The impact of injury of the chorda tympani nerve during primary stapes surgery or cochlear implantation on taste function, quality of life and food preferences: A study protocol for a double-blind prospective prognostic association study.

BACKGROUND: The chorda tympani nerve (CTN) is a mixed nerve, which carries sensory and parasympathetic fibres. The sensory component supplies the taste sensation of the anterior two-thirds of the ipsilateral side of the tongue. During middle ear surgery the CTN is exposed and frequently stretched or sacrificed, because it lacks a bony covering as it passes through the middle ear. Injury may cause hypogeusia, ageusia or altered taste sensation of the ipsilateral side of the tongue. To date, there is no consensus regarding which type of CTN injury (sacrificing or stretching), during middle ear surgery, leads to the least burden for the patient. METHODS: A double-blind prospective prognostic association study was designed in a single medical centre in the Netherlands to determine the effect of CTN injury on postoperative taste disturbance and quality of life. 154 patients, who will undergo primary stapes surgery or cochlear implantation will be included. The taste sensation, food preferences and quality of life of these patients will be evaluated preoperatively and at one week, six weeks and six months postoperatively using the Taste Strip Test, Electrogustometry, supplementary questionnaire on taste disturbance, Macronutrient and Taste Preference Ranking Task, Appetite, Hunger and Sensory Perception questionnaire and Questionnaire of Olfactory Disorders to assess the association of these outcomes with CTN injury. Evaluation of olfactory function will only take place preoperatively and at one week postoperatively using the Sniffin' Sticks. The patient and outcome assessor are blinded to the presence or absence of CTN injury. DISCUSSION: This study is the first to validate and quantify the effect of chorda tympani nerve injury on taste function. The findings of this study may lead to evidence-based proof of the effect of chorda tympani injury on taste function with consequences for surgical strategies. TRIAL REGISTRATION: Netherlands Trial Register NL9791. Registered on 10 October 2021.

Prednisolone does not improve olfactory function after COVID-19: a randomized, double-blind, placebo-controlled trial.

BACKGROUND: Prednisolone has been suggested as a treatment for olfactory disorders after COVID-19, but evidence is scarce. Hence, we aimed to determine the efficacy of a short oral prednisolone treatment on patients with persistent olfactory disorders after COVID-19. METHODS: We performed a randomized, double-blind, placebo-controlled, single-centered trial in the Netherlands. Patients were included if they were > 18 years old and if they had persistent (> 4 weeks) olfactory disorders within 12 weeks after a confirmed COVID-19 test. The treatment group received oral prednisolone 40 mg once daily for 10 days and the placebo group received matching placebo. In addition, all patients performed olfactory training. The primary outcome was the objective olfactory function on Sniffin' Sticks Test (SST) 12 weeks after the start of treatment, measured in Threshold-Discrimination-Identification (TDI) score. Secondary outcomes were objective gustatory function assessed by the Taste Strip Test (TST) and subjective self-reported outcomes on questionnaires about olfactory, gustatory and trigeminal function, quality of life, and nasal symptoms. The CONSORT 2010 guideline was performed. RESULTS: Between November 2021 and February 2022, we included 115 eligible patients, randomly assigned to the treatment (n = 58) or placebo group (n = 57). No difference in olfactory function between groups was obtained after 12 weeks. Median TDI score on SST was 26.8 (IQR 23.6-29.3) in the placebo group and 28.8 (IQR 24.0-30.9) in the prednisolone group, with a median difference of 2.0 (95% CI 0.75 to 1.5). There was similar improvement on olfactory function in both groups after 12 weeks. Furthermore, on secondary outcomes, we obtained no differences between groups. CONCLUSIONS: This trial shows that prednisolone does not improve olfactory function after COVID-19. Therefore, we recommend not prescribing prednisolone for patients with persistent olfactory disorders after COVID-19. TRIAL REGISTRATION: This trial is registered on the ISRCTN registry with trial ID ISRCTN70794078.

COCOS trial: COrticosteroids for COVID-19-induced loss of Smell-protocol for a single-centred, double-blind, randomised, placebo-controlled trial.

INTRODUCTION: Hyposmia and anosmia are common in COVID-19. Most patients regain normal smell within 4 weeks, but severe loss of smell persists roughly in 20% after 2 months and may last up to a year or longer. These persistent smell disorders greatly influence daily life. It is hypothesised that COVID-19 induces inflammation around the olfactory nerve and in the olfactory pathway, leading to smell disorders. Corticosteroids might reduce this local inflammatory response and improve smell. METHODS AND ANALYSIS: We will conduct a single-centre, randomised, placebo-controlled trial to determine the efficacy of a short high-dose treatment of oral prednisolone for persistent loss of smell after COVID-19 in the early phase. We will include 116 patients with persistent (>4 weeks) loss of smell within 12 weeks of COVID-19 diagnosis, based on a positive PCR/antigen test. One group receives 40 mg of prednisolone for 10 days and the other group receives matching placebo treatment. In addition, all patients will perform smell training for 12 weeks. The primary outcome is objective olfactory function measured by means of sniffin' sticks test. Secondary outcomes are objective gustatory function by means of taste strips test and subjective taste and smell ability, trigeminal sensations, quality of life and nasal symptoms, measured by three questionnaires. These outcomes will be measured at inclusion before treatment and 12 weeks later. ETHICS AND DISSEMINATION: The Institutional Review Board of the University Medical Center Utrecht approved the research protocol (21-635/G-D, October 2021). The trial results will be shared in peer-reviewed medical journals and scientific conferences. TRIAL REGISTRATION NUMBER: NL9635. EUCTR2021-004021-71-NL.