Journal of" Voice Vol. 3, No. 4, pp 337-341 1989 Raven Press, Ltd., New York

A Study on the Mechanism of Functional Dysphonia

Shilin Yang and Liancai Mu

Liaoning Research Center of Logopedics and Phoniatrics, 3rd Hospital Affiliated to China Medical University, Shenyang, People's Republic of China

Summary: A total of 333 patients with a diagnosis of functional dysphonia were studied by both laryngeal electromyography (EMG) and spectral analysis. EMG and acoustic analysis revealed that some patients with so-called func- tional dysphonia diagnosed by physical examination alone in fact suffered from a variable degree of laryngeal nerve paralysis. Laryngeal EMG plays an im- portant role in determining whether patients with a diagnosis of functional dysphonia have organic disease of the laryngeal nerves. Key Words: Functional dysphonia--Vocal cord paresis--Laryngeal electromyography.

Functional dysphonias have been described ex- tensively in the literature and classified into many forms by previous authors (1-5). It is generally ac- cepted that functional dysphonia usually occurs in people who are emotionally unstable. On the other hand, the dysphonias can cause secondary organic abnormalities such as vocal cord nodules or polyps. Generally speaking, incomplete closure of the vocal cords is the most striking finding on laryngoscopy. Although the functional dysphonias have been di- vided into many forms, they are usually classified into four types, i.e., hyperfunctional, hypofunc- tional, plicae ventricularis, and habitual dyspho- nias. It is generally accepted that these four types of dysphonia are functional without organic disease of the larynx.

MATERIALS AND METHODS Subjects

.Subjects were 333 patients with a diagnosis of functional dysphonia, 211 males and 122 females, ranging from 14 to 78 years of age.

The subjects were divided into four groups. Groups 1 included those with inadequate closure

of the glottis (fusiform glottic chink or a small tri-

This work was presented at the Beijing International Sympo- sium on Otolaryngology, Beijing, October 25-30, 1988.

Address correspondence and reprint requests to Dr. Liancai Mu, Department of Otolaryngology, 3rd Hospital Affiliated to China Medical University, Shenyang, Liaoning, P.R. of China.

angular chink between the two cords from the an- terior commissure to the posterior commissure) or inadequate closure of the glottis with hypertrophy or hyperadduction of the ventricular folds (Figs. 1--4).

Group 2 includes those with simple hypertrophy or hyperadduction of ventricular folds (Figs. 5 and 6).

Group 3 includes those with inadequate closure of the glottis or hypertrophy of the ventricular fold associates with vocal nodule, polyp, or edema of the vocal cords (Figs. 7-9).

Group 4 includes those with functional dysphonia without positive findings in the larynx (Fig. 10).

Methods Initially, the vocal cords were examined by indi-

rect laryngoscopy. Next, the voice of the patient was analyzed with a Bruel & Kjaer 2031 Narrow Band Spectrum Analyser in order to evaluate pho- natory function. Finally, one DISA four-channel electromyograph provided simultaneous monitoring and recording of spontaneous muscle activity from the cricothyroid (CT), thyroarytenoid (TA), and posterior cricoarytenoid (PCA) muscles of both sides. Recordings of electromyography were pro- duced utilizing monopolar concentric needle elec- trodes. An external approach was always used for inserting the electrodes. In addition, stroboscopy was used in some cases of each group.

337

338 S. YANG AND L. MU

FIGS. 1-4. Typical glottic shapes seen during indirect laryngoscopy in patients with dysphonia. Fig. 1. Fusiform chink. Fig. 2. Posterior small triangular chink. Fig. 3. Large triangular chink. Fig. 4. Inadequate closure of the glottis with hypertrophic or hyperadducted ventricular folds.

RESULTS

The dysphonias of the 333 patients were classi- fied into four types: hyperfunctional, hypofunc- tional, habitual, and plicae ventricularis.

Hyperfunctional dysphonia This term indicates excessive use of all of the

laryngeal muscles. During phonation, excessive tension of the vocal cords is usually seen. In marked cases, the voice sounds rough and heavy. The respiratory muscles also show evidence of ex- cess activity and the neck veins are frequently dis- tended because of straining. On laryngoscopy, the main laryngoscopic feature of increased laryngeal muscle tension is an open posterior glottic chink between the arytenoid cartilages. In some cases, the vocal cords are usually red and thickened and the ventricular folds are hypertrophic. Stroboscopy revealed that fluctuation of the mucosa of the vocal cords is reduced.

In this group, three of five only had a small tri- angular chink in the posterior one-third of the glot- tis, and one had a small triangular chink with a hy-

FIGS. 5, 6. Typical glottic shapes seen during indirect laryngos- copy in patients with dysphonia plicae ventricularis. Fig. 5. Hy- pertrophy of the ventricular fold. Fig. 6. Hyperadduction of the ventricular fold.

pertrophic ventricular fold; another had normal vo- cal cords (Figs. 11-13).

Spectral analysis of these subjects' voices re- vealed that the vocal cord function was decreased. The voice spectrum showed that the noise compo- nent increased.

Hypofunctional dysphonia Hypofunctional dysphonia is characterized by

hypotonia of the muscles of the vocal cord. It usu- ally occurs in people who are emotionally unstable. The voice is weak and muffled and air escape can be heard. Incomplete closure of the vocal cords is the most striking finding on laryngoscopy. On strobos-- copy, active vibration of the mucosa of the vocal cords was observed in some cases of this group.

This is the largest group in this study. There were 146 patients with this form of dysphonia. In this group, 93 cases had a large triangular chink between the two cords from the anterior commissure to the posterior commissure, 18 cases had a large triangu- lar chink with hypertrophy or hyperadduction of the ventricular folds, 33 cases had fusiform chink be- tween the two cords, and 2 cases had a fusiform chink with hyperadduction of the ventricular folds (Figs. 14-17).

The voice spectrum showed that the noise com- ponent obviously increased, indicating that these patients had reduced phonatory function.

Habitual dysphonia The habitual dysphonias are primary functional

disorders that are usually caused by incorrect use of the voice and often by emotional disorders. The dysphonia can cause secondary organic abnormali- ties such as vocal cord nodules or polyps. How- ever, most cases in this group had hoarseness with- out positive findings in the larynx.

There were 117 patients with this form of dyspho-

Journal of Voice, Vol. 3, No. 4, 1989

MECHANISM OF FUNCTIONAL D YSPHONIA 339

i "" '~11 FIGS. 7-9. Typical glottic shapes seen in group 3. Fig. 7. Inadequate closure of the glottis with vocal nodule. Fig. 8. Inadequate closure of the glottis with polypus of the vocal cord. Fig. 9. Hypertrophy of the ventricular fold with a vocal nodule.

nia. Ninety-nine cases of the 117 had reduced pho- natory function. A spectrum of the voice showed that the vocal range became narrow, and the pho- nation time was short. The others, however, had normal phonatory function.

Dysphonia plicae ventricularis Dysphonia ventricularis arises when the ventric-

ular folds play an active part in phonation. The ven- tricular folds were not designed for phonation, so that they produce a rough unmodulated sound. Dur- ing phonation, the ventricular folds often close first, and in long-standing cases may be hypertrophic. In some cases, it was difficult to see the true vocal cords during laryngoscopy.

Sixty-five patients with hypertrophy or hyperad-

FIG. 10. The normal glottic shape on phonation.

FIGS. 11-13. Hyperfunctional dysphonia with variable glottic shapes. Fig. 11. Small triangular chink. Fig. 12. Small triangular chink with a hypertrophic ventricular fold. Fig. 13. Normal vocal cords.

duction of the ventricular folds and with normal true vocal cords were included in this group (Figs. 18 and 19).

Among the 65 patients, there were 17 cases with normal vocal range, and 48 cases with reduced vo- cal range, as the voice spectrum showed.

Laryngeal EMG findings and diagnostic criteria are as follows: (a) Prolonged duration of the poten- tials, electrical silence, or fibrillation potentials

FIGS. 14-17. Hypofunctional dysphonia with variable glottic shapes. Fig. 14. Large triangular chink. Fig. 15. Large triangular chink with hypertrophy or hyperadduction of the ventricular folds. Fig. 16. Fusiform chink. Fig. 17. Fusiform chink with hy- peradducted ventricular folds.

FIGS. 18, 19. The glottic shapes seen in the patients with the dysphonia plicae ventricularis. Fig. 18. Hypertrophy of the ven- tricular fold. Fig. 19. Hyperadduction of the ventricular folds.

Journal of Voice, Vol. 3, No. 4, 1989

340 S. YANG AND L. MU

TABLE 1. Some EMG findings and diagnosis in the patients with variable forms of dysphonias

Mean potential Duration (ms)

CT TA PCA Patient Age Clinical EMG

no. Sex (years) diagnosis L R L R L R diagnosis

39 Female 32 Hypo-FD 6.3 6.5 5.6 5.3 12.1 8.1 BCPP of RLN, SLN 21% 25% 64% 55% 168% 32%

76 Male 20 Hyper-FD 5.3 5.3 3.9 4.9 6.2 6.3 BPP of RLN 1% 1% 14% 23% 38% 40%

5 Female 26 Hypo-FD 6.8 6.0 4.4 5.5 6.6 6.7 LCPP and RRLN PP 26% 13% 22% 62% 56% 52%

91 Male 55 DPV 5.4 5.3 4.7 3.5 5.9 5.3 LRLN PP 1% - - 34% 1% 31% 18%

97 Female 20 Hypo-FD 5.0 5.1 3.9 3.4 4.9 4.7 Normal EMG -3% -1% 14% - - 11% 6%

37 Male 47 Hypo-FD Silence 3.6 3.6 4.7 4.7 BSLN CP 2% 2% 4% 4%

135 Male 18 Hypo-FD 4.7 5.4 3.8 F.P. 4.3 6.1 LSLN PP, RRLN PP - 9% 4% 12% - 2% 34%

Prolonged potential duration means that over 20% of potentials measured have prolonged duration. L, left; R, right; Hypo-FD, hypofunctional dysphonia; Hyper-FD, hypeffuctional dysphonia; DPV, dysphonia plicae ventricularis;

BCPP, bilateral combined partial paralysis; BPP, bilateral partial paralysis; LCPP, left combined partial paralysis; PP, partial paralysis; BSLN CP, bilateral SLN complete paralysis.

from unilateral or bilateral CT, TA, PCA, or CT, either of the TA and PCA, indicates that the patient has a combined recurrent laryngeal nerve (RLN) and the superior laryngeal nerve (SLN) partial or complete paralysis. (b) If the above EMG findings are found in unilateral or bilateral TA and PCA, or in either of them, a diagnosis of partial or complete RLN paralysis can be made. (c) Prolonged potential duration or electrical silence or fibrillation poten- tials from unilateral or bilateral CT muscles, indi-

cates that unilateral or bilateral SLNs have been paralyzed partially or completely.

Some EMG findings as diagnostic evidence of la- ryngeal nerve paralysis are shown in Table 1.

EMG findings of the 333 patients with dysphonias are summarized in Table 2.

DISCUSSION

Functional dysphonias are common voice disor- ders in clinical practice. Our classification is based

TABLE 2. EMG changes and diagnosis of the four forms of the dysphonias

Intrinsic laryngeal muscles

Clinical diagnosis

Hyper-FD Hypo-FD HD DPV Total EMG diagnosis

BTA, PCA; either of TA, PCA 3 BCT, TA, PCA; either of TA, PCA 0 LTA, PCA; either of TA, PCA 0 RTA, PCA; either of TA, PCA 1 LCT, TA, PCA; RTA, PCA; either of RTA, PCA 0 BCT 0 LCT, RTA, PCA; either of RTA, PCA 0 LCT, TA, PCA; either of TA, PCA 0 RCT, TA, PCA; LTA, PCA 0 LCT, TA, PCA; RCT 0 RCT; LTA, PCA 0 LCT 0 Normal EMG of CT, TA 0

PCA on both sides Hyperthyroidism 0 Congestion of vocal cords 0

1

5 Total

89 65 37 194 BPP of RLN 8 8 2 18 BCPP 9 12 7 28 LRLN, PP

16 19 11 47 RRLN PP 3 3 3 9 LCPP and RRLN PP 4 1 2 7 BSLN CP or PP 2 0 0 2 LSLN, RRLN PP 2 2 1 5 LCPP 0 4 0 4 RCPP; LRLN PP 0 1 0 1 LCPP; RSLN PP 0 1 0 1 RSLN, PP; LRLN PP 0 0 0 1 LSLN PP 6 1 1 8 FD

1 0 0 1 FD 6 1 1 6 FD 0 0 0 1 FD (vocal overuse)

146 117 65 333

FD, functional dysphonia; HD, habitual dysphonia. The other abbreviations are the same as those in Table 1.

Journal of Voice, Vol. 3, No. 4, 1989

MECHANISM OF FUNCTIONAL D YSPHONIA 341

on 333 patients with dysphonias and on previous classifications in the literature. The results of this study showed that 16 cases (4.8%) of the 333 were truly functional with normal EMG of the intrinsic laryngeal muscles, while the other 317 cases (95.2%) were organic with varying degrees of laryn- geal nerve paresis. The etiology of 232 cases (69.9%) of the 333 remains unknown. We agree with Dedo's opinion (6) that the cases whose cause is unknown may be caused by a virus. Clinically, par- tial paralysis of the laryngeal nerves can not be identified with routine examinations without laryn- geal electromyography. Some of the so-called func- tional dysphonias are in fact due to laryngeal nerve paresis.

CONCLUSIONS

The results of the present study indicate that neu- rogenic lesions in laryngeal muscles are frequent in dysphonia diagnosed as functional from routine ex- aminations.

The present study emphasizes the diagnostic value of electromyographic examination in cases suffering from dysphonia of unknown origin.

Acknowledgment: We thank Mrs. Zhao Yuhong for her help in editing and typing the manuscript, Mrs. Li) Shu- qing for technical assistance, and Mr. Fan Yu for the photography. This study was supported in part by re- search grant No. 3860762 from the National Natural Sci- ence Funds.

REFERENCES

1. Wu X. Laryngology, 1st edition. Shanghai: Shanghai Sci- ence and Technology Press, 1981:254--61.

2. Morrison MD, Nichol H, Rammage LA. Diagnostic criteria in functional dysphonia. Laryngoscope 1986; 94:1-8.

3. Koufman JA, Blalock PD. Classification and approach to patients with functional voice disorders. Ann Otol Rhinol Laryngol t982;91:372-7.

4. Zhang N. Concise vocal disorders. Beijing: People's Pub- lishing House, 1981:254-61.

5. Yang S, Hu L, Han Z. Spectral analysis of the human voice and its clinical applications. Chin J Otorhinolaryngol 1986; 21:275-8.

6. Dedo DD. Pediatric vocal cord paralysis. Laryngoscope 1979 ;89:1378-84.

Journal of Voice, Vol. 3, No. 4, 1989