This study aimed to analyse demographic profiles and pre-injection stroboscopic findings for patients with unilateral vocal fold paralysis, to investigate possible predictive factors for voice outcomes of injection laryngoplasty.

Fifty-nine unilateral vocal fold paralysis patients underwent vocal fold augmentation, using transcutaneous Artecoll (polymethyl methacrylate microspheres plus bovine collagen) injection into the paralysed vocal fold via the cricothyroid space. Three months later, patients were divided into improved (n = 44) and unimproved (n = 15) groups, using the perceptual grade-roughness-breathiness-asthenia-strain scale, and their clinical characteristics and pre-operative stroboscopic findings compared.

The improved group were significantly younger than the unimproved group (p = 0.000). The size of the posterior gap on phonation was closely associated with the outcome of injection laryngoplasty (p = 0.015).

Younger patients with a smaller posterior glottic gap on phonation can be expected to have a more favourable outcome following injection laryngoplasty for correction of glottic insufficiency due to unilateral vocal fold paralysis.