Ophthalmic Features of Spinocerebellar Ataxia Type 7: A Case Report

Abstract

BACKGROUND Spinocerebellar ataxia (SCA) is an inherited progressive neurodegenerative disorder characterized by late-onset cerebellar and brainstem dysfunction. It is an autosomal dominant condition with monoallelic pathogenic expansion in the ATXN7 gene. Patients have neurological deficits, including ataxia and dysarthria. Visual symptoms are the first presenting signs in patients with SCA type 7 (SCA7), including severely affected visual acuity and color vision, ocular motility impairment, and retinal macular degeneration. This is one of the first reports of the existence of keratoconus in a patient with SCA7. Few theories explain this coexistence, including vigorous rubbing of the eyes, and genetic and environmental etiologies. CASE REPORT A 34-year-old man with SCA7 underwent genetic and ophthalmic investigations. Multiple family members of the patient had a positive history of ataxia. He had an abnormal posterior and anterior corneal elevation on Pentacam (Pentacam-Oculus, Optikgeräte GmbH, Wetzlar, Germany) and was eventually diagnosed with keratoconus in both eyes, which is not a known feature of SCA7. Later, he underwent a penetrating keratoplasty in the left eye with no subsequent improvement in vision. No further treatment was offered to the patient due to the guarded visual prognosis caused by the retinal pathology. He continues to have routine follow-ups in the Ophthalmology Clinic. CONCLUSIONS This case reinforces the importance of recognizing the guarded visual outcome in these patients due to the macular degeneration and progressive nature of the disease. Therefore, appropriate and adequate patient counseling about the visual prognosis is essential before proceeding with any ocular surgical interventions.

Figure 1.

The family tree (pedigree) of spinocerebellar ataxia type 7 (SCA7)-affected individuals. Arrowhead shows the reported case; filled symbols indicate clinically affected individuals with SCA7 (red) and keratoconus (blue).

Figure 2.

Biomicroscopic slit lamp photos: (A) Right eye with diffused illumination. (B) With the slit beam, the right eye showed advanced keratoconus with central corneal scarring. (C) Left eye with diffused illumination. (D) With the slit beam, the left eye showed a clear sutureless corneal graft with no signs of rejection.

Figure 3.

(A) Ultrawide-field (UWF) Optos (Optos California, Dunfermline, Scotland, United Kingdom) fundus photo of the right eye, with bull’s eye maculopathy (arrowhead) and optic disc pallor. (B) Left eye showed bull’s eye maculopathy (arrowhead) with optic disc pallor.

Figure 4.

(A) Belin/Ambrosio Enhanced Ectasia Display of the right eye with elevation data on the left and pachymetric data on the right. (B) Keratometric values of the right eye on Pentacam (Pentacam-Oculus, Optikgeräte GmbH, Wetzlar, Germany) showed the displaced cone and inferior steepening on the axial curvature map, and a significant elevation suggestive of keratoconus in the posterior float.

Figure 5.

Ocular coherence tomography of the left eye (A) and right eye (B) with corresponding en face infrared images showed foveal hyperreflectivity with inverse shadowing indicating foveal atrophy in both eyes due to the loss of photoreceptors.

Figure 6.

Electroretinogram showed a nonrecordable cone response in both eyes.