Causes Of Olfactory Dysfunction Research Articles

CASE REPORT : OLFACTORY GROOVE MENINGIOMA

Abstract
 Background: Olfactory Groove Meningiomas (OGM) are a rare cause of olfactory dysfunction. OGMs are benign, slow-growing tumors that cause non-specific symptoms, such as headaches, olfactory impairment, and psychiatric symptoms, such as depression, personality changes, decreased cognitive function, visual problems, or seizures.
 Aim: In this case report we would like to discuss about a rare case of olfactory groove meningioma with non-spesific symptoms presented in 47-year old female patient
 Case report: A 47-year old female with progressive blurred vision in the right eye for 3 months. Negative light perception in the right eye and fundus of the right eye indicated papillary atrophy. The direct and indirect light reflexes were negative in the right eye. We found Strong homogenous contrast enhancement extraaxial lesion accompanied by multiple dural tails in the left frontal convexity UK approximately 3.2 x 2.8 x 3.1 cm, Tuberculum sellae approximately 2.7 x 2.9 x 3 cm. Cranial decompression, frontal bone reconstruction, and tumor removal were performed. It was found that there was microcystic growth of tumor tissue, consisting of proliferation of meningoethelial cells, round to oval nuclei, smooth chromatin, visible intranuclear inclusions
 Discussion: OGM is a rare, benign tumor. Female patients were more likely to develop OGM than male patients. The ciliary ganglion of cranial nerve III may be affected by compression of the tumor, resulting in the absence of direct and indirect pupillary reflexes in the affected eyes.
 Conclusion: OGM is a slow-growing tumor that does not show significant symptoms at an early stage, making early detection difficult.
 Keyword: Olfactory Groove Meningioma, Blurred Vision, Meningioma

Exhaled Nitric Oxide and Olfactory Dysfunction in Patients with Asthma: Association with Chronic Rhinosinusitis.

Objectives: Olfactory dysfunction is a clinical sign that is important to detect with coexistent upper airway comorbidities in patients with asthma. This study aimed to investigate the etiology of olfactory dysfunction in patients with asthma and the relationship between fractional exhaled nitric oxide (FeNO) levels. Materials and Methods: This study included 47 asthma patients who were evaluated for olfactory dysfunction at Hiroshima University Hospital between 2012 and 2020. The etiologies of olfactory dysfunction were evaluated, and they were classified according to the FeNO levels of patients with asthma. Results: Olfactory dysfunction was observed in 30 patients with asthma, with chronic rhinosinusitis (77%) being the most prevalent etiology. Eosinophilic chronic rhinosinusitis (ECRS) was the most prevalent etiology of olfactory dysfunction in asthma patients with high FeNO levels (≥25 ppb), while non-eosinophilic chronic rhinosinusitis (NCRS) was the most prevalent etiology in asthma patients with low FeNO levels (<25 ppb). Additionally, the prevalence of ECRS was significantly higher in asthma patients with olfactory dysfunction and high FeNO levels (74%) than in those with either high FeNO levels or olfactory dysfunction and those with low FeNO levels and no olfactory dysfunction (12% and 9%, respectively). Conclusions: We found that ECRS was the predominant cause of olfactory dysfunction in patients with high FeNO levels, while NCRS was more common in those with low FeNO levels. The present study showed that both ECRS and NCRS are common etiologies of olfactory dysfunction in patients with asthma. Additionally, this study supports the link between upper and lower airway inflammation in patients with asthma complicated with olfactory dysfunction.

Efficacy of Gabapentin For Post–COVID-19 Olfactory Dysfunction

The COVID-19 pandemic affected millions of people and has become a dominant etiology of olfactory dysfunction (OD). No interventions with definitive clinical utility exist. Gabapentin represents a potential therapy for COVID-19-induced OD. To evaluate the efficacy of oral gabapentin on olfactory function and olfaction-related quality of life in patients with COVID-19-induced OD. This pilot double-blinded, placebo-controlled randomized clinical trial (RCT) was conducted at Washington University School of Medicine in St Louis from January 7, 2022, to February 3, 2023. Adults with at least 3 months of OD after COVID-19 infection were eligible for inclusion. Participants with a history of other causes of OD or contraindications to gabapentin were excluded. Patients were randomized 1:1 to oral gabapentin or placebo. All patients underwent titration to a maximum tolerable dose, which was maintained during an 8-week fixed-dose (FD) phase then tapered off. Participants were monitored for 4 weeks following cessation of study medication. Outcomes were assessed following the 8-week FD phase and 4 weeks after taper completion. The primary outcome measure was the response rate determined by subjective improvement in OD on the Clinical Global Impression of Improvement (CGI-I) after the FD phase. Other subjective and objective measures of olfactory function were also assessed as secondary outcome measures. Sixty-eight participants were enrolled (34 randomized to each arm), a total of 44 participants completed the FD period and 20 (45.4%) reported response to treatment with at least slight improvement in olfaction from baseline. Of those randomized, 51 (75%) were women and 56 were White (82%) with a mean (SD) age of 43 (13.5) years. Baseline demographic features including age, sex, and race and ethnicity were not significantly different between the groups. Of the 18 participants in the gabapentin group, 8 (44%) were responders and of the 26 participants in the placebo group, 12 (46%) reported response to treatment (percent difference, 1.7%; 95% CI, -31.6% to 28.2%). Mixed-model analysis of all secondary outcome measures demonstrated no clinically meaningful or statistically significant difference between the gabapentin and placebo groups throughout the trial. There were no serious adverse events. In this randomized clinical trial, gabapentin was not associated with statistically significant or clinically meaningful benefit over placebo and likely is not an efficacious therapy for COVID-19-induced OD. ClinicalTrials.gov Identifier: NCT05184192.

Structural, functional and behavioral impact of allergic rhinitis on olfactory pathway and prefrontal cortex

BackgroundAllergic rhinitis (AR) has been identified as a cause of olfactory dysfunction. Beyond the classic symptoms, AR has been associated with altered sleep patterns, a decline in cognitive performance and higher likelihood of depression and anxiety. The olfactory pathway has been postulated to be a possible link between nasal inflammation and central nervous system (CNS) modifications. Thus, we aimed to investigate the structural, functional and behavioral changes in the olfactory pathway and related areas in an animal model of AR. MethodsAR was induced in adult Wistar rats by ovalbumin sensitization and challenge. Following olfactory and behavioral tests we investigated the synaptic structure of the olfactory bulb (OB), anterior olfactory nuclei (AON), piriform cortex and prefrontal cortex (PFC), by immunofluorescence detection of synaptophysin (Syn) and glutamatergic, GABAergic and dopaminergic neuronal markers. ResultsWe detected a significant decrease in Syn in the glomerular layer (GL) of OB and in the PFC of the AR group. Additionally, the optical density of GAD67 and VGLUT2 was reduced in the OB, AON and PFC, compared to controls. The behavioral tests demonstrated olfactory dysfunction and reduced male aggressiveness in AR rats, but we did not find any difference in the cognition and anxiety-like behavior. ConclusionsWe confirmed olfactory dysfunction in a rat model of AR and we identified modifications in synaptic activity by reduction of Syn optical density in the GL of the OB and in the PFC. This was accompanied by structural changes in glutamatergic and GABAergic activity in essential components of the olfactory pathway and PFC.

Olfaction Now and in the Future in CRSwNP.

Chronic rhinosinusitis (CRS) is the leading cause of olfactory dysfunction in the general population. Olfactory dysfunction is more common in patients with CRS with nasal polyposis (CRSwNP) compared to those without polyps. The present review aims to summarize the current literature on the mechanism behind olfactory dysfunction in CRSwNP and the impact of therapy on olfactory outcomes in this patient population. A comprehensive review of the available literature on olfaction in CRSwNP was performed. We evaluated the most recent evidence from studies on the mechanisms behind smell loss in CRSwNP and the impact of medical and surgical therapy for CRS on olfactory outcomes. The mechanism behind olfactory dysfunction in CRSwNP is not completely understood, but evidence from clinical research and animal models suggests both an obstructive component causing conductive olfactory loss and an inflammatory response in the olfactory cleft leading to sensorineural olfactory loss. Oral steroids and endoscopic sinus surgery have both shown efficacy in improving olfactory outcomes in CRSwNP in the short term; however, the long-term response of these treatments remains uncertain. Newer targeted biologic therapies, such as dupilumab, have also shown remarkable and durable improvement in smell loss for CRSwNP patients. Olfactory dysfunction is highly prevalent in the CRSwNP population. Although significant advances have been made in our understanding of olfactory dysfunction in the setting of CRS, additional studies are needed to elucidate cellular and molecular changes mediated by type 2-mediated inflammation in the olfactory epithelium with potential downstream effects on the central olfactory system. Further identification of these underlying basic mechanisms will be vital for developing future therapies targeted to improve olfactory dysfunction in patients with CRSwNP.

Interpretation of the 2021 American Academy of Allergy, Asthma and Immunology expert consensus on the treatment of postinfectious olfactory dysfunction

Respiratory tract viruses are the second leading cause of olfactory dysfunction. Between 2019 to 2022, the world has been plagued by the problem of olfaction caused by the COVID-19. As we learn more about the impact of severe acute respiratory syndrome coronavirus 2（SARS-CoV-2）, with the recognition that olfactory dysfunction is a key symptom of this disease process, there is a greater need than ever for evidence-based management of postinfectious olfactory dysfunction（PIOD）. The Clinical Olfactory Working Group has proposed theconsensus on the roles of PIOD. This paper is the detailed interpretation of the consensus.

Substance P and Prokineticin-2 are overexpressed in olfactory neurons and play differential roles in persons with persistent post-COVID-19 olfactory dysfunction

Persistent olfactory dysfunction (OD) is one of the most complaining and worrying complications of long COVID-19 because of the potential long-term neurological consequences. While causes of OD in the acute phases of the SARS-CoV-2 infection have been figured out, reasons for persistent OD are still unclear.Here we investigated the activity of two inflammatory pathways tightly linked with olfaction pathophysiology, namely Substance P (SP) and Prokineticin-2 (PK2), directly within the olfactory neurons (ONs) of patients to understand mechanisms of persistent post-COVID-19 OD.ONs were collected by non-invasive brushing from ten patients with persistent post-COVID-19 OD and ten healthy controls. Gene expression levels of SP, Neurokinin receptor 1, Interleukin-1β (IL-1β), PK2, PK2 receptors type 1 and 2, and Prokineticin-2-long peptide were measured in ONs by Real Time-PCR in both the groups, and correlated with residual olfaction. Immunofluorescence staining was also performed to quantify SP and PK2 proteins.OD patients, compared to controls, exhibited increased levels of both SP and PK2 in ONs, the latter proportional to residual olfaction.This work provided unprecedented, preliminary evidence that both SP and PK2 pathways may have a role in persistent post-COVID-19 OD. Namely, if the sustained activation of SP, lasting months after infection’s resolution, might foster chronic inflammation and contribute to hyposmia, the PK2 expression could instead support the smell recovery.

The use of MRI in a tertiary smell and taste clinic: Lessons learned based on a retrospective analysis.

Olfactory dysfunction (OD) is a common but underreported problem that can significantly impact a patient's quality of life. OD is prevalent in over 5% of the adult population and can be broadly categorised into conductive and sensorineural causes. Magnetic Resonance Imaging (MRI) can form part of the diagnostic work up, although its exact role is often debated. The aim of this study was to evaluate the value of MRI in managing patients with OD. A retrospective analysis of the records of patients presenting to a national smell and taste clinic over a 5-year period was performed. Variables included demographics, endoscopic findings, final diagnosis, psychophysical smell test and imaging results. A total of 409 patients, with an age range of 10-93 years, underwent clinical assessment and smell testing, of which 172 patients (42%) had MRI scans. Imaging in younger age-groups was associated with a higher rate of positive findings, however identifiable causes for OD were recorded across the range. MRI provided both diagnostic and prognostic information in those with idiopathic, traumatic and congenital causes of OD. For example, MRI provided information on the extent or absence of gliosis in those with a head trauma history allowing further treatment and prognosis. We recommend the adjunct use of MRI in patients with a clear history and examination findings of head injury, congenital cases and in apparent idiopathic cases. MRI should be requested to compliment clinical findings with a view to aiding decision-making on treatment and prognosis independent of patient's age.

Olfactory system measurements in COVID-19: a systematic review and meta-analysis.

PurposeThe neurotropism of SARS-CoV-2 and the consequential damage to the olfactory system have been proposed as one of the possible underlying causes of olfactory dysfunction in COVID-19. We aimed to aggregate the results of the studies which reported imaging of the olfactory system of patients with COVID-19 versus controls.MethodsPubMed and EMBASE were searched to identify relevant literature reporting the structural imaging characteristics of the olfactory bulb (OB), olfactory cleft, olfactory sulcus (OS), or olfactory tract in COVID-19 patients. Hedge’s g and weighted mean difference were used as a measure of effect size. Quality assessment, subgroup analyses, meta-regression, and sensitivity analysis were also conducted.ResultsTen studies were included in the qualitative synthesis, out of which seven studies with 183 cases with COVID-19 and 308 controls without COVID-19 were enrolled in the quantitative synthesis. No significant differences were detected in analyses of right OB volume and left OB volume. Likewise, right OS depth and left OS depth were also not significantly different in COVID-19 cases compared to non-COVID-19 controls. Also, we performed subgroup analysis, meta-regression, and sensitivity analysis to investigate the potential effect of confounding moderators.ConclusionThe findings of this review did not confirm alterations in structural imaging of the olfactory system, including OB volume and OS depth by Covid-19 which is consistent with the results of recent histopathological evaluations.Supplementary InformationThe online version contains supplementary material available at 10.1007/s00234-022-03014-8.

Analysis of clinical characteristics in the patient with olfactory disorders

Objective:To analyze the etiology and clinical features of patients with olfactory disorders （OD） , and to explore the importance of gustatory testing in patients with OD. Methods:Clinical data of 335 consecutive patients with OD who seek medical consultation in the smell and taste center from the year 2015 to 2021 was retrospectively analyzed. The clinical characteristics of patients with OD were analyzed thorough a structured interview of medical history, otolaryngologic examinations, olfactory tests（Sniffin' Sticks test） and gustatory function test（whole-mouth taste test）. SPSS 17.0 software was used to analyze the clinical characteristics of patients with OD and related factors which have effect on gustatory function. Results:Among the patients， 36.4% of them caused by head trauma, 22.1% for upper respiratory tract infection（URTI）, 15.5% for rhinosinusitis diseases（RSD）, 11.9% for idiopathic, 9.6% for congenital anosmia, and 4.5% for other causes, respectively. The features were different in patients with different kinds of OD: most patients with head trauma were anosmic（χ²=27.958, P<0.001）, and no difference was found in gender and age（P>0.05 for both）; most patients with URTI were anosmic（χ²=21.568, P<0.001）, and female patients were more than male（χ²=5.898, P<0.05）, elder patients were more than younger（χ²=12.963, P<0.001）; most patients with RSD were anosmic（χ²=12.106, P<0.05）, and male patients were more than female（χ²=4.655, P<0.05）; elder patients were more than younger for idiopathic OD（χ²=5.284, P<0.05）, but no sex difference was found（P>0.05）; patients with congenital anosmia were all lost their smell since they were born, and no sex difference was found in the disease（P>0.05）. Fifty-seven of 146（39%） patients whose gustation was assessed had gustatory dysfunction. Gustatory function was significantly associated with the causes of OD（r=0.368, P<0.05）, but not related to olfactory function, age and sex（P>0.05 for all）. Conclusion:The leading causes of olfactory dysfunction were head trauma, URTI, RSD, and idiopathic causes. Each of OD had its own distinct clinical features. Gustatory dysfunction were common in patients with OD, and gustatory function was related to the causes of OD. High priority should be given to gustatory function evaluation for the patients with OD.

Clinical features of olfactory dysfunction in elderly patients

ObjectiveThis study aimed to investigate the causes of olfactory dysfunction (OD) and to discuss the benefits of understanding the characteristics of OD in elderly patients. MethodsA total of 4300 patients with OD who were treated at our hospital between January 1996 and December 2020 were retrospectively analyzed. There were 1833 men and 2467 women, with ages ranging from 4 to 95 years. The patients were divided into two groups: younger (less than 65 years old, n = 2947) and elderly (65 years old or more, n = 1353) groups. Causative diseases were chronic rhinosinusitis (CRS), post-viral (PV), post-traumatic (PT), central nervous system dysfunction (CNS), peripheral nervous system dysfunction (PNS), congenital, psychogenic, and unknown. Visual analogue scale (VAS) and olfactory detection and recognition thresholds using the T&T olfaction test were used to evaluate olfaction. The mean detection and recognition thresholds, as well as the deviation difference (the difference between the mean detection and recognition thresholds) were compared by causative disease. ResultsThe causative diseases in elderly group were CRS (32%), PV (28%), PT (3%), CNS (2%), and PNS (4%). OD of unknown cause was significantly more in elderly (30%) than in younger patients (12%). Olfactory detection and recognition thresholds in elderly group were significantly worse than in younger group (p < 0.05). The olfactory detection and recognition thresholds were not any significant differences between patients with OD of unknown cause and those with CNS. ConclusionOD of unknown cause was predominantly observed in elderly group. The olfactory acuity of OD of unknown cause was similar to CNS OD. These findings suggest the importance of continuous follow-up due to the potential of neurodegenerative diseases in elderly OD patients.

Assessment of olfactory fluctuations in a clinical context

PurposeThe aim of the study was to investigate whether olfactory fluctuations (OF) are pronounced in patients with sinonasal olfactory dysfunction (OD).MethodsThe retrospective investigation included patients aged 18 years or older, who consulted a tertiary referral center for olfactory loss. Patients with normal smell function were excluded. Patients answered a structured questionnaire about their olfactory symptoms, with specific questions related to the presence of OF and its average frequency, amplitude, duration, time since most recent OF, and associated symptoms of self-reported OF. Patients also underwent clinical evaluation including a structured medical history and physical examination including nasal endoscopy. In addition, we assessed orthonasal olfactory function using Sniffin’ Sticks, and gustatory function using “taste sprays”.ResultsParticipants included 131 men and 205 women (n = 336), aged 18 to 86 years (mean 50, SD 16). Patient-reported fluctuations occurred most frequently in sinonasal (38%), idiopathic (29%), and postviral (29%) OD. Amplitude of OF was highest in postviral OD (p = 0.009). Average frequency, duration, and the time since the most recent fluctuation were not significantly different between groups (all p’s > 0.42). Odor discrimination (p = 0.002) and identification (p = 0.017) scores were higher among those individuals with OF.ConclusionAmplitude of OF may help distinguish postviral from other causes of OD, especially in patients presenting with equivocal symptoms of sinonasal disease.

Transient modifications of the olfactory bulb on MR follow-up of COVID-19 patients with related olfactory dysfunction

Background: Olfactory dysfunction (OD) has been reported with a high prevalence on mild to moderate COVID-19 patients. Previous reports suggest that volume and signal intensity of olfactory bulbs (OB) have been reported as abnormal on acute phase of COVID-19 anosmia, but a prospective MRI and clinical follow-up study of COVID-19 patients presenting with OD was missing, aiming at understanding the modification of OB during patients'follow-up.Methods: A prospective multicenter study was conducted including 11 COVID-19 patients with OD. Patients underwent MRI and psychophysical olfactory assessments at baseline and 6-month post-COVID-19. T2 FLAIR-Signal intensity ratio (SIR) was measured between the average signal of the OB and the average signal of white matter. OB volumes and obstruction of olfactory clefts (OC) were evaluated at both evaluation times.Results: The psychophysical evaluations demonstrated a 6-month recovery in 10/11 patients (90.9%). The mean values of OB-SIR significantly decreased from baseline (1.66±0.24) to 6-month follow-up (1.35±0.27), reporting a mean variation of -17.82±15.20 % (p<0.001).The mean values of OB volumes significantly decreased from baseline (49.22±10.46 mm3) to 6-month follow-up (43.70±9.88 mm3), (p=0.006).Conclusion: Patients with demonstrated anosmia reported abnormalities in OB imaging that may be objectively evaluated with the measurement of SIR and OB volumes. SIR and OB volumes significantly normalized when patient recovered smell. This supports the underlying mechanism of a transient inflammation of the OB as a cause of Olfactory Dysfunction in COVID-19 patients.

Chronic Rhinosinusitis and COVID-19

The COVID-19 pandemic has raised awareness about olfactory dysfunction, although a loss of smell was present in the general population before COVID-19. Chronic rhinosinusitis (CRS) is a common upper airway chronic inflammatory disease that is also one of the most common causes of olfactory dysfunction. It can be classified into different phenotypes (ie, with and without nasal polyps) and endotypes (ie, type 2 and non–type 2 inflammation). However, scientific information regarding CRS within the context of COVID-19 is still scarce. This review focuses on (1) the potential effects of severe acute respiratory syndrome coronavirus 2 infection on CRS symptoms, including a loss of smell, and comorbidities; (2) the pathophysiologic mechanisms involved in the olfactory dysfunction; (3) CRS diagnosis in the context of COVID-19, including telemedicine; (4) the protective hypothesis of CRS in COVID-19; and (5) the efficacy and safety of therapeutic options for CRS within the context of COVID-19.

The Role of Social Media in Improving Patient Recruitment for Research Studies on Persistent Post-Infectious Olfactory Dysfunction.

Background and Objectives: Since the COVID-19 pandemic, the number of cases of post-infectious olfactory dysfunction (PIOD) has substantially increased. Despite a good recovery rate, olfactory dysfunction (OD) becomes persistent in up to 15% of cases and further research is needed to find new treatment modalities for those patients who have not improved on currently available treatments. Social media has emerged as a potential avenue for patient recruitment, but its role in recruiting patients with smell dysfunction remains unexplored. We conducted a survey using the AbScent Facebook page to evaluate the feasibility of using this platform for future studies on smell dysfunction. Materials and Methods: Between 26 October and 4 November 2021, we conducted an online survey to evaluate propensity of patients with PIOD who would be willing to participate in research studies on smell dysfunction. Results: Sixty-five subjects were surveyed with a response rate of 90.7%. The median visual analogue scale (VAS) for sense of smell was 0 at infection and 2 at survey completion. The median length of OD was 1.6 years, and the main cause of OD was SARS-CoV-2 (57.6%). Parosmia was reported in 41 subjects (69.5%) whilst phantosmia in 22 (37.3%). The median length of olfactory training (OT) was 6 months but subjectively effective in 15 subjects (25.4%). Twenty-seven subjects (45.8%) tried other medications to improve olfaction, but only 6 participants (22.2%) reported an improvement. All subjects expressed their propensity to participate in future studies with most of them (38; 64.4%) willing to be enrolled either in medical and surgical studies or to be part of a randomised study design (11; 18.6%). Conclusions: Using the AbScent Facebook platform we successfully selected a population of subjects with persistent and severe OD that have failed to improve on available treatments and are willing to participate in further clinical trials.

The Shape of the Olfactory Bulb Predicts Olfactory Function

The olfactory bulb (OB) plays a key role in the processing of olfactory information. A large body of research has shown that OB volumes correlate with olfactory function, which provides diagnostic and prognostic information in olfactory dysfunction. Still, the potential value of the OB shape remains unclear. Based on our clinical experience we hypothesized that the shape of the OB predicts olfactory function, and that it is linked to olfactory loss, age, and gender. The aim of this study was to produce a classification of OB shape in the human brain, scalable to clinical and research applications. Results from patients with the five most frequent causes of olfactory dysfunction (n = 192) as well as age/gender-matched healthy controls (n = 77) were included. Olfactory function was examined in great detail using the extended “Sniffin’ Sticks” test. A high-resolution structural T2-weighted MRI scan was obtained for all. The planimetric contours (surface in mm2) of OB were delineated manually, and then all surfaces were added and multiplied to obtain the OB volume in mm3. OB shapes were outlined manually and characterized on a selected slice through the posterior coronal plane tangential to the eyeballs. We looked at OB shapes in terms of convexity and defined two patterns/seven categories based on OB contours: convex (olive, circle, and plano-convex) and non-convex (banana, irregular, plane, and scattered). Categorization of OB shapes is possible with a substantial inter-rater agreement (Cohen’s Kappa = 0.73). Our results suggested that non-convex OB patterns were significantly more often observed in patients than in controls. OB shapes were correlated with olfactory function in the whole group, independent of age, gender, and OB volume. OB shapes seemed to change with age in healthy subjects. Importantly, the results indicated that OB shapes were associated with certain causes of olfactory disorders, i.e., an irregular OB shape was significantly more often observed in post-traumatic olfactory loss. Our study provides evidence that the shape of the OB can be used as a biomarker for olfactory dysfunction.

Relationship between olfactory and cognitive function in asthma

Poor asthma control or asthma exacerbation can cause hypoxia, which may be associated with cognitive impairment. 1 Caldera-Alvarado G Khan DA Defina LF Pieper A Brown ES Relationship between asthma and cognition: the Cooper Center Longitudinal Study. Allergy. 2013; 68: 545-548 Crossref PubMed Scopus (35) Google Scholar ,2 Irani F Barbone JM Beausoleil J Gerald L Is asthma associated with cognitive impairments? A meta-analytic review. J Clin Exp Neuropsychol. 2017; 39: 965-978 Crossref PubMed Scopus (39) Google Scholar Chronic rhinosinusitis (CRS) and allergic rhinitis, typically accompanied by asthma, are the main causes of olfactory dysfunction. 3 Mullol J Mariño-Sánchez F Valls M Alobid I Marin C The sense of smell in chronic rhinosinusitis. J Allergy Clin Immunol. 2020; 145: 773-776 Abstract Full Text Full Text PDF PubMed Scopus (26) Google Scholar We investigated the association between olfactory 4 Rhyo HI Bae WY Nam YH Association between olfactory function and asthma in adults. J Asthma Allergy. 2021; 14: 309-316 Crossref PubMed Scopus (3) Google Scholar and cognitive function 5 Rhyou HI Nam YH Association between cognitive function and asthma in adults. Ann Allergy Asthma Immunol. 2021; 126: 69-74 Abstract Full Text Full Text PDF PubMed Scopus (6) Google Scholar in patients with asthma and found that a decrease in olfactory and cognitive functions was typically observed among patients with asthma. In addition, an association between olfactory dysfunction and cognitive impairment has been found in recent studies. 6 Dintica CS Marseglia A Rizzuto D et al. Impaired olfaction is associated with cognitive decline and neurodegeneration in the brain. Neurology. 2019; 92: e700-e709 Crossref PubMed Scopus (61) Google Scholar ,7 Roberts RO Christianson TJH Kremers WK et al. Association between olfactory dysfunction and amnestic mild cognitive impairment and Alzheimer disease dementia. JAMA Neurol. 2016; 73: 93-101 Crossref PubMed Scopus (204) Google Scholar However, no study has evaluated the association between olfactory and cognitive functions in patients with asthma thus far. We hypothesized that olfactory and cognitive functions would be related to each other in patients with asthma, and they also might be associated with asthma control. Therefore, we aimed to evaluate this association in patients with asthma.

Analysis of Steroid Effect in Patients with Olfactory Dysfunction

Background and Objectives Olfaction plays an important role on sensing and discriminating smell and taste. The number of patients visiting outpatient department for treatment of olfactory dysfunction is increasing along with the change in patients’ perception about the importance of olfactory function.Subjects and Method Patients with olfactory dysfunction, who visited the hospital from 2010 to 2018, were included in this study. The medical records were reviewed focusing on the Korean Version of Sniffin’ Stick, the CT finding of olfactory cleft or signs of sinusitis, and the effect of oral steroids. Postviral olfactory disorder (PVOD) patients and chronic rhinosinusitis (CRS) patients were treated by oral steroid, starting on prednisolon (Solondo Tab&lt;sup&gt;®&lt;/sup&gt;, YuHan Corp.; 40 mg per day) and tapered for 2 weeks.Results There were 13 cases where patients’ sense of smell was improved only for a short period of time after taking steroids but worsened thereafter. They showed improvement of olfactory function every time they took steroids. We defined this group as “steroid dependent olfactory dysfunction.”Conclusion It is necessary to understand the physiology and molecular biologic mechanisms behind the causes of olfactory dysfunction in order to establish the diagnostic criteria and treatment strategy. Steroid dependent olfactory dysfunction also needs more investigation.

Olfactory rehabilitation and olfactory bulb volume changes in patients after total laryngectomy: a prospective randomized study

IntroductionAfter total laryngectomy, decreased olfactory function and olfactory bulb volume shrinkage have been reported to occur due to olfactory deprivation caused by nasal airflow interruption. There is evidence that the olfactory system can be modulated by repeated exposure to odors in a procedure called olfactory training. However, it is not known whether any recovery of the lost olfactory bulb volume is possible by eliminating olfactory deprivation via olfactory rehabilitation long after laryngectomy. ObjectiveThis study examined the recovery of olfactory function and the change in olfactory bulb volume via long-term olfactory rehabilitation after total laryngectomy. MethodsPossible causes of olfactory dysfunction in the study participants were evaluated by collecting detailed anamnesis. As olfactory tests, orthonasal butanol threshold and odor discrimination tests were performed. Three-dimensional olfactory bulb volumes were calculated using manual segmentation on T2-weighted coronal magnetic resonance images. In olfactory rehabilitation, four different odors were applied to all patients orthonasally, using a larynx bypass technique for 30 min per day for 6 months. Olfactory tests were performed before the rehabilitation and after 6 months of rehabilitation, and olfactory bulb volume measurements were performed using magnetic resonance images. ResultsEleven patients diagnosed with advanced laryngeal cancer who underwent total laryngectomy and postoperative radiotherapy with a follow-up of 5–10 years were included in the study. All patients were male, and the mean age was 58.18 ± 4.17 years. In total laryngectomized patients, the olfactory bulb volumes measured on magnetic resonance images were 42.25 ± 12.8 mm3 before and 55.5 ± 11.22 mm3 after rehabilitation, and this increase was highly significant. Olfactory test scores were 2.3 ± 1.27 before and 4.39 ± 0.86 after rehabilitation, and this increase was also highly significant. ConclusionAs a result of the olfactory rehabilitation applied by providing orthonasal air flow, the olfactory function lost after total laryngectomy was improved considerably, and the olfactory bulb volume was significantly increased. The increase in olfactory bulb volume in total laryngectomy patients via olfactory rehabilitation to eliminate olfactory deprivation due to nasal airflow interruption was demonstrated for the first time in this prospective longitudinal study.

Factors associated with relevant olfactory recovery after olfactory training: a retrospective study including 601 participants.

Olfactory training (OT) represents a therapeutic option for multiple etiologies of olfactory dysfunction (OD) that also benefits normosmic subjects. In this retrospective study, we report the effectiveness of OT and factors associated with relevant changes in olfactory function (OF) in large groups of normosmic participants and patients with OD, including a control group that performed no training. This was a retrospective pooled analysis including 2 treatment cohorts of 8 previously published studies. Adult participants that either presented with the major complaint of quantitative OD or normosmic volunteers were recruited at various ENT clinics and received OT or no training. The outcome was based on changes in objective olfactory test scores after OT. A total of 601 patients with OD or normosmic subjects were included. OT was more effective compared to no training. No interaction was found between OT and OF. In multivariate analysis, higher baseline OF (adjusted odds ratio, aOR, 0.93) and posttraumatic (aOR, 0.29) or idiopathic OD (aOR, 0.18) compared to postinfectious causes were significantly associated with lower odds of relevant improvements in patients with OD receiving OT. Subgroup analysis of normosmic participants receiving OT further revealed a significant association of lower age and baseline olfactory function with improvements of overall OF. This study demonstrated that OT was more effective than no training in patients with various causes of OD. Additionally, baseline olfactory performance and etiology of OD were identified as important factors associated with relevant improvements after OT.