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A comparison of four clinical techniques in the analysis of phonation
Journal of Voice
Vol. 4, No. 3, pp. 198-204 © 1990 Raven Press, Ltd., New York
A Comparison of Four Clinical Techniques in the Analysis of Phonation *David P. Hill, *Arlen D. Meyers, and *'?Ronald C. Scherer *Department of Otolaryngology/Head and Neck Surgery, University of Colorado Health Sciences Center; 7"The Recording and Research Center, The Denver Center for the Performing Arts, Denver, Colorado, U.S.A.
Summary: The success of four clinical techniques for voice analysis were compared: videolaryngoscopy, videolaryngostroboscopy (VLS), electroglottography (EGG) for laryngeal adduction, and acoustic perturbation analysis. Two normal and 26 consecutive voice patients were studied. All four techniques were successful with the normals and 42% of the patients. There were difficulties for 23% of the patients for the stroboscopic technique, 46% for the EGG analysis, and 35% for acoustic analysis. These difficulties were due primarily to aperiodicity of the voice signals or, in the case of stroboscopy, to the inability to view the vocal folds because of hypertrophy of tissue. Videolaryngoscopy failed only once due to intolerance by the patient. For the 28 subjects, only three (11%) could not be analyzed by either VLS, EGG, or acoustic techniques. There was a moderate correspondence between VLS and EGG analysis for the estimate of glottal adduction. The results strongly suggest the complementary and overlapping interpretations of these measures and, thus, the usefulness of the battery for clinical voice analysis. Key Words: Videolaryngoscopy--Videolaryngostroboscopy (VLS)--Acoustic analysis-Electroglottography (EGG)--Mucosal w a v e - - L a r y n x - - A d d u c t i o n - Abduction--Abduction quotient--Perturbation--Vocal cord--Vocal fold--Phonation--GLIMPES.
For many years, otolaryngologists and their patients have benefitted from visual diagnosis of many laryngeal disorders using a laryngeal mirror. Clinical application of indirect laryngoscopy with rigid and flexible laryngoscopes added a further dimension to the clinical evaluation of laryngeal disorders. The rapid movement of the vocal folds, however, has remained a limiting factor in the successful e v a l u a t i o n of m a n y f u n c t i o n a l vocal fold abnormalities. Over the past 10 years, several tech-
niques for the evaluation of vocal fold movement have been refined, and some have the potential to become simple, safe, and economic means for objective evaluation. Some of these techniques include videolaryngostroboscopy (VLS) (1), electroglottography (EGG) (2), photoglottography (PGG) (3), electromyography (EMG) (4), and acoustic analysis (5). Several recent studies have evaluated the clinical usefulness of some of these techniques. Trapp and Burke (6) studied the correlation of photoglottography and electroglottography with VLS in an in vivo canine model. They noted that the PGG and EGG waveforms were distinctly different between the simulated unilateral recurrent nerve paralysis and the superior laryngeal nerve paralysis. Hanson et al. (7) compared PGG and EGG measures in hu-
Address correspondence and reprint requests to Dr. D. P. Hill at Department of Otolaryngology/Head and Neck Surgery, University of Colorado Health Sciences Center, Box B-210, 4200 East Ninth Avenue, Denver, CO 80262, U.S.A. Presented at the Seventeenth Annual Symposium: Care of the Professional Voice, sponsored by the Voice Foundation, New York City, June 9, 1988.
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CLINICAL A N A L YSIS OF P H O N A T I O N
rnans having unilateral recurrent, superior, and idiopathic laryngeal paralysis and found that the PGG waveshapes differentiated between different categories of paralysis. Anastaplo and Karnell (8) studied four normal adult subjects with a split screen technique that simultaneously displays EGG waveform and videostroboscopic images. They further validated the relationship between the EGG waveform and glottic opening, showing that the " k n e e " (a point of discontinuity between two slopes on the EGG waveform) usually reflects the separation of the superior surface of the vocal folds in normal individuals. Measures of laryngeal adduction have been studied recently (9-12). Titze (9) developed a computer program called " G L I M P E S " (Glottal Imaging by Processing External Signals) that analyzes EGG recordings to predict laryngeal configuration and dynamic vocal fold motion. A laryngeal abduction measure is obtained from that analysis. GLIMPES also performs a number of perturbation analyses on recorded signals.
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The goal of the present study was to compare the success of obtaining information about laryngeal function among four techniques: constant light flexible videolaryngoscopy, videolaryngostroboscopy, laryngeal abduction via GLIMPES, and acoustic perturbation analysis via GLIMPES. These techniques and analyses are useful in determining laryngeal function, relatively easy to administer, and relatively noninvasive. MATERIALS AND METHODS Voice evaluation was performed for two normal subjects and 26 patients who were consecutively referred to the Center for Voice Disorders at the University of Colorado Health Sciences Center. Patient pathology varied from mild to severe dysfunction (Table 1). VLS was performed first. The patient was locally anesthetized with a topical oral preparation of 4% lidocaine spray and was placed in the examining chair (Fig. 1). VLS was performed using a Panasonic Color Video Camera model WV-F2, a Pana-
TABLE 1. List o f the 28 subjects evaluated with videolaryngoscopy, VLS, Qa, and acoustic perturbation analysis a Age
Sex
DH JA AS PB 1 VD HK GB
30 30 43 39 32 48 69
M
X
X
F F F F M M
X X X X X X
X X X X X X
8
SH
40
M
X
X
X
X
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
JS JK PB2 ME HF GH PG SA CC AF FS EC Jp FB WP BK BM RW PW DV
65 30 30 68 68 58 38 58 63 62 55 67 77 67 58 60 65 69 68 49
M M M F M M F M M
X X X X X O X X X
X X X X X O O O O
X X X X X X O/X O/O O/O
X X X X X X X O O
M
X
O
X
X
M M M M M M M M M M
X X X X X X X X X X
O X X X X X X X X X
O/O O/O O/O O/O O/O O/O O/X O/X O/X X
O O O O O O X X X O
1
2 3 4 5 6 7
Video
Strobe
Q,/EGG b
Subject
Perturbation
Diagnosis
X
X
X X X X X X
X X X X X X
Normal subject Normal, small postchink Dystonia Left arytenoid trauma, stridor Right partial paretic TVC Right vocal process granuloma Parkinson's, bowing Bilateral leukoplakia T1 cancer, XRT Surgery to tongue, XRT Tension dysph, ant chink Tension dysphonia Supraglottal fatigue Tension dysphonia Tension dysph, hyperadd T1 cancer, XRT, edema Hypertrophy false cords Bowing right TVC, fluids Left TVC atrophy, aphonic Aphonic, post chink Left TVC paralysis Right hemilaryng, teflon, T2 Right hemil, false fold phon. T1 cancer, XRT Spastic dysphonia Glottic slit, fluids Hoarse, tight larynx Multiple sclerosis
Also included is a subjective technique of judging adduction by viewing the EGG waveshape. b The first X or O refers to success or failure, respectively, of the software to produce a Qa value. The second X or O refers to the judgment of degree of adduction by viewing the EGG waveshape (X) or the inability to judge adduction from the EGG waveshape (O). X, the technique was successful; O, the technique could not be used successfully. Age, sex, and basic diagnoses are included. T1, tumor confined to vocal cord(s) with normal cord mobility; XRT, radiation therapy; T2, supraglottal or subglottal extension of tumor.
Journal of Voice, Vol. 4, No. 3, 1990
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FIG. 1. A sketch of the VLS exam. The examiner is holding the videocamera, using a flexible fiberoptic laryngoscope, and the patient or an assistant is holding the stethoscope on the neck to transduce the frequency of phonation. The foot pedal is used to key the direct or strobe light source. B&K, Bruel and Kjaer stroboscope type 4914.
sonic VCR model AG-1950, Olympus ENF type P flexible fiberoptic nasendoscope, a high-resolution Sony Color Video Monitor, and a Bruel and Kjaer Rhinolarynx Stroboscope type 4914. Videotapes of the exams were subjectively scored by the authors for the following categories: symmetry of vocal fold movement, amplitude of lateral movement, periodicity of mucosal wave motion, characteristics of the mucosal wave along the length of the cords, and closure during the phonatory cycle (13). Symmetry of vocal fold movement was broken down into the following categories: always, usually, episodically, and never symmetric. Asymmetry was then further broken down in terms of the differences in vertical or lateral position at rest and during phonation. Amplitude of lateral movement was categorized as great, normal, small, and absent. Each patient was also given a rating for consistency of amplitude over many cycles. Periodicity of vocal fold movement was scored in terms of cycle to cycle variability, and consistency of cycle period over many cycles, as seen on the stroboscopic image. This was not a direct measure of acoustic periodicity. Mucosal wave motion of the superior surface of the vocal fold was graded as great, normal, small, and absent. Consistency of the mucosal movement over time was also noted. Abnormal mucosal motion was further characterized by its location on the fold: anterior, middle, posterior third, or the entire fold. Journal of Voice, Vol. 4, No. 3, 1990
Closure was measured on a nominal scale: " o n e " meant pressed, " t w o " normal adduction, "three" a mild posterior or anterior chink, " f o u r " a moderate to large posterior chink or hourglass-shape glottis, "five" bowed cords, and "six" a glottal slit or chink the length of the cords. Of the 11 judgments, all three of the authors agreed 90% of the time, and two of the three agreed 95% of the time. The judgments differing across the three judges (5%) were excluded from further consideration. The patient was also taken to a recording station (14) (Fig. 2) and seated in a double-walled sound booth. An EGG electrode was placed against each side of the anterior neck over the thyroid laminae, and a third reference electrode was placed on the side of the neck. The patient was asked to remain a constant distance from the microphone. The initial mouth-to-microphone distance was measured at 12 in, b u t t h e r e was no n e e d to k e e p mouthto-microphone distance constant across subjects in this experiment. The patient was instructed to say 15 prolonged/a/vowels at a comfortable pitch and loudness, trying to keep the sound as steady as possible. Each phonation or "token" was - 3 s in duration. The patient also read several standard passages and performed maneuvers to evaluate vocal range and fundamental frequency during reading. Acoustic recordings were made using a Realistic Cardioid Microphone, an ATI M-1000 Precision Dual Microphone Preamplifier, and an AKG Acoustic Amplifier. EGG recordings were made using a Synchrovoice Research Electroglottograph. The simultaneous EGG and acoustic signals produced by the patient were digitized, multiplexed, and video encoded within a Sony Digital PCM
FIG. 2. A sketch of a GLIMPES recording station. The EGG and acoustic signals are digitized and recorded on half-inch videotape.
CLINICAL A N A L YSIS OF P H O N A T I O N
model 501ES and recorded onto a Magnavox VCR. The videotapes were sent to The Recording and Research Center of The Denver Center for the Performing Arts for analysis on a VAX 11/750 computer. A report form with perturbation measures (from the acoustic signal) and abduction measures (from the EGG signal) as well as a subjective analysis of both acoustic and EGG measures and waveforms (12) by a voice scientist was returned to the otolaryngology clinic. This arrangement made these evaluation techniques feasible in the clinic setting. ABDUCTION ANALYSIS The EGG signal was analyzed through an analysis-synthesis scheme within GLIMPES. The abduction quotient (Q~) was obtained for five consecutive cycles within approximately the center position of each token. Qa is defined (9) as the ratio of the half-distance between the vocal processes to the amplitude of vibration of (one of) the vocal folds. This parameter would increase if vocal process separation increased or vocal fold amplitude decreased. Excised canine larynx and human studies verify Qa as a useful measure of glottal abduction (12). 1 Values of Qa < - 1 . 0 suggest hyperadduction and >0.5 suggest hypoadduction (12). ACOUSTIC ANALYSIS Perturbation analysis was performed on 100 consecutive cycles within each of the 15 tokens of the microphone signal. Four perturbation measures (12) were obtained for the prolonged/a/microphone recordings: the coefficient of variation for frequency (CVF) and jitter are measures of the stability of signal fundamental frequency, and the coefficient of variation for amplitude (CVA) and shimmer are measures of the stability of signal amplitude. Jitter and shimmer are measures of adjacent cycle perturbation, and CVF and C V A are related to the calculation of the standard deviation of cycle frequency and amplitude, respectively (12). Short-term instai Qa was tested with seven normal actor subjects who imitated very breathy, normal, and very pressed (or constricted) voice qualities. Qa values were consistent with greater abduction of the Vocal processes for the breathy tokens and greater adduction for the pressed tokens. The decision of hypo- or hyperadduction based on the Q~ value for clinical and research purposes is conservative in that the Qa value must exceed one-half standard deviation beyond the mean for very breathy or the very pressed tokens. Further information on the validity and application of the abduction quotient can be found elsewhere (12).
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bility, shown as relatively high values for jitter and shimmer, are most likely associated with laryngeal tissue abnormalities, fast-acting neuromuscular fluctuations, or asymmetry of movement (12). Longer-term instability, reflected as relatively high numbers for CVA and CVF, suggest relatively slow fluctuations of amplitude or frequency, respectively (12). RESULTS Table 1 gives a list of the subjects, basic diagnoses, and success or failure of the four techniques, videolaryngoscopy, VLS, Qa, and acoustic perturbation (jitter, shimmer, and coefficients of variation for amplitude and frequency). A technique was successfully administered when the recordings and data obtained appeared reliable and valid. Also included in the table with Qa is the additional "technique" of judging laryngeal adduction strictly by viewing the EGG waveshape when Qa w a s not available. The first two subjects in Table 1 were normal controls for whom all four techniques were successful. The next 26 subjects were patients. All four techniques were successful for 11 of the 26 patients (42%), representing a wide range of diagnoses. Two examples of this group follow. Case 1: JA was a 30-year-old normal woman with a physiologic posterior glottic chink on videolaryngoscopy, and normal glottic symmetry, amplitude, periodicity, and mucosal wave on VLS. She had no complaints. The Q~ and acoustic measures were all normal. Case 2: H K was a 48-year-old man with a large contact granuloma arising from the vocal process of the right arytenoid cartilage. His symptoms included throat pain and vocal fatigue after prolonged voice usage, but he did not complain of hoarseness or breathiness. VLS showed complete closure, normal symmetry, amplitude, periodicity, and mucosal wave. The granuloma was not interfering with voice production. Qa and acoustic measures were normal, supporting the findings on VLS. There were difficulties with endoscopy for six (23%) of the patients (patients 14-19 in Table 1). Patient GH could not tolerate the flexible endbscopy procedure. For patients PG, SA, and CC, the glottis was obscured from vision by overhanging swollen arytenoid cartilages or ventricular folds. For AF and FS, the acoustic signal was too aperiodic or the voice too aphonic to permit synchronous flashing of the light source using stroboscopy. Journal of Voice, Vol. 4, No. 3, 1990
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Even though there were difficulties with endoscopy for six patients, for three of them (GH, PG, and AF) the EGG signal was generally helpful in determining relevant adduction information. For the other three patients, the voice was too aperiodic (SA and FS) or the patient could not sustain the/a/ vowel sufficiently long (CC). The case for subject AF is now described. Case 3: AF was a 62-year-old man with bowing of the true vocal cords. Stroboscopic examination was unsuccessful due to copious amounts of secretions in the larynx. CVA, jitter, and shimmer were very high, suggesting either an unstable larynx or (more likely) noise caused by acoustic transients as the glottal airflow passed through the secretions on the vocal folds. Qa was low, suggesting hyperadduction. However, both the bowing and the copious fluid may have altered the EGG waveshape. Interpretation of the Qa values would have to be made with care in this case. There were difficulties in obtaining Qa for 12 (46%) of the patients. For six patients (patients 16 and 19-23 in Table 1), the voice was too aperiodic for EGG analysis. One patient (CC) could not sustain the/aJ vowel long enough for analysis, and one patient (BK) had a voice that was too rough and fry-like for successful EGG analysis. For these patients, the EGG waveform could not be reliably judged by visual inspection. However, for four additional patients for whom the Qa could not be obtained (patients 15 and 25-27 in Table 1), the EGG signal was sufficiently well defined that a judgment could be rendered: For patients PG and BM, the EGG signal was too "wide" for GLIMPES analysis to be successful, but the waveshape strongly suggested hyperadduction. For patient RW, the EGG signal was very "narrow," suggesting wide abduction. Finally, although PW had a noisy EGG signal that prevented GLIMPES analysis, the waveshape was sufficiently intact for a judgment of hyperadduction. These results suggest that the EGG signal is not useful when the voice is too aperiodic, an obvious conclusion, but moreover, frequently can be meaningfully interpreted by visual inspection of waveshape when the software analysis is unsatisfactory. Discussion will now be given for patients SA and BM from this group for which Qa could not be obtained. Case 4: SA was a 58-year-old man who recently underwent radiation therapy for TI cancer of the right true vocal fold. He had been hoarse since the termination of his treatment course 10 months prior to this exam. Videolaryngoscopy revealed Journal of Voice, Vol. 4, No. 3, 1990
that the reason for his hoarseness was swollen arytenoids and false cord phonation. During phonatory tasks, the true vocal folds were completely obscured, and the swollen false cords were in contact, apparently initiating a low glottal fry-like quality. The patient's voice was aperiodic and sounded rough. The acoustic, strobe, and EGG evaluations were not feasible. Case 5: BM was a 65-year-old man with spastic dysphonia. VLS was difficult to perform because the true vocal cords were often obscured by hypopharyngeal constriction. The "best segment" stroboscopic exam revealed symmetric movement most of the time, a small consistent amplitude, normal periodicity, and complete glottic closure. Acoustic "best voice" samples revealed normal cycle-to-cycle variations (normal jitter and shimmer), but very high CVA and CVF, suggesting that the instability of phonation was characterized by a slow variation in frequency and amplitude. The abduction quotient was unattainable because the EGG signal was too wide for analysis by GLIMPES, but the extreme width suggested hyperadduction. These EGG and acoustic findings supported the diagnosis of spastic dysphonia. Table 1 also shows the cases for which there were difficulties in obtaining acoustic perturbation analyses. This occurred for nine (35%) of the patients and was due to nearly aperiodic vocal production (patients 16 and 19-23 in Table 1), inability to prolong the/a/vowel long enough (subject CC), a voice that was too rough and fry-like (BK), and a voice for which transient sounds and apparent double excitations prohibited analysis (DV). Patient FB had a voice that was too noisy for perturbation analysis using GLIMPES. Case 6: FB was a 67-year-old man who underwent right hemilaryngectomy for laryngeal cancer 15 years ago, with subsequent teflon injection into the right laryngeal wall at the level of the left true vocal cord. Phonation could be evaluated with VLS, which showed an irregular, floppy, but effective left true vocal cord (TVC) flapping against the outpouching of tissue caused by the patient's teflon injection. Symmetry was absent, amplitude of the left cord was great, periodicity was consistently irregular, the mucosal wave was irregular, and closure was incomplete with a persistent glottal slit. The voice was very breathy, and the microphone signal was too noisy to allow successful acoustic perturbation analysis with GLIMPES. There were five patients (19%) for which the qualitative video techniques were successful, but the quantitative measures (Qa, perturbation analy-
CLINICAL A N A L YSIS OF PHONATION
ses) were not (patients 20-24 in Table 1). The patients' voices were sufficiently aperiodic that the software was inappropriate or unsuccessful, but not aperiodic enough to prevent stroboscopy from giving some useful information. In contrast, there were two patients (8%) for which stroboscopy was unsuccessful, but Qa and perturbation analyses were successful (patients GH and AF). In these cases, adduction and vocal stability were attributes complementing the absence of stroboscopy. Both the videostroboscopic view of the larynx and analysis of the EGG signal allowed for a judgment of laryngeal adduction. Table 2 gives this comparison for the 16 cases for which both were available (excluding the case of bowed vocal folds, for which the Q~ value may be artificially lowered). The table suggests that there is correspondence between the visual judgment of adduction through VLS and decisions based on GLIMPES analysis (13 cases) and inspection of the EGG signal (three cases). The data were weighted toward relatively normal adduction for both measures. Eleven of the 16 cases were in essential agreement (those along the main diagonal). The other cases are also of interest. Moderate glottal opening (VLS category C), but normal computed adduction (Qa) was the case for the normal female voice (patient JA). This suggests that the VLS technique may underestimate normal limits of glottal abduction within normal subjects, or the abduction quotient may be insensitive to detecting slightly abnormal abduction in otherwise normal subjects. Because conservative limits were placed on deciding hyper- or hypoadduction from the Qa value (12), however, it is also likely that the subject may have produced greater hypoadduction while being scoped than during the acoustic recording (the two procedures were not simultaneous). The case of incomplete closure (category C) with hyperadduction (EGG analysis), a seemingly contradictory finding, sounded breathy but "forced" during
TABLE 2. Comparison between stroboscopic and GLIMPES (9) measures of adduction Visual degree of closure
EGG analysis Hyperadduction Normal adduction Hypoadduction
A
B
C
1 1 0
2 9 0
1 1 1
A, pressed larynx; B, normal closure or small anterior or posterior chink; C, a moderate to large anterior or posterior chink, or glottal separation the length of the glottis.
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the acoustic recordings, suggesting that the glottis may have been closed firmly at the vocal processes but was open between the arytenoid cartilages (at least during the acoustic recordings). One of the two hyperadduction category B cases showed through VLS that the larynx "appeared tight" despite an anterior chink, suggesting that the larynx may have been hyperadducted at the vocal processes, a configuration reflected in the EGG analysis. The case of normal adduction with pressed appearance (category A) was associated with a low normal Qa value. These results suggest that there appears to be an important correspondence between adduction seen via stroboscopy and inferred through the Qa value. Furthermore, the advantage of the Qa value is that it is a quantitative estimate of adduction of the membranous glottis, whereas the advantage of stroboscopy is that it allows viewing the relative closure of the membranous versus the cartilaginous glottis. Both techniques appear to be diagnostically valuable. DISCUSSION The four techniques examined in this report are complementary: Videolaryngoscopy is useful in determining gross structural and tissue characteristics, VLS is useful in determining functional characteristics of vocal fold motion, Qa is a quantitative measure that is strongly related to laryngeal adduction, and acoustic voice measures give quantitative indices of laryngeal stability and help in determining etiology (12). The measures are not completely independent, however: The visual techniques also give indications of adduction (Table 2) and stability. The overlap of information between the visual techniques and the quantitative techniques is of primary usefulness when one or the other is not possible to obtain for a particular patient. However, the acoustic measures are not easily compared to the VLS judgments. The majority of patients with even abnormal acoustic indices had normal appearing periodicity and amplitude on VLS. This is most likely due to the effectively low visual sampling of vibration intrinsic to stroboscopy. This suggests that stroboscopy should be supplemented by more accurate perturbation measures in order to determine laryngeal stability. EGG, acoustic, and stroboscopic measures in this report are all dependent on the periodic or cyclic nature of voice production. Extremely breathy, Journal of Voice, Vol. 4, No. 3, 1990
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hoarse, or diplophonic signals are not successfully analyzed by the software version used for this report (9,12). The usefulness of Qa and acoustic perturbation measures appears to be in analyzing mild to moderate voice dysfunction, and appears to be useful for a wide range of laryngeal abnormalities. CONCLUSION Although videolaryngoscopy is extremely useful in evaluating gross anatomic, morphologic, and tissue changes, and is nearly always successfully administered, the procedure does not give an indication of dynamic vibratory function of the larynx. Stroboscopy is highly effective for viewing vibratory function unless the vocal folds can not be seen or the motion is too aperiodic. When stroboscopy is not possible or in order to supplement stroboscopy, a quantified indication of laryngeal adduction can be obtained indirectly and noninvasively through a measure such as the abduction quotient. Furthermore, compared to the use of stroboscopy, more subtle indications of dynamic vocal fold instability can be obtained through acoustic perturbation analysis. Acoustic perturbation analysis can often be obtained when stroboscopy is not feasible and supplements stroboscopy when it is feasible. Stroboscopy, the Qa measure, and certain acoustic perturbation measures are limited by the lack of periodicity of the voice in some pathologic conditions. For example, patients after hemilaryngectomy or radiation therapy may have an irregular vibratory pattern that does not allow for analysis using these techniques. VLS often appears to tolerate more variability and noise than the perturbation or Qa measures of GLIMPES (9), but, therefore, interpretation of laryngeal function using VLS must be conservative. Adduction estimates from VLS and from Qa appear to correspond well enough to suggest that they are similarly meaningful, although Qa does not reveal posterior (cartilaginous) separation, and VLS is useless if the glottis is covered by arytenoid or ventricular tissue. When Qa is not determined, inspection of the EGG waveform may give highly relevant information. The EGG waveform must be suspect if there is a copious amount of fluid on the vocal folds. This study suggests that VLS, EGG analysis, and
Journal of Voice, Vol. 4, No. 3, 1990
acoustic recordings and measures are useful and complementary clinical tools in the evaluation of laryngeal function. Clinical readiness for all of them would allow a more complete voice analysis for clinical purposes and allow meaningful information gathering if one of the techniques were to be inappropriate or fail because of specific patient conditions. Acknowledgment: The authors would like to thank Vern Vail, Kathy Duran, Julie Artigliere, and Debbie Garrison for helping in many aspects of this study. Partial support for this project has come from grant 8 RO1 DC00387 from the National Institutes of Health. REFERENCES I. Shalkh A, Bless DM. Preliminary comparison of vocal fold vibration with strobotelescopic and strobofibroscopic examinations. Proceedings o f lnternational Conference on Voice, X X Congress o f l A L P 1986;2:9-14. 2. Childers DG, Krishnamurthy AK. A critical review of electroglottography. CRC Critical Review o f Biomedical Engineering 1985;12:131-61. 3. Sonesson B. A method for studying the vibratory movements of the vocal cords. J Laryngol Otol 1959;73:732-7. 4. Miller RH, Rosenfield DB. The role of electromyography in clinical laryngology. Otolaryngol Head Neck Surg 1984; 92:287-91. 5. Ludlow CL, Basich CJ, Connor NP, Coulter DC, Lee YJ. The validity of using phonatory jitter and shimmer to detect laryngeal pathology. In: Baer T, Sasaki C, Harris K, ed. Laryngeal function in phonation and respiration. Boston: College-Hill Press, 1987:492-508. 6. Trapp TK, Berke GS. Photoelectric measurement of laryngeal paralysis correlated with videostroboscopy. Laryngoscope 1988;98:486-92. 7. Hanson DG, Gerratt BR, Karin RR, Berke GS. Giottographic measures of vocal fold vibration: an examination of laryngeal paralysis. Laryngoscope 1988;98:541-9. 8. Anastaplo S, Karnell MP. Synchronized videostroboscopic and electroglottographic examination of glottal opening. J Acoust Soc Am 1988;83:1883-90. 9. Titze IR. Parameterization of the glottal area, glottal flow, and vocal fold contact area. J Acoust Soc A m 1984;75:570-80. 10. Rothenberg M, Mahshie JJ. Monitoring vocal fold abduction through vocal fold contact area. J Speech Hear Res 1988;30:338-51. 11. Scherer RC, Vail VJ. Measures of laryngeal adduction. J Acoast Soc Am 1988;84:$81 (A). 12. Scherer RC, Gould WJ, Titze IR, Meyers AD, Sataloff RT. Preliminary evaluation of selected acoustic and giottographic measures for clinical phonatory function analysis. J Voice 1988;2:230-44. 13. Hirano M. Clinical examination o f voice. New York: Springer-Vertag, 1981:52-3. 14. Titze IR, Scherer RC, Winholtz W. Manual o f instruction for GLIMPES users. Part I. Recording o f sigt, " . Denver: Recording and Research Center, Denver Ce lot the Performing Arts, 1985.
Vol. 4, No. 3, pp. 198-204 © 1990 Raven Press, Ltd., New York
A Comparison of Four Clinical Techniques in the Analysis of Phonation *David P. Hill, *Arlen D. Meyers, and *'?Ronald C. Scherer *Department of Otolaryngology/Head and Neck Surgery, University of Colorado Health Sciences Center; 7"The Recording and Research Center, The Denver Center for the Performing Arts, Denver, Colorado, U.S.A.
Summary: The success of four clinical techniques for voice analysis were compared: videolaryngoscopy, videolaryngostroboscopy (VLS), electroglottography (EGG) for laryngeal adduction, and acoustic perturbation analysis. Two normal and 26 consecutive voice patients were studied. All four techniques were successful with the normals and 42% of the patients. There were difficulties for 23% of the patients for the stroboscopic technique, 46% for the EGG analysis, and 35% for acoustic analysis. These difficulties were due primarily to aperiodicity of the voice signals or, in the case of stroboscopy, to the inability to view the vocal folds because of hypertrophy of tissue. Videolaryngoscopy failed only once due to intolerance by the patient. For the 28 subjects, only three (11%) could not be analyzed by either VLS, EGG, or acoustic techniques. There was a moderate correspondence between VLS and EGG analysis for the estimate of glottal adduction. The results strongly suggest the complementary and overlapping interpretations of these measures and, thus, the usefulness of the battery for clinical voice analysis. Key Words: Videolaryngoscopy--Videolaryngostroboscopy (VLS)--Acoustic analysis-Electroglottography (EGG)--Mucosal w a v e - - L a r y n x - - A d d u c t i o n - Abduction--Abduction quotient--Perturbation--Vocal cord--Vocal fold--Phonation--GLIMPES.
For many years, otolaryngologists and their patients have benefitted from visual diagnosis of many laryngeal disorders using a laryngeal mirror. Clinical application of indirect laryngoscopy with rigid and flexible laryngoscopes added a further dimension to the clinical evaluation of laryngeal disorders. The rapid movement of the vocal folds, however, has remained a limiting factor in the successful e v a l u a t i o n of m a n y f u n c t i o n a l vocal fold abnormalities. Over the past 10 years, several tech-
niques for the evaluation of vocal fold movement have been refined, and some have the potential to become simple, safe, and economic means for objective evaluation. Some of these techniques include videolaryngostroboscopy (VLS) (1), electroglottography (EGG) (2), photoglottography (PGG) (3), electromyography (EMG) (4), and acoustic analysis (5). Several recent studies have evaluated the clinical usefulness of some of these techniques. Trapp and Burke (6) studied the correlation of photoglottography and electroglottography with VLS in an in vivo canine model. They noted that the PGG and EGG waveforms were distinctly different between the simulated unilateral recurrent nerve paralysis and the superior laryngeal nerve paralysis. Hanson et al. (7) compared PGG and EGG measures in hu-
Address correspondence and reprint requests to Dr. D. P. Hill at Department of Otolaryngology/Head and Neck Surgery, University of Colorado Health Sciences Center, Box B-210, 4200 East Ninth Avenue, Denver, CO 80262, U.S.A. Presented at the Seventeenth Annual Symposium: Care of the Professional Voice, sponsored by the Voice Foundation, New York City, June 9, 1988.
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rnans having unilateral recurrent, superior, and idiopathic laryngeal paralysis and found that the PGG waveshapes differentiated between different categories of paralysis. Anastaplo and Karnell (8) studied four normal adult subjects with a split screen technique that simultaneously displays EGG waveform and videostroboscopic images. They further validated the relationship between the EGG waveform and glottic opening, showing that the " k n e e " (a point of discontinuity between two slopes on the EGG waveform) usually reflects the separation of the superior surface of the vocal folds in normal individuals. Measures of laryngeal adduction have been studied recently (9-12). Titze (9) developed a computer program called " G L I M P E S " (Glottal Imaging by Processing External Signals) that analyzes EGG recordings to predict laryngeal configuration and dynamic vocal fold motion. A laryngeal abduction measure is obtained from that analysis. GLIMPES also performs a number of perturbation analyses on recorded signals.
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The goal of the present study was to compare the success of obtaining information about laryngeal function among four techniques: constant light flexible videolaryngoscopy, videolaryngostroboscopy, laryngeal abduction via GLIMPES, and acoustic perturbation analysis via GLIMPES. These techniques and analyses are useful in determining laryngeal function, relatively easy to administer, and relatively noninvasive. MATERIALS AND METHODS Voice evaluation was performed for two normal subjects and 26 patients who were consecutively referred to the Center for Voice Disorders at the University of Colorado Health Sciences Center. Patient pathology varied from mild to severe dysfunction (Table 1). VLS was performed first. The patient was locally anesthetized with a topical oral preparation of 4% lidocaine spray and was placed in the examining chair (Fig. 1). VLS was performed using a Panasonic Color Video Camera model WV-F2, a Pana-
TABLE 1. List o f the 28 subjects evaluated with videolaryngoscopy, VLS, Qa, and acoustic perturbation analysis a Age
Sex
DH JA AS PB 1 VD HK GB
30 30 43 39 32 48 69
M
X
X
F F F F M M
X X X X X X
X X X X X X
8
SH
40
M
X
X
X
X
9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
JS JK PB2 ME HF GH PG SA CC AF FS EC Jp FB WP BK BM RW PW DV
65 30 30 68 68 58 38 58 63 62 55 67 77 67 58 60 65 69 68 49
M M M F M M F M M
X X X X X O X X X
X X X X X O O O O
X X X X X X O/X O/O O/O
X X X X X X X O O
M
X
O
X
X
M M M M M M M M M M
X X X X X X X X X X
O X X X X X X X X X
O/O O/O O/O O/O O/O O/O O/X O/X O/X X
O O O O O O X X X O
1
2 3 4 5 6 7
Video
Strobe
Q,/EGG b
Subject
Perturbation
Diagnosis
X
X
X X X X X X
X X X X X X
Normal subject Normal, small postchink Dystonia Left arytenoid trauma, stridor Right partial paretic TVC Right vocal process granuloma Parkinson's, bowing Bilateral leukoplakia T1 cancer, XRT Surgery to tongue, XRT Tension dysph, ant chink Tension dysphonia Supraglottal fatigue Tension dysphonia Tension dysph, hyperadd T1 cancer, XRT, edema Hypertrophy false cords Bowing right TVC, fluids Left TVC atrophy, aphonic Aphonic, post chink Left TVC paralysis Right hemilaryng, teflon, T2 Right hemil, false fold phon. T1 cancer, XRT Spastic dysphonia Glottic slit, fluids Hoarse, tight larynx Multiple sclerosis
Also included is a subjective technique of judging adduction by viewing the EGG waveshape. b The first X or O refers to success or failure, respectively, of the software to produce a Qa value. The second X or O refers to the judgment of degree of adduction by viewing the EGG waveshape (X) or the inability to judge adduction from the EGG waveshape (O). X, the technique was successful; O, the technique could not be used successfully. Age, sex, and basic diagnoses are included. T1, tumor confined to vocal cord(s) with normal cord mobility; XRT, radiation therapy; T2, supraglottal or subglottal extension of tumor.
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D. P. HILL E T AL.
FIG. 1. A sketch of the VLS exam. The examiner is holding the videocamera, using a flexible fiberoptic laryngoscope, and the patient or an assistant is holding the stethoscope on the neck to transduce the frequency of phonation. The foot pedal is used to key the direct or strobe light source. B&K, Bruel and Kjaer stroboscope type 4914.
sonic VCR model AG-1950, Olympus ENF type P flexible fiberoptic nasendoscope, a high-resolution Sony Color Video Monitor, and a Bruel and Kjaer Rhinolarynx Stroboscope type 4914. Videotapes of the exams were subjectively scored by the authors for the following categories: symmetry of vocal fold movement, amplitude of lateral movement, periodicity of mucosal wave motion, characteristics of the mucosal wave along the length of the cords, and closure during the phonatory cycle (13). Symmetry of vocal fold movement was broken down into the following categories: always, usually, episodically, and never symmetric. Asymmetry was then further broken down in terms of the differences in vertical or lateral position at rest and during phonation. Amplitude of lateral movement was categorized as great, normal, small, and absent. Each patient was also given a rating for consistency of amplitude over many cycles. Periodicity of vocal fold movement was scored in terms of cycle to cycle variability, and consistency of cycle period over many cycles, as seen on the stroboscopic image. This was not a direct measure of acoustic periodicity. Mucosal wave motion of the superior surface of the vocal fold was graded as great, normal, small, and absent. Consistency of the mucosal movement over time was also noted. Abnormal mucosal motion was further characterized by its location on the fold: anterior, middle, posterior third, or the entire fold. Journal of Voice, Vol. 4, No. 3, 1990
Closure was measured on a nominal scale: " o n e " meant pressed, " t w o " normal adduction, "three" a mild posterior or anterior chink, " f o u r " a moderate to large posterior chink or hourglass-shape glottis, "five" bowed cords, and "six" a glottal slit or chink the length of the cords. Of the 11 judgments, all three of the authors agreed 90% of the time, and two of the three agreed 95% of the time. The judgments differing across the three judges (5%) were excluded from further consideration. The patient was also taken to a recording station (14) (Fig. 2) and seated in a double-walled sound booth. An EGG electrode was placed against each side of the anterior neck over the thyroid laminae, and a third reference electrode was placed on the side of the neck. The patient was asked to remain a constant distance from the microphone. The initial mouth-to-microphone distance was measured at 12 in, b u t t h e r e was no n e e d to k e e p mouthto-microphone distance constant across subjects in this experiment. The patient was instructed to say 15 prolonged/a/vowels at a comfortable pitch and loudness, trying to keep the sound as steady as possible. Each phonation or "token" was - 3 s in duration. The patient also read several standard passages and performed maneuvers to evaluate vocal range and fundamental frequency during reading. Acoustic recordings were made using a Realistic Cardioid Microphone, an ATI M-1000 Precision Dual Microphone Preamplifier, and an AKG Acoustic Amplifier. EGG recordings were made using a Synchrovoice Research Electroglottograph. The simultaneous EGG and acoustic signals produced by the patient were digitized, multiplexed, and video encoded within a Sony Digital PCM
FIG. 2. A sketch of a GLIMPES recording station. The EGG and acoustic signals are digitized and recorded on half-inch videotape.
CLINICAL A N A L YSIS OF P H O N A T I O N
model 501ES and recorded onto a Magnavox VCR. The videotapes were sent to The Recording and Research Center of The Denver Center for the Performing Arts for analysis on a VAX 11/750 computer. A report form with perturbation measures (from the acoustic signal) and abduction measures (from the EGG signal) as well as a subjective analysis of both acoustic and EGG measures and waveforms (12) by a voice scientist was returned to the otolaryngology clinic. This arrangement made these evaluation techniques feasible in the clinic setting. ABDUCTION ANALYSIS The EGG signal was analyzed through an analysis-synthesis scheme within GLIMPES. The abduction quotient (Q~) was obtained for five consecutive cycles within approximately the center position of each token. Qa is defined (9) as the ratio of the half-distance between the vocal processes to the amplitude of vibration of (one of) the vocal folds. This parameter would increase if vocal process separation increased or vocal fold amplitude decreased. Excised canine larynx and human studies verify Qa as a useful measure of glottal abduction (12). 1 Values of Qa < - 1 . 0 suggest hyperadduction and >0.5 suggest hypoadduction (12). ACOUSTIC ANALYSIS Perturbation analysis was performed on 100 consecutive cycles within each of the 15 tokens of the microphone signal. Four perturbation measures (12) were obtained for the prolonged/a/microphone recordings: the coefficient of variation for frequency (CVF) and jitter are measures of the stability of signal fundamental frequency, and the coefficient of variation for amplitude (CVA) and shimmer are measures of the stability of signal amplitude. Jitter and shimmer are measures of adjacent cycle perturbation, and CVF and C V A are related to the calculation of the standard deviation of cycle frequency and amplitude, respectively (12). Short-term instai Qa was tested with seven normal actor subjects who imitated very breathy, normal, and very pressed (or constricted) voice qualities. Qa values were consistent with greater abduction of the Vocal processes for the breathy tokens and greater adduction for the pressed tokens. The decision of hypo- or hyperadduction based on the Q~ value for clinical and research purposes is conservative in that the Qa value must exceed one-half standard deviation beyond the mean for very breathy or the very pressed tokens. Further information on the validity and application of the abduction quotient can be found elsewhere (12).
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bility, shown as relatively high values for jitter and shimmer, are most likely associated with laryngeal tissue abnormalities, fast-acting neuromuscular fluctuations, or asymmetry of movement (12). Longer-term instability, reflected as relatively high numbers for CVA and CVF, suggest relatively slow fluctuations of amplitude or frequency, respectively (12). RESULTS Table 1 gives a list of the subjects, basic diagnoses, and success or failure of the four techniques, videolaryngoscopy, VLS, Qa, and acoustic perturbation (jitter, shimmer, and coefficients of variation for amplitude and frequency). A technique was successfully administered when the recordings and data obtained appeared reliable and valid. Also included in the table with Qa is the additional "technique" of judging laryngeal adduction strictly by viewing the EGG waveshape when Qa w a s not available. The first two subjects in Table 1 were normal controls for whom all four techniques were successful. The next 26 subjects were patients. All four techniques were successful for 11 of the 26 patients (42%), representing a wide range of diagnoses. Two examples of this group follow. Case 1: JA was a 30-year-old normal woman with a physiologic posterior glottic chink on videolaryngoscopy, and normal glottic symmetry, amplitude, periodicity, and mucosal wave on VLS. She had no complaints. The Q~ and acoustic measures were all normal. Case 2: H K was a 48-year-old man with a large contact granuloma arising from the vocal process of the right arytenoid cartilage. His symptoms included throat pain and vocal fatigue after prolonged voice usage, but he did not complain of hoarseness or breathiness. VLS showed complete closure, normal symmetry, amplitude, periodicity, and mucosal wave. The granuloma was not interfering with voice production. Qa and acoustic measures were normal, supporting the findings on VLS. There were difficulties with endoscopy for six (23%) of the patients (patients 14-19 in Table 1). Patient GH could not tolerate the flexible endbscopy procedure. For patients PG, SA, and CC, the glottis was obscured from vision by overhanging swollen arytenoid cartilages or ventricular folds. For AF and FS, the acoustic signal was too aperiodic or the voice too aphonic to permit synchronous flashing of the light source using stroboscopy. Journal of Voice, Vol. 4, No. 3, 1990
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Even though there were difficulties with endoscopy for six patients, for three of them (GH, PG, and AF) the EGG signal was generally helpful in determining relevant adduction information. For the other three patients, the voice was too aperiodic (SA and FS) or the patient could not sustain the/a/ vowel sufficiently long (CC). The case for subject AF is now described. Case 3: AF was a 62-year-old man with bowing of the true vocal cords. Stroboscopic examination was unsuccessful due to copious amounts of secretions in the larynx. CVA, jitter, and shimmer were very high, suggesting either an unstable larynx or (more likely) noise caused by acoustic transients as the glottal airflow passed through the secretions on the vocal folds. Qa was low, suggesting hyperadduction. However, both the bowing and the copious fluid may have altered the EGG waveshape. Interpretation of the Qa values would have to be made with care in this case. There were difficulties in obtaining Qa for 12 (46%) of the patients. For six patients (patients 16 and 19-23 in Table 1), the voice was too aperiodic for EGG analysis. One patient (CC) could not sustain the/aJ vowel long enough for analysis, and one patient (BK) had a voice that was too rough and fry-like for successful EGG analysis. For these patients, the EGG waveform could not be reliably judged by visual inspection. However, for four additional patients for whom the Qa could not be obtained (patients 15 and 25-27 in Table 1), the EGG signal was sufficiently well defined that a judgment could be rendered: For patients PG and BM, the EGG signal was too "wide" for GLIMPES analysis to be successful, but the waveshape strongly suggested hyperadduction. For patient RW, the EGG signal was very "narrow," suggesting wide abduction. Finally, although PW had a noisy EGG signal that prevented GLIMPES analysis, the waveshape was sufficiently intact for a judgment of hyperadduction. These results suggest that the EGG signal is not useful when the voice is too aperiodic, an obvious conclusion, but moreover, frequently can be meaningfully interpreted by visual inspection of waveshape when the software analysis is unsatisfactory. Discussion will now be given for patients SA and BM from this group for which Qa could not be obtained. Case 4: SA was a 58-year-old man who recently underwent radiation therapy for TI cancer of the right true vocal fold. He had been hoarse since the termination of his treatment course 10 months prior to this exam. Videolaryngoscopy revealed Journal of Voice, Vol. 4, No. 3, 1990
that the reason for his hoarseness was swollen arytenoids and false cord phonation. During phonatory tasks, the true vocal folds were completely obscured, and the swollen false cords were in contact, apparently initiating a low glottal fry-like quality. The patient's voice was aperiodic and sounded rough. The acoustic, strobe, and EGG evaluations were not feasible. Case 5: BM was a 65-year-old man with spastic dysphonia. VLS was difficult to perform because the true vocal cords were often obscured by hypopharyngeal constriction. The "best segment" stroboscopic exam revealed symmetric movement most of the time, a small consistent amplitude, normal periodicity, and complete glottic closure. Acoustic "best voice" samples revealed normal cycle-to-cycle variations (normal jitter and shimmer), but very high CVA and CVF, suggesting that the instability of phonation was characterized by a slow variation in frequency and amplitude. The abduction quotient was unattainable because the EGG signal was too wide for analysis by GLIMPES, but the extreme width suggested hyperadduction. These EGG and acoustic findings supported the diagnosis of spastic dysphonia. Table 1 also shows the cases for which there were difficulties in obtaining acoustic perturbation analyses. This occurred for nine (35%) of the patients and was due to nearly aperiodic vocal production (patients 16 and 19-23 in Table 1), inability to prolong the/a/vowel long enough (subject CC), a voice that was too rough and fry-like (BK), and a voice for which transient sounds and apparent double excitations prohibited analysis (DV). Patient FB had a voice that was too noisy for perturbation analysis using GLIMPES. Case 6: FB was a 67-year-old man who underwent right hemilaryngectomy for laryngeal cancer 15 years ago, with subsequent teflon injection into the right laryngeal wall at the level of the left true vocal cord. Phonation could be evaluated with VLS, which showed an irregular, floppy, but effective left true vocal cord (TVC) flapping against the outpouching of tissue caused by the patient's teflon injection. Symmetry was absent, amplitude of the left cord was great, periodicity was consistently irregular, the mucosal wave was irregular, and closure was incomplete with a persistent glottal slit. The voice was very breathy, and the microphone signal was too noisy to allow successful acoustic perturbation analysis with GLIMPES. There were five patients (19%) for which the qualitative video techniques were successful, but the quantitative measures (Qa, perturbation analy-
CLINICAL A N A L YSIS OF PHONATION
ses) were not (patients 20-24 in Table 1). The patients' voices were sufficiently aperiodic that the software was inappropriate or unsuccessful, but not aperiodic enough to prevent stroboscopy from giving some useful information. In contrast, there were two patients (8%) for which stroboscopy was unsuccessful, but Qa and perturbation analyses were successful (patients GH and AF). In these cases, adduction and vocal stability were attributes complementing the absence of stroboscopy. Both the videostroboscopic view of the larynx and analysis of the EGG signal allowed for a judgment of laryngeal adduction. Table 2 gives this comparison for the 16 cases for which both were available (excluding the case of bowed vocal folds, for which the Q~ value may be artificially lowered). The table suggests that there is correspondence between the visual judgment of adduction through VLS and decisions based on GLIMPES analysis (13 cases) and inspection of the EGG signal (three cases). The data were weighted toward relatively normal adduction for both measures. Eleven of the 16 cases were in essential agreement (those along the main diagonal). The other cases are also of interest. Moderate glottal opening (VLS category C), but normal computed adduction (Qa) was the case for the normal female voice (patient JA). This suggests that the VLS technique may underestimate normal limits of glottal abduction within normal subjects, or the abduction quotient may be insensitive to detecting slightly abnormal abduction in otherwise normal subjects. Because conservative limits were placed on deciding hyper- or hypoadduction from the Qa value (12), however, it is also likely that the subject may have produced greater hypoadduction while being scoped than during the acoustic recording (the two procedures were not simultaneous). The case of incomplete closure (category C) with hyperadduction (EGG analysis), a seemingly contradictory finding, sounded breathy but "forced" during
TABLE 2. Comparison between stroboscopic and GLIMPES (9) measures of adduction Visual degree of closure
EGG analysis Hyperadduction Normal adduction Hypoadduction
A
B
C
1 1 0
2 9 0
1 1 1
A, pressed larynx; B, normal closure or small anterior or posterior chink; C, a moderate to large anterior or posterior chink, or glottal separation the length of the glottis.
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the acoustic recordings, suggesting that the glottis may have been closed firmly at the vocal processes but was open between the arytenoid cartilages (at least during the acoustic recordings). One of the two hyperadduction category B cases showed through VLS that the larynx "appeared tight" despite an anterior chink, suggesting that the larynx may have been hyperadducted at the vocal processes, a configuration reflected in the EGG analysis. The case of normal adduction with pressed appearance (category A) was associated with a low normal Qa value. These results suggest that there appears to be an important correspondence between adduction seen via stroboscopy and inferred through the Qa value. Furthermore, the advantage of the Qa value is that it is a quantitative estimate of adduction of the membranous glottis, whereas the advantage of stroboscopy is that it allows viewing the relative closure of the membranous versus the cartilaginous glottis. Both techniques appear to be diagnostically valuable. DISCUSSION The four techniques examined in this report are complementary: Videolaryngoscopy is useful in determining gross structural and tissue characteristics, VLS is useful in determining functional characteristics of vocal fold motion, Qa is a quantitative measure that is strongly related to laryngeal adduction, and acoustic voice measures give quantitative indices of laryngeal stability and help in determining etiology (12). The measures are not completely independent, however: The visual techniques also give indications of adduction (Table 2) and stability. The overlap of information between the visual techniques and the quantitative techniques is of primary usefulness when one or the other is not possible to obtain for a particular patient. However, the acoustic measures are not easily compared to the VLS judgments. The majority of patients with even abnormal acoustic indices had normal appearing periodicity and amplitude on VLS. This is most likely due to the effectively low visual sampling of vibration intrinsic to stroboscopy. This suggests that stroboscopy should be supplemented by more accurate perturbation measures in order to determine laryngeal stability. EGG, acoustic, and stroboscopic measures in this report are all dependent on the periodic or cyclic nature of voice production. Extremely breathy, Journal of Voice, Vol. 4, No. 3, 1990
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hoarse, or diplophonic signals are not successfully analyzed by the software version used for this report (9,12). The usefulness of Qa and acoustic perturbation measures appears to be in analyzing mild to moderate voice dysfunction, and appears to be useful for a wide range of laryngeal abnormalities. CONCLUSION Although videolaryngoscopy is extremely useful in evaluating gross anatomic, morphologic, and tissue changes, and is nearly always successfully administered, the procedure does not give an indication of dynamic vibratory function of the larynx. Stroboscopy is highly effective for viewing vibratory function unless the vocal folds can not be seen or the motion is too aperiodic. When stroboscopy is not possible or in order to supplement stroboscopy, a quantified indication of laryngeal adduction can be obtained indirectly and noninvasively through a measure such as the abduction quotient. Furthermore, compared to the use of stroboscopy, more subtle indications of dynamic vocal fold instability can be obtained through acoustic perturbation analysis. Acoustic perturbation analysis can often be obtained when stroboscopy is not feasible and supplements stroboscopy when it is feasible. Stroboscopy, the Qa measure, and certain acoustic perturbation measures are limited by the lack of periodicity of the voice in some pathologic conditions. For example, patients after hemilaryngectomy or radiation therapy may have an irregular vibratory pattern that does not allow for analysis using these techniques. VLS often appears to tolerate more variability and noise than the perturbation or Qa measures of GLIMPES (9), but, therefore, interpretation of laryngeal function using VLS must be conservative. Adduction estimates from VLS and from Qa appear to correspond well enough to suggest that they are similarly meaningful, although Qa does not reveal posterior (cartilaginous) separation, and VLS is useless if the glottis is covered by arytenoid or ventricular tissue. When Qa is not determined, inspection of the EGG waveform may give highly relevant information. The EGG waveform must be suspect if there is a copious amount of fluid on the vocal folds. This study suggests that VLS, EGG analysis, and
Journal of Voice, Vol. 4, No. 3, 1990
acoustic recordings and measures are useful and complementary clinical tools in the evaluation of laryngeal function. Clinical readiness for all of them would allow a more complete voice analysis for clinical purposes and allow meaningful information gathering if one of the techniques were to be inappropriate or fail because of specific patient conditions. Acknowledgment: The authors would like to thank Vern Vail, Kathy Duran, Julie Artigliere, and Debbie Garrison for helping in many aspects of this study. Partial support for this project has come from grant 8 RO1 DC00387 from the National Institutes of Health. REFERENCES I. Shalkh A, Bless DM. Preliminary comparison of vocal fold vibration with strobotelescopic and strobofibroscopic examinations. Proceedings o f lnternational Conference on Voice, X X Congress o f l A L P 1986;2:9-14. 2. Childers DG, Krishnamurthy AK. A critical review of electroglottography. CRC Critical Review o f Biomedical Engineering 1985;12:131-61. 3. Sonesson B. A method for studying the vibratory movements of the vocal cords. J Laryngol Otol 1959;73:732-7. 4. Miller RH, Rosenfield DB. The role of electromyography in clinical laryngology. Otolaryngol Head Neck Surg 1984; 92:287-91. 5. Ludlow CL, Basich CJ, Connor NP, Coulter DC, Lee YJ. The validity of using phonatory jitter and shimmer to detect laryngeal pathology. In: Baer T, Sasaki C, Harris K, ed. Laryngeal function in phonation and respiration. Boston: College-Hill Press, 1987:492-508. 6. Trapp TK, Berke GS. Photoelectric measurement of laryngeal paralysis correlated with videostroboscopy. Laryngoscope 1988;98:486-92. 7. Hanson DG, Gerratt BR, Karin RR, Berke GS. Giottographic measures of vocal fold vibration: an examination of laryngeal paralysis. Laryngoscope 1988;98:541-9. 8. Anastaplo S, Karnell MP. Synchronized videostroboscopic and electroglottographic examination of glottal opening. J Acoust Soc Am 1988;83:1883-90. 9. Titze IR. Parameterization of the glottal area, glottal flow, and vocal fold contact area. J Acoust Soc A m 1984;75:570-80. 10. Rothenberg M, Mahshie JJ. Monitoring vocal fold abduction through vocal fold contact area. J Speech Hear Res 1988;30:338-51. 11. Scherer RC, Vail VJ. Measures of laryngeal adduction. J Acoast Soc Am 1988;84:$81 (A). 12. Scherer RC, Gould WJ, Titze IR, Meyers AD, Sataloff RT. Preliminary evaluation of selected acoustic and giottographic measures for clinical phonatory function analysis. J Voice 1988;2:230-44. 13. Hirano M. Clinical examination o f voice. New York: Springer-Vertag, 1981:52-3. 14. Titze IR, Scherer RC, Winholtz W. Manual o f instruction for GLIMPES users. Part I. Recording o f sigt, " . Denver: Recording and Research Center, Denver Ce lot the Performing Arts, 1985.