Effects of olfactory training on posttraumatic olfactory dysfunction: a systematic review and meta‐analysis

Abstract

Background Posttraumatic olfactory dysfunction is a clinical challenge due to refractory characteristics and limited therapeutic options. Olfactory training has been proved to be effective for olfactory dysfunction with varied etiologies. We pooled existing studies to evaluate the effects of olfactory training in patients with posttraumatic olfactory dysfunction. Methods A systematic literature review using PubMed, Embase, Cochrane Library, and Web of Science was conducted to identify studies assessing olfactory change in patients with posttraumatic olfactory dysfunction after olfactory training. Results Of the initial 812 abstracts reviewed, 13 full‐text articles were included. Clinically significant results after olfactory training were defined as an improvement of threshold, discrimination, and identification (TDI) score ≥6 or University of Pennsylvania Smell Identification Test (UPSIT) score ≥4. Six studies were included in the meta‐analysis, 36.31% (95% confidence interval [CI], 0.28 to 0.45) of posttraumatic patients would achieve clinically significant results after olfactory training with a mean increase of TDI score of 4.61. Conclusion Olfactory training might be a promising modality for the treatment of posttraumatic olfactory dysfunction. More high‐quality studies with controls are needed to clarify the effect of olfactory training on total olfactory performance and subcomponents of olfaction.

Clinical Implications of Psychophysical Olfactory Testing: Assessment, Diagnosis, and Treatment Outcome

“…Although patients with post-infectious olfactory dysfunctions experienced significant improvement of olfaction, a mean increase of 4.47 in TDI scores did not reach the minimal clinically important difference of 5.5 after treatment with short-term systemic steroids (Schriever et al, 2012). Our recent meta-analysis of the effects of olfactory training on post-traumatic olfactory dysfunction showed that post-traumatic patients would achieve clinically significant results after olfactory training with a mean increase of TDI score of 4.61 (Huang et al, 2021). The different treatment response of the odor threshold between post-traumatic and post-infectious olfactory dysfunction reveals different plasticity of the peripheral olfactory function after olfactory training.…”

Research Progress of Olfactory Nerve Regeneration Mechanism and Olfactory Training

“…The data indicated that OT could improve the ability of discrimination and identification of odors in patients with post-traumatic olfactory disorders within 8 months. 66 After 6 months of OT, odor sensitivity could be improved slightly but the ability of odor identification remained unchanged. 67 The authors postulated that the reasons for these inconsistent results might be due to differences in OT and olfactory-testing methods between institutions.…”

Year in review: 2021 IFAR article summary

“…With regard to treatment of impaired olfaction, a systematic review with meta-analysis evaluating the efficacy of olfactory training in the setting of posttraumatic olfactory dysfunction demonstrated a mean Sniffin' Stick threshold, discrimination, and identification (TDI) score increase of 4.61, suggesting that olfactory training could represent a promising modality for the treatment of posttraumatic olfactory dysfunction, but high-quality and controlled studies are needed. 38 Two unique studies evaluated the milieu of the olfactory cleft and olfactory function in CRS patients. A case-control pilot study by Soler et al 39 assessed specific mucous proteins and the proteomic profile of the olfactory cleft of using hierarchical clustering and bioinformatic analysis.…”

“…evaluated the psychometric properties of the Brief Questionnaire of Olfactory Disorders–Negative Statements, an abbreviated version of the parent survey, and demonstrated minimal information loss and excellent external predictive utility when compared to the original questionnaire when used in patients with CRS. With regard to treatment of impaired olfaction, a systematic review with meta‐analysis evaluating the efficacy of olfactory training in the setting of posttraumatic olfactory dysfunction demonstrated a mean Sniffin’ Stick threshold, discrimination, and identification (TDI) score increase of 4.61, suggesting that olfactory training could represent a promising modality for the treatment of posttraumatic olfactory dysfunction, but high‐quality and controlled studies are needed 38 …”