The LSVT® was developed during the late 1980s. Initially, case studies, single-subject designs, and nonrandomized studies were published (120). These studies provided the first evidence of successful treatment outcomes for individuals with PD and suggested that intensive treatment focusing on increasing phonatory effort and self-monitoring of such effort could improve vocal communication in individuals with PD. On the basis of those findings, a number of randomized and blinded studies were conducted. In one study, 45 individuals with PD were randomly assigned to one of two forms of treatment: respiratory effort treatment (RET) or LSVT®. Short-(14) and long-term (15,118,121) data have been reported from these studies. Only subjects who received the LSVT® rated a significant decrease after treatment on the impact of PD on their communication. Corresponding perceptual ratings by blinded raters (122) revealed only the male subjects who had the LSVT® improved in ratings of breathiness and intonation. The acoustic findings were supported in studies at one-year (15) and two-year follow-up (118). Only those subjects in the LSVT® group improved or maintained vocal SPL above pre-treatment levels. In addition, perceptual reports by patients and family members supported the positive impact of LSVT®
on functional daily communication. In another study (123), 29 individuals with PD were studied over six months. Half the group received LSVT® and half of the group served as an untreated control group. In addition, neurologically healthy, age-matched controls were studied over this time period. Only subjects who received the LSVT® demonstrated significant increases in variables such as vocSPL (related to loudness) and semitone standard deviation (related to intonation) at post and six-month follow-up.
Improvement in laryngeal function with LSVT® has been documented physiologically. Smith et al. (41) found increases in vocal fold closure following treatment in individuals who received the LSVT® but not in individuals who received RET. These data were collected by clinicians not directly involved in the study and therefore support carryover of treatment effects. Importantly, laryngeal examination has shown no evidence of hyperfunctional laryngeal behaviors or vocal fold pathology induced by loud phonation training with LSVT®. In fact, it has been shown that LSVT® tends to decrease pre-treatment hyperfunctional behavior (false fold overclosure, anterior-posterior hyperfunction, laryngeal elevation) (124), increase subglottal air pressure and maximum flow declination rate (125), and reduce breathiness and hoarseness in individuals with PD (122). These findings reflect increased respiratory drive, improved vocal fold adduction, less abusive or strenuous voice use, and more efficient voice production after LSVT®.
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