Unilateral vocal fold paralysis : Voice therapy and voice outcomes

Unilateral vocal fold paralysis (UVFP) is a debilitating condition arising from a recurrent laryngeal nerve injury due to iatrogenic, idiopathic or other intrinsic or extrinsic causes. The loss of voluntary vocal fold movement can result in marked changes in voice quality and performance (dysphonia) and have a significant impact on quality of life. UVFP is estimated to affect approximately 0.5% of the population - with dysphonia reported in 86.6% of all cases. Treatment for UVFP aims to improve the voice quality and restore the glottal sufficiency either through voice therapy, surgical intervention or a combination of the two. Selection of treatment type for UVFP is based on the severity of the glottal insufficiency, the associated dysphonia and the vocal requirements of the individual. However, there is currently limited evidence available to support decision making around the management of dysphonia for people with UVFP. There are a number of potential reasons for the current limitation in evidence, including: (1) inadequate development and documentation of the voice therapy program characteristics and (2) variable and inadequate application of voice outcome measures to determine treatment effect.

The first aim of my PhD is therefore to investigate the content, timing and dosage characteristics of voice therapy provided (by speech pathologists) to patients with dysphonia due to UVFP. This has resulted in three studies in my thesis: (1) a systematic review of the current relevant literature; (2) a cross-section international survey of current practice and (3) an in-depth qualitative study of expert practice. The findings of the three studies highlighted the lack of consistency in the application of voice therapy in the literature (Study 1), and then provided key information that informed the development of a schema that outlined the key stages involved in voice therapy treatment for patients with UVFP (Study 2 and Study 3) Key elements of this schema described factors that influence decision making and goal setting for voice therapy, the timing and intensity of therapy, the measurement of therapy outcomes, and decision making for the cessation of therapy. The schema could inform both future research into the efficacy of voice therapy in UVFP and clinical practice Together these studies will provide a triangulation of evidence to formulate a clear and prescriptive direction for voice therapy treatment for future efficacy studies, as well as for clinical practice.

The second aim of my PhD is to critically evaluate voice outcome measures that are used with patients with UVFP to determine treatment effects. There are a large number of potential voice outcomes to choose from (more than 50), across multiple dimensions of voicing (e.g. acoustic, aerodynamic, auditory-perceptual and patient self-rated measures) and therefore there is a need for clarity on the most appropriate means of detecting voice change over time. A systematic review was conducted to address the second aim. The systematic review critically evaluated the voice outcome measures used in the existing literature with respect to reliability, validity and responsiveness to change, as well as multidimensionality and procedural/protocol accuracy. The systematic review identified set of voice outcome measures with good psychometric properties that demonstrated their responsiveness to the treatment effect. The set of outcome measures could therefore be used for future research in UVFP.

Together the findings of this thesis provide the best evidence for the voice therapy management of UVFP and have identified several multi-dimensional voice outcome measures which are responsive to the treatment effect.