Memantine for axonal loss of optic neuritis

To determine the effect of memantine on axonal loss and visual function during the course of optic neuritis (ON).

Sixty ON patients in a single-center, institutional setting were randomly assigned to the memantine or placebo groups. Patients with first attack of acute unilateral optic neuritis, with visual symptoms of 8 days' duration or less were enrolled in this trial. No patient had known multiple sclerosis, and none had taken immunomodulatory agent prior to or at the time of presentation. For all patients, the following characteristics were recorded and compared at initial presentation and 3 months afterward: visual acuity, retinal nerve fiber layer (RNFL) thickness, visual field parameters (mean deviation and pattern standard deviation), visual evoked potential, and contrast sensitivity.

Fifty-four patients completed the 3-month follow up. There were no significant differences between the placebo and memantine groups for any of the characteristics at initial presentation. After 3 months, the only statistically significant difference between the two groups was in RNFL thickness. Memantine group subjects had higher thickness in nasal (P = 0.01), superior (P = 0.006), inferior (P = 0.01) quadrants and average (P = 0.01). However, temporal quadrant thickness was not different between two groups (P = 0.35).

Memantine was effective in reduction of RNFL thinning, although this structural difference was not associated with improved visual function.