Quantifying changes in articulatory working space following oral cancer treatment

Introduction. Surgical treatment of oral cancer may limit the mobility of the affected articulator as shown by non-speech tasks, which may hinder communication. However, even though patients consistently rank speech as one of their top-priorities during and following treatment, articulatory consequences of oral cancer treatment have not been clearly characterised. The purpose of this study was to evaluate the range of movement of the tongue and jaw during speech by measuring the articulatory working space (AWS) of individuals who were surgically treated for oral cancer. We investigated whether the size of the AWS was (1) smaller in individuals treated for oral cancer compared to controls; (2) related to the type of treatment received; and (3) related to self-reported speech symptoms following treatment.

Method. Nine native speakers of Dutch who were surgically treated for a stage 3 or 4 squamous cell carcinoma of the oral cavity (5 male, 4 female; mean age = 61.6 years) and seven age-matched controls (4 male, 3 female; mean age = 61.3 years) participated. Individuals received treatment for a tumour located in the jaw (n=5) or on the tongue (n=4). Participants read the North Wind and the Sun passage while kinematic trajectories were recorded using electromagnetic articulography. The AWS (convex hull in mm2) was calculated using the anteroposterior and superior-inferior trajectories of the tongue-tip, tongue-back, and jaw sensor. Self-reported speech symptoms were quantified using the Speech Handicap Index (SHI).

Results. Descriptively, large individual variation in AWS was noted within both the clinical and control group. Compared to a sex-matched control group, the individuals who underwent treatment for oral cancer showed smaller AWS for the tongue-tip and tongue-back. In the clinical group, the AWS for the jaw showed more variability across individuals compared to AWS of the tongue-tip and tongue-back. On average, lower SHI scores (i.e., better speech outcomes) were associated with a larger AWS.

Conclusion. Despite large individual variation, most individuals treated for oral cancer show descriptively reduced tongue and jaw AWS when compared to controls. Whereas both treatment for jaw and tongue tumours reduced tongue AWS compared to controls, more variable results for jaw AWS were found across treatment sites. This suggests that there may be no one-to-one mapping between articulator mobility and primary treatment site. Overall, these findings specify specific kinematic changes in individuals who underwent oral cancer treatment that should be further explored in future studies. Kinematic data may be especially informative in designing new therapeutic approaches for this population as they directly measure articulatory changes.