Retronasal olfactory function in nasal polyposis

Olfactory Loss in Rhinosinusitis: Mechanisms of Loss and Recovery

Chronic rhinosinusitis (CRS) is a highly prevalent disease and up to 83% of CRS patients suffer from olfactory dysfunction (OD). Because OD is specifically seen in those CRS patients that present with a type 2 eosinophilic inflammation, it is believed that type 2 inflammatory mediators at the level of the olfactory epithelium are involved in the development of this olfactory loss. However, due to the difficulties in obtaining tissue from the olfactory epithelium, little is known about the true mechanisms of inflammatory OD. Thanks to the COVID-19 pandemic, interest in olfaction has been growing rapidly and several studies have been focusing on disease mechanisms of OD in inflammatory conditions. In this paper, we summarize the most recent data exploring the pathophysiological mechanisms underlying OD in CRS. We also review what is known about the potential capacity of olfactory recovery of the currently available treatments in those patients.

Chemosensory Functions After Glossectomy-A Cross-Sectional Pilot Study

OBJECTIVE

To evaluate potential interactions and compensatory mechanisms of subjectively impaired taste function with ortho- and retronasal olfaction after glossectomy.

STUDY DESIGN

In this cross-sectional pilot study, chemosensory functions were assessed in 25 patients with tongue carcinomas after glossectomy. The orthonasal-, retronasal-, and gustatory functions were tested with a mean time of 25 months after surgery with the Sniffin' Sticks odor identification test kit (ISST), the Candy Smell-27 test (CST-27) and the Taste strip test (TST). Visual analog scales (VAS) were additionally used for self-assessment of taste, flavor perception, and odor ranging from 0 (no perception) to 10 (excellent perception) and further correlated with our psychophysical evaluated outcome measures.

RESULTS

The TST, ISST, and CST-27 tests revealed that only eight (32%) and 13 (52%) glossectomy patients had normal taste and orthonasal function, e 21 (84%) patients showed normal retronasal function. Importantly, neither extent of resection and reconstruction nor prior radiotherapy affected chemosensory functions. Contrary, 20 (80%) patients rated their taste and flavor perception as acceptable (VAS >5). Results of the TST, ISST, and CST-27 tests did not correlate with the equivalent self-assessments of taste (p = 0.260, r = 0.234), odor (p = 0.588, r = -0.114), and flavor (p = 0.728, r = 0.073) perception.

CONCLUSION

There was a significant discrepancy between self-perception of taste and flavor and assessed gustatory function after glossectomy. A contribution of the intact retronasal olfactory system could be a possible explanation of our results.

LEVEL OF EVIDENCE

4 Laryngoscope, 133:375-382, 2023.

A Nasal Aerodynamics Perspective of Retronasal Olfaction: Rodents vs. Humans

Introduction

Odor perception can be achieved through ortho or retronasal routes, with the latter being an important component of flavor perception. There are significant olfactory differences that exist between rats and humans and by understanding the role of structural differences, further insight can be gained into the mechanism of odorant perception via ortho or retronasal routes.

Methods

3D human and rat (Sprague Dawley) computational models were used to investigate nasal anatomy impact on ortho vs. retronasal odorant transport to the olfactory epithelium. The nasal pharynx region was modified for human and rat models to probe nasal structure impact on ortho vs retro olfaction. 65 odorant absorption rates to the olfactory epithelium were extracted from each model.

Results

For human, the retronasal route provided higher peak odorant absorption compared to orthonasal route (left: 90% higher, right: 45% higher), but substantially lowered peak absorption for rat (medial: 97% lower, lateral: 75% lower). For both models, anatomical modification had minimal impact to orthonasal routes, but substantially modulated the retronasal route: decrease (left: -41.4%, right: -44.2%) for human, and increase to the medial (29.5%) but not to lateral (-14.3%) for rat.

Conclusions

There exist key differences between humans and rats regarding retro/orthonasal odorant transport routes, which matched well with experimental olfactory bulb activity data in literature.

Implications

While humans have equivalent odorant delivery between routes, the difference in retro and orthonasal routes in rodents is substantial and changes to the transverse lamina above the nasopharynx can substantially modulate the retronasal route, but not enough to bridge the gap between the two routes.

Beyond aroma: A scoping review on the impact of chronic rhinosinusitis on retronasal olfaction

Background

Retronasal olfaction (RNO) refers to the perception of odorants inhaled through the mouth and carried through the nasopharynx to olfactory receptors within the olfactory cleft, enabling the perception of flavor. Although orthonasal olfactory dysfunction in chronic rhinosinusitis (CRS) has been widely described, the impact of CRS on RNO is less clear. In this study, we systematically review available literature to provide an update on RNO in the setting of CRS.

Methods

We systematically searched PubMed, Ovid Embase, Web of Science, and the Cochrane Library for studies examining RNO in patients with documented CRS. The primary outcome of interest was objective psychophysical measurement of olfaction, including characterization of RNO.

Results

We identified 404 unique references that underwent title and abstract review by two independent reviewers, with 52 articles undergoing full-text review, where 10 relevant studies underwent data extraction. Although outcome measures varied, all included studies demonstrated diminished RNO in patients with CRS. Of six studies evaluating the relationship between retronasal and orthonasal olfactory test scores in CRS patients two out of six (33%) demonstrated a correlation between both forms of olfaction and CRS, and two out of six studies (33%) found significantly lower orthonasal olfactory test scores compared to retronasal olfactory test scores. Two of three found significant improvement in RNO with treatment of underlying CRS. Of three studies examining patient reported outcome measures (PROMs) in CRS, two found significant associations between retronasal olfactory test scores and PROMs.

Conclusions

Based on the current literature, CRS patients appear to have diminished RNO, which may be associated with orthonasal olfactory dysfunction and decreased quality of life in this population. Higher level of evidence studies are required to further elucidate these relationships and the impact of medical and surgical CRS management on RNO.

Riech- und Schmeckstörungen

Ziel der vorliegenden Übersicht ist es, einen Überblick über die Ätiologie und Diagnostik von Riech- und Schmeckstörungen zu geben. Da etwa 5 % der Allgemeinbevölkerung betroffen sind, ist es ein häufiges Krankheitsbild. Riechen und Schmecken erhielten v. a. zuletzt Aufmerksamkeit während des Aufkommens der SARS-CoV-2-Pandemie, wobei eine plötzlich aufgetretene Riech- und/oder Schmeckstörung zu den typischen Symptomen zählt. Daneben sind Riechstörungen in der Frühdiagnostik neurodegenerativer Erkrankungen von Bedeutung. Häufig zeigen Patienten mit Riechstörungen Zeichen einer Depression. Die Auswirkungen von Riech‑/Schmeckstörungen sind also umfangreich, die Therapiemöglichkeiten aktuell begrenzt. Nach einem Einblick in die Ätiologie werden Diagnostik und Therapiemöglichkeiten auf dem aktuellen Stand der Literatur erörtert. Auch zukunftsweisende Behandlungsvorstellungen, wie z. B. autologe Schleimhauttransplantationen oder olfaktorische Implantate, werden angesprochen.

International consensus statement on allergy and rhinology: Olfaction

BACKGROUND

The literature regarding clinical olfaction, olfactory loss, and olfactory dysfunction has expanded rapidly over the past two decades, with an exponential rise in the past year. There is substantial variability in the quality of this literature and a need to consolidate and critically review the evidence. It is with that aim that we have gathered experts from around the world to produce this International Consensus on Allergy and Rhinology: Olfaction (ICAR:O).

METHODS

Using previously described methodology, specific topics were developed relating to olfaction. Each topic was assigned a literature review, evidence-based review, or evidence-based review with recommendations format as dictated by available evidence and scope within the ICAR:O document. Following iterative reviews of each topic, the ICAR:O document was integrated and reviewed by all authors for final consensus.

RESULTS

The ICAR:O document reviews nearly 100 separate topics within the realm of olfaction, including diagnosis, epidemiology, disease burden, diagnosis, testing, etiology, treatment, and associated pathologies.

CONCLUSION

This critical review of the existing clinical olfaction literature provides much needed insight and clarity into the evaluation, diagnosis, and treatment of patients with olfactory dysfunction, while also clearly delineating gaps in our knowledge and evidence base that we should investigate further.

[Olfactory and gustatory disorders]

Ziel der vorliegenden Übersicht ist es, einen Überblick über die Ätiologie und Diagnostik von Riech- und Schmeckstörungen zu geben. Da etwa 5 % der Allgemeinbevölkerung betroffen sind, ist es ein häufiges Krankheitsbild. Riechen und Schmecken erhielten v. a. zuletzt Aufmerksamkeit während des Aufkommens der SARS-CoV-2-Pandemie, wobei eine plötzlich aufgetretene Riech- und/oder Schmeckstörung zu den typischen Symptomen zählt. Daneben sind Riechstörungen in der Frühdiagnostik neurodegenerativer Erkrankungen von Bedeutung. Häufig zeigen Patienten mit Riechstörungen Zeichen einer Depression. Die Auswirkungen von Riech‑/Schmeckstörungen sind also umfangreich, die Therapiemöglichkeiten aktuell begrenzt. Nach einem Einblick in die Ätiologie werden Diagnostik und Therapiemöglichkeiten auf dem aktuellen Stand der Literatur erörtert. Auch zukunftsweisende Behandlungsvorstellungen, wie z. B. autologe Schleimhauttransplantationen oder olfaktorische Implantate, werden angesprochen.

Orthonasal, but not Retronasal Olfaction Is Specifically Impaired in Parkinson's Disease

Olfactory dysfunction (OD) in Parkinson's disease (PD) appears several years before the presence of motor disturbance. Olfactory testing has the potential to serve as a tool for early detection of PD, but OD is not specific to PD as it affects up to 20% of the general population. Olfaction includes an orthonasal and a retronasal components; in some forms of OD, retronasal olfactory function is preserved. We aimed to evaluate whether combined testing components allows for discriminating between PD-related OD and non-Parkinsonian OD (NPOD). The objective of this study is to orthonasal and retronasal olfactory function in PD patients and compare them to a NPOD group and to healthy controls. We hypothesized that this combined testing allows to distinguish PD patients from both other groups. We included 32 PD patients, 25 NPOD patients, and 15 healthy controls. Both olfactory components were impaired in PD and NPOD patients, compared with controls; however, NPOD patients had significantly better orthonasal scores than PD patients. Furthermore, the ratio of retronasal/orthonasal score was higher in PD than in both other groups. In the NPOD group, orthonasal and retronasal scores were significantly correlated; no such correlation could be observed in PD patients. In summary, PD patients seem to rely on compensatory mechanisms for flavor perception. Combined orthonasal and retronasal olfactory testing may contribute to differentiate PD patients from patients with NPOD.

Clinical Implications of Psychophysical Olfactory Testing: Assessment, Diagnosis, and Treatment Outcome

Purpose of Review

Olfactory dysfunction dramatically impairs quality of life with a prevalence of 20% in the general adult population. Psychophysical olfactory testing has been widely used to evaluate the ability to smell due to its validated utility and feasibility in clinic. This review summarizes the current literature regarding psychophysical olfactory testing and the clinical relevance of the olfactory testing with different components. Furthermore, the review highlights the diagnosis and treatment value of olfactory subtests in patients with olfactory dysfunction.

Recent Findings

With the accumulation of studies of psychophysical olfactory testing in olfactory disorders, the clinical relevance of olfactory testing with different components is expanding. Different olfactory domains present with distinct olfactory processing and cortical activity. Psychophysical assessment of olfaction with three domains reveals different levels of olfactory processing and might assist with analyzing the pathophysiologic mechanism of the various olfactory disorders. Furthermore, olfactory thresholds provided the largest amount of non-redundant information to the olfactory diagnosis. Sinonasal olfactory dysfunction and non-sinonasal-related olfactory dysfunction are emerging classifications of smell disorders with certain characteristics of olfactory impairment and different responses to the therapy including steroids, sinus surgery, and olfactory training.

Summary

These recent advancements should promote the understanding of psychophysical olfactory testing, the association between individual subcomponents and neurophysiological processes, and pave the way for precision assessment and treatment of the olfactory dysfunction.

Validation study of a novel approach for assessment of retronasal olfactory function with combination of odor thresholds and identification

Purpose

The present study aimed to establish a test battery for the clinical assessment of retronasal odor thresholds and retronasal odor identification.

Study design

Prospective case–control series.

Methods

Sixty participants (36 women, 24 men, mean age 37.6 ± 19.4 years) were enrolled in this study; 36 were healthy controls and 24 were patients with olfactory dysfunction. Orthonasal olfactory function was assessed with the “Sniffin’ Sticks” test battery. Retronasal olfaction was assessed with oral odorant delivery using special containers for threshold function, and with oral tasteless powders for odor identification.

Results

Retronasal and orthonasal olfaction were significantly correlated for threshold scores, identification score, and the sum of threshold and identification score (TI score). Validity analyses showed that the retronasal TI score was able to discriminate between healthy controls and patients with olfactory dysfunction.

Conclusions

Normosmic participants can be distinctly differentiated from patients with olfactory dysfunction using a valid test battery comprised of retronasal threshold and identification tests. Based on the current findings, we advocate a TI score of 16 as a cut-off between patients and controls. Therefore, TI scores of 17 and above would indicate retronasal normosmia.

Clinical Olfactory Working Group consensus statement on the treatment of postinfectious olfactory dysfunction

BACKGROUND

Respiratory tract viruses are the second most common cause of olfactory dysfunction. As we learn more about the effects 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).

OBJECTIVE

Our aim was to provide an evidence-based practical guide to the management of PIOD (including post-coronavirus 2019 cases) for both primary care practitioners and hospital specialists.

METHODS

A systematic review of the treatment options available for the management of PIOD was performed. The written systematic review was then circulated among the members of the Clinical Olfactory Working Group for their perusal before roundtable expert discussion of the treatment options. The group also undertook a survey to determine their current clinical practice with regard to treatment of PIOD.

RESULTS

The search resulted in 467 citations, of which 107 articles were fully reviewed and analyzed for eligibility; 40 citations fulfilled the inclusion criteria, 11 of which were randomized controlled trials. In total, 15 of the articles specifically looked at PIOD whereas the other 25 included other etiologies for olfactory dysfunction.

CONCLUSIONS

The Clinical Olfactory Working Group members made an overwhelming recommendation for olfactory training; none recommended monocycline antibiotics. The diagnostic role of oral steroids was discussed; some group members were in favor of vitamin A drops. Further research is needed to confirm the place of other therapeutic options.

Olfaction: Sensitive indicator of inflammatory burden in chronic rhinosinusitis

BACKGROUND AND OBJECTIVE

Olfactory dysfunction has a high prevalence in chronic rhinosinusitis (CRS) patients and significantly affects quality of life. CRS is recognized as a complex disorder encompassing heterogeneous inflammatory processes in the nose and paranasal sinuses. Olfactory dysfunction in CRS patients is associated with the level of inflammatory mediators and the efficiency of inflammatory control. Learning about the association between CRS-related inflammation and olfactory function will provide clues to the pathogenesis of CRS.

STRUCTURE

The first section of this review describes the assessment of olfactory function using various measures, from ratings to MR based imaging. Then, we discuss the conductive and inflammatory mechanisms related to olfactory dysfunction in CRS: olfaction is associated with certain inflammatory patterns and is potentially a marker of CRS subtype. Finally, we review anti-inflammatory therapies including conservative and surgical approaches, and their effectiveness in olfactory dysfunction in CRS.

CONCLUSION

Assessment of olfactory function should be considered in the clinical evaluation of CRS patients, not only for detecting and quantifying patients' symptom, but also because it appears to be useful to objectively assess the efficacy of CRS treatment over time. In addition, olfaction can be expected to expand the library of CRS phenotypes and endotypes and, hence, pave the way for more precise, tailored treatment options.

Characteristics of Olfactory Disorder With and Without Reported Flavor Loss

OBJECTIVES/HYPOTHESIS

Quality of life related to olfactory disorder (OD) depends on the perceived impairment. It is not known why some patients with OD report smell and flavor loss while others report smell loss only. In order to understand this, we compared the two clinical presentation forms in terms of demographics, clinical features, and orthonasal olfaction test results.

STUDY DESIGN

Observational, analytic, cross-sectional study.

METHODS

A total of 401 patients with measured orthonasal OD presenting at a tertiary referral center were divided in 2 groups according to their subjective reports (smell loss only = 129 patients vs. smell and flavor loss = 272 patients). Groups were compared in terms of demographic (age, sex), clinical features (duration of disease, type of onset, etiology, degree of impairment due to the disorder) and test results (taste and orthonasal olfaction).

RESULTS

Groups did not differ in terms of age, sex distribution, orthonasal olfactory, or taste function. Patients reporting smell and flavor loss were characterized by a mainly sudden onset of the disorder and a predominance of postinfectious olfactory loss. They also have a shorter disease duration and a higher disease impairment. For patients reporting smell loss only, disease duration is longer, they feel less impaired, the onset of the disorder is to a higher degree protracted and the main cause is idiopathic.

CONCLUSIONS

Patients with orthonasal OD reporting smell and flavor loss feel more impaired and present significant different clinical features compared to patients reporting smell loss only. Future studies measuring retronasal olfaction are necessary to fully understand flavor perception in OD.

LEVEL OF EVIDENCE

4 Laryngoscope, 130:2869-2873, 2020.

Ortho- and retronasal olfactory performance in rhinosurgical procedures: a longitudinal comparative study

Purpose

Testing olfaction should be an integral part of a clinical work-up in rhinosurgical procedures. Importantly, intact olfactory experience also includes retronasally perceived odors (retronasal olfaction). This study aimed at comprehensively assessing olfaction in patients undergoing rhinosurgical procedures in a comparative manner and evaluating relations to patient-reported outcome measurements (PROMs).

Methods

Each nostril odor threshold and discrimination, and birhinal identification were tested using Sniffin’ Sticks in 14 subjects assigned for septoplasty (SP), 21 for septorhinoplasty (SRP), and 30 for endoscopic sinus surgery (ESS). The 27-Candy-Smell-Test was used to quantify retronasal abilities. Tests were repeated 3 months after surgery.

Results

Olfactory dysfunction was preoperatively present in 21% of SP, in 47.6% of SRP, and in 80% of ESS patients. Odor threshold side differences were most frequently found in SRP. Frequently, SRP and ESS patients showed severely impaired retronasal olfaction. Half of included subjects re-visited after 3 months, but olfactory function did not improve overall and rarely on an individual basis to a meaningful extent. Subjective ratings on nasal patency and PROMs were not associated with olfaction nor with changes in olfactory scores.

Conclusion

Olfactory function can decisively be impaired a priori not only in patients awaiting sinus surgery, but also in those assigned for functional septorhinoplasty. This impairment may not improve in the short term, which has to be taken into account in patient counseling. This study adds to the current literature on olfaction in rhinosurgery with the extension of retronasal testing.

Olfactory Fluctuation Revisited

OBJECTIVES

Many patients complain about olfactory fluctuation (OF), which is a symptom commonly attributed to sinonasal disease. Data-based evidence for its association with sinonasal disease is scarce. The aim of the study is to identify explanatory variables associated with OF and to analyze its predictive value regarding sinonasal disease.

STUDY DESIGN

We performed a retrospective study based on patients with olfactory dysfunction.

METHODS

We analyzed data from 482 patients attending the smell and taste outpatient clinic with full psychophysical workup and structured questions regarding their symptoms. The questionnaire included items on OF and chronic nasal symptoms. Clinical investigators filled out the second part of this questionnaire that included information about nasal endoscopy, psychophysical tests of orthonasal olfaction (Sniffin' Sticks), retronasal olfaction, and putative etiology of olfactory dysfunction.

RESULTS

OF was more prevalent in sinonasal disease (42.4%) compared to other putative etiologies of olfactory dysfunction such as postinfectious (28%) or posttraumatic (11.7%) (X2 [5, n = 440] = 24.98; P < .0001). OF was strongly associated with Sniffin' Sticks score categories (anosmia, hyposmia, normosmia) (X2 [2, n = 424] = 39.21; P < .0001; Cramer's V = 0.30; P < .0001) and presence of "chronic nasal symptoms" (X2 [1, n = 437] = 22.71; P < .0001; Cramer's V = 0.23; P < .0001). The accuracy in predicting putative sinonasal disease etiology when OF was present depended strongly on the clinical context.

CONCLUSION

Olfactory fluctuation is a symptom mostly but not exclusively associated with sinonasal disease, elevated Sniffin' Sticks test scores, and is frequently accompanied by other nasal complaints. Its presence is valuable information for clinicians to be integrated into the clinical context when doing patients' workup.

LEVEL OF EVIDENCE

4 Laryngoscope, 130:2442-2447, 2020.

Association Between Orthonasal Olfaction and Chemosensory Perception in Patients With Smell Loss

Objectives

Self‐ratings seem to be the most effortless strategy for assessment of patients' chemical senses. Notably, although flavor perception strongly relies on olfaction, the relationship between self‐reported flavor perception and orthonasal olfactory tests have hitherto not been considered. The aim of this study was to investigate the relationship between self‐perceived olfactory function (SO), taste (ST), and flavor perception (SF) and smell test results in patients with olfactory dysfunction (OD).

Methods

We included 203 patients with quantitative OD. Group comparison, bivariate correlation, and ordinal logistic regression were employed to quantify the relationships between predictor variables (age, gender, reason for OD, and orthonasal olfaction—summed scores of threshold, discrimination, and identification [TDI]) and outcomes of SO and SF (“impaired,” “average,” or “good”).

Results

Group comparison revealed significant differences between SO and SF (P < .001). Stronger correlations were found between SO and TDI (r = 0.64), compared to SF and TDI (r = 0.27). No relevant correlation was found between ST and TDI (r = 0.10). Higher TDI was associated with odds of higher SO in univariate (odds ratio = 1.25) and multivariable analyses (adjusted odds ratio = 1.23), and both models showed good fit of data. Conversely, regression models on the associations between TDI and changes in SF did not meet the assumption of goodness of fit.

Conclusion

We found that higher orthonasal olfactory performance was associated with odds of higher SO in patients with OD, even after controlling for olfactory‐relevant factors. To the contrary, similar models based on flavor perception failed to describe these relationships. This indicates for SF and ST to be less represented by the TDI compared to SO.

Level of Evidence

4 Laryngoscope, 130:2213–2219, 2020

Reversible obstruction of the olfactory cleft: impact on olfactory perception and nasal patency

BACKGROUND

Temporary disruption of sensory input can be studied relatively easily for vision or hearing by covering the eyes or ears. In contrast, closing the nostrils affects not only the sense of smell, but also the ability to breathe through the nose and humidify and warm inhaled air. We hypothesized that filling the olfactory cleft (OC) with dissolvable nasal dressing (foam) would temporarily block olfaction while respecting nasal airflow.

METHODS

In 30 healthy volunteers, the OC was unilaterally obstructed in a back-to-front fashion. Orthonasal and retronasal olfactory function were tested before and after foam application. Ratings of odors and subjective nasal patency (SNP) were collected. Peak nasal inspiratory flow (PNIF) was used to measure nasal patency.

RESULTS

Foam was safely applied in every case using minimal instruments. No complications were reported. Orthonasal and retronasal test results decreased significantly in overall participants (all p < 0.0008). Indicating temporary anosmia, 3 subjects reached the lowest possible score for odor-threshold testing, with corresponding drops in retronasal test scores. PNIF values before and after foam application were not significantly different (p = 0.11). SNP ratings decreased slightly, but not significantly (p = 0.052). Odor-intensity ratings dropped significantly (all p < 0.05).

CONCLUSION

The OC can be safely obstructed with dissolvable nasal dressing, resulting in a decrease in odor-intensity and orthonasal and retronasal olfactory function test scores. This procedure may serve as a hyposmia model that maintains normal nasal airflow.

Olfactory and Gustatory Function in Patients With Different Types of Maxillofacial Trauma

OBJECTIVES/HYPOTHESIS

To investigate olfactory and gustatory function in patients with maxillofacial trauma and associated fractures.

STUDY DESIGN

Retrospective cohort study.

METHODS

Olfactory and gustatory function was assessed psychophysically in 124 patients who had sustained maxillofacial trauma with an associated fracture. Five groups were defined based on the fracture type: Le Fort, mandibular, nasal, orbital, and zygomatic. Olfaction was measured with Sniffin' Sticks (threshold, discrimination, identification [TDI] score) and gustation with the taste spray method. Patients self-rated olfactory and gustatory function on a visual analog scale prior to formal testing.

RESULTS

Ten out of 124 patients were found to be anosmic (8%), with half of them found in the Le Fort (skull base) group. The Le Fort fracture group had significantly lower olfactory function than other fracture types (TDI score = 22.4 ± 10.7; P = .01; possible range = 1-48). The mean gustatory spray test score was 3.82 ± 0.4 (possible range = 0-4) without any intergroup differences. Self-rated olfactory function showed a correlation with the measured scores (r = 0.61, P < .001) across all groups.

CONCLUSIONS

The present data show a significant effect of maxillofacial fracture type on the development of anosmia. Maxillofacial fractures involving the skull base, such as Le Fort fractures, are more likely to cause permanent smell loss, whereas the other fracture types are rarely associated with anosmia.

LEVEL OF EVIDENCE

4 Laryngoscope, 131:E331-E337, 2021.

A New Method for Assessment of Retronasal Olfactory Function

OBJECTIVES/HYPOTHESIS

The aim of the study was to develop a test for the assessment of retronasal olfaction in healthy participants and patients with olfactory disorders using "tasteless" powders.

STUDY DESIGN

Prospective case-control series.

METHODS

A total of 150 participants (110 women, 40 men, mean age = 40 ± 16 years) were recruited for this study; 100 were healthy controls and 50 were patients with olfactory loss due to infections of the upper respiratory tract (n = 25), idiopathic causes (n = 12), sinonasal disease (n = 7), and head trauma (n = 6). Orthonasal olfactory function was evaluated using the Sniffin' Sticks test battery, and retronasal olfaction was evaluated using powders lacking distinctive tastes administered to the oral cavity. To establish test-retest reliability, healthy participants had their orthonasal and retronasal function tested twice.

RESULTS

The validity analyses revealed that the selected 16 stimuli differentiated between normosmic participants and patients with olfactory loss, and that retronasal and orthonasal olfaction were highly correlated.

CONCLUSIONS

The results of the present study indicate that patients with olfactory loss and controls can be clearly separated using a reliable test of retronasal olfaction based on 16 retronasal stimuli.

LEVEL OF EVIDENCE

2b Laryngoscope, 131:E324-E330, 2021.

Retronasal olfactory function in patients with smell loss but subjectively normal flavor perception

OBJECTIVES

The human sense of smell constitutes the main part of flavor perception. Typically, patients with loss of olfactory function complain of diminished perception during eating and drinking. However, some patients with smell loss still report normal enjoyment of foods. The aim of the present study was to compare orthonasal and retronasal olfactory function in patients with non-sinonasal smell loss and subjectively normal flavor perception.

METHODS

Nineteen patients (mean age [range] 52.0 [8-83 years]) with self-reported olfactory impairment but subjective normal flavor perception were included. Olfactory performance was assessed using the Sniffin' Sticks (TDI) for orthonasal and the Candy Smell Test (CST) for retronasal function. Visual analogue scales were used for self-assessment of odor (SOP), taste (STP), and flavor perception (SFP), ranging from 0 (no perception) to 10 (excellent perception).

RESULTS

Mean (SD) SFP was 8.0 (1.8). Mean (SD) orthonasal TDI-score of all patients was 14.4 (5.3, range 6-25.3) with 11 patients classified as anosmic and eight as hyposmic. Mean/SD retronasal CST-score was 8.8 (2.7, range 3-13) within the range of anosmia/hyposmia. No correlation was found between SFP and the CST (P = .62).

CONCLUSION

The present results showed that despite claiming normal flavor perception, our patients were ortho- and retronasally dysosmic using standard tests for olfactory function. Although other explanations could be possible, we suggest that this subjective flavor perception might be due to unconscious memory recall from previously experienced cross-modal sensory interactions.

LEVEL OF EVIDENCE

4 Laryngoscope, 130:1629-1633, 2020.

Impaired eating-related quality of life in chronic rhinosinusitis

BACKGROUND

Despite the tremendous burden of smell and taste dysfunction in patients with chronic rhinosinusitis (CRS), objective measures of smell and taste fail to fully account for eating-related disruptions in CRS patient quality of life (QOL). In this study we sought to investigate the driving force behind impaired eating-related QOL in CRS patients.

METHODS

Adult CRS patients were prospectively enrolled and answered a series of surveys relating to smell, taste, overall sinus-specific QOL, and depression. Patients with both smell-related and taste-related eating complaints were considered to have impaired eating-related QOL. Clinical demographics, objective chemosensory scores, and endoscopy scores were collected.

RESULTS

Seventy patients were enrolled and 23% showed impaired eating-related QOL. In multivariable analyses, patients with aspirin-exacerbated respiratory disease (AERD) showed 10.7 times higher odds of impaired eating-related QOL (odds ratio [OR] 10.72; 95% confidence interval [CI], 1.09 to 105.09; p = 0.042); meanwhile, for every 1-point increase in depression scores, the odds of impaired eating-related QOL increased by 1.3 (OR 1.31; 95% CI, 1.10 to 1.57; p = 0.003). For every 1-point decrease in orthonasal olfactory threshold, the odds of impaired eating-related QOL increased by 1.9 times (OR 1.85; 95% CI, 1.14 to 3.00; p = 0.013). Symptom scores, polyp status, endoscopic scores, and other olfactory measures did not remain significant after adjusting for other variables in forward-selection multivariable modeling.

CONCLUSION

Disruptions in eating-related QOL cannot be fully explained by objective smell or taste testing alone. We identified AERD and depression as independent risk factors for greater odds of impaired eating-related QOL in CRS. Improved orthonasal threshold scores were independently associated with better eating-related QOL.

Retronasal olfaction in chronic rhinosinusitis

OBJECTIVE

The goals of this study were to assess retronasal olfaction in patients with chronic rhinosinusitis (CRS) and describe clinical factors that influence retronasal olfaction. This study sought to investigate the influence of retronasal olfaction on patient-perceived outcomes and examine the relationship between retronasal and orthonasal olfaction.

METHODS

Retronasal olfactory function was tested using odorized powders in the oral cavity, whereas Sniffin' Sticks test (Burghart Instruments, Wedel, Germany) were used to assess orthonasal function prospectively in 69 adult CRS patients. Endoscopic evaluation of the olfactory cleft was scored using the Olfactory Cleft Endoscopy Scale (OCES). Several quality-of-life (QOL) instruments relating to sinonasal, olfactory, and chemosensory functions were used to assess the interactions between patient-reported outcome measures and retronasal olfaction.

RESULTS

There was strong correlation between retronasal and total orthonasal olfaction scores (r = 0.77, P < 0.001) as well as retronasal scores with orthonasal subscores. Retronasal scores were worse in patients with nasal polyposis (P = 0.002), asthma (P = 0.04), and aspirin-exacerbated respiratory disease (AERD) (P = 0.02), whereas OCES was the only independent predictor of retronasal olfaction (r = -0.42, P < 0.001). Significant correlation existed between retronasal olfaction and olfactory-specific QOL and chemosensory smell scores.

CONCLUSION

Few studies have examined retronasal olfaction in CRS patients. In this cohort, CRS patients demonstrated deficits in retronasal olfaction, with worse scores in patients with nasal polyposis, asthma, and AERD. Retronasal olfaction scores correlate with degree of inflammation of the olfactory cleft. Retronasal olfaction correlated strongly with orthonasal olfaction and patient-reported smell and taste metrics, although orthonasal olfaction may have a stronger correlation with these metrics.

LEVEL OF EVIDENCE

NA. Laryngoscope, 2437-2442, 2018.

Retronasal Olfaction Test Methods: A Systematic Review

Background

This report produces a bibliographic study of psychophysical tests proposed clinical assessments of retronasal olfaction.

Aims

We review how these tests can be utilized and discuss their methodological properties.

Study Design

Systematic review.

Methods

We undertook a systematic literature review investigating the retronasal olfaction test methods. PubMed, the free online MEDLINE database on biomedical sciences, was searched for the period from 1984 to 2015 using the following relevant key phrases: “retronasal olfaction”, “orthonasal olfaction”, “olfaction disorders”, and “olfaction test”. For each of the selected titles cited in this study, the full manuscript was read and analyzed by each of the three authors of this paper independently before collaborative discussion for summation and analytical reporting. Two reviewers independently read the abstracts and full texts and categorised them into one of three subgroups as follow, suitable, not-suitable, and unsure. Then they cross-checked the results, and a third reviewer decided assigned the group “unsure” to either the suitable group or the not-suitable group. Fifty eight studies revealed as suitable for review by two authors whereas 13 found not suitable for review. The total amount of 60 uncertain (unsure) or differently categorized articles were further examined by the third author which resulted in 41 approvals and 19 rejections. Hence 99 approved articles passed the next step. Exclusion criteria were reviews, case reports, animal studies, and the articles of which methodology was a lack of olfaction tests. By this way excluded 69 papers, and finally, 30 original human research articles were taken as the data.

Results

The study found that the three most widely used and accepted retronasal olfaction test methods are the retronasal olfaction test, the candy smell test and odorant presentation containers. All of the three psychophysical retronasal olfaction tests were combined with orthonasal tests in clinical use to examine and understand the smell function of the patient completely. There were two limitations concerning testing: “the lack concentrations and doses of test materials” and “performing measurements within the supra-threshold zone”.

Conclusion

The appropriate test agents and optimal concentrations for the retronasal olfaction tests remain unclear and emerge as limitations of the retronasal olfaction test technique. The first step to overcoming these limitations will probably require identification of retronasal olfaction thresholds. Once these are determined, the concept of retronasal olfaction and its testing methods may be thoroughly reviewed.

Variability in Retronasal Odor Identification Among Patients With Chronic Rhinosinusitis

Background Retronasal olfaction is important in flavor detection and enjoyment. The ability to identify specific individual retronasal odors may play a role in quality of life for patients with chronic rhinosinusitis (CRS). Objective To identify patterns and improve understanding of retronasal identification of individual odors in CRS patients. Methods Patients diagnosed with CRS underwent retronasal and orthonasal (Sniffin' Sticks) olfactory testing and taste testing (taste strips). Retronasal identification was tested with presentation of flavored powders on the posterior tongue. Retronasal identification for individual odors was compared with results of orthonasal and taste testing. Results Seventy participants were evaluated. Retronasal identification correlated with orthonasal identification and discrimination for most individual odors. Among all patients, cinnamon and apple were identified better retronasally and banana better orthonasally ( P < .05). Anosmics identified retronasal orange, cinnamon, mushroom, coffee, smoked ham, peach, ginger, grape, and cheese more than would be expected by chance for a forced-choice paradigm with 3 distractor items ( P < .05), and this was independent of objective taste function for most odors. Conclusion Retronasal and orthonasal identification of most odors correlate in CRS patients; however, patients with anosmia can still identify certain retronasal odors more often than expected. These odors do not appear to stimulate gustatory pathways and may involve trigeminal stimulation. Understanding preserved retronasal neural stimuli may allow providers to improve eating-related quality of life in these patients.

Circadian anosmia: A rare clinical presentation

We report the case of a 27-year-old female who presented with a peculiar story of anosmia fluctuating in a circadian manner. Olfactory function appeared an hour after breakfast, was normal during daytime, and disappeared in the early evening. Imaging confirmed chronic rhinosinusitis (CRS). Initial systemic, followed by topical steroid treatment, rapidly and sustainably reversed this condition. The olfactory fluctuation paralleled the endogenous steroid production. This suggests that slight congestion changes in a chronically inflamed nasal mucosa may have been sufficient to induce this circadian anosmia. The importance of identifying fluctuation of olfactory function as a sign of CRS is emphasized and discussed. Laryngoscope, 128:1537-1539, 2018.

Influence of the location of nasal polyps on olfactory airflow and olfaction

BACKGROUND

Chronic rhinosinusitis with nasal polyps (CRSwNP) often results in decreased olfaction. In this study, we examined the relationship between nasal polyp location and olfactory airflow and odorant transport changes using virtual nasal polyp models at different locations and computational fluid dynamics (CFD) analysis. We also compared olfactory airflow and olfaction between patients with nasal polyps at different locations using CFD analysis and an olfactory test.

METHODS

Nasal computed tomography images were used to generate a normal model and 4 virtual nasal polyp models based on polyp locations, including the olfactory region (all-olfactory model), the region anterior to the olfactory region (preolfactory model), the middle meatus (middle-meatus model), and the superior meatus (superior-meatus model). Various airflow parameters were compared between these models and a normal model without polyps. We then performed a similar comparison between the 3-dimensional (3D) reconstruction models of patients with nasal polyps, and retrospectively investigated the correlation between olfaction and nasal polyp location in those patients.

RESULTS

Virtual nasal polyp analysis revealed dispersion of olfactory airflow in the all-olfactory model. Olfactory airflow and odorant transport showed maximum decrease in the preolfactory model and a slight decrease in the superior-meatus model. Olfactory airflow by polyps was further decreased by blockade of the olfactory airflow inlet than of the outlet. The findings obtained by patients corresponded well to those of the virtual polyp analysis.

CONCLUSION

Olfactory airflow and olfaction are differentially affected by nasal polyp location. This finding is important for planning polyp-removal surgeries from the perspective of improving patient olfaction.

Factors affecting the ortho- and retronasal perception of flavors: A review

Flavor perception is a highly individual sensation, and is impacted by a number of factors. Olfaction is a critical element in fully experiencing flavor. In this review, we explore the differences between orthonasal (sniff) versus retronasal (mouth) olfaction, and provide a comprehensive summary of recent publications in this arena. Here we explore the complexities of flavor perception, including the role that select flavors and media have on identification and localization. We also discuss some common neural imaging techniques used in this field, as odorants activate different neural responses in diverse areas of the brain, as well as the different stimulation patterns derived from perceiving food and nonfood related odorants. The information provided will be useful for sensory scientists and industry alike for the development of novel food and beverages that positively impact the consumer experience.

Neuron-specific enolase in nasal secretions as a novel biomarker of olfactory dysfunction in chronic rhinosinusitis

BACKGROUND

Olfactory dysfunction is a diagnostic criterion for chronic rhinosinusitis (CRS). During chronic inflammation and olfactory neuronal damage in CRS, it is likely that neuron-specific enolase (NSE) can leak into nasal secretions (NS) and serum. Therefore, we postulated that NSE levels in NS and in circulation may be indicative of olfactory dysfunction in CRS.

OBJECTIVE

To evaluate the relationship between the NS and serum concentrations of NSE with olfactory dysfunction in subjects with CRS.

METHODS

The patients with CRS were classified into two groups, depending on the presence of polyps: CRS without nasal polyps (CRSsNP) and CRS with nasal polyps (CRSwNP). A group of age- and sex-matched healthy volunteers served as controls. Olfactory function assessment was performed by using Sniffin' Sticks. NSE concentrations in serum and NS were analyzed by using the enzyme immunometric assay kit specific for the γ subunit.

RESULTS

The study included 46 patients with CRSsNP, 25 women (54.3%) and 21 men (45.7%), mean (standard deviation [SD]) age, 34.1 ± 12.3 years; and 54 patients with CRSwNP, 24 women (44.4%) and 30 men (55.6%), mean (SD) age, 37.9 ± 17.5 years. A group of 40 healthy volunteers who were matched for age and sex served as controls. Significantly higher serum and NS levels of NSE were measured in patients with CRS compared with healthy controls (p < 0.001). In the CRSwNP group, both mean (SD) serum (83.5 ± 37.6 ng/mL) and mean (SD) NS (6.1 ± 2.3 ng/mL) levels of NSE were significantly higher than in the CRSsNP group (46.4 ± 7.3 ng/mL [p < 0.001] and 1.7 ± 0.5 ng/mL [p < 0.001], respectively). In both the CRSsNP and CRSwNP groups (but not in the healthy controls), significant negative correlations between NS NSE levels and TDI scores (r = -0.63, p < 0.001 for the CRSwNP group, and r = -0.51, p < 0.001 for CRSsNP group) were observed, which meant that higher NSE was associated with worse olfactory function.

CONCLUSIONS

The study demonstrated a contribution of CRS to NSE and olfactory dysfunction.

Olfaction in Chronic Rhinosinusitis

Olfactory dysfunction is a frequent complaint in chronic rhinosinusitis patients and has a significant impact on quality of life. Therefore, it is essential that clinicians are aware of the importance of olfactory dysfunction in chronic rhinosinusitis (CRS) patients and know how to deal with it. Notably, the evaluation of olfactory function (i.e., using psychophysical testing) and imagery of olfactory bulb play an important role in the evaluation of patients and give essential information about the "baseline" olfactory function. Because the high impact of olfactory function on quality of life and medical and/or surgical treatment should be proposed to patients. However, it remains difficult to predict the outcome of treatment as well as long-term efficacy. The first section of this review is dedicated to the assessment of olfactory function. Secondly, we will discuss the etiopathology of olfactory dysfunction in CRS with and without nasal polyps. Finally, we will review literature findings about the efficacy of different treatments on olfactory function.

Evaluation of the olfactory bulb volume and olfactory threshold in patients with nasal polyps and impact of functional endoscopic sinus surgery: a longitudinal study

BACKGROUND

Debate still persists on the relation between olfactory bulb volume (OBV) and olfactory function. Many studies suggest that olfactory deprivation decreases the OBV. The aim of this study was to compare the olfactory threshold and OBV of patients with nasal polyps to healthy individuals and to evaluate the impact of functional endoscopic sinus surgery (FESS) on OBV and olfactory threshold.

METHODS

A longitudinal study was carried out in Tehran between 2011 and 2012. Twenty-two patients with nasal polyps were compared with 37 healthy individuals. Olfactory threshold test and magnetic resonance imaging (MRI) were performed on all participants. Twenty-two patients in case group were followed for 6 months after FESS. OBV and olfactory threshold were measured after 6 months.

RESULTS

There was no significant difference between the age, gender, and OBV of the 2 groups. However, the difference between olfactory threshold was significant (p = 0.005). The olfactory threshold showed no significant relation with OBV (p > 0.05). The correlation between Lund-Mackay score and the mean total OBV and left OBV was significant (r = -0.15, p = 0.045; r = -0.22, p = 0.047; respectively). The decrease in olfactory threshold measured after FESS was statistically significant. Right, left, and total OBV significantly increased after FESS.

CONCLUSION

The results of our study show that FESS has a significant impact on OBV increment and olfactory threshold decrement. The olfactory bulb is a plastic structure and improvement in peripheral olfactory function results in increase in OBV. However, further studies are mandated, in order to establish this result.

Effect of three-drug delivery modalities on olfactory function in chronic sinusitis

BACKGROUND

Olfactory dysfunction is deemed to be a significant contributor to poor quality of life in chronic rhinosinusitis (CRS).

OBJECTIVE

To assess and to compare the effectiveness of three modalities of corticosteroids administration in patients with CRS.

STUDY DESIGN

A prospective randomized controlled study

METHODS

Thirty patients with CRS were randomized in three groups depending on the route of corticosteroids administration: 16 days by oral route (Medrol (Pfizer, Belgique), 32 mg/8 days -16 mg/4 days-8 mg/4 days); nasal spray (Rhinocort (AstraZeneca, Belgique), 2 × 2 × 64 µg/nostril); or sonic nebulization (Pulmicort (AstraZeneca, Belgique), 2 × 1 mg/4 mL) (Sonic nebulizer, AOHBOX-NL11SN, DTF, France). Olfactory function was assessed using orthonasal threshold discrimination identification and retronasal psychophysical olfactory tests (RNT) before and after the treatment. Same intranasal modalities were previously tested for in vitro airways scintigraphic deposition.

RESULTS

In vitro differences in drug deposition pattern between both intranasal modalities were demonstrated. Threshold discrimination identification and RNT were similar between three groups at baseline. Threshold discrimination identification improved by 5.5, 5.8, and -1.1 for sonic nebulization, oral, and nasal spray groups, respectively (P = 0.010). This improvement was clinically relevant for oral and nebulized administration. It was similar between oral and nebulized administration but significantly higher than nasal spray administration. Retronasal psychophysical olfactory tests improved similarly for the three groups (P = 0.231) CONCLUSION: Effectiveness of sonic nebulized and oral administration is demonstrated on orthonasal olfactory. The clinical benefit is better than with nasal spray.

Tuning to odor solubility and sorption pattern in olfactory epithelial responses

Odor information is first represented as a spatial activation pattern across the olfactory epithelium, when odor is drawn into the nose through breathing. This epithelial pattern likely results from both the intrinsic olfactory sensory neuron (OSN) sensitivity and the sorptive patterns imposed by the interaction of nasal aerodynamics with physiochemical properties of odorants, although the precise contributions of each are ill defined. Here, we used a computational fluid dynamics (CFD) model of rat nasal cavity to simulate the nasal aerodynamics and sorption patterns for a large number of odorants, and compared the results with the spatial neural activities measured by electro-olfactogram (EOG) under same flow conditions. The computational and experimental results both indicate greater sorption and response to a narrow range odorants as a function of their mucosal solubility, and this range can be further modulated by changes of intranasal flow rates and direction (orthonasal vs retronasal flow). A striking finding is that the profile of intrinsic EOG response measured in surgically opened nose without airflow constraints is similar to the shape of the sorption profile imposed by nasal airflow, strongly indicating a tuning process. As validation, combining the intrinsic response with the mucosal concentration estimated by CFD in nonlinear regression successfully accounts for the measured retronasal and orthonasal EOG response at all flow rates and positions. These observations redefine the role of sorption properties in olfaction and suggest that the peripheral olfactory system, especially the central zone, may be strategically arranged spatially to optimize its functionality, depending on the incoming stimuli.

Conductive olfactory losses in chronic rhinosinusitis? A computational fluid dynamics study of 29 patients

BACKGROUND

Besides sensorineural factors, conductive impediments likely contribute to olfactory losses in chronic rhinosinusitis (CRS) patients, yet no conclusive evidence exists. We aimed to examine possible conductive factors using computational fluid dynamics (CFD) models.

METHODS

A total of 29 CRS patients were assessed via odorant detection thresholds (ODTs), rhinomanometry (nasal resistance [NR]), acoustic rhinometry (minimum-cross-sectional area [MCA]) and computed tomography (CT) staging. CFD simulations of nasal airflow and odorant absorption to olfactory region were carried out based on individual CTs. Biopsies of olfactory epithelium (OE) were collected, cryosectioned, stained, and scored for erosion.

RESULTS

Significant correlations to ODTs were found for 3 variables: odor absorption in the olfactory region (r = -0.60, p < 0.01), MCA (r = -0.40, p < 0.05), and CT staging (r = 0.42, p < 0.05). However, significant findings were limited to ODTs of the highly soluble l-carvone. Multiple regression analysis revealed that these variables combined, with the addition of NR, can account for 65% of the total variance in ODTs. CT staging correlated significantly with OE erosion (r = 0.77, p < 0.01) and can replace the latter in the regression with comparable outcomes. Partial correlations suggest the contributions of both conductive and sensorineural variables are more prominent if adjusted for the effects of the other. Olfactory loss and inflammatory factors have strong bilateral involvement, whereas conductive factors are independent between sides. As validation, CFD-simulated NRs significantly correlated with rhinomanometrically assessed NRs (r = 0.60, p < 0.01).

CONCLUSION

Both conductive and sensorineural mechanisms can contribute to olfactory losses in CRS. CFD modeling provides critical guidance in understanding the role of conductive impediments in olfactory dysfunction in CRS.

Retronasal perception of odors

We perceive odors orthonasally during sniffing; in contrast, we perceive odors retronasally during eating when they enter the nose through the pharynx. There are clear differences between orthonasal and retronasal olfaction in neuronal processing and perception, so that these two pathways convey two distinct sensory signals. The perception of foods is based on the interaction between ortho- and retronasal smell, taste, trigeminal activation and texture, so it is difficult to investigate one of these factors in isolation. Specific clinical aspects include effects of retronasal olfaction on satiation and swallowing.

The Candy Smell Test in clinical routine

BACKGROUND

The "Candy Smell Test" (CST) has been introduced as a new testing method for the evaluation of the human sense of smell. In contrast to other established orthonasal smell tests, the CST addresses the retronasal application of odors, typical for food aroma effects during mastication and swallowing. The aim of this study was to evaluate the CST in a clinical setting in patients with olfactory dysfunction and normal controls against the Sniffin' Sticks test. Furthermore, cutoff points for normal and pathological results in the CST should be determined.

METHODS

The olfactory performance of 96 patients presenting with olfactory disorders and 71 healthy controls was evaluated with the CST-comprised of 23 different aromatized smell candies and the extended Sniffin' Sticks test (threshold, discrimination, and identification). The control group was gender matched but included also younger persons.

RESULTS

The tested subjects could easily understand the procedures and were motivated to participate. The CST correlated well with the Sniffin' Sticks for all tested subjects and for patients (n = 96) and controls (n = 71). The proposed cutoff value to differentiate normosmia from hyposmia in the CST was a score of <16 (i.e., 16 correctly identified odors) of 23. A score below 13 in the CST was the cutoff value for anosmia.

CONCLUSION

The CST is an easy-to-handle reliable tool to investigate retronasal olfaction suited for clinical determination of normosmia, hyposmia, and ansomia. In addition, it can be used for investigation where self-application is necessary such as in large survey studies.

Olfactory and Gustatory Function in Patients with Multiple Sclerosis

Background

The olfactory function (OF) and gustatory function in patients with multiple sclerosis (MS) can be limited.

Methods

We performed the testing of orthonasal (Threshold Discrimination Identification [TDI] score with Sniffin’ Sticks) and retronasal (Taste Powder) OF and gustatory function (Taste Strips; Burghart, Wedel, Germany) in patients diagnosed with MS and healthy controls matching in age, sex, and smoking habits.

Results

Eight of 16 MS patients (50%) displayed hyposmia (TDI score, 28.75 ± 1.28; p = 0.06); the identification subtest significantly was restricted (12.63 ± 1.67; p = 0.001). Four of 16 MS patients (25%) had limited retronasal OF with a Taste Powder score of 4.5 ± 1.29. The gustatory function in 19% of MS patients was significantly limited (Taste Strip score, 5.33 ± 2.52; p = 0.02). Patients who estimated their ability to smell as diminished performed more poorly on retronasal OF testing (r = 0.657; p = 0.046).

Conclusion

This study confirms the incidence of olfactory disorder in MS patients that has been reported in the literature. Interestingly, a significant correlation between orthonasal and retronasal OF testing was not shown. A higher incidence of gustatory dysfunction was shown and might serve as another potential marker for this disease.

[Smell disorders as early diagnosis in the early stage of sinonasal polyposis]

INTRODUCTION

The increasing demand for attention to olfactory disorders, along with the persistent presence of sinonasal polyposis, has opened the need to treat these pathologies in very early stages.

OBJECTIVES

To demonstrate that incipient stages in sinonasal polyposis are detectable by olfactometry before radiological images, and that this detection is linked with a non-blocked area around the nasal meatus (where the olfactory cleft is located).

METHODS

This study is based on data obtained from a sinonasal polyposis (degree 0 or 1) patient group (n=121) without allergies or asthma backgrounds. The patients underwent both fibroscopic and olfactometry explorations (first and fifth cranial nerve) and computed axial tomography (CT) assessment. The results were compared with the control group (n=120).

RESULTS

Significant values (p<0.05) of affectation were found in decreasing olfactory levels (olfactory and trigeminal nerves) in patients with degree 0 or 1 polyposis.

CONCLUSION

Olfactory disorders linked to a non-blocked area around the nasal meatus (degree 1 or 2 polyposis), together with sinonasal CT scans showing beginnings of ethmoidal inflammation, should be interpreted as incipient sinonasal polyposis.

Chemosensory function in Wegener's granulomatosis: a preliminary report

Despite the fact that Wegener's granulomatosis affects the nasal and paranasal cavities and the cranial nerves regularly, chemosensory impairments have not been reported. The objective of this study is to test the three chemosensory systems, olfaction, taste, and intranasal trigeminal function in Wegener disease patients. We tested olfactory, gustatory, and intranasal trigeminal function in nine patients (5 women, 4 men, mean age 57 years) with confirmed Wegener's granulomatosis. Olfaction was tested with the Sniffin'Sticks, gustatory function with the "Taste strips" and intranasal trigeminal function with a lateralization task. One patient had anosmia (11%), four patients had hyposmia (44%) and four patients were normosmic (45%). Gustatory testing function showed pathological taste strip results in five patients (55%) and normal results in three patients (33%). One patient did not undergo taste testing. Intranasal trigeminal function was lowered in five patients (56%) and normal in four patients (44%). Neither previous nasal surgery status nor endoscopic status was associated to a higher frequency in pathological scores for any of the three chemical senses. In conclusion, these preliminary results suggest a consistent affection in chemosensory functions in Wegener's granulomatosis patients.

Retronasal olfactory function in Parkinson's disease

OBJECTIVES/HYPOTHESIS

Orthonasal olfaction is severely altered in PD patients. Retronasal olfactory function has been shown to be preserved under certain conditions even in the absence of orthonasal function. This study was undertaken to investigate retronasal versus orthonasal olfactory function in Parkinson's disease (PD).

STUDY DESIGN

Prospective study.

METHODS

A total of 45 PD patients (mean age, 61 years; range 26-82 years) underwent orthonasal olfactory testing with a standardized olfactory test (Sniffin' Sticks) and retronasal olfactory testing with a 10-item identification kit based on aromatized powders.

RESULTS

Regarding orthonasal tests, all PD patients scored within the range of hyposmia and functional anosmia. The mean correct orthonasal identification score for PD patients was 56% +/- 2.6%, and the mean retronasal identification rate was 60% +/- 3%. There was no significant difference between ortho- and retronasal odor identification (P = .15).

CONCLUSIONS

The present study shows that retronasal and orthonasal olfactory function are severely impaired in PD patients, and this impairment is of similar magnitude for both functions. The contribution of this finding to the food-intake behavior of PD patients is discussed.

Olfactory function and nasal nitric oxide

PURPOSE OF REVIEW

To highlight two often forgotten nasal functions, olfaction and nasal nitric oxide production, which have both received more attention over the last two decades with consequent findings that are now entering the routine clinical setting.

RECENT FINDINGS

Olfactory measurements have been optimized and normative data are available, giving clinicians the possibility of testing olfactory function quickly within a patient's workup. The results can lead to more thorough investigations if necessary. Olfactory disorders concern more than just a few people, and these disorders can be a very early sign of Parkinson's disease. Nasal nitric oxide is hypothesized to play a role as an airborne messenger and as an antiinfectious agent in the nose and sinuses and to contribute to the mucociliary clearance. Evidence is growing that the nasal nitric oxide level is a good parameter for diagnosis of ciliary beat impairments and a suitable parameter to monitor treatment success in chronic rhinosinusitis.

SUMMARY

Both nasal nitric oxide and olfactory function are worth testing routinely in any rhinology workup. Valuable clinical information for diagnostic and follow-up purposes can be gained.

Retronasal perception of odors

Odors often produce different sensations when presented in front of the nose or intraorally, when eaten. It is a long-standing question whether these differences in sensations are due, for example, to the additional mechanical sensations elicited by the food in the mouth or additional odor release during mastication. To study this phenomenon in detail, a stimulation technique has been developed that allows controlled ortho- or retronasal presentation of odorous stimuli. Results from psychophysical, electrophysiological, and imaging studies suggest that there are clear differences in the perception of ortho- and retronasal stimuli. This 'duality of the sense of smell' is also observed in a clinical context where some patients exhibit good retronasal olfactory function with little or no orthonasal function left, and vice versa. The differences between ortho- and retronasal perception of odors are thought to be, at least partly, due to absorption of odors to the olfactory epithelium, which appears to differ in relation to the direction of the airflow across the olfactory epithelium.