earlier in cerebellar patients. Shortened CR responses were most prominent in patients with primarily cerebellar cortical disease (SCA6). In the group of all cerebellar patients, the SCA3 and the FRDA group correlations between learning deficits and clinical findings were weak. Moderate-to-strong correlations were found in the SCA6 patients. There was no significant change, however, in clinical ataxia scores and CR incidence across the three sessions. In summary, impaired learning of conditioned eyeblink responses is a stable finding across multiple sessions in patients with degenerative cerebellar disorders. Eyeblink conditioning may be a useful measure of cerebellar impairment in patients with hereditary ataxias that primarily affect the cerebellum (such as SCA6). In other heredoataxias (such as SCA3 and FRDA), extracerebellar involvement not assessed by ICARS likely contributes to eyeblink conditioning abnormalities.

Symptomatic and Disease-Modifying Therapy for the Progressive Ataxias

BACKGROUND

The progressive ataxias are a diverse group of neurologic diseases that share features of degeneration of the cerebellum and its inflow/outflow pathways but differ in etiology, course, and associated noncerebellar system involvement. Some will have treatable causes, but for most, the pathophysiology is incompletely known.

REVIEW SUMMARY

Treatment strategies will include (1) definitive therapy when available, (2) symptomatic treatment and prevention of complications, and (3) rehabilitation and support resources. The physician will have to decide whether to introduce or approve the use of therapies based on as yet-unproven mechanisms or the use of complementary medicine approaches.

CONCLUSIONS

There are as yet no drugs that have been approved by the Food and Drug Administration for the treatment of the progressive ataxias and relatively few disease-modifying therapies, but symptomatic and rehabilitation interventions can greatly improve the quality of life of individuals with these disabling neurodegenerative disorders.

Dominant spinocerebellar ataxias: a molecular approach to classification, diagnosis, pathogenesis and the future

The capacity to use molecular techniques to establish the genetic diagnoses of the autosomal dominant ataxias has revolutionized the field. It is now possible to systematically classify these disorders according to the nature of the causative mutation, with implications for diagnostic testing, analysis of pathogenesis and therapeutic strategies. Here, the disorders are grouped into ataxias caused by CAG repeat expansions that encode polyglutamine, ataxias caused by mutations in ion channels, ataxias caused by repeat expansions that do not encode polyglutamine, and ataxias caused by point mutations. The clinical, pathological, genetic and pathogenic features of each disorder are considered and the current status and future of diagnosis and therapy are reviewed in light of this classification scheme.

Inter-rater reliability of the International Cooperative Ataxia Rating Scale (ICARS)

We assessed the inter-rater reliability of the 100-point International Cooperative Ataxia Rating Scale (ICARS). Three neurologists independently rated videotaped ICARS examinations of 22 subjects with genetically determined ataxias (spinocerebellar ataxia [SCA] Type 1 in 11; SCA Type 2 in 1; Friedreich's ataxia in 10) and 4 controls. Scores on live ICARS assessment had ranged from 0 to 7 for controls and 11 to 74 for ataxic subjects (clinically very mildly affected to wheelchair-bound). Inter-rater correlation was very high for the total score (Kendall's omega 0.994, 95% confidence interval, 0.988-0.997), and high to very high for each component subscore (0.791 for speech to 0.994 for posture/gait). All correlations were significant at P < 0.00001. The ICARS exhibits very high inter-rater reliability even without prior observer standardisation and is sensitive to a range of ataxia severities from very mild to severe.

The spinocerebellar ataxias: order emerges from chaos

In the past decade, the genetic etiologies accounting for most cases of adult-onset dominant cerebellar ataxia have been discovered. This group of disorders, generally referred to as the spinocerebellar ataxias (SCAs), can now be classified by a simple genetic nosology, essentially a sequential list in which each new SCA is given a number. However, recent advances in the elucidation of SCA pathogenesis provide the opportunity to subclassify the disorders into three discrete groups based on pathogenesis: 1) the polyglutamine disorders, SCAs 1, 2, 3, 7, and 17, which result from proteins with toxic stretches of polyglutamine; 2) the channelopathies, SCA6 and episodic ataxia types 1 and 2 (EA1 and EA2), which result from disruption of calcium or potassium channel function; and 3) the gene expression disorders, SCAs 8, 10, and 12, which result from repeat expansions outside of coding regions that may quantitatively alter gene expression. SCAs 4, 5, 9, 11, 13-16, 19, 21, and 22 are of unknown etiology, and may or may not fit into one of these three groups. At present, most diagnostic and therapeutic strategies apply equally to all of the SCAs. Therapy specific for individual diseases or types of diseases is a realistic goal in the foreseeable future.