April 2009
Volume 50, Issue 13
ARVO Annual Meeting Abstract  |   April 2009
Spinocerebellar Ataxia Type 7 (SCA 7) - Electrophysiological Findings
Author Affiliations & Notes
  • T. Hugosson
    Department of Ophthalmology, Lund University Hospital, Lund, Sweden
  • L. Gränse
    Department of Ophthalmology, Lund University Hospital, Lund, Sweden
  • V. Ponjavic
    Department of Ophthalmology, Lund University Hospital, Lund, Sweden
  • S. Andréasson
    Department of Ophthalmology, Lund University Hospital, Lund, Sweden
  • Footnotes
    Commercial Relationships  T. Hugosson, None; L. Gränse, None; V. Ponjavic, None; S. Andréasson, None.
  • Footnotes
    Support  Supported by the Faculty of Medicine, Lund University, and grants from the Swedish Medical Research Council and the Foundation Fighting Blindness, Owings Mills, Maryland.
Investigative Ophthalmology & Visual Science April 2009, Vol.50, 3860. doi:
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      T. Hugosson, L. Gränse, V. Ponjavic, S. Andréasson; Spinocerebellar Ataxia Type 7 (SCA 7) - Electrophysiological Findings. Invest. Ophthalmol. Vis. Sci. 2009;50(13):3860.

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      © ARVO (1962-2015); The Authors (2016-present)

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Purpose: : To characterize the clinical phenotype regarding retinal function and macular appearance in patients with spinocerebellar ataxia type 7 (SCA 7), with an emphasis on electrophysiological findings.

Methods: : Three patients from two Swedish families were given an ophthalmological examination including visual acuity, fundus inspection, Farnsworth's colour vision test, Goldmann perimetry, full-field electroretinography (full-field ERG), multifocal electroretinography (mfERG) and optical coherence tomography (OCT). DNA was analyzed with polymerase chain reaction for CAG trinucleotide expansion repeats in the SCA 7 gene.

Results: : Molecular analysis demonstrated abnormally expanded CAG repeats in the gene for SCA 7, which encodes the protein ataxin-7, thus confirming the diagnosis SCA 7. In the oldest patient very discreet pigmentary changes in the maculae were found, but with that exception the patients had a normal ophthalmoscopic fundus appearance and OCT demonstrated only minor changes. MfERG indicated predominantly central involvement, especially in the early disease stages, which in pace with disease progression extended from the center to the more peripheral areas. Full-field ERG in the oldest patient demonstrated bilaterally distinctly prolonged 30-Hz flicker implicit time, verifying widespread cone photoreceptor degeneration.

Conclusions: : The patients with genetically confirmed SCA 7 presented an early macular dysfunction, preceding any signs of abnormalities in fundus appearance. According to the electrophysiological findings the primary dysfunction involves the cone photoreceptors in the foveal region, however in an older patient involvement of cone photoreceptors throughout the retina was verified. This is in accordance with the theory that ataxin-7 interacts with CRX transcription, since it is known that mutations in the CRX gene cause cone-rod dystrophy.

Keywords: electrophysiology: clinical • macula/fovea • genetics 

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