Voice and General Fatigue in Multiple Sclerosis: A Comparative Study with Healthy Individuals
Yıl 2026,
Cilt: 11 Sayı: 1, 179 - 184, 28.01.2026
Emel Arslan-sarımehmetoğlu
,
Kübra Tekin
Öz
Objective: The purpose of this study was to compare the levels of vocal fatigue and general fatigue in multiple sclerosis (MS) patients without voice disorders with those of healthy individuals, and to evaluate the relationship between vocal fatigue and general fatigue within the MS group.
Material and Methods: The study was conducted using a comparative descriptive design. The sample consisted of 25 individuals diagnosed with MS according to the McDonald criteria and 25 healthy controls matched for age and gender. The mean age of the MS group was 38.12 years (min = 21, max = 62), while the control group had a mean age of 35.79 years (min = 20, max = 56). In the MS group, 88% were female and 12% were male, whereas in the control group 76% were female and 24% were male. Data were collected online using the Descriptive Information Form, the Voice Handicap Index–30 (VHI), the Fatigue Assessment Scale (FAS), and the Vocal Fatigue Index (VFI).
Results: The MS group had significantly higher levels of general fatigue compared to the control group (p < 0.001). Similarly, the MS group scored significantly higher on vocal fatigue total (p = 0.001), the fatigue and avoidance subscale (p < 0.001), and the physical discomfort subscale (p = 0.019) than the control group.
Conclusion: In this study, it was found that individuals with MS without voice disorders had significantly higher general and voice-related fatigue than healthy individuals. The observation that overall and vocal fatigue levels are higher in MS patients at an independent functioning level, even before the onset of overt dysphonia, suggests that these symptoms may develop from the early stages of the disease. Systematic assessment of voice parameters during the clinical follow-up of patients with MS may contribute to research on the disease and guide the development of early intervention strategies.
Etik Beyan
Before the research, approval was obtained from the Non-Interventional Clinical Research Ethics Committee of Ankara Medipol University (Decision No: 128, Date: 01.07.2025). Participants were informed about the purpose of the study, the principles of voluntary participation, and the confidentiality of personal data; informed consent forms were obtained electronically from each individual in an online environment. The study process was conducted in accordance with the Declaration of Helsinki.
Destekleyen Kurum
Ankara Medipol University
Proje Numarası
E-85859696-604.01.01-4657
Teşekkür
We would like to express our gratitude to the Non-Interventional Clinical Research Ethics Committee of Ankara Medipol University for their contribution to the realization of this study. We also extend our sincere thanks to all individuals who voluntarily participated in the study for their valuable contributions.
Kaynakça
-
1. Correale J, Gaitán MI, Ysrraelit MC, Fiol MP. Progressive multiple sclerosis: from pathogenic mechanisms to treatment. Brain. 2017;140 (3):527-46. DOI: 10.1093/brain/aww258.
-
2. Sonkaya ZZ, Özturk B, Sonkaya R, Taskiran E, Karadas Ö. Using objective speech analysis techniques for the clinical diagnosis and assessment of speech disorders in patients with multiple sclerosis. Brain Sci. 2024;14(4):384. DOI: 10.3390/brainsci14040384.
-
3. Dobson R, Giovannoni G. Multiple sclerosis–a review. Eur J Neurol. 2019;26(1):27-40. DOI: 10.1111/ene.13819.
-
4. Braley TJ, Chervin RD. Fatigue in multiple sclerosis: mechanisms, evaluation, and treatment. Sleep. 2010;33(8):1061-7. DOI: 10.1093/sleep/33.8.1061.
-
5. Kurtzke JF. Rating neurologic impairment in multiple sclerosis: an expanded disability status scale (EDSS). Neurology. 1983;33(11):1444. DOI: 10.1212/WNL.33.11.1444.
-
6. Meyer-Moock S, Feng YS, Maeurer M, Dippel FW, Kohlmann T. Systematic literature review and validity evaluation of the Expanded Disability Status Scale (EDSS) and the Multiple Sclerosis Functional Composite (MSFC) in patients with multiple sclerosis. BMC Neurol. 2014;14:58. DOI: 10.1186/1471-2377-14-58.
-
7. Bailey A, Channon S, Beaumont JG. The relationship between subjective fatigue and cognitive fatigue in advanced multiple sclerosis. Mult Scler J. 2007;13(1):73-80. DOI: 10.1177/1352458506071162.
-
8. Bayazıt ZZ, Sonkaya AR. Multipl Skleroz erken tanısında ses analizi yönteminin kullanılabilirliğinin incelenmesi. Online Turk J Health Sci. 2019;4(4):413-27. DOI: 10.26453/otjhs.479261.
-
9. Bauer V, Aleric Z, Jancic E. Comparing voice self-assessment with auditory perceptual analysis in patients with multiple sclerosis. Int Arch Otorhinolaryngol. 2015;19(2):100-5. DOI: 10.1055/s-0034-1397332.
-
10. Rusz J, Benova B, Ruzickova H, Novotny M, Tykalova T, Hlavnicka J, et al. Characteristics of motor speech phenotypes in multiple sclerosis. Mult Scler Relat Disord. 2018;19:62-9. DOI: 10.1016/j.msard.2017.11.007.
-
11. Sataloff RT, Mandel S, Rosen DC. Neurologic disorders affecting the voice in performance. In: Sataloff RT, editor. The professional voice: the science and art of clinical care. 2nd ed. San Diego (CA): Singular Publishing Group; 1997. p. 479-98. DOI: 10.1007/978-3-031-97751-0.
-
12. Hartelius L, Svensson P. Speech and swallowing symptoms associated with Parkinson's disease and multiple sclerosis: a survey. Folia Phoniatr Logop. 1994;46(1):9-17. DOI:10.1159/000266286.
-
13. Feijo AV, Parente MA, Behlau M, Haussen S, et al. Acoustic analysis of voice in multiple sclerosis patients. J Voice. 2004;18(3):341-7. DOI:10.1016/j.jvoice.2003.05.004.
-
14. Yamout B, Fuleihan N, Hajj T, Sibai A, Sabra O, Rifai H, et al. Vocal symptoms and acoustic changes in relation to the expanded disability status scale, duration and stage of disease in patients with multiple sclerosis. Eur Arch Otorhinolaryngol. 2009;266(11):1759-65. DOI:10.1007/s00405-009-1003-y.
-
15. Heine M, van de Port I, Rietberg MB, van Wegen EE, Kwakkel G. Exercise therapy for fatigue in multiple sclerosis. Cochrane Database Syst Rev. 2015;(9)\:CD009956. DOI: 10.1002/14651858.CD009956.pub2.
-
16. Dogan M, Midi I, Yazıcı MA, Kocak I, Günal D, Sehitoglu MA. Objective and subjective evaluation of voice quality in multiple sclerosis. J Voice. 2007;21(6):735-40. DOI: 10.1016/j.jvoice.2006.05.006.
-
17. Santiago RDS, Araújo JMC, Nascimento MHC, Anhoque CF, Neves AT, Depolli GT, et al. Voice handicap, vocal fatigue, and voice-related quality of life in patients with multiple sclerosis. CoDAS. 2025;37\:e20230320. DOI: 10.1590/2317-1782/e20230320pt.
-
18. Kreiman, J., & Gerratt, B. R. (2000). Sources of listener disagreement in voice quality assessment. J Acoust Soc Am, 108, 1867-1876. DOI: 10.1121/1.1289362.
-
19. Fujiki RB, Thibeault SL. Examining relationships between GRBAS ratings and acoustic, aerodynamic and patient-reported voice measures in adults with voice disorders. J Voice. 2023;37(3):390-7. DOI: 10.1016/j.jvoice.2021.02.007.
-
20. Şirin S, Öğüt MF, Bilgen C. Reliability and validity of the Turkish version of the Vocal Fatigue Index. Turk J Med Sci. 2020;50(4):902-9. DOI: 10.3906/sag-1908-105.
-
21. Tezcaner, Z. Ç., & Aksoy, S. Reliability and validity of the Turkish version of the voice-related quality of life measure. J Voice, 2017;31(2),262-e7. DOI: 10.1016/j.jvoice.2016.04.012.
-
22. Arslan-Sarımehmetoğlu, E., Tuaç, Y., & Çınar, R. (2024). Reliability and validity of the Turkish version of the Screening Index for Voice Disorder (SIVD-TR). J Voice. DOI: 10.1016/j.jvoice.2024.07.021.
-
23. Shao J, MacCallum JK, Zhang Y, Sprecher A, Jiang JJ. Acoustic analysis of the tremulous voice: assessing the utility of the correlation dimension and perturbation parameters. J Commun Disord. 2010;43(1):35-44. DOI: 10.1016/j.jcomdis.2009.09.001.
-
24. Fantoni A. Assessment of vocal fatigue of multiple sclerosis patients. Validation of a contact microphone-based device for long-term monitoring \[doctoral dissertation]. Torino: Politecnico di Torino; 2023. DOI: 10.5281/zenodo.1234567.
-
25. Songur ET, Hafizoğlu M, Aydinli FE, İncebay Ö, Parlak MM, Balci C. Analysis of the auditory-perceptual voice quality in older and younger adults without self-reported voice complaints. J Voice. 2025;39(1)\:xxx-xxx. DOI: 10.1016/j.jvoice.2024.12.022.
-
26. Dias M, Dörr F, Garthof S, Schäfer S, Elmers J, Schwed L, et al. Detecting fatigue in multiple sclerosis through automatic speech analysis. Front Hum Neurosci. 2024;18:1449388. DOI: 10.3389/fnhum.2024.1449388.
-
27. Jacobson BH, Johnson A, Grywalski C, Silbergleit A, Jacobson G, Benninger MS, et al. The voice handicap index (VHI) development and validation. Am J Speech Lang Pathol. 1997;6(3):66-70. DOI: 10.1044/1058-0360.0603.66.
-
28. Kılıç MA, Okur E, Yıldırım İ, Öğüt F, Denizoğlu İİ, Kızılay A, et al. Ses handikap endeksi voice handicap index Türkçe versiyonunun güvenilirliği ve geçerliliği. Turk J Ear Nose Throat. 2008;18(3):139-47. DOI: 10.16919/kbbihtisas.2023.1124908.
-
29. De Vries J, Michielsen H, Van Heck GL, Drent M. Measuring fatigue in sarcoidosis: the fatigue assessment scale (FAS). Br J Health Psychol. 2004;9(3):279-91. DOI: 10.1348/1359107041557048.
-
30. Ozkeskin M, Özden F, Yüceyar N. The reliability and validity of the Turkish version of the fatigue assessment scale in patients with multiple sclerosis. Neurol Sci Neurophysiol. 2022;39(2):109-14. DOI: 10.5152/nsn.2022.39020.
-
31. Nanjundeswaran C, Jacobson BH, Gartner-Schmidt J, Abbott KV. Vocal fatigue index (VFI): development and validation. J Voice. 2015;29(4):433-40. DOI: 10.1016/j.jvoice.2014.09.012.
-
32. Penner IK, Paul F. Fatigue as a symptom or comorbidity of neurological diseases. Nat Rev Neurol. 2017;13(11):662-75. DOI: 10.1038/nrneurol.2017.117.
-
33. Blaney, B. E., & Lowe-Strong, A. (2009). The impact of fatigue on communication in multiple sclerosis. The insider's perspective. Disabil Rehabil, 31(3), 170-180. DOI: 10.1080/09638280802060716.
-
34. Freal J E, Kraft G H, Coryell J K. Symptomatic fatigue in multiple sclerosis. Arch Phys Med Rehabil 1984; 65: 135–138 DOI: 10.1016/S0003-9993(84)80004-1.
-
35. Natour, Y., Marie, B., & Aljunidy, L. (2012). The respiratory muscle capabilities of Jordanian patients with multiple sclerosis. J Voice, 26(6), 811-e15. DOI: 10.1016/j.jvoice.2012.02.009.
-
36. Sarımehmetoğlu, E. A., & Barmak, E. (2024). Examination of voice perception and voice fatigue in call center employees. J Voice. DOI: 10.1016/j.jvoice.2024.01.011.
-
37. Crispiatico V, Baldanzi C, Bertuletti M, Grassi S, Tedeschi F, Groppo E, et al. Factors associated with treatment-related changes in voice volume in people with multiple sclerosis. Int J MS Care. 2023;25(1):1-7. DOI: 10.7224/1537-2073.2021-056.
Multipl Skleroz Hastalığında Ses ve Genel Yorgunluk: Sağlıklı Bireylerle Karşılaştırmalı Bir İnceleme
Yıl 2026,
Cilt: 11 Sayı: 1, 179 - 184, 28.01.2026
Emel Arslan-sarımehmetoğlu
,
Kübra Tekin
Öz
Amaç: Bu çalışmanın amacı, ses bozukluğu olmayan multipl skleroz (MS) hastalarında ses yorgunluğu ve genel yorgunluk düzeylerini sağlıklı bireylerle karşılaştırmak, MS grubunda ses yorgunluğunun genel yorgunluk ile ilişkisini değerlendirmek amaçlanmıştır.
Gereç ve Yöntem: Çalışma, karşılaştırmalı tanımlayıcı desenle yürütülmüştür. Araştırmaya McDonald kriterlerine göre MS tanısı almış 25 birey ve yaş ile cinsiyet açısından benzer özellikler gösteren 25 sağlıklı birey katılmıştır. Katılımcıların yaş ortalaması çalışma grubunda 38,12 (min = 21, maks = 62), kontrol grubunda ise 35,79 (min = 20, maks = 56) olarak bulunmuştur. Çalışma grubunun %88’i kadın, %12’si erkek; kontrol grubunun ise %76’sı kadın, %24’ü erkektir. Veriler; Tanımlayıcı Bilgi Formu, Ses Handikap Endeksi–30 (SHE), Yorgunluk Değerlendirme Ölçeği (FAS-TR) ve Ses Yorgunluğu Ölçeği (SYÖ) aracılığıyla çevrimiçi olarak toplanmıştır.
Bulgular: Çalışma grubunda genel yorgunluk düzeyi kontrol grubuna kıyasla anlamlı düzeyde daha yüksek bulunmuştur (p < 0,001). Benzer şekilde, ses yorgunluğu toplam puanı (p = 0,001), yorgunluk ve kaçınma alt boyutu (p < 0,001) ve fiziksel rahatsızlık alt boyutu (p = 0,019) çalışma grubunda kontrol grubuna göre anlamlı düzeyde yüksek bulunmuştur.
Sonuç: Bu çalışmada ses bozukluğu olmayan MS tanılı bireylerin genel ve sesle ilişkili yorgunluğun sağlıklı bireylere göre daha belirgin düzeyde yüksek olduğu bulunmuştur. Belirgin bir disfoni ortaya çıkmadan, MS hastalarında bağımsızlık düzeyindeyken genel ve ses yorgunluğunun daha yüksek seviyelerde gözlemlenmesi, bu semptomların hastalığın erken evrelerinden itibaren gelişebileceğini düşündürmüştür. MS hastalarının klinik izlem sürecinde ses alanında sistematik değerlendirmelerin yapılmasının, hastalığa ilişkin araştırmalara katkı sağlayabileceği ve erken müdahale yaklaşımlarının geliştirilmesine yön verebileceği düşünülmektedir.
Etik Beyan
Araştırma öncesinde Ankara Medipol Üniversitesi Girişimsel Olmayan Klinik Araştırmalar Etik Kurulu’ndan onay alınmıştır (Karar No: 128, Tarih: 01.07.2025). Katılımcılara çalışmanın amacı, gönüllü katılım esasları ve kişisel verilerin gizliliği hakkında bilgilendirme yapılmış; her bireyden aydınlatılmış onam formu çevrimiçi ortamda elektronik olarak alınmıştır. Çalışma sürecinde Helsinki Bildirgesine uygun hareket edilmiştir.
Destekleyen Kurum
Ankara Medipol Üniversitesi
Proje Numarası
E-85859696-604.01.01-4657
Teşekkür
Çalışmamızın gerçekleştirilmesine katkı sağlayan Ankara Medipol Üniversitesi Girişimsel Olmayan Klinik Araştırmalar Etik Kurulu’na teşekkür ederiz. Ayrıca çalışmaya gönüllü olarak katılan tüm bireylere değerli katkıları için şükranlarımızı sunarız.
Kaynakça
-
1. Correale J, Gaitán MI, Ysrraelit MC, Fiol MP. Progressive multiple sclerosis: from pathogenic mechanisms to treatment. Brain. 2017;140 (3):527-46. DOI: 10.1093/brain/aww258.
-
2. Sonkaya ZZ, Özturk B, Sonkaya R, Taskiran E, Karadas Ö. Using objective speech analysis techniques for the clinical diagnosis and assessment of speech disorders in patients with multiple sclerosis. Brain Sci. 2024;14(4):384. DOI: 10.3390/brainsci14040384.
-
3. Dobson R, Giovannoni G. Multiple sclerosis–a review. Eur J Neurol. 2019;26(1):27-40. DOI: 10.1111/ene.13819.
-
4. Braley TJ, Chervin RD. Fatigue in multiple sclerosis: mechanisms, evaluation, and treatment. Sleep. 2010;33(8):1061-7. DOI: 10.1093/sleep/33.8.1061.
-
5. Kurtzke JF. Rating neurologic impairment in multiple sclerosis: an expanded disability status scale (EDSS). Neurology. 1983;33(11):1444. DOI: 10.1212/WNL.33.11.1444.
-
6. Meyer-Moock S, Feng YS, Maeurer M, Dippel FW, Kohlmann T. Systematic literature review and validity evaluation of the Expanded Disability Status Scale (EDSS) and the Multiple Sclerosis Functional Composite (MSFC) in patients with multiple sclerosis. BMC Neurol. 2014;14:58. DOI: 10.1186/1471-2377-14-58.
-
7. Bailey A, Channon S, Beaumont JG. The relationship between subjective fatigue and cognitive fatigue in advanced multiple sclerosis. Mult Scler J. 2007;13(1):73-80. DOI: 10.1177/1352458506071162.
-
8. Bayazıt ZZ, Sonkaya AR. Multipl Skleroz erken tanısında ses analizi yönteminin kullanılabilirliğinin incelenmesi. Online Turk J Health Sci. 2019;4(4):413-27. DOI: 10.26453/otjhs.479261.
-
9. Bauer V, Aleric Z, Jancic E. Comparing voice self-assessment with auditory perceptual analysis in patients with multiple sclerosis. Int Arch Otorhinolaryngol. 2015;19(2):100-5. DOI: 10.1055/s-0034-1397332.
-
10. Rusz J, Benova B, Ruzickova H, Novotny M, Tykalova T, Hlavnicka J, et al. Characteristics of motor speech phenotypes in multiple sclerosis. Mult Scler Relat Disord. 2018;19:62-9. DOI: 10.1016/j.msard.2017.11.007.
-
11. Sataloff RT, Mandel S, Rosen DC. Neurologic disorders affecting the voice in performance. In: Sataloff RT, editor. The professional voice: the science and art of clinical care. 2nd ed. San Diego (CA): Singular Publishing Group; 1997. p. 479-98. DOI: 10.1007/978-3-031-97751-0.
-
12. Hartelius L, Svensson P. Speech and swallowing symptoms associated with Parkinson's disease and multiple sclerosis: a survey. Folia Phoniatr Logop. 1994;46(1):9-17. DOI:10.1159/000266286.
-
13. Feijo AV, Parente MA, Behlau M, Haussen S, et al. Acoustic analysis of voice in multiple sclerosis patients. J Voice. 2004;18(3):341-7. DOI:10.1016/j.jvoice.2003.05.004.
-
14. Yamout B, Fuleihan N, Hajj T, Sibai A, Sabra O, Rifai H, et al. Vocal symptoms and acoustic changes in relation to the expanded disability status scale, duration and stage of disease in patients with multiple sclerosis. Eur Arch Otorhinolaryngol. 2009;266(11):1759-65. DOI:10.1007/s00405-009-1003-y.
-
15. Heine M, van de Port I, Rietberg MB, van Wegen EE, Kwakkel G. Exercise therapy for fatigue in multiple sclerosis. Cochrane Database Syst Rev. 2015;(9)\:CD009956. DOI: 10.1002/14651858.CD009956.pub2.
-
16. Dogan M, Midi I, Yazıcı MA, Kocak I, Günal D, Sehitoglu MA. Objective and subjective evaluation of voice quality in multiple sclerosis. J Voice. 2007;21(6):735-40. DOI: 10.1016/j.jvoice.2006.05.006.
-
17. Santiago RDS, Araújo JMC, Nascimento MHC, Anhoque CF, Neves AT, Depolli GT, et al. Voice handicap, vocal fatigue, and voice-related quality of life in patients with multiple sclerosis. CoDAS. 2025;37\:e20230320. DOI: 10.1590/2317-1782/e20230320pt.
-
18. Kreiman, J., & Gerratt, B. R. (2000). Sources of listener disagreement in voice quality assessment. J Acoust Soc Am, 108, 1867-1876. DOI: 10.1121/1.1289362.
-
19. Fujiki RB, Thibeault SL. Examining relationships between GRBAS ratings and acoustic, aerodynamic and patient-reported voice measures in adults with voice disorders. J Voice. 2023;37(3):390-7. DOI: 10.1016/j.jvoice.2021.02.007.
-
20. Şirin S, Öğüt MF, Bilgen C. Reliability and validity of the Turkish version of the Vocal Fatigue Index. Turk J Med Sci. 2020;50(4):902-9. DOI: 10.3906/sag-1908-105.
-
21. Tezcaner, Z. Ç., & Aksoy, S. Reliability and validity of the Turkish version of the voice-related quality of life measure. J Voice, 2017;31(2),262-e7. DOI: 10.1016/j.jvoice.2016.04.012.
-
22. Arslan-Sarımehmetoğlu, E., Tuaç, Y., & Çınar, R. (2024). Reliability and validity of the Turkish version of the Screening Index for Voice Disorder (SIVD-TR). J Voice. DOI: 10.1016/j.jvoice.2024.07.021.
-
23. Shao J, MacCallum JK, Zhang Y, Sprecher A, Jiang JJ. Acoustic analysis of the tremulous voice: assessing the utility of the correlation dimension and perturbation parameters. J Commun Disord. 2010;43(1):35-44. DOI: 10.1016/j.jcomdis.2009.09.001.
-
24. Fantoni A. Assessment of vocal fatigue of multiple sclerosis patients. Validation of a contact microphone-based device for long-term monitoring \[doctoral dissertation]. Torino: Politecnico di Torino; 2023. DOI: 10.5281/zenodo.1234567.
-
25. Songur ET, Hafizoğlu M, Aydinli FE, İncebay Ö, Parlak MM, Balci C. Analysis of the auditory-perceptual voice quality in older and younger adults without self-reported voice complaints. J Voice. 2025;39(1)\:xxx-xxx. DOI: 10.1016/j.jvoice.2024.12.022.
-
26. Dias M, Dörr F, Garthof S, Schäfer S, Elmers J, Schwed L, et al. Detecting fatigue in multiple sclerosis through automatic speech analysis. Front Hum Neurosci. 2024;18:1449388. DOI: 10.3389/fnhum.2024.1449388.
-
27. Jacobson BH, Johnson A, Grywalski C, Silbergleit A, Jacobson G, Benninger MS, et al. The voice handicap index (VHI) development and validation. Am J Speech Lang Pathol. 1997;6(3):66-70. DOI: 10.1044/1058-0360.0603.66.
-
28. Kılıç MA, Okur E, Yıldırım İ, Öğüt F, Denizoğlu İİ, Kızılay A, et al. Ses handikap endeksi voice handicap index Türkçe versiyonunun güvenilirliği ve geçerliliği. Turk J Ear Nose Throat. 2008;18(3):139-47. DOI: 10.16919/kbbihtisas.2023.1124908.
-
29. De Vries J, Michielsen H, Van Heck GL, Drent M. Measuring fatigue in sarcoidosis: the fatigue assessment scale (FAS). Br J Health Psychol. 2004;9(3):279-91. DOI: 10.1348/1359107041557048.
-
30. Ozkeskin M, Özden F, Yüceyar N. The reliability and validity of the Turkish version of the fatigue assessment scale in patients with multiple sclerosis. Neurol Sci Neurophysiol. 2022;39(2):109-14. DOI: 10.5152/nsn.2022.39020.
-
31. Nanjundeswaran C, Jacobson BH, Gartner-Schmidt J, Abbott KV. Vocal fatigue index (VFI): development and validation. J Voice. 2015;29(4):433-40. DOI: 10.1016/j.jvoice.2014.09.012.
-
32. Penner IK, Paul F. Fatigue as a symptom or comorbidity of neurological diseases. Nat Rev Neurol. 2017;13(11):662-75. DOI: 10.1038/nrneurol.2017.117.
-
33. Blaney, B. E., & Lowe-Strong, A. (2009). The impact of fatigue on communication in multiple sclerosis. The insider's perspective. Disabil Rehabil, 31(3), 170-180. DOI: 10.1080/09638280802060716.
-
34. Freal J E, Kraft G H, Coryell J K. Symptomatic fatigue in multiple sclerosis. Arch Phys Med Rehabil 1984; 65: 135–138 DOI: 10.1016/S0003-9993(84)80004-1.
-
35. Natour, Y., Marie, B., & Aljunidy, L. (2012). The respiratory muscle capabilities of Jordanian patients with multiple sclerosis. J Voice, 26(6), 811-e15. DOI: 10.1016/j.jvoice.2012.02.009.
-
36. Sarımehmetoğlu, E. A., & Barmak, E. (2024). Examination of voice perception and voice fatigue in call center employees. J Voice. DOI: 10.1016/j.jvoice.2024.01.011.
-
37. Crispiatico V, Baldanzi C, Bertuletti M, Grassi S, Tedeschi F, Groppo E, et al. Factors associated with treatment-related changes in voice volume in people with multiple sclerosis. Int J MS Care. 2023;25(1):1-7. DOI: 10.7224/1537-2073.2021-056.