Results of treatment of olfactory disorders after COVID-19 disease using olfactory training

Abstract

Objective: The aim of this study is to fi nd out how many patients with an ongoing smell and taste disorder after COVID-19 infection, can improve the subjective perception of smell by olfactory training method. Methods: Patients after COVID-19 (fi rst and second wave of the pandemic in 2020 and 2021) with persisting smell disorder (hyposmia, anosmia, parosmia, fantosmia) with or without taste disorder and while the olfactory disorder did not improve within one month afterrecovery, signed up on the website www.cuch.sk and asked for a testing set (perfumed felt-tip pens) to be sent. After a self-examination at home, each respondent fi lled out an on-line questionnaire and sent it to the Neurobio logical Institute of the BMC SAV. Patient with confi rmed hypo and anosmia underwent an ENT examination at contracted ENT workplaces in Slovakia. All the 117 patients included got through the olfactory training, twice a day, following the instructions. The control examination was performed after three and six months of smell training. Smell and taste status was evaluated by visual analogue scale (VAS) from 1 to 10 in admission and discharge of the study. According to VAS, the average entering olfactory status was 4 and the average taste status reached an average of 2. At admission, 28 patients entering the study suff ered from parosmia, 18 from phantosmia, and 20 from dysgeusia. Results: After the olfactory training, improvement of smell capability was observed in 96 patients, which is 73% from the whole group of patiets (117) with hyposmia and anosmia. The discharge olfactory score after 6 months of olfactory training reached grade 8 according to VAS. Improvement of taste capability was observed in 47 patients, which is 65% from the whole group of patients (72) with hypogeusia and dysgeusia. The discharge taste score after six months of olfacory training reached grade 4 according to VAS. However, various forms of dysgeusia, parosmia, or phantosmia persisted after the olfactory training in 18 patients. Conclusion: Smell (olfactory) training is currently considered the most eff ective rehabilitation method for improving impaired olfactory function after COVID-19 infection. Better subjective results were observed in the restitution of quantitative smell disorder than in quantitative taste disorder. Key words anosmia – hyposmia – COVID-19 – parosmia – phantosmia – hypogeusia – dysgeusia – olfactory training