The Laryngoscope C 2015 The American Laryngological, V
Rhinological and Otological Society, Inc.
Aging Voice and the Laryngeal Muscle Atrophy Regina Helena Garcia Martins, MD, PhD; Adriana Bueno Benito Pessin, PhD; Douglas Jorge Nassib; Anete Branco, PhD; Sergio Augusto Rodrigues, PhD; Selma Maria Michelim Matheus, PhD Objectives/Hypothesis: To study by means of morphometric measurements the severity of vocal muscle atrophy in the elderly. Study Design: Cadaver study. Setting: Universidade Estadual Paulista (UNESP), Botucatu Medical School, Brazil. Subjects and Methods: Thirty vocal folds were collected from necropsies distributed into three groups: aged 60 to 75 years (n 5 10); aged 76 to 90 years (n 5 10); and a control group aged 30 to 50 years (n 5 10). Specimens for histology were obtained from the middle portion of the vocal folds. The stained specimens were analyzed using Axion Vision software (coupled to a Zeiss [Oberkochen, Germany] microscope) and used in the morphometric analyses conducted with the ImageJ software. The diameters of 200 muscle fibers from each slide were measured, and the mean values were statistically analyzed. Results: The mean values of the diameters of the vocal muscle fibers of the elderly age groups were smaller than in the control: control (30–50 years: 16.389 lm); elderly (60–75 years: 14.412 lm; 76–90 years: 14.162 lm) (P < 0.01). No statistical differences were observed between genders. Conclusion: The morphometric analysis showed smaller diameters of vocal muscle fibers in the elderly when compared to controls, demonstrating the atrophy of the muscle. No statistical differences were observed between genders. Key Words: Larynx, voice, vocal muscle, presbyphonia, morphometry. Level of Evidence: N/A. Laryngoscope, 125:2518–2521, 2015
INTRODUCTION Presbyphonia refers to the process of voice aging. The etiology is multifactorial, including natural anatomical and physiological changes. A systematic review of the prevalence of voice disorders in subjects older than 60 years included only four articles, which identified vocal disorders in 4.8% to 29.1% of such individuals.1 The common symptoms of presbyphonia in the elderly population are poor vocal projection, reduced loudness, hoarseness, lowered pitch in women and raised pitch in men, decreased duration of phonation, tremor, and breathiness.2–4 Videolaryngoscopy in the elderly show atrophic, bowed vocal folds; salivary stasis; prominence of the From the Department of Ophthalmology, Otolaryngology and Head and Neck Surgery, Botucatu Medical School, UNESP–Univ Estadual Paulista (R.H.G.M.); the Department of Otolaryngology, Botucatu Medical ao Paulo School, UNESP–Univ Estadual Paulista (A.B.B.P., A.B., D.J.N.); S~ State Technological College/FATEC (S.A.R.), Botucatu; and the Department of Anatomy, Institute of Bioscience–UNESP (S.M.M.M.), Univ Estadual Paulista, Botucatu, SP, Brazil. Editor’s Note: This Manuscript was accepted for publication April 30, 2015. This work was funded by S~ ao Paulo Research Foundation (FAPESP) for the preparation of the histological samples. The authors have no other funding, financial relationships, or conflicts of interest to disclose. Send correspondence to Dr. Regina H. G. Martins, Department of Ophthalmology, Otorhinolaryngology and Head and Neck Surgery, Botucatu Medical School–Universidade Estadual Paulista, Distrito de Rubi~ ao Junior s/n, 18618-970, Botucatu-SP, Brazil. E-mail: [email protected]. br DOI: 10.1002/lary.25398
Laryngoscope 125: November 2015
2518
vocal apophysis; and pseudosulcus. Such vocal changes result from alterations involving all of the structures of the larynx, including calcification of the hyaline cartilages; decreased mucosal secretions; decreased neuromotor control; mucosal atrophy; changes in the components of the lamina propria, such as an increased number of collagen fibers and a decreased elastic fibers and hyaluronic acid; and muscle atrophy.5,6 In the larynx of adults, there is a higher concentration of elastin in the superficial layers of the lamina propria. Collagen fibers are more abundant in intermediate and deeper layers. In the elderly, the atrophy of the vocal folds results from the scarcity of elastic fibers and hyaluronic acid, as well as from atrophy of the vocal muscle.6 When the vocal muscle becomes atrophic, power and vocal intensity decrease, affecting vocal performance. These symptoms are very relevant for some older people, especially those who stay active in their profession. Therefore, this study intends to examine the degree of atrophy of the vocal muscle in the elderly larynx.
SUBJECTS AND METHODS Thirty vocal folds from 30 fresh cadavers were removed during necropsy performed at the Department of Pathology, Botucatu Medical School, Universidade Estadual Paulista (UNESP), between 2010 and 2013. The necropsies where completed within 2 hours of death. The larynges were divided into age groups: control (30–50 years; n 5 10 ) and elderly groups (60–75 years, n 5 10; 76–90 years , n 5 10). Each group included five males and five female larynges. Only the left vocal fold of
Martins et al.: Vocal Muscle Atrophy in the Aging Voice
This project was approved by the Human Research Ethics Committee of the Botucatu Medical School, UNESP. The statistical analysis for the comparison the muscle fibers (dependent variable) between age groups and genders involved the technique of parametric two-way factorial analysis of variance (ANOVA) in independent groups, followed by Tukey’s test for multiple comparisons with alpha adjustment, considering 5% significance level (P < 0.05).7
RESULTS The diameter of muscle fibers was significantly smaller in the elderly groups compared to the control group (P < 0.01) (Table I). No statistical differences were observed between gender. Fig. 1. Vocal fold of control group. Measure of the muscle fiber diameter (Image J software). Periodic acid-Schiff 403. [Color figure can be viewed in the online issue, which is available at www. laryngoscope.com.] each cadaver was removed; the right vocal fold was intended for another study. Exclusion criteria were history of sepsis, prolonged intubation, laryngeal lesions, systemic infectious diseases, dermatological diseases with connective tissue involvement, autoimmune or metabolic disorders, cervical trauma, peripheral nerve disease, Parkinson’s disease, amyotrophic lateral sclerosis, neuromotor disorders, or other causes that could affect the vocal folds mucosa and invalidate the morphological study. Medical records were consulted to confirm predeath diseases. When medical records were incomplete, family members were contacted to provide additional information on comorbidities. The midportion of the vocal folds were dissected and removed. Cross-sections of the fragments were made and fixed in 10% formaldehyde. Paraffin blocks were prepared, sectioned, and stained with periodic acid-Schiff. A pathologist and the author researchers (RHGM and ABBP) analyzed the slides blindly to the purpose of the study. Images of the muscle fibers contiguous to the vocal ligament (vocalis region of the thyroarytenoid muscle) were obtained, due the importance of this segment in the phonatory mechanism. A computer-assisted light microscope (Axiophot, Zeiss, Oberkochen, Germany) mounted to a digital camera (AxioCam HRc, Zeiss) was used. The morphometric analyses were performed using the ImageJ software to measure the diameter of the muscle fibers (lm) (Fig. 1). To measure the diameter of the muscle fibers, two noncontiguous fields of each slide were photographed at 103 magnification, and the muscle fibers under the deeper layer of lamina propria were selected. The diameters of 200 muscle fibers were measured from each vocal fold.
DISCUSSION The literature describes well enough the whole process of skeletal muscle modulation with respect to aging, but it rarely contemplates the vocal muscle in the elderly. According to Jang and Van Remmen,8 aging of skeletal muscle is characterized by gradual loss of muscular mass as well as functional impairment. This is known as sarcopenia, a physiological aging event that occurs in muscle mass. The muscle changes are multifactorial, associated with metabolic, nutritional, genetic, and endocrine events. This process affects quality of life in the elderly, increasing the risk of morbidity, physical handicap, and mortality. Similar to the aging process that takes place in the whole body, the laryngeal structures also suffer different modifications with aging such as cartilage calcification; slow neuromotor transmission; reduction in the number of mucous glands; decrease of elastic fibers in the lamina propria and increase in collagen fibers; epithelial atrophy; decrease of acid hyaluronic concentration; and atrophy of the intrinsic and extrinsic muscles, especially the thyroarytenoid muscle, which is an important tensor of the vocal folds.4 One of the more important characteristics of presbyphonia is glottic incompetence, directly related to the vocal muscle atrophy, and responsible for vocal symptoms such as breathiness and decrease in loudness that characterize phonasthenia. Furthermore, dysphagia is also frequent in the elderly and may be associated with cough and aspiration of food by impaired glottic closure due to atrophy of the vocal folds.9 Quantitative studies relating to the degree of atrophy of the laryngeal muscles are rare in the literature,
TABLE I. Measure of the Muscle Fiber Diameter (Mean 6 SD, mm) in Both Genders and Age Groups. Gender Age Groups (years)
Male
Female
Total
30–50
17.214 mm 6 1.139
15.565 mm 6 1.899
16.389 mm 6 1.713
60–75 76–90
14.354 mm 6 0.627 14.309 mm 6 0.452
14.471 mm 6 0.699 14.016 mm 6 0.921
14.412 mm 6 0.617* 14.162 mm 6 0.701*
Total
15.292 mm 6 1.595
14.684 mm 6 1.365
14.988 mm 6 1.486
Statistical analysis: P 5 0.174 between groups 3 gender; P 5 0.131 between genders; P < 0.01 between age groups (*). SD 5 standard deviation.
Laryngoscope 125: November 2015
Martins et al.: Vocal Muscle Atrophy in the Aging Voice
2519
what makes difficult the comparative analysis between measurements reported in the literature and those obtained in the current study. Malmgren et al.10 studied 29 human larynges (20 male, 9 female) from autopsies of cadavers aged between 26 and 97 years and evaluated the apoptosis process of myonuclei and satellite cells of the thyroarytenoid muscle. They found that the apoptosis occurred, specially in type I fibers of the human thyroarytenoid (TA) muscle, which may contribute to agerelated fiber loss and muscle atrophy. The authors suggest that treatments intended to modify the apoptotic threshold of the fibers can contribute to prevent vocal muscle atrophy in the elderly. In an experimental study, Nishida et al.11 compared the behavior of laryngeal intrinsic muscles (CT 5cricothyroid muscle; TA 5 thyroarytenoid muscle; PCA 5 posterior cricoarytenoid muscle) in adult and aged Wistar rats, analyzing the measurement of muscle fiber number and diameter (stained with hematoxylineosin and observed using light microscope), muscle contractile protein composition through analysis of the composition of myosin heavy chain isoforms (using gel electrophoresis method), and quantitative analysis of subneural apparatuses (using scanning electron microscopy [SEM]). In the elderly rats, the authors found a significant decrease in the diameter and number of CT muscle fibers, as well as a decrease in the number but not the diameter of the TA. No decrease in the number or diameter of PCA fibers was observed. The authors also investigated the myosin heavy chain (MHC) composition and found that greatest changes in proteins occurred in the CT muscle, with an increase in the expression of MHC isoforms of proteins type IIA and a decrease in type IIB. Changes in the morphology and subneural apparatuses on the CT muscle fibers were detected by SEM. Those results underscore the susceptibility of the CT muscle to the effects of aging, TA muscle being less affected, unlike in our results, in which we could observe a decrease in the diameter of TA fibers. We believe that such contradictions might be due to possible methodological differences between the studies; difference in animal species; and possible chronological sequence of events related to aging, with the atrophy of some muscles preceding others. Further studies in human larynges that include the three intrinsic laryngeal muscles would be interesting to answer these questions. Takeda et al.12 observed denervation and axonal lesions in the laryngeal motor control of the elderly, thus changing laryngeal muscles contraction. Although muscle atrophy is prominent, the epithelium and lamina propria are also very compromised in the elderly larynx. Some authors studied larynges of the elderly and observed an increase of collagen fibers, as well as a considerable decrease in elastic fibers and hyaluronic acid.13,14 The lack of these components compromises the viscoelastic properties of vocal folds, whereas the increase of collagen fibers favors their stiffness.15,16 Ximenes et al.17 conducted a study comparing the aging process of the vocal folds to the skin of the inguinal region in the elderly. They observed similar strucLaryngoscope 125: November 2015
2520
tural changes in both sites, such as epithelial and lamina propria atrophy. Voice therapy for presbyphonia has proved to be effective in improving glottic incompetence and vocal performance in the elderly.18,19 Johnson et al.20 studied the effects of voice therapy on neuromuscular mechanisms in rats using the ultrasonic vocalizations. In this study, young and old Fischer 344/Brown Norway male rats were trained during 8 weeks to increase their ultrasonic vocalization. The authors compared the results of the acoustic vocalization and the aspects of neuromuscular junction of the thyroarytenoid muscle to a no-intervention group (control). They observed that vocal training reduced some differences in both parameters (ultrasonic vocalization and neuromuscular junction measures) related to age and concluded that voice exercise may be an important preventive procedure in presbyphonia. However, in more severe cases the success of voice therapy is only partial. Various treatments have been proposed to restore the vocal folds volume and reduce glottic incompetence, keeping the vocal folds viscoelastic properties. Among these, the injection of hyaluronic acid and the administration of fibroblast growth factors and hepatocytes deserve to be highlighted.21 Hyaluronic acid seems to be more effective than other injectable substances, such as Teflon and fat, to maintain viscoelastic properties of the vocal folds.22,23 Growth factors, besides stimulating hyaluronic acid production, inhibit collagen production, promising great advances in phonosurgery.
CONCLUSION The current findings showed smaller diameters of vocal muscle fibers in the elderly when compared to controls, demonstrating the atrophy of the muscle. No statistical differences were observed between genders.
BIBLIOGRAPHY 1. de Araujo Pernambuco L, Espelt A, Balata PM, de Lima KC. Prevalence of voice disorders in the elderly: a systematic review of population-based studies. Arch Otorhinolaryngol 2014 Aug 23. Epub ahead of print. DOI 10.1007/s00405-014-3252-7. 2. Morrison M, Rammage J. Voice disorders in the elderly. The Management of Voice Disorders. San Diego, CA: Singular Publishing; 1994: 141–149. 3. Mifune E, Justino VSS, Camargo Z, Gregio F. Acoustic analysis of aging voice: fundamental frequency characterization. Rev CEFAC 2007;9:238– 247. 4. Kendall K. Presbyphonia: a review. Curr Opin Otolaryngol Head Neck Surg 2007;15:137–140. 5. Bloch I, Behrman A. Quantitative analysis of videostroboscopic images in presbylarynges. Laryngoscope 2001;111:2022–2027. 6. Hirano M. Morphological structure of the vocal cord as a vibration and its variations. Folia Phoniatr (Basel) 1974;26:89–94. 7. Zar JH. Biostatistical analysis. 5th ed. Upper Saddle River, NJ: PrenticeHall; 2009: 994. 8. Jang YC, Van Remmen H. Age-associated alterations of neuromuscular junction. Exp Gerontol 2011;46:193–198. 9. Ney DM, Weiss JM, Kind AJ, Robbins J. Senescent swallowing: impact, strategies and interventions. Nutr Clin Pract 2009;24:395–413. 10. Malmgren LT, Jones CE, Bookman LM. Muscle fiber and satellite cell apoptosis in the aging human thyroarytenoid muscle: a stereological study with confocallaser scanning microscopy. Otolaryngol Head Neck Surg 2001;125:34–39. 11. Nishida N, Taguchi A, Motoyoshi K, Hyodo M, Gyo K, Desaki J. Agerelated changes rat intrinsic muscle: analysis of muscle fibers, muscle fiber proteins, and subneural apparatuses. Eur Arc Otorhinolaryngol 2013;270:975–984. 12. Takeda N, Thomas GR, Ludlow CL. Aging effects on motor units in the human thyroarytenoid muscle. Laryngoscope 2000;110:1018–1025. 13. Roberts T, Morton R, Ali-Ali S. Microstructure of the vocal fold in elderly humans. Clin Anat 2011;24:544–551.
Martins et al.: Vocal Muscle Atrophy in the Aging Voice
14. Ohno T, Hirano S, Rousseau B. Age-associated changes in the expression and deposition of vocal fold collagen and hyaluronan. Ann Otol Rhinol Laryngol 2009;118:735–741. 15. Hammond T, Gray S, Butler J. Age and gender related collagen distributions in human vocal folds. Ann Otol Rhinol Laryngol 2000;109:913– 920. 16. Sato K, Hirano M, Nakashima T. Age-related changes of collagenous. Ann Otol Rhinol Laryngol 2002;111:15–20. 17. Ximenes Filho JA, Tsuji DH, do Nascimento PH, Sennes LU. Histologic changes in human vocal folds correlated with aging: a histomorphometric study. Ann Otol Rhinol Laryngol 2003;112:894–898. 18. Suehiro A, Wright H, Rousseau B. Optimal concentration of Hepatocyte growth factor for treatment of the aged rat vocal fold. Laryngoscope 2011;121:1726–1734.
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19. Chan RW, Titze IR. Hyaluronic acid (with fibronectin) as a bioimplant for the vocal fold mucosa. Laryngoscope 1999;109:1142–1149. 20. Johnson AM, Ciucci MR, Connor NP. Vocal training mitigates age-related changes within the vocal mechanism in old rats. J Gerontol A Biol Sci Med Sci 2013 68:1458–1468. 21. Hirano S, Bless DM, Rio AM, Connor NP, Ford CN. Therapeutic potential of growth factors for aging voice. Laryngoscope 2004;114: 2161–2167. 22. Duke SG, Salmon S, Blalock D, Postma GN, Koufman JA. Fascia augmentation of the vocal fold: graft yield in the canine and preliminary clinical experience. Laryngoscope 2001;11:759–764. 23. Remacle M, Lawson G. Injectable substances for vocal fold augmentation. Otolaryngol Head Neck Surg 2001;9:393–397.
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Rhinological and Otological Society, Inc.
Aging Voice and the Laryngeal Muscle Atrophy Regina Helena Garcia Martins, MD, PhD; Adriana Bueno Benito Pessin, PhD; Douglas Jorge Nassib; Anete Branco, PhD; Sergio Augusto Rodrigues, PhD; Selma Maria Michelim Matheus, PhD Objectives/Hypothesis: To study by means of morphometric measurements the severity of vocal muscle atrophy in the elderly. Study Design: Cadaver study. Setting: Universidade Estadual Paulista (UNESP), Botucatu Medical School, Brazil. Subjects and Methods: Thirty vocal folds were collected from necropsies distributed into three groups: aged 60 to 75 years (n 5 10); aged 76 to 90 years (n 5 10); and a control group aged 30 to 50 years (n 5 10). Specimens for histology were obtained from the middle portion of the vocal folds. The stained specimens were analyzed using Axion Vision software (coupled to a Zeiss [Oberkochen, Germany] microscope) and used in the morphometric analyses conducted with the ImageJ software. The diameters of 200 muscle fibers from each slide were measured, and the mean values were statistically analyzed. Results: The mean values of the diameters of the vocal muscle fibers of the elderly age groups were smaller than in the control: control (30–50 years: 16.389 lm); elderly (60–75 years: 14.412 lm; 76–90 years: 14.162 lm) (P < 0.01). No statistical differences were observed between genders. Conclusion: The morphometric analysis showed smaller diameters of vocal muscle fibers in the elderly when compared to controls, demonstrating the atrophy of the muscle. No statistical differences were observed between genders. Key Words: Larynx, voice, vocal muscle, presbyphonia, morphometry. Level of Evidence: N/A. Laryngoscope, 125:2518–2521, 2015
INTRODUCTION Presbyphonia refers to the process of voice aging. The etiology is multifactorial, including natural anatomical and physiological changes. A systematic review of the prevalence of voice disorders in subjects older than 60 years included only four articles, which identified vocal disorders in 4.8% to 29.1% of such individuals.1 The common symptoms of presbyphonia in the elderly population are poor vocal projection, reduced loudness, hoarseness, lowered pitch in women and raised pitch in men, decreased duration of phonation, tremor, and breathiness.2–4 Videolaryngoscopy in the elderly show atrophic, bowed vocal folds; salivary stasis; prominence of the From the Department of Ophthalmology, Otolaryngology and Head and Neck Surgery, Botucatu Medical School, UNESP–Univ Estadual Paulista (R.H.G.M.); the Department of Otolaryngology, Botucatu Medical ao Paulo School, UNESP–Univ Estadual Paulista (A.B.B.P., A.B., D.J.N.); S~ State Technological College/FATEC (S.A.R.), Botucatu; and the Department of Anatomy, Institute of Bioscience–UNESP (S.M.M.M.), Univ Estadual Paulista, Botucatu, SP, Brazil. Editor’s Note: This Manuscript was accepted for publication April 30, 2015. This work was funded by S~ ao Paulo Research Foundation (FAPESP) for the preparation of the histological samples. The authors have no other funding, financial relationships, or conflicts of interest to disclose. Send correspondence to Dr. Regina H. G. Martins, Department of Ophthalmology, Otorhinolaryngology and Head and Neck Surgery, Botucatu Medical School–Universidade Estadual Paulista, Distrito de Rubi~ ao Junior s/n, 18618-970, Botucatu-SP, Brazil. E-mail: [email protected]. br DOI: 10.1002/lary.25398
Laryngoscope 125: November 2015
2518
vocal apophysis; and pseudosulcus. Such vocal changes result from alterations involving all of the structures of the larynx, including calcification of the hyaline cartilages; decreased mucosal secretions; decreased neuromotor control; mucosal atrophy; changes in the components of the lamina propria, such as an increased number of collagen fibers and a decreased elastic fibers and hyaluronic acid; and muscle atrophy.5,6 In the larynx of adults, there is a higher concentration of elastin in the superficial layers of the lamina propria. Collagen fibers are more abundant in intermediate and deeper layers. In the elderly, the atrophy of the vocal folds results from the scarcity of elastic fibers and hyaluronic acid, as well as from atrophy of the vocal muscle.6 When the vocal muscle becomes atrophic, power and vocal intensity decrease, affecting vocal performance. These symptoms are very relevant for some older people, especially those who stay active in their profession. Therefore, this study intends to examine the degree of atrophy of the vocal muscle in the elderly larynx.
SUBJECTS AND METHODS Thirty vocal folds from 30 fresh cadavers were removed during necropsy performed at the Department of Pathology, Botucatu Medical School, Universidade Estadual Paulista (UNESP), between 2010 and 2013. The necropsies where completed within 2 hours of death. The larynges were divided into age groups: control (30–50 years; n 5 10 ) and elderly groups (60–75 years, n 5 10; 76–90 years , n 5 10). Each group included five males and five female larynges. Only the left vocal fold of
Martins et al.: Vocal Muscle Atrophy in the Aging Voice
This project was approved by the Human Research Ethics Committee of the Botucatu Medical School, UNESP. The statistical analysis for the comparison the muscle fibers (dependent variable) between age groups and genders involved the technique of parametric two-way factorial analysis of variance (ANOVA) in independent groups, followed by Tukey’s test for multiple comparisons with alpha adjustment, considering 5% significance level (P < 0.05).7
RESULTS The diameter of muscle fibers was significantly smaller in the elderly groups compared to the control group (P < 0.01) (Table I). No statistical differences were observed between gender. Fig. 1. Vocal fold of control group. Measure of the muscle fiber diameter (Image J software). Periodic acid-Schiff 403. [Color figure can be viewed in the online issue, which is available at www. laryngoscope.com.] each cadaver was removed; the right vocal fold was intended for another study. Exclusion criteria were history of sepsis, prolonged intubation, laryngeal lesions, systemic infectious diseases, dermatological diseases with connective tissue involvement, autoimmune or metabolic disorders, cervical trauma, peripheral nerve disease, Parkinson’s disease, amyotrophic lateral sclerosis, neuromotor disorders, or other causes that could affect the vocal folds mucosa and invalidate the morphological study. Medical records were consulted to confirm predeath diseases. When medical records were incomplete, family members were contacted to provide additional information on comorbidities. The midportion of the vocal folds were dissected and removed. Cross-sections of the fragments were made and fixed in 10% formaldehyde. Paraffin blocks were prepared, sectioned, and stained with periodic acid-Schiff. A pathologist and the author researchers (RHGM and ABBP) analyzed the slides blindly to the purpose of the study. Images of the muscle fibers contiguous to the vocal ligament (vocalis region of the thyroarytenoid muscle) were obtained, due the importance of this segment in the phonatory mechanism. A computer-assisted light microscope (Axiophot, Zeiss, Oberkochen, Germany) mounted to a digital camera (AxioCam HRc, Zeiss) was used. The morphometric analyses were performed using the ImageJ software to measure the diameter of the muscle fibers (lm) (Fig. 1). To measure the diameter of the muscle fibers, two noncontiguous fields of each slide were photographed at 103 magnification, and the muscle fibers under the deeper layer of lamina propria were selected. The diameters of 200 muscle fibers were measured from each vocal fold.
DISCUSSION The literature describes well enough the whole process of skeletal muscle modulation with respect to aging, but it rarely contemplates the vocal muscle in the elderly. According to Jang and Van Remmen,8 aging of skeletal muscle is characterized by gradual loss of muscular mass as well as functional impairment. This is known as sarcopenia, a physiological aging event that occurs in muscle mass. The muscle changes are multifactorial, associated with metabolic, nutritional, genetic, and endocrine events. This process affects quality of life in the elderly, increasing the risk of morbidity, physical handicap, and mortality. Similar to the aging process that takes place in the whole body, the laryngeal structures also suffer different modifications with aging such as cartilage calcification; slow neuromotor transmission; reduction in the number of mucous glands; decrease of elastic fibers in the lamina propria and increase in collagen fibers; epithelial atrophy; decrease of acid hyaluronic concentration; and atrophy of the intrinsic and extrinsic muscles, especially the thyroarytenoid muscle, which is an important tensor of the vocal folds.4 One of the more important characteristics of presbyphonia is glottic incompetence, directly related to the vocal muscle atrophy, and responsible for vocal symptoms such as breathiness and decrease in loudness that characterize phonasthenia. Furthermore, dysphagia is also frequent in the elderly and may be associated with cough and aspiration of food by impaired glottic closure due to atrophy of the vocal folds.9 Quantitative studies relating to the degree of atrophy of the laryngeal muscles are rare in the literature,
TABLE I. Measure of the Muscle Fiber Diameter (Mean 6 SD, mm) in Both Genders and Age Groups. Gender Age Groups (years)
Male
Female
Total
30–50
17.214 mm 6 1.139
15.565 mm 6 1.899
16.389 mm 6 1.713
60–75 76–90
14.354 mm 6 0.627 14.309 mm 6 0.452
14.471 mm 6 0.699 14.016 mm 6 0.921
14.412 mm 6 0.617* 14.162 mm 6 0.701*
Total
15.292 mm 6 1.595
14.684 mm 6 1.365
14.988 mm 6 1.486
Statistical analysis: P 5 0.174 between groups 3 gender; P 5 0.131 between genders; P < 0.01 between age groups (*). SD 5 standard deviation.
Laryngoscope 125: November 2015
Martins et al.: Vocal Muscle Atrophy in the Aging Voice
2519
what makes difficult the comparative analysis between measurements reported in the literature and those obtained in the current study. Malmgren et al.10 studied 29 human larynges (20 male, 9 female) from autopsies of cadavers aged between 26 and 97 years and evaluated the apoptosis process of myonuclei and satellite cells of the thyroarytenoid muscle. They found that the apoptosis occurred, specially in type I fibers of the human thyroarytenoid (TA) muscle, which may contribute to agerelated fiber loss and muscle atrophy. The authors suggest that treatments intended to modify the apoptotic threshold of the fibers can contribute to prevent vocal muscle atrophy in the elderly. In an experimental study, Nishida et al.11 compared the behavior of laryngeal intrinsic muscles (CT 5cricothyroid muscle; TA 5 thyroarytenoid muscle; PCA 5 posterior cricoarytenoid muscle) in adult and aged Wistar rats, analyzing the measurement of muscle fiber number and diameter (stained with hematoxylineosin and observed using light microscope), muscle contractile protein composition through analysis of the composition of myosin heavy chain isoforms (using gel electrophoresis method), and quantitative analysis of subneural apparatuses (using scanning electron microscopy [SEM]). In the elderly rats, the authors found a significant decrease in the diameter and number of CT muscle fibers, as well as a decrease in the number but not the diameter of the TA. No decrease in the number or diameter of PCA fibers was observed. The authors also investigated the myosin heavy chain (MHC) composition and found that greatest changes in proteins occurred in the CT muscle, with an increase in the expression of MHC isoforms of proteins type IIA and a decrease in type IIB. Changes in the morphology and subneural apparatuses on the CT muscle fibers were detected by SEM. Those results underscore the susceptibility of the CT muscle to the effects of aging, TA muscle being less affected, unlike in our results, in which we could observe a decrease in the diameter of TA fibers. We believe that such contradictions might be due to possible methodological differences between the studies; difference in animal species; and possible chronological sequence of events related to aging, with the atrophy of some muscles preceding others. Further studies in human larynges that include the three intrinsic laryngeal muscles would be interesting to answer these questions. Takeda et al.12 observed denervation and axonal lesions in the laryngeal motor control of the elderly, thus changing laryngeal muscles contraction. Although muscle atrophy is prominent, the epithelium and lamina propria are also very compromised in the elderly larynx. Some authors studied larynges of the elderly and observed an increase of collagen fibers, as well as a considerable decrease in elastic fibers and hyaluronic acid.13,14 The lack of these components compromises the viscoelastic properties of vocal folds, whereas the increase of collagen fibers favors their stiffness.15,16 Ximenes et al.17 conducted a study comparing the aging process of the vocal folds to the skin of the inguinal region in the elderly. They observed similar strucLaryngoscope 125: November 2015
2520
tural changes in both sites, such as epithelial and lamina propria atrophy. Voice therapy for presbyphonia has proved to be effective in improving glottic incompetence and vocal performance in the elderly.18,19 Johnson et al.20 studied the effects of voice therapy on neuromuscular mechanisms in rats using the ultrasonic vocalizations. In this study, young and old Fischer 344/Brown Norway male rats were trained during 8 weeks to increase their ultrasonic vocalization. The authors compared the results of the acoustic vocalization and the aspects of neuromuscular junction of the thyroarytenoid muscle to a no-intervention group (control). They observed that vocal training reduced some differences in both parameters (ultrasonic vocalization and neuromuscular junction measures) related to age and concluded that voice exercise may be an important preventive procedure in presbyphonia. However, in more severe cases the success of voice therapy is only partial. Various treatments have been proposed to restore the vocal folds volume and reduce glottic incompetence, keeping the vocal folds viscoelastic properties. Among these, the injection of hyaluronic acid and the administration of fibroblast growth factors and hepatocytes deserve to be highlighted.21 Hyaluronic acid seems to be more effective than other injectable substances, such as Teflon and fat, to maintain viscoelastic properties of the vocal folds.22,23 Growth factors, besides stimulating hyaluronic acid production, inhibit collagen production, promising great advances in phonosurgery.
CONCLUSION The current findings showed smaller diameters of vocal muscle fibers in the elderly when compared to controls, demonstrating the atrophy of the muscle. No statistical differences were observed between genders.
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