Anosmia-A Clinical Review

Impaired odor recognition memory in Parkinson's disease linked to absent functional hippocampal asymmetry

Odor recognition memory (ORM) combines olfaction and episodic memory, both linked to dementia and impaired in Parkinson's Disease (PD). Measuring ORM may indicate early PD dementia and aid in selecting device-aided Parkinson therapy. This study investigates ORM capacity and hippocampal dynamic functional connectivity in PD. Thirty-one PD participants and 31 healthy controls (HC) underwent functional MRI during an ORM task. Co-activation pattern analysis identified active hippocampal networks. The PD group showed impaired ORM and a sequence of four activated hippocampal networks. The fourth network, involving the dorsal Attention Network (dAN), had fewer and shorter expressions during correct ORM responses in PD compared with HC. Hippocampal functional asymmetry was observed in HC but not in PD. These findings suggest that impaired ORM in PD is linked to reduced hippocampal functional asymmetry. Future research should explore differences in functional dynamics of odor memory-related brain regions in PD patients with and without cognitive decline.

Devices for the electrical stimulation of the olfactory system: A review

The loss of olfactory function has a profound impact on quality of life, affecting not only sensory perception but also memory, emotion, and overall well-being. Despite this, advancements in olfactory prostheses have lagged significantly behind those made for vision and hearing restoration. This review offers a comprehensive analysis of the current state of devices for electrical stimulation of the olfactory system. We begin by providing an overview of the olfactory system's structure and function, emphasizing the neural pathways involved in smell perception. Following this, we explore the key challenges associated with chronic implantation and electrical stimulation, material biocompatibility, inflammation risks, and ensuring long-term functionality and durability. A detailed analysis of existing neural stimulation devices-including ECoG, intracortical, and depth electrodes-is presented, assessing their potential for application in olfactory stimulation. We also discuss the limitations and pitfalls of current approaches and explore new emerging technologies aimed at overcoming these obstacles. A comprehensive literature review about the olfactory system electrical stimulation is reported, and results are analyzed to identify the most promising routes. Finally, the review highlights emerging technologies, ongoing research, and the ethical considerations associated with olfactory implants, along with future directions for developing more effective, safe, and durable solutions to restore the sense of smell for individuals with olfactory disorders.

Chemosensory Impairments and Their Impact on Nutrition in Parkinson's Disease: A Narrative Literature Review

Parkinson's disease (PD) is a neurological disorder characterized by heterogeneous symptomatology, in which the classical motor features of Parkinsonism are associated with clinically significant non-motor symptoms. Olfactory alteration, as a manifestation of PD's premotor or prodromal phase, is well known. These impairments can lead to malnutrition, decreased appetite, and depression, thereby worsening patients' quality of life. However, only a few studies clarify the mechanisms, characteristics, and clinical diagnostic and therapeutic implications of impaired taste perception. Moreover, unlike most motor features of PD, non-motor symptoms often have limited treatment options or responses. The purpose of this review is to collate and describe all relevant studies on taste and smell alterations in patients with PD and how these alterations could affect nutritional status. Our search aimed to identify English-language research articles and reviews published in peer-reviewed journals over the past two decades (2004-2024), while also including older foundational studies when relevant. Several studies show that hyposmia in PD worsens over time, potentially linked to structural changes in the brain's basal ganglia and piriform cortex. Severe hyposmia is also associated with a higher risk of dementia in PD patients and can negatively influence quality of life, affecting social interactions and nutrition. Regarding taste perception, recent studies have suggested that hypogeusia may occur even in the prodromal stage of PD, such as in patients with REM sleep disorder, although the exact mechanisms remain unclear. Additionally, research has explored the role of bitter taste receptors and their possible involvement in inflammation and α-synuclein misfolding, suggesting a link between taste dysfunction and immune system changes in PD. Attention was then focused on the gut microbiota's link to the central nervous system and its contribution to gustatory dysfunctions, as well as how the nasal microbiome influences PD progression by altering the olfactory system. Nowadays, the primary role of a correct diet in the overall treatment of PD patients is becoming increasingly important for practitioners. Diet should be included among the available aids to counteract some aspects of the pathology itself. For all these reasons, it is also crucial to determine whether these chemosensory impairments could serve as disease markers, helping to better understand the underlying mechanisms of the disease.

Olfactory function in Wilson's disease-systematic literature review

In Wilson's disease (WD) improper copper metabolism results in copper accumulation in various organs, mainly brain and liver. The sense of smell is today one of the focuses of interest in aging and neurodegenerative diseases research. However, in WD olfactory function (OF) is still poorly investigated. Our aim was to perform a systematic review of the studies evaluating OF in WD. We searched PubMed for original papers evaluating olfactory function in WD and retrieved five articles. Additionally, one article was identified while viewing the references lists of the included studies. Finally, we included 6 studies. The number of patients ranged from 12 to 68 (altogether 222 WD patients) and their clinical characteristics were variable. Differences in methodology (mainly various tests used for OF evaluation) made it impossible to meta-analyze the data. OF was worse in WD than in controls in all studies. In 3 studies OF was impaired significantly in neurologic phenotype vs hepatic, which was not confirmed in 2 other studies. Correlation between OF and presence of brain lesions in magnetic resonance imaging was inconsistent across two studies. Only one study assessed brain regions involved in the olfactory tract by evaluating olfactory bulb volume. There was no effect of WD treatment, including its type and duration on OF (4 studies). One study additionally assessed taste which was preserved in WD. Although OF was found to be abnormal in WD, this area remains insufficiently explored. Further studies conducted on larger cohorts, with a focus on olfactory tract damage, is essential.

Scent of COVID-19: Whole-Genome Sequencing Analysis Reveals the Role of ACE2, IFI44, and NDUFAF4 in Long-Lasting Olfactory Dysfunction

COVID-19-related persistent olfactory dysfunction (OD) presents remarkable interindividual differences, and little is known about the host genetic factors that are involved in its etiopathogenesis. The goal of this study was to explore the genetic factors underpinning COVID-19-related OD through the analysis of Whole Genome Sequencing data of 153 affected subjects, focusing on genes involved in antiviral response regulation. An innovative approach was developed, namely the assessment of the association between a "gene score", defined as the ratio of the number of homozygous alternative variants within the gene to its length, and participants' olfactory function. The analysis highlighted how an increased gene score in the ACE2 gene is associated with a worse olfactory performance, while an increased gene score in the IFI44 and NDUFAF4 genes is associated with a better olfactory function. Considering the physiological role of the proteins encoded by these genes, it can be hypothesized that a reduced expression of ACE2 may be associated with a protracted and severe inflammatory response in the olfactory epithelium, thus worsening patients' smell abilities. Conversely, an increased gene score in IFI44 and NDUFAF4 might be associated with a decreased inflammatory response, thus correlating with a better olfactory performance. Overall, this study identified new host genetic factors that may play a pivotal role in determining COVID-19-related OD heterogeneity, possibly enabling more personalized and effective clinical management for affected individuals.

Different Modalities in the Management of Post-COVID-19 Olfactory Dysfunction

SARS-CoV-2 infection may lead to olfactory dysfunctions affecting patients' quality of life. Despite various ongoing studies, solid evidence supporting therapies, especially for COVID-19-related olfactory dysfunction, remains scarce. To assess nasal steroid, nasal vitamin A, and intranasal theophylline as treatment options for post-COVID-19 olfactory dysfunction. This is a multi-center retrospective case-controlled study of 120 cases with post-COVID-19 olfactory dysfunction (hyposmia or anosmia) at Benha University Hospitals, Egypt, and Dallah Hospital, Riyadh City, Kingdom of Saudi Arabia (KSA) between January 2020 and December 2022. 43.3% males and 56.6% females with median age was 38.5 years. Nasal steroid, nasal vitamin A, and intranasal theophylline had a significantly reduced time for complete smell recovery (25.7 ± 9.20 days, 24.8 ± 6.67 days. 23.5 ± 7.13 days Respectively) in comparison to the control group (olfactory training alone) (28.97 ± 4.29 days) (P = 0.02*). No significant correlation between age, gender, severity, duration of COVID-19 illness, and obesity with anosmia/hyposmia duration and smell scores, however a highly significant negative correlation between diabetes, hypertension, smoking, and asthma complete smell recovery within four weeks of treatment (P-Value < 0.001***). A combination of topical mometasone furoate, vitamin A, or intranasal theophylline with olfactory training can shorten post-COVID-19 olfactory dysfunction. However, no significant smell score improvement was found when compared to olfactory training alone after four weeks. Diabetes, hypertension, smoking, and asthma adversely affect complete smell recovery within four weeks of treatment.

Periodontitis is associated with impaired olfactory function: A clinical study

AIM

To explore the association between periodontitis and olfactory disorders.

METHODS

Clinical data were collected from 198 individuals between the ages of 18 and 60 years living in Denmark. The exposure was periodontitis, and the outcome was olfactory function (Threshold, Discrimination, Identification - TDI score), both measured clinically. Covariates included sex, age, education level, income, usage of nasal spray, tongue coating, halitosis, xerostomia, smoking, and history of COVID-19. Structural equation modeling was used to estimate the association between periodontitis and olfactory function. Periodontitis was defined using the AAP/EFP classification and dichotomized into "no" (healthy subjects) and "yes" (Stages I, II, and III). Olfactory function was treated as a one-factor latent variable, including the different olfactory scores. In addition, extra models were performed considering each olfactory component as a separate outcome and the TDI Global Score.

RESULTS

The results showed that periodontitis was associated with a lower olfactory function [standardized coefficient (SC) -0.264, 95% CI -0.401, -0.118]. Additionally, periodontitis was also associated with a lower olfactory Threshold (odorant concentration required for detection) (SC -0.207, 95% CI -0.325, -0.089), Discrimination (ability to discriminate between odorants) (SC -0.149, 95% CI -0.270, -0.027), Identification (ability to identify odorants) scores (SC -0.161, 95% CI -0.277, -0.045), and TDI Global Score (SC -0.234, 95% CI -0.370, -0.099).

CONCLUSIONS

This study suggests that periodontitis is associated with olfactory impairment.

Effects of Mepolizumab in the treatment of type 2 CRSwNP: a real-life clinical study

PURPOSE

Mepolizumab was recently approved for treating Chronic Rhinosinusitis with Nasal Polyps (CRSwNP) unresponsive to standard treatment or recurring after endoscopic sinus surgery (ESS). To date, few studies have assessed Mepolizumab's efficacy in severe type-2 CRSwNP. Our study aimed to analyze sinonasal outcomes in type-2 CRSwNP patients treated with 100 mg Mepolizumab administered subcutaneously every four weeks.

METHODS

We conducted a retrospective study of patients with severe, recalcitrant CRSwNP treated with Mepolizumab. Demographic and clinical characteristics were collected, including age, sex, and comorbidities such as asthma, nonsteroidal anti-inflammatory drug-exacerbated respiratory disease (NERD), and allergic rhinitis (AR), as well as the number of previous ESS procedures and the interval since the last one. Patients were evaluated at baseline and after one year for blood eosinophil count, nasal polyp score (NPS), modified Lund-Kennedy score (mLKS), olfactory function (using a VAS scale and a 16-item Sniffin' identification test), SNOT-22, and sinus opacification on CT scans. The need for rescue ESS or systemic corticosteroids (SCS), response to treatment, and side effects were also recorded.

RESULTS

Data from 27 patients were collected. After one year, all scores showed significant improvement. NERD was the only factor associated with a less favorable improvement in olfactory function. There were no side effects reported, although 2 patients discontinued Mepolizumab as they were considered "non-responders."

CONCLUSIONS

Mepolizumab is safe and effective in reducing the clinical, endoscopic, and radiological burden of disease, as well as in decreasing the need for salvage ESS or systemic steroids.

Past, Present, and Future of Human Chemical Communication Research

Although chemical signaling is an essential mode of communication in most vertebrates, it has long been viewed as having negligible effects in humans. However, a growing body of evidence shows that the sense of smell affects human behavior in social contexts ranging from affiliation and parenting to disease avoidance and social threat. This article aims to (a) introduce research on human chemical communication in the historical context of the behavioral sciences; (b) provide a balanced overview of recent advances that describe individual differences in the emission of semiochemicals and the neural mechanisms underpinning their perception, that together demonstrate communicative function; and (c) propose directions for future research toward unraveling the molecular principles involved and understanding the variability in the generation, transmission, and reception of chemical signals in increasingly ecologically valid conditions. Achieving these goals will enable us to address some important societal challenges but are within reach only with the aid of genuinely interdisciplinary approaches.

Significant Underreporting of Preoperative Hyposmia in Patients Undergoing Endoscopic Skull Base Surgery: Discrepancies Between Subjective and Objective Measurements

Objective  The assessment of baseline olfactory function before endoscopic skull base surgery (ESBS) has been relatively limited compared with analysis before functional endoscopic sinus surgery (FESS). Our study addresses this knowledge gap, assessing preoperative olfactory function in ESBS and FESS and elucidating any differences. Study Design  We conducted a retrospective review of patients undergoing anterior ESBS or FESS at a single institution between 2021 and 2022. We included 171 patients and compared their reported and measured preoperative olfactory function using the Sino-Nasal Outcome Test questionnaire and the 40-item University of Pennsylvania Smell Identification Test. Results  Of the 171 patients included in this study, 30% of patients underwent ESBS and 70% underwent FESS. Of all patients, only 57% correctly reported their objective preoperative olfactory function. Of the 36 ESBS patients with measured preoperative hyposmia, only 31% correctly reported hyposmia, while 69% incorrectly reported normosmia. This distribution significantly differs ( p  < 0.0001) from the FESS subset (89 patients), with 64% correctly reporting hyposmia and 36% incorrectly reporting normosmia. Conclusion  Our analysis demonstrates higher than anticipated underreporting of preoperative hyposmia in patients undergoing ESBS as well as discrepancies between subjective and objective olfactory functions in the FESS population. The results highlight several gaps in knowledge regarding perioperative olfactory function that would be best examined with more thorough pre- and postoperative objective olfactory testing. This analysis demonstrates significant prognostic uncertainty for patients and providers and creates significant medicolegal uncertainty regarding the appropriate attribution of postoperative olfactory loss in cases without objective preoperative testing.

Intranasal Trigeminal Function in Aging Adults

BACKGROUND

Intranasal trigeminal function is important in detecting environmental stimuli. The impact of age-associated chemosensory dysfunction upon taste and olfaction is well described, but an understanding of trigeminal loss (chemesthesis) is lacking.

OBJECTIVE

The goal of this study was to characterize trigeminal function in a cohort of older adults and explore potential impacts.

METHODS

Twenty-eight participants over 50 years of age were recruited from the community as part of an aging cohort study. This nested cohort completed chemosensory questionnaires, patient-reported outcome measures (PROMs), and psychophysical testing for taste (taste strips), olfaction (Sniffin' Sticks), and trigeminal function (eucalyptol lateralization). Data were analyzed for associations between trigeminal function, olfactory, and taste psychophysical performance, patient-reported metrics, and demographic risk factors.

RESULTS

Patient-reported trigeminal impairment is less severe than other chemosensory loss, with mean visual analog scores (VAS, rated 0-100 from least to most severe) for smell (32.9 ± 34.2), taste (20.6 ± 28.4), and trigeminal sensation (9.5 ± 12.8). Despite low VAS scores, psychophysical trigeminal dysfunction was present in 10 (35.7%) subjects. Psychophysical olfactory and taste dysfunction were present in 16 (57.1%) and eight (28.6%) participants respectively. Hypercholesterolemia was associated with psychophysical trigeminal dysfunction (mean lateralization performance in hypercholesterolemia 57.7% ± 17.1 vs. 74.1% ± 10.4, p = .008).

CONCLUSION

Intranasal trigeminal impairment is present in nearly one-third of aging adults when assessed by psychophysical methods but is under-recognized. Hyperlipidemia may be associated with trigeminal impairment. Future inquiries should better characterize these findings in larger and prospective cohorts.

Impaired olfactory system in metabolic imbalance-related neuropathology

Olfactory dysfunction, influenced by factors such as aging and environmental stress, is linked to various neurological disorders. The olfactory bulb's connections to brain areas like the hypothalamus, piriform cortex, entorhinal cortex, and limbic system make olfactory dysfunction a contributor to a range of neuropathological conditions. Recent research has underscored that olfactory deficits are prevalent in individuals with both metabolic syndrome and dementia. These systemic metabolic alterations correlate with olfactory impairments, potentially affecting brain regions associated with the olfactory bulb. In cases of metabolic syndrome, phenomena such as insulin resistance and disrupted glucose metabolism may result in compromised olfactory function, leading to multiple neurological issues. This review synthesizes key findings on the interplay between metabolic-induced olfactory dysfunction and neuropathology. It emphasizes the critical role of olfactory assessment in diagnosing and managing neurological diseases related to metabolic syndrome.

Topical platelet-rich plasma as a possible treatment for olfactory dysfunction-A randomized controlled trial

BACKGROUND

Olfactory dysfunction (OD) affects many survivors of COVID-19. Prior studies have investigated the use of platelet-rich plasma (PRP) injections for OD. We describe the first randomized controlled trial investigating topical PRP for OD treatment and contribute to existing literature illustrating PRP as an emerging therapeutic.

METHODS

This is a single-blinded, randomized controlled trial conducted from July 2022 to December 2023. Adult patients with OD ≥6 months secondary to COVID-19 with Brief Smell Identification Test (BSIT) scores of ≤8/12 or SCENTinel odor intensity of ≤40/100 were included. Patients were randomized to three, monthly PRP or placebo-impregnated Surgifoam treatments into bilateral olfactory clefts. The BSIT, SCENTinel, and Questionnaire of Olfactory Disorders-Negative Statements (QOD-NS) were completed monthly through month 12.

RESULTS

Of 104 patients screened, 83 participated. No significant differences in age, OD duration, BSIT, SCENTinel, or QOD-NS scores were found between PRP (n = 42) and placebo (n = 41) patients at baseline. PRP patients experienced a statistically significant increase in BSIT scores from baseline at months 5‒9, 11, and 12, while placebo patients did not (p < 0.05). However, total BSIT scores were similar between the two groups throughout the study. Neither the SCENTinel odor intensity scores nor the change from baseline were significantly different between the treatment groups. At month 12, PRP patients experienced minor improvement in OD-related quality-of-life compared with placebo.

CONCLUSIONS

This study is the first to describe topical PRP as a safe, experimental treatment for OD in humans. PRP may impact odor identification in post-COVID-19 OD patients, although the lack of difference in total BSIT scores highlights the need for further study.

Receptors Involved in COVID-19-Related Anosmia: An Update on the Pathophysiology and the Mechanistic Aspects

Olfactory perception is an important physiological function for human well-being and health. Loss of olfaction, or anosmia, caused by viral infections such as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has received considerable attention, especially in persistent cases that take a long time to recover. This review discusses the integration of different components of the olfactory epithelium to serve as a structural and functional unit and explores how they are affected during viral infections, leading to the development of olfactory dysfunction. The review mainly focused on the role of receptors mediating the disruption of olfactory signal transduction pathways such as angiotensin converting enzyme 2 (ACE2), transmembrane protease serine type 2 (TMPRSS2), neuropilin 1 (NRP1), basigin (CD147), olfactory, transient receptor potential vanilloid 1 (TRPV1), purinergic, and interferon gamma receptors. Furthermore, the compromised function of the epithelial sodium channel (ENaC) induced by SARS-CoV-2 infection and its contribution to olfactory dysfunction are also discussed. Collectively, this review provides fundamental information about the many types of receptors that may modulate olfaction and participate in olfactory dysfunction. It will help to understand the underlying pathophysiology of virus-induced anosmia, which may help in finding and designing effective therapies targeting molecules involved in viral invasion and olfaction. To the best of our knowledge, this is the only review that covered all the receptors potentially involved in, or mediating, the disruption of olfactory signal transduction pathways during COVID-19 infection. This wide and complex spectrum of receptors that mediates the pathophysiology of olfactory dysfunction reflects the many ways in which anosmia can be therapeutically managed.

The current possibilities of diagnosing and therapies for olfactory disorders

INTRODUCTION

Olfactory disorders significantly affect individuals, diminishing their capacity to detect dangers, appreciate flavors, and engage socially. Despite their considerable impact on quality of life, these disorders often receive less attention compared to other sensory impairments. This review emphasizes the importance of olfactory function and explores both traditional and innovative diagnostic and therapeutic approaches.

AREAS COVERED

This review comprehensively covers the pathophysiology, diagnostic challenges, and treatment options for olfactory disorders. It delves into the nuances of different disorders, such as anosmia and parosmia, and discusses the array of diagnostic tools from traditional sniff tests to advanced imaging techniques. The review also evaluates therapeutic strategies, from pharmacological treatments to emerging therapies like electrical stimulation and regenerative medicine, highlighting recent advances in the field.

EXPERT OPINION

Current insights suggest a growing recognition of the significance of olfactory disorders, driven by recent pandemics and advances in diagnostic and therapeutic technologies. Future perspectives indicate a promising direction toward more personalized medicine approaches and enhanced regenerative therapies. Continuous research and improved clinical awareness are critical for evolving the management strategies of olfactory impairments, potentially leading to better patient outcomes and quality of life enhancements.

Olfactory-Related Adverse Events: An Analysis of the Food and Drug Administration Adverse Events Reporting System

OBJECTIVE

Olfactory dysfunction has gained considerable interest with its association to the coronavirus pandemic. Due to the limited literature on olfactory-related adverse events (ORAE) associated with medications, this study investigated ORAE reported in the Food and Drug Administration Adverse Event Reporting System (FAERS) to identify the most frequent medications associated with these reactions.

STUDY DESIGN

Cross-sectional analysis SETTING: FAERS database.

METHODS

The FAERS database was accessed to obtain ORAEs from 2012 to 2022. Disproportionality analysis was conducted by calculating the proportional reporting ratios (PRR) and reporting odds ratio (ROR) for anosmia, parosmia, hyposmia, and olfactory dysfunction. A PRR > 2 or ROR > 1 was significant. A multivariate logistical model was used to estimate adjusted ROR for gender and country of origin.

RESULTS

Our final study population consisted of 1111 cases with the following symptoms: anosmia (672), parosmia (364), hyposmia (71), and olfactory dysfunction (4). The most significant ROR signal scores were found for secukinumab (3.42; 95% confidence interval, CI [1.9, 4.01]) for anosmia, levofloxacin (8.86; 95% CI [2.83, 9.8]) for hyposmia, and pregabalin (6.88; 95% CI [2.23, 8.01]) for parosmia. No significant PRR signal scores were found for anosmia, but significant signals were found for citalopram hydrobromide (17.25; 95% CI [17.01, 17.49]) in hyposmia, and dimethyl fumarate (3.18; 95% CI [3.09, 3.27]) in parosmia. No valid PRR or ROR values were found for olfactory dysfunction. Multivariate analysis did not reveal statistically significant differences between genders for any symptoms, but individuals from non-US countries did exhibit statistically significant elevated risk of anosmia (1.3 (95% CI [1.01, 1.68]).

CONCLUSION

Pharmacovigilance studies provide an opportunity to evaluate the safety profile of medications regarding ORAE, particularly for those commonly prescribed for sinonasal symptoms. Findings from this study may function as a resource for prescribers and patients.

Remote olfactory assessment using the NIH Toolbox Odor Identification test and the brain health registry

BACKGROUND

Early identification of deficits in our ability to perceive odors is important as many normal (i.e., aging) and pathological (i.e., sinusitis, viral, neurodegeneration) processes can result in diminished olfactory function. To realistically enable population-level measurements of olfaction, validated olfaction tests must be capable of being administered outside the research laboratory and clinical setting.

AIM

The purpose of this study was to determine the feasibility of remotely testing olfactory performance using a test that was developed with funding from the National Institutes of Health as part of a ready-to-use, non-proprietary set of measurements useful for epidemiologic studies (NIH Toolbox Odor ID Test).

MATERIALS AND METHODS

Eligible participants older than 39 years and active (within 6 months) in the Brain Health Registry (BHR), an online cognitive assessment platform which connects participants with researchers, were recruited for this study. Interested participants were mailed the NIH Toolbox Odor ID Test along with instructions on accessing a website to record their responses. Data obtained from subjects who performed the test at home was compared to the normative data collected when the NIH Toolbox Odor ID Test was administered by a tester in a research setting and validated against the Smell Identification Test. The age-range and composition of the population ensured we had the ability to observe both age-related decline and gender-related deficits in olfactory ability, as shown in the experimental setting.

RESULTS

We observed that age-associated olfactory decline and gender-associated performance was comparable to performance on the administered test. Self-administration of this test showed the age-related loss in olfactory acuity, F(4, 1156)=14.564, p<.0001 as well as higher accuracy for women compared to men after controlling for participants' age, F(1, 1160) = 22.953, p <.0001. The effect size calculated as Hedge's g, was 0.41.

CONCLUSION

These results indicate that the NIH Toolbox Odor ID Test is an appropriate instrument for self-administered assessment of olfactory performance. The ability to self-administer an inexpensive olfactory test increases its utility for inclusion in longitudinal epidemiological studies and when in-person testing is not feasible.

Effectiveness of dupilumab versus endoscopic sinus surgery for the treatment of type-2 chronic rhinosinusitis with nasal polyps: a preliminary report

PURPOSE

Historically managed with intranasal corticosteroids (INCS) and endoscopic sinus surgery (ESS), type-2 Chronic RhinoSinusitis with Nasal Polyps (CRSwNP) treatment was revolutionized by the introduction of dupilumab but universally accepted guidelines are still lacking.

METHODS

Patients treated at our University Hospital for type-2 CRSwNP were enrolled. Demographic data were collected, as well as laboratory (eosinophils, total IgE), endoscopic [nasal polyps score (NPS), modified Lund-Kennedy score (mLKS)], radiological [Lund-Mackay score (LMS) at CT scan], SNOT-22, and olfactory [Sniffin' Sticks identification test (SSIT)] features. Patients were treated with dupilumab or ESS and re-evaluated after 3 and 12 months.

RESULTS

At 3 and 12 months, patients undergoing ESS achieved a higher reduction of NPS and mLKS, while patients receiving dupilumab experienced a higher improvement at SNOT-22 and SSIT with a greater positive variation in the prevalence of anosmia (- 57.7% vs - 42.9%) and normosmia (+ 37.8 vs + 28.5%). Mean mLKS and LMS were quite similar. Results were independent of clinical features known to contribute to CRSwNP severity, except for patients with ≥ 2 prior ESS who had a significantly lower smell improvement.

CONCLUSION

ESS and dupilumab were effective at reducing CRSwNP inflammatory burning. CRSwNP smell impairment cannot be attributed only to olfactory cleft obstruction and other mechanisms may be involved. Dupilumab acts systemically with poor correlation with NPS. As of today, dupilumab appears to be more suitable for elderly patients with anesthesiological contraindications and/or several previous surgeries, while ESS may represent the first-line choice in surgery-naive patients.

Reduced olfactory performance is associated with changed microbial diversity, oralization, and accumulation of dead biomaterial in the nasal olfactory area

The partial or complete loss of the sense of smell, which affects about 20% of the population, impairs the quality of life in many ways. Dysosmia and anosmia are mainly caused by aging, trauma, infections, or even neurodegenerative disease. Recently, the olfactory area-a site containing the olfactory receptor cells responsible for odor perception-was shown to harbor a complex microbiome that reflects the state of olfactory function. This initially observed correlation between microbiome composition and olfactory performance needed to be confirmed using a larger study cohort and additional analyses. A total of 120 participants (middle-aged, no neurodegenerative disease) were enrolled in the study to further analyze the microbial role in human olfactory function. Olfactory performance was assessed using the Sniffin' Stick battery, and participants were grouped accordingly (normosmia: n = 93, dysosmia: n = 27). The olfactory microbiome was analyzed by 16S rRNA gene amplicon sequencing and supplemented by metatranscriptomics in a subset (Nose 2.0). Propidium monoazide (PMA) treatment was performed to distinguish between intact and non-intact microbiome components. The gastrointestinal microbiome of these participants was also characterized by amplicon sequencing and metabolomics and then correlated with food intake. Our results confirm that normosmics and dysosmics indeed possess a distinguishable olfactory microbiome. Alpha diversity (i.e., richness) was significantly increased in dysosmics, reflected by an increase in the number of specific taxa (e.g., Rickettsia, Spiroplasma, and Brachybacterium). Lower olfactory performance was associated with microbial signatures from the oral cavity and periodontitis (Fusobacterium, Porphyromonas, and Selenomonas). However, PMA treatment revealed a higher accumulation of dead microbial material in dysosmic subjects. The gastrointestinal microbiome partially overlapped with the nasal microbiome but did not show substantial variation with respect to olfactory performance, although the diet of dysosmic individuals was shifted toward a higher meat intake. Dysosmia is associated with a higher burden of dead microbial material in the olfactory area, indicating an impaired clearance mechanism. As the microbial community of dysosmics (hyposmics and anosmics) appears to be influenced by the oral microbiome, further studies should investigate the microbial oral-nasal interplay in individuals with partial or complete olfactory loss.IMPORTANCEThe loss of the sense of smell is an incisive event that is becoming increasingly common in today's world due to infections such as COVID-19. Although this loss usually recovers a few weeks after infection, in some cases, it becomes permanent-why is yet to be answered. Since this condition often represents a psychological burden in the long term, there is a need for therapeutic approaches. However, treatment options are limited or even not existing. Understanding the role of the microbiome in the impairment of olfaction may enable the prediction of olfactory disorders and/or could serve as a possible target for therapeutic interventions.

Deprivation-Induced Plasticity in the Early Central Circuits of the Rodent Visual, Auditory, and Olfactory Systems

Activity-dependent neuronal plasticity is crucial for animals to adapt to dynamic sensory environments. Traditionally, it has been investigated using deprivation approaches in animal models primarily in sensory cortices. Nevertheless, emerging evidence emphasizes its significance in sensory organs and in subcortical regions where cranial nerves relay information to the brain. Additionally, critical questions started to arise. Do different sensory modalities share common cellular mechanisms for deprivation-induced plasticity at these central entry points? Does the deprivation duration correlate with specific plasticity mechanisms? This study systematically reviews and meta-analyzes research papers that investigated visual, auditory, or olfactory deprivation in rodents of both sexes. It examines the consequences of sensory deprivation in homologous regions at the first central synapse following cranial nerve transmission (vision - lateral geniculate nucleus and superior colliculus; audition - ventral and dorsal cochlear nucleus; olfaction - olfactory bulb). The systematic search yielded 91 papers (39 vision, 22 audition, 30 olfaction), revealing substantial heterogeneity in publication trends, experimental methods, measures of plasticity, and reporting across the sensory modalities. Despite these differences, commonalities emerged when correlating plasticity mechanisms with the duration of sensory deprivation. Short-term deprivation (up to 1 d) reduced activity and increased disinhibition, medium-term deprivation (1 d to a week) involved glial changes and synaptic remodeling, and long-term deprivation (over a week) primarily led to structural alterations. These findings underscore the importance of standardizing methodologies and reporting practices. Additionally, they highlight the value of cross-modal synthesis for understanding how the nervous system, including peripheral, precortical, and cortical areas, respond to and compensate for sensory inputs loss.

Validity and reliability of the Questionnaire of Olfactory Disorders for Italian-speaking patients with olfactory dysfunction

Objective

To translate and validate an Italian version of the Questionnaire of Olfactory Disorders (IT-QOD).

Materials and methods

This is a prospective, multicentre study that involved patients with olfactory dysfunction (OD). Both cases and controls underwent administration of the IT-QOD, Sino-Nasal Outcome Test-22 (SNOT-22) and psychophysical evaluation of orthonasal and retronasal olfactory function.

Results

The IT-QOD was administered to 96 patients and 38 controls. The Cronbach's alpha exceeded 0.90, indicating satisfactory internal consistency. The test-retest reliability was found to be high for both parosmia (rs = 0.944) and life quality (rs = 0.969). Patients with OD had significantly higher IT-QOD scores compared to healthy individuals (p < 0.001), indicating strong internal validity. The external validity was also satisfactory, as shown by the significant correlation with SNOT-22 (rs = -0.54) and the threshold, discrimination, and identification score (rs = -0.63).

Conclusions

The IT-QOD was demonstrated to be reliable and valid to assess the impact of OD on the quality of life of Italian-speaking patients.

In vitro modeling of cranial placode differentiation: Recent advances, challenges, and perspectives

Cranial placodes are transient ectodermal thickenings that contribute to a diverse array of organs in the vertebrate head. They develop from a common territory, the pre-placodal region that over time segregates along the antero-posterior axis into individual placodal domains: the adenohypophyseal, olfactory, lens, trigeminal, otic, and epibranchial placodes. These placodes terminally differentiate into the anterior pituitary, the lens, and contribute to sensory organs including the olfactory epithelium, and inner ear, as well as several cranial ganglia. To study cranial placodes and their derivatives and generate cells for therapeutic purposes, several groups have turned to in vitro derivation of placodal cells from human embryonic stem cells (hESCs) or induced pluripotent stem cells (hiPSCs). In this review, we summarize the signaling cues and mechanisms involved in cranial placode induction, specification, and differentiation in vivo, and discuss how this knowledge has informed protocols to derive cranial placodes in vitro. We also discuss the benefits and limitations of these protocols, and the potential of in vitro cranial placode modeling in regenerative medicine to treat cranial placode-related pathologies.

Patient Experience and Preferences for the Assessment of Olfaction: The Patient International Clinical Assessment of Smell Survey

INTRODUCTION

Olfactory dysfunction (OD) is common and carries significant personal and societal burden of disease. Accurate assessment of olfaction is required for good clinical care and affords patients insight into their condition. However, the accuracy of assessment varies with technique used, and there is presently little standardisation of clinical practice. We therefore aimed to determine experience of and preferences for olfactory assessment in healthcare-seeking adults.

METHODS

An anonymous patient co-produced survey was developed in collaboration with a UK-based OD charity. Distribution was via their social media patient forum. "Healthcare seeking" adults (i.e., who had undergone olfactory assessment by a healthcare professional [any care level/speciality] or may do so in the future) were included.

RESULTS

576 people (88.5% female, mean 46 years) responded. Hyposmia, parosmia, and retronasal OD were most frequently reported. 55.2% had been assessed by a healthcare professional - GP most commonly, followed by ENT. Importantly, only 15.6% and 16.9% of respondents had undergone systematic assessment with smell tests or symptom questionnaires, respectively. Most respondents had not undergone imaging. Mean satisfaction was higher in those seen by ENT. Interestingly, respondents prioritise orthonasal odour identification over other forms of smell test. Unfortunately, many felt that healthcare professionals (across specialities) were dismissive towards OD and lacked appropriate knowledge of both its pathophysiology and effects. We propose simple steps that can be taken to improve olfactory assessment, including education and establishment of robust referral networks.

CONCLUSION

We hope these results and supporting practical recommendations will inform future service planning, funding allocation and research, as well as better aligning patient and clinician priorities.

Odor Identification Across Time in Mutation Carriers and Non-Carriers in Autosomal-Dominant Alzheimer's Disease

BACKGROUND

Impaired odor identification is a characteristic of sporadic Alzheimer'sdisease(AD), but its presence in autosomal-dominantAD (adAD) remains uncertain.

OBJECTIVE

To investigate odor identification ability in mutation carriers (MC) and non-carriers (NC) of adAD in relation to years to estimated clinical onset clinical onset (YECO) of disease.

METHODS

Participants from six families with autosomal-dominant mutations (APP Swedish, APP Arctic, and PSEN1 mutations) included 20 MC and 20 NC. The groups were comparable in age, gender, education, number of APOE ɛ4 alleles, and YECO, but differed in global cognition (Mini-Mental State Examination). The MC group included individuals in asymptomatic, symptomatic cognitively unimpaired, mild cognitive impairment, and dementia stages of disease, spanning approximately 40 years of the AD continuum. All NC were asymptomatic. Olfactory function was assessed by means of free and cued identification of common odors summarized as total identification.

RESULTS

MC performed poorer than NC in free and total identification. Four MC and none of the NC were anosmic. Olfactory functions in MC and NC were significantly and inversely related to time course (YECO) for both free and total identification. The decline in free identification began approximately 10 years prior to the estimated clinical onset of AD in MC. Odor identification proficiency was associated with episodic memory and executive function in MC and NC.

CONCLUSIONS

Impaired odor identification is present well before the clinical diagnosis of AD in MC and is associated with disease progression. Odor identification ability may be a useful early biomarker for adAD.

Integrating the patient's voice into the research agenda for treatment of chemosensory disorders

World-wide some 658 million people were infected with coronavirus disease 2019 (COVID-19) and millions suffer from chemosensory impairment associated with long COVID. Current treatments for taste and smell disorders are limited. Involving patients has the potential to catalyze the dynamic exchange and development of new ideas and approaches to facilitate biomedical research and therapeutics. We assessed patients' perceptions of the efficacy of treatments for chemosensory impairment using an online questionnaire completed by 5,815 people in the US Logistic regression determined variables predictive of reported treatment efficacy for patients aged 18 to 24, 25 to 39, 40 to 60, and 60+ yrs. who were treated with nasal steroids, oral steroids, zinc, nasal rinse, smell training, theophylline, platelet-rich plasma, and Omega 3. The most consistent predictor was age, with the majority of those 40 to 60 and 60+ reporting that nasal steroids, oral steroids, zinc, nasal rinse, and smell training were only slightly effective or not effective at all. Many of these treatment strategies target regeneration and immune response, processes compromised by age. Only those under 40 reported more than slight efficacy of steroids or smell training. Findings emphasize the need to include patients of all ages in clinical trials. Older adults with olfactory impairment are at increased risk for Alzheimer's disease (AD). We speculate that olfactory impairment associated with long COVID introduces the potential for a significant rise in AD. Long COVID-associated chemosensory impairment increases the urgency for translational and clinical research on novel treatment strategies. Suggestions for high-priority areas for epidemiological, basic, and clinical research on chemosensory impairment follow.

Lifelong olfactory deprivation-dependent cortical reorganization restricted to orbitofrontal cortex

Prolonged sensory deprivation has repeatedly been linked to cortical reorganization. We recently demonstrated that individuals with congenital anosmia (CA, complete olfactory deprivation since birth) have seemingly normal morphology in piriform (olfactory) cortex despite profound morphological deviations in the orbitofrontal cortex (OFC), a finding contradictory to both the known effects of blindness on visual cortex and to the sparse literature on brain morphology in anosmia. To establish whether these unexpected findings reflect the true brain morphology in CA, we first performed a direct replication of our previous study to determine if lack of results was due to a deviant control group, a confound in cross sectional studies. Individuals with CA (n = 30) were compared to age and sex matched controls (n = 30) using voxel- and surface-based morphometry. The replication results were near identical to the original study: bilateral clusters of group differences in the OFC, including CA atrophy around the olfactory sulci and volume increases in the medial orbital gyri. Importantly, no group differences in piriform cortex were detected. Subsequently, to assess any subtle patterns of group differences not detectable by our mass-univariate analysis, we explored the data from a multivariate perspective. Combining the newly collected data with data from the replicated study (CA = 49, control = 49), we performed support vector machine classification based on gray matter volume. In line with the mass-univariate analyses, the multivariate analysis could accurately differentiate between the groups in bilateral OFC, whereas the classification accuracy in piriform cortex was at chance level. Our results suggest that despite lifelong olfactory deprivation, piriform (olfactory) cortex is morphologically unaltered and the morphological deviations in CA are confined to the OFC.

Nutritional Management of Oncological Symptoms: A Comprehensive Review

Throughout their experience of illness and during the course of treatment, a substantial proportion of cancer patients are prone to develop nutritional and/or metabolic disturbances. Additionally, cancer patients often encounter long-term side effects from therapies, which may lead to impaired digestion, nutrient absorption or bowel motility. Therefore, the preservation and maintenance of an optimal and balanced nutritional status are pivotal to achieving a better prognosis, increasing the tolerance and adherence to cancer therapies and improving the overall quality of life. In this context, personalized nutritional programs are essential for addressing conditions predisposing to weight loss, feeding difficulties, digestion problems and intestinal irregularity, with the goal of promoting adequate nutrient absorption and minimizing the detrimental effects of treatment regimens. The focus of this research is to examine the most common clinical conditions and metabolic changes that cancer patients may experience, including stomatitis, xerostomia, diarrhea, nausea, vomiting, dysphagia, sub-occlusion, dysgeusia, dysosmia, anorexia, and cachexia. Furthermore, we present a pragmatic example of a multidisciplinary workflow that incorporates customized recipes tailored to individual clinical scenarios, all while maintaining the hedonic value of the meals.

One-year psychophysical evaluation of COVID-19-induced olfactory disorders: a prospective cohort study

BACKGROUND

Olfactory disorders are common in COVID-19. While many patients recover within weeks, a notable number of patients suffer from prolonged olfactory disorders. Much research has focused on the acute phase of olfactory disorders in COVID-19; however, there is still inconsistency regarding the prognosis. We aim to assess both objective and subjective olfactory function in patients with persisting olfactory disorders following COVID-19, 1 year after diagnosis.

METHODS

We objectively measured olfactory function in 77 patients who initially had COVID-19-induced smell disorders, 1 year after confirmed diagnosis. These patients previously underwent two objective measurements at approximately 3 and 6 months after COVID-19, in the context of the COCOS trial (COrticosteroids for COvid-19-induced loss of Smell). The main outcome measurement was TDI score (threshold-discrimination-identification) on Sniffin' Sticks Test (SST). Secondary outcomes included objective gustatory function on Taste Strip Test (TST), self-reported olfactory, gustatory and trigeminal function on a visual analogue scale (VAS) and outcomes on questionnaires about quality of life, and nasal symptoms.

RESULTS

The findings of this study show that 1 year following COVID-19, the median TDI score increased to 30.75 (IQR 27.38-33.5), regarded as normosmia. The median TDI score started at 21.25 (IQR 18.25-24.75) at baseline and increased to 27.5 (IQR 23.63-30.0) at 6 months following COVID-19. The increase of 9.5 points on the TDI score between baseline and 1 year after COVID-19 marks a clinically relevant improvement. Regarding the self-reported VAS score (1-10) on sense of smell, it increased from 1.2 (IQR 0.4-3.0) at baseline to 3.2 (IQR 1.4-6.0) at 6 months and further improved up to 6.1 (IQR 2.7-7.5) after 1 year. Objective gustatory function increased with 2 points on TST a year after diagnosis. Self-reported olfactory, gustatory, and trigeminal functions also improved over time, as did quality of life.

CONCLUSIONS

Objective and self-reported olfactory function continued to improve 1 year after COVID-19. The median TDI score of 30.75 (IQR 27.38-33.5) is regarded as normosmia, which is a favorable outcome. However, the rate of improvement on TDI score reduces over time.

Olfactory Dysfunction in Children: A Scoping Review

OBJECTIVE

Olfactory disorders are well-studied in the adult population, however, there is a paucity of literature characterizing olfactory dysfunction in pediatric patients. The purpose of this scoping review was to identify known causes of olfactory loss in pediatric populations, clarify the extent of use and validity of smell tests, and summarize current therapies for olfactory loss.

DATA SOURCES

PubMed, Ovid MEDLINE, and Web of Science.

REVIEW METHODS

Databases were systematically searched in September 2020. Two independent reviewers conducted the title and abstract screen, followed by review of full-texts for inclusion based on preset inclusion and exclusion criteria. Extracted data included study type, age/age-range of participants, gender, radiological evidence of olfactory dysfunction, types and results of smell tests used, etiology of olfactory loss, and therapies employed for olfactory loss.

RESULTS

A total of 103 articles (n = 1654) were eligible for final data extraction. The University of Pennsylvania Smell Identification Test was used most frequently for smell testing (21% of studies). In total, 45 causes of olfactory dysfunction have been elucidated by this study: 22 congenital and 23 acquired. Few therapies were described, and all were specific to the etiology of olfactory loss.

CONCLUSION

Olfactory dysfunction has a wide range of etiologies in the pediatric population, and clinicians should have a diagnostic algorithm for how to identify a cause should they encounter it in practice. If no etiology can be identified, education around safety should be provided to both the patient and their caregivers.

Special Sensory Function Deficit among Patients with Post-COVID-19 Visiting a Tertiary Care Centre

Introduction

Several patients who recover from COVID-19 infection continue to have persistent symptoms even after recovery from the disease. The special sensory functions such as taste, smell and hearing are affected by COVID-19 infection even after recovery from the illness. The aim of the study was to find out the prevalence of special sensory deficits among patients with post-COVID-19 visiting a tertiary care centre.

Methods

A descriptive cross-sectional study was conducted among adult patients who recovered from COVID-19 visiting a tertiary care centre from 1 January 2022 to 31 December 2022. After obtaining ethical approval from the Research Ethics Board of Health, data on patients who were diagnosed with COVID-19 one year ago was obtained from the surveillance register from the Ministry of Health. They were contacted by phone call and invited to the centre to participate in the study. Appropriate clinical examination and tests were carried out to assess the special sensory deficits. A convenience sampling technique was used. The point estimate was calculated at a 95% Confidence Interval.

Results

Among 271 patients, the prevalence of sensory function deficit was 39 (14.39%) (10.21-18.57, 95% Confidence Interval).

Conclusions

The prevalence of special sensory deficits after recovery from COVID-19 infections was found to be similar to the findings of other studies.

Keywords

anosmia; COVID-19; hearing loss.

Experiences of living without a sense of smell: Like "Being Behind Glass"

This study addresses the paucity of research concerning the subjective experiences of those affected by anosmia. In the study, we interviewed individuals(n = 11) recruited via the charity (Fifth Sense) and used Interpretative Phenomenological Analysis (IPA) to analyse the data. Findings revealed three main themes and seven sub themes. The main themes are Living with Anosmia; Remembrance of things old and new and Resilience. The study reveals the process of becoming aware of being anosmic and the relationships with others in this process including potentially unhelpful minimisations of the impact by professionals. In addition to a sense of isolation and insecurity, living with anosmia for some participants brought with it an identification of being 'anosmic' and feeling part of a community. This was in contrast to a general lack of public knowledge and understanding of anosmia. The findings of the study demonstrated the importance of smell to time, place and relationship and the recalling of smells as bringing a sense of connectivity to loved ones, of times past and also a sense of loss of ability. Participants also described the ways in which they coped and adapted to a life with anosmia and focused on positive aspects of life. These findings provide a rich qualitative account of the experience of anosmia. The findings point towards future research which could inform us about the lives of those who are anosmic and currently unaware and of those recently diagnosed, which will create a richer understanding of the experiences of anosmia.

Outcome and Safety of Insulin in the Management of Smell Loss: A Systematic Review

Background: Olfactory dysfunction can negatively impact the quality of life and increase the risk of danger from warning odors. Various factors can cause olfactory dysfunction, including COVID-19 infection, which has increased anosmia cases. No medications are approved; however, recent studies have suggested that intranasal insulin could effectively treat olfactory dysfunction. Aim: To comprehensively evaluate the effectiveness and safety of intranasal insulin in treating olfactory dysfunction. Materials and Methods: PubMed, Google Scholar, and CENTRAL databases were searched using specific keywords, and the outputs were screened using the Rayyan AI system. Original research articles published without time frame limitations that reported the relevant outcomes were included. The reviewers performed the screening and data extraction, and any disagreements were resolved by a third senior author. Results: This systematic review identified 66 references from 3 databases, with 45 articles meeting the criteria for review after duplicates were removed. Six articles met the inclusion criteria and were selected, including 177 subjects. The selected studies consisted of various study designs, including pilot studies, placebo-controlled trials, crossover studies, and randomized clinical trials. The findings showed that intranasal insulin therapy had beneficial effects on olfactory function. Specifically, improvements were observed in olfactory detection and discrimination in patients with post-COVID-19 anosmia, olfactory threshold performance in healthy participants, and odor identification in hyposmic patients. However, there were variations in the observed effects based on different doses of insulin administered and gender differences. It also shows that using insulin provides good outcomes. Using it intranasally was safe and did not cause any complications. Conclusion: Intranasal insulin has shown promising results as a potentially safe treatment for olfactory dysfunction. Studies suggest that it can improve olfactory thresholds. Further studies are needed to investigate optimal doses and potential gender differences in response.

Olfactory training effects in children after mild traumatic brain injury

OBJECTIVE

Mild traumatic brain injury (mTBI) might impair the sense of smell and cognitive functioning. Repeated, systematic exposure to odors, i.e., olfactory training (OT) has been proposed for treatment of olfactory dysfunctions, including post-traumatic smell loss. Additionally, OT has been shown to mitigate cognitive deterioration in older population and enhance selected cognitive functions in adults. We aimed to investigate olfactory and cognitive effects of OT in the pediatric population after mTBI, likely to exhibit cognitive and olfactory deficits.

METHODS

Our study comprised 159 children after mTBI and healthy controls aged 6-16 years (M = 9.68 ± 2.78 years, 107 males), who performed 6-months-long OT with a set of 4 either high- or low-concentrated odors. Before and after OT we assessed olfactory functions, fluid intelligence, and executive functions.

RESULTS

OT with low-concentrated odors increased olfactory sensitivity in children after mTBI. Regardless of health status, children who underwent OT with low-concentrated odors had higher fluid intelligence scores at post-training measurement, whereas scores of children performing OT with high-concentrated odors did not change.

CONCLUSION

Our study suggests that OT with low-concentrated odors might accelerate rehabilitation of olfactory sensitivity in children after mTBI and support cognitive functions in the area of fluid intelligence regardless of head trauma.

Characteristics of smell and taste disorders depending on etiology: a retrospective study

PURPOSE

This study investigates the impact of etiology on the epidemiologic profile, disease severity, type of treatment and therapy outcome in smell and taste disorders.

METHODS

This is a retrospective analysis of 270 patients that presented with a smell or taste disorder in a specialized, tertiary care center. An established questionnaire was used to collect data from patients and physicians. Olfactometry was performed with the Sniffin' Sticks test kit, while gustometry was performed by taste strips.

RESULTS

Post-traumatic etiology was associated with young age (median 46 years) and male sex, and showed the most severe degrees of smell loss compared to other etiologies (64.3% anosmia). Postinfectious causes occurred more frequently in females (77.3%) and correlated with a history of pharyngeal surgery, suggesting a vulnerability for virally mediated sensory dysfunction following adenoid/tonsil removal. Parosmia also correlated with both postinfectious etiology (62.5%) and female sex. In sinunasal etiology, the presence of nasal polyps worsened the overall olfactory test score by approximately 50%. In particular, smell threshold and discrimination were reduced, while smell identification was not significantly impacted by nasal polyp obstruction. Sinunasal dysfunction was the only etiology to show significant improvement after therapy (73.9% improved). Finally, we could establish good correlations between the subjective impairment and objective dysfunction for each sensory modality.

CONCLUSION

Each etiology of chemosensory dysfunction shows particular distributions of variables like sex, age, comorbidities and operations, disease severity, sensory threshold, discrimination and identification. This paper offers a detailed account of the correlations between the cause and the characteristics of smell and taste loss.

Poor preoperative performance at Clock Drawing Test is associated with postoperative decline in olfaction in older patients: an observational pilot study

BACKGROUND

Decline in olfaction may occur after general anesthesia, but the exact incidence and underlying physiopathology remain scarcely investigated. Olfactory dysfunction arises with aging and is known to be linked to cognitive impairment. In this pilot study, we evaluated the incidence of immediate postoperative decline in olfaction and its association with a preoperative cognitive test, performance at Clock Drawing Test (CDT), in a group of older patients.

METHODS

This pilot study is a sub-analysis of a prospective observational study. Patients ≥ 65 years old and scheduled for elective non-cardiac surgery under sevoflurane-based anesthesia were enrolled. CDT was part of the preoperative evaluation. We assessed olfaction on the day before and the day after surgery (between 16 and 26 h postoperatively) using the Sniffin' Sticks 12-item identification test, which consists of pen-like devices displaying 12 different odors. Postoperative decline in olfaction was defined as a decrease of at least 1 standard deviation in the olfactory score.

RESULTS

We included a total of 93 patients, among whom 19 (20.4%) presented a postoperative decline in olfaction. The incidence of postoperative decline in olfaction was higher in the "CDT low-score" (score ≤ 5/8) group (11/34, 32.4%) than in the "CDT high-score" (score ≥ 6/8) group (8/58, 13.6%) (P = 0.030). Despite adjusting for confounding variables, CDT score remained independently associated with immediate postoperative decline in olfactory identification function (OR 0.67, 95% CI 0.48 to 0.94, P = 0.022).

CONCLUSIONS

Postoperative decline in olfaction occurred in 20.4% of older patients and was associated with poor preoperative performance at CDT.

TRIAL REGISTRATION

This study was retrospectively registered on https://clinicaltrials.gov/ under the NCT04700891 number (principal investigator: Victoria Van Regemorter), in December 2020.

Effect of any form of steroids in comparison with that of other medications on the duration of olfactory dysfunction in patients with COVID-19: A systematic review of randomized trials and quasi-experimental studies

BACKGROUND

The life quality of about two-thirds of patients with COVID-19 is affected by related olfactory dysfunctions. The negative impact of olfactory dysfunction ranged from the decreased pleasure of eating to impaired quality of life. This research aimed to provide a comprehensive understanding of the effects of corticosteroid treatments by comparing that to other currently available treatments and interventions.

METHODS

The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist's 27-point checklist was used to conduct this review. PubMed (Public/Publisher MEDLINE), PubMed Central and EMBASE (Excerpta Medica Database) databases were conveniently selected and Boolean search commands were used for a comprehensive literature search. Five core search terms were "effects of treatments", " COVID-19-related olfactory dysfunction", "corticosteroids", "treatments" and "interventions". The reporting qualities of the included studies were appraised using JBI (Joanna Briggs Institute) appraisal tools. The characteristics of the 21 experimental studies with a total sample (of 130,550) were aggregated using frequencies and percentages and presented descriptively. The main interventions and their effects on the duration of the COVID-19-related olfactory dysfunction were narratively analyzed.

RESULTS

Among patients with COVID-19, the normal functions of the olfactory lobe were about 23 days earlier to gain with the treatments of fluticasone and triamcinolone acetonide nasal spray compared with that of mometasone furoate nasal spray and oral corticosteroid. The smell loss duration was reduced by fluticasone and triamcinolone acetonide nasal spray 9 days earlier than the inflawell syrup and 16 days earlier than the lavender syrup. The nasal spray of corticosteroids ended the COVID-19-related smell loss symptoms 2 days earlier than the zinc supplementation, about 47 days earlier than carbamazepine treatment and was more effective than palmitoylethanolamide (PEA) and luteolin and omega-3 supplementations and olfactory training. Treatment with oral corticosteroid plus olfactory training significantly improved Threshold, Discrimination and Identification (TDI) scores compared with olfactory training alone. A full dose of the COVID-19 vaccination was not uncertain to reduce the COVID-19-related smell loss duration.

CONCLUSION

Corticosteroid treatment is effective in reducing the duration of COVID-19-related smell loss and olfactory training, the basic, essential and effective intervention, should be used as a combination therapy.

Smell-related quality of life changes after total laryngectomy: a multi-centre study

PURPOSE

A total laryngectomy creates an alternate airway for gas exchange that bypasses the upper aerodigestive tract. The subsequent reduction in nasal airflow, and therefore, reduction in deposition of particles to the olfactory neuroepithelium leads to hyposmia or anosmia. The aim of this study was to assess the quality of life impairment conferred by anosmia following laryngectomy and identify any specific patient-related risk factors that are associated with poorer outcomes.

METHODS

Consecutive patients with a total laryngectomy presenting for review at three tertiary head and neck services (in Australia, the United Kingdom and India) over a 12-month period were recruited. Patient demographic and clinical data were collected, and each subject completed the validated assessment of self-reported olfactory functioning and olfaction-related quality of life questionnaire (ASOF). Dichotomous comparisons were performed using the student's unpaired t-test for continuous variables (SRP), a chi-squared test for categorical variables, and a Kendall's tau-b for ordinal variables (SOC) to assess for a correlation with poorer questionnaire scores.

RESULTS

A total of 66 laryngectomees (13.4% female; age 65.7 ± 8.6 years) were included in the study. The mean SRP score of the cohort was found to be 15.6 ± 7.4, while the mean ORQ score was noted to be 16.4 ± 8.1. No other specific risk factors associated with poorer quality of life were identified.

CONCLUSION

A significant quality of life detriment from hyposmia is conferred following laryngectomy. Further research to assess treatment options and the patient population that would best benefit from these interventions is required.

COVID-19 and Neurological Manifestations

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a newly emerged coronavirus, has sparked a global pandemic with its airborne transmission and ability to infect with asymptomatic patients. The pathophysiology is thought to relate to the binding of angiotensin converting enzyme 2 (ACE2) receptors in the body. These receptors are widely expressed in various body organs such as the lungs, the heart, the gastrointestinal tract (GIT), and the brain. This article reviews the current knowledge on the symptoms of coronavirus disease 2019 (COVID-19), highlighting the neurological symptoms that are associated with COVID-19, and discussing the possible mechanisms for SARS-CoV-2 virus infection in the body.

The immune mechanism of the nasal epithelium in COVID-19-related olfactory dysfunction

During the first waves of the coronavirus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, olfactory dysfunction (OD) was reported as a frequent clinical sign. The nasal epithelium is one of the front-line protections against viral infections, and the immune responses of the nasal mucosa may be associated with OD. Two mechanisms underlying OD occurrence in COVID-19 have been proposed: the infection of sustentacular cells and the inflammatory reaction of the nasal epithelium. The former triggers OD and the latter likely prolongs OD. These two alternative mechanisms may act in parallel; the infection of sustentacular cells is more important for OD occurrence because sustentacular cells are more likely to be the entry point of SARS-CoV-2 than olfactory neurons and more susceptible to early injury. Furthermore, sustentacular cells abundantly express transmembrane protease, serine 2 (TMPRSS2) and play a major role in the olfactory epithelium. OD occurrence in COVID-19 has revealed crucial roles of sustentacular cells. This review aims to elucidate how immune responses of the nasal epithelium contribute to COVID-19-related OD. Understanding the underlying immune mechanisms of the nasal epithelium in OD may aid in the development of improved medical treatments for COVID-19-related OD.

Post-COVID-19 Anosmia and Therapies: Stay Tuned for New Drugs to Sniff Out

Background: Anosmia is defined as the complete absence of olfactory function, which can be caused by a variety of causes, with upper respiratory tract infections being among the most frequent causes. Anosmia due to SARS-CoV-2 infection has attracted attention given its main role in symptomatology and the social impact of the pandemic. Methods: We conducted systematic research in a clinicaltrials.gov database to evaluate all active clinical trials worldwide regarding drug therapies in adult patients for anosmia following SARS-CoV-2 infection with the intention of identifying the nearby prospects to treat Anosmia. We use the following search terms: "Anosmia" AND "COVID-19" OR "SARS-CoV-2" OR "2019 novel coronavirus". Results: We found 18 active clinical trials that met our criteria: one phase 1, one phase 1-2, five phases 2, two phases 2-3, three phases 3, and six phases 4 studies were identified. The drug therapies that appear more effective and promising are PEA-LUT and Cerebrolysin. The other interesting drugs are 13-cis-retinoic acid plus aerosolized Vitamin D, dexamethasone, and corticosteroid nasal irrigation. Conclusions: COVID-19 has allowed us to highlight how much anosmia is an important and debilitating symptom for patients and, above all, to direct research to find a therapy aimed at curing the symptom, whether it derives from SARS-CoV-2 infection or other infections of the upper airways. Some of these therapies are very promising and are almost at the end of experimentation. They also provide hope in this field, which not addressed until recently.

The potential for clinical application of automatic quantification of olfactory bulb volume in MRI scans using convolutional neural networks

The olfactory bulbs (OBs) play a key role in olfactory processing; their volume is important for diagnosis, prognosis and treatment of patients with olfactory loss. Until now, measurements of OB volumes have been limited to quantification of manually segmented OBs, which is a cumbersome task and makes evaluation of OB volumes in large scale clinical studies infeasible. Hence, the aim of this study was to evaluate the potential of our previously developed automatic OB segmentation method for application in clinical practice and to relate the results to clinical outcome measures. To evaluate utilization potential of the automatic segmentation method, three data sets containing MR scans of patients with olfactory loss were included. Dataset 1 (N = 66) and 3 (N = 181) were collected at the Smell and Taste Center in Ede (NL) on a 3 T scanner; dataset 2 (N = 42) was collected at the Smell and Taste Clinic in Dresden (DE) on a 1.5 T scanner. To define the reference standard, manual annotation of the OBs was performed in Dataset 1 and 2. OBs were segmented with a method that employs two consecutive convolutional neural networks (CNNs) that the first localize the OBs in an MRI scan and subsequently segment them. In Dataset 1 and 2, the method accurately segmented the OBs, resulting in a Dice coefficient above 0.7 and average symmetrical surface distance below 0.3 mm. Volumes determined from manual and automatic segmentations showed a strong correlation (Dataset 1: r = 0.79, p < 0.001; Dataset 2: r = 0.72, p = 0.004). In addition, the method was able to recognize the absence of an OB. In Dataset 3, OB volumes computed from automatic segmentations obtained with our method were related to clinical outcome measures, i.e. duration and etiology of olfactory loss, and olfactory ability. We found that OB volume was significantly related to age of the patient, duration and etiology of olfactory loss, and olfactory ability (F(5, 172) = 11.348, p < 0.001, R2 = 0.248). In conclusion, the results demonstrate that automatic segmentation of the OBs and subsequent computation of their volumes in MRI scans can be performed accurately and can be applied in clinical and research population studies. Automatic evaluation may lead to more insight in the role of OB volume in diagnosis, prognosis and treatment of olfactory loss.

COVID-19-Related Long-Term Taste Impairment: Symptom Length, Related Taste, Smell Disturbances, and Sample Characteristics

INTRODUCTION

 The COVID-19 infection triggered in some patients a prolonged reduction in the perception of both gustatory and olfactory senses (ageusia and anosmia). These symptoms could be manifested during the first days after the contagion, acting as predictors of COVID-19 infection, and additionally, they could be the only symptoms manifested at all. Clinical resolution of anosmia and ageusia was expected to occur within a few weeks, yet in some cases, patients began to demonstrate COVID-19-related long-term taste impairment (CRLTTI), a condition that can persist for longer than two months, contradicting initial evidence.  Objectives: The authors' aimed to describe the characteristics of the sample of 31 participants with COVID-19-related long-term taste impairment, and their capacity to quantify taste and rate their smell perception.  Material and Methods: Participants were submitted to a taste evaluation of four hyper-concentrated tastes perceived by the tongue (0-10), self-reported their smell (0-10), and answered a semi-structured questionnaire.  Results: Different tastes seemed to be affected differently by COVID-19, despite the lack of statistical relevance observed in this study. Dysgeusia was only expressed in bitter, sweet, and acidic tastes. The mean age observed was 40.2 (SD 12.06) years, with women representing 71% of the sample. Taste impairment persisted for an average period of 10.8 months (SD 5.7). Self-reported smell impairment was reported by the majority of participants with taste impairment. Non-vaccinated people represented 80.6% of the sample.  Conclusions: COVID-19 infection could trigger taste and smell disturbances that lasted as long as 24 months. CRLTTI seems not to affect the four main taste perceptions (hyper-concentrated) equally. Women represented the majority of the sample, with an average age of 40 years (SD 12.06). Previous diseases, medication use, and behavioral aspects seem not to be linked to CRLTTI development.

A Review of Stellate Ganglion Block as an Adjunctive Treatment Modality

Peripheral nerve blocks are becoming increasingly used as adjunctive treatment modalities for a variety of conditions refractory to medical management. Right or left stellate ganglion blocks (SGB) are a specific type of peripheral nerve block that target the sympathetic blockade of neuronal impulses using the injection of local anesthetic and steroids into nerve bundles in the cervical area. This review article is intended to summarize the common uses of stellate ganglion blocks and explain the procedural technique, which has evolved with technological advances in ultrasonography. The similarities between these disease processes are centered around sympathetic hyperactivity. This sympathetic overdrive state is created by increased levels of nerve growth factor (NGF), which causes a cascade of sympathetic sprouting resulting in increased norepinephrine (NE) systemically. Reversal of this cascade by local anesthetic injection into the stellate ganglion thereby reduces NGF and sympathetic sprouting subsequently lowering overall norepinephrine levels. This is the unifying theory by which SGB is able to provide resolution for the varied clinical conditions described in this article.  This review article discusses the physiology of several conditions where stellate ganglion blocks are being investigated as an adjunct treatment modality, including anosmia, PTSD, long-COVID, chronic fatigue syndrome, menopausal hot flashes, and ventricular tachyarrhythmias. Overall, the current literature supporting the use of stellate ganglion blocks for several esoteric conditions is limited; however, case reports to date have shown promising evidence-based results supporting their use as an adjunctive treatment among patients with refractory symptoms to existing treatment algorithms. In conclusion, SGB should be considered among patients with refractory symptoms for medical management in the conditions discussed in this article. Further research is needed to delineate which patients will benefit from the use of SGB, the use of subsequent blocks and timelines in between injections, and unilateral versus bilateral blockade.

Pathogenesis and progression of anosmia and dysgeusia during the COVID-19 pandemic

Severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) is the causative agent of COVID-19 which was detected in late 2019 in Wuhan, China. As of September 2022, there have been over 612 million confirmed cases of COVID-19 with over 6.5 million associated deaths. In many cases, anosmia and dysgeusia have been identified as primary symptoms of COVID-19 infection in patients. While the loss of smell (anosmia) and loss of taste (dysgeusia) due to COVID-19 infection is transient in most patients, many report that these symptoms persist following recovery. Understanding the pathogenesis of these symptoms is paramount to early treatment of the infection. We conducted a literature review of Google Scholar and PubMed to find and analyze studies discussing anosmia and dysgeusia in the context of COVID-19 to understand the progression and management of these symptoms. The mechanism for dysgeusia is largely unknown; however, pathogenesis of anosmia includes inflammation and cytokine release resulting from the infection that alters neuronal signaling, thus inducing the loss of smell that patients experience. Anosmia may be managed and potentially resolved sooner with a combination therapy of olfactory training and budesonide irrigation of the nasal cavity. It is important to note that the variants of SARS-CoV-2 are genetically distinguished from the original virion due to a mutation in their spike proteins, giving them a different symptom profile regarding anosmia and dysgeusia. This variability in symptomatology is an area of study that needs to be further explored.

Odor Discrimination by Lipid Membranes

Odor detection and discrimination in mammals is known to be initiated by membrane-bound G-protein-coupled receptors (GPCRs). The role that the lipid membrane may play in odor discrimination, however, is less well understood. Here, we used model membrane systems to test the hypothesis that phospholipid bilayer membranes may be capable of odor discrimination. The effect of S-carvone, R-carvone, and racemic lilial on the model membrane systems was investigated. The odorants were found to affect the fluidity of supported lipid bilayers as measured by fluorescence recovery after photobleaching (FRAP). The effect of odorants on surface-supported lipid multilayer microarrays of different dimensions was also investigated. The lipid multilayer micro- and nanostructure was highly sensitive to exposure to these odorants. Fluorescently-labeled lipid multilayer droplets of 5-micron diameter were more responsive to these odorants than ethanol controls. Arrays of lipid multilayer diffraction gratings distinguished S-carvone from R-carvone in an artificial nose assay. Our results suggest that lipid bilayer membranes may play a role in odorant discrimination and molecular recognition in general.

Olfactory disorders in COVID-19 patients as a prognostic factor: a systematic review

Background

The reduction, loss, or impaired sense of smell and taste is common in patients with COVID-19. We aimed to investigate olfactory disorders (ODs) in patients with COVID-19 as a prognostic factor.

Methods

In this systematic review and meta-analysis, studies that assessed ODs in patients with COVID-19 were included. International databases, including PubMed, Embase, MEDLINE, Web of Science, and Scopus, were searched up to 20 March 2021. The random-effects model was used to combine the results of studies. Results were reported with a 95% confidence interval.

Results

In this study, out of 724 references, ten studies had the inclusion criteria. The odds of death in patients with the OD were 69% lower than in those without the ODs (OR = 0.31, 95% CI: 0.14, 0.69), and OD increased the odds of positive polymerase chain reaction (PCR) test (OR = 13.34, 95% CI: 4.2, 42.37).

Conclusions

The findings of our study showed that OD had an inverse and significant relationship with death in COVID-19 patients, and the patients with OD seemed to have a lower risk of mortality.

[Involvement of the trigeminal nerve system in the sense of smell]

A systematic review of literature on the issue of involvement in the sense of smell, as well as the interaction between the trigeminal and olfactory nerves, was carried out. The article discusses the features of the chemical perception systems, as well as the treatment of olfactory disorders using transcranial electrical stimulation of the trigeminal nerve.

Ablation of AQP5 gene in mice leads to olfactory dysfunction caused by hyposecretion of Bowman's gland

Smell detection depends on nasal airflow, which can make absorption of odors to the olfactory epithelium by diffusion through the mucus layer. The odors then act on the chemo-sensitive epithelium of olfactory sensory neurons (OSNs). Therefore, any pathological changes in the olfactory area, for instance, dry nose caused by Sjögren's Syndrome (SS) may interfere with olfactory function. SS is an autoimmune disease in which aquaporin (AQP) 5 autoantibodies have been detected in the serum. However, the expression of AQP5 in olfactory mucosa and its function in olfaction is still unknown. Based on the study of the expression characteristics of AQP5 protein in the nasal mucosa, the olfaction dysfunction in AQP5 knockout (KO) mice was found by olfactory behavior analysis, which was accompanied by reduced secretion volume of Bowman's gland by using in vitro secretion measure system, and the change of acid mucin in nasal mucus layer was identified. By excluding the possibility that olfactory disturbance was caused by changes in OSNs, the result indicated that AQP5 contributes to olfactory functions by regulating the volume and composition of OE mucus layer, which is the medium for the dissolution of odor molecules. Our results indicate that AQP5 can affect the olfactory functions by regulating the water supply of BGs and the mucus layer upper the OE that can explain the olfactory loss in the patients of SS, and AQP5 KO mice might be used as an ideal model to study the olfactory dysfunction.

Host-Cell Surface Binding Targets in SARS-CoV-2 for Drug Design

The ongoing pandemic of coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) became a major public health threat to all countries worldwide. SARS-CoV-2 interactions with its receptor are the first step in the invasion of the host cell. The coronavirus spike protein (S) is crucial in binding to receptors on host cells. Additionally, targeting the SARS-CoV-2 viral receptors is considered a therapeutic option in this regard. In this review of literature, we summarized five potential host cell receptors, as host-cell surface bindings, including angiotensin-converting enzyme 2 (ACE2), neuropilin 1 (NRP-1), dipeptidyl peptidase 4 (DPP4), glucose regulated protein-78 (GRP78), and cluster of differentiation 147 (CD147) related to the SARS-CoV-2 infection. Among these targets, ACE2 was recognized as the main SARS-CoV-2 receptor, expressed at a low/moderate level in the human respiratory system, which is also involved in SARS-CoV-2 entrance, so the virus may utilize other secondary receptors. Besides ACE2, CD147 was discovered as a novel SARS-CoV-2 receptor, CD147 appears to be an alternate receptor for SARSCoV- 2 infection. NRP-1, as a single-transmembrane glycoprotein, has been recently found to operate as an entrance factor and enhance SARS Coronavirus 2 (SARS-CoV-2) infection under in-vitro. DPP4, which was discovered as the first gene clustered with ACE2, may serve as a potential SARS-CoV-2 spike protein binding target. GRP78 could be recognized as a secondary receptor for SARS-CoV-2 because it is widely expressed at substantially greater levels, rather than ACE2, in bronchial epithelial cells and the respiratory mucosa. This review highlights recent literature on this topic.