JSLHR

Research Article

Muscle Weakness and Speech in Oculopharyngeal Muscular Dystrophy Amy T. Neel,a Phyllis M. Palmer,a Gwyneth Sprouls,a and Leslie Morrisona

Purpose: We documented speech and voice characteristics associated with oculopharyngeal muscular dystrophy (OPMD). Although it is a rare disease, OPMD offers the opportunity to study the impact of myopathic weakness on speech production in the absence of neurologic deficits in a relatively homogeneous group of speakers. Methods: Twelve individuals with OPMD and 12 healthy age-matched controls underwent comprehensive assessment of the speech mechanism including spirometry (respiratory support), nasometry (resonance balance), phonatory measures (pitch, loudness, and quality), articulatory measures (diadochokinetic rates, segment duration measures, spectral moments, and vowel space),

tongue-to-palate strength measures during maximal isometric and speechlike tasks, quality-of-life questionnaire, and perceptual speech ratings by listeners. Results: Individuals with OPMD had substantially reduced tongue strength compared to the controls. However, little impact on speech and voice measures or on speech intelligibility was observed except for slower diadochokinetic rates. Conclusions: Despite having less than half the maximal tongue strength of healthy controls, the individuals with OPMD exhibited minimal speech deficits. The threshold of weakness required for noticeable speech impairment may not have been reached by this group of adults with OPMD.

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New Mexico Health Sciences Center, and an OPMD registry has been established recently. The dysphagia characteristics associated with OPMD have been described by a number of authors (Duranceau, Beauchamp, Jamieson, & Barbeau, 1983; Duranceau, Letendre, Clermont, Lévesque, & Barbeau, 1978; Palmer et al., 2010; Young & Durant-Jones, 1997), but less information is available about speech. Autopsy and imaging studies have noted loss of muscle tissue in structures involved in speech, including thinning of the pharyngeal wall (Chang, Chang, Cheung, & Kong, 1993; Little & Perl, 1982) and atrophy of the masseter (King, Lee, & Davis, 2005), anterior digastric muscle, and diaphragm (Little & Perl, 1982). The tongue is greatly affected in OPMD: Autopsy of one French Canadian individual with OPMD revealed replacement of 80% of tongue tissue with fat (Little & Perl, 1982). Imaging studies confirm moderate to severe fatty infiltration of the tongue (Chang et al., 1993; King et al., 2005). With these issues, difficulties with speech and voice in the form of flaccid dysarthria are expected to occur. In a cohort of 49 New Mexicans with OPMD, 76% had dysphagia and 41% were judged by a neurologist to have dysarthria (Becher et al., 2001). Duranceau et al. (1983) commented that voice changes are common among patients with OPMD, ranging from “simple rasping to an extremely nasal voice” (p. 828). Young and Durant-Jones (1997), in describing the dysphagia associated with OPMD, observed speech and voice problems

culopharyngeal muscular dystrophy (OPMD) is a rare genetic myopathic disease characterized by ptosis and dysphagia. OPMD symptoms generally appear in middle age with ptosis and dysphagia progressing slowly over many years (Brais, Rouleau, Bouchard, Fardeau, & Tome, 1999). The skeletal muscle cell death that causes weakness in OPMD is associated with the abnormal aggregation of proteins in cell nuclei, although the mechanism of toxicity is not understood at present. Life expectancy is generally not shortened by the disease, but OPMD does have a significant impact on quality of life (Becher et al., 2001). To preserve vision, surgical correction of ptosis is required for most individuals with OPMD. Dysphagia leads to prolonged meal times (Palmer, Neel, Sprouls, & Morrison, 2010), and proximal limb weakness can lead to decreased mobility. OPMD cases have been reported throughout the world, including exceptionally high populations of French Canadians in Quebec and Bukharan Jews in Israel. The current study focuses on a group of Hispanic northern New Mexicans with OPMD. More than 700 New Mexicans with OPMD have been identified by the OPMD Clinic at the University of

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University of New Mexico, Albuquerque Correspondence to Amy T. Neel: [email protected] Editor: Jody Kreiman Associate Editor: Julie Liss Received July 2, 2013 Revision received April 14, 2014 Accepted September 15, 2014 DOI: 10.1044/2014_JSLHR-S-13-0172

Disclosure: The authors have declared that no competing interests existed at the time of publication.

Journal of Speech, Language, and Hearing Research • Vol. 58 • 1–12 • February 2015 • Copyright © 2015 American Speech-Language-Hearing Association

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in five individuals with the disorder. Speech characteristics ranged from mild dysphonia and vocal fatigue to gross hypernasality and nearly unintelligible speech. They documented difficulties in all subsystems of speech, including reduced breath support, impairments of vocal intensity and fundamental frequency, hypernasality, decreased rate of speech, and articulation problems. Bouchard, Brais, Brunet, Gould, and Rouleau (1997) described a series of 72 French-Canadian individuals with OPMD. They observed “clinically detectable weakness” in 43% of cases, tongue weakness in 82%, and alteration of the voice (slurring, hoarseness, and weakness) in 67%. They also described the clinical progression of speech and voice symptoms in a single case study with “voice change” beginning at age 50 years, a weak and nasal voice and tongue weakness without atrophy at age 58 years, and by age 67 years, flattened facial expression with transversal smile, increased hoarseness of voice, nasality with no movement of the soft palate on phonation, and slurring. Tiomny and colleagues (1996) reported clinical symptoms for 13 Bukharan Jews with OPMD: Dysphonia ranged from mild in nine cases to severe in three cases. Other case reports in the literature have mentioned weakness of facial muscles (Boukriche, Maisonobe, & Masson, 2002), dysphonia and tongue weakness (Codère, Brais, Rouleau, & Lafontaine, 2001), weak movements of the soft palate (Bilgen, Bilgen, & Sener, 2001), and nasal voice (Adamczyk & Oshinskie, 1987; Chang et al., 1993). Weismer (2006) noted that there is little evidence for a strong relation between weakness and severity of speech impairment. Although OPMD is a rare disease, it is of interest to the field because it offers us the unique opportunity to study the impact of weakness alone on speech and swallowing. As a myopathic disorder, OPMD is characterized by loss of muscle cells and is rarely associated with neuropathy or cognitive deficits (Boukriche et al., 2002; Hardiman et al., 1993; Jones & Harper, 2010; Raz, Butler-Browne, van Engelen, & Brais, 2013). Although previous studies of OPMD have documented its debilitating effects on speech production, the only study that has attempted to relate speech deficits and muscle weakness was published by Neel, Palmer, Sprouls, and Morrison (2006), who reported measures of tongue strength and speech intelligibility in eight individuals with OPMD. These participants had greatly reduced maximum tongue strength compared to the controls, but estimates of tongue pressure produced during the syllable /dà / showed that most were able to generate similar pressures to normal controls. Listener ratings suggested that speech intelligibility was not impaired for most of the individuals with OPMD. The current study adds to that work by extending the investigation to all subsystems of speech (respiration, phonation, articulation, and resonance balance) for the eight participants in the 2006 study and four additional individuals with OPMD, thus providing a comprehensive profile of speech and voice characteristics associated with the disorder (Kent, Kent, Duffy, & Weismer, 1998; Kent & Kim, 2003). We measured the pressure exerted by the tongue in maximal pressure and a speechlike task to quantify one aspect of weakness in the speech mechanism and then assessed the relations between tongue pressure and various measures of speech production

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and intelligibility. If weakness underlies speech deficits in persons with OPMD who exhibit measurably reduced tongue strength, we should observe changes in acoustic measures of speech and voice production and in listener ratings of intelligibility, articulation, phonation, and resonance balance.

Method All procedures were approved by the Institutional Review Board at the University of New Mexico.

Participants Individuals with OPMD were recruited from the OPMD Clinic in the Department of Neurology at the University of New Mexico Health Sciences Center. As part of a larger investigation of speech and swallowing characteristics of the disorder, 12 individuals with OPMD and 12 controls of similar ages with no family history of OPMD participated in the study (see Table 1). All participants were Hispanic, primarily English-speaking individuals from New Mexico. The participants with OPMD had significant dysphagia and ptosis. Onset of symptoms preceded diagnosis by many months or years for most of the participants. All participants were paid for taking part in the study.

Procedures Respiration. Forced vital capacity (FVC) and forced expiratory volume in one second (FEV1) were obtained using a SpiroStar DX Spirometer with Spiro 2000 Version 1.6.1 software (Medikro Oy, Kuupio, Finland) attached to a Dell desktop computer. To obtain these measures, participants were instructed to take in as deep a breath as possible and then force out all the air through the spirometry tube with the nose clipped. The task was repeated three times, and the highest of the three values for FVC and FEV1 was submitted to analysis. For normative data, prediction equations for Hispanic adults reported by Coultas, Howard, Skipper, and Samet (1988) were used. Resonance balance. Nasometry was used to assess resonance balance. For control participants C1 and C2 and for participants with OPMD S1–S6, nasalance scores were obtained with the NasalView system (Tiger Electronics, Seattle, WA). For control participants C3–C12 and participants with OPMD S7–S12, we used the Kay Nasometer II, Model 6400 (KayPENTAX, Lincoln Park, NJ). Participants read aloud the Zoo Passage (Fletcher, 1978), which contains only oral phonemes. Phonation. Speech and voice tasks were recorded on a Marantz PMD670 solid state recorder with a Shure SM10A head-mounted microphone positioned about 1 cm from the corner of the mouth. Several measures of phonatory function were obtained. To determine maximum vowel duration for /A/, participants were instructed to take a deep breath and hold out “ah” as long as they could. The longest duration of three trials was submitted to analysis for each participant. Laryngeal diadochokinetic rates were obtained by

Journal of Speech, Language, and Hearing Research • Vol. 58 • 1–12 • February 2015

Table 1. Demographic data for control (C) participants and participants with oculopharyngeal muscular dystrophy (OPMD) (S).

Participant C1 C2 C3 C4 C5 C6 C7 C8 C9 C10 C11 C12 S1 S2 S3 S4 S5 S6 S7 S8 S9 S10 S11 S12

Age (years)

Gender

61 61 58 59 56 69 56 57 56 67 52 53 63 62 61 57 66 67 59 57 57 73 50 51

F F M F M F M F F F M F F F M F F F M F F F M F

Time since diagnosis

Hearing screening at 25 dB HL

Dysphagia treatment

3 years 4 years 10 years 4 months 10 years 6 months 4 years 2.5 years 6 months 10 years 1 year 6 years

Fail (4 kHz) Fail (4 kHz) Fail (4 kHz) Fail (500 Hz, 4 kHz) Pass Fail (2 kHz) Fail (4 kHz) Pass Fail (4 kHz) Fail (4 kHz) Fail (4 kHz) Pass Fail (4K Hz) Fail (4–8K Hz) Fail (2–8K Hz) Fail (all) Fail (2K–8K Hz) Fail (500–8K Hz) Fail (4–8K Hz) Pass Fail (4–8K Hz) Fail (250–1K Hz) Fail (all) Pass

Botox ×2 None None None Botox ×3 Esophageal dilatation ×1 Botox ×1 None None None None Esophageal dilatation ×10

Note. F = female; M = male.

having participants repeat the vowel /A/ as quickly as possible until asked to stop. The number of syllables per second was counted from the middle 5 seconds, and the fastest rate from two trials was submitted to analysis. To obtain maximum intensity of phonation, “hey” shouted at a self-selected pitch was measured with a sound level meter located 30 cm from the participant’s mouth. Habitual intensity was measured at five 20-second intervals during reading of the Rainbow Passage (Fairbanks, 1960). Mean fundamental frequency and F0 range were obtained from recordings of six sentences of eight to nine words in length (Weismer & Laures, 2002) read aloud by the participants. The average F0 value over the six sentences was submitted to analysis. F0 range was calculated for each sentence by subtracting the lowest value achieved during the utterance from the highest. The largest range from the six sentences was submitted to analysis. Three acoustic parameters from the Multi-Dimensional Voice Program (MDVP, Kay Pentax) were used to explore voice quality from the sustained /A/ vowels. As recommended by Kent, Vorperian, and Duffy (1999), 3-second intervals from the middle portion of the sustained vowels were submitted to MDVP analysis, usually from the second trial of the sustained vowel task. Selected measures represented fundamental frequency and amplitude parameters as well as ratios of harmonic and inharmonic energy in the spectrum. The parameters included relative average perturbation (RAP), shimmer in dB, and noise-to-harmonics ratio. To evaluate voice quality in connected speech, long-term average spectrum (LTAS) measures were obtained for one

sentence with unvoiced segments removed from each participant using the Kay Computerized Speech Lab, Model 4150 (CSL, KayPENTAX). Articulation. To assess the potential impact of OPMD on speed of articulator movements, diadochokinetic rates for the syllables /pÃ/, /tÃ/, /kÃ/, and /pÃtəkə/ were obtained. Participants were asked to repeat the syllables as rapidly as possible until asked to stop, and the number of syllables per second from middle 5 seconds was calculated. Articulation rate in syllables per second was obtained from the set of six sentences described above (Weismer & Laures, 2002). Pauses lasting longer than 50 ms that were not related to articulatory acts such as voice onset time were subtracted from the total speaking time for each sentence. The average articulation rate over the six sentences was submitted to analysis. Several segment durations were measured from the 25-word list (adapted from the paired word intelligibility test in Kent, Weismer, Kent, and Rosenbek, 1989) read aloud by participants. Voice onset times for the initial stop in the word “two,” were obtained in Praat (Boersma, 2001) by measuring the duration from the burst to the onset of vibration for the following vowel sound. Consonant closure durations were obtained for the voiceless final stop in “at” by measuring the interval from the offset of clear vowel formants to the following stop burst. Durations of the fricative in the word “sip” were also measured in Praat. As a measure of tongue placement accuracy, the first spectral moment was obtained for the initial /s/ in the words “sip,” “seep,” and “see.” Using CSL (KayPENTAX), the audio files for each word were filtered at 10000 Hz, and

Neel et al.: Muscle Weakness and Speech in OPMD

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spectral moments were obtained at the center of the fricatives using a 20 ms Hamming window (Tjaden & Turner, 1997). The first spectral moment (weighted average of the spectral peak frequencies) was averaged across the three words and submitted to analysis. If individuals with OPMD produce alveolar fricatives with shorter, wider constrictions or a more posterior place of articulation due to tongue weakness, first spectral moment values should be lower than that of controls (Tjaden & Turner, 1997). Three vowel-related measures were obtained from the words “heed,” “hod,” and “who’d” read in a sentence frame: F1 range, F2 range, and vowel space area. The first two vowel formants were obtained at the midpoint of each vowel using Praat. F1 range was calculated by subtracting the lowest F1 value of the three vowels from the highest F1 value. F2 range was calculated by subtracting the lowest F2 value from the highest. Euclidean distance between each pair of vowels was calculated, and the vowel space area for /i/, /A/, and /u/ was computed using Heron’s formula. Tongue pressure. Tongue-to-palate strength was measured during maximal isometric and speech tasks using the Iowa Oral Performance Instrument (IOPI; IOPI Northwest Co., Carnation, WA). The IOPI data were digitized at a sampling frequency of 1000 Hz and stored using the WINDAQ digital acquisition system (DATAQ Instruments, Akron, OH). To ensure consistent placement of the IOPI bulb, it was centered on the midpoint of the tongue body such that the end of the bulb did not extend past the mandibular teeth. For the maximal pressure task, participants were instructed to press the IOPI bulb as hard as possible with their tongues. The task was performed four times: twice at the beginning of the experimental session and twice at the end. The maximum value across the four trials was submitted to analysis. For the speech task, participants were asked to repeat the syllable /dà / at least four times with the IOPI bulb in place. The mean of the first four values was submitted to analysis. Quality of life. All participants completed a questionnaire regarding their communication skills patterned after the SWAL-QOL instrument (McHorney et al., 2000). Sections included burden, speaking, symptoms, communication, mental health, and socialization. Participants used a 5-point scale to judge how often each of 28 statements was true. A score of 5 was assigned to statements that participants judged to be not true at all, and a score of 1 was assigned to statements judged to be very much true. Participants in the control group were expected to have scores of 5 across the 28 statements. Intelligibility ratings. Two certified speech-language pathologists rated overall intelligibility and several speech parameters for three of the Weismer and Laures (2002) sentences produced by each participant. The sentences were delivered via Alvin experiment control software (Hillenbrand & Gayvert, 2005) on a desktop computer played through Sennheiser HD 580 headphones. Using a visual analog scale from 0 (normal or no impairment) to 100 (severe impairment), the speech-language pathologists rated overall intelligibility plus six speech parameters: stress, intonation, rate, articulatory

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precision, voice quality, and nasality. Listeners could replay the three sentences if they desired. Statistical analysis. Power analysis revealed that the sample size of 12 subjects in each group was more than adequate for determining significant differences on the maximum tongue pressure measure. Statistical differences between the two groups for all variables were tested using independent samples t tests. Instead of reducing the alpha level in the face of multiple comparisons, which decreases Type I errors but may increase Type II errors, we report effect size (Cohen’s d ) for each t test. To assess the impact of weakness on speech production, Pearson product-moment correlations between tongue pressure measures and selected acoustic and perceptual measures were performed for the OPMD group.

Results Reliability of Acoustic Measures Intrajudge and interjudge reliability estimates were obtained for acoustic measures of speech and voice. To obtain intrajudge reliability, the investigator re-measured 10% of the tokens. Pearson product-moment correlation coefficients were above .98 (p < .05) for the intrajudge comparisons. For interjudge reliability, a second investigator measured 10% of the tokens. Correlations of .95 and above ( p < .05) were obtained for all interjudge comparisons, indicating adequate reliability of acoustic measurements. All of the intrajudge and interjudge differences between acoustic measures fell below 5%.

Respiration Table 2 contains mean FVC and FEV1 values for each group along with standard deviations and ranges. T tests revealed that the OPMD group did not differ significantly from the control group for either measure, FVC, t = 0.42, p = .69; FEV1, t = 0.30, p = .77. Compared to Coultas et al. (1988) norms, three participants exhibited depressed performance: C12, S4 (who reported multiple health issues), and S13 (who reported having aspiration pneumonia three times). OPMD has been associated with significant loss of muscle cells in the diaphragm (Little & Perl, 1982), but the participants in this study generally did not appear to have respiratory deficits.

Resonance Balance Table 3 contains means, standard deviations, and ranges for nasalance scores for the NasalView and Kay Nasometer systems. Because of the differences in scores between the two nasometry systems, statistical comparison was not performed. Scores were compared to norms for the NasalView system (Awan, 2001; Bressman, 2005) and for the Nasometer system (Seaver, 1991). One of the controls (C6) and three of the participants with OPMD (S4, S6, and S11) had nasalance scores that were more than two standard deviations higher

Journal of Speech, Language, and Hearing Research • Vol. 58 • 1–12 • February 2015

Table 2. Means (standard deviations) and ranges for respiration measures. Control Respiration measure Forced vital capacity (mL) Forced expiratory volume in 1 sec (mL)

OPMD

M (SD)

Range

M(SD)

Range

3,107 (816) 2,615 (819)

2,250–4,360 1,750–4,140

2,946 (994) 2,500 (920)

1,950–3,920 960–4,140

than norms. Their scores, which fell between 30 and 33, indicated mild hypernasality.

Phonation Results for phonation measures are shown in Table 4. For maximum phonation duration, there were no significant differences between controls and individuals with OPMD, t = 0.41, p = .69. Five participants (C2, C7, C14, S4, and S6) had duration values that fell more than one standard deviation below the norms reported by Hakkesteegt, Brocaar, Wieringa, and Feenstra (2006). Comparison of laryngeal diadochokinetic rates revealed a significant difference between the control and OPMD groups, t = 3.22, p = .004. A Cohen’s d score of 1.31 indicated a large effect. The OPMD participants, mean = 3.6 syllables/ second, had slower repetition rates than controls, mean = 4.8 syllables/second. One participant with OPMD, S11, had rates more than two standard deviations slower than even elderly males (Ptacek, Sander, Maloney, & Jackson, 1966), despite being the youngest of all the subjects. There was no significant difference between the OPMD and control group in maximum intensity, t = 0.20, p = .84. When maximum intensity values were compared to those obtained by Ptacek et al. (1966) by having subjects produce /A/ as loudly as possible, several participants from both groups fell more than two standard deviations below means for elderly subjects (ages 66–93 years). Two controls, C6 and C8, and five from the OPMD group, S2, S3, S4, S7, and S9, produced maximum intensities of less than 90 dB SPL. Because habitual intensity values were available for only six controls and nine members of the OPMD group, statistical comparison was not performed. Habitual intensity values were compared to norms obtained by Gelfer and Young (1997) for two sentences from the Rainbow Passage for young adult males (mean intensity = 70.4 dB SPL) and females (68.2 dB SPL). One of the control subjects, C1, and six of the nine participants with OPMD (S2, S3, S4, S6, S7, and S8) had values that fell more than two standard deviations below the norms for their gender. It is not clear why participants in this study

had lower values than the Gelfer and Young norms; possibilities include task differences, increased age, or disease processes. The individuals with OPMD were able to substantially increase intensity over habitual values on request: On average, they shouted “hey” with 28 dB greater intensity than speech read at a comfortable level. For average F0 in sentences, there were no significant differences between the control and OPMD groups, t = 0.43, p = .67. Means for both groups appeared appropriate for their age and gender. No differences in F0 range in sentences read aloud were detected by t test, t = 0.17, p = .87. No significant differences in MDVP voice quality measures for sustained /a / between controls and individuals with OPMD were observed. Values obtained from the current study were compared with norms for young adults ages 20–55 years (Deliyski & Gress, 1998) and for older adults (Xue & Deliyski, 2001). Many participants in both groups had scores higher than two standard deviations above the mean for young adults for all three measures. For the elderly norms, C2 scored more than two standard deviations above the mean for RAP. Three individuals with OPMD had elevated scores compared to normal: S4 was higher for shimmer in dB, RAP, and noise-to-harmonics ratio, while S7 and S11 had high scores for RAP and noiseto-harmonic ratio. The first four spectral moments of the LTAS were obtained to assess voice quality in connected speech. Because the four measures were highly intercorrelated, only LTAS skewness scores were submitted to analysis. No significant difference between the groups was found, t = −1.15, p = .26, though skewness scores for the OPMD group were slightly higher than those for the healthy controls. Compared to the skewness values reported for healthy adults of between 5.00 and 7.00 (Lowell, Colton, Kelley, & Hahn, 2011; Tjaden, Sussman, Liu, & Wilding, 2010), six members of the control group and four members of the OPMD group had relatively high skewness scores indicating weakness in the upper harmonics of the speech spectrum. In summary, the reduced laryngeal diadochokinetic rate for speakers with OPMD compared to healthy controls

Table 3. Means (standard deviations) and ranges for nasalance scores with results for the NasalView and Nasometer systems reported separately. Control System NasalView (C1–C2, S1–S6) Kay Nasometer (C3–C12, S7–S12)

OPMD

M (SD)

Range

M (SD)

Range

25.91 (0.21) 16.9 (9.3)

25.76–26.06 7–33

26.26 (5.90) 19.2 (7.4)

16.38–31.94 11–32

Neel et al.: Muscle Weakness and Speech in OPMD

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Table 4. Means (standard deviations) and ranges for phonatory measures. Control Phonatory measure Sustained /a / duration (s) Laryngeal DDK rates (syls/s)* Maximum intensity (dB SPL) Habitual intensity (dB SPL) Average F0 (Hz) F0 range (Hz) MDVP: Shimmer dB MDVP: Relative average pertubation MDVP: Noise-to-harmonics ratio LTAS skewness

OPMD

M (SD)

Range

M (SD)

Range

18.9 (9.9) 4.5 (0.7) 88.2 (11.9) 63.7 (4.31) 170.8 (35.2) 101.3 (33.2) 0.46 (0.28) 0.99 (1.12) 0.15 (0.06) 8.50 (3.35)

6.8–41.2 2.6–5.6 70–105 55.2–67.6 110.3–214.7 48–176 0.17–1.032 0.18–3.86 0.03–0.26 4.5–12.7

17.5 (6.6) 3.3 (1.2) 87.3 (8.1) 59.6 (3.2) 164.2 (40.5) 98.7 (40.4) 0.16 (0.31) 1.01 (2.49) 0.37 (0.54) 9.91 (2.64)

9.2–29.6 2.2–4.4 71–99 55.4–64.2 103.5–219.7 45–199 0.20–1.37 0.20–8.10 0.11–2.03 5.4–14.2

Note. DDK = diadochokinetic; MDVP = multi-dimensional voice program; LTAS = long-term average spectrum. *Significant difference.

was the only significant voice-related difference found in this analysis. Otherwise, the individuals with OPMD did not differ from the healthy controls on average, and both groups resembled older speakers in other studies.

Articulation Articulatory results are shown in Table 5. Participants with OPMD performed significantly more slowly on diadochokinetic rate tasks than controls for /pà /, t = 2.61, p = .02, Cohen’s d = 1.13; /tà /, t = 2.45, p = .02, Cohen’s d = 1.05; and /kà /, t = 3.17, p = .01, Cohen’s d = 1.36. Effect sizes for all three tasks were large. However, rates for the combined syllable task /pÃtəkə/ were not significantly slower, t = 0.90, p = .38. Average rates for the OPMD group were about 5%– 10% slower than the rates for the controls. Single-syllable diadochokinetic rates for both groups in the current study fell closer to the values reported for elderly speakers (over 65 years) by Ptacek et al. (1966) than for younger adults (under 40 years). Repetition rates for the speakers with OPMD in this study were generally faster than those reported for individuals with spastic and ataxic dysarthria by Portnoy and Aronson (1982). The two groups did not differ in the rate of syllables per second produced in short sentences read aloud, t = 0.627, p = .54, nor in average pause time per sentence, t = 0.48, p = .83. Both groups produced a little over three syllables per second, and few pauses were observed in these relatively short sentences. Regarding segment durations, no significant group differences were found. Although the OPMD group on average produced longer voice onset times for voiceless stops and initial fricatives, the differences did not reach statistical significance. Comparison of the first spectral moments for /s/ revealed no difference between the participants with OPMD and controls, t = −0.67, p = .51. First spectral moment values for the individuals with OPMD (mean = 7269 Hz) were slightly higher than those of healthy controls (mean = 6962 Hz) but fell within the range of values for normal speakers reported by Tjaden and Turner (1997).

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Analysis of F1 and F2 range and vowel space area also revealed no significant differences between the two groups, F1 range, t = −0.023, p = .98; F2 range, t = 0.548, p = .22; vowel space area, t = 0.67, p = .51. As with the voice analysis, the only significant difference between the groups was the reduction in diadochokinetic rates for single syllable repetitions for the individuals with OPMD.

Tongue Pressure Mean tongue pressure data for the two groups are shown in Table 6, and individual data are shown in Figure 1. Maximum tongue pressure values were significantly lower for the individuals with OPMD compared to the controls, t = 9.85, p = .00, Cohen’s d = 4.03. On average, the individuals with OPMD had less than one-half of the maximum tongue pressure of the controls, OPMD mean = 25 kPa, control mean = 59 kPa. The mean maximum tongue pressure for the control group in this study was slightly lower than those reported for older adults by Neel and Palmer (2012), perhaps because some participants in that study were 40–50 years of age rather than over 50 years. Pressures generated during the production of the syllable /dà / did not differ significantly between the two groups, t = 1.74, p = .10. Both participant groups produced tongue pressures below 20 kPa while producing the syllable /dà /, which falls close to the 10–14 kPa range reported by Neel and Palmer for adult subjects. Healthy controls used about 20%–25% of their maximum pressure to produce the /dà / syllable, whereas individuals with OPMD on average used around 40% of their maximum pressure to produce /dà /.

Quality of Life Average rankings for each statement of the qualityof-life questionnaire for the OPMD and control groups are shown in Table 7. As expected, the control participants responded with scores of 5 or not true at all to nearly every statement on the questionnaire: Speech skills were not impaired and presented no barrier to communication, mental

Journal of Speech, Language, and Hearing Research • Vol. 58 • 1–12 • February 2015

Table 5. Means (standard deviations) and ranges for articulatory measures. Control Articulatory measure DDK rate: /pà / (syls/s)* DDK rate: /tà / (syls/s)* DDK rate: /kà / (syls/s)* DDK rate: /pÃtəkə/ (syls/s) Articulation rate (phonemes/s) Pause duration (s) Voice onset time for /t / (ms) Consonant closure duration for /t / m(s) Fricative duration for /s/ (ms) First spectral moment for /s/ (Hz) Vowel F1 range (Hz) Vowel F2 range (Hz) Vowel space area (Hz2)

OPMD

M (SD)

Range

M (SD)

Range

5.9 (0.5) 5.7 (0.5) 5.3 (0.5) 6.2 (0.6) 3.2 (0.5) 0.142 (.247) 98.5 (15.0) 153.1 (28.2) 251.5 (43.5) 6,962.6 (1,282.6) 448.9 (83.9) 1552.8 (197.8) 334262 (98,557)

4.4–6.9 3.8–6.6 3.5–5.8 5.2–7.2 2.1–4.0 0–0.751 79–123 110–194 187–335 4,700–8,756 286–532 1309–1899 192980–526903

5.3 (0.6) 5.1 (0.6) 4.7 (0.5) 5.9 (0.9) 3.1 (0.4) 0.160 (0.166) 104.3 (26.8) 141.0 (42.4) 270.3 (118.8) 7,269.3 (892.5) 449.7 (76.9) 1452.3 (192.5) 309632 (80488)

3.8–6.4 3.6–5.8 3.8–5.4 4.2–7.4 2.4–3.7 0–0.511 58–148 74–202 229–463 5,813–8,268 365–565 995–1648 178550–440291

*Significant difference.

health, or socialization. Six of the individuals with OPMD, however, had mean scores of less than 4 out of 5 on the questionnaire, suggesting some quality-of-life issues related to speech difficulties (S1, S4, S5, S7, S9, and S13). The lowest scores on the questionnaire from the OPMD group occurred for the following items: “dealing with my speech problem is very difficult,” “my voice is too weak or quiet,” “strangers have a hard time understanding my speech,” and “I often have to repeat what I say.” At least half of the participants with OPMD marked each of those statements as somewhat true to very much true.

Intelligibility Ratings Intelligibility and speech parameter ratings were averaged across the two listeners. Scores for overall intelligibility and the six speech dimensions were submitted to a multiple analysis of variance (MANOVA) with the independent variable of group (control vs. OPMD) and the dependent variables of parameter (overall intelligibility, stress, intonation, rate, articulatory precision, voice quality, and nasality). The MANOVA revealed no effect of group on the dependent variables considered as a group, F(7, 16) = 1.04, p = .43. Follow-up ANOVAs for the dependent factors individually also revealed no significant differences between the groups with F values ranging from 3.07 for intelligibility, p = .10, to 0.01 for voice quality, p = .94. Figure 2 displays the average parameter ratings for the control and OPMD

groups. Compared to the control group, the OPMD group scored 3–5 points higher in impairment on overall intelligibility, stress, intonation, and rate. Mean scores for both groups suggested no impairment of speech intelligibility (control mean = 4.4 out of 100, OPMD mean = 8.3) and very mild impairment on average for voice quality (control mean = 12.2, OPMD mean = 12.0 out of 100).

Relation Between Tongue Pressure and Speech Measures To test the hypothesis that degree of weakness is correlated with increased deficits in acoustic and perceptual measures of speech and voice, Pearson product-moment correlations of maximum tongue pressure and /dà / pressure with several of the speech measures were computed for the OPMD group only. Neither maximum tongue pressure nor tongue pressure for /dà / were significantly correlated with any of the speech measures.

Discussion Individuals with OPMD in this study had reduced maximum tongue pressures compared to their age-matched controls. On average, participants with OPMD exhibited less than one-half the tongue strength of the control group. The ranges of maximum tongue pressure for the two groups did not overlap: The highest values for the OPMD

Table 6. Means (standard deviations) and ranges for tongue pressure measures. Control

Maximum tongue pressure (kPa)* Tongue pressure for /dÃ/ (kPa)

OPMD

M (SD)

Range

M (SD)

Range

59.3 (9.04) 17.2 (12.9)

48–69 3.8–40.6

24.7 (8.16) 9.9 (5.2)

11–37 2.8–20.7

*Significant difference.

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Figure 1. Mean maximum tongue pressure and tongue pressure exerted during /dà / for the individual control and OPMD participants.

group fell below the lowest values for the control group. Despite this substantial difference in strength of the tongue (and presumably other muscles of the speech mechanism), little impact on speech and voice measures or on perceptual ratings by listeners was observed. Slower single-syllable repetition was the only consistent difference between the individuals with OPMD and the healthy control group. This group of 12 people with OPMD may represent a relatively mild form of the disorder: We have certainly observed individuals with OPMD outside of this study with obvious speech impairments including articulatory imprecision, dysphonia, and hypernasality, and speech deficits have been reported many times in the literature on OPMD. At present, we know little about strength changes in structures other than the tongue and how weakness in the lips, pharynx, soft palate, vocal folds, and respiratory muscles affects speech production. Longitudinal research to determine the progression of weakness in these individuals over the course of time and the impact on speech and swallowing is currently under way in our laboratory, and endoscopic evaluations of velopharyngeal and vocal fold function are also being

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performed. Imaging studies will be helpful in relating amount of muscle cell loss to measures of strength, speech production, and speech intelligibility. Regarding therapy for individuals with OPMD who do present with speech deficits due to flaccid dysarthria, there is little information available to guide clinicians. Many individuals with OPMD are more concerned with swallowing difficulties than speech impairment. The 12 individuals in this study were no exception: They reported less impact on quality of life for speech issues than for swallowing problems (Palmer et al., 2010). Prosthetic treatments may be effective in treating some aspects of speech deficits in OPMD. If weakness of the velum causes substantial hypernasality, a palatal lift prosthesis may be considered in order to improve velopharyngeal closure. For decreased vocal volume, voice amplifiers may be used to increase loudness without creating fatigue. In addition, behavioral therapies such as Lee Silverman voice treatment (Ramig, Sapir, Fox, & Countryman, 2001) and clear speech (Lam & Tjaden, 2012) could be useful in improving speech intelligibility in individuals who exhibit voice and articulation deficits. Increasing strength through

Journal of Speech, Language, and Hearing Research • Vol. 58 • 1–12 • February 2015

Table 7. Mean scores for speech quality-of-life questionnaire. Questionnaire Burden Dealing with my speech problem is very difficult. My speech problem is a major distraction in my life. Mean Speaking Most days, I don’t care if I speak or not. I don’t enjoy speaking anymore. Mean Symptoms My voice is too weak or quiet. My voice is hoarse or rough. Too much air comes through my nose when I speak. It’s hard for me to pronounce sounds clearly. I run out of air when I speak. I have to pause more often when saying a sentence. My lips or tongue feel weak. My lips or tongue feel numb. I use a great deal of effort to speak. Mean Communication People I know well have trouble understanding my speech. Strangers have a hard time understanding my speech. People have trouble understanding me over the phone. It’s been difficult for me to speak clearly. I often have to repeat what I say. Mean Mental Health My speech problem depresses me. Having to be so careful to pronounce speech annoys me. I’ve been discouraged about my speech problem. My speech problem frustrates me. I get impatient dealing with my speech problem. Mean Social My speech problem makes it hard to have a social life. My work/leisure activities have changed due to my speech problem. Social gatherings are not enjoyable due to my speech problem. I avoid talking on the phone because of my speech problem. Role with family/friends has changed because of my speech problem. Mean Overall Mean (standard deviation) Range

progressive resistance exercises seems to be an obvious treatment target in OPMD to improve both speech and swallowing abilities. However, the intensity and amount of exercise required to achieve overload levels to bring about strength changes (Robbins, 2011) may not be prudent in a disorder associated with muscle degeneration and impaired regeneration of muscle fibers (Gidaro et al., 2013). Further research is needed to determine if muscle strength can be safely and effectively improved in OPMD. If moderate myopathic weakness has relatively little impact on production of intelligible speech, how do we account for the speech deficits often associated with neuromuscular disorders? One possibility is greater loss of strength: Individuals must be so weak that the tongue cannot be raised to the alveolar ridge, the vocal folds cannot contact one another, or the velum cannot reach the back wall of the pharynx at a sufficient speed to support normal speech production. A recent report by Solomon, Makashay, Helou, and Clark

Controls

OPMD

5 5 5

3.2 3.3 3.2

5 5 5

4.3 4.3 4.3

4.8 4.7 4.9 4.7 4.8 4.9 5 5 5 4.9

3.2 4.1 4.4 3.7 3.9 3.3 3.7 4.3 3.5 3.8

5 5 4.9 4.8 4.8 4.9

3.3 3.2 3.3 3.4 3.0 3.2

5 4.9 5 5 5 5

3.8 3.5 4.1 3.8 3.9 3.8

5 5 5 5 5 5

4.3 4.1 4.6 4.3 4.3 4.3

4.97 (0.04) 4.88–5.00

3.76 (1.06) 2.05–5.00

(2011) explored orofacial weakness, speech intelligibility, perceived severity of dysarthria, and speech rate in monologue and diadochokinetic rate tasks for a heterogeneous group of adults with dysarthria. They found weak to moderate correlations between tongue strength and speech function and suggested that maximum anterior tongue pressure values of 18 to 28 kPa may be associated with noticeable impairments of speech. They further noted that neither reduced diadochokinetic rates nor slow speech rates in a monologue were correlated with tongue strength. In the current study, the participants with OPMD had mean maximum pressure values around 25 kPa, less than half of the average value for healthy controls. Further studies of OPMD in our laboratory will include individuals with greater speech deficits in order to determine the threshold at which weakness in the speech mechanism impacts speech production. A number of studies have investigated tongue strength and speech intelligibility in other disorders associated with

Neel et al.: Muscle Weakness and Speech in OPMD

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Figure 2. Mean intelligibility and speech parameter ratings for the control and OPMD participants. Error bars show standard errors.

dysarthria, including Parkinson’s disease, amyotrophic lateral sclerosis, multiple sclerosis, and traumatic brain injury. For Parkinson’s disease, researchers found no significant decrease in maximum tongue pressure compared to age-matched controls and no relation between measures of tongue function and measures of speech adequacy (McAuliffe, Ward, Murdoch, & Farrell, 2005; Solomon, Robin, & Luschei, 2000). Individuals with multiple sclerosis were found to have significantly weaker tongues on average than controls and slower repeated movements of the tongue, but tongue strength and rate of movement were not significantly correlated with speech intelligibility (Murdoch, Spencer, Theodoros, & Thompson, 1998). Weakness appeared to be relatively mild in these individuals with multiple sclerosis; on average they had 70%– 84% of the tongue strength of the normal control group. For individuals with dysarthria related to traumatic brain injury, one study found that participants had mildly reduced strength compared to a control group (Theodoros, Murdoch, & Stokes, 1995), whereas two other studies did not (Goozee, Murdoch, & Theodoros, 2001; McHenry, Minton, Wilson, & Post, 1994). Goozee et al. (2001) reported weak correlations between measures of tongue function and deviant articulation, whereas McHenry et al. (1994) found that the group judged to be less intelligible did not differ in strength from the group judged to be more intelligible. For amyotrophic lateral sclerosis, two studies demonstrated significant tongue weakness compared to controls and significant negative correlations between tongue strength and speech intelligibility (Dworkin, Aronson, & Mulder, 1980; Langmore

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& Lehman, 1994). The individuals with amyotrophic lateral sclerosis had weaker tongues on average than those with other neurologic disorders. The disadvantage in using neurologic disorders to study the impact of weakness on speech production is that aspects of neuromuscular function other than weakness may account for the dysarthric speech deficits. Future research into neuromuscular deficits underlying dysarthria should focus on those aspects. For example, we have little information of the impact of abnormal muscle tone (such as spasticity associated with upper motor neuron damage or rigidity associated with basal ganglia dysfunction), poor coordination of range, force, and timing related to cerebellar damage, or diminution of reflexes and sensory deficits associated with lower motor neuron damage, though abnormal muscle tone is currently being investigated (Dietsch et al., 2014; Solomon & Clark, 2010). Ascertaining the underlying neuromuscular problems that cause dysarthria has important implications for treatment. It is clear we have more to learn about the relation between weakness and speech deficits. In OPMD, it is possible to examine the relations among amount of muscle cell loss in an organ (via imaging studies), weakness (tongue and lip pressure measures), physiologic measures of speech production (e.g., speed, extent, and accuracy of movements), acoustic measures of articulation, voice, and resonance balance, speaker perceptions of the impact of their disorder on communication, and listener judgments of intelligibility and speech production. Relating physiology, acoustics, and

Journal of Speech, Language, and Hearing Research • Vol. 58 • 1–12 • February 2015

speaker and listener perceptions in OPMD, a disorder characterized by myopathic weakness without neurologic deficits, will advance our understanding of the link between weakness and speech production and help us determine appropriate treatments for dysarthria.

Acknowledgments We are very grateful to the individuals with OPMD and to the healthy controls who participated in this study. We also acknowledge the contributions of Aaron Padilla and Diondra Maestas in collecting and analyzing data.

References Adamczyk, D. T., & Oshinskie, L. (1987). Oculopharyngeal muscular dystrophy. Journal of the American Optometric Association, 58, 408–412. Awan, S. (2001). Age and gender effects on measures of RMS nasalance. Clinical Linguistics & Phonetics, 15, 117–121. Becher, M. W., Morrison, L., Davis, L. E., Maki, W. C., King, M. K., Bicknell, J. M., . . . Bear, D. G. (2001). Oculopharyngeal muscular dystrophy in Hispanic New Mexicans. Journal of the American Medical Association, 286, 2437–2440. Bilgen, C., Bilgen, I. G., & Sener, R. N. (2001). Oculopharyngeal muscular dystrophy: Clinical and CT findings. Computerized Medical Imaging and Graphics, 25, 527–529. Boersma, P. (2001). Praat, a system for doing phonetics by computer. Glot International, 5, 341–345. Bouchard, J. P., Brais, B., Brunet, D., Gould, P. V., & Rouleau, G. A. (1997). Recent studies on oculopharyngeal muscular dystrophy in Québec. Neuromuscular Disorders, 7(Suppl. 1), 22–29. Boukriche, Y., Maisonobe, T., & Masson, C. (2002). Neurogenic involvement in a case of oculopharyngeal muscular dystrophy. Muscle & Nerve, 25, 98–101. Brais, B., Rouleau, G. A., Bouchard, J. P., Fardeau, M., & Tome, F. M. (1999). Oculopharyngeal muscular dystrophy. Seminars in Neurology, 19, 59–66. Bressmann, T. (2005). Comparison of nasalance scores with the Nasometer, the NasalView, and the OroNasal System. Cleft Palate-Craniofacial Journal, 42, 423–433. Chang, M. H., Chang, S. P., Cheung, S. C., & Kong, K. W. (1993). Computerized tomography of oropharynx is useful in diagnosis of oculopharyngeal muscular dystrophy. Muscle & Nerve, 16, 325–328. Codère, F., Brais, B., Rouleau, G., & Lafontaine, E. (2001). Oculopharyngeal muscular dystrophy: What’s new? Orbit, 20, 259–266. Coultas, D. B., Howard, C. A., Skipper, B. J., & Samet, J. M. (1988). Spirometric prediction equations for Hispanic children and adults in New Mexico. American Review of Respiratory Disease, 138, 1386–1392. Deliyski, D., & Gress, C. (1998, November). Intersystem reliability of MDVP for Windows 95/98 and DOS. Paper presented at the Annual Convention of the American Speech-LanguageHearing Association, San Antonio, TX. Dietsch, A. M., Solomon, N. P., Sharkey, L., Duffy, J. R., Strand, E. A., & Clark, H. M. (2014). Perceptual and instrumental assessments of orofacial muscle tone in dysarthric and normal speakers. Journal of Rehabilitation Research and Development, 51, 1127–1142. Duranceau, A. C., Beauchamp, G., Jamieson, G. G., & Barbeau, A. (1983). Oropharyngeal dysphagia and oculopharyngeal muscular dystrophy. Surgical Clinics of North America, 63, 825–832.

Duranceau, C. A., Letendre, J., Clermont, R. J., Lévesque, H. P., & Barbeau, A. (1978). Oropharyngeal dysphagia in patients with oculopharyngeal muscular dystrophy. Canadian Journal of Surgery, 21, 326–329. Dworkin, J. P., Aronson, A. E., & Mulder, D. W. (1980). Tongue force in normals and in dysarthric patients with amyotropic lateral sclerosis. Journal of Speech and Hearing Research, 23, 828–837. Fairbanks, G. (1960). Voice and articulation drillbook (2nd ed.). New York, NY: Harper and Row. Fletcher, S. G. (1978). Diagnosing speech disorders from cleft palate. New York, NY: Grune and Stratton. Gelfer, M. P., & Young, S. R. (1997). Comparisons of intensity measures and their stability in male and female speakers. Journal of Voice, 11, 178–186. Gidaro, T., Negroni, E., Perie, S., Mirabella, M., Laine, J., St Guily, J., . . . Capucine, T. (2013). Atrophy, fibrosis, and increased PAX7-positive cells in pharyngeal muscles of oculopharyngeal muscular dystrophy patients. Journal of Neuropathology & Experimental Neurology, 72, 234–243. Goozee, J. V., Murdoch, B. E., & Theodoros, D. G. (2001). Physiological assessment of tongue function in dysarthria following traumatic brain injury. Logopedics Phoniatrics Vocology, 26, 51–65. Hakkesteegt, M. M., Brocaar, M. P., Wieringa, M. H., & Feenstra, L. (2006). Influence of age and gender on the dysphonia severity index. Folia Phoniatrica et Logopaedica, 58, 264–273. Hardiman, O., Halperin, J. J., Farrell, M. A., Shapiro, B. E., Wray, S. H., & Brown, R. H., Jr. (1993). Neuropathic findings in oculopharyngeal muscular dystrophy: A report of seven cases and a review of the literature. Archives of Neurology, 50, 481–488. Hillenbrand, J., & Gayvert, R. (2005). Open source software for experiment design and control. Journal of Speech, Language, and Hearing Research, 48, 45–60. Jones, L. K., & Harper, C. M. (2010). Clinical and electrophysiologic features of oculopharyngeal muscular dystrophy: Lack of evidence for an associated peripheral neuropathy. Clinical Neurophysiology, 121, 870–873. Kent, R. D., Kent, J. F., Duffy, J., & Weismer, G. (1998). The dysarthrias: Speech-voice profiles, related dysfunctions, and neuropathology. Journal of Medical Speech-Language Pathology, 6, 165–211. Kent, R. D., & Kim, Y.-J. (2003). Towards an acoustic typology of motor speech disorders. Clinical Linguistics and Phonetics, 17, 427–445. Kent, R. D., Vorperian, H. K., & Duffy, J. R. (1999). Reliability of the Multidimensional Voice Program™ for the analysis of voice samples of subjects with dysarthria. American Journal of Speech-Language Pathology, 8, 129–136. Kent, R., Weismer, G., Kent, J., & Rosenbek, J. (1989). Toward phonetic intelligibility testing in dysarthria. Journal of Speech and Hearing Disorders, 54, 482–499. King, M. K., Lee, R. R., & Davis, L. E. (2005). Magnetic resonance imaging and computed tomography of skeletal muscles in oculopharyngeal muscular dystrophy. Journal of Clinical Neuromuscular Disease, 6, 103–108. Lam, J., & Tjaden, K. (2012). Intelligibility of clear speech: Effect of instruction. Journal of Speech, Language, and Hearing Research, 56, 1429–1440. Langmore, S. E., & Lehman, M. E. (1994). Physiologic deficits in the orofacial system underlying dysarthria in amyotrophic lateral sclerosis. Journal of Speech, Language, and Hearing Research, 37, 28–37. Little, B. W., & Perl, D. P. (1982). Oculopharyngeal muscular dystrophy: An autopsied case from the French-Canadian kindred. Journal of the Neurological Sciences, 53, 145–158.

Neel et al.: Muscle Weakness and Speech in OPMD

11

Lowell, S. Y., Colton, R. H., Kelley, R. T., & Hahn, Y. C. (2011). Spectral- and cepstral-based measures during continuous speech: Capacity to distinguish dysphonia and consistency within a speaker. Journal of Voice, 25, e223–e232. McAuliffe, M. J., Ward, E. C., Murdoch, B. E., & Farrell, A. M. (2005). A nonspeech investigation of tongue function in Parkinson’s disease. Journals of Gerontology: Series A: Biological Sciences and Medical Sciences, 60, 667–674. McHenry, M. A., Minton, J. T., Wilson, R. L., & Post, Y. V. (1994). Intelligibility and nonspeech orofacial strength and force control following traumatic brain injury. Journal of Speech, Language, and Hearing Research, 37, 1271–1283. McHorney, C. A., Bricker, D. E., Robbins, J., Kramer, A. E., Rosenbek, J. C., & Chignell, K. A. (2000). The SWAL-QOL outcomes tool for oropharyngeal dysphagia in adults: II. Item reduction and preliminary scaling. Dysphagia, 15, 122–133. Murdoch, B. E., Spencer, T. J., Theodoros, D. G., & Thompson, E. C. (1998). Lip and tongue function in multiple sclerosis: A physiological analysis. Motor Control, 2, 148–160. Neel, A. T., & Palmer, P. M. (2012). Is tongue strength an important influence on articulation rates in diadochokinetic and reading tasks? Journal of Speech, Language, and Hearing Research, 55, 235–246. Neel, A. T., Palmer, P. M., Sprouls, G., & Morrison, L. (2006). Tongue strength and speech intelligibility in oculopharyngeal muscular dystrophy. Journal of Medical Speech-Language Pathology, 14, 273–277. Palmer, P. M., Neel, A. T., Sprouls, G., & Morrison, L. (2010). Swallow characteristics in patients with oculopharyngeal muscular dystrophy. Journal of Speech, Language, and Hearing Research, 53, 1567–1578. Portnoy, R. A., & Aronson, A. E. (1982). Diadochokinetic syllable rate and regularity in normal and in spastic and ataxic dysarthric subjects. Journal of Speech and Hearing Disorders, 47, 324–328. Ptacek, P. H., Sander, E. K., Maloney, W. H., & Jackson, C. C. R. (1966). Phonatory and related changes with advanced age. Journal of Speech, Language, and Hearing Research, 9, 353–360. Ramig, L. O., Sapir, S., Fox, C., & Countryman, S. (2001). Changes in vocal loudness following intensive voice treatment (LSVTW) in individuals with Parkinson’s disease: A comparison with untreated patients and normal age-matched controls. Movement Disorders, 16, 79–83. Raz, V., Butler-Browne, G., van Engelen, B., & Brais, B. (2013). 191st ENMC International Workshop: Recent advances in oculopharyngeal muscular dystrophy research: From bench to

12

bedside, 8–10 June 2012, Naarden, the Netherlands. Neuromuscular Disorders, 23, 516–523. Robbins, J. (2011). Upper aerodigestive tract neurofunctional mechanisms: Lifelong evolution and exercise. Head & Neck, 33(Suppl. 1), S30–S36. Seaver, E. J. (1991). A study of nasometric values for normal nasal resonance. Journal of Speech, Language, and Hearing Research, 34, 715–721. Solomon, N. P., & Clark, H. M. (2010). Quantifying orofacial muscle stiffness using damped oscillation. Journal of Medical Speech-Language Pathology, 18, 120–124. Solomon, N. P., Makashay, M. J., Helou, L. B., & Clark, H. M. (2011, November). Temporal and perceptual characteristics of speech in neurogenic orofacial weakness. Paper presented at Annual Convention of the American Speech-Language-Hearing Association, San Diego, CA. Solomon, N. P., Robin, D. A., & Luschei, E. S. (2000). Strength, endurance, and stability of the tongue and hand in Parkinson disease. Journal of Speech, Language, and Hearing Research, 43, 256–267. Theodoros, D. G., Murdoch, B. E., & Stokes, P. (1995). A physiological analysis of articulatory dysfunction in dysarthric speakers following severe closed-head injury. Brain Injury, 9, 237–254. Tiomny, E., Khilkevic, O., Korczyn, A. D., Kimmel, R., Hallak, A., Baron, J., & Gilat, T. (1996). Esophageal smooth muscle dysfunction in oculopharyngeal muscular dystrophy. Digestive Diseases and Sciences, 41, 1350–1354. Tjaden, K., Sussman, J. E., Liu, G., & Wilding, G. (2010). Longterm average spectral (LTAS) measures of dysarthria and their relationship to perceived severity. Journal of Medical SpeechLanguage Pathology, 18, 125–132. Tjaden, K., & Turner, G. S. (1997). Spectral properties of fricatives in amyotrophic lateral sclerosis. Journal of Speech, Language, and Hearing Research, 40, 1358–1372. Weismer, G. (2006). Philosophy of research in motor speech disorders. Clinical Linguistics and Phonetics, 20, 315–349. Weismer, G., & Laures, J. (2002). Direct magnitude estimates of speech intelligibility in dysarthria: Effects of a chosen standard. Journal of Speech, Language, and Hearing Research, 45, 421–433. Young, E. C., & Durant-Jones, L. (1997). Gradual onset of dysphagia: A study of patients with oculopharyngeal muscular dystrophy. Dysphagia, 12, 196–201. Xue, S. A., & Deliyski, D. (2001). Effects of aging on selected acoustic voice parameters: Preliminary normative data and educational implications. Educational Gerontology, 27, 159–168.

Journal of Speech, Language, and Hearing Research • Vol. 58 • 1–12 • February 2015

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