Abstract Details

Title Downbeat Nystagmus and Causes of Diplopia in SCA27B: A Newly Described, Novel yet Common, Entity with Unique Neuro-ophthalmologic Presentations

Topic Neuro-ophthalmology/Neuro-otology

Presentation(s) P2 - Poster Session 2 (8:00 AM-9:00 AM)

Poster/Presentation
Number 11-003

Objective Not applicable

Background Spinocerebellar ataxia type 27B (SCA27B) due to GAA trinucleotide repeats in the fibroblast growth factor 14 (FGF14) gene, newly discovered in 2022, is emerging as a common cause of late-onset ataxia, as well as neuro-ophthalmologic presentations. We aim to familiarize the neurologist with this new diagnosis and to delineate the causes of diplopia, which have not yet been described.

Design/Methods Not applicable

Results Retrospective analysis of 12 patients [mean age at symptom onset 64 (range 44-73) years] with genetically confirmed SCA27B. Seven patients had episodic or persistent oscillopsia or diplopia at symptom onset, neurologically isolated for several years in 3. Eight of 11 treated patients experienced improvement in oscillopsia and/or imbalance on 4-aminopyridine. All patients had downbeat nystagmus detectable on exam, though it was clinically obvious in only 3. Diplopia was present in 9 patients: vertical due to skew deviation (static or alternating on lateral gaze) (n=6) and/or horizontal due to vergence dysfunction (n=8), including convergence insufficiency (n=4) and divergence insufficiency with cerebellar esotropia (n=3). One patient had saccadic slowing, confirmed with oculography.

Conclusions SCA27B is a newly discovered diagnosis that is evolving as a common cause of late-onset episodic or slowly progressive ataxia and idiopathic downbeat nystagmus. Patients often present with oscillopsia or diplopia, including unique features such as hours-long discrete episodes, and exam features can be subtle; thus, it is important that neurologists become familiar with this condition and its neuro-ophthalmic manifestations, particularly given its uniquely responsivity to 4-aminopyridine.

Authors/Disclosures
Alexander S. Fein, MD PRESENTER	Dr. Fein has nothing to disclose.
Daniel R. Gold, DO (Johns Hopkins)	Dr. Gold has received personal compensation in the range of $500-$4,999 for serving as an Editor, Associate Editor, or Editorial Advisory Board Member for Springer . Dr. Gold has received publishing royalties from a publication relating to health care.
Anand K. Bery, MD (Mass Eye and Ear)	Dr. Bery has nothing to disclose.
Weiyi Mu, ScM	Prof. Mu has received personal compensation in the range of $500-$4,999 for serving as a Consultant for UCB BioPharma.
Nicolas J. Abreu, MD (NYU Langone)	Dr. Abreu has received personal compensation in the range of $500-$4,999 for serving on a Scientific Advisory or Data Safety Monitoring board for Sanofi. The institution of Dr. Abreu has received research support from Adult Polyglucosan Body Disease Research Foundation. The institution of Dr. Abreu has received research support from Sanofi Genzyme. The institution of Dr. Abreu has received research support from Takeda. The institution of Dr. Abreu has received research support from Sangamo. The institution of Dr. Abreu has received research support from BDSRA Foundation.
Connolly Steigerwald, CGC	Ms. Steigerwald has received personal compensation for serving as an employee of Ambry Genetics. Ms. Steigerwald has received personal compensation in the range of $5,000-$9,999 for serving as a Consultant for Vigil Neuroscience.
Janet C. Rucker, MD	Dr. Rucker has nothing to disclose.

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