Research Article Sound Lateralization Test Distinguishes Unimpaired MS Patients from Healthy Controls Joshua H. Bacon, 1,2 Ilya Kister, 2 Tamar E. Bacon, 2 Eliana Pasternak, 1 Yael Strauchler, 1 and Joseph Herbert 2 1 Department of Psychology, Stern College for Women, Yeshiva University, 215 Lexington Avenue, New York, NY 10016, USA 2 NYU Multiple Sclerosis Care Center, Department of Neurology, NYU School of Medicine, 240 E38th Street, New York, NY 10016, USA Correspondence should be addressed to Joshua H. Bacon; baconj01@gmail.com Received 5 March 2014; Revised 18 June 2014; Accepted 19 June 2014; Published 15 July 2014 Academic Editor: Matilde Inglese Copyright © 2014 Joshua H. Bacon et al. Tis is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Tere is an urgent need to develop a practical and reliable clinical measure of disease progression in early and mild MS. We hypothesized that a test of sound lateralization, which is exquisitely sensitive to transmission delays in auditory brainstem, could be more useful for detecting processing speed defcits in mildly impaired MS subjects than standard cognitive tasks. Objective. To develop a practical test of sound lateralization for the clinic and to compare performance of MS subjects with variable disability and healthy subjects on Sound Lateralization Test (SLT) and two speed-of-processing tasks. Design. 42 healthy controls and 90 subjects with clinically defnite MS, divided into no, mild, and moderate disability strata, were administered the Symbol Digit Modalities Test (SDMT), and 3-second Paced Auditory Serial Addition Test (PASAT). Results. All of the tests showed an overall diference in performance between controls and the three MS groups, but only the SLT measured a signifcant diference between controls and the no disability group. Conclusion. SLT is rapidly applied, technically simple, and superior to standard processing speed tests for discriminating between healthy controls and nondisabled MS subjects. SLT should be investigated as an outcome measure in early-phase trials and for monitoring early disease progression in the clinic. 1. Introduction Tere are two main reasons to develop tests for quantifying neurologic defcits in minimally or mildly impaired MS patients. Te “gold standard” measure of MS disability, Expanded Disability Status Scale (EDSS), is unreliable in the low range [1] and sufers from a number of well-known methodological limitations [2]. Patients with “stable” low EDSS scores ofen exhibit increasing functional limitations and radiographic disease progression. By the time neurologic defcits become overt, patients may already have reached EDSS score of 3 or more and entered an irreversible phase of the disease, with a relatively fxed time course to moderate-to- severe disability milestones [3]. For clinical decision making it would be most important to have a reliable, objective measure of disease progression in the early phase of MS, when patients may still be within the “window of opportunity” and an intervention could be of greatest beneft [4, 5]. Secondly, there are no accepted clinical outcome mea- sures for monitoring treatment efects of potentially neu- roprotective or restorative agents in phase I or II studies. Smaller-scale studies rely on MRI metrics, such as T1 and T2 lesion burden, whose validity as an outcome measure in MS has been called into question [6]. A clinical measure capable of detecting progression of defcits in mild disease could be used to decide which investigational agents should be advanced through the therapeutic pipeline. As a candidate for a clinical measure sensitive to changes in early disease, we investigated a test of sound lateral- ization, a measure of speed of processing in the auditory brainstem. We adapted a technically simple, well-established experimental paradigm in which bursts of pure-tone, low- frequency sounds are presented through earphones with variable interaural delay [7]. When two sound bursts of equal intensity are simultaneously presented to both ears through the earphones, the listener perceives a “fused acoustic image” Hindawi Publishing Corporation Multiple Sclerosis International Volume 2014, Article ID 462043, 5 pages http://dx.doi.org/10.1155/2014/462043