Reduction in retinal nerve fiber layer thickness in tuberous sclerosis complex

The aim of our study was to non-invasively investigate central nervous system axonal integrity in patients with tuberous sclerosis complex (TSC). Diffuse microstructural white matter abnormalities reflecting axonal disorganization, reduced/altered myelination, or gliosis have been described in individuals with TSC. Optical coherence tomography (OCT) is a fast, easy-to-perform, non-invasive, and cost-efficient method to assess retinal morphology in vivo and to measure the thickness of the retinal nerve fiber layer (RNFL). In order to assess central nervous system axonal integrity, eight subjects with TSC have been investigated by OCT to evaluate RNFL and they have been compared with matched healthy controls. When comparing mean overall RNFL thicknesses of the TSC group with those of the control group, the TSC group presented with significantly lower RNFL values, compared to the control group, in the temporal quadrant (62.5 +/- 6.9 vs. 76.9 +/- 5.4; t = 14.438; p < 0.0001). Since a reduced RNFL thickness might be seen as an indicator of chronic axonal degeneration or lack of appropriate neuronal development, our results support the presence of axonal alterations in TSC and also that white matter disorganization could be much more diffuse than originally thought. Since axonal alterations directly derive from mammalian target of rapamycin (mTOR) overactivation, which occurs early during fetus development, the RNFL thinning we observed could represent one of the facets of such early neurodevelopmental abnormalities.