Abstract
The authors investigated indication for phonosurgery for treatment of unilateral vocal fold paralysis based on laryngeal tomographs taken during sustained phonation of the vowel/u/, using a computed radiography system. As pre-operative quantitative indices, the thickness ratio (the ratio of the frontal sectional area of the paralyzed vocal fold to that of the other side, TR) and the level difference (the distance between the upper surfaces of the bilateral vocal folds, LD) were measured from pre-operative laryngeal tomographs. The TR represented a quantitative index of atrophy of the paralyzed vocal fold and the LD represented the level difference between the bilateral vocal folds. Results of phonosurgery were evaluated by post-operative mean air flow rate (MFR) and the AC/DC ratio, effective value of the AC component of expiratory air flow divided by mean flow rate (DC). The results were as follows;
1. Thyroplasty type I was indicated for the cases whose pre-operative TR was below 0.7 and LD was below 0.5mm.
2. A combination of thyroplasty type I and arytenoid adduction was indicated for the cases whose pre-operative LD was above 0.5mm and TR was below 0.7.
3. Intra-cordal injection of collagen was not indicated for the cases whose pre-operative TR was below 0.5 or LD was below 1.0mm.
