Annals of Otology, Rhinology & Laryngology 120(7):465-473. © 2011 Annals Publishing Company. All rights reserved.

Spasmodic Dysphonia: Onset, Course, Socioemotional Effects, and Treatment Response Kristine Tanner, PhD; Nelson Roy, PhD; Ray M. Merrill, PhD; Cara Sauder, MA; Daniel R. Houtz, MA; Marshall E. Smith, MD Objectives: This investigation explored the onset, progression, socioemotional effects, and treatment outcomes of spasmodic dysphonia (SD), Methods: A cross-sectional epidemiological approach was used to examine questionnaire responses from 150 individuals with SD, Results: Symptoms of SD (mean age at onset, 46 years) began gradually in 76% of cases and were progressive (ie, failed to plateau) in 34% of cases. Botulinum toxin A (Botox) helped to attenuate voice symptoms in 91% of cases; however, the scores on the Voice-Related Quality of Life questionnaire (V-RQOL) were not associated with this effect. The V-RQOL scores improved with time since symptom onset, independent of age and treatment. The patients with only SD experienced onset, course, and progression of symptoms similar to those of the patients with SD and coexisting vocal tremor. Conclusions: The symptoms of SD begin gradually and worsen over time. New evidence indicates that SD symptoms may continue to progress without plateau in at least a subset of patients. Individuals with SD and coexisting vocal tremor experience symptom trajectories similar to those of patients with SD only. Although Botox may attenuate voice symptoms, these effects do not appear to be strongly related to the V-RQOL scores. These results provide new and valuable insights regarding the onset, course, progression, and treatment of SD. Key Words: ansa cervicalis reinnervation, Botox, botulinum toxin A, recurrent laryngeal nerve denervation, spasmodic dysphonia, voice disorder, Voice-Related Quality of Life, V-RQOL.

years In 130 cases of SD, Variability in the course of SD was also observed by Borenstein et al (unpublished observations, 1978): 2 of 10 individuals reported that their symptoms had worsened during an 18-year period, whereas the remaining 8 reported symptom improvement or plateau, Aronson (unpublished observations, 1979) reported a median onset age of 50 years in 100 cases of SD, with symptoms progressing during the first year after onset. Later, Aronson'*^ concluded that SD symptoms often plateau within the first year after onset, although some individuals experience progressive worsening over time. In a group of 29 cases, Schaefer" observed that SD symptoms remitted intermittently in the first 2 years after onset, and that symptom severity was variable years after onset, Izdebski et al'^ examined 200 case histories of patients with SD to identify risk factors for the disease and to characterize symptom onset. The results indicated that 84% of patients reported a gradual onset of voice symptoms. Ultimately, the voice symptoms plateaued between 6 and 9

INTRODUCTION Spasmodic dysphonia (SD) is a relatively rare, action-induced, task-specific focal laryngeal dystonia with no known cure,'""* Adductor, abductor, and mixed variants — with and without coexisting vocal tremor — have been described, with adductor SD being the most prevalent,^'^ The cause of SD is unknown. The treatments are symptom-based and do not fully address the voice complaints,^ Patient counseling related to prognosis, symptom progression, and individual treatment outcomes is often based on anecdotal reports and clinical experience. Relatively little is known regarding the onset, course, and progression of SD, and only a handful of investigations have examined SD symptom development. In a sample of 34 cases of SD, Aronson et al^ found that the mean age of SD onset was 44 years. In 94% of those cases, the severity of voice symptoms fluctuated after the initial onset, but the dysphonia never resolved, Brodnitz^ reported a mean onset age of 50

From the Department of Communication Sciences and Disorders (Tanner, Roy), the Division of Otolaryngology-Head and Neck Surgery (Tanner, Roy, Smith), and the Voice Disorders Center (Sauder, Houtz), The University of Utah, Salt Lake City, and the Department of Health Science, Brigham Young University, Provo (Merrill), Utah. This work was supported in part by a University of Utah College of Health Research and Creative Grant. Correspondence: Kristine Tanner, PhD, Voice Disorders Center, Surgical Specialty Center, 729 Arapeen Dr, Salt Lake City, UT 84108.

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months after onset. In general, these reports indicate that SD often begins in midlife and may plateau within 1 year after onset. However, some variability in the course and progression has also been observed, indicating a need for large-scale, systematic epidemiological studies to clarify the onset and possible course(s) of SD. Botulinum toxin A (Botox) injection of the laryngeal musculature remains the gold standard for SD management, despite the limitations of being an incomplete, short-duration, symptom-based treatment.'' Many studies have examined the effects of Botox on SD symptoms, including several that investigated its impact on patient-based quality-oflife measures.'^'^ However, these investigations have produced mixed results related to the degree of improvement in quality-of-life measures observed with Botox injection. Information is lacking regarding the effectiveness of Botox injection over time in relation to individual disease course(s). Recurrent laryngeal nerve section, crush, and avulsion procedures have also been offered as surgical procedures for SD symptom management, but have had relatively poor or mixed long-term effects .2*^"^^ More recent denervation-reinnervation procedures show promise in addressing SD symptoms,^^'30 yielding evidence of voice improvement 4 years after surgery .3' However, longer-term follow-up data remain somewhat limited.^^ In summary, few data exist regarding SD onset, course, and symptom trajectory. Large-scale epidemiological data are required to characterize disease course and progression, as well as to guide future treatment delivery and development. The purpose of this study was to examine the onset, course, and progression of SD symptoms (with and without coexisting vocal tremor), treatment frequencies and outcomes, and social and emotional effects in a fairly large cohort of patients. METHODS Participants. The participants included 150 individuals with SD who were identified and recruited at the University of Utah Voice Disorders Center during voice evaluation clinic appointments, during Botox injection appointments, or via letter and subsequent telephone contact based on chart reviews (Institutional Review Board approval 00025341). A consensus diagnosis of SD was assigned by a multidisciplinary team including a laryngologist (M.E.S.) and 1 of 4 speech-language pathologists (K.T., N.R., C.S., D.R.H.) who specialize in voice disorders and have substantial experience in the diagnosis and treatment of SD. The diagnosis was confirmed by use of an extensive assessment protocol including

a detailed case history, auditory-perceptual evaluation, and videolaryngostroboscopy. In some ambiguous cases, the failure of voice therapy served to corroborate the diagnosis and exclude other diagnostic possibilities, including muscle tension dysphonia.2'3.33-36 Given the absence of a gold standard test for the diagnosis of SD, there always exists some non-zero possibility of an incorrect diagnosis. However, the strict diagnostic criteria outlined above, combined with the expertise of the clinicians, rendered the likelihood of misclassification improbable. Individuals were excluded from the study if they had moderate or severe hearing loss or documented cognitive impairment. Data Collection. This cross-sectional, descriptive study used a previously validated questionnaire^'^-^o adapted for individuals with SD. The questions included but were not limited to case history, onset, progression, treatment response, and functional, social, and emotional effects. The Short Form 36 (SF36) and the Voice-Related Quality of Life (V-RQOL) questionnaires were also included.^' The SF-36 includes questions related to overall health, including vitality, physical functioning, bodily pain, general health perceptions, physical, emotional, and social role functioning, and mental health. The SF-36 is a reliable, validated questionnaire that has been used to determine the relative health benefits of various treatments and to compare the impact of various disease processes. The V-RQOL is a validated, reliable, 10-item instrument that has been used to determine the impact of voice impairment on quality of life and as an outcome measure in patients with voice disorders. These questionnaires were administered orally'*^ during a 1-hour interview by trained examiners who were periodically audited for accuracy of administration and scoring. Data collection was completed during a 14-month period. Statistical Analysis. Data were examined for frequencies, proportions, means, and standard deviations. Cross-tabulations were used to perform bivariate analyses, with statistical significance based on the y} test for independence. Omnibus F statistics. Student Newman-Keuls comparisons, and linear regression analyses were undertaken for selected variables. Statistical significance was determined at an alpha level of 0.05. Analyses were performed with SAS version 9.1 (SAS Institute Inc, Cary, North Carolina). RESULTS Diagnostic and demographic data for study participants are presented in Table 1. The majority of participants had a diagnosis of adductor SD. The age ranges were equally distributed among the three

Tanner et al. Spasmodic Dysphonia

TABLE 2. ONSET AND PROGRESSION OF SPASMODIC DYSPHONIA SYMPTOMS

TABLE 1. FREQUENCY DISTRIBUTIONS OF PARTICIPANTS ACCORDING TO DEMOGRAPHIC VARIABLES Variable Gender Male Female Diagnosis Adductor spasmodic dysphonia Adductor spasmodic dysphonia + vocal tremor* Abductor spasmodic dysphonia Mixed spasmodic dysphonia Age 23-49 y 50-59 y 60-69 y 70-1-y Race/ethnicity White, non-Hispanic Other Education High school (or GED) Associate degree BA.BS MA, MS PhD, MD, ID, etc Gross annual income $60,000 Prefer not to answer

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No.

%

56 96

37 63

104 41

70 27

2 3

1 2

28 43 37 42

18 29 25 28

149 1

99 1

41 35 40

27 23 27

24

16

10

7

8 17 21 76 28

5 11 14 51 19

*Vocal tremor was only observed to coexist with adductor spasmodic dysphonia.

older age ranges, and the fewest participants were in a fourth, younger age range. The race or ethnicity (99% white) and gender representations (94 female, 56 male) in this study were also consistent with those of the general population of individuals with SD 12,43,44 -phe participant recruitment rate was 78% (ie, 150 of the 192 patients with SD who were invited to participate ultimately completed the study). Onset and Progression ofSD. Findings related to the onset and progression of SD symptoms are presented in Table 2. The mean age of onset was 46 years (standard deviation, 15 years). At the time of the study, 86% of participants had had SD symptoms for 4 years or more. The majority of participants reported that their voice problems began gradually. About one third (51) indicated that their voice symptoms had worsened over time (mean, 16 years since onset; standard deviation, 14 years since onset). For 29 cases (20%; mean, 17 years since onset; standard deviation, 14 years since onset), voice

Variable Onset (mean age, 46 years; SD, 15 years) Sudden Gradual Don't know First noticed the voice problem? 1-6 months ago 7-12 months ago 1-3 years ago 4-9 years ago 10+ years ago

No. 31 104 1

23 76 1

2 5 12 28 88

1 4 9 21 65

Has the voice problem... Gotten better? 32 21 Worsened over time? 51 34 Stayed the same? 67 45 (If the voice problem has worsened over time) did it worsen... Quickly? 7 13* Gradually? 48 87* (If the voice problem has worsened over time) is it still worsening? Yes 29 53* No 25 45* Don't know 1 2* How long did the voice problem take to plateau? 1 -6 months 2 5 7-12 months 4 10 1-3 years 12 29 4-9 years 10 24 10-1-years 13 32 *Percentage based on subset of patients who reported that voice problem had worsened over time.

symptoms were still worsening at the time of the study. Of the 41 subjects who reported an eventual plateau of symptoms, about one third indicated that the length of time until the plateau occurred was 10 years or more. SD Treatment. Findings on treatment administration, including treatment methods and frequencies for all participants, are reported in Table 3. Nearly all individuals in this study (ie, 89%) received treatment for their voice symptoms. The treatment most frequently received was Botox injection, followed by voice therapy, medication, and surgery. No statistically significant gender differences were observed for Botox, voice therapy, surgery, or medication treatments. Ninety-one percent of participants who received Botox indicated that it helped their voices. For those who received voice therapy, 22% reported that it helped their voices. For medication, 29% reported voice improvement, and for surgery, 45% improved. Five of the 11 participants had received recurrent laryngeal nerve denervation-ansa cervi-

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TABLE 3. FREQUENCIES OF SPASMODIC DYSPHONIA TREATMENTS Variable Received treatment for voice problem? Yes No Received botulinum toxin (Botox)? Yes No Helped voice? Received voice therapy? Yes No Don't know | Helped voice? ' Received surgery? Yes No Helped voice? Received medication? Yes No Helped voice? How long ago did you receive Botox? 0-2 weeks ago 3-4 weeks ago 5-7 weeks ago 2-3 months ago 4-5 months ago 6-12 months ago 1 -3 years ago 4-9 years ago lO-i- years ago How long ago did you receive voice therapy? 0-2 weeks ago 3-4 weeks ago 5-7 weeks ago 2-3 months ago 4-5 months ago 6-12 months ago 1 -3 years ago 4-9 years ago 10-1- years ago How long ago did you receive surgery? 0-2 weeks ago 3-4 weeks ago 5-7. weeks ago 2-3 months ago 4-5 months ago 6-12 months ago 1 -3 years ago 4-9 years ago 10-1- years ago How long ago did you receive medication? 0-2 weeks ago 3-4 weeks ago 5-7 weeks ago 2-3 months ago 4-5 months ago 6-12 months ago 1 -3 years ago 4-9 years ago 10-1- years ago

No.

%

144 6

96 4

134 16 124

89 II 91*

89 60 1 20

59 40 1 22*

11 139 5

7 93 45*

22 128 10

15 85

29*

16 20 13 35 12 14 15 7 4

12 15 9 26 9 10 11

4

5

1 0 1

1 0 1

3

3

2 12 24 41

2 14 27 47

0

0

0

0

0 0 0 1 3 3

0 0 0 9 27 27 37

4 8

0 0 2 1 4 4 2 12

5 3

24 0 0

6 3

12 12 6 37

*Percentage based on subset of patients who received specified treatment and reported improvement.

calis reinnervation performed by one of the authors (M.E.S.) within the past 3 years, and 1 of these patients received subsequent Botox treatments. Short Form 36. Scores from the SF-36 were compared with normative values, and differences based on demographic variables and treatment types were examined. The eight subtests from the SF-36 include physical functioning, role limitations due to physical health and emotional stresses, energy or fatigue, emotional well-being, social functioning, pain, and general health. High scores reflect better function related to each subtest, and low scores indicate limitations in function. No significant differences were observed between the participants with SD and the normative scores for each subtest. Statistically significant differences were observed between men (mean, 86.4; standard deviation, 12.4) and women with SD (mean, 80.7; standard deviation, 14.3) on the emotional well-being subtest (p = 0.022), but both groups exceeded normal limits (74.7). To examine general health along with social and emotional functioning over time in individuals with SD, as well as possible changes with treatment, we analyzed the SF-36 scores. After adjusting for age, gender, race, and income, we observed no significant associations between adjusted SF-36 scores and length of time since SD symptom onset. For treatment type, only Botox was associated with general health (p = 0.034); individuals who received Botox had significantly lower (poorer) general health scores than did those who did not receive Botox. Similarly, individuals who took medication for their voice symptoms had significantly lower emotional well-being scores than did those who did not take medication for SD (p = 0.005). No other significant associations based on the SF-36 subtests were identified for treatment type. To examine adjusted SF-36 scores in relation to time since last treatment, we undertook regression analyses. For Botox, associations with the energy or fatigue subtest approached statistical significance (p = 0.055), with the category "3 to 12 months since last treatment" having higher (better) scores, followed by 3 weeks to 3 months, 0 to 2 weeks, and 12 plus months. No other significant associations were observed for time since last Botox injection. For voice therapy, significant associations were observed in terms of role limitations due to physical (p < 0.004) and emotional (p < 0.030) stresses and in terms of social functioning, with increases in the length of time since treatment associated with better functioning. Voice-Related Quality of Life. The V-RQOL

Tanner et al, Spasmodic Dysphonia

469

scores range from 0 to 100, with higher numbers indicating a better quality of life based on voice function. The V-RQOL has three scales, including a social-emotional domain, a physical function domain, and a total score. The mean V-RQOL scores from the participants with SD were significantly below normative scores for the social-emotional domain (SD, 60.9; norm, 98.8), the physical function domain (SD, 60.0; norm, 97.3), and the total score (SD, 57.3; norm, 98.0).^*'

medication), SF-36 mean scores, or V-RQOL mean scores. However, 56% of those with SD plus tremor reported that medication helped their voice problem, as compared with 21% of those with SD only (p = 0.053). This finding appeared to be related, in part, to gender differences. That is, the percentage of men who reported that medication helped their voices was 25% for SD plus tremor, versus 38% for SD only; the percentage for women was 80% for SD plus tremor, versus 13% for SD only.

To examine the quality of hfe related to voice production over time in individuals with SD, as well as possible changes related to treatment, we obtained adjusted V-RQOL scores. After adjusting for age, gender, race, and income, the length of time since SD onset was significantly associated with the total score (p - 0.002) and the physical function domain (p = 0.001), and approached significance with the social-emotional domain (p = 0.070). That is, increases in the length of time since SD onset corresponded with significant increases (improvement) in V-RQOL scores. However, the V-RQOL scores remained significantly below normal scores 10 or more years after SD onset.

DISCUSSION This investigation revisited the onset, course, and progression of voice symptoms, the frequency and effects of several conventional treatments, and the social and emotional effects of SD. This large-scale, cross-sectional epidemiological study provides evidence to corroborate some long-standing beliefs surrounding SD; however, and perhaps more importantly, our findings also challenge others. A discussion of each of the salient findings and related observations, as well as how they compare to previous research, follows.

To examine adjusted V-RQOL scores in relation to time since last treatment, we undertook regression analyses. For voice therapy, the V-RQOL scores for the social-emotional (p = 0.075) and physical function (p = 0.063) domains were higher, the longer the duration since last treatment. No significant associations between V-RQOL scores and the length of time since last treatment were observed for the Botox or medication treatments. SD With Coexisting Vocal Tremor Versus SD Only. Twenty-seven percent of the participants with SD in this study also had coexisting vocal tremor. Only the adductor variant of SD was observed to coexist with vocal tremor; no participants in this study with abductor or mixed variants of SD had coexisting vocal tremor. The distribution of women and men was similar between the two subgroups; however, those with SD plus tremor (mean, 64.1 years; standard deviation, 11.8 years) were significantly older (p < 0.050) than those with SD only (mean, 59.7 years; standard deviation, 12.1 years). Differences between participants with SD plus tremor versus those with SD only were examined in terms of gender, time since symptom onset, course and progression, treatment frequency and response, and SF-36 and V-RQOL variables. No significant differences were observed between the subgroups with SD plus tremor and SD only in terms of gender, time since SD onset, symptom progression, frequency of treatments (including Botox, voice therapy, surgery, and

SD Symptom Manifestation. In general, SD has been reported in the literature to have a gradual symptom onset, with some worsening during the first year or two, followed by a plateau therafter'O''^ (also Aronson, unpublished observations, 1979). Findings from the present investigation indicate that at least a subset of patients with SD may experience a more protracted worsening of voice symptoms thari has been previously reported. One third of the participants in this study reported that their voice symptoms continued to progress for, on average, 4 years or more after the initial onset of symptoms. In fact, at the time of data collection, 20% of participants — with an average of 17 years since symptom onset — said that their voice symptoms were still progressing. Although SD symptom progression has been reported by others, the protracted time frame associated with this progression in a subset of patients is decidedly at odds with previous assumptions surrounding SD symptom manifestation, and would appear to directly conflict with previous reports that SD only progresses during the first year after onset and then plateaus"'''^ (also Aronson, unpublished observations, 1979). In at least a subset of individuals with SD, symptoms may be expected to progress for a decade or more after onset. Although others have reported some "symptom variability" in similar percentages of patients with regard to SD manifestation" (also Boren stein, unpublished observations, 1978), findings from this large-scale investigation suggest a more progressive nature of SD symptoms over time. Unfortunately, these findings

470

Tanner et al. Spasmodic Dysphonia

do not easily explain why some individuals' symptoms plateau while others' do not. In general, our results provide new evidence that SD can be a disabling, progressive condition with a variable symptom trajectory. Another finding regarding the manifestation of SD symptoms warrants attention. Consistent with previous reports'^-'^ (also Aronson, unpublished observations, 1979), the majority of participants in this study described the onset of their voice symptoms as gradual. However, 23% reported that their voice problems began suddenly. Additionally, 21 % of participants said that their voice symptoms had "gotten better" over time. As discussed above. It is clear that although some patients experience progressive worsening of voice symptoms with time, it is possible that others experience symptom variability or plateau. Although these perceptions of variability may be related to Botox treatment effects, it is also possible that another subset of patients experience a waxing and waning course of SD manifestation, or alternatively, that certain individuals do experience partial remission of symptoms. Certainly, the possibility of a sudden onset of voice symptoms in one quarter of SD cases is of great importance clinically, as muscle tension dysphonia — a voice disorder that often masquerades as SD — is often characterized by sudden onset with relapsing or remitting symptoms. Findings from the present investigation not only indicate several possible courses or progression patterns in SD, but also support the need for ongoing research to improve the differential diagnosis and clinical characterization of voice disorders, including SD, SD Treatment. Clinical practice guidelines have identified Botox injections as the recommended treatment for SD,^^ Our results confirm that Botox was the most common treatment for individuals with SD, as 89% of participants in this study had received Botox on at least one occasion. After Botox, the treatments most frequently received by participants were voice therapy, medication, and surgery. The vast majority of patients who received Botox (91%) reported that it "helped the voice," However, these responses were not consistent with the VRQOL scores, which were not associated with the Botox treatment cycle. At first glance, these data may appear incongruous; however, additional consideration identifies several possible explanations for these findings. For example, it is possible that the dichotomous question of whether Botox treatment "helped the voice" was not sensitive to the amount or grade of improvement with treatment. Perhaps Botox helped, but it did not fully resolve their symptoms. This would be consistent with pre-

vious reports on the effectiveness of Botox in attenuating but not eliminating voice complaints,'3"'^ Also, perhaps the V-RQOL is more sensitive to overall social and emotional functioning with respect to the voice, and is less associated with impairment level. The apparent disconnect between impairment ratings and V-RQOL scores has been reported previously,'^ For instance, Braden et al'^ also recently documented relatively weak correlations between the V-RQOL and an equal-appearing interval scale patient-based rating of voice impairment before and after Botox treatment, Paniello et al'^ also found a weak relationship between the V-RQOL and other clinical and patient-based measures after Botox treatment. Like these studies, ours raises additional questions surrounding the nature of the benefit of Botox as a treatment for SD, It seems that although patients report voice improvement with Botox, this does not necessarily improve the quality of life over time. It should be noted, however, that this study employed a cross-sectional design, and thus, withinsubjects pre-Botox-post-Botox comparisons were not possible. Such studies would shed additional light on the complex relationship between impairment-level measures such as improved voice quality versus patient-centered handicap measures such as the V-RQOL, Clearly, patients would not continue to return repeatedly to voice clinics, often traveling great distances, if Botox did not help to attenuate their voice symptoms. But it is possible that this treatment does not significantly influence their social and emotional functioning related to the voice, or that it is insufficient in managing these symptoms consistently. Regardless, these data provide additional evidence of the need for better treatments to manage SD over time. Eleven participants in this study had surgery for their voice problems. Analysis of the results identified significantly higher V-RQOL scores for participants who had surgery to address their voice problems in comparison to those who pursued other treatments. Five participants reported that the procedure helped their voices, and of those, 4 had received recurrent laryngeal nerve denervation-ansa cervicalis reinnervation procedures within the past 3 years. Given the very small number who received surgery in this study, combined with additional factors such as selection bias, potential placebo effects, and the lack of long-term follow-up data, we are extremely cautious in interpreting treatment data from the surgical group. Although it does appear that surgical management of SD might be a promising avenue for future research, we recommend caution in interpreting these results, SD Plus Tremor Versus SD Only. Perhaps the

Tanner et al. Spasmodic Dysphonia

most interesting finding related to comparisons of patients with SD plus vocal tremor and those with SD only was the similarity in SD symptom onset, course, and progression between the two subgroups. Vocal tremor is believed to be progressive,'*^'''^ thus presumably, patients with SD plus tremor would experience greater voice deterioration over time, perhaps with corresponding changes in SF-36 and V-RQOL scores. Yet no differences were observed in this study between the subgroups with SD plus tremor and SD only in regard to the onset or progression of symptoms or to the SF-36 or V-RQOL data. These findings suggest that at least a subgroup of individuals with SD may experience progressive worsening of voice symptoms similar to that experienced with vocal tremor. In this study, 27% of participants had vocal tremor in addition to SD — a finding that is consistent with previous reports of the incidence and prevalence of SD and vocal tremor comorbidity.''^'^ ' Only 25% of men versus 80% of women with SD plus tremor who received medication (eg, beta blockers) reported that this treatment helped the voice. However, controlled studies are needed to further examine the effects of medication on SD plus vocal tremor. Coping with SD. Although the patients who received Botox injections did not have significant changes in V-RQOL scores with treatment, a trend for increasing V-RQOL scores over time was found. This increase in V-RQOL scores based on length of time since SD symptom onset was statistically significant and independent of age effects, suggesting that social and emotional function improves with time in individuals with SD, despite worsening of symptoms in some cases. However, it is important to note that even the highest (best) scores in this study were well below normative values for the V-RQOL domains. After adjusting for age, gender, race or ethnicity, and income, no significant differences between this group of participants and SF-36 normative values were observed. These findings indicate that individuals with SD are comparable to the general population in overall health and emotional wellbeing. It should be noted that the overwhelming majority of participants in this study received treatment. Combined with the relatively long duration of SD, it

471

is possible that the relatively normal SF-36 scores in patients with SD might refiect positive adjustments related to living with a chronic condition. Perhaps if the SF-36 were administered immediately after onset, the impact of SD on overall health and emotional well-being would be more apparent. In general, it appears that the V-RQOL scores increase with time, but fail to approach normative values, despite positive coping adjustments. Additional Considerations. Several factors warrant attention regarding the interpretation of the findings in the present investigation. First, the participants in this study represent a convenience sample of patients seen at the University of Utah Voice Disorders Center. Certainly, issues surrounding patient identification, selection, and potential placebo or bias effects should be considered. For example, patients who were only seen for an initial evaluation but did not return to receive Botox, or did not have a positive experience with treatment, may have been less motivated or accessible to complete the study. Additionally, although the questionnaire data were collected anonymously, it is possible that patients who received Botox regularly felt more persuaded to report that it helped their voice symptoms. It is also possible that because of the cross-sectional design of the study, we failed to detect the consistent improvement in V-RQOL scores with regular Botox injection that has been reported previously. These limitations notwithstanding, this epidemiological investigation represents one of the largest and most thorough evaluations of SD yet undertaken. CONCLUSIONS Spasmodic dysphonia is a chronic, disabling condition that typically begins gradually in the fifth decade of life. Contrary to previous assertions, SD can be a progressive condition that worsens with time, and it fails to plateau in one third of cases. Patients with SD and coexisting vocal tremor experience a voice symptom trajectory similar to that of those with SD only. Most patients report some attenuation of voice symptoms with Botox injections, although we did not observe commensurate improvements in V-RQOL scores. This investigation provides new evidence that challenges previous assertions regarding the onset, progression, and treatment of SD.

Acknowledgments: The authors gratefully acknowledge the work of university students Sara Carter, Anya Currier, Julie ChoulesRobinson, Sarah Groves, Priscilla Hansen, Kamille Kimber, Ann Merrill, Rachel Sjoberg, and Stacee Sullivan, who assisted with data collection. They also thank the physicians, nurses, and office staff at the University of Utah Hospital Otolaryngology Clinics for their assistance during the participant identification and recruitment process.

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