AI Article Synopsis
- Spinocerebellar ataxia (SCA) 27B is caused by an abnormal increase of GAA repeats in the FGF14 gene, leading to coordination issues, first identified in late 2022.
- Two patients with late-onset SCA27B exhibited mild cerebellar ataxia and omnidirectional downbeat nystagmus, especially noticeable when their heads were suspended, but showed normal head impulse and caloric test results.
- The downbeat nystagmus in these patients likely indicates a disruption in the vestibulo-ocular reflex due to cerebellar cortex issues, which may serve as a characteristic sign of SCA27B.
Article Abstract
Background: Spinocerebellar ataxia (SCA) 27B, first reported in late 2022, is caused by the abnormal expansion of GAA repeats in the first intron of the FGF14 gene, which encodes the fibroblast growth factor 14.
Case Presentation: We present two late-onset cases, each manifesting mild cerebellar ataxia accompanied by omnidirectional downbeat nystagmus, which was enhanced in a suspended head position. None of the patients exhibited impaired head impulse or caloric tests. Repeat-primed PCR and targeted long-read nanopore sequence analysis of the FGF14 GAA repeat site identified more than 250 repeats, leading to the diagnosis of SCA27B.
Discussion: Downbeat nystagmus is reported to be associated with disturbances in the suppression of the vestibulo-ocular reflex (VOR). Our patients with SCA27B demonstrated downbeat nystagmus, likely due to a disruption of the VOR at the level of the cerebellar cortex, a potentially characteristic clinical feature of SCA27B. We have included video footages of eye movements recorded using Frenzel goggles for these cases.
Conclusions: Omnidirectional downbeat nystagmus may be a distinctive clinical feature of SCA27B.
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| http://dx.doi.org/10.1016/j.jns.2023.120849 | DOI Listing |
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