Dual–Mode (Surgical + Drug) Treatment of Acquired Pendular Nystagmus and Oscillopsia in MS

Abstract

Abstract: : Purpose: To investigate the effects of tenotomy, tenotomy + memantine, and uniocular tenotomy on acquired pendular nystagmus (APN) and intractable oscillopsia in MS. Background: The tenotomy procedure developed on a canine model to damp infantile nystagmus, was successful in a masked clinical trial and hypothesized to improve acquired nystagmus. Methods: Case 1: Both medial rectus muscles were tenotomized and lateral rectus muscles recessed for exotropia correction. Horizontal, vertical, and torsional pre– and post–tenotomy search–coil recordings were made. Fixation, saccades, pursuit, OKR, VOR, and visual acuity were tested. Multiplanar APN was analyzed for eXpanded Nystagmus Acuity Function (NAFX), peak–to–peak velocities, mean speeds, amplitudes, and frequencies. Memantine was then prescribed and the analyses were repeated. Case 2: The horizontal rectus muscles of the affected eye were tenotomized at another center, by a different surgeon. Pre– and post–tenotomy digitized videotapes were analyzed. Results: Case 1's post–tenotomy slow–phase velocities and amplitudes decreased by 38–77.5%; frequencies remained unchanged at 3.7 Hz. Biplanar NAFX values increased by 34% and visual acuities increased from 0.125 to 0.25 (100%). Voluntary saccades and abducting saccadic pulses, secondary to bilateral INO, were unaffected. Memantine + tenotomy further damped the nystagmus by 69% and increased the biplanar NAFX by 9%; visual acuity increased to 0.4 (60%). The cumulative improvements in nystagmus, NAFX, and acuity were 82%, 46%, and 220% respectively. The patient estimated an oscillopsia reduction of 75%. Case 2's APN was reduced by 66%, acuity increased from 0.2 to 0.4 (100%), and oscillopsia was "greatly reduced." Conclusions: Four–muscle tenotomy reduced APN and oscillopsia in MS, increasing acuity. This is consistent with its hypothesized peripheral, small–signal gain reduction via proprioceptive tension control. Memantine further reduced APN centrally, demonstrating the power of dual–mode (surgery + drug) therapy. The NAFX estimated measured acuity improvements for both therapies. Two–muscle tenotomy of the affected eye reduced uniocular APN.

Keywords: nystagmus • ocular motor control