Retinal layer segmentation: Non-invasive technique demonstrating hyperplasia of nerve fibers and ganglion cells in the Ataxia of Charlevoix-Saguenay

Purpose To present a new retinal layer segmentation technique, in order to evaluate the existence of nerve fiber hyperplasia in patients with the autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS). Methods This observational cross-sectional study included five patients with a molecular diagnosis of ARSACS and 5 sex and age-matched healthy controls underwent a full ophthalmologic examination, which included a new technique to segment the retinal layers using Optical Coherence Tomography. Images and data were correlated with diffusion tensor colour encoded MRI maps, diffusion tensor tractographies, and retinal anatomopathological analysis. Results Every patient showed increased thickness in the internal layers of the retina (inner limiting membrane, nerve fiber layer and ganglion cell layer) in OCT evaluation. These findings suggest the presence of neurofilamentous hyperplasia in the retina of patients with ARSACS and correlated with anatomopathological findings. Conclusion We found evidence of ganglion cell and nerve fiber hyperplasia in the retina of ARSACS patients. Thus, a revision of the aetiopathogenic mechanisms is necessary in this disease.