Relationships Between Vocal Structures, the Airway, and Craniocervical Posture Investigated Using Magnetic Resonance Imaging

Objectives
Traditional voice research focuses on the vocal tract, articulators, and larynx. By ignoring their direct/indirect attachments (skull, cervical spine, and sternum) important information may be missed. We aim to investigate vocal structures within this wider context and assess the validity of this approach for subsequent voice production studies.

Study Design/Method
Using a cross-sectional study design, we obtained midsagittal MR images from 10 healthy adults (five males and five females) while at rest and breathing quietly. With reference points based on cephalometry, 17 craniocervical, craniocaudal, and anteroposterior variables were chosen to describe craniofacial morphology, craniocervical posture, and airway dimensions. Relationships between variables were sought using Pearson's correlation coefficient.

Results
We found widespread correlations relating vocal structures to the craniofacial skeleton and cervical spine (r > 0.6). Increasing airway size (hyocervical distance) was associated with greater distances from the cranial base of the hyoid, larynx, epiglottis tip and uvula tip, and of C3 from the menton. A wider velopharyngeal opening was associated with a shorter and higher soft palate, and a greater (lower) craniocervical angle was associated with a wider laryngeal tube opening, narrower airway at the uvula tip and shorter distances of the hyoid and uvula tip from the cranial base.

Conclusion
Finding widespread correlations relating vocal structures to the craniofacial skeleton and cervical spine confirms the potential of this approach to uncover functional activity during voice production and demonstrates the importance of considering vocal structures and the airway within this wider context if important information is not to be missed.