RFC1 and late-onset spinocerebellar ataxia 27b: Noteworthy, for RFC1-related ataxia and SCA27B a combination of aVOR gain measurements and assessment for spontaneous (downbeating) nystagmus was recommended to allow a better distinction between these two entities as aVOR gain deficits are usually more pronounced for RFC1-related ataxia compared to SCA27B [49].