Diagnostic Optic Nerve Features in Autosomal Recessive Spastic Ataxia of Charlevoix-Saguenay

A 23-year-old man was referred to neuro-ophthalmology for gaze-evoked nystagmus. He had been evaluated for lower-limb incoordination due to a history of slowly progressive walking difficulty since childhood. He had asthma and eczema and no prior ophthalmic history. Magnetic resonance imaging (MRI) of his brain revealed cerebellar vermis atrophy.

On examination, visual acuities were 6/6 OU, with normal color vision and pupillary reflexes and no relative afferent pupillary defect. He had a gaze-evoked nystagmus but no oscillopsia and normal pursuit and saccades. Fundus examination revealed normal optic nerve heads with pale yellow peripapillary striae radiating from the discs predominantly following the major vascular arcades (Figure 1). The macula showed a reduced foveal reflex, and the peripheral retina was normal. Optical coherence tomography (OCT) imaging was performed, which showed significant thickening of the global peripapillary retinal nerve fiber layer (RNFL) in both eyes (right eye, 153 μm; left eye, 145 μm) and absence of the normal foveal depression (Figure 2). After genetic evaluation for ataxia at age 18 years and identification of a gene variation previously presumed to be a polymorphism, he was finally diagnosed with autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS).