ABSTRACT
Purpose of Review: The purpose of this review was to summarize the current knowledge on parosmia and phantosmia and introduce support and treatment algorithms for the two qualitative olfactory disorders. Recent Findings: Recent literature regarding parosmia has revealed that patients with the disorder are mainly triggered by certain substances, including thiols and pyrazines. In 2015, the existing "olfactory training" regimen was improved to more effectively treat post-infectious olfactory loss and was named "modified olfactory training" (MOT). It was also found in 2022 that MOT is also effective against COVID-19-induced parosmia. Summary: Parosmia, the distortion of smells, is a symptom in qualitative olfactory disorders that severely affects patients' mental well-being and enjoyment of their everyday lives. The condition was first documented in 1895 and can affect up to 5% of the general population. Etiologies of parosmia include sinonasal diseases, viruses, surgeries, traumatic brain injury, neurological and psychiatric conditions, toxic chemicals, and medications. Parosmia has seen a surge in cases since the onset of the COVID-19 pandemic and is linked to changes in brain structure following an infection. The evaluation of the symptom is done using surveys, smell identification tests, fMRI, MRI, PET/CT, and gas chromatography. Treatment for parosmia can vary in duration, which makes it essential to focus not only on helping the patients regain normosmia, but also on supporting the patient through the recovery journey. Parosmia should not be confused with phantosmia, in which the distortion of smells occurs in the absence of olfactory stimuli. The etiology of phantosmia can vary from infections and traumatic brain injury to psychiatric disorders like schizophrenia. Unlike parosmia, the treatment of phantosmia is less straightforward, with an emphasis on determining the etiology and providing symptomatic relief.
ABSTRACT
OBJECTIVES: Coronavirus disease (COVID-19) infection often causes olfactory dysfunction and parosmia may occur in some patients with olfactory dysfunction. In this study, we retrospectively investigated the effectiveness of modified olfactory training (MOT) for the treatment of COVID-19-induced parosmia. STUDY DESIGN: This study presents results of MOT performed with 12 odors for 36 weeks in patients with olfactory dysfunction following COVID-19 infection. A total of 75 participants were included in the study (mean age 33 years, range 16-60 years). METHODS: The patients were separated into two groups: 1) Treatment group consisted of parosmia patients who received MOT with three sets of four different odors sequentially. 2) Control group consisted of parosmia patients who did not perform any olfactory training. Both groups were matched for age and sex distribution of participants. TDI scores were compared at the time of application and at the end of the 9th month by the Sniffin' Sticks Test. The results of the 0th and 9th months were recorded by applying the parosmia assessment scale to both groups. The results were analyzed statistically, and p < 0.05 was considered significant. RESULTS: When the treatment group and the control group were compared, a significant improvement was observed in both groups at the third, sixth, and ninth month, however the improvement in the treatment group was found to be better than in the control group (P < .001). Extending the treatment from 6 to 9 months in the treatment group was found to be effective in mitigating parosmia complaints and improving discrimination scores (P < .001). CONCLUSION: This study has shown that modified olfactory training is effective in the treatment of parosmia following COVID-19 infection. LEVEL OF EVIDENCE: 3 Laryngoscope, 132:1433-1438, 2022.