Correlations between gustatory, trigeminal, and olfactory functions and nasal airflow

PURPOSE

To determine the relationship of chemosensory screening and nasal airflow tests among the same set of participants, and to determine other factors that are related to the outcomes of these tests.

METHODS

Participants had no chemosensory complaints. Structured medical history was taken. Participants underwent 5 screening tests: q-sticks (orthonasal olfaction), q-powders (retronasal olfaction), trigeminal lateralization test, taste sprays, and peak nasal inspiratory flow (PNIF). Ratings of smell/taste ability and nasal airflow were obtained using visual analogue scales (VAS). Composite sinusitis symptoms and significance of olfaction questionnaire scores were also determined.

RESULTS

Four hundred participants were included in the study, 156 men, 244 women; aged 18-82 years (mean: 46). The q-powders and taste spray scores were weakly positively correlated with all the other chemosensory tests and PNIF. However, chemosensory test scores were not correlated with VAS, composite sinusitis symptoms, and significance of olfaction questionnaire scores. Various tests showed significant decrease starting at specific ages (in years, PNIF and trigeminal lateralization: 40, q-powders: 60, and q-sticks: 70).

CONCLUSION

Chemosensory screening tests and self-rated chemosensory function showed no correlation in participants without chemosensory complaints. In addition, gustatory function appeared to be correlated with olfactory and trigeminal function but also with nasal airflow, and nasal airflow was related not only to olfactory but also to trigeminal and taste function. Over all, the results suggest that chemosensory functions (orthonasal olfactory, trigeminal, retronasal olfactory, gustatory) and nasal airflow are correlated with each other, which we propose may be possibly mediated, at least in part, through central nervous system interactions.

Systematic review: Validity, reliability, and diagnostic accuracy of the electrogustometer

Objective

What are the electrogustometer's (EGM) validity, reliability, and diagnostic accuracy in assessing taste sensation in adults compared to other taste tests?

Data Sources

PubMed Medline, Elseviers's Embase, and the six databases of Cochrane Library.

Methods

We conducted a systematic search on December 20, 2022, consisting of synonyms for EGM. We considered randomized controlled trials and observational studies with original data for inclusion if they included adults who underwent electrogustometry. Articles were excluded if no analysis regarding validity, reliability, or diagnostic accuracy had been performed or if these analyses could not be performed with the published data.

Results

Nineteen articles discussing 18 studies were included for data extraction. The included studies carry a high risk of bias. Overall, the association between a variety of reference taste tests and EGM was moderate or weak with correlation coefficients ranging from -0.51 to 0.40 with one outlier of -0.74 found in one study correlating EGM and taste solutions. Test-retest reliability was good with reported correlation coefficients between 0.78 and 1.0. The sensitivity, specificity, PPV, and NPV of EGM in identifying abnormal taste function varied widely between the four studies on diagnostic accuracy.

Conclusion

The included studies in this review lack the required standards regarding study design to draw firm conclusions about the validity, reliability, and diagnostic accuracy of the EGM. Future research is needed to assess these measurement properties. Based on the reported results, we would not recommend using the EGM as a screening test for taste disturbance in clinical practice.

Level of Evidence

NA.

Visualization of the relationship between electrogustometry and whole mouth test using multidimensional scaling

Interpreting the relationship between different taste function tests of different stimuli, such as chemical and electrical stimulation, is still poorly understood. This study aims to analyze visually as well as quantitatively how to interpret the relationship of results between taste function tests using different stimuli. Patients who underwent the whole mouth test and Electrogustometry (EGM) at a tertiary medical center between August 2018 and December 2018 were reviewed retrospectively with electronic medical records. Of the 110 patients, a total of 86 adults who self-reported that their taste function was normal through a questionnaire were enrolled. EGM measured the thresholds of the chorda tympani (CT) and glossopharyngeal nerve (GL) area of the tongue. The whole mouth test measured detection and recognition thresholds for sweet, salty, bitter, sour, and umami taste. Statistical analyses of Pearson's, Spearman's rank and polyserial correlation and multidimensional scaling (MDS) was performed. The EGM threshold for the average value of both CT regions and the recognition threshold of the whole mouth test were significantly correlated in sweet, salty, bitter, and sour taste (r = 0.244-0.398, P < 0.05), and the detection threshold was correlated only significant in sweet (r = 0.360, P = 0.007). In the MDS analysis results, the three-dimensional (D) solution was chosen over the 2-D solution because of the lower stress. Detection-, recognition threshold of whole mouth test and EGM thresholds of CT and GL area, those were standardized by Z-score, formed well-distinguished sections in the MDS analyses. The EGM threshold of the CT area was closer to the detection and recognition thresholds than the EGM threshold of the GL area. In general, the EGM threshold was closer to the recognition threshold than the detection threshold for each taste. Overall, visualization of the relationship of whole mouth test and EGM by MDS was in good agreement with quantitative analysis. EGM and whole mouth test seem to reflect different aspects of taste. However, when interpreting the EGM results, the EGM threshold of the CT area will show more similarity to the recognition threshold than the detection threshold for the whole mouth test.

Gustatory dysfunction perceptions versus objective gustatory dysfunction among older adults

BACKGROUND

Research on gustatory dysfunction among older adults has been scarce relative to research on olfactory dysfunction, and the relationship between subjective and objective gustatory dysfunction has not been studied in detail. We aimed to evaluate whether subjective recognition of gustatory dysfunction correlates with objective diagnosis of gustatory dysfunction among older adults.

METHODS

In this retrospective, cross-sectional study, we reviewed the medical records of 138 patients of ages ≥ 60 years for whom data were available on self-reported and objectively measured gustatory and olfactory function from January 2018 through April 2021 at a specialized smell/taste center of a single institution. We reviewed self-reported and measured outcomes of gustatory and olfactory function using patient data including clinical characteristics, including age, sex, smoking history, and medical history.

RESULTS

We found that the subjective recognition of gustatory dysfunction does not correlate with the objective diagnosis of gustatory dysfunction based on the measured results of gustatory function tests. Subjective gustatory dysfunction, however, was correlated with subjective olfactory dysfunction. Among clinical and demographic characteristics, age and sex were significantly associated with measured gustatory function outcomes.

CONCLUSION

We suggest that subjective gustatory dysfunction underestimates objective dysfunction and recommend that older men with diminished olfactory function undergo gustatory function testing regardless of their self-reported gustatory function status.

[Analysis of clinical characteristics in the patient with olfactory disorders]

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

Persisting olfactory dysfunction in post-COVID-19 is associated with gustatory impairment: Results from chemosensitive testing eight months after the acute infection

Olfactory and gustatory disorders are prominent symptoms of acute COVID-19. Although both senses recover in many patients within weeks to months, persistency has been described in up to 60%. However up to now most reports on the course of chemosensitive disorders after COVID-19 are not based on psychophysical testing but only on subjective patients' ratings. In this study we assessed both olfaction and gustation using psychophysical tests eight months after COVID-19. Validated psychophysical testing revealed hyposmia in 18% and hypogeusia in even 32% of 303 included patients. This shows that olfactory and especially gustatory disorders have to be seen as important chronic symptoms post-COVID-19. The high prevalence of gustatory dysfunction indicates that gustatory function does not recover or might even deteriorate in the months following the acute infection.

The taste of the pandemic-contemporary review on the current state of research on gustation in coronavirus disease 2019 (COVID-19)

Subjectively perceived impairment of taste is a common and distinct symptom of coronavirus disease 2019 (COVID-19). Large meta-analyses identified this symptom in approximately 50% of cases. However, this high prevalence is not supported by blinded and validated psychophysical gustatory testing, which showed a much lower prevalence in up to 26% of patients. This discrepancy may be due to misinterpretation of impaired retronasal olfaction as gustatory dysfunction. In addition, we hypothesized that COVID-19-associated hyposmia is involved in the decrease of gustatory function, as found for hyposmia of different origin. This indirect mechanism would be based on the central-nervous mutual amplification between the chemical senses, which fails in COVID-19-associated olfactory loss. However, further research is necessary on how severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) may directly impair the gustatory pathway as well as its subjective perception.

The Etiologies and Considerations of Dysgeusia: A Review of Literature

BACKGROUND

Dysgeusia is a prevalent qualitative gustatory impairment that may affect food intake and quality of life. The facial (VII), glossopharyngeal (IX), and vagus (X) nerves are the three cranial nerves responsible for sensing taste. Typically, dysgeusia is considered a general term for all taste disorders. In addition, dysgeusia may be a symptom of underlying systemic conditions such as diabetes mellitus, chronic kidney disease, respiratory infections, and nutritional deficiencies. Various subjective and objective diagnostic approaches are available to aid clinicians, each with its own set of benefits and drawbacks.

HIGHLIGHTS

Taste impairment can lead to a lack of enjoyment while eating, food aversion, and malnutrition, resulting in a decrease in the quality of life and loss of muscle mass. Therefore, the present review aims to address the probable etiologies, diagnostic aids, and management of dysgeusia. A broad search for studies was conducted using PubMed, Web of Science, Scopus, and Google Scholar. In addition, relevant studies found in the references of the selected articles were also studied.

CONCLUSION

Oral health care providers should be aware of the possible etiologies of dysgeusia, diagnostic tools, and treatment options. Accurate diagnosis of the cause of taste dysfunction has a significant impact on the management of taste impairment.

Oral Somatosensory Sensitivity in Patients With Taste Disturbance

OBJECTIVE

The significance of the human sense of taste is typically underestimated until it is altered or even lost. Hypogeusia, a diminished capacity to taste, has an adverse influence on a patient's quality of life. Similar to interactions between the oral senses and between olfaction and intranasal trigeminal sensitivity, taste disturbance may also affect the mechanosensitivity of the tongue. In this study, we investigated the lingual tactile sensitivity of patients with subjective taste disturbance and people with normogeusia.

STUDY DESIGN

Prospective case-control study.

METHODS

Forty-six patients with subjective taste disturbance (mean age 60 years) and 43 participants with normogeusia (mean age 55 years) were enrolled and underwent a stereognostic test of edge and point sensitivity based on 3D-printed letters sized from 2 to 8 mm. Gustatory function and salivary production were also tested.

RESULTS

Patients with dysgeusia needed significantly bigger letters to recognize them compared with controls (P = .01). Apart from this, patients with dysgeusia had no significant association between gustatory function and salivary production. Duration of dysgeusia and age were not associated with the presently obtained measures of gustatory or oral mechanosensory function.

CONCLUSIONS

The results of this study indicate that taste dysfunction has a negative impact on oral mechanosensitivity and hence possibly on oral texture perception.

LEVEL OF EVIDENCE

3 Laryngoscope, 131:2572-2577, 2021.

Assessment of Taste Function

Taste disorders, impacting well-being and physical health, can be caused by many etiologies including the use of medication. Recently, taste disturbance is also considered as one of the predominant symptoms of COVID-19 although its pathogenesis requires further research. Localized taste disorders may be overlooked considering that whole-mouth taste perception is insured through several mechanisms. Individuals often fail to discern taste from flavor, and interviews/surveys are insufficient to properly assess taste function. Hence, various taste assessment methods have been developed. Among them, psychophysical methods are most widely applied in a clinical context. Less-biased electrophysiological, imaging, or morphological methods are used to a much lesser degree. Overall, more research is needed in the field of taste.

Symptoms of Depression in Patients with Chemosensory Disorders

INTRODUCTION

Patients with chemosensory dysfunction frequently report symptoms of depression. The current study aims to clarify whether the type (smell dysfunction, taste dysfunction, and mixed smell and taste dysfunction), severity, duration, or cause of dysfunction have differential impacts on the symptoms of depression.

METHODS

899 patients with chemosensory disorders and 62 controls were included. Following a structured interview and an otorhinolaryngological examination, subjects underwent olfactory tests (Sniffin' Sticks), gustatory tests (taste sprays) and an assessment of depressive symptoms (Beck Depression Inventory). Information on the cause and duration of disorders was also collected.

RESULTS

Patients with combined olfactory/gustatory dysfunction had higher depression scores than patients with smell dysfunction only and controls, and no significant difference was found between the smell dysfunction and controls. Anosmia patients, but not hyposmia patients, exhibited higher depression scores than controls. Among various causes of chemosensory disorders, patients from the posttraumatic group had higher depression scores than patients with other causes of chemosensory dysfunction (sinonasal, idiopathic, or postinfectious). Multiple linear regression analyses suggested that reduced olfactory function was associated with enhanced depression scores in the olfactory disorders group (B = -0.326, t = -2.294, and p = 0.02) and in all patients with chemosensory disorders (B = -0.374, t = -2.550, p = 0.017).

DISCUSSION/CONCLUSION

Simultaneously decreased input of olfaction and gustation seems to have an additive effect on the exacerbation of emotional dysfunction. Early intervention should be considered for depression symptoms in patients with mixed olfactory/gustatory dysfunction in clinical practice.

Self-perceived Taste and Flavor Perception: Associations With Quality of Life in Patients With Olfactory Loss

OBJECTIVE

To evaluate associations between self-perceived chemosensory functions of smell, taste, and flavor perception with olfactory-specific quality of life (QoL) in patients with olfactory dysfunction (OD) and whether these associations would be influenced by other factors, such as duration or etiology of smell loss.

STUDY DESIGN

Retrospective cohort study.

SETTING

Tertiary care, academic center.

METHODS

Olfactory-specific QoL was measured with the Questionnaire of Olfactory Disorders (QOD). The QOD measures the impact of OD on QoL (QOD-negative statements) and the ability of patients to cope with smell loss (QOD-positive statements). Orthonasal olfactory function, patients' demographics, self-perceived chemosensory perception, and duration and etiology of OD were retrospectively collected in a cohort of patients with quantitative OD. Correlations and multivariable linear regression models were computed to determine possible associations with the outcome measure of QOD-negative and QOD-positive statement scores.

RESULTS

A total of 133 patients with OD were included. Analysis revealed a positive correlation between self-perceived taste and flavor perception with QOD-negative statement scores, while self-perceived smell showed no significant correlation. Similarly, longer duration of smell loss and higher age were also correlated with higher QOD-positive statement scores. Multivariable regression models confirmed that self-perceived taste was independently associated with the QOD-negative statement score, while age and duration of OD were independently associated with the QOD-positive statement score.

CONCLUSIONS

These findings suggest that the impact of diminished flavor perception during eating and drinking has a stronger impact on the QoL of patients with OD as compared with decreased orthonasal olfaction.

Psychophysical evaluation of chemosensory functions 5 weeks after olfactory loss due to COVID-19: a prospective cohort study on 72 patients

Purpose

To evaluate the evolution of chemosensation via extended psychophysical testing in patients who suffered from sudden chemosensory loss due to coronavirus disease 2019 (COVID-19). Additionally, this study sought to determine whether odor threshold testing provided additional information on olfactory loss due to COVID-19 compared to the more common odor identification testing.

Methods

Prospective cohort study of patients with sudden chemosensory loss since February 2020 and confirmed COVID-19 infection via RT-PCR or serology testing. Olfactory function was tested extensively using the “Sniffin Sticks” test battery. In addition, we screened gustatory perception and nasal cooling sensations using psychophysical tests.

Results

Seventy-two patients completed the study. After a mean of 37 days, 37% of patients showed olfactory dysfunction, 7% were dysgeusic, and 48% showed signs of low sensitivity for cooling sensation. A longer duration of anosmia before smell improvement was correlated with lower olfactory function at 5 weeks. Odor threshold detection was more affected by COVID-19 compared to odor identification.

Conclusion

Five weeks after developing sudden chemosensory loss due to COVID-19, a high proportion of patients were dysosmic and showed signs of low nasal cooling sensitivity, whereas most of them had normal taste function. SARS-CoV-2 affected mainly odor thresholds, possibly suggesting that the major cause of loss of smell lies at the level of the olfactory neuroepithelium, rather than in the central nervous system.

Chemical, Electrical and Tactile Sensitivity Changes After Middle Ear Surgery

OBJECTIVE/HYPOTHESIS

Taste disturbances are often seen in patients after middle ear surgery due to the stress received by an unprotected chorda tympani. It has also been reported that loss in tactile sensitivity may accompany this issue. The current study was designed to measure electrical, chemical, and tactile sensitives of several senses involved in oral processing, smell, taste and touch, over time.

STUDY DESIGN

Prospective cohort study.

METHODS

For three time points, one before middle ear surgery and two after operation (about 5 and 23 days), sensitivity thresholds were obtained using electrogustometry (electrical taste), taste strips (chemical taste), Sniffin' Sticks (smell) and Von Frey Hairs (point-pressure tactile sensitivity).

RESULTS

The results show a decline in both chemical and electrical taste responses. Additionally, the electrical taste response showed more sensitivity to deviations and no sign of recovery unlike the chemical taste response. Mechanosensory function of the anterior tongue and olfactory function was not strongly affected by middle ear surgery.

CONCLUSION

Taste responses, but not mechanosensory or olfaction function, are altered after middle ear surgery. Due to the effects that taste loss has on quality of life, gustometry is recommended for this group of patients.

LEVELS OF EVIDENCE

4.