Plasticity of voice quality: a prognostic factor for outcome of voice therapy?

Plasticity of voice quality is defined here as the degree of improvement in deviant voice quality that can be achieved immediately or quasi-immediately by changing basic voicing conditions, posture, articulation or resonance, breathing mechanics, laryngeal position, or auditory feedback. Thirty-two adult patients with various benign organic voice pathologies, and who had a (preoperative) functional voice therapy, were scored before therapy using a weighted multidimensional Index of Voice Plasticity (IVP). The hypothesis is that IVP could be a predictor of the final outcome of functional voice therapy, and therefore a correlation with a comparable quantification of the actual results of the therapy was investigated. The IVP shows a satisfactory correlation (Spearman's rho = 0.68) with the efficacy of (preoperative) voice therapy. The IVP also significantly differs between diagnostic categories. Although its predictive value remains limited, the Index of Voice Plasticity seems helpful in decision making for indication of (presurgical) voice therapy.