Macular Retinal Nerve Fiber Layer Axonal Damage and Macular Retinal Ganglion Cell Loss in Clinically Isolated Syndrome: A Potential Marker of Neurodegeneration? (P4.265)

Background: Optical Coherence Tomography (OCT) can measure retinal nerve fiber layer (RFNL) (marker of axonal change) and retinal ganglion cell layer (GCL) (marker of cellular change) thicknesses. Peripapillary RNFL thinning can be used as a potential marker of neurodegeneration in multiple sclerosis and it has been demonstrated to correlate with brain atrophy. It is unknown whether RNFL thinning is present in the early stages of MS. Objectives: We aimed to (i) measure macular RFNL (mRFNL) and GCL (mGCL) thicknesses at the onset of clinically isolated syndrome (CIS), (ii) investigate correlations between these measurements and brain grey matter tissue fraction (GMF). Methods: We recruited 16 CIS subjects (8F, mean [SD] age 33.5[±7.27]), 14 of them with optic neuritis (ON), within 3 months of symptoms onset, 10 healthy controls (6F, mean [SD] age 34.20[±7.07]. All subjects undergo a MRI protocol at 3T and brain tissue segmentation was performed using SPM12. OCT images were acquired with a Spectralis Heidelberg model. Linear regression models were used to compare differences between groups adjusting for age and gender. Pearson’s correlations compared OCT parameters and GMF in CIS patients. Results: In CIS patients, the mRFNL was thinner in both affected (20.06 ± 1.84), and fellow eyes (20.70±1.44) compared with controls (21.94±1.52) (p< 0.64), although the differences were not statistically significant; similar results were for mGCL (affected eyes-38.26±7.14, unaffected eyes-49.23±4.9 versus controls-53.81±6.28, p<0.59). Although GMF was lower in patients compared with controls (0.48±0.02 versus 0.50±0.03, p< 0.06), no significant correlations were found between GMF and mRNFL or mGCL. Conclusion: There is a suggestion for axonal and retinal ganglion cell loss in macular volumes in affected and unaffected eyes of CIS patients, which we hope to confirm by recruiting a larger sample of patients. Disclosure: Dr. Collorone has nothing to disclose. Dr. Cawley has nothing to disclose. Dr. Miller has nothing to disclose. Dr. Toosy has received personal compensation for activities with Biogen Idec. Dr. Ciccarelli has received personal compensation for activities with Novartis, Biogen and GE as a consultant.