Thickening of peripapillar retinal fibers for the diagnosis of autosomal recessive spastic ataxia of Charlevoix-Saguenay.

Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is characterized by the presence of myelinated retinal fibers. This typical feature is very helpful for the diagnosis but is not always observed in patients outside Quebec. Apart from phenotype variations, misinterpretation of the funduscopy may explain discrepancies and misdiagnosis. We analyze the modification of retinal fibers layer using the funduscopy and the optical coherence tomography (OCT) in two French patients having spinocerebellar ataxia associated with a spastic paraparesia with genetically confirmed ARSACS. In both patients the funduscopy showed a swollen and striated aspect of peripapillar fibers along the retinal vessels and in the intermaculopapillar region. The OCT displayed an important thickening of the optical fibers layer mainly in upper and lower temporal area without attenuation of deep layers, as well as a filling in of the foveolar depression with thickening of the ganglion cell layer normally absent from the foveola. The aspect of funduscopy and OCT in our patients does not correspond to the classical description of myelin fibers encountered in 0.3% to 1% of the population. Thus, ARSACS might be underdiagnosed because of an erroneous interpretation of funduscopy. When considering the diagnosis of ARSACS, the neurologist should ask the ophthalmologist to search for thickening of peripapillar retinal fibers by both funduscopy and OCT rather than myelinated retinal fibers. This ophthalmological consideration has avoided misdiagnosis and led to the description of new mutations in our cases.