An Integrative Supraglottic Sound Source Taxonomy (SSST) for Pathological Speaking Voice: A Case Series

Supraglottic structures can participate in sound source creation when there is either pathological or healthy glottal-level voice production. For pathological voices, supraglottal structures may form part of the overall sound production, be associated with a presenting symptom, or may constitute a substitutional vibratory source. A recent taxonomy in healthy singing populations proposes four dimensions, including distinct phenotyping, vibrational strategies, level of control, and number of vibrating sources to distinguish among a number of supraglottic sound sources in healthy voices, yet differences and similarities between healthy and unhealthy involvement of supraglottic sound sources remain unclear. The purpose of this study was to extend the previously outlined supraglottic sound source taxonomy based in healthy singing populations to pathological voice and develop an integrative supraglottic sound source taxonomy (SSST).

A case series of seven patients identified as involving vibrations of supraglottic structures during routine clinical assessment were included and discussed according to the supraglottic sound source taxonomy dimensions. Patients were assessed using stroboscopy, electroglottography, and acoustic measures during sustained vowel tasks and continuous speech tasks at comfortable pitches.

Beyond supplementary and substitutional strategies for involving supraglottic sound sources, pathological voices may also recruit supraglottic structures in a compensatory manner allowing for improved vocal fold entrainment. The results suggest that compensatory strategies came in two forms, one for which the pathology necessitating supraglottic sound source involvement is irreversible (e.g., following extensive cordectomy) and one where the pathology is reversible (e.g., following medialization laryngoplasty procedure for unilateral paralysis). Accordingly, supraglottic vibrations can be separated into an integrative taxonomy that outlines supplementary, compensatory, or substitutional functions of vibration with further dimensions related to intentional or unintentional level of control, unisource or multisource number of supraglottic sound sources, and distinction of the involved supraglottic phenotypes. Previously identified distinct phenotypes were determined in the studied population according to the anatomical vibration source, including ventricular fold vibrations, arytenoid against arytenoid vibrations, cuneiform/arytenoid against epiglottis vibrations, and vibrations in the aryepiglottic free edge along with large vocal fold amplitude of vibrations. The study proposes hypotheses as to differences between healthy and pathological use of supraglottic vibrations along dimensions of laryngeal, respiratory, and resonatory technical ability and control.

The study presents an integrative SSST including phenotyping for both pathological and healthy voice. Diagnostic, surgical, rehabilitative, and pedagogical relevance is discussed.