[Study on voice quality after different layers injured in vocal fold with CO2 laser microsurgery]

To investigate the nature of pathological voice after injured in different layers of vocal fold with CO2 laser microsurgery.

50 cases of precancerous lesion (keratosis and leukoplakia) were treated with laser mucosa ablation. Glottal carcinoma (Tis-T2) were treated with laser microsurgery in mucosal stripping(30 cases) or with laser cordectomy(60 cases). Vocal function was examined by acoustic analysis (F0, Jitter, Shimmer, NNE, HNR), aerodynamic analysis (MPT, S/Z) and videostroboscopic examination.

For lesion mucosa ablation, hoarseness improved quickly after operation and acoustic analysis became normal. There were 18.2% decreased mucosa wave, 16.7% mild-moderate supraglottal hyperfunction. For mucosa stripping (cover layers excised), 63.3% decreased and 10.0% absented with mucosa wave, 46.7% mild-moderate supraglottal hyperfunction, glottal closure was incomplete. Acoustic analysis showed that Jitter, Shimmer, F0 different from normal(P < 0.05), HNR significantly different from normal(P < 0.01). For cordectomy: Acoustic analysis showed significantly worse than normal(P < 0.01), 61.7% mild-moderate supraglottal hyperfunction. The ipsilateral mucosa wave was absent, but 30.0% showed mucosa wave of vocal process and 13.3% with ventricular fold wave. There was little difference with or without vocalis muscle excision in acoustic analysis. To compared with mucosa stripping, the NNE, HNR, Jitter, Shimmer of cordectomy group was worse and amplitude was higher in cordectomy(P < 0.01).

Although the acoustic characteristic and vibration mode of mucosa ablation and mucosa stripping was distinct to each other, within the cover layer injured, vocal function will be good. Once the body layer is injured, vocal quality will decrease significantly.