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An Unusual Fundus Finding in a Teenage Girl

Educational Objective
Based on this clinical scenario and the accompanying image, understand how to arrive at a correct diagnosis.
1 Credit CME

A 16-year-old girl presented to our ataxia unit with a report of a peculiar finding in fundoscopy. Her parents were nonconsanguineous, and her family history was unremarkable. She had unsteadiness and frequent falls at gait initiation since age 16 months. There was a progressive worsening of her gait difficulties, and she complained of loss of balance.

On examination, she had saccadic pursuit, subtle appendicular ataxia, and a spastic gait with a wide base. She could not stand or walk with her feet in the tandem position. Her muscle strength was normal. Achilles tendon reflexes and plantar responses were absent, and vibration sense was decreased in her toes and ankles.

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C. Autosomal recessive spastic ataxia of Charlevoix-Saguenay

Brain magnetic resonance imaging (MRI) showed upper cerebellar vermis atrophy, linear pontine T2 hypointensities, lateral pontine T2 hyperintensities, a posterior fossa arachnoid cyst, and thinning of the corpus callosum and cervical spinal cord (Figure 2). Per the clinical features, fundoscopy findings, and abnormalities on MRI, autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) was suspected. Genetic testing identified biallelic pathogenic SACS mutations.

The first description of ARSACS derives from families of the Charlevoix and Saguenay regions of Quebec, Canada. The patients had unsteadiness and falls at gait initiation, followed by slowly progressive spastic ataxia and axonal-demyelinating peripheral neuropathy. Every affected individual presented with slurred speech, saccadic pursuit, and nystagmus, accompanied by a distinctive fundus appearance involving an increased visibility of the retinal nerve fibers hiding parts of the retinal vessels.1 Identification of the causative gene, SACS, and its product, the protein sacsin, occurred in 2000. Outside of Canada, most patients have disease onset in the first decade of life and display progressive spastic ataxia and peripheral neuropathy. However, retinal abnormalities are less frequent in non-Canadian individuals, and divergent presentations may exhibit adult onset, hearing loss, and supranuclear vertical gaze palsy.2 Moreover, the ataxia, spasticity, and peripheral neuropathy of the classic ARSACS triad might each be missing in patients with SACS mutations.3 Findings on MRI include upper cerebellar vermis atrophy, linear pontine T2 hypointensities, lateral pontine T2 hyperintensities, thickening of middle cerebellar peduncles, posterior fossa arachnoid cyst, corpus callosum thinning, and parietal atrophy.3 Optical coherence tomography reveals thickening of the RNFL, which is unknown in any other progressive neurodegenerative condition. Also, OCT is more sensitive in detecting retinal abnormalities in ARSACS compared with fundoscopy.4

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Article Information

Corresponding Author: Flávio Moura Rezende Filho, MD, Division of General Neurology and Ataxia Unit, Department of Neurology, Universidade Federal de São Paulo, Rua Pedro de Toledo 650, 04039-002 São Paulo, Brazil (flaviomourarezende@hotmail.com).

Correction: This article was corrected in the December 2018 print issue to fix the presentation of the surnames in the byline with respect to the dual surname (Rezende Filho) of Flavio Moura Rezende Filho and the single surname (Barsottini) of Orlando G. Póvoas Barsottini.

Published Online: October 15, 2018. doi:10.1001/jamaneurol.2018.3108

Conflict of Interest Disclosures: None reported.

Additional Contributions: We thank the patient for granting permission to publish this information. We are grateful to the Laboratory NIM Genetics for providing genetic testing. This organization was not compensated for this contribution.

References
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2.
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Campuzano  V, Montermini  L, Moltò  MD,  et al.  Friedreich’s ataxia: autosomal recessive disease caused by an intronic GAA triplet repeat expansion.  Science. 1996;271(5254):1423-1427. doi:10.1126/science.271.5254.1423PubMedGoogle ScholarCrossref
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Noval  S, Contreras  I, Sanz-Gallego  I, Manrique  RK, Arpa  J.  Ophthalmic features of Friedreich ataxia.  Eye (Lond). 2012;26(2):315-320. doi:10.1038/eye.2011.291PubMedGoogle ScholarCrossref
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Salinas  S, Proukakis  C, Crosby  A, Warner  TT.  Hereditary spastic paraplegia: clinical features and pathogenetic mechanisms.  Lancet Neurol. 2008;7(12):1127-1138. doi:10.1016/S1474-4422(08)70258-8PubMedGoogle ScholarCrossref
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