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Article Excerpt
The study investigated whether acoustic speech measures permitted effective clinical assessment of the effects of botulinum toxin treatment (BT) in an individual with adductor spasmodic dysphonia (ADSD). A 54-year-old male diagnosed with ADSD was tracked over a span of 26 months of BT treatment. Seven BT injections were administered during that time span. A total of 24 audio recordings of the participant reading the "Rainbow Passage" (Fairbanks, 1960) aloud were made pre- and postinjections. Short-term and long-term effects of treatment were evaluated using temporal acoustic measurements. Anticipated voice improvement was observed following treatment, and there were statistically significant differences, in the immediate pre- versus postinjection readings for total pause time and total articulation time. Statistically significant improvement over the long term was found for total speaking time, total pause time, and words per minute, but not in total articulation time. Linear regression analysis showed a statistically significant relationship between duration of BT therapy and magnitude of clinical change across the 24 readings. That is, as time in treatment increased, postinjection rate of speech also increased. In addition to expected short-term improvements, there was also cumulative long-term improvement in response to BT injections. Temporal acoustic analyses of connected speech proved useful for quantifying short- and long-term treatment-related change.
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The parameters of speech stability in individuals with adductor spasmodic dysphonia (ADSD) treated with botulinum toxin (BT) are poorly understood, controversial, and involve issues of theoretical and clinical concern. The immediate effects of BT injection of the vocal fold(s) on voice production are increased breathiness and reported tightness in the vocal track, which resolves approximately 1 month postinjection. This is usually followed by a couple of months of improved voice quality, which deteriorates at approximately 3 to 4 months and is then followed by another injection. BT treatment raises the following issues: what measures should be used to successfully monitor improvement in functional communication and assess the long-term parameters of both voice and speech? (1)
PARAMETERS OF TREATMENT
Short-Term Impact
Short-term efficacy of the BT technique, that is, voice improvement following initial injection is well established in the literature (Boutsen, Cannito, Taylor, & Bender, 2002; Truong, Rontal, Rolnick, Aronson, & Mistua, 1991). Nevertheless, in studies comparing the postinjection ADSD voices to voices of normal controls, ADSD voice remains significantly poorer than normal as measured by both perceptual and acoustic techniques (Cannito, Woodson, Murry, & Bender, 2004; Langveld, van Rossum, Houtman, Zwinderman, Briaire, & Baatenburg De Jong, 2001; Sapienza, Cannito, Murry, Branski, & Woodson, 2002). ADSD voice may continue to improve across repeated injections, primarily as a function of dosage adjustments (Blitzer, Brin, & Stewart, 1998; Cannito & Woodson, 2000). It is also possible that postinjection benefit may decline across repeated injections.
Long-Term Impact
Long-term impact of BT treatment appears to vary depending upon the type of measurements used to evaluate it. Available data on this topic are limited, and study findings appear equivocal depending upon the type of measurements used to evaluate it. For example, Aronson, McCaffrey, Litchy, and Lipton (1993) studied 10 ADSD speakers using patient self-ratings to assess vocal change. They found that the amount of improvement following injection was relatively stable, and the time from injection to beginning of voice deterioration became progressively longer across the three injections. Hogikian, Wodchis, Spak, and Kileny (2001) followed 27 ADSD patients across three injections using a functional scale of voice-related quality of life measured during the period of maximum benefit, which ranged from 6 to 8 weeks postinjection. Although quality of life improved over preinjection levels following each injection, their data also demonstrated a statistically significant decline in patients' judgments of postinjection vocal quality of life across the three injections. While the authors speculate that the patients' internal standards may have shifted as they became more accustomed to their post-BT voice, it is also plausible that the amount of benefit may have actually declined.
In contrast, Mehta, Goldman, and Orloff (2001) reported sustained gradual improvement across three injections that occurred 12 months or more apart for each of 16 patients with ADSD. Intervening injections during this period were not studied. They used several objective measurements of phonatory function in sustained vowels, including translaryngeal airflow, laryngeal electromyography, and acoustic variables such as jitter, shimmer, and maximum phonation time. They found that transglottal airflow, jitter, and shimmer improved significantly after BT treatments and showed sustained improvement over time. "Electromyographic data showed decreased inappropriate muscle activity with repeated BT injections" (p. 393). (2)
Voice/Speech Sampling Measures
The measures used to evaluate vocal change following BT varies. For example, Cimino-Knight and Sapienza (2001) examined stability of acoustic measures of voice in connected speech across two injections spaced about 5 months apart in eight ADSD speakers who had been receiving BT treatment for 2 to 8 years. Recordings of oral readings of a standard paragraph were made from 3 to 7 months postinjection; however, they were not made during the period of peak benefit. These investigators observed no significant differences between two postinjection recordings.
Based upon the studies above, the long-term outcomes vary depending upon the time postinjection, type of speech samples employed (everyday speaking experiences, oral reading, or sustained vowel production), and the analysis techniques used to measure them (subjective self-ratings of voice quality, effort or quality of life vs. objective physiological or acoustic indexes). To date no long-term (i.e., multiple-injection) studies have reported objective acoustic measurements of connected speech across more than two or three injections.
Evaluating Connected Speech
Several investigators have studied acoustic speech behaviors in ADSD prior to and following a single BT injection using a variety of acoustic measurement techniques. Ludlow, Naunton, Terada, and Anderson (1991) measured phonatory breaks, sentence time, and aperiodicity in 10 ADSD patients. Measurements were made immediately preceding injection, at least 2 weeks postinjection, and at 2-week intervals until the patient showed evidence of vocal cord paralysis. At 4 months postinjection only sentence time showed a statistically significant change from preinjection levels. Sentence time remained significantly reduced in comparison to the prolonged durations exhibited prior to injection. Sapienza et al. (2002) examined occurrence of phonation breaks, frequency shifts, and aperiodic segments, as well as cumulative duration of 15 words excerpted from a standard reading passage, prior to BT injection and 3 to 6 weeks following. Cumulative word duration decreased in ADSD following BT, but remained significantly longer than that of normal controls. A combination of the voice-related acoustic measures improved following BT and significantly discriminated postinjection ADSD speech from normal speech.
Ford, Bless, and Patel (1992) reported when examining the efficacy of BT for ADSD that the greatest difference observed from pre- to post-BT was shown during conversational...
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