Prolonged persistence of hyaluronic acid after suboptimal vocal fold injection

Hyaluronic acid (HA) is a commonly used injectable material in temporary vocal fold injections (VFI) in patients with unilateral vocal fold paralysis (UVFP). Hyaluronic acid has generally been known for its three-six months of longevity following VFI. Owing to recent advances in cross-linking technologies, the longevity of HA-based materials, including deep-volumizing cross-linked HA used in VFI, has been improved. However, persisting injectable material in the subepithelial space poses undesirable complications following VFI. Herein, we report 2 cases of unexpected persistence of superficially injected cross-linked HA. In the first case, a 70-year-old man with iatrogenic UVFP received VFI with cross-linked HA three years ago and was referred for persistent dysphonia. Previously injected HA spilled out from the vocal fold (VF) when an epithelial incision was made in the subepithelial cystic lesion. In the second case, a 72-year-old woman with iatrogenic UVFP received VFI with cross-linked HA that migrated into the subepithelial space. Diffuse swelling of the injected VF caused dysphonia that lasted for a year. The previously injected HA spilled out when an epithelial incision was made in the swollen VF. Since superficially injected deep-volumizing cross-linked HA can persist for up to three years, laryngologists should be aware of possible sequelae upon suboptimal VFI with cross-linked HA.