Parosmia Associated with Functional Recovery from Post-Infectious Olfactory Dysfunction

What is the association between parosmia and phantosmia, and clinically relevant recovery of olfactory function in patients with post-infectious olfactory dysfunction (PIOD) receiving olfactory training (OT)?

BOTTOM LINE: The presence of parosmia is associated with clinically relevant recovery in olfactory discrimination and identification (suprathreshold) function in patients with PIOD who are receiving OT.

BACKGROUND: Parosmia and phantosmia are qualitative olfactory dysfunctions (OD) commonly found in patients with PIOD. OT is a side effect-free treatment option for smell loss that is effective in patients with OD. However, literature on symptoms of qualitative OD as a positive predictor of olfactory recovery after OT remains sparse.

STUDY DESIGN: Retrospective cohort study.

SETTING: Smell and Taste Clinic, Department of Otorhinolaryngology, Medical Faculty Carl-Gustav Carus, Technical University of Dresden, Germany.

SYNOPSIS: Researchers pooled data from three previously published studies on OT in adult patients who were seen between 2008 and 2018. Inclusion criteria were post-traumatic OD, PIOD, and idiopathic smell loss. A total of 246 subjects (106 men, 140 women, mean age 58.7 years) were included in the final analysis. All received OT as a therapy for their smell loss. Parosmia was most frequently present in PIOD (40.%), followed by post-traumatic OD (25.8%) and idiopathic OD (17.7%). In contrast, phantosmia was most commonly present in idiopathic OD (25.8%), followed by post-traumatic OD (19.3%) and PIOD (13.7%). Researchers’ analysis revealed that both lower baseline olfactory function and presence of parosmia at initial visit were prognostic predictors for clinically relevant recoveries in patients with PIOD. Authors state that prior suggestions that OT improves cognitive processing of olfaction-related sensory information might be associated with the improved outcome of patients who report parosmia. Study limitations included potential bias in results due to small differences in odors used in OT, and a lack of large sample sizes of etiologies other than PIOD.

CITATION: Liu DT, Sabha M, Damm M, et al. Parosmia is associated with relevant olfactory recovery after olfactory training. Laryngoscope. 2021;131:618-623.