Inner Retinal Dysfunction in the Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay

Abstract

The autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is associated with structural retinal abnormalities either directly visible on funduscopy or revealed by optical coherence tomography (OCT). Most patients with ARSACS have a whitish peripapillary appearance corresponding to a thickening of the peripapillary retinal nerve fiber layer. OCT has also shown an absence of the physiological foveal depression. Abnormal electroretinography (ERG) has previously been reported in only two cases, without further details. This report describes a patient with ARSACS in whom careful full-field ERG revealed dysfunction of the retinal On− bipolar cells with sparing of photoreceptor function. This is the first report of inner retinal dysfunction in ARSACS.

Thickened Retinal Nerve Fiber Layer Without Hypermyelination in Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay

“…4 There are no reports of VA loss, reduced visual fields, or color vision changes in patients with autosomal recessive spastic ataxia of Charlevoix-Saguenay. 18 This is consistent with findings in our patient, who had normal vision.…”

“…9,10 Given these criteria, our patient had thickening in both eyes, with an average thickness of 180 µm in the right eye and 177 µm in the left eye. Peripapillary thickening of the RNFL has a specificity of 100% but reduced sensitivity in certain patient populations; for example, a study of Japanese patients with the disorder found no RNFL thickening on OCT. 18 Of 17 patients diagnosed with autosomal recessive spastic ataxia of Charlevoix-Saguenay in a British study, all patients were found to have RNFL thickening. 9 The authors thus defined this thickening as a hallmark of the disorder and a way to differentiate the disease from other causes of ataxia.…”

Asymptomatic Retinal Nerve Fiber Layer Thickening in a Patient With Ataxia

“…7 Autosomal recessive spastic ataxia of Charlevoix-Saguenay may be associated with fovea plana. 8 This case presents mild fovea plana corresponding to grade 1 in the grading scale proposed by Thomas et al 9 with absence of plexiform layers extrusion. Macular microcysts have also been described in ARSACS, but their pathological significance is yet to be determined.…”