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Journal of neurology 269(8), 4363-4374 (2022). doi:10.1007/s00415-022-11071-5, Published by Steinkopff, [Darmstadt]

Movement disorders 37(2), 405-410 (2022). doi:10.1002/mds.28844, Published by Wiley, New York, NY

The cerebellar nuclei are a brain region with high iron content. Surprisingly, little is known about iron content in the cerebellar nuclei and its possible contribution to pathology in cerebellar ataxias, with the only exception of Friedreich’s ataxia. In the present exploratory cross-sectional study, quantitative susceptibility mapping was used to investigate volume, iron concentration and total iron content of the dentate nuclei in common types of hereditary and non-hereditary degenerative ataxias. Seventy-nine patients with spinocerebellar ataxias of types 1, 2, 3 and 6; 15 patients with Friedreich’s ataxia; 18 patients with multiple system atrophy, cerebellar type and 111 healthy controls were also included. All underwent 3 T MRI and clinical assessments. For each specific ataxia subtype, voxel-based and volumes-of-interest-based group analyses were performed in comparison with a corresponding age- and sex-matched control group, both for volume, magnetic susceptiblity (indicating iron concentration) and susceptibility mass (indicating total iron content) of the dentate nuclei. Spinocerebellar ataxia of type 1 and multiple system atrophy, cerebellar type patients showed higher susceptibilities in large parts of the dentate nucleus but unaltered susceptibility masses compared with controls. Friedreich’s ataxia patients and, only on a trend level, spinocerebellar ataxia of type 2 patients showed higher susceptibilities in more circumscribed parts of the dentate. In contrast, spinocerebellar ataxia of type 6 patients revealed lower susceptibilities and susceptibility masses compared with controls throughout the dentate nucleus. Spinocerebellar ataxia of type 3 patients showed no significant changes in susceptibility and susceptibility mass. Lower volume of the dentate nuclei was found to varying degrees in all ataxia types. It was most pronounced in spinocerebellar ataxia of type 6 patients and least prominent in spinocerebellar ataxia of type 3 patients. The findings show that alterations in susceptibility revealed by quantitative susceptibility mapping are common in the dentate nuclei in different types of cerebellar ataxias. The most striking changes in susceptibility were found in spinocerebellar ataxia of type 1, multiple system atrophy, cerebellar type and spinocerebellar ataxia of type 6. Because iron content is known to be high in glial cells but not in neurons of the cerebellar nuclei, the higher susceptibility in spinocerebellar ataxia of type 1 and multiple system atrophy, cerebellar type may be explained by a reduction of neurons (increase in iron concentration) and/or an increase in iron-rich glial cells, e.g. microgliosis. Hypomyelination also leads to higher susceptibility and could also contribute. The lower susceptibility in SCA6 suggests a loss of iron-rich glial cells. Quantitative susceptibility maps warrant future studies of iron content and iron-rich cells in ataxias to gain a more comprehensive understanding of the pathogenesis of these diseases.

During recent decades, many studies have yielded evidence for cerebellar involvement in cognitive, emotional and affective processes besides the well-known cerebellar contribution to motor performance and learning (Koziol et al., 2014; Marien et al., 2014; Van Overwalle et al., 2014; Strata, 2015; Adamaszek et al., 2017; Kansal et al., 2017; Guell et al., 2018; King et al., 2019). Cerebellar diseases can result in executive, linguistic and visuospatial dysfunctions as well as problems with the regulation of emotion and affect. This combination of non-motor symptoms has been named cerebellar cognitive affective/Schmahmann syndrome (CCAS) (Schmahmann and Sherman, 1998). For many years, diagnosis has relied on non-standardized bedside cognitive examination and, if available, detailed neuropsychological test batteries. A short and easily applicable bedside test (CCAS Scale), published by Hoche et al. (2018) in Brain, was developed to screen for CCAS and is already in widespread use. We therefore believe that it is important to share our recent findings that the reference values published by Hoche and colleagues may apply only within a limited age and education range, while their more universal application may lead to a substantial number of false-positive test results.

[Background] Mutations in the mitochondrial DNA polymerase gamma are causing a wide phenotypic spectrum including ataxia as one of the most common presentations., [Objective] The objective of this study was to determine the course of disease of polymerase gamma–related ataxia., [Methods] In a prospective natural history study, we assessed 24 adult ataxia patients with biallelic polymerase gamma mutations for (1) severity of cerebellar dysfunction using the Scale for the Assessment and Rating of Ataxia score, (2) presence of nonataxia signs using the Inventory of Non-Ataxia Symptoms, (3) gray- and white-matter changes in brain MRI, and (4) findings in nerve conduction studies., [Results] Assessment included follow-up visits up to 11.6 years. The Scale for the Assessment and Rating of Ataxia showed a mean annual increase of 1.02 ± 0.78 points/year. Disease progression was faster in patients with age at onset ≤ 30 years (1.5 Scale for the Assessment and Rating of Ataxia points/year) than with later onset (0.5 points/year); P = 0.008. The Inventory of Non-Ataxia Symptoms count increased by 0.30 ± 0.4 points/year. External ophthalmoplegia, brain stem oculomotor signs, areflexia, and sensory deficits were the most common nonataxic features. On MRI cerebellar atrophy was mild. T2 signal alterations affected mostly cerebellar white matter, middle cerebellar peduncles, thalamus, brain stem, and occipital and frontal white matter. Within 4 years, progression was primarily observed in the context of repeated epileptic seizures. Nerve conduction studies revealed axonal sensory peripheral neuropathy with mild motor nerve involvement. Exploratory sample size calculation implied 38 patients per arm as sufficient to detect a reduction of progression by 50% in hypothetical interventions within a 1-year trial., [Conclusion] The results recommend the Scale for the Assessment and Rating of Ataxia as a primary outcome measure for future interventional trials in polymerase gamma–related ataxia. © 2021 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society., This work was supported, in part, via the European Union's Horizon 2020 research and innovation program under the ERA-NET Cofund action no. 643578. It was supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) no. 441409627, as part of the PROSPAX consortium under the frame of EJP RD, the European Joint Programme on Rare Diseases, under the EJP RD COFUND-EJP no. 825575 (to M.S. and B.v.d.W.) and to the PREPARE consortium (01GM1607; to M.S. and B.v.d.W.).

Background Traditionally, cerebellar disorders including ataxias have been associated with deficits in motor control and motor learning. Since the 1980’s growing evidence has emerged that cerebellar diseases also impede cognitive and affective processes such as executive and linguistic functions, visuospatial abilities and regulation of emotion and affect. This combination of non-motor symptoms has been named Cerebellar Cognitive Affective/ Schmahmann Syndrome (CCAS). To date, diagnosis relies on non-standardized bedside cognitive examination and, if available, detailed neuropsychological test batteries. Recently, a short and easy applicable bedside test (CCAS Scale) has been developed to screen for CCAS. It has been validated in an US-American cohort of adults with cerebellar disorders and healthy controls. As yet, the CCAS Scale has only been available in American English. We present a German version of the scale and the study protocol of its ongoing validation in a German-speaking patient cohort. Methods A preliminary German version has been created from the original CCAS Scale using a standardized translation procedure. This version has been pre-tested in cerebellar patients and healthy controls including medical experts and laypersons to ensure that instructions are well understandable, and that no information has been lost or added during translation. This preliminary German version will be validated in a minimum of 65 patients with cerebellar disease and 65 matched healthy controls. We test whether selectivity and sensitivity of the German CCAS Scale is comparable to the original CCAS Scale using the same cut-off values for each of the test items, and the same pass/ fail criteria to determine the presence of CCAS. Furthermore, internal consistency, test-retest and interrater reliability will be evaluated. In addition, construct validity will be tested in a subset of patients and controls in whom detailed neuropsychological testing will be available. Secondary aims will be examination of possible correlations between clinical features (e.g. disease duration, clinical ataxia scores) and CCAS scores. Perspective The overall aim is to deliver a validated bedside test to screen for CCAS in German-speaking patients which can also be used in future natural history and therapeutic trials. Study registration The study is registered at the German Clinical Study Register (DRKS-ID: DRKS00016854).