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R.P. Hagan, C.E. Willoughby, T.J. Shergill, R. Mountford, N. Fletcher, M.C. Brown, G. Kyle; ‘Negative’ ERG Phenotype in a UK Family Presenting With Spinocerebellar Ataxia . Invest. Ophthalmol. Vis. Sci. 2005;46(13):4558.
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Purpose: To define the ocular phenotype including electrodiagnostic testing in a family with spinocerebellar ataxia (SCA). Methods: Three members of a UK family with SCA had an ocular and neurological assessment. Electrodiagnostic testing (ERG, VEP, and EOG) was performed according to the standards of the International Society for Clinical Electrophysiology of Vision (ISCEV). Serum copper, caeruloplasmin, vitamins B12 and E levels were determined to exclude a metabolic basis for the SCA. Mutational screening for SCA (SCA 1, SCA 2, SCA 3, SCA 6 and SCA 7) and Friedreich’s Ataxia (frataxin gene) was performed to identify the number of triplet repeats or expansion mutations. Results: All members of the family had neurological features consistent with SCA. The ocular phenotype consisted of retinal pigment mottling with reduced ERGs to all modes of stimulation. In particular, all had ‘negative’ ERG to standard mixed rod/cone mediated stimulation (cds/m2). Serum copper, caeruloplasmin, vitamins B12 and E levels were normal in all three family members. Genetic testing for SCA 1, SCA 2, SCA 3, SCA 6 and SCA 7 and Friedreich Ataxia was normal. Conclusions: This represents the first report of a UK family with a negative ERG associated with SCA. This finding supports the findings of Kimura et al who also have found the negative ERG phenotype in an as yet genetically undescribed SCA (2 out of 3). This suggests the existence of a retinopathy associated with SCA which has a ‘negative’ ERG phenotype, which spans across at least two continents. References: Kimura A, Nemoto H, Nishimiya J, Yuasa T and Yamazaki H: Spinocerebellar degeneration with negative electroretinogram: dysfunction of the bipolars cells. Doc. Ophtham. V103 N 3 241–7.
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