Olfactory Improvement and Decline in Patients with Posttraumatic Olfactory Dysfunction

Objectives: Identify the prognosis for patients with post-traumatic olfactory dysfunction. Methods: From 2007 to 2013, patients with posttraumatic olfactory dysfunction were enrolled. The threshold, discrimination, and identification (TDI) score of Sniffin’ Sticks test was ≤15 for anosmia, ≥30 for normosmia, and between these values for hyposmia. Olfactory improvement/decline was defined as an increase/decrease in TDI score ≥ 6 points. The cumulative incidence rates of olfactory improvement and decline were calculated using the Kaplan-Meier method. Variables with a potential impact on olfactory changes were entered into Cox regression analysis. The correlation between the TDI scores of the first and last visit was evaluated. Results: We included 80 patients with an average 9.4-month follow-up period (range, 1-52 months). The 12-month cumulative rates of olfactory improvement and decline were 8.4% and 11.8%, respectively. Anosmia, hyposmia, and normosmia were noted in 71.2%, 27.5%, and 1.2% of the patients at the first visit and 72.5%, 23.8%, and 3.8% at the last visit (Fisher’s exact, P = .583). Multivariate analysis revealed no associations between clinical predictors and olfactory changes (all P > .05). A positive correlation between the TDI scores of first and last visit (Spearman test, Rho = 0.532, P < .001) confirmed the absence of significant changes in olfaction. Conclusions: Posttraumatic olfactory dysfunction was associated with a lower risk of decline in olfaction and a lower likelihood of improvement. Although most patients maintained a stable disease status, anosmia in the majority of patients may reflect a poor prognosis in olfactory recovery for patients with head trauma.