Prevalence and assessment of qualitative olfactory dysfunction in different age groups

Parosmia: Pathophysiology and Management

PURPOSE OF REVIEW

Parosmia is a qualitative olfactory disorder in which there is a mismatch between the memory of an odor and the actual experience triggered by an odor. There has been a surge in parosmia-related publications since the COVID-19 pandemic. This review summarizes the latest clinical findings, theories on pathophysiology and potential treatment options.

RECENT ADVANCES

Potential models of parosmia include peripheral or central hypotheses, which refer to aberrancies in olfactory neuron regeneration or information processing in central olfactory centers respectively. This leads to an incomplete or disorganized pattern of olfactory information relay. Studies using gas chromatography and functional magnetic resonance imaging have identified molecular triggers and intracranial functional connectivity patterns in parosmia respectively. Parosmia tends to occur in a delayed fashion after virus-induced anosmia. It may run a protracted course, but typically improves over time. Currently there are no generally approved, objective ways to ascertain the presence and measure the extent of parosmia. Evidence-based treatment for parosmia remains elusive. In some people, this can lead to health and quality of life issues.

Trends in Olfactory Threshold Test Results and Limits of Olfactory Testing in Patients with Parosmia

INTRODUCTION

Parosmia poses a clinical challenge due to a lack of established testing methods, leading to underestimated self-reported symptoms. This study investigated olfactory threshold trends, aiming to highlight parosmia prevalence, analyze threshold patterns, and assess diagnostic potential in current olfactory testing.

METHODS

A total of 407 patients who visited our olfactory clinic from April 2009 to September 2015 were categorized into parosmia and non-parosmia groups based on initial visit questionnaires. The Jet Stream T&T Olfactometer measured olfactory thresholds, including mean detection and recognition thresholds, and the left-right detection threshold difference. Patient characteristics such as gender, age, time from symptom onset to hospital visit, and smoking status were compared. The study also aimed to diagnose parosmia with olfactory identification ability tests such as Open Essence and the gap between T&T detection and recognition thresholds.

RESULTS

Parosmia prevalence was 18%, with a significant gender difference and a shorter onset-to-visit duration in the parosmia group. Post-traumatic and post-infectious olfactory dysfunctions exhibited higher parosmia prevalence. Olfactory threshold testing revealed significantly lower average detection (p = 0.014) and recognition (p = 0.005) thresholds in the parosmia group, with a left-right difference in detection thresholds (p = 0.012). No significant differences were found in identification ability tests. Results suggest that preserved sense of smell is crucial for perceiving parosmia symptoms.

CONCLUSION

Parosmia was observed in 18% of patients, more commonly among females and often following trauma or infection. It presents diagnostic challenges as patients tend to maintain olfactory thresholds, making subjective assessments essential for diagnosis. The significant left-right differences in detection thresholds suggest that olfactory lateralization may play a role in the manifestation of parosmia symptoms. Our findings suggest that a unilateral occlusion test, which identifies which nostril is more likely to cause parosmia, could allow for more targeted treatment.

Parosmia in patients with post-infectious olfactory dysfunction in the era of COVID-19-associated olfactory impairment

OBJECTIVES

A large number of patients with olfactory impairment are affected by parosmia or phantosmia. This study aimed to examine the demographic and clinical characteristics of parosmia.

METHODS

We performed a retrospective data analysis of patients consulting at our Smell and Taste Outpatient Clinic. A total of 297 patients were included (203 women, mean age 44.4 ± 13.7 years). Olfactory function was quantified using the "Sniffin' Sticks" composite TDI (odor threshold, determination, and identification) score. The presence of qualitative olfactory impairment was assessed trough medical history and a parosmia questionnaire.

RESULTS

Most of the patients showed olfactory impairment after an infection with SARS-CoV‑2 (84%) and were diagnosed with parosmia (49%). Patients with parosmia (PAR) (n = 201) were significantly younger compared to the group without parosmia (noPAR; n = 92) (PAR 43.2 ± 13 years vs. noPAR 47 ± 15.1 years, p = 0.03) and had a slightly shorter duration of disease, without reaching statistical significance (PAR 10.3 ± 4.9 months, noPAR 13.6 ± 37.6 months, p = 0.23). They also had higher TDI scores (PAR 24.3 ± 7 points, noPAR 21.4 ± 8.2 points, p = 0.003).

CONCLUSIONS

Patients affected by parosmia were younger and had a better olfactory function compared to patients without parosmia.

Comparison of Patient Characteristics and Olfactory Sensitivity for Trigger Odorants in Parosmia and Phantosmia

OBJECTIVES

This study aimed to determine the characteristics of patients with qualitative olfactory dysfunction (qualOD) and whether individuals with parosmia exhibit increased olfactory sensitivity to previously reported odorous triggers of parosmia.

METHODS

This study included individuals aged ≥18 years, divided into quantitative OD only, parosmia, and phantosmia groups. Data collected included: clinical-demographic data, "Sniffin' Sticks" scores, questionnaires (depression scale, importance of olfaction), and information about parosmia and phantosmia. A proportion of patients underwent trigger odor threshold testing for 2-Furfurylthiol [FFT] found in coffee and 2,6-nonadienal [Nonadienal] found in cucumber.

RESULTS

Those with parosmia were typically younger women, with shorter OD duration due to post-viral OD (PVOD), hyposmic/normosmic, and experienced parosmia more severely. Parosmia was 3.5 times more likely in PVOD. Those with phantosmia were older, with longer OD duration due to idiopathic OD, hyposmic/anosmic, and experienced phantosmia less severely. There were no significant differences between FFT and Nonadienal threshold scores in patients with parosmia, phantosmia, or only quantitative OD, but all groups had significantly increased olfactory sensitivity for trigger odors compared to phenyl ethyl alcohol (PEA).

CONCLUSION

Parosmia and phantosmia patients have distinct characteristics. This may provide clinicians with a better understanding of possible olfactory outcomes in these patients. The higher olfactory sensitivity of all groups to trigger odors compared to PEA raises interesting points about parosmia triggers and odors in the context of warning for danger, in relation to the pathophysiology of parosmia that may be worth exploring in future studies.

LEVEL OF EVIDENCE

3 Laryngoscope, 134:3277-3285, 2024.

Olfactory function assessment of migraine patients by using the Sniffin' sticks test: A clinical study

OBJECTIVE

This as a cross-sectional controlled clinical study. We hypothesis that the olfactory functions in migraine patients may differ from the healthy controls. In this study, we evaluated the olfactory functions by using a Sniffin' Sticks test battery, which is a reliable and semi quantitative test to evaluate for olfactory dysfunction.

METHODS

Patients above 18 years of age who had migraine received a definitive diagnosis of migraine from experienced headache specialists based on the criteria of The International Classification of Headache Disorders-3 were included. Odor threshold, discrimination, and identification parameters were assessed using the "Sniffin' Sticks" test.

RESULTS

One-hundred and one migraine patients (age [mean ± SD], 36.9 ± 10.4 years; range, 18-60 years) and sixty healthy volunteers (age 34.5 ± 13.2 years, range 18-65 years) participated in our study. The median odor threshold score [percentiles 25th-75th] was 8.3 [6.5-9.8] for the migraine group during attack free period and 4.5[3.6-6.0] for the control group. It was found that the migraine group had a median odor discrimination score of 10.0 [10.0-13.0] and the control group 12.0 [11.0-13.0]. These differences were statistically significant (p < 0.001 and p = 0.032 respectively). The median odor discrimination and identification scores were statistically significant higher for the participants with higher educational level group than in those of lower educational group (p < 0.0001). The median odor discrimination and identification scores of those without allodynia (12.0 [10.0-14.0] and 13.0 [10.0-13.0] respectively) were higher than that of those with allodynia (11.0 [9.0-12.0] and 11.0 [10.0-13.0] respectively) (p = 0.037 and p = 0.034 respectively).

CONCLUSIONS

We found that the odor thresholds, discrimination and identification scores of the migraine group demonstrate differences from those of the healthy group and in relation to allodynia.

Olfactory Function and Olfactory Disorders

The sense of smell is important. This became especially clear to patients with infection-related olfactory loss during the SARS-CoV-2 pandemic. We react, for example, to the body odors of other humans. The sense of smell warns us of danger, and it allows us to perceive flavors when eating and drinking. In essence, this means quality of life. Therefore, anosmia must be taken seriously. Although olfactory receptor neurons are characterized by regenerative capacity, anosmia is relatively common with about 5 % of anosmic people in the general population. Olfactory disorders are classified according to their causes (e. g., infections of the upper respiratory tract, traumatic brain injury, chronic rhinosinusitis, age) with the resulting different therapeutic options and prognoses. Thorough history taking is therefore important. A wide variety of tools are available for diagnosis, ranging from short screening tests and detailed multidimensional test procedures to electrophysiological and imaging methods. Thus, quantitative olfactory disorders are easily assessable and traceable. For qualitative olfactory disorders such as parosmia, however, no objectifying diagnostic procedures are currently available. Therapeutic options for olfactory disorders are limited. Nevertheless, there are effective options consisting of olfactory training as well as various additive drug therapies. The consultation and the competent discussion with the patients are of major importance.

Parosmia as a predictor of a better olfactory function in COVID-19: a multicentric longitudinal study for upper respiratory tract infections

PURPOSE

This study aimed to evaluate the course of olfactory dysfunction [OD] due to upper respiratory tract infections [URTI] especially for COVID-19 [C19] in a multicentric design and to investigate possible predictors for the outcome.

METHODS

In a multicentric study, patients (n = 147, of which 96 were women) with OD due to URTI, including C19 and non-C19 were evaluated at two visits with a standardized medical history and "Sniffin' Sticks" extended psychophysical testing to examine the course and possible predictors for improvement of olfactory function.

RESULTS

C19 patients showed better overall olfactory function (p < 0.001) compared to non-C19. Olfactory function (p < 0.001) improved over 3.5 ± 1.2 months in a comparable fashion for C19 and non-C19 comparable over time (p = 0.20) except for a more pronounced improvement of odour threshold (p = 0.03) in C19. C19 patients with parosmia exhibited a higher probability of clinically relevant improvement of odour threshold, a better threshold in the second visit, and tended to have a better TDI-score at the second visit. Further possible predictors for an improving olfactory function were younger age, female gender, and had lower scores in olfactory tests at the first visit.

CONCLUSIONS

Patients with C19 and non-C19 URTI exhibit a similar improvement over 3-4 months except for the odour threshold, with a better TDI in both visits for C19. For C19 a better prognosis in terms of olfactory recovery was found for younger patients with parosmia and lower olfactory scores at the first visit. Still, for many patients with olfactory loss, an improvement that is experienced as complete may only occur over months and possibly years.

Phantom smells: a prevalent COVID-19 symptom that progressively sets in

PURPOSE

One of the long-term symptoms of COVID-19 is phantosmia, a type of Olfactory Disorder (OD) that has deleterious impacts on patients' quality of life. The aim of this article was to study how this poorly understood qualitative OD manifests itself in the COVID-19.

METHODS

4691 patients with COVID-19 responded to our online questionnaire focusing on COVID-19-related OD. We first analyzed the prevalence of phantosmia in this population. Then, with the help of Natural Language Processing techniques, we investigated the qualitative descriptions of phantom smells by the 1723 respondents who reported phantosmia.

RESULTS

The prevalence of phantosmia was of 37%. Women were more likely to report phantosmia than men, as well as respondents for whom OD was described as fluctuating rather than permanent, lasted longer, was partial rather than total and appeared progressively rather than suddenly. The relationship between OD duration and phantosmia followed a logarithmic function, with a prevalence of phantosmia increasing strongly during the first 2 months of the disease before reaching a plateau and no decrease over the 15 months considered in this study. Qualitative analyses of phantosmia descriptions with a sentiment analysis revealed that the descriptions were negatively valenced for 78% of the respondents. Reference to "tobacco" was more frequent in non-smokers. Source names and odor characteristics were used differently according to age and OD duration.

CONCLUSION

The results of this descriptive study of phantosmia contribute to the current efforts of the medical community to better understand and treat this rapidly increasing COVID-19-related OD.

Headache-Associated Phantosmia as a Harbinger of Lewy Body Dementia

Olfactory hallucinations, or phantosmias, can occur in many neurological, psychiatric, and medical conditions, but no widely used standardized approach exists to comprehensively assess qualitative olfactory dysfunction in the clinical setting. Additionally, medical professionals, patients, and their family members may not recognize phantosmia as a potentially neurological problem. Given the many possible etiologies for symptomatic phantosmia, it is important to recognize this unusual presentation and elicit a meaningful history to explore the potential underlying cause. We describe a 77-year-old gentleman with a two-year history of headaches accompanied by smelling a foul odor and discuss the differential diagnosis for new onset and persistent phantosmia. This unusual case ultimately manifested features consistent with Lewy body dementia, highlighting the varied clinical presentations that are possible with this neurodegenerative disorder. We discuss the possible pathophysiology of phantosmia in Lewy body disorders, including a proposed mechanism for olfactory hallucinations arising prior to the typical well-formed hallucinations in Lewy body dementia.

Olfactory distortions in the general population

Parosmia, distorted smell sensations, is a common consequence of respiratory virus infections. The phenomenon is not well understood in terms of its impact and long-term outcomes. We examined self-reported experiences of parosmia in a population-based sample from the Betula study that was conducted in Umeå in northern Sweden (baseline data collected in 1998–2000). We used a baseline sample of 2168 individuals aged 35–90 years and with no cognitive impairment at baseline. We investigated the prevalence of parosmia experiences and, using regression analyses, its relationship to other olfactory and cognitive variables and quality of life. Benefitting from the longitudinal study design, we also assessed the persistence of parosmia over 5 and 10 years prospectively. Parosmia experiences were prevalent in 4.8% of the population and it often co-occurred with phantosmia (“olfactory hallucinations”), but was not associated with lower self-rated overall quality of life or poor performance on olfactory or cognitive tests. For some individuals, parosmia was retained 5 years (17.0%) or even 10 years later (10.3%). Thus, parosmia experiences are commonly reported in the population, and can be persistent for some individuals, but might be mostly benign in nature. Our work complements research on clinical-level parosmia, which is typically more severe, and recent parosmia reports during the COVID-19 pandemic, where long-term outcomes are still unknown.

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.

[Smell and care: from professionalism to emotions]

The sense of smell presents itself to us as a means of forging an opinion of a situation, sending us back to our memories and giving us a form of knowledge of the patient. In addition, besides the obvious repulsion that certain wounds can engender, the sense of smell can also, conversely, lead us into an eroticization of care.

Olfaction in COPD

BACKGROUND

Olfaction is poorly characterized in COPD. To test the hypothesis that olfaction is reduced in COPD, we assessed olfaction with the "Sniffin' Sticks" test and a questionnaire addressing olfaction in COPD and a corresponding control group in respect to age and sex. We also explored whether there is an association between COPD, chronic rhinosinusitis without nasal polyps (CRSsNP), and other predefined covariates with olfactory function.

METHODOLOGY

Olfactory function was assessed by the score for threshold (T), discrimination (D) and identification (I), and the composite TDI score in the "Sniffin' Sticks" test and by self-reported evaluation of impaired olfaction and of "decreased sense of smell and taste" in the 22-item Sino-Nasal Outcome Test (SNOT-22) in 90 COPD patients and 93 controls. A clinical interview and ENT-examination with nasal endoscopy, skin prick test and spirometry with reversibility were performed.

RESULTS

The TDI, D and I scores were significantly lower in the COPD group than in the control group. The T score was not significantly different between the two groups. Hyposmia and anosmia were present in up to 79% of patients with COPD. The prevalence of self-reported impaired olfactory function and for "decreased sense of smell and taste&quot; - was more than two-fold greater in the COPD than in the control group. COPD, higher age, male sex and allergy were associated with a lower TDI score, while CRSsNP was not associated with the TDI score.

CONCLUSIONS

COPD is associated with olfactory dysfunction and the underlying mechanisms for this dysfunction should be elucidated.

Olfactory hallucinations in a population-based sample

Olfactory hallucinations referring to olfactory perceptions in the absence of chemical stimuli, occur in non-clinical and clinical populations. Few studies have investigated their prevalence in the general population and little is known about factors triggering and maintaining them such as substance use, severe life events, and mood. We analyzed self-report data from 2500 community dwelling Norwegians, aged 18-96 years, for occurrence of olfactory hallucinations and co-occurring hallucinations in other modalities (auditory, visual, tactile). Analyses included age, sex, self-reported symptoms of depression and anxiety, mental health status, and experience of severe life-events. The results show that 4.2% (95% CI 3.5-5.1%) reported having experienced olfactory hallucinations, and 56% of individuals experiencing olfactory hallucinations also reported these in combination with hallucinations in other modalities. Prevalence varied significantly in terms of age and sex, in that olfactory hallucinations were most frequently reported by young individuals and females. Self-reported symptoms of anxiety and experience of stressful life events were significantly associated with olfactory hallucinations, suggesting that experiencing olfactory hallucinations may negatively affect functioning and may increase the likelihood of developing psychopathology. Findings underline the need to continue to examine olfactory hallucinations albeit with a more comprehensive assessment in order to increase knowledge on this experience.

Clinical assessment of olfactory function

Approximately 5% of the general population is affected by functional anosmia with approximately additional 15% exhibiting decreased olfactory function. Many of these individuals ask for help. Because the subjective rating of olfactory function is biased, assessment of olfactory function is important. Olfactory measurements are needed for patient counseling and the tracking of changes in the sense of smell over time. The present review provides an overview of frequently used psychophysical tests for olfactory function, discusses differences between threshold and suprathreshold aspects of olfactory function, and gives examples on how to apply psychophysical tests.

Prevalence and correlates of parosmia and phantosmia among smell disorders

Among those many individuals who experience a reduced odor sensitivity (hyposmia/anosmia), some individuals also have disorders that lead to odor distortion, such as parosmia (i.e. distorted odor with a known source), or odor phantoms (i.e. odor sensation without an odor source). We surveyed a large population with at least one olfactory disorder (N = 2031) and found that odor distortions were common (46%), with respondents reporting either parosmia (19%), phantosmia (11%), or both (16%). In comparison to respondents with hyposmia or anosmia, respondents with parosmia were more likely to be female, young, and suffering from post-viral olfactory loss (P < 0.001), while respondents with phantosmia were more likely to be middle-aged (P < 0.01) and experiencing symptoms caused by head trauma (P < 0.01). In addition, parosmia, compared to phantosmia or anosmia/hyposmia, was most prevalent 3 months to a year after olfactory symptom onset (P < 0.001), which coincides with the timeline of physiological recovery. Finally, we observed that the frequency and duration of distortions negatively affects the quality of life, with parosmia showing a higher range of severity than phantosmia (P < 0.001). Previous research often grouped these distortions together, but our results show that they have distinct patterns of demographics, medical history, and loss in quality of life.

Assessment of odor hedonic perception: the Sniffin' sticks parosmia test (SSParoT)

Qualitative olfactory dysfunction is characterized as distorted odor perception and can have a profound effect on quality of life of affected individuals. Parosmia and phantosmia represent the two main subgroups of qualitative impairment and are currently diagnosed based on patient history only. We have developed a test method which measures qualitative olfactory function based on the odors of the Sniffin' Sticks Identification subtest. The newly developed test is called Sniffin' Sticks Parosmia Test (SSParoT). SSParoT uses hedonic estimates of two oppositely valenced odors (pleasant and unpleasant) to assess hedonic range (HR) and hedonic direction (HD), which represent qualitative olfactory perception. HR is defined as the perceivable hedonic distance between two oppositely valenced odors, while HD serves as an indicator for overall hedonic perception of odors. This multicenter study enrolled a total of 162 normosmic subjects in four consecutive experiments. Cluster analysis was used to group odors from the 16-item Sniffin' Sticks Identification test and 24-additional odors into clusters with distinct hedonic properties. Eleven odor pairs were found to be suitable for estimation of HR and HD. Analysis showed agreement between test-retest sessions for all odor pairs. SSparoT might emerge as a valuable tool to assess qualitative olfactory function in health and disease.

Factors Associated With Phantom Odor Perception Among US Adults: Findings From the National Health and Nutrition Examination Survey

Importance

Phantom odor perception can be a debilitating condition. Factors associated with phantom odor perception have not been reported using population-based epidemiologic data.

Objective

To estimate the prevalence of phantom odor perception among US adults 40 years and older and identify factors associated with this condition.

Design, Setting, and Participants

In this cross-sectional study with complex sampling design, 7417 adults 40 years and older made up a nationally representative sample from data collected in 2011 through 2014 as part of the National Health and Nutrition Examination Survey.

Exposures

Sociodemographic characteristics, cigarette and alcohol use, head injury, persistent dry mouth, smell function, and general health status.

Main Outcomes and Measures

Phantom odor perception ascertained as report of unpleasant, bad, or burning odor when no actual odor exists.

Results

Of the 7417 participants in the study, 52.8% (3862) were women, the mean (SD) age was 58 (12) years, and the prevalence of phantom odor perception occurred in 534 participants, which was 6.5% of the population (95% CI, 5.7%-7.5%). Phantom odor prevalence varied considerably by age and sex. Women 60 years and older reported phantom odors less commonly (7.5% [n = 935] and 5.5% [n = 937] among women aged 60-69 years and 70 years and older, respectively) than younger women (9.6% [n = 1028] and 10.1% [n = 962] among those aged 40-49 years and 50-59 years, respectively). The prevalence among men varied from 2.5% (n = 846) among men 70 years and older to 5.3% (n = 913) among men 60 to 69 years old. Phantom odor perception was 60% (n = 1602) to 65% (n = 2521) more likely among those with an income-to-poverty ratio of less than 3 compared with those in the highest income-to-poverty ratio group (odds ratio [OR], 1.65; 95% CI, 1.06-2.56; and OR, 1.60; 95% CI, 1.01-2.54 for income-to-poverty ratio <1.5 and 1.5-2.9, respectively). Health conditions associated with phantom odor perception included persistent dry mouth (OR, 3.03; 95% CI, 2.17-4.24) and history of head injury (OR, 1.74; 95% CI, 1.20-2.51).

Conclusions and Relevance

An age-related decline in the prevalence of phantom odor perception is observed in women but not in men. Only 11% (n = 64) of people who report phantom odor perception have discussed a taste or smell problem with a clinician. Associations of phantom odor perception with poorer health and persistent dry mouth point to medication use as a potential explanation. Prevention of serious head injuries could have the added benefit of reducing phantom odor perception.

Phantom odor perception and vascular conditions among adults in the United States: National Health and Nutrition Examination Survey 2011-2014

OBJECTIVES/HYPOTHESIS

Phantom odor perception has been correlated with burden of vascular risk among older adults. We evaluated associations between vascular conditions and phantom odor perception among adults in the United States.

STUDY DESIGN

Cross-sectional analysis.

METHODS

Cross-sectional data were collected as part of the 2011 to 2014 National Health and Nutrition Examination Survey, yielding a nationally representative sample of 7,417 adults aged 40 years and older. Phantom odor perception was defined as report of an unpleasant, bad, or burning odor when nothing is there. Participants reported on vascular conditions including history of stroke. Total cholesterol and glycated hemoglobinwere measured. High blood pressure was ascertained during an examination.

RESULTS

Stroke was associated with a 76% greater likelihood of phantom odor perception. Congestive heart failure and angina were associated with three times and 2.8 times the odds of phantom odor perception among adults 40 to 59 years and 60 years and older, respectively. Adults with diagnosed, but controlled, high cholesterol reported phantom odors more frequently than those without high cholesterol. Adults with diagnosed, but controlled, high blood pressure reported phantom odors more frequently than those without high blood pressure. We observed a threefold greater odds of phantom odor perception among adults aged 60 years and older with diabetes, but only among those who use both insulin and oral medications.

CONCLUSIONS

Stroke, angina, congestive heart failure, well-managed high blood pressure, and well-managed high cholesterol are associated with phantom odor perception. Vascular or metabolic conditions or their treatments may contribute to reporting of phantom odor perception.

LEVEL OF EVIDENCE

NA Laryngoscope, 130:332-337, 2020.

Phantom Smells: Prevalence and Correlates in a Population-Based Sample of Older Adults

Loss of olfactory function is common in old age, but evidence regarding qualitative olfactory dysfunction in the general older population is scarce. The current study investigates the prevalence and correlates of phantom smell experiences (phantosmia) in a population-based study (Swedish National Study on Aging and Care in Kungsholmen [SNAC-K]) of Swedish adults (n = 2569) aged between 60 and 90 years. Phantosmia was assessed through a standardized interview and defined as reporting having experienced an odor percept in the absence of any stimuli in the surrounding environment that could emit the odor. The relationships between phantosmia and demographic, genetic, health-related, and behavioral variables were analyzed with hierarchical logistic regression analyses. The overall prevalence of phantom smells was 4.9%, and was associated with female gender, carrying the met allele of the BDNF gene, higher vascular risk burden, and reporting distorted smell sensations (parosmia). Olfactory dysfunction was, however, not related to phantosmia. The most frequently reported phantom smell was smoky/burnt. A novel finding was that some individuals reported phantom smells with an autobiographical connotation. The results from this study indicate that the prevalence of phantosmia in the general older population is not negligible and that some factors that are beneficial for preserved olfactory function, such as female gender and the BDNF met allele, are also associated with the occurrence of phantom smells.

Disrupted Odor Perception

Olfactory loss is frequent. However, in public not many people complain of that, or they are even not (fully) aware of it. This indicates that it is possible to live a life without a sense of smell, albeit it is more dangerous, less pleasant, and food tastes much less interesting. Most common causes for smell loss are sinunasal disease (chronic rhinosinusitis with and without nasal polyps), acute infections of the upper airways, head trauma, and neurodegenerative disorders. In many people smell loss seems to be due to the aging process. Before treatment olfactory disorders are diagnosed according to cause with the medical history being a big portion of the diagnostic process. Olfactory disorders are in principle reversible, with a relatively high degree of spontaneous improvement in olfactory loss following infections of the upper respiratory tract. Medical treatment is according to cause. It also involves surgical approaches as well as conservative treatments including the use of corticosteroids, antibiotics, or smell training. Because today olfactory dysfunction seems to receive more attention than in previous years it can be expected that tomorrow we will have more specific and effective treatment options available.

Prognosis of Olfactory Dysfunction according to Etiology and Timing of Treatment

Objective We evaluated the severity of olfactory impairment according to risk factors, compared responses with risk factors and treatment timing, and investigated prognosis according to treatments. Study design Case series with chart review. Setting Tertiary referral center. Subjects and Methods We retrospectively reviewed medical records of patients complaining of loss of their sense of smell between January 2006 and May 2016. In total, 491 patients were included. We evaluated olfactory function using the Connecticut Chemosensory Clinical Research Center test (threshold test) and Cross-cultural Smell Identification Test. Results Post-upper respiratory infection patients showed better results than those with other risk factors (59.6% recovered). Patients with head trauma (12.5% recovered) and congenital olfactory dysfunction (0% recovered) showed poorer results. Earlier treatment showed better olfactory recovery outcomes for post-upper respiratory infection ( P = .001), head trauma ( P = .022), and nasal/sinus surgery ( P = .009). Xerostomia ( P = .73) and idiopathy ( P = .365) showed no significant difference in terms of treatment timing. The threshold test better reflected subjective recovery than the identification test. The systemic + topical steroid group and the systemic steroid treatment group both showed better smell recovery outcomes than the group with topical treatment alone (both, P < .001). However, there was no significant difference between the systemic treatment group and the systemic + topical treatment group ( P = .978). Conclusions Our findings suggest that the duration of smell loss is important for better olfactory outcomes with most etiologies. Also, the effects of systemic steroids were better than those of topical steroids, regardless of combined treatment.

Main causes and diagnostic evaluation in patients with primary complaint of olfactory disturbances

Introduction

Establishing a diagnosis in patients with olfactory disturbances has always been challenging for physicians.One reason for this is the rarity of some of the diseases that affect this sense, such as Kallmann's syndrome and post-viral olfactory loss.

Objective

To identify the major causes of olfactory disturbances and to describe the diagnostic evaluation in outpatients attended to at an ambulatory clinic specialized in olfaction disorders.

Methods

A retrospective analysis was performed in outpatients with primary olfactory complaint attended to between June 1, 2011 and September 30, 2013 in a center specialized in olfactory disorders. Patient history, nasofibroscopy, and the University of Pennsylvania Smell Identification Test (UPSIT) comprised the examination.

Results

Sixty-two patients were evaluated. The major causes were chronic rhinosinusitis (31%); rhinitis, primarily the allergic type (19%); post-viral olfactory loss (13%); and post-traumatic loss (8%). UPSIT scores were statistically different among different etiologies (p = 0.01).

Conclusions

The major diagnoses that should be part of the physician assessment when a patient complains of olfactory disturbance are chronic rhinosinusitis with and without polyps, allergic rhinitis, post-viral olfactory loss, and post-traumatic loss.

Evaluation of olfactory memory after coronary artery bypass grafting

Introduction

This study determined whether coronary artery bypass grafting (CABG) surgery has any effect on olfactory function, employing the Brief Smell Identification Test (B-SIT).

Material and methods

All the participants were informed preoperatively about the B-SIT test and the mode of its application. The test was performed by each patient preoperatively (d0) as well as 1 (d1) and 3 (d3) days following the surgery. C-reactive protein (CRP) levels were recorded at the same time as the smell test.

Results

This prospective study included 45 patients. The mean age was 67 ± 7.55, and the group was 29% male. The mean durations of cross clamping and cardiopulmonary bypass were 54 ± 32 min and 62.5 ± 37.0 min, respectively. Eleven different odors were tested. Significant differences were observed for several odors: leather between d0 and d3, pine between d0 and d3, onion between d0 and d1, onion between d0 and d3, and soap between d0 and d1. The postoperative CRP levels were significantly higher than the preoperative levels. The correlation analysis determined that the postoperative CRP levels were negatively correlated with the B-SIT score (r = –0.48, p = 0.001).

Conclusions

Our findings suggest that patients after CABG are prone to develop olfactory dysfunction in the early postoperative period and that olfactory dysfunction is associated with postoperative CRP levels.

Olfactory disorders and quality of life--an updated review

Olfactory disorders are common and affect about one-fifth of the general population. The main causes of olfactory loss are post viral upper respiratory infection, nasal/sinus disease, and head trauma and are therefore very frequent among patients in ear, nose, and throat clinics. We have systematically reviewed the impact of quantitative, qualitative, and congenital olfactory disorders on daily life domains as well as on general quality of life and depression. From the extensive body of literature, it can be concluded that loss of the sense of smell leads to disturbances in important areas, mainly in food enjoyment, detecting harmful food and smoke, and to some extent in social situations and working life. Most patients seem to deal well and manage those restrictions. However, a smaller proportion has considerable problems and expresses a noticeable reduction in general quality of life and enhanced depression. The impact of coping strategies is discussed.

Hidden consequences of olfactory dysfunction: a patient report series

BACKGROUND

The negative consequences of olfactory dysfunction for the quality of life are not widely appreciated and the condition is therefore often ignored or trivialized.

METHODS

1,000 patients with olfactory dysfunction participated in an online study by submitting accounts of their subjective experiences of how they have been affected by their condition. In addition, they were given the chance to answer 43 specific questions about the consequences of their olfactory dysfunction.

RESULTS

Although there are less practical problems associated with impaired or distorted odor perception than with impairments in visual or auditory perception, many affected individuals report experiencing olfactory dysfunction as a debilitating condition. Smell loss-induced social isolation and smell loss-induced anhedonia can severely affect quality of life.

CONCLUSIONS

Olfactory dysfunction is a serious condition for those affected by it and it deserves more attention from doctors who treat affected patients as well as from scientist who research treatment options.

Clinical features of olfactory disorders in patients seeking medical consultation

Background

Olfactory disorders are common complaints in ENT clinics. We investigated causes and relevant features of olfactory disorders and the need for gustatory testing in patients with olfactory dysfunction.

Material/Methods

A total of 140 patients seeking medical consultations were enrolled. All patients were asked about their olfactory disorders in a structured interview of medical history and underwent thorough otolaryngologic examinations and imaging of the head.

Results

Causes of olfactory disorders were classified as: upper respiratory tract infection (URTI), sinonasal diseases (NSD), head trauma, idiopathic, endoscopic sinus surgery, congenital anosmia, and other causes. Each of the various causes of olfactory dysfunction had its own distinct clinical features. Nineteen of 54 patients whose gustation was assessed had gustatory disorders.

Conclusions

The leading causes of olfactory dysfunction were URTI, NSD, head trauma, and idiopathic causes. Gustatory disorders were fairly common in patients with olfactory dysfunction. High priority should be given to complaints of olfactory disorders.

Long lasting phantosmia treated with venlafaxine

Qualitative olfactory disorders such as parosmia and phantosmia are not well investigated. In particular, the causes and treatment options for phantosmia are largely unknown. We report a case of long lasting phantosmia that disappeared under anti-depressive treatment, raising the question to what extent certain forms of qualitative olfactory disorders are an early symptom of depression.

Gray matter alterations in parosmia

Parosmia is a common olfactory disorder. In this condition, odors are perceived in a different quality than usual. This distorted olfactory percept is typically reported to be unpleasant. Little is known about the pathophysiology of this phenomenon. Previous studies demonstrated smaller volumes of the olfactory bulbs in patients with parosmia compared to subjects without parosmia. In order to investigate structural brain alterations in areas beyond the olfactory bulb, in the current study voxel-based morphometry was applied. A group of 22 parosmic patients was compared with control subjects matched for age- and sex, who exhibited a similar performance in olfactory tests. Performing a whole brain analysis, we found profound gray matter volume loss in the left anterior insula in parosmic patients. In an additional volume of interest analysis including primary and secondary olfactory areas, we also found volume loss in the right anterior insula, the anterior cingulate cortex, the hippocampus bilaterally, and the left medial orbitofrontal cortex. Many of these areas are critically involved in olfactory quality discrimination and odor memory. The present results indicate that reduced gray matter volume in brain regions supporting odor discrimination and memory is related to disturbed olfactory sensation in parosmia.

Evaluating the clinical usefulness of structured questions in parosmia assessment

OBJECTIVES/HYPOTHESIS

Parosmia and phantosmia relate to distorted odor perceptions. Little is known about their clinical significance. Measuring phantosmia and parosmia is still not possible. Today, assessment of parosmia or phantosmia relies mainly upon the patient's interview and the physician's experience. Therefore, we investigated the clinical usefulness of four structured questions in comparison to the patient's history regarding their accuracy in terms of the presence of odor distortions.

STUDY DESIGN

Tertiary care center outpatient clinic analyses.

METHODS

Responses from 193 patients were analyzed. All patients underwent full olfactory work-up (ear, nose, and throat examination, Sniffin' Sticks testing, structural brain imaging) and filled in a questionnaire with four parosmia questions and six questions regarding characteristics and severity of the parosmia. These responses formed the bases of a numerical parosmia score.

RESULTS

Patients with parosmia showed significantly lower parosmia scores (P <.001) when compared to either patients with phantosmia or patients without odor distortions. Two questions could be identified that showed a high association to the presence or absence of parosmia.

CONCLUSIONS

The present results confirm reports on the high frequency of parosmia and phantosmia among patients suffering from olfactory disorders. A parosmia score could be established that distinguishes between patients with or without odor distortions. The score provides valuable information regarding the presence or absence of parosmia, thus helping the physician during the patient's evaluation.

Psychophysical effects of nasal and oral inflammation

Olfactory disorders are common in "nasal inflammation" even though the term is comprehensive and subsumes different kinds of entities which have to be differentiated. The most common cause of olfactory disorders are sinonasal disorders, which are defined as secondary smell disorders caused by diseases/pathologies in the nose/paranasal sinuses. According to the literature, sinonasal disorders represent--depending on the examined population-up to 72% of all olfactory disorders. In general, noninflammatory and inflammatory disorders are differentiated. Inflammatory disorders can be further classified into infectious or noninfectious disorders, both forms in which olfactory disorders can be present. For the clinician examining patients, the exact classification of the olfactory disorder is mandatory in order to choose appropriate treatment and counseling. Among the most common inflammatory disorders are acute rhinitis, allergic rhinitis, post-upper respiratory tract infection and chronic rhinosinusitis, which are discussed in detail. In contrast to nasal inflammation, only little is known about oral inflammation and its psychophysical effects on taste function. Taste disorders following oral inflammation are briefly discussed.

Improvement of olfaction after endoscopic sinus surgery in smokers and nonsmokers

OBJECTIVES

The aim of this prospective study was to examine the short-term benefit of endoscopic sinus surgery (ESS) on the olfactory function of patients operated on for nasal polyposis. We also studied the predictive value of smoking for the recovery of the olfactory function in these patients.

METHODS

We studied 116 patients with nasal polyposis who underwent ESS. Olfactory testing was performed with the Sniffin' Sticks test before operation and 1, 3, and 6 months after operation.

RESULTS

All patients achieved a statistically significant stepwise increment of all of the indices of olfactory function over time. The composite threshold-discrimination-identification score was lower in smokers than in nonsmokers in all testing sessions, but none of these differences reached statistical significance. After adjustment for preoperative olfactory measures and all other potential confounders, the effect of smoking on the 6-month postoperative measurement was not significant. However, we did find a statistically significant adverse effect of the quantity of smoking on the olfactory threshold scores.

CONCLUSIONS

Both smokers and nonsmokers achieve a highly significant improvement on their olfactory function from ESS. Although smoking is not a major predictive factor for the short-term outcome of the olfactory function after ESS, a greater quantity of smoking may have an effect on the 6-month postoperative odor thresholds.

Complaints of olfactory disorders: epidemiology, assessment and clinical implications

PURPOSE OF REVIEW

Recent studies illuminate the difficulties that patients with olfactory disorder face in daily life, which underlines the need to understand its prevalence, and to diagnose and treat these patients. The purpose of the present review is to characterize olfactory disorders and describe associated complaints, present recent insights into epidemiology, suggest procedures to assess these disorders, and discuss clinical implications.

RECENT FINDINGS

A compilation of previous and new studies of olfactory disorders suggests associated complaints of poor quality of life, depression, and various specific consequences. Epidemiological studies show that loss in odor sensitivity is common in both general and clinical populations, whereas dysosmia is less common in general populations but frequent in clinical populations. The most common etiologies are post-upper respiratory infection, nasal/sinus disease and head trauma.

SUMMARY

Procedures to diagnose olfactory disorders and to identify etiologies are available. Depending on etiology, certain types of treatment are often successful, such as endoscopic sinus surgery and corticosteroid administration in nasal/sinus disease. In post-upper respiratory infection and head trauma, spontaneous recovery is fairly high. In any case, it is advisable to counsel the patient with regards to strategies to cope with olfactory disorders.

Clinical experience with patients with olfactory complaints, and their quality of life

CONCLUSION

A special consulting team for patients with olfactory disorders would be able to verify, describe, and explain the characteristics of the disorders, also in cases where a patient experiences a disorder, but has a normal sense of smell.

OBJECTIVES

The general purpose of this paper was to present our experience with patients seeking medical attention for olfactory disorders, and to describe how quantitative and qualitative olfactory disorders are diagnosed, what the etiologies are, and how quality of life is compromised in patients with olfactory disorders.

SUBJECTS AND METHODS

This investigation was performed prospectively over a 10-year period by one physician responsible for the consulting team for patients with olfactory disorders. Based on a standardized clinical examination, a structured interview, and assessment of olfactory function, its aim was to diagnose quantitative and qualitative disorders in 303 consecutive patients. Health-related quality of life was assessed with the Nottingham Health Profile (NHP) in about one-third of patients.

RESULTS

In the majority of patients, a reduced sense of smell was found after testing. Often, but not always, this was combined with qualitative disorders. Dominating etiologies were infections, nasal polyposis, head trauma, and aging. Patients complaining of olfactory disorders experience a significantly reduced quality of life regarding the impact of their health problem on paid employment, household work, and social and family life.

A study on the prognostic significance of qualitative olfactory dysfunction

We investigated the frequency and prognostic significance of qualitative olfactory dysfunction (parosmia, phantosmia) in a retrospective patient based study. A total of 392 patients with impairment of olfaction were tested at least two times for their olfactory function using the "Sniffin' Sticks". The mean interval between the first and the last test was 11 months. At the first visit 34% of all patients reported parosmia. Parosmia was most frequent in patients with postinfectious olfactory loss (56%), and less frequent in idiopathic, posttraumatic, sinunasal disease with frequencies of 10, 14, and 28%, respectively. In contrast, only 12% of all patients had phantosmias, with no significant differences between the patient groups. Improvement of olfactory function was found in 23% of all patients (n = 90). Pre-existing parosmia or phantosmia had no significant effect on recovery rate. Regarding qualitative olfactory dysfunction, 29% of those patients reporting parosmia reported relief of this symptom after an average of 12 months, whereas 53% of phantosmic patients lost phantosmia during the observation period. Although it has been suggested that olfactory distortion s could be regarded as an indicator of early recovery of decreased olfactory sensitivity, the current data indicate that occurrence of parosmia or phantosmia has little prognostic value. Phantosmia disappears at a faster rate than parosmia. These insights into qualitative olfactory dysfunction are regarded to be significant in the counseling of patients with olfactory loss.

Olfactory dysfunction as a predictor of neurodegenerative disease

Olfactory dysfunction is present in patients diagnosed with Alzheimer's disease or idiopathic Parkinson's disease and can differentiate each of these disorders from related disorders with similar clinical presentations. The pathologic hallmarks of each disease are present in brain regions involved in processing olfactory input. Both the olfactory functional deficits and the corroborating pathologic lesions are present in asymptomatic subjects with increased risk of developing these diseases. Preclinical detection of neurodegenerative diseases is necessary to control their devastating effects on individuals and societies. We address whether olfactory dysfunction can be used to assess risk for developing Alzheimer's disease or Parkinson's disease in asymptomatic individuals. We argue that further characterization and a deeper understanding of olfactory deficits in these neurodegenerative diseases at the molecular, cellular, and systems levels will augment our acumen for preclinical detection and elucidate pathogenic mechanisms to guide the development of new therapeutic modalities.

Aging and olfactory and taste function

This article focuses on the change in olfaction and taste with aging. It discusses histopathology with an emphasis on age-related changes, causes of chemosensory dysfunction in the elderly, how to evaluate a patient with dysfunction, useful tests and imaging, clinical consequences of chemosensory impairments, and available treatment options.

Basic and clinical aspects of olfaction

Disturbances of olfaction are a common occurrence in many neurological and neurosurgical patients and their correct diagnosis might be helpful in management and enhancement of quality of life. However, olfaction is seldom checked in most neurosurgical units and the "smell bottles" are often either absent or out of date. This chapter reviews systematically recent advances in our understanding of the anatomy, physiology (olfactory coding) and measurement of olfactory function in the human. The causes and symptoms of smell disorders, risk of damage to the olfactory system by various surgical procedures and, finally, the natural history of recovery and treatment of smell disorders, for example after trauma, are discussed.

Olfactory dysfunction and daily life

The objective of the present study was to investigate the hypothesis that subjects with parosmia suffer more in their daily life than patients who experience only quantitative olfactory loss. Two hundred five outpatients of the Smell and Taste Clinic and 25 healthy controls were included. The newly developed Questionnaire of Olfactory Disorders (QOD) was administered in combination with other psychometric tests (Beck Depression Inventory, "Befindlichkeitsskala" and the Short Form-36 Health Survey) along with an olfactory test ("Sniffin' Sticks"). Results of the QOD were found to be an appropriate and valid measure of the impact of olfactory dysfunction on daily life. Patients with parosmia and quantitative olfactory dysfunction show higher rates of daily life complaints when compared to patients suffering from quantitative olfactory impairment only (QOD-PS: P=0.005). In addition, hyposmic and anosmic patients indicated significantly more complaints compared to patients with normosmia. Further, female patients seemed to suffer more from olfactory dysfunction than male patients. In conclusion, the assessment of the degree of qualitative olfactory dysfunction may be possible by the use of instruments based on questionnaires regarding daily life problems.

Riechstörungen

INTRODUCTION

Olfactory dysfunction has been reported to affect more than 200,000 patients a year in the USA. The aim of this survey was to obtain comparable epidemiological data and treatment information on olfactory dysfunction in German speaking countries.

METHODS

Questionnaires were sent to all otorhinolaryngology departments in Germany, Austria and Switzerland; 52% of hospitals completed the survey.

RESULTS

An average of 46 patients with olfactory dysfunction were treated per hospital every month. Hyp- and anosmia were most commonly caused by inflammatory diseases of the nose/paranasal sinuses (53%), respiratory dysfunction (19%), or postviral conditions (11%). Steroids were used most frequently for pharmacological treatment (topically 82%; orally 65%). Approximately one third of the clinics used B vitamins, or zinc; 80% of the hospitals performed surgery to treat underlying diseases. Acupuncture and smell training was used by approximately 20%.

CONCLUSION

A total of 79,000 patients per year are treated for olfactory dysfunction in German hospitals. The vast majority of these disorders (72%) is caused by sinunasal diseases. The quality control of therapeutic strategies is urgently needed.

Clinical presentation of qualitative olfactory dysfunction

Many patients with olfactory dysfunction not only experience quantitative reduction of olfactory function, but also suffer from distorted olfactory sensations. This qualitative dysfunction is referred to as parosmia (also called "troposmia") or phantosmia, with the major difference that distorted olfactory sensations are experienced in the presence or absence of an odor, respectively. Our clinical observations corroborate the literature in terms of a general underestimation of the incidence of olfactory distortions. Based on selected cases we try to show that olfactory distortions exhibit a large variance in their clinical appearance. Further, emphasis is placed on the fact that only a detailed and directed history of the patient can provide cues to the correct diagnosis.

A Scandinavian adaptation of the Multi-Clinic Smell and Taste Questionnaire: evaluation of questions about olfaction

OBJECTIVE

A Scandinavian adaptation of the Multi-Clinic Smell and Taste Questionnaire (MCSTQ-Sc) was evaluated with respect to comprehension and test-retest reliability for responses to questions about olfactory dysfunction (abnormal sensitivity, parosmia and phantosmia) and related questions about medical history and consequences of olfactory dysfunction.

MATERIAL AND METHODS

Comprehension was evaluated in a first study in 20 patients with chief complaints of olfactory dysfunction by comparing questionnaire- and interview-based responses. Test-retest reliability was evaluated in a second study in 30 other patients with olfactory complaints.

RESULTS

Data from the two studies suggest that the vast majority of the questions evaluated from the MCSTQ-Sc are comprehensible and generate responses with very good reliability. Distinct exceptions were poor agreement between the questionnaire- and interview-based responses for questions about the number of cigarettes smoked and the pleasantness and typical episode length of phantosmia; the test-retest reliability regarding the nostril side of phantosmia also showed poor agreement. The results suggest the importance of probing these areas further in the clinical interview.

CONCLUSION

The findings imply that, with a few caveats, the MCSTQ-Sc is a useful tool for the clinical assessment of olfactory dysfunction and its consequences.