Demyelination and Neurodegeneration along the Visual Pathway are more prominent in Secondary Progressive than Primary Progressive Multiple Sclerosis. (P2.391)

Objective: We aimed at using visual evoked potentials-VEPs and optical coherence tomography-OCT to compare the extent of demyelination and neurodegeneration in the visual pathway of primary progressive-PP and secondary progressive-SP MS patients. Background: The pathophysiologic distinction between PP and SPMS is still debated. Design/Methods: One hundred progressive MS patients (55 SP: disease duration-DD 20.1±7.6 years, median EDSS 6.0; 45 PP: DD 8.4±4.7 years, median EDSS 6.0) and 42 healthy controls-HC underwent testing with high-contrast visual acuity-VA, low contrast letter acuity-LCLA, full-field pattern-reversal VEPs and peripapillary RNFL measurement with OCT. Results: After excluding eyes with previous optic neuritis-ON (unilateral in 18 SP and 2 PP, bilateral in 7 SP), VA did not significantly differ between SP and PP (HCVA 0.88±0.2 vs 0.94±0.2 decimal, p=0.424) and was significantly reduced than in HC (1.03±0.2, p vs PP (0.29±0.2, p=0.015) and vs HC (0.31±0.1, p vs PP (88.7±9.9 μm, p=0.002), and in both subgroups vs HC (96.9±5.7 μm, p vs 26.1% (23/88) PP eyes (p vs PP (132.9±19.3 msec, p=0.003), and in both vs HC (116.2±5.2 msec, p vs 61.3% (54/88) PP eyes (p=0.020). Conclusions: Despite similar global disability, SP patients have greater visual impairment, demyelination and neurodegeneration along the visual pathway compared with PP. These aspects may reflect distinct pathophysiologic processes between the two courses of the disease. Study Supported by: Part of this work was supported by Merck Serono S.A., Geneva, Switzerland. Merck Serono is the biopharmaceutical division of Merck KGaA, Darmstadt, Germany Disclosure: Dr. Guerrieri has nothing to disclose. Dr. pisa has nothing to disclose. Dr. Di Maggio has nothing to disclose. Dr. Moiola has received personal compensation for consulting, serving on a scientific advisory board, speaking, or other activities with Sanofi-Genzyme, Novartis, Teva, Merck-Serono, Biogen, Roche, Excemed. Dr. Martinelli has nothing to disclose. Dr. Comi has nothing to disclose. Dr. Leocani has nothing to disclose.