Immediate impact of a short course of systemic corticosteroid on olfactory dysfunction, parosmia, and phantosmia

Systemic corticosteroids effectively treat conductive olfactory dysfunction from chronic rhinosinusitis. However, more evidence is needed for their effects on smell loss from other causes. This study measured the impact of a 7-day prednisolone course on quantitative and qualitative olfactory dysfunction in patients with postinfectious, post-trauma, and idiopathic smell disability. Data from 120 patients with olfactory dysfunction were analyzed. Scores on the University of Pennsylvania Smell Identification Test (UPSIT®), as well as ratings of self-perceived smell ability and complaints of parosmia and phantosmia, were determined before and immediately after the 7 days of treatment with 40 mg of oral prednisolone. Ten patients were controls. Twenty-six patients (23.6 %) experienced a clinically significant improvement of at least 4 UPSIT® points following prednisolone treatment, compared to only 10 % of the control group. Thirteen (24.5 %) of the 53 patients who had persistent olfactory dysfunction (≥6 months) had a clinically significant improvement after the steroid treatment. Nine patients with parosmia (18.4 %) improved this symptom after the treatment, while 5 (27.8 %) of those with phantosmia reported relief. Patients with worse function in the first visit exhibited greater recovery. COVID-19 patients generally presented earlier to medical consultation and had the highest chance of having parosmia (63.4 %) and phantosmia (22.9 %). This study supports the concept that a short course of prednisolone may be efficacious in cases of non-conductive quantitative and qualitative olfactory dysfunction. Additional clinical trials are needed to exclude its placebo beneficial effect on the qualitative complaints of parosmia and phantosmia. Level of evidence: 3. • There are few medications with high efficacy for non-conductive smell disturbances and even fewer for qualitative symptoms such as parosmia and phantosmia. • The results of this study demonstrate that a short course of prednisolone may be efficacious in quantitative and qualitative olfactory dysfunction. • Patients with worse initial smell capacity exhibited more remarkable recovery using this oral steroid. • A more prolonged onset (≥ six months) was not impeditive to an improvement. • 18.4% of patients with parosmia improved this symptom, and more than 25% of those with phantosmia reported relief.