Keywords
voice - vocal cords - voice quality
Introduction
Several factors can interfere in vocal quality, including biological, psychological
or socioeducational aspects.[1] However, the morphological dimension of the speech apparatrus, especially the larynx,
has a significant influence on voice characteristics.[1]
[2] Although there is a supposed anatomical model of the larynx that represents the
symmetry of its halves, and vocal cords with a uniform and stratified surface in the
epithelium, lamina propria with three distinct layers and vocal muscle, this conformation
seems not to be found in the entire population.[3] Small anatomical alterations in the larynx, such as the sulcus vocalis, can change
its functional result, predisposing individuals to dysphonia (hoarseness) or vocal
fatigue.[1]
[2]
[4]
The sulcus vocalis is defined as a longitudinal depression in a vocal cord parallel
to its free border, which can vary in extension and depth, and be unilateral or present
in both vocal cords. Histologically, the sulcus is located on the surface layer of
the lamina propria and is lined with the stratified epithelium, contiguous to the
epithelium with a normal mucosal lining.[2] Sulcus changes are classified according to their morphological characteristics and
the degree to which the vocal cord structures are compromised. Ford et al (1996)[5] divided sulcus disorders of the vocal folds into 3 groups: In type I, epitelial
invagination is limited to the lamina propria; type II, epithelial invagination along
the vocal fold length; type III is the true sulcus vocalis (pocket type) and represents
an epithelial invagination that may penetrate into the vocal ligament and/or vocalis
muscle layers. Pontes et al (1994)[2] propose the following categories: sulcus stria minor—epithelial invagination, whose
upper and lower lips usually touch each other; sulcus stria major—spindle-shaped mucosal
depression, with a stiffer consistency and adhering to deeper structures, such as
the vocal ligament and muscle; pouch-shaped sulcus—lesion that emerges as an invagination,
whereby its lips touch each other and the opening leads to a dilated pouch-shaped
subepithelial space.
The real incidence of sulcus vocalis is unknown, due to three factors: lack of knowledge
of this laryngeal alteration, diagnostic error, or the absence of diagnosis when vocal
symptoms are not serious enough to cause vocal complaints.[6] Currently, examinations such as videolaryngoscopy, videolaryngostroboscopy or suspension
microlaryngoscopy are used to investigate morphological and structural changes in
the vocal cords, although it is important to consider the data related to the clinical
history of vocal alterations.[1]
[6]
[7]
[8]
[9]
It is important to underscore that the sulcus vocalis is not always evident in videolaryngoscopy
and often causes only slight structural alterations, although the vocal repercussions
can be considerable.[2]
[6]
[7]
[8] Videolaryngostroboscopy can help assess a larynx with sulcus vocalis, showing a
decline or absence of mucosal wave vibration.[1]
[9] However, under some circumstances, an accurate diagnosis of the sulcus vocalis can
only be obtained by suspension microlaryngoscopy, the gold standard for diagnosing
minimal structural changes. It is applied exceptionally because of its invasive nature
and the fact that the procedure is performed under general anesthesia.[8]
[9] Suspension microlaryngoscopy makes it possible to assess vocal cord details under
binocular microscopy at depth and with good lighting, enabling the use of instruments
for palpating vocal cord alterations and providing an important contribution to sulcus
vocalis diagnosis.[8]
[9]
With respect to characterizing visual laryngeal, auditory perception and acoustic
attributes, studies performed with symptomatic individuals show that most vocal sulci
are bilateral, with types II and III being the most common.[5]
[10]
[11]
[12] The most marked vocal characteristic of this lesion is breathlessness, which results
from incomplete glottal closure. Another vocal parameter is roughness, due to the
decline in mucosal wave vibration in the vocal cords.[1]
[2]
[7]
[12] In regard to the acoustic characteristics of voice, parameters such as fundamental
voice frequency, jitter, and shimmer were altered.[1]
[12]
However, it is important to emphasize that voice assessment studies in individuals
with sulcus vocalis[5]
[9]
[10]
[11]
[12]
[13]
[14]
[15] generally select a symptomatic population, excluding possible subjects with sulcus
that did not display voice symptoms. As such, the aim of the present study was to
characterize the larynx and voice of asymptomatic adults with sulcus vocalis from
the standpoint of laryngeal, auditory perception, and acoustic assessment, in addition
to voice self-evaluation.
Method
This is a cross-sectional observational study, conducted in the otolaryngology department
of a public hospital in Pernambuco state, Brazil.
After approval was obtained from the institutional research committee, under protocol
number 973.637, and the subjects gave their informed consent, data collection occurred
between January and December 2014.
The initial sample, selected consecutively by convenience, consisted of 77 adults
with no vocal complaints, submitted to general anasthesia for surgery at the extralaryngeal
site, extraneous to the study. The subjects were submitted to the following surgeries:
tonsillectomies, septoplasties, turbinectomies and/or sinusectomies. After exclusion
criteria were applied, the number of patients declined to 71. Suspension microlaryngoscopy
was conducted, revealing 13 individuals with sulcus vocalis (group 1). Among the remaining
subjects, 13 gender-matched controls with no laryngeal alterations were selected consecutively
(group 2), totaling 26 study participants. Each group consisted of nine women and
four men.
Excluded from the study were patients submitted to surgery with high anesthetic risk
(above ASA III); endotracheal intubation or previous laryngeal surgery; history of
cervical trauma; extrinsic laryngeal aggression factors, including the prolonged use
of inhalatory costocorticoids, smoking and occupational respiratory diseases, contraindication
for suspension laryngoscopy; trauma from orotracheal intubation; presence of phonotraumatic
lesions identified during the examination; and incomplete laryngeal exposure during
the procedure.
Suspension microlaryngoscopy was conducted by an otalaryngologist (larynx specialist)
using a Zeiss microscope equipped with a 12.5 occular lens and 400 mm objective lens
with 25X magnification, without causing stress on the vocal cords. The procedure involves
placing the microlaryngoscope between the upper and lower teeth, over the tongue and
down the throat to allow a good view of the larynx and vocal cords. The microlaryngoscope
is a hollow metal tube with a fiber optic light. There was no surgical intervention
aimed at altering the larynx, irrespective of vocal cord examination findings. All
laryngeal examinations were video recorded for later reassessment. The sulcus vocalis
were described according to Ford et al (1996).[5]
All the participants underwent the following voice evaluatiosymptoms scale (VSS),
to ensure that all the participants were asymptomatic; auditory perception evaluation
of the voice, with vocal assessment using the grade, roughness, breathiness, asthenia,
strain, instability (GRBASI) scale; and acoustic evaluation of the voice applying
the VOXMETRIA program (CTS Informática, Pato Branco, Paraná, Brazil). A sample characterization
questionnaire was conducted before the vocal assessment. All the procedures were performed
a minimum of 15 days after surgery.
The VSS is an instrument adapted and validated for Brazil.[16] It self-assesses voice and vocal symptoms, via 30 questions divided into three domains,
collecting information on functionality (15 questions), emotional impact (8 questions)
and physical symptoms (7 questions) that a voice disorder can cause. Subjects responded
individually to the scale questions and each answer was scored from 0 to 4, according
to the frequency reported: (0) never, (1) rarely, (2) sometimes, (3) almost always,
(4) always. The scores were used to determine the participants' level of vocal alteration.
For auditory perception and vocal acoustics, samples of the subjects' voices were
recorded. All the tasks were executed with the patients comfortably seated in a quiet
room, where voices were recorded individually. The vocal data for auditory perception
and acoustic analysis were recorded using the Fonoview (CTS Informática) and Voxmetria
software (CTS Informática), respectively, in an HP Intel Core i5 2.5 GHz 4096 MB laptop.
The voices were captured with a Karsect HT-9 microphone placed four centimeters from
the speaker's mouth at a 45° angle. In addition, an Andrea PureAudio USB adaptor was
connected to the laptop to reduce background noise.
For auditory perception data collection, the tasks selected were sustained emission
of the vowels /a/ and /i/ and counting from one to ten. To determine vocal parameters,
the GRBASI scale, proposed by Hirano (1981) and complemented with Dejonckere's “I”
parameter (1996) was applied. This scale analyzes the following aspects of vocal quality:
voice roughness (R), breathlessness (B), asthenia (A), stress (S) and instability
(I), which, taken together, determine the overall degree of hoarseness (G). Each of
these aspects can be classified on a severity scale from 0 to 3, where 0 represents
no change; 1 slightly changed; 2 moderately changed and 3 significantly changed.
Auditory perception of voices was evaluated by two speech therapists specialized in
voice assessment, with more than 15 years' experience. To determine inter-rater agreement,
30% of the voices were randomly repeated for a total of 34 voices. The results obtained
from the evaluator with the highest index of reliability were selected for analysis.
For acoustic recording of the voices of the participants using the Voxmetria (CTS
Informática) software, subjects were instructed to emit the vowel /e/ and count from
1 to 10. The following parameters were investigated: a) fundamental frequency; b)
vocal intensity; c) irregularity d) jitter; e) shimmer; and f) glottal noise excitation ratio (GNE). The acoustic data were supplied
by the program itself.
Vocal self-assessment, auditory perception and the acoustic data of groups 1 and 2
were submitted to descriptive analysis using absolute and percentage frequencies for
the categorical variables and means and standard deviation for the numerical variables.
Pearson chi-squared or Fisher Exact test were applied to determine whether there was
an intergroup difference in the categoriacal variables and the Student t or Mann-Whitney test to compare the numerical variables. Fisher Exact test rather
than Pearson chi-squared was used when the condition to apply the latter was not present.
The Student t-test was selected when the hypothesis of data normality was confirmed in both groups,
while the Mann-Whitney test was used when the data were not normally distributed.
Data normality was determined by the Shapiro-Wilk test and equality of variance by
Levene test.
Cohen Kappa Statistic was used to analyze inter-rater agreement, considering the classification
proposed by Landis & Koch, as follows: (a): almost perfect: kappa between 0.80 and
1.00; (b): substantial: kappa between 0.60 and 0.80; (c): moderate: kappa between
0.40 and 0.60; (d): fair: kappa betweeen 0.20 and 0.40; (e): slight: kappa between
zero and 0.20; (f): poor: kappa between -1 and zero. The margin of error used in the
statistical tests was 5%. The data were entered into an Excel (Microsoft Corp. Redmond,
WA, USA) spreadsheet and the Statistical Package for the Social Sciences (SPSS) version
21 (IBM Corp., Armonk, NY, USA) was used to obtain the statistical calculations.
Results
The age of the participants varied between 24 and 66 years, with an average of 41.88
years. Half were aged between 24 and 40 years and the other half between 41 and 66
years; a majority (69.2%) were women. Only two individuals (7%) were voice professionals,
one each from group 1 and 2.
Group 1 consisted of individuals with sulcus vocalis and group 2 without the disorder.
Of the 26 vocal cords studied in group 1, 23 exhibited sulci vocalis. Of these, 18
(78%) were type I and 5 (22%) type II. Furthermore, most of the individuals with sulcus
vocalis (77%) were affected bilaterally (n = 10).
[Table 1] illustrates the mean VSS values, and the standard deviation. There was no statistically
significant intergroup difference (p > 0.05). The values observed for each individual were below 16 points, when all the
domains were added. This assessment ensured that none of the participants displayed
vocal symptoms.
Table 1
Means and standard deviations of the vocal symptoms scale values obtained
|
Variable
|
Group 1 Mean (standard deviation)
|
Group 2 Mean (standard deviation)
|
P-value
|
|
• VSS
|
6.38 (2.29)
|
8.46 (3.77)
|
0.148[*]
|
Abbreviation: VSS, vocal symptoms scale.
* Mann-Whitney test.
[Table 2] shows the auditory perception results obtained, considering each parameter on the
GRBASI scale, according to the group analyzed. In group 1, 69.2% of the individuals
displayed mild overall vocal alteration (G), and 61.5% mild roughness (R). In group
2, 15.4% showed mild overall vocal alteration (G) and roughness (R). Intergroup comparison
revealed a significant difference (p < 0.05) in relation to the overall degree of vocal alteration (G) and roughness (R).
Table 2
Numerical and percentage data of group 1 and 2 subjects with normal and altered auditory
perception vocal parameters
|
Group
|
|
|
|
Variable
|
Group 1
|
Group 2
|
Group Total
|
P-value
|
|
N
|
%
|
N
|
%
|
N
|
%
|
|
|
TOTAL
|
13
|
100.0
|
13
|
100.0
|
26
|
100.0
|
|
|
• G
|
|
|
|
|
|
|
|
|
Normal
|
4
|
30.8
|
11
|
84.6
|
15
|
57.7
|
p
[a] = 0.005*
|
|
Overall
|
9
|
69.2
|
2
|
15.4
|
11
|
42.3
|
|
|
• R
|
|
|
|
|
|
|
|
|
Normal
|
5
|
38.5
|
11
|
84.6
|
16
|
61.5
|
p
[a] = 0.016*
|
|
Overall
|
8
|
61.5
|
2
|
15.4
|
10
|
38.5
|
|
|
• B
|
|
|
|
|
|
|
|
|
Normal
|
12
|
92.3
|
13
|
100.0
|
25
|
96.2
|
p
[b] = 1,000
|
|
Overall
|
1
|
7.7
|
−
|
−
|
1
|
3.8
|
|
|
• A
|
|
|
|
|
|
|
|
|
Normal
|
13
|
100.0
|
13
|
100.0
|
26
|
100.0
|
**
|
|
Overall
|
−
|
−
|
−
|
−
|
−
|
−
|
|
|
• S
|
|
|
|
|
|
|
|
|
Normal
|
12
|
92.3
|
12
|
92.3
|
24
|
92.3
|
p
[b] = 1,000
|
|
Overall
|
1
|
7.7
|
1
|
7.7
|
2
|
7.7
|
|
|
• I
|
|
|
|
|
|
|
|
|
Normal
|
13
|
100.0
|
13
|
100.0
|
26
|
100.0
|
**
|
|
Overall
|
−
|
−
|
−
|
−
|
−
|
−
|
|
*Significant difference at the 5.0% level.
**Could not be determined due to the presence of only one category.
a Through Pearson Chi-square test.
b Using Fisher exact test.
The weighted kappa index values of inter-rater agreement analysis on the GRBASI auditory
perception scale were 0.81 (group I) and 0.82 (group II) for evaluator 1, and 0.79
(group I) and 0.80 (group II) for evaluator 2. In this analysis, almost perfect agreement
was obtained for evaluator 1 and substantial for evaluator 2, according to the Landis
& Koch classification. As such, the former's analysis was considered.
[Table 3] shows the absolute number of group 1 and 2 individuals with normal and altered values
in the acoustic assessment parameters. Most of the individuals in both groups obtained
normal acoustic values.
Table 3
Numerical data of group 1 and 2 individuals with normal and altered values in the
acoustic assessment parameters
|
Parameters
|
Group 1
|
Group 2
|
|
Normal
|
Altered
|
Normal
|
Altered
|
|
Fundamental frequency
|
13
|
0
|
13
|
0
|
|
Intensity
|
10
|
03
|
11
|
02
|
|
Irregularity
|
10
|
03
|
11
|
02
|
|
Shimmer
|
10
|
03
|
11
|
02
|
|
Jitter
|
10
|
03
|
10
|
03
|
|
GNE ratio
|
09
|
04
|
08
|
05
|
Abbreviation: GNE, glottal-to-noise excitation.
The average acoustic parameter values in [Table 4] show that the means were higher in group 1 in vocal intensity, irregularity, shimmer
and GNE ratio. Mean jitter was higher in group 2. Average fundamental frequency was
higher in group 1 men, while the opposite was found for women. Furthermore, mean fundamental
frequency was higher in women. However, when compared statistically, there was no
significant intergroup difference (p > 0.05), considering all the acoustic parameters analyzed.
Table 4
Mean values and standard deviation of fundamental frequency, intensity, irregularity,
shimmer, jitter and glottal-to-noise excitation ratio per group
|
Group
|
|
|
|
Variable
|
Group 1
|
Group 2
|
Group total
|
P-value
|
|
Mean ± SD (Median)
|
Mean ± SD (Median)
|
Mean ± SD (Median)
|
|
|
• Frequency (male)
|
101.48 ± 7.44
|
98.68 ± 9.67
|
100.08 ± 8.13
|
p
[b] = 0.886
|
|
• Frequency (female)
|
194.46 ± 8.96
|
202.21 ± 17.75
|
198.34 ± 14.21
|
p
[b] = 0.077
|
|
• Intensity
|
60.07 ± 3.53 (59.87)
|
58.85 ± 3.39 (59,23)
|
59.46 ± 3.45 (59.82)
|
p
[a] = 0.337
|
|
• Irregularity
|
3.48 ± 1.43 (3.45)
|
3.10 ± 1.29 (2.89)
|
3.29 ± 1.35 (3.13)
|
p
[a] = 0.485
|
|
• Shimmer
|
4.56 ± 2.04 (4.38)
|
3.96 ± 2.11 (4,56)
|
4.26 ± 2.06 (4.47)
|
p
[a] = 0.469
|
|
• Jitter
|
0.44 ± 0.36 (0,24)
|
0.48 ± 0.33 (0.47)
|
0.46 ± 0.34 (0.46)
|
p
[b] = 0.663
|
|
• GNE ratio
|
0.63 ± 0.20 (0.67)
|
0.57 ± 0.27 (0.67)
|
0.60 ± 0.24 (0.67)
|
p
[a] = 0.580
|
Abbreviations: GNE, glottal-to-noise excitation; SD, standard deviation.
a Through the t-Student test with equal variances.
b Through the Mann-Whitney test.
Discussion
Of the 13 individuals (26 vocal cords) with sulcus vocalis, the vast majority were
type I, with type II being far less frequent. There were no vocal cords with sulcus
type III. Furthermore, most individuals with sulcus were affected bilaterally. The
literature shows a predominance of bilateral sulcus, with most being type II or III.[5]
[7]
[12]
[13]
[14] The predominance of type I sulci in the present study may be related to the fact
that only individuals from the general population with no vocal complaints were selected.
According to Ford,[5] type I sulcus is located on the surface layer of the lamina propria, where structural
damage to the mucosa is minimal, with no increase in stiffness or impact on vocal
quality. By contrast, literature studies[5]
[7]
[12]
[13]
[14] assessed individuals with voice complaints, which may explain the prevalence of
type II and III sulci, resulting in greater damage to the vocal cord of the lamina
propria.
In relation to vocal symptoms, none of the VSS scale values ([Table 1]) indicated hoarseness in the subjects of the present study, or significant intergroup
differences. Furthermore, the total VSS value for each participant was below 16 points.
As such, this population exhibited no vocal symptoms. According to Moreti et al (2014),[16] who validated the VSS for Brazilian Portuguese, the cutoff point for vocal symptoms
is 16. Values greater than 16 suggest some degree of hoarseness and those below 16
no vocal symptoms.
With respect to the lack of voice-related symptoms in group 1 individuals, since most
were not voice professionals and did not use strain their voice, they were less likely
to overload their vocal apparatus. Moreover, the degree of required vocal quality,
as well as self-perceived vocal disadvantage, tend to be lower in the general population
than in voice professionals.[17]
[18] Given that voice professionals face significant vocal demands and risks, and that
even slight hoarseness can limit good performance, it is hoped that this population
report sulcus vocalis-related problems as soon as possible, in contrast to the group
under study.
In relation to the auditory perception characteristics of group 1, eight of the 13
individuals with sulcus vocalis exhibited mild roughness. Only one individual displayed
mild breathlessness ([Table 2]). This result contradicts literature findings,[5]
[6]
[7]
[10]
[11]
[12] in which breathlessness is the primary auditory perception alteration in patients
with sulcus vocalis. Hirano et al (1990)[11] assessed 126 patients with sulcus vocalis and most of the individuals exhibited
mild breathlessness and hoarseness. The results indicated that voice quality was more
correlated with glottis incompetence than vocal cord stiffness. Since it was a retrospective
study of individuals with vocal complaints examined by videolaryngoscopy, the sulci
detected would likely be more pronounced with a more evident vocal impact, which would
explain the higher incidence of breathlessness.
Other studies of symptomatic patients also showed a predominance of breathlessness
in subjects with sulcus vocalis, in addition to the presence of roughness in some
cases. The authors also agree that breathlessness is related to glottis incompetence
and stiffness in the lamina propria of the vocal cords.[1]
[19] Bouchayer et al (1988)[20] reported that although sulcus vocalis is a benign condition, it has a dramatic impact
on the voice, and the resulting vocal quality can be considered typical, not only
breathlessness, but especially the rough, veiled monotone and reduced loudness, with
limited harmonics and lack of projection imposed by the restricted muco-undulatory
movement of the vocal cords.
Given these literature findings, contradicting those obtained here, in which individuals
with sulcus vocalis exhibited mild roughness, it is important to underscore that 78%
of group 1 individuals consisted of patients with type 1 sulci, which are generally
shallow, exerting no significant impact on glottic closure or the voice. In addition,
sulcus vocalis affects a part of the population with no vocal complaints, whereby
the impact on the voice depends on the type and magnitude of the sulcus vocalis as
well as the vocal demand the individual is submitted to.[1]
[2]
[8] The minimal structural alteration of the larynx present since birth can manifest
themselves in the first sounds an infant makes or in adulthood depending on vocal
demands, irritative factors and laryngeal development itself.[1]
[2]
[21]
Intergroup comparison in terms of auditory perception assessment revealed that individuals
with sulcus vocalis obtained lower scores, with a statistically significant difference
in relation to group 2, in overall hoarseness (G) and roughness (R), both exhibiting
a mild level. The presence of roughness in group 1 individuals is related to vibratory
irregularity in the mucosal wave of the vocal cords. Some authors[1]
[6]
[11] report that sulcus vocalis may exhibit different levels of vibratory irregularity
in the mucosal wave, when different layers of the lamina propria of the vocal cords
are affected.[4]
[7] Ushijima et al (1986)
[22] considered that the sulcus vocalis is related to persistent hoarseness due to insufficient
glottic closure during phonation. Other authors[2]
[4]
[6] found that the impact is minimal in type 1 sulcus vocalis, because only the surface
layer of the lamina propria is affected, often not perceived by the individuals who
exhibit mild roughness.[1]
With respect to acoustic assessment, in both groups 1 and 2, all the individuals showed
normal voice frequencies, with no significant intergroup differences ([Table 3]). The normal distribution range for male voices is between 80 and 150 Hz, while
for females it varies from 150 to 250 Hz.[1]
[23]
[24] Several studies found alterations in fundamental frequency in individuals with sulcus
vocalis, often leading to acute frequencies.[6]
[10]
[25] However, the samples of these studies consisted of subjects with type II or Type
III sulcus, likely with vocal cords that exhibited important structural alterations.
In the present study, most of the sulci were type I, with minimal structural alteration
of the mucosa and no increase in stiffness or impact on the fundamental frequency.
These results corroborate those reported by Lim et al (2009),[6] who assessed individuals with type I sulcus vocalis and found normal frequency values.
Intensity is directly related to subglottic pressure of the air column, which depends
on factors such as amplitude of the vibration and stress on the vocal cords, more
specifically glottic resistance.[1]
[26] With respect to this parameter, normal mean values were observed for both groups,
with no significant differences between them ([Table 4]). Considering that individuals in the present study with sulcus vocalis exhibited
minimal structural alterations to their vocal cords with no impact on glottic closure,
no change in subglottic air pressure or voice intensity is expected.
The parameter irregularity is related to glottic coaptation and quantifies irregularity
of vocal cord vibratory cycles.[1]
[27] In the present study, the average values were normal for both groups, with no significant
differences between them.
In relation to shimmer, the individuals with sulci vocalis displayed normal values
and no significant intergroup differences were observed. Shimmer indicates the variability
in sound wave amplitude, that is, irregular alterations in the amplitude of glottic
cycles, from one to another.[1]
[5]
[11] Since the individuals studied here likely showed no decline in glottic resistance
or mass lesion, according to the literature,[1]
[28] they may experience alterations in shimmer values, thereby explaining the fact that
most of the values were normal.
In regard to jitter, the means obtained in groups 1 and 2 were normal. Jitter showed
variable fundamental frequency and how much a period is different from its predecessor
or immediate successor. Furthermore, alterations occur due to the lack of vocal cord
vibration control, often correlated with roughness.[1]
[5]
[11] The results of the present study demonstrated that the changes found did not cause
an increase in vocal cord vibration periodicity, which is reflected in higher jitter
values.[1] The type of sulcus found does not result in significant damage to the vocal cord
mucosa.
With respect to the jitter and shimmer data obtained in this study, it is important
to underscore the findings of Yilmaz,[15] who studied the acoustic data of 44 patients with sulcus vocalis. In his study,
patients exhibited changes in several acoustic parameters (jitter, shimmer, and fundamental
frequency), without characterizing the type of sulcus vocalis. It is important to
emphasize, however, that since this study assessed a sulcus excision technique associated
with vocal cord medicalization, the population analyzed displayed intense vocal complaints
and sulci vocalis with greater structural vocal cord alterations.[29]
[30]
[31]
Glottal-to-noise excitation is an acoustic measure that calculates the noise produced
by vocal cord oscillation, indicating that the vocal signal originates in vocal cord
vibrations or the turbulent air current produced in the vocal tract.[32] The mean GNE obtained in group 1 and 2 revealed normal values, with no significant
intergroup differences. According to the literature, since the GNE is related to breathlessness,
the normal average values can be explained, since roughness was the only parameter
that stood out in the individuals assessed (predominant in group 1). According to
Madazio et al (2009),[33] strained and adapted voices may exhibit normal mean GNE values.
In regard to the difference in auditory perception and acoustic data, assessment of
the former considers both source and filter-related data, which could, in some situations,
change the overall impression of voice. It is known that correlations between auditory
perception and acoustic data do not always exist.[1]
According to Pontes,[2] a larynx with sulcus vocalis or other minimal structural alterations (MSA) can remain
balanced and adapted to the vocal demand of speakers without compromising them for
the rest of their life. The slight vocal alterations observed in individuals with
sulcus vocalis reinforce the hypothesis that its vocal impact may be minimal or nonexistent,
but these slight vocal deviations can be detected by voice specialists. Therefore,
alterations in the vocal quality of individuals with sulcus is far greater than that
traditionally described in the literature, since, in addition to symptomatic patients
with pronounced sulci and severe hoarseness, where roughness and breathlessness predominate,
there is also a much larger population of asymptomatic individuals with sulcus stria
minor that may display minimum alterations in voice quality.[34] This sample clearly demonstrates the possibility of classifying one of the most
frequent MSAs (sulcus vocalis) as an anatomical variation (morphological alteration
in which the function of the organ is not compromised) or a representative entity
of the set of laryngeal abnormalities, since in certain situations, this lesion promotes
phonatory deviation.
Conclusion
Type I sulcus vocalis is predominant in individuals with no voice complaints, who
may exhibit slight changes in vocal quality, characterized by roughness, or no voice
alterations whatsoever.
