Mood Impairment in Patients with Olfactory Loss Predicts a More Pronounced Recovery of Olfactory Function.

BACKGROUND: Here, we refer to our publication "Symptoms of depression change with olfactory function" [Sci Rep. 2022 Apr 5;12(1):5656]. OBJECTIVES: Depression decreases with olfactory improvement, but the question remains open of whether patients who indicate more suffering regarding mood impairment exhibit a different pattern of recovery from olfactory loss compared to those who suffer less. METHOD: In the course of an additional investigation of our previously published dataset, we established groups of participants (N = 171) with low (≤8 points on a depression [ADSL] scale; 47%; n = 45) and high (≥14 points on ADSL scale; 53%; n = 53) mood impairment. RESULTS: We found that the group that reported more sufferance on a depression [ADSL] scale improved more in change of olfactory function, and, more importantly, odor discrimination change over a period of an average of 11 months. CONCLUSION: Patients, who suffered more, as indicated by higher scores on ADSL scale, may have been more willing to commit to the study protocol, and thus their improvement was more notable.

Consequences of gaining olfactory function after lifelong anosmia.

We present a rare case in which a patient has gained her smell after lifelong anosmia. The patient was objectively tested and diagnosed with functional anosmia at age 13 and reported they were experiencing a new sensation of smell at age 22. Our results show an electrophysiological signal for two unimodal odorants. The patient had a retronasal score in the hyposmic range and self-reported the ability to smell non-trigeminal odors, but reported being disturbed by the presence of the new sense and co-occurrence of phantosmia. We discuss our case in routes of neurogenesis and non-forming memory association with odors.

Prevalence and Prognostic Factors Associated with Early Recovery of Olfactory Dysfunction in COVID-19 Patients.

BACKGROUND: The prevalence of smell dysfunction, along with its risk factors, has been evaluated in previous literature; however, little has been established regarding its relation to other factors such as disease severity, history of coronavirus disease-2019 (COVID-19) vaccinations, and medical treatment for COVID-19 infection. These factors may impact the overall recovery of olfaction in COVID-19 patients. OBJECTIVE: This study investigated the prevalence of early olfactory recovery from COVID-19 infection and its associated factors. METHODS: This study was a prospective cohort study on 348 COVID-19 patients with a new onset of anosmia or hyposmia. Smell sensation scores on the olfactory self-assessment test were collected at baseline and every week until 6 weeks of follow-up. The primary outcome was the prevalence of early olfactory recovery. The secondary outcomes were analyzing factors associated with early olfactory recovery and the median time to complete recovery of smell loss. RESULTS: The prevalence of early olfactory recovery was 63.1% (95% CI: 0.58-0.68), and significant associated factors in multivariate analysis included patients without allergic rhinitis (OR 2.22, 95% CI: 1.12-4.40, P = 0.023) and no alteration of taste perception (OR 1.62, 95% CI: 1.02-2.57, P = 0.042). The median time to complete recovery from smell loss was 2 weeks. CONCLUSION: The present study found that the prevalence of early olfactory recovery within 2 weeks was 63.1%. The median time to olfactory recovery was also 2 weeks. Patients without allergic rhinitis and taste alteration had a significantly better chance of early recovery of olfactory function.

Olfactory training assists in olfactory recovery after sinonasal surgery.

Objectives: Olfactory dysfunction is a common complaint in patients with chronic rhinosinusitis (CRS). The study aimed to evaluate the effectiveness of olfactory training (OT) in patients with CRS after sinonasal surgery. Methods: We enrolled 111 patients with CRS who underwent sinonasal surgery. Prior to surgery and 3 months after starting OT, the participants were assessed by both an olfactory function test and endoscopy. The Korean version of the Sniffin' Stick II (KVSS-II) was used to perform the olfactory function test. Over the course of 3 months, five odorants were used in OT (rose, lemon, cinnamon, orange, and peach). Results: Over a 12-week duration, 37% of the participants in the OT group showed clinically relevant increase in olfactory function. The OT group had significantly higher olfactory outcomes for the total KVSS-II and identification scores than the non-OT group between the initial and follow-up assessments. The initial score influenced the degree of olfactory improvement after OT. Conclusions: Patients with OT exhibited significantly higher total KVSS-II scores compared with non-OT patients following sinonasal surgery; in particular, the odor identification score was different between the two groups. The results of this study demonstrated that a 12-week period of repeated short-term exposure to various odors could be useful in enhancing olfactory activity in patients who underwent sinonasal surgery for the improvement of sensory-neural olfactory impairment. Level of evidence: 2c.

Effect of early olfactory training on olfactory recovery after nasal endoscopy in patients with chronic rhinosinusitis and olfactory impairment.

OBJECTIVE: To analyze the effect of early comprehensive olfactory rehabilitation training on olfactory recovery after nasal endoscopy in patients with chronic rhinosinusitis and olfactory impairment. METHODS: A retrospective study was conducted on 67 patients with chronic rhinosinusitis combined with olfactory impairment in our hospital from July 2018 to August 2020. Patients were divided into control group and observation group according to the time of implementing comprehensive olfactory rehabilitation training. The control group received non-early comprehensive olfactory rehabilitation training at 2 weeks after nasal endoscopy, and the observation group received early comprehensive olfactory rehabilitation training at 1 week after nasal endoscopy. The minimum detection/recognition threshold, olfactory threshold, olfactory function and quality of life were compared between the two groups. RESULTS: After 3 months of training, T&T olfactory test scores in the observation group were significantly lower than those in the control group (P<0.05). The minimum detection scores in the observation group were lower than those in the control group after 1, 2 and 3 months of training, and the recognition scores in the observation group were higher than those in the control group (P<0.05). The scores of olfactory threshold, odor discrimination, and odor identification of the observation group after 1, 2 and 3 months of training were higher than those of the control group (P<0.05). After 3 months of training, the self-description scores of quality-of-life questionnaires in the observation group were higher than those in the control group, and visual analogue scale (VAS) scores in the observation group were lower than those in the control group (P<0.05). CONCLUSION: Early comprehensive olfactory training can improve the olfactory threshold and odor discrimination of patients with chronic rhinosinusitis combined with olfactory impairment after nasal endoscopy, improve the quality of life, and have a positive effect on olfactory recovery.

Recovery of rainbow trout olfactory function following exposure to copper nanoparticles and copper ions.

In response to environmental information received by olfactory sensory neurons (OSNs), fish display different behaviors that are crucial for reproduction and survival. Damage to OSNs from direct exposure to environmental contaminants can disrupt fish olfaction. Copper nanoparticles (CuNPs) are neurotoxic contaminants which can impair fish olfactory function. However, it is uncertain if CuNP-induced olfactory dysfunction is reversible. Here, we compared the recovery of rainbow trout olfactory mucosa after being exposed to CuNPs or dissolved copper (Cu2+). Following a 96 h exposure to CuNPs or Cu2+, recovery was tested 14 min and 7 days after exposure using electro-olfactography (EOG). Results indicated the 14 min recovery period was not sufficient to improve the olfactory sensitivity in either Cu treatment. After 7 days of transition to clean water, olfactory mucosa was able to recover from Cu2+-induced dysfunction, while no recovery was observed in the CuNP-exposed OSNs. This olfactory dysfunction in the CuNP treatment was observed when no Cu was significantly accumulated in the olfactory mucosa after the recovery period. The transcript abundances of a subset of genes involved in olfactory signal transduction (OST) were downregulated in the CuNP-exposed fish after the 7-day recovery period. These results revealed that odorant reception through OST cascade remained impaired over the recovery period in the CuNP-treated OSNs. The ion regulation gene transcripts were not dysregulated in either Cu treatment, which suggests that neural ion balance was not affected following the recovery period. Collectively, our findings revealed the CuNP-induced olfactory dysfunction was irreversible after the 7-day recovery period. Given the importance of olfaction in crucial aspects of fish life, it is likely that the CuNP-induced impairment of odorant reception pose risks to the survival of fish.

Evolution of Olfactory Disorders in COVID-19 Patients.

OBJECTIVES: A high frequency and a strong association of olfactory/gustatory impairment with COVID-19 were reported. Its spontaneous evolution remains unknown. The aim of this study was to investigate the spontaneous evolution of olfactory disorders in COVID-19 patients. STUDY DESIGN: Cross-sectional study. METHODS: A total of 229 patients with laboratory-confirmed COVID-19 from March 1 through 31, 2020 in our institution were included. Among them, 140 patients (mean age, 38.5 years, 89 women) reported sudden olfactory/gustatory disorders during COVID-19. All patients were interviewed by phone based on a questionnaire with 16 questions at time of survey. The primary end point was olfactory recovery rate at time of survey. RESULTS: The frequency of patients with olfactory disorders was higher before March 20, 2020 than since (70.3% vs. 53.9%, respectively) (P = .016). At time of survey (26 days of the mean time from anosmia onset), 95.71% reported to start an olfactory recovery. The mean time from olfactory loss onset to recovery onset was 11.6 days. Recovery started between the fourth and the fifteenth day after olfactory loss onset in 78.4% of patients. Complete olfactory recovery happened for 51.43% of patients. There was a significant relationship between the complete olfactory recovery and a short time from olfactory loss onset to recovery onset (P = .0004), absence of nasal obstruction (P = .023) and absence of sore/dry/tingling feeling in the nose (P = .007) in COVID-19 patients. CONCLUSION: Knowledge of spontaneous evolution of olfactory disorders allows reassuring patients and planning therapeutic strategies for persistent olfactory dysfunction after having definitely recovered from COVID-19. LEVEL OF EVIDENCE: 4 Laryngoscope, 130:2667-2673, 2020.

Differential response of olfactory sensory neuron populations to copper ion exposure in zebrafish.

The peripheral olfactory system of fish is in direct contact with the external aqueous environment, so dissolved contaminants can easily impair sensory functions and cause neurobehavioral injuries. The olfactory epithelium of fish is arranged in lamellae forming a rosette in the olfactory cavity and contains three main types of olfactory sensory neurons (OSNs): ciliated (cOSNs) and microvillous olfactory sensory neurons (mOSNs), common to all vertebrates, and a third minor group of olfactory neurons, crypt cells, absent in tetrapods. Since copper is a ubiquitously diffusing olfactory toxicant and a spreading contaminant in urban runoff, we investigated the effect of low copper concentration on the three different OSNs in the olfactory epithelium of zebrafish, a model system widely used in biological research. Image analysis was applied for morphometry and quantification of immunohistochemically detected OSNs. Copper exposure resulted in an evident decrease in olfactory epithelium thickness. Moreover, after exposure, the lamellae of the dorsal and ventral halves of the olfactory rosettes showed a different increase in their sensory areas, suggesting a lateral migration of new cells into non-sensory regions. The results of the present study provide clear evidence of a differential response of the three neural cell populations of zebrafish olfactory mucosa after 96h of exposure to copper ions at the sublethal concentration of 30µgL-1. Densitometric values of cONS, immunostained with anti-G αolf, decreased of about 60% compared to the control. When the fish were transferred to water without copper addition and examined after 3, 10 and 30days, we observed a partial restoration of anti-G αolf staining intensity to normal condition. The recovery of cOSNs appeared sustained by neuronal proliferation, quantified with anti-PCNA immunostaining, in particular in the early days after exposure. The densitometric analysis applied to mOSNs, immunostained with anti-TRPC2, revealed a statistically significant decrease of about 30% compared to the control. For cOSNs and mOSNs, the decrement in staining intensity may be indicative of cell death, but reduction in antigen expression may not be excluded. In the post-exposure period of 1 month we did not find recovery of mOSNs. We hypothesize that cOSNs are more sensitive than mOSNs to copper treatment, but also more prompted to tissue repair. Anti-TrkA-immunopositive crypt cells appeared not to be affected by copper exposure since statistical analysis excluded any significant difference between the control and treated fish. Comparative studies on OSNs would greatly enhance our understanding of the mechanisms of olfaction.