Dysphonia Severity Degree and Phonation Onset Latency in Laryngeal Adductor Dystonia

Dysphonia Severity Degree and Phonation Onset Latency in Laryngeal Adductor Dystonia *Noemi Grigoletto De Biase, *Gustavo P. Korn, *Paula Lorenzon, †Marina Padovani, †Miriam Moraes, †Glaucya Madazio, and ‡Luiz Celso P. Vilanova, *yz Sao Paulo, Brazil Summary: Although the latency between the initiation of thyroarytenoid electrical activity and the onset of phonation generally is increased in patients with adductor laryngeal dystonia, there is disagreement about whether there is overlap of latency values in these patients and normal subjects. The goal of this article was to compare the severity of dysphonia with the latency between electrophysiological activation of the thyroarytenoid muscle (TA) and the onset of phonation in patients with adductor laryngeal dystonia and compare the values with normal controls. Twenty-one patients with adductor dystonia and 15 control patients underwent laryngeal electromyographic (EMG) examination of the left TA. We measured the latency from initiation spike of the electric activity of the TA muscle to the onset of phonation. Three speech-pathologists/voice specialists arrived at a consensus to rate the perceptual evaluation of voice quality for the study group. The average latency measured for patients with mild dysphonia was 332 milliseconds, for moderate dysphonia was 426 milliseconds, and for the severe dysphonia was 792 milliseconds. We used the Spearman’s correlation test to compare the latency time values and the dysphonia’s degree of severity (P < 0.05). Latency was significantly and directly related to the degree of severity of dysphonia. Key Words: Dystonia–Electromyography–Dysphonia. INTRODUCTION There is increasing interest in the clinical relevance of laryngeal electromyography (LEMG).1–8 Because it is technically difficult to perform, LEMG is not a common investigative technique. However, it has revealed significant new information about laryngeal diseases that compromise vocal fold mobility.1–4,6–8 Laryngeal dystonia does not have a single typical LEMG pattern and the findings vary from normal to nonspecific abnormalities.9 There is no evidence of spontaneous pathologic activity at rest. The resting state may exhibit increased voluntary activity, possibly from the patient’s difficulty to relax the laryngeal muscles. The waveforms of the potentials may be normal, but poor coordination between the agonist and antagonist muscles or inappropriate activation also may be recorded.9,10,13,16 In the most frequent type of laryngeal dystonia, adductor dystonia, abnormalities of electrical activity, such as variations in the amplitude of the potentials or even in the recruitment may occur synchronously with pauses in phonation.9 Periodic and rhythmic discharges also have been described, most often in association with tremor.9–15 Blitzer et al14 observed an increase in the time from the electrical evidence of muscular activity to the onset of phonation. This measurement requires a second channel for the microphone, which captures the patient’s voice during the recording of the electrical muscular activity. The latency is about 200 milliseconds in normal subjects, but jumps Accepted for publication October 27, 2008. From the *Department of Otolaryngology Head Neck Surgery, Universidade Federal de Sao Paulo, Sao Paulo, Brazil; yDepartment of Speech Language Pathology, Universidade Federal de Sao Paulo, Sao Paulo, Brazil; and the zDepartment of Neurology, Universidade Federal de Sao Paulo, Sao Paulo, Brazil. Address correspondence and reprint requests to Noemi Grigoletto De Biase, Universidade Federal de Sa˜o Paulo, Otolaryngology Head Neck Surgery, Rua Doutor Pedro de Toledo, 106, 04721-050 Sao Paulo, Brazil. Tel.: +55 11 5683 2903. E-mail: ngdebiase@ gmail.com Journal of Voice, Vol. 24, No. 4, pp. 406-409 0892-1997/$36.00 Ó 2010 The Voice Foundation doi:10.1016/j.jvoice.2008.10.012

over to 500 milliseconds in dystonic patients and may reach up to 1 second.11,13–16 Adductor laryngeal dystonia is related to spasms of the adductor muscles, mainly the lateral cricoarytenoid (LCA) and thyroarytenoid (TA). These muscles are suspected of being hyperactive16 and this idea is supported by the successful treatment using chemical denervation of the TA muscle.17 Vocal quality is strain-strangled with phonation effort and audible spasms. Hoarseness, harshness, and tremor are common. Dysphonia occurs in different degrees of severity. Although we could find no specific reports of LEMG investigation of this patient population, the more severe vocal pathologies seem to present, the longer are the delays between electrophysiological activation and sound production. The purpose of this study was to compare the degree of severity of dysphonia in patients with adductor laryngeal dystonia with the latency between the electrophysiological activation of the TA muscle and the onset of phonation. METHOD This study was developed at the Neurolaryngeal Clinic of the Universidade Federal de Sa˜o Paulo, Brazil, and it was fully approved by the local Ethics Committee. Thirty-six participants were submitted to LEMG and voice perceptual assessment between January 2004 and December 2006. All of them were duly informed about the procedures and signed a formal agreement to participate in the study. Twenty-one of the participants were diagnosed with adductor laryngeal dystonia and 15 were normal adults, who comprised the control group. Participants underwent complete neurological and ENT evaluation, including transnasal fiberoptic laryngeal examination. The assessment was based on a specific protocol developed to diagnose laryngeal dystonia.17 The voice perceptual analysis was made by three speechpathologists/voice specialists who had no previous knowledge of latency values or patient condition. The three speech language pathologists listened to the samples at the same

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Latency Time in Abductor Laryngeal Dystonia

time in a silent room, using two speakers and the result was obtained by consensus. The four voice tasks evaluated were (1) sustained vowel /e/ at a normal pitch and loudness; (2) sustained vowel /i/ in ascending and descending glissando; (3) sustained vowel /i/ at high pitch; and (4) phrases containing words with voiced and voiceless phonemes spoken in whispered and loud speech, as described previously.18 A 4-point ordinal scale was used. They classified the degree of dysphonia severity in the following scale: 0—no alteration perceived; 1—mild degree of dysphonia; 2—moderate degree of dysphonia; and 3—severe degree of dysphonia. The presence/absence of spasms and voice quality stability during tasks were the main criteria for this dysphonia evaluation. Nihon Kohden 2-channel electromyography instrumentation (Nihon Kohden Corporation, Tokyo, Japan) was used with a monopolar needle to record transcutaneous electromyographic responses of the left TA muscle. Head set microphone was positioned 5 cm from the patient’s mouth. Patients received no anesthetic or sedation. THe ONe Surface reference and earth electrodes were placed, respectively, on clavicle and sternal region. The superior channel (channel 1) registered the electrical activity and the inferior channel (channel 2), the vocal signal (sustained /i/ at confortable pitch and loudness). The needle was introduced through the cricothyroid membrane, approximately 0.5 mm to the left of the sagittal plane and rotated it superiorly and laterally about 30 –45 , continuing the insertion until we identified electrical activity, usually at around 2 cm. Position of the needle was verified in the TA muscle by observing electrical activity during phonation and significant decrease of the electrical signal during the resting state and calm breathing. With the needle positioned on the TA muscle, sound produced by the electromyography was disabled to avoid interference with the voice recording procedure and recorded the data with a sensitivity of 100–200 mV/div and a speed of 200 ms/div. The registers were monitored and saved in the computer. Measures of the latency were done from the rise of the electrical signal of the TA muscle until the first graphic record of the patient’s voice in the second channel (Figure 1).

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Otolaryngologists were blinded to the SLPs’ assessment. In the same way, SLPs did not know the latency values or the patients’ condition before the perceptual evaluation. The Mann-Whitney test was used to compare the latency between groups and Spearman’s analysis to verify the correlation between the degree of dysphonia severity and the latency time set at a significance level of 5% (P < 0.05). RESULTS The mean value of latency time between phonation onset and TA electrical activation was obtained for study and control groups (Table 1). Patients with dystonia presented a significantly higher latency time (569.57 milliseconds) in comparison with controls (202.93 milliseconds), P<.001. The correlation between the dysphonia severity degree and the latency time was determined (Table 2). Results showed that the dysphonia severity degree was significantly correlated with the latency time (p¼.02): 332.33 milliseconds for mild degree (grade 1); 426.33 for moderate degree (grade 2); and 791.89 milliseconds for severe dysphonic degree. DISCUSSION The latency between muscular activation and the onset of phonation reflects the time necessary for vocal fold adduction, vocal fold tension, and formation of the mucosal wave brought about by the airflow generated by the subglottic pressure. The intrinsic muscles adjust the position of the vocal fold and the TA activity precedes phonation onset. Although most authors11–15 consider 200 milliseconds as the upper limit for this latency in normal subjects, Hillel16 obtained values up to 400 milliseconds in 11 normal subjects (mean ¼ 309 milliseconds; median ¼ 304 milliseconds). The mean latency for our control group was 203 milliseconds (standard deviation [SD] ¼ 72 milliseconds), in general agreement with the literature11–15 but less than that reported by Hillel.16 None of our control subjects had latencies greater than 321 milliseconds (Table 1).

FIGURE 1. EMG measurement of latency time in patients with laryngeal dystonia. Channel 1: electrical activity. Channel 2: phonation (vocal signal). Arrow: latency time.

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TABLE 1. Individual Values, Mean, and SD of the Latency Between Phonation Onset and TA Electrical Activation in the Study Group (Dystonia) and in the Control (Ctrl) Latency Time (ms)

TABLE 2. Individual Values, Mean, and SD of the Dysphonia Severity Degree and Latency Time (ms) Between TA Electrical Activation and Phonation Onset Dysphonia Severity Degree

ID Number

Ctrl

Dystonia

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

266 204 321 123 236 196 197 312 95 161 212 240 218 200 63

320 813 345 371 318 530 333 1157 582 989 544 597 386 680 558 373 281 417 1141 789 437

Mean SD

202.93* 71.74

569.57* 268.16

Mann-Whitney test *P < 0.001.

All but one patient with adductor laryngeal dystonia in this study exhibited a delay between the electrical activity and onset of phonation greater than 300 milliseconds (Table 1). However, eight patients with adductor laryngeal dystonia had latency values within Hillel’s normal range even though values for most patients exceeded 500 milliseconds and some had values more than 1 second. Hillel16 also reported latency values for dystonic patients within the range of the normal controls during the task of producing a sustained vowel /i/ (lower value ¼ 215 milliseconds). Statistic analysis revealed that the latency values in these dystonic patients were significantly greater than those of normal controls (Table 1). Thus, although a normal latency from an LEMG is not enough to exclude the diagnosis of dystonia, an increased latency time (>400 milliseconds) supports the diagnosis of laryngeal dystonia, as suggested by Hillel.16 Methodological differences may explain differences from data to Hillel’s. Voice task during EMG register was emission of the vowel /i/ at comfortable pitch and loudness, likewise Hillel (‘‘eeee’’).16 Although different EMG devices and needle should not explain different results, the use of anesthetic should explain it. Hillel’s article showed use of anesthetic (lidocaine 2%) into the airway through the cricothyroid membrane before EMG. Others12–15 used oropharyngeal anesthetic. Differently from both, any anesthetic was used in these participants. Injection of lidocaine 2% by Hillel may modify afferents, and

Latency (ms)

1 1 1

345 371 281

Mean SD

332.33* 46.32

2 2 2 2 2 2 2 2 2

320 318 530 333 582 386 558 373 437

Mean SD

426.33* 105.27

3 3 3 3 3 3 3 3 3 Mean SD

813 1157 989 544 597 680 417 1141 789 791.89* 261.48

Spearman’s correlation test *P ¼ 0.02.

this may increase latency time. This aspect may explain these values below Hillel’s and agreement with other authors which did not use laryngeal anesthetic before EMG. In an attempt to understand the existence of normal latency values in some dystonic patients, the latency values were compared with the degree of severity for the dysphonia, using a scale of perceptual analysis (Table 1). Clinical observations suggested that cases of severe dysphonia had increased latency values. More severe dysphonia is probably associated with stronger vocal fold adduction. In the physiology of voice production, the stronger the adductor forces, the higher the subglottic pressure required to initiate vocal fold’s mucosal vibration and the initiation of phonation. Thus, it is possible to infer that the stronger the adductor forces, the longer the time that will be required for the airflow to be released through the vocal folds. Statistical analysis showed that there was a significant correlation between latency time and degree of dysphonia severity (Table 2). That suggests that patients with longer latency times also should have moderate to severe degrees of dysphonia. All three

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Latency Time in Abductor Laryngeal Dystonia

patients with mild dysphonia (classified as grade 1) had latencies greater than one SD above the mean of normal controls, but below the 400 milliseconds norm of Hillel. Five of nine patients with moderate dysphonia (grade 2) presented latencies times under 400 milliseconds, the remaining four had longer latencies. As would be predicted from the inference above, all the patients with severe dysphonia had latencies greater than 400 milliseconds with a mean value of 792 milliseconds. Cannito et al19 noted that patients with severe adductor spasmodic dysphonia received the greatest improvement in voice production after Botox injection. Clinical experience of the group suggests better results in severe adductor dystonia, except when associated with supraglottic compromising or tremor. Therefore, latency time may be another support parameter for vocal quality prognosis after botulinum injection.

CONCLUSION For patients with adductor laryngeal dystonia, the latency between electrophysiological activation of the TA muscle and the onset of phonation is directly related to the degree of severity of the dysphonia. Mild dysphonia patients may have latencies that overlap the range of normal subjects reported in some series, but patients with severe dysphonia have significantly prolonged latencies.

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