OCT, Visual Function and MRI Measures in Acute Optic Neuritis: Baseline Data from a Clinical Trial (P2.255)

Objective: To assess whether baseline retinal nerve fibre layer thickness (RNFL) correlates with functional, electrophysiological and imaging measures in acute optic neuritis. Background: The aim of the neuroprotection with phenytoin in acute unilateral optic neuritis trial is to assess whether sodium channel blockade with phenytoin has a neuroprotective effect after acute demyelinating optic neuritis.This analysis is based on baseline data available at this time. Results:At the time data was available for 49 patients with an average age of 35+/-9 years. 38 of these were female (77.6%). The mean RNFL thickness of the affected eye was 126.6µm+/-47.4 compared with 97.8µm+/10.8 in the fellow eye(p=<0.0001).There was no significant difference between the affected and fellow eye total macular volume.The mean logMAR visual acuity of the affected eye was 1.07+/-0.6 with a mean Farnsworth-Munsell(FM)100 hue error score of 695+/-299.Baseline visual evoked potentials(VEPS) were absent in the affected eye of 21(42.9%) patients.For the remainder with recordable VEPs the mean latency was 135.9ms+/-17.87 with a mean amplitude of 6.05 µV+/-3.13. On T2 weighted MRi of the optic nerve the mean distance of the anterior end of lesion from the globe was 12.7mm+/-9.8 and mean lesion length was 18.6 mm+/- 8.2.There was a significant negative correlation between greater RNFL thickness and distance of the lesion from the globe(p=0.04, r= -0.34) and significant correlation between lesion length on MRI and RNFL thickness(p=0.003, r =0.49).There was no significant correlation between visual function and RNFL thickness in the affected eye.RNFL thickness was 16.5µm greater in patients with absent VEPS compared to those with recordable VEPs but this did not reach statistical significance(p= 0.27). Conclusion: In our cohort of acute optic neuritis patients RNFL thickness did not predict visual function or electrophysiological measures at baseline.More anterior and more elongated lesions on MRI were associated with significantly greater RNFL thickness. Study Supported by:National MS society,MS society of GB and NI,NMR research unit, Queen Sqaure MS centre,UCLH comprehensive biomedical research centre,Novartis Disclosure: Dr. Raftopoulos has nothing to disclose. Dr. Hickman has nothing to disclose. Dr. Toosy has nothing to disclose. Dr. Wheeler-Kingshott has received personal compensation for activities with Biogen Idec as an advisory board member. Dr. Altmann has nothing to disclose. Dr. Mallik has nothing to disclose. Dr. Paling has nothing to disclose. Dr. Yiannakas has nothing to disclose. Dr. Schmierer has received personal compensation for activities with Sanofi-Aventis Pharmaceuticals Inc., Novartis and Merck Serono. Dr. Sharrack has nothing to disclose. Dr. Sheridan has nothing to disclose. Dr. Giovannoni has received personal compensation for activities with Biogen Idec, Merck Serono, Vertex Pharmaceuticals, Bayer Schering, Pfizer Inc., Teva Neuroscience, and Sanofi-Aventis Pharmaceuticals Inc. Dr. Giovannoni has received research support from Biogen Idec, Merck Serono, Novartis, and Ironwood. Dr. Miller has received personal compensation for activities with UCL Institute of Neurology, Biogen Idec, GlaxoSmithKline Inc., Novartis, Merck & Co. Inc., Chugai, and Mitsubishi Pharma. Dr. Miller has received personal compensation in an editorial capacity for the Journal of Neurology. Dr. Miller has received research support from Biogen Idec, Schering AG, Apitope, Richmond Pharma, GlaxoSmithKline Inc., and Novartis. Dr. Kapoor has received personal compensation for activities with Merck Serono, Novartis, MS Therapeutics, and Biogen Idec as a consultant.