David J. Szmulewicz

Annals of neurology • July 22, 2024

Sarah Milne, Melissa Roberts, Shannon Williams, Jillian Chua, Alison Grootendorst, Genevieve Agostinelli, Anneke Grobler, Hannah Ross, Amy Robinson, Kristen Grove, Gabrielle Modderman, Annabel Price, Megan Thomson, Libby Massey, Christina Liang, Kishore Kumar, Kim Dalziel, Joshua Burns, Carolyn Sue, Pubudu Pathirana, Malcolm Horne, Nikki Gelfand, Helen Curd, David Szmulewicz, Louise Corben, Martin Delatycki

Objective: Rehabilitation is thought to reduce ataxia severity in individuals with hereditary cerebellar ataxia (HCA). This multicenter, randomized controlled superiority trial aimed to examine the efficacy of a 30-week goal-directed rehabilitation program compared with 30 weeks of standard care on function, ataxia, health-related quality of life, and balance in individuals with an HCA. Methods: Individuals with an autosomal dominant or recessive ataxia (aged ≥15 years) were enrolled at 5 sites in Australia. Participants were randomized (1:1) to receive rehabilitation (6 weeks of outpatient physiotherapy followed by a 24-week home exercise program) (n = 39) or continued their usual activity (n = 37). The primary outcome measure was the motor domain of the Functional Independence Measure (mFIM) at 7 weeks. Secondary outcomes included the Scale for the Assessment and Rating of Ataxia (SARA) and the SF-36v2, assessed at 7, 18, and 30 weeks. Outcome assessors were blinded to treatment allocation. Results: Seventy-one participants (rehabilitation, 37; standard-care, 34) were included in the intention-to-treat analysis. At 7 weeks, mFIM (mean difference 2.26, 95% confidence interval [CI]: 0.26 to 4.26, p = 0.028) and SARA (-1.21, 95% CI: -2.32 to -0.11, p = 0.032) scores improved after rehabilitation compared with standard care. Compared with standard care, rehabilitation improved SARA scores at 30 weeks (mean difference -1.51, 95% CI: -2.76 to -0.27, p = 0.017), but not mFIM scores (1.74, 95% CI: -0.32 to 3.81, p = 0.098). Frequent adverse events in both groups were fatigue, pain, and falls. Conclusions: Goal-directed rehabilitation improved function at 7 weeks, with improvement in ataxia and health-related quality of life maintained at 30 weeks in individuals with HCA, beyond that of standard care. ANN NEUROL 2025;97:409-424.

Cerebellum (London, England) • June 01, 2025

Kayli Davies, Haloom Rafehi, Liam Fearnley, Penny Snell, Greta Gillies, Tess Field, Gábor Halmágyi, Kishore Kumar, Kate Pope, Renee Smyth, Susan Tomlinson, Stephen Tisch, Chi-chang Tang, Shaun R Watson, Thomas Wellings, Kathy H Wu, David Szmulewicz, Martin Delatycki, Melanie Bahlo, Paul Lockhart

RFC1-related disease, which includes cerebellar ataxia, neuropathy, and vestibular areflexia syndrome (CANVAS), is a late-onset neurodegenerative disorder primarily caused by biallelic AAGGG(n) repeat expansions (RE) in RFC1. The RFC1 locus is highly polymorphic, with multiple pathogenic and non-pathogenic repeat motifs identified. This study aimed to characterise the structure of the RFC1 repeat and determine the pathogenic allele frequency in an Australian cohort. Using a combination of PCR and next generation sequencing techniques, we provide a comprehensive characterisation of the RFC1 repeat locus in an Australian cohort of 232 individuals with adult-onset ataxia and 269 healthy controls. Biallelic pathogenic RFC1 variants were identified in 34.1% of affected individuals. The overwhelming majority (93.7%) have biallelic AAGGG(n) RE, although other pathogenic alleles, including ACAGG(n), AAAGG(>500) and the Māori AAAGG(10-25)AAGGG(n)AAAGG(4-6) configuration were detected in some affected individuals. We also demonstrate the utility of targeted long-read sequencing in resolving complex alleles. The carrier frequency of the pathogenic AAGGG(n) expansion was approximately 1 in 16 in controls, highlighting the potential for pseudodominant inheritance and the likelihood that RFC1-related disease is underdiagnosed. We further demonstrate the significant RFC1 repeat heterogeneity, identifying 16 distinct motifs, complex repeat structures, and at least six motifs with an allele frequency > 1%. The frequency of RFC1-related disease in individuals with adult-onset cerebellar ataxia and the high carrier frequency of pathogenic RFC1 alleles in the Australian population underscores the need for improved diagnostic strategies. Our findings indicate RFC1 RE are a major cause of late-onset cerebellar ataxia and sensory neuropathy in Australia and provide further insights into RFC1 repeat diversity.

Cerebellum (London, England) • June 25, 2024

E Sohns, D Szmulewicz, A Tarnutzer

Disease-specific oculomotor assessments play a crucial role in the early diagnosis of hereditary cerebellar ataxias. Whereas several studies have reported on quantitative oculomotor and vestibular measurements in Friedreich's Ataxia (FRDA), the value of specific oculomotor paradigms remains unclear. We aimed to address this knowledge gap through a systematic literature review and providing disease-specific recommendations for a tailored set of eye-movement recordings in FRDA. MEDLINE and Embase were searched for studies reporting on quantitative oculomotor and/or vestibular measurements in FRDA-patients. Data on oculomotor and vestibular parameters were extracted and correlations with a range of clinical parameters were sought. Included studies (n = 17) reported on 185 patients. Abnormalities observed included the presence of saccadic intrusions (143/161) such as square-wave jerks (SWJ, 90/109) and ocular flutter (21/43), impaired eccentric gaze-holding (40/104), abnormal pursuit (81/93) and angular vestibulo-ocular reflex (aVOR) deficits (39/48). For visually-guided saccades (VGS), we frequently observed increases in saccade latency (27/38) and dysmetric saccades (71/93), whereas saccade velocity was more often preserved (37/43). Augmented anti-saccade (AS) latency, downbeat nystagmus and frequent macro-SWJ correlated with disease duration. Increased AS-latency and VGS-latency, frequent macro-SWJ, reduced aVOR-gain and augmented aVOR peak-latency correlated with disease severity. A broad range of oculomotor and vestibular deficits are documented in the literature. Impairments in pursuit, saccades and aVOR-responses are most commonly reported, and as such, should be prioritized as disease markers. Quantitative oculomotor testing in FRDA may facilitate early diagnosis and prove valuable in monitoring disease progression and treatment response.

Genome Research • June 11, 2024

Haloom Rafehi, Liam Fearnley, Justin Read, Penny Snell, Kayli Davies, Liam Scott, Greta Gillies, Genevieve Thompson, Tess Field, Aleena Eldo, Simon Bodek, Ernest Butler, Luke Chen, John Drago, Himanshu Goel, Anna Hackett, G Halmagyi, Andrew Hannaford, Katya Kotschet, Kishore Kumar, Smitha Kumble, Matthew Lee Archer, Abhishek Malhotra, Mark Paine, Michael Poon, Kate Pope, Katrina Reardon, Steven Ring, Anne Ronan, Matthew Silsby, Renee Smyth, Chloe Stutterd, Mathew Wallis, John Waterston, Thomas Wellings, Kirsty West, Christine Wools, Kathy H Wu, David Szmulewicz, Martin Delatycki, Melanie Bahlo, Paul Lockhart

The cerebellar ataxias (CAs) are a heterogeneous group of disorders characterized by progressive incoordination. Seventeen repeat expansion (RE) loci have been identified as the primary genetic cause and account for >80% of genetic diagnoses. Despite this, diagnostic testing is limited and inefficient, often utilizing single gene assays. This study evaluates the effectiveness of long- and short-read sequencing as diagnostic tools for CA. We recruited 110 individuals (48 females, 62 males) with a clinical diagnosis of CA. Short-read genome sequencing (SR-GS) was performed to identify pathogenic RE and also non-RE variants in 356 genes associated with CA. Independently, long-read sequencing with adaptive sampling (LR-AS) was performed to identify pathogenic RE. SR-GS provided a genetic diagnosis for 38% of the cohort (40/110) including seven non-RE pathogenic variants. RE causes disease in 33 individuals, with the most common condition being SCA27B (n = 24). In comparison, LR-AS identified pathogenic RE in 29 individuals. RE identification for the two methods was concordant apart from four SCA27B cases not detected by LR-AS due to low read depth. For both technologies manual review of the RE alignment enhances diagnostic outcomes. Orthogonal testing for SCA27B revealed a 15% and 0% false positive rate for SR-GS and LR-AS, respectively. In conclusion, both technologies are powerful screening tools for CA. SR-GS is a mature technology currently used by diagnostic providers, requiring only minor changes in bioinformatic workflows to enable CA diagnostics. LR-AS offers considerable advantages in the context of RE detection and characterization but requires optimization before clinical implementation.

Cerebellum (London, England) • January 05, 2024

David Szmulewicz, Rocco Galli, Alexander Tarnutzer

In patients with cerebellar ataxia (CA), symptoms related to oculomotor dysfunction significantly affect quality of life (QoL). This study aimed to analyze the literature on patient-related outcome measures (PROMs) assessing QoL impacts of vestibular and cerebellar oculomotor abnormalities in patients with CA to identify the strengths and limitations of existing scales and highlight any areas of unmet need. A systematic review was conducted (Medline, Embase) of English-language original articles reporting on QoL measures in patients with vertigo, dizziness or CA. Pre-specified parameters were retrieved, including diseases studied, scales applied and conclusions drawn. Our search yielded 3671 articles of which 467 studies (n = 111,606 participants) were deemed relevant. The most frequently studied disease entities were (a) non-specific dizziness/gait imbalance (114 studies; 54,581 participants), (b) vestibular schwannomas (66; 15,360), and (c) vestibular disorders not further specified (66; 10,259). The Dizziness Handicap Inventory (DHI) was the most frequently used PROM to assess QoL (n = 91,851), followed by the Penn Acoustic Neuroma Quality-of-Life Scale (n = 12,027) and the Activities-Specific Balance Confidence Scale (n = 2'471). QoL-scores capturing symptoms related to oculomotor abnormalities in CA were rare, focused on visual impairments (e.g., National-Eye-Institute Visual Function Questionnaire, Oscillopsia Functional Impact, oscillopsia severity score) and were unvalidated. The DHI remains the most widely used and versatile scale for evaluating dizziness. A lack of well-established PROMs for assessing the impact of oculomotor-related symptoms on QoL in CA was noted, emphasizing the need for developing and validating a new QoL-score dedicated to the oculomotor domain for individuals with CA.