Successful treatment of speech disorders in individuals with progressive neuro logical diseases can be challenging. Hillman, Gress, Haugraf, Walsh, and Bunting (1990) stated that “voice treatment for disorders that are degenerative is controversial since there is no expectation for recovery of function or that any improvement secondary to speech language pathology intervention will be maintained in the long term” (p. 308). Individuals with idiopathic Parkinson disease (IPD) have been particularly resistant to speech treatment, with the conventional wisdom being summarized by the statement that changes observed in the treatment room disappear on the way to the parking lot (Allan, 1970; Aronson, 1985; Greene, 1980; Sarno, 1968; Weiner & Singer, 1989). The consensus that speech treatment has not been effective for individuals with IPD is, perhaps, the basis for the report that of the 75%–89% of these individuals with voice and speech disorders, only 3%–4% receive speech treatment (Hartelius & Svensson, 1994; Oxtoby, 1982).
The reduced ability to communicate is considered to be one of the most difficult aspects of IPD by many patients and their families. Soft voice, monotone, breathy, hoarse voice quality, and imprecise articulation (Darley, Aronson, & Brown, 1969a, 1969b; Logemann, Fisher, Boshes, & Blonsky, 1978), together with lessened facial expression (masked facies), contribute to limitations in communication in the vast majority of individuals with IPD (Pitcairn, Clemie, Gray, & Pentland, 1990a, 1990b). Although medical treatments, including neuro-pharmacological as well as neurosurgical methods, may be effective in improving limb symptoms, their impact on speech production remains unclear (Baker, Ramig, Johnson, & Freed, 1997; Kompoliti, Wang, Goetz, Leurgans, & Raman, 2000; Larson, Ramig, & Scherer, 1994; Rigrodsky & Morrison, 1970; Solomon et al., 2000; Wang, Kompoliti, Jiang, & Goetz, 2000; Wolfe, Garvin, Bacon, & Waldrop, 1975). In addition, previous speech treatment for individuals with IPD, focusing on articulation and rate, has limited efficacy data and limited evidence of long-term success. Recently, there has been great progress in understanding the function of the basal ganglia; this has shed light on the neural bases of IPD (Albin, 1995; Brooks, 1995; Hayes, Davidson, Keele, & Rafal, 1998; Mink, 1996; Wichmann & DeLong, 1993, 1996). Although many studies have used these findings to understand limb function in individuals with IPD (Rand & Stelmach, 1999; Weiss, Stelmach, Chaiken, & Adler, 1999), their application to voice and speech disorders has been infrequent. At this time, the neural mechanisms underlying speech, voice, and swallowing disorders in IPD are not well understood.