The speech therapy approaches presented in this chapter are organized by laryngeal pathophysiology rather than specific neurological disorders. The traditional approach has attempted to relate neurological diagnoses with certain voice characteristics and consequently certain treatment approaches. We assume that a direct relationship exists between the laryngeal pathophysiology (biomechanical conditions of the oscillator) and the resulting voice characteristics, regardless of the specific diagnosis. This approach accommodates the numerous sources of variation in voice characteristics accompanying neurological disorders, such as compensatory behaviors, multiple neural pathologies and neuropharmacological effects, and facilitates application of principles of normal laryngeal function to treatment.

When laryngeal dysfunction is a primary contributor to reduced speech intelligibility, voice therapy is designed to maximize improvement in speech intelligibility by changing or compensating for underlying laryngeal pathophysiology. Laryngeal dysfunctions in patients with neurological disorders include problems in adducting the vocal folds (hypoadduction, hyperadduction), producing a stable voice (phonatory instability) and coordinating movements (phonatory incoordination) . These dysfunctions may reduce speech intelligibility by affecting the perceptual characteristics of pitch, loudness, quality, intonation and voice- voice less contrasts.

When laryngeal function is affected due to a neurological disorder, other components of the speech mechanism frequently are affected as well. Therefore, it is important to assess laryngeal function and apply treatment strategies within the framework of the entire speech mechanism. One such framework includes nine functional components which are primarily responsible for producing speech: diaphragm, abdomen, rib cage, larynx, velopharynx, posterior tongue, lips and jaw. Using a sampling of perceptual, acoustic, aerodynamic and physiologic measures, the speech pathologist evaluates the individual and interactive contribution of all components to a reduction in speech intelligibility and makes hypotheses about the pathophysiology underlying the disordered speech. This information, used in combination with otolaryngological and neurological findings, will result in a program of speech therapy that will maximize treatment outcomes for each patient.