We performed a retrospective chart review to compare the presence and types of abnormal muscle tension patterns (MTPs) in patients who had been diagnosed with glottal insufficiency before and after fiberoptic injection laryngoplasty. The main cause of glottal insufficiency had been unilateral vocal fold paralysis. Our review included an analysis of the medical records and laryngeal videostroboscopic recordings of 16 patients-9 men and 7 women, aged 25 to 87 years (mean: 59). Stroboscopic frames were analyzed for the presence of one or more types of abnormal MTP. Statistical analysis was performed to determine the significance of the change in scores for type II and type III MTP before injection and 1 month after injection. Before injection laryngoplasty, 15 of the 16 patients exhibited evidence of an abnormal MTP; 10 patients had MTP II only, 2 had MTP III only, and 3 patients had both. The mean percentage of frames showing MTP (i.e., MTP score) in patients with MTP II was 66.2% before the injection and 28.9% 1 month after; the decrease was statistically significant (p = 0.001). For MTP III, the corresponding figures were 71.6 and 37.7% (p = 0.043). We conclude that injection laryngoplasty has a positive effect on reducing muscle tension in patients with glottal insufficiency.