Long-term and Longitudinal Outcomes of Intracordal Trafermin Injection in Vocal Fold Paralysis

Intracordal trafermin injection (ITI) can improve vocal function in patients with unilateral vocal fold paralysis (UVFP) by promoting tissue regeneration and enhancing glottal gap. However, evidence on long-term and longitudinal outcomes remains limited. This study aimed to evaluate long-term and longitudinal outcomes of ITI in patients with UVFP.

This retrospective study was approved by the Ethics Committee (Approval No.22-S-11) and conducted at the Tokyo Voice Center between 2014 and 2025 using medical records. The final analysis included 221 cases. We extracted data on sex, age, dose, causative disease of UVFP, voice data (maximum phonation time [MPT], pitch range [PR], mean flow rate [MFR], and voice handicap index [VHI]), and the number of days from ITI to voice data measurement. This study did not estimate individual longitudinal changes; instead, it integrated days and improvements in all patients after ITI.

Regarding the long-term outcomes, no significant correlation was observed in the relationship between the number of days after ITI and voice improvement for MPT, PR, MFR, and VHI. All voice data improved over all periods. Regarding longitudinal outcomes, a generalized linear mixed-effects model analysis revealed no significant association between the number of days after ITI and VHI. Although significant differences were observed for MPT and PR, the estimated effect sizes were minimal and did not indicate clinically meaningful changes.

Voice improvement was achieved immediately after ITI and was maintained over the long term. However, longitudinal outcomes did not fully align with our clinical experience.