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

Supraglottic structures frequently contribute to the generation of sound during both disordered and healthy glottal-level voice production. Prior research has shown that these anatomical components can form an integral part of the overall acoustic output or serve as a substitutional vibratory source. A framework recently established for healthy singing populations utilizes four specific dimensions to categorize these diverse sound sources. These dimensions include distinct phenotyping, specific vibrational strategies, the level of conscious control, and the total number of active vibrating sources. Clinical observations indicate that supraglottic involvement often accompanies presenting symptoms in patients with laryngeal dysfunction. The precise similarities and differences between healthy recruitment and unhealthy involvement of these structures remain largely undefined in current literature. This absence of evidence motivated the development of a more comprehensive classification system to address the complexities of pathological phonation.

This investigation expands the previously established framework for healthy singers to include the nuances of pathological speaking voice presentations. The primary objective involved creating an integrative Supraglottic Sound Source Taxonomy (SSST) that encompasses both healthy and disordered vocal states. Researchers aimed to evaluate how supraglottic vibrations function as compensatory mechanisms when primary vocal fold vibration is impaired. The study sought to categorize these vibrations across dimensions of intentionality and the number of active sound sources. By analyzing a specific case series, the authors intended to identify unique phenotypes associated with various laryngeal pathologies. The project focused on determining if these secondary sources improve vocal fold entrainment in patients with structural or functional deficits. The work clarifies the functional roles of supplementary, compensatory, and substitutional strategies within a unified diagnostic framework.

The research team conducted a case series involving seven patients who exhibited supraglottic vibrations during routine clinical voice assessments. Clinicians employed stroboscopy to visualize the mucosal wave and the specific anatomical sites of secondary vibration. Electroglottography (EGG) provided objective measurements of the contact patterns between the vocal folds and adjacent supraglottic tissues. Acoustic measures were systematically recorded while participants performed sustained vowel tasks to evaluate the stability of the sound source. The protocol included continuous speech tasks performed at comfortable pitches to observe vibratory behavior during natural communication. Each patient was evaluated based on the four dimensions of the taxonomy, including phenotyping and the level of vocal control. The study utilized these diverse data points to map pathological behaviors onto the existing dimensions of the Supraglottic Sound Source Taxonomy (SSST).

The analysis demonstrated that pathological voices recruit supraglottic structures through supplementary, substitutional, and distinct compensatory strategies. Compensatory recruitment occurred in two specific forms depending on whether the underlying laryngeal pathology was reversible or irreversible. Irreversible conditions, such as those following an extensive cordectomy, necessitated permanent supraglottic involvement to facilitate effective vocal fold entrainment. Reversible pathologies, exemplified by unilateral paralysis cases following medialization laryngoplasty, showed different patterns of structural recruitment. The researchers identified several distinct phenotypes, including ventricular fold vibrations and contact between the arytenoid cartilages. Other observed patterns involved the cuneiform or arytenoid structures vibrating against the epiglottis or vibrations along the aryepiglottic free edge. These findings suggest that pathological supraglottic use differs from healthy use across dimensions of laryngeal, respiratory, and resonatory control.

The integrative Supraglottic Sound Source Taxonomy (SSST) offers a standardized method for classifying secondary sound sources in clinical settings. These findings indicate that the functional intent of supraglottic vibration is a critical factor in determining appropriate treatment paths. The distinction between compensatory and substitutional strategies provides a clearer understanding of laryngeal adaptation to injury or disease. The authors propose that this taxonomy has significant relevance for diagnostic, surgical, rehabilitative, and pedagogical applications. Future investigations may use these dimensions to refine therapeutic interventions for patients with complex voice disorders. The study emphasizes the need for multi-dimensional assessment to capture the full complexity of laryngeal vibratory behavior. This classification system facilitates better communication among the multidisciplinary teams involved in voice care and vocal training.