34 Abstract Background: Since in multiple sclerosis (MS), changes in speech and voice quality often precede other signs and symptoms; early diagnosis of these changes is necessary. In this study, an acoustic examination of phonation subsystem was performed. Due to the progressive nature of multiple sclerosis, the aim of this study was to examine the correlation between acoustic parameters of voice quality and disease severity and duration. Methods: This descriptive-analytic study was performed on 43 patients with multiple sclerosis. The disease severity was detected by a neurologist based on the Expanded Disability Status Scale (EDSS) for each patient. Acoustic analysis was performed during the production of sustained vowel /a/ and accordingly, the maximum phonation time (MPT), perturbation of the frequency (jitter), perturbation of amplitude (shimmer), the maximum and minimum frequency, and the highest and lowest intensity were evaluated. All the acoustic analyses were performed using PRAAT software. Data were statistically analyzed using Spearman's correlation coefficient by SPSS version 21. Results: The lowest intensity showed a significant correlation with disease severity (P=0.00). Also, the highest and lowest intensity showed a significant correlation with disease duration (P=0.022 and P=0.002). Conclusion: One of the earlier symptoms of central nervous system impairment resulting from multiple sclerosis is changes in phonation subsystem and voice quality. These changes may appear at any clinical stages; however, the symptoms might get worse over time, with the progression of the disease. Therefore, immediate acoustic assessments and interventions can prevent more degradation of voice quality. Copyright: 2018 The Author(s); Published by Kerman University of Medical Sciences. This is an open-access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Citation: Fazeli M, Moradi N, Soltani M, Naderifar E, Majdinasab N, Latifi S.M. Correlation between Acoustic Parameters and Disease Severity and Duration in Patients with Multiple Sclerosis. Journal of Kerman University of Medical Sciences, 2018; 25 (1): 34-43. JKMU Journal of Kerman University of Medical Sciences, 2018; 25 (1): 34-43 Correlation between Acoustic Parameters and Disease Severity and Duration in Patients with Multiple Sclerosis Mahnoosh Fazeli, M.Sc. 1 , Negin Moradi, Ph.D. 2 , Majid Soltani, Ph.D. 3 , Ehsan Naderifar M.Sc. 4 , Nastaran Majdinasab, Ph.D. 5 , Seyed Mahmood Latifi, M.Sc. 6 1- Musculoskeletal Rehabilitation Research Center, Department of Speech Therapy, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran 2- Assistant Professor, Musculoskeletal Rehabilitation Research Center, Department of Speech Therapy, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran (Corresponding author; E-mail: neginmoradist@gmail.com) 3-Assistant Professor, Musculoskeletal Rehabilitation Research Center, Department of Speech Therapy, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran 4-Instructor, Musculoskeletal Rehabilitation Research Center, Department of Speech Therapy, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran 5-Associate Professor, Musculoskeletal Rehabilitation Research Center, Department of Neurology, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran 6- Ph.D. Candidate, Health Research Institute, Diabetes Research Center, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran Received: 24 October, 2017 Accepted: 29 February, 2018 ARTICLE INFO Article type: Original article Keywords: Multiple sclerosis Speech Voice Quality Disease Severity Disease Duration