OPHTALMIC FEATURES OF SPINOCEREBELLAR ATAXIA TYPE 7: CORNEAL ENDOTHELIAL CELL DENSITY CORRELATES WITH ATAXIA RATE AND MUTATION LENGHT

Abstract

 

Purpose

 

To analyze the relation between ophthalmologic and motor changes in spinocerebellar ataxia type 7 (SCA7)

 

Methods

 

Design: Case series<br /> Participants: Sixteen SCA7 patients from the State of Veracruz, in Mexico.<br /> Methods: SCA7 patients underwent a comprehensive ophthalmic examination including uncorrected and corrected distance visual acuity, ocular extrinsic motility testing, slit-lamp biomicroscopy of the anterior segment, fundoscopy and measurement of intraocular pressure, color vision evaluation with Ishihara color plates, and optical coherence tomography (OCT) of the optic nerve and macula. Changes and alterations in the endothelium and in electroretinographic patterns were explored, and a complete neurologic evaluation using the Scale for the Assessment and Rating of Ataxia (SARA) was done as well.<br /> Main outcome measures: optical coherence tomography (OCT) findings of the optic nerve and macula, alterations in the endothelium and in electroretinographic patterns, and SARA scores.

 

Results

 

All patients showed various degrees of visual impairment mainly due to macular deterioration. Notably, they also presented decreased endothelial cell density (ECD).<br /> Pairwise correlations of ECD with number of CAG repeats and severity of motor symptoms quantified with the SARA scores were inverse (r=‒0.46, p=0.083 and r=‒64, p=0.009, respectively). Further analyses indicated an average ECD decrease of 48.4 (p=0.006) per unit of change on the number of CAG repeats, and of 74.6 (p=0.001) per unit of change on the SARA scores.

 

Conclusions

 

The results agree with previous ophthalmological findings regarding the widespread effect of SCA7 mutation on the patient’s visual system. However, the results also show a significant negative correlation of decreased ECD with both CAG repetitions and SARA scores. This suggests that motor systems degenerate in parallel with visual systems, although more research is needed to determine whether the degeneration is caused by the same mechanisms.