Ann 0101 88 :1979
CRICOTHYROID DISTANCE AND VOCAL PITCH EXPERIMENTAL SURGICAL STUDY TO ELEVATE THE VOCAL PITCH
KAZUTOMO KITAJIMA, MD MASAHffiO TANABE, MD
NOBUHIKO ISSH1KI, MD KYOTO, JAPAN
To establish an experimental basis for surgical approximation of the anterior cricothyroid distance which aims at raising the vocal pitch, the relationship between vocal pitch and the cricothyroid distance was analyzed in voices produced with excised human larynges (four male and two female larynges). Within the framework of the experimental conditions, the following conclusions were drawn: 1) The vocal pitch expressed in semitones was almost linearly related to the cricothyroid distance, with an increase of 0.15 to 0.90 semitones per millimeter of cricothyroid approximation. 2) The rise in vocal pitch reached a plateau when the force applied to shorten the cricothyroid distance reached 30 to 50 gm,
No effective conservative treatment has been reported for restoring an adequate pitch in females who have abnormally low voices. This disorder of pitch is frequently caused by 1) medication of anabolic steroids, 2) disturbance of the endocrine system or, 3) paralysis of the cricothyroid (CT) muscles. As a surgical procedure for this disorder, we have proposed a thyroplasty Type IV, i.e., CT approximation.l-"
vocal cord was elicited by blowing into a tube connected to the trachea.' Two points were marked on each laryngeal specimen on the anterior midline, one on the lower margin of the thyroid cartilage, and the other on the upper margin of cricoid cartilage. The distance between these two points was defined as the CT distance (Fig. 2). The CT distance was adjusted by two means: a) by loading weights onto a nylon thread sutured to the thyroid cartilage in the midline (Fig. 2), and b) by tightening a nylon thread spanning the thyroid and cricoid cartilages at one of three different suture sites. As shown in Figure 3, these were 1) the midline, 2) the site corresponding to the pars recta of the cricothyroid muscle and 3) the site corresponding to the pars obliqua of the same muscle. Under each of the above conditions voice was produced artificially with each specimen. The flow rate and the subglottal pressure were held constant for each trial. The CT distance and vocal cord length were measured for each trial phonation and the pitch of voice produced was recorded. While it is evident that the thyroarytenoid muscle also plays an important role in pitch control, we omitted evaluation of this muscle in pitch control in the present experiment, because it is virtually impossible to simulate the contraction of the internal thyroarytenoid muscle (vocal muscle) just by the string and weight system. Surgical simulation of contraction of this muscle is also impractical.
To obtain an experimental basis for this procedure, we designed an experiment to learn 1) the relationship between the vocal pitch and the CT distance and 2) the most effective means of suturing to shorten the CT distance. METHODS AND MATERIALS Six excised human larynges with no pathological changes on the vocal cords (four males and two females) were used to produce an artificial voice. The cricoid cartilage was fixed with an iron holder, while the thyroid cartilage was left free. Glottal closure was achieved by simulating the contraction of the lateral cricoarytenoid and interarytenoid muscles by use of known weights connected to the muscular process of the arytenoid cartilage (Fig. 1). A weight of 20 or 50 gm was applied to simulate the contraction of the lateral cricoarytenoid muscles, and of 10 gm for the interarytenoid muscle.' These conditions of glottal closure were held constant for each experiment. Vibration of the
RESULTS
Weight (Contractional Force of the Cricothyroid Muscles) and the Vocal
From the Voice Science Laboratory, Departments of Otolaryngology and Plastic Surgery, Kyoto University, Kyoto, Japan.
52
Downloaded from aor.sagepub.com at FLORIDA ATLANTIC UNIV on July 14, 2015
ELEVATION OF VOCAL PITCH
Fig. 1. Glottal closure was achieved by simulating the contraction of the lateral cricoarytenoid and interarytenoid muscles by use of known weights connected to the muscular process of the arytenoid cartilage. W, - Weights correspond to the forces produced by the lateral cricoarytenoid muscles; W2 - Weights correspond to the forces produced by the interarytenoid muscle.
Pitch. The relationship between the vocal pitch and the weight applied in the direction of the cricothyroid muscles is shown in Figure 4. It is noted that elevation of the pitch is remarkable and almost linearly related with the weight up to 30 to 50 gm. Weighing over that value raises the pitch only slightly.
Figure 5 shows the change in CT
53
Fig. 3. The cricothyroid distance was adjusted by tightening the nylon thread spanning the thyroid and cricoid cartilages at one of three suture sites: 1) the midline, 2) the site corresponding to the pars recta of the cricothyroid muscle, 3) the site corresponding to the pars obliqua of the same muscle.
distance induced by the force simulating the cricothyroid The shortening effect of the CT distance is much reduced force exceeds 50 gm.
(weight) muscles. force on when the
The relationship between CT distance and the vocal pitch is illustrated in Figure 6. Although the pitch increment per unit shortening of CT distance varies from one specimen to another, the relationship between pitch and CT distance is generally almost linear. The pitch increment per unit shortening of CT distance tends to be greater in female larynges (nos. 1 and 2) than male. N
z: lOOOr
•
0' 0' j
s:
~ 500
'0.
o
/~., I ,,'
.'
!",. ,,0 X
•
•
•
x x .0,0
0-
.»:":
--
e
100
o
50
100
200
weight
sm.
specimen number
Fig. 2. TIle cricothyroid distance (CT) was adjusted by loading a weight (W) onto a nylon thread sutured to the thyroid cartilage in the midline.
• 1
x3
"5
02
04
·6
Fig. 4. The change of vocal pitch induced by the force (weight) simulating the cricothyroid muscle. There is a linear relationship between vocal pitch and the force (weight) of the cricothyroid muscle. Note that weights in excess of 50 gm raise pitch only slightly.
Downloaded from aor.sagepub.com at FLORIDA ATLANTIC UNIV on July 14, 2015
54
KIT AlIMA ET AL ~ 1000
.J: CJ
... '0.
~
u
-.
500
111
CJ 0
200
>
3
specimen
2
number 6
100 o
8 0
50
100
weight
.,
, 3
02
04
7
6
5
4
3
mm
200 gm .
CT distance
specimen number
6
Fig. 5. The change in CT distance induced by the force (weight) simulating the cricothyroid muscle. Note that the shortening effect of the force on CT distance is much reduced when the force exceeds 50 gm,
Shortening of the CT distance by 1 mm elevates the pitch by 0.15 to 0.90 semitones.
Cricothyroid Approximation with Nylon Suture. In order to find the most effective position and direction for pitch elevation of the suture connecting the cricoid and thyroid cartilages, the three suture sites described above were compared. Figure 7 shows the results for one of the specimens, indicating
Fig. 7. Elevation of vocal pitch as a function of CT distance for three suture sites. Numbers correspond to the suture sites shown in Fig. 3. No significant difference in pitch elevation is seen among the three sites.
that pitch rises as a function of CT distance for the three sutures. The numbers in this figure correspond to the suture sites in Figure 3. In this specimen there were no significant differences in pitch elevation due to the suture site. In other words, the same degree of pitch elevation was obtained regardless of the suture position provided the CT distance was the same. Three other cases showed a similar tendency. However a different trend was noted in the other two specimens, as exemplified in Figure 8. A steeper elevation of pitch was obtained with the suture at site 2 than at site 1. Site 3 N :c 1000
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Fig. 6. CT distance and vocal pitch show an almost linear relationship. The pitch increment per unit shortening of CT distance tends to be greater in female larynges (nos. 1 and 2) than male.
CT distance
Fig. 8. A steeper elevation of pitch is obtained with the suture at site 2 than at site 1.
Downloaded from aor.sagepub.com at FLORIDA ATLANTIC UNIV on July 14, 2015
ELEVATION OF VOCAL PITCH
55
the surgeon can insert the needle deeply enough without fear of injuring the mucous membrane of the larynx. At site 3, calcification of the thyroid ala is sometimes observed from early age. Therefore to place a suture in this site is relatively difficult. It can thus be concluded that the approximation of the CT cartilages by suturing at site 2 is advisable.
could not be tested because of the advanced calcification of the thyroid cartilage. DISCUSSION
In two specimens out of six, positioning of the suture along the pars recta of the cricothyroid muscle (site 2) produced a greater elevation of pitch than at the other two sites. On the other hand, no remarkable differences in pitch elevation were observed between the three suture sites in the other four specimens. To evaluate the suture sites, anatomical features must be considered with the findings of this study. The thyroid cartilage is rather thin in the midportion, and a needle placed in this position can easily injure the mucous membrane of the laryngeal cavity. On the other hand, the sites to which the pars obliqua and pars recta of the cricothyroid muscle are attached are thicker and can withstand the tension of the nylon thread. Also in this position
In our experiment using the larynx of human cadaver, the elevation of the pitch resulting from a 1 mm approximation of CT cartilages was 0.15 to 0.90 semitones. The experiment was performed on larynges which had no pathological changes in the vocal cords. In clinical practice, abnormally low voice in the female is frequently caused by the medication of anabolic steroids, which produces extreme thickening of the vocal cords. In these cases the elevation of pitch would probably not be so marked as in the present experiment.
REFERENCES 1. Isshiki N, Morita H, Okamura H, et al: Thyroplasty as a new phonological technique. Acta Otolaryngol (Stockh) 78:451-457, 1974 2. Isshiki N, Okamura H, Ishikawa T: Thyroplasty type 1 (lateral compression) for dysphonia due to vocal cord paralysis or atrophy. Acta Otolaryngol (Stockh) 80 :465-473
1m
'
3. Isshiki N, Tanabe M, Ishizaka K, et al: Clinical significance of asymmetrical vocal cord tension. Ann Otol Rhinol Laryngol 86: 58-66, 1977 4. van den Berg 1. Tan TS: Results of experiments with human larynges. Pract OtoRhino-Laryngol 21:425, 1959
REPRINTS - Kazutomo Kitajima, MD, Voice Science Lab., Department of Otolaryngology School of Medicine, Kyoto University, Kyoto, 606, Japan. '
CANADIAN OTOLARYNGOLOGICAL SOCIETY The annual meeting of the Canadian Otolaryngological Society will be held June 6-8 1979 at the Harbour Castle Hotel, Toronto, Ontario. Inquiries may be sent to Dr. David Briant Sec' retary, St. Michaels Hospital, Toronto, Ontario M5B 1WB.
Downloaded from aor.sagepub.com at FLORIDA ATLANTIC UNIV on July 14, 2015
CRICOTHYROID DISTANCE AND VOCAL PITCH EXPERIMENTAL SURGICAL STUDY TO ELEVATE THE VOCAL PITCH
KAZUTOMO KITAJIMA, MD MASAHffiO TANABE, MD
NOBUHIKO ISSH1KI, MD KYOTO, JAPAN
To establish an experimental basis for surgical approximation of the anterior cricothyroid distance which aims at raising the vocal pitch, the relationship between vocal pitch and the cricothyroid distance was analyzed in voices produced with excised human larynges (four male and two female larynges). Within the framework of the experimental conditions, the following conclusions were drawn: 1) The vocal pitch expressed in semitones was almost linearly related to the cricothyroid distance, with an increase of 0.15 to 0.90 semitones per millimeter of cricothyroid approximation. 2) The rise in vocal pitch reached a plateau when the force applied to shorten the cricothyroid distance reached 30 to 50 gm,
No effective conservative treatment has been reported for restoring an adequate pitch in females who have abnormally low voices. This disorder of pitch is frequently caused by 1) medication of anabolic steroids, 2) disturbance of the endocrine system or, 3) paralysis of the cricothyroid (CT) muscles. As a surgical procedure for this disorder, we have proposed a thyroplasty Type IV, i.e., CT approximation.l-"
vocal cord was elicited by blowing into a tube connected to the trachea.' Two points were marked on each laryngeal specimen on the anterior midline, one on the lower margin of the thyroid cartilage, and the other on the upper margin of cricoid cartilage. The distance between these two points was defined as the CT distance (Fig. 2). The CT distance was adjusted by two means: a) by loading weights onto a nylon thread sutured to the thyroid cartilage in the midline (Fig. 2), and b) by tightening a nylon thread spanning the thyroid and cricoid cartilages at one of three different suture sites. As shown in Figure 3, these were 1) the midline, 2) the site corresponding to the pars recta of the cricothyroid muscle and 3) the site corresponding to the pars obliqua of the same muscle. Under each of the above conditions voice was produced artificially with each specimen. The flow rate and the subglottal pressure were held constant for each trial. The CT distance and vocal cord length were measured for each trial phonation and the pitch of voice produced was recorded. While it is evident that the thyroarytenoid muscle also plays an important role in pitch control, we omitted evaluation of this muscle in pitch control in the present experiment, because it is virtually impossible to simulate the contraction of the internal thyroarytenoid muscle (vocal muscle) just by the string and weight system. Surgical simulation of contraction of this muscle is also impractical.
To obtain an experimental basis for this procedure, we designed an experiment to learn 1) the relationship between the vocal pitch and the CT distance and 2) the most effective means of suturing to shorten the CT distance. METHODS AND MATERIALS Six excised human larynges with no pathological changes on the vocal cords (four males and two females) were used to produce an artificial voice. The cricoid cartilage was fixed with an iron holder, while the thyroid cartilage was left free. Glottal closure was achieved by simulating the contraction of the lateral cricoarytenoid and interarytenoid muscles by use of known weights connected to the muscular process of the arytenoid cartilage (Fig. 1). A weight of 20 or 50 gm was applied to simulate the contraction of the lateral cricoarytenoid muscles, and of 10 gm for the interarytenoid muscle.' These conditions of glottal closure were held constant for each experiment. Vibration of the
RESULTS
Weight (Contractional Force of the Cricothyroid Muscles) and the Vocal
From the Voice Science Laboratory, Departments of Otolaryngology and Plastic Surgery, Kyoto University, Kyoto, Japan.
52
Downloaded from aor.sagepub.com at FLORIDA ATLANTIC UNIV on July 14, 2015
ELEVATION OF VOCAL PITCH
Fig. 1. Glottal closure was achieved by simulating the contraction of the lateral cricoarytenoid and interarytenoid muscles by use of known weights connected to the muscular process of the arytenoid cartilage. W, - Weights correspond to the forces produced by the lateral cricoarytenoid muscles; W2 - Weights correspond to the forces produced by the interarytenoid muscle.
Pitch. The relationship between the vocal pitch and the weight applied in the direction of the cricothyroid muscles is shown in Figure 4. It is noted that elevation of the pitch is remarkable and almost linearly related with the weight up to 30 to 50 gm. Weighing over that value raises the pitch only slightly.
Figure 5 shows the change in CT
53
Fig. 3. The cricothyroid distance was adjusted by tightening the nylon thread spanning the thyroid and cricoid cartilages at one of three suture sites: 1) the midline, 2) the site corresponding to the pars recta of the cricothyroid muscle, 3) the site corresponding to the pars obliqua of the same muscle.
distance induced by the force simulating the cricothyroid The shortening effect of the CT distance is much reduced force exceeds 50 gm.
(weight) muscles. force on when the
The relationship between CT distance and the vocal pitch is illustrated in Figure 6. Although the pitch increment per unit shortening of CT distance varies from one specimen to another, the relationship between pitch and CT distance is generally almost linear. The pitch increment per unit shortening of CT distance tends to be greater in female larynges (nos. 1 and 2) than male. N
z: lOOOr
•
0' 0' j
s:
~ 500
'0.
o
/~., I ,,'
.'
!",. ,,0 X
•
•
•
x x .0,0
0-
.»:":
--
e
100
o
50
100
200
weight
sm.
specimen number
Fig. 2. TIle cricothyroid distance (CT) was adjusted by loading a weight (W) onto a nylon thread sutured to the thyroid cartilage in the midline.
• 1
x3
"5
02
04
·6
Fig. 4. The change of vocal pitch induced by the force (weight) simulating the cricothyroid muscle. There is a linear relationship between vocal pitch and the force (weight) of the cricothyroid muscle. Note that weights in excess of 50 gm raise pitch only slightly.
Downloaded from aor.sagepub.com at FLORIDA ATLANTIC UNIV on July 14, 2015
54
KIT AlIMA ET AL ~ 1000
.J: CJ
... '0.
~
u
-.
500
111
CJ 0
200
>
3
specimen
2
number 6
100 o
8 0
50
100
weight
.,
, 3
02
04
7
6
5
4
3
mm
200 gm .
CT distance
specimen number
6
Fig. 5. The change in CT distance induced by the force (weight) simulating the cricothyroid muscle. Note that the shortening effect of the force on CT distance is much reduced when the force exceeds 50 gm,
Shortening of the CT distance by 1 mm elevates the pitch by 0.15 to 0.90 semitones.
Cricothyroid Approximation with Nylon Suture. In order to find the most effective position and direction for pitch elevation of the suture connecting the cricoid and thyroid cartilages, the three suture sites described above were compared. Figure 7 shows the results for one of the specimens, indicating
Fig. 7. Elevation of vocal pitch as a function of CT distance for three suture sites. Numbers correspond to the suture sites shown in Fig. 3. No significant difference in pitch elevation is seen among the three sites.
that pitch rises as a function of CT distance for the three sutures. The numbers in this figure correspond to the suture sites in Figure 3. In this specimen there were no significant differences in pitch elevation due to the suture site. In other words, the same degree of pitch elevation was obtained regardless of the suture position provided the CT distance was the same. Three other cases showed a similar tendency. However a different trend was noted in the other two specimens, as exemplified in Figure 8. A steeper elevation of pitch was obtained with the suture at site 2 than at site 1. Site 3 N :c 1000
1
s:
...
500
"
/
/'
(21//'
1//(1)
CJ
'a'
/
1I I
ell
CJ 0
1
0
mm
specimen number 2
I
1001
specimen number e1 02
>
2':>01,
x3 04
05 • 8
I 87654
mm
Fig. 6. CT distance and vocal pitch show an almost linear relationship. The pitch increment per unit shortening of CT distance tends to be greater in female larynges (nos. 1 and 2) than male.
CT distance
Fig. 8. A steeper elevation of pitch is obtained with the suture at site 2 than at site 1.
Downloaded from aor.sagepub.com at FLORIDA ATLANTIC UNIV on July 14, 2015
ELEVATION OF VOCAL PITCH
55
the surgeon can insert the needle deeply enough without fear of injuring the mucous membrane of the larynx. At site 3, calcification of the thyroid ala is sometimes observed from early age. Therefore to place a suture in this site is relatively difficult. It can thus be concluded that the approximation of the CT cartilages by suturing at site 2 is advisable.
could not be tested because of the advanced calcification of the thyroid cartilage. DISCUSSION
In two specimens out of six, positioning of the suture along the pars recta of the cricothyroid muscle (site 2) produced a greater elevation of pitch than at the other two sites. On the other hand, no remarkable differences in pitch elevation were observed between the three suture sites in the other four specimens. To evaluate the suture sites, anatomical features must be considered with the findings of this study. The thyroid cartilage is rather thin in the midportion, and a needle placed in this position can easily injure the mucous membrane of the laryngeal cavity. On the other hand, the sites to which the pars obliqua and pars recta of the cricothyroid muscle are attached are thicker and can withstand the tension of the nylon thread. Also in this position
In our experiment using the larynx of human cadaver, the elevation of the pitch resulting from a 1 mm approximation of CT cartilages was 0.15 to 0.90 semitones. The experiment was performed on larynges which had no pathological changes in the vocal cords. In clinical practice, abnormally low voice in the female is frequently caused by the medication of anabolic steroids, which produces extreme thickening of the vocal cords. In these cases the elevation of pitch would probably not be so marked as in the present experiment.
REFERENCES 1. Isshiki N, Morita H, Okamura H, et al: Thyroplasty as a new phonological technique. Acta Otolaryngol (Stockh) 78:451-457, 1974 2. Isshiki N, Okamura H, Ishikawa T: Thyroplasty type 1 (lateral compression) for dysphonia due to vocal cord paralysis or atrophy. Acta Otolaryngol (Stockh) 80 :465-473
1m
'
3. Isshiki N, Tanabe M, Ishizaka K, et al: Clinical significance of asymmetrical vocal cord tension. Ann Otol Rhinol Laryngol 86: 58-66, 1977 4. van den Berg 1. Tan TS: Results of experiments with human larynges. Pract OtoRhino-Laryngol 21:425, 1959
REPRINTS - Kazutomo Kitajima, MD, Voice Science Lab., Department of Otolaryngology School of Medicine, Kyoto University, Kyoto, 606, Japan. '
CANADIAN OTOLARYNGOLOGICAL SOCIETY The annual meeting of the Canadian Otolaryngological Society will be held June 6-8 1979 at the Harbour Castle Hotel, Toronto, Ontario. Inquiries may be sent to Dr. David Briant Sec' retary, St. Michaels Hospital, Toronto, Ontario M5B 1WB.
Downloaded from aor.sagepub.com at FLORIDA ATLANTIC UNIV on July 14, 2015
