Long‐Term Changes in Olfactory Threshold During Rehabilitation After Total Laryngectomy: A Preliminary Study

Objectives: This study aimed to evaluate the time-dependent changes in olfactory threshold and identification ability during olfactory rehabilitation in patients who had undergone laryngectomy and to investigate the recovery process for different odor types. Methods: Nineteen patients who underwent laryngectomy participated in olfactory rehabilitation using the nasal airflow-inducing maneuver (NAIM). Olfactory function was assessed at baseline and at 1, 3, 6, and 12 months post-NAIM. Results: Of the 19 participants, 12 (63.1%) continued the program for 6 months, whereas 8 (42.1%) completed the 12-month assessment. The mean olfactory threshold improved from 2.7 at baseline to -1.5 at 12 months, reaching normal levels by 1 month. The recognition threshold (identification ability) improved from 4.1 at baseline to -0.3 at 12 months, with significant recovery observed by 3 months. Odor-specific recovery patterns varied: Isovaleric acid showed improvement at 1 month; methyl cyclopentenolone, γ-undecalactone, and skatole at 3 months; and β-phenylethyl alcohol at 6 months. Conclusion: In patients who underwent laryngectomy, the olfactory thresholds recovered earlier than the identification abilities. The rate of recovery differed among odor types, with more rapid improvement observed for odors of physiological importance, such as putrid smells. Level of Evidence: 4 Laryngoscope, 2024.