BACKGROUND. Cancer of the oral cavity is one of the most common malignancies of which 60% affect the tongue. Carcinoma of the tongue causes significant alterations of the articulatory and swallowing functions. The gold standard of care remains primary surgical resection with or without postoperative adjuvant therapy. Whereas T1 and T2 tongue tumors can be treated with more conservative surgeries, as partial glossectomies, the larger tumors require total and aggressive glossectomies which increase survival, but, on the other hand, they might often make speech, chewing and swallowing impossible.

MATERIAL AND METHODS. Our study was performed on a total of 21 patients with Squamous Cell Carcinoma of the tongue who underwent either partial resection or hemiglossectomy. Each subject (either surgical patients or controls) was asked to pronounce the vowels /a/, /e/, /i/, /u/, and all signals were evaluated separately by two operators. Acoustic (F0, jitter, shimmer, NHR) and vowel metric (the ratio F2i/F2u, tVSA, qVSA, FCR) features have been extracted. In order to define the speech intelligibility, all patients were evaluated by two doctors and one speech therapist and all patients received the Speech Handicap Index (SHI) translated into Italian language before recording.

RESULTS. No statistically significant variations were observed, regardless of the gender, between controls and surgically resected patients when tumor staging was T1-T2. On the contrary, when patients had to undergo more extensive surgical resection due to the presence of a T3-T4 tumor, a dramatic increase of F2u could be observed. This change, together with a decrease of F2i, led to a highly significant reduction in the F2i/F2u parameter in surgically resected patients as compared to controls. The other parameters which were reduced in a statistically significant manner in T3-T4 surgically resected patients were tVSA and qVSA. Instead, two parameters increased in a statistically significant manner in T3-T4 surgically resected patients: FCR and SHI. Again, none of the above-mentioned parameters was altered in a statistically significant manner in early tumor stage resected patients, regardless of the gender.

CONCLUSION. For the first time, we used a series of newly developed formant parameters, introduced by various authors for the study of the articulatory undershoot of the tongue in various neurodegenerative diseases. The statistical analysis of our results highlighted in an incontrovertible way a strong correlation and significance of each of our parameters F2 / i / / F2 / u /, FCR, tVSA, qVSA, with the entity of the TNM, and therefore of the surgical extension of the resection, and in parallel with the loss of the intelligibility of the speech that proportionally reaches higher values in the advanced stages of the disease as can be deduced from the SHI trend.