Clinical assessment of retronasal olfactory function

OBJECTIVES: To develop a test kit for the simple assessment of retronasal olfactory function and to compare orthonasal and retronasal olfactory function in healthy subjects and patients with olfactory disorders. DESIGN AND PATIENTS: We tested 230 individuals with normosmia, hyposmia, and anosmia using grocery-available powders. Initially, 30 different substances were investigated. Subjects identified each substance using a list with 4 verbal items (forced choice). After preliminary experiments, 20 items were selected according to the degree to which they were identified by normosmic and anosmic subjects. Orthonasal olfactory function was assessed psychophysically using "sniffin' sticks," which includes tests for odor identification, discrimination, and butanol odor thresholds. In addition, anosmia was confirmed electrophysiologically by means of olfactory-evoked potentials. RESULTS: In healthy subjects, there was a test-retest reliability correlation of r(27) = 0.76 for retronasal olfactory function, which is similar to other odor identification tests. Retronasal testing in normosmic subjects allowed for the discrimination of sex-related differences, with women scoring higher than men (P =.007), and the identification of a slight decrease with age (r(120) = -0.20; P =.03). Orthonasal and retronasal identification of odors was found to correlate (r(86) = 0.78; P<.001). Retronasal testing allowed for the discrimination between normosmia, hyposmia, and anosmia (P<.001). In addition, retronasal performance of anosmic patients appeared to improve with duration of anosmia (P =.03). No difference was found between patients with anosmia of different origin. CONCLUSION: Results of the present investigation indicate that the assessment of retronasal olfactory function is possible using oral stimulus presentation.     

Retronasal and orthonasal olfactory ability after laryngectomy

OBJECTIVE: To characterize orthonasal and retronasal olfactory ability in patients who have had a total laryngectomy (TL). DESIGN: Prospective psychophysical evaluation of orthonasal and retronasal olfactory function. SETTING: Academic center outpatient clinic. PATIENTS: Volunteer sample of 36 subjects who underwent laryngectomy 0.5 to 25.0 years after TL (median, 3.5 years) and 36 age-, sex-, and smoking history-matched controls. MAIN OUTCOME MEASURES: Scores on established psychophysical tests of orthonasal and retronasal olfaction and self-rating scores of smell assessed with a visual analog scale. RESULTS: Assessment of orthonasal olfactory ability yielded a mean composite score of 4.3 (maximum score, 7) for the TL group and 5.3 for the control group (P = .002). Evaluation of retronasal olfactory ability resulted in a mean score of 11.0 (maximum score, 20) for the TL group vs 14.3 for the control group (P<.001). The mean self-rating scores of smell were 2.9 and 6.6 (maximum score, 10) for the TL and control groups, respectively (P<.001). Self-ratings of smell positively correlated with orthonasal (r(S) = 0.42; P<.001) and retronasal (r(S) = 0.50; P<.001) olfactory ability. CONCLUSIONS: Laryngectomy is associated with measurable decreases in olfactory function that are also subjectively perceived. Quantification of decrements in orthonasal and retronasal olfactory function can be used to characterize the severity of hyposmia and to assess the potential for, and efficacy of, olfactory rehabilitation. Although self-assessment with a simple visual analog scale successfully identifies many laryngectomy patients who have objective evidence of olfactory dysfunction, further investigation is necessary to evaluate and compare its validity and reliability with other available survey instruments that purport to measure olfaction.     

Retronasal olfactory function in nasal polyposis

OBJECTIVE: To investigate the question of whether there is a difference in retronasal olfactory function between patients suffering from chronic rhinosinusitis with nasal polyposis (NP) and healthy controls. This question was based on the clinical observation that many of these patients present with smell loss without complaining about loss of the appreciation of foods. STUDY DESIGN: Open prospective study comparing symptomatic patients with healthy controls. METHODS: A total of 56 healthy volunteers and 42 NP patients were tested for orthonasal and retronasal odor identification. All subjects received detailed nasal endoscopy; NP was staged according to the Malm classification. Patients rated their olfactory function on visual analogue scales. Orthonasal testing was performed using the "Sniffin' Sticks" test kit. Retronasal testing was evaluated with odorized powders applied to the oral cavity. In both tests, subjects were asked to identify 10 items using a forced choice paradigm. RESULTS: Overall, odor identification was better in controls compared with NP patients (P <.001). Although controls exhibited no difference between orthonasal and retronasal smelling (P =.26), in NP patients, olfactory function was significantly better when odors were applied through the retronasal route (P <.001). Ratings of general olfactory abilities correlated with retronasal and orthonasal olfactory function in NP patients (P <.001) but not in healthy controls (P =.34). CONCLUSION: Better retronasal than orthonasal olfactory function seems to be associated with the presence of mechanical obstruction in the anterior portion of the olfactory cleft. In turn, these data indicate that olfactory loss in NP seems to be caused by regional mechanical or inflammatory factors.     

Differences between orthonasal and retronasal olfactory functions in patients with loss of the sense of smell

OBJECTIVE: To investigate differences between orthonasal and retronasal olfaction in patients with loss of the sense of smell without taste complaints. DESIGN: Electrophysiological and psychophysical testing of orthonasal and retronasal olfactory functions. SETTING: Outpatient clinics. PATIENTS: A series of 18 patients who had olfactory loss due to various reasons but no "taste" complaints. MAIN OUTCOME MEASURES: Orthonasal and retronasal olfactory functions assessed by olfactory event-related potentials and psychophysical smell tests. RESULTS: Psychophysical testing revealed retronasal olfaction to be normal or slightly altered, whereas orthonasal olfaction was either absent or severely compromised. Findings from nasal endoscopic examinations and computed tomographic scans were within the reference range in all subjects. In response to orthonasal stimulation there were neither detectable olfactory event-related potentials nor any with small amplitudes, whereas olfactory event-related potentials in response to retronasal stimulation were clearly present in some patients. CONCLUSION: These clinical observations, together with the psychophysical and electrophysiological findings, suggest that orthonasal and retronasal olfaction might be processed differently.     

Retro- and orthonasal olfactory function in relation to olfactory bulb volume in patients with hypogonadotrophic hypogonadism

Introduction

Idiopathic hypogonadotrophic hypogonadism with an olfactory deficit is defined as Kallmann syndrome and is distinct from normosmic idiopathic hypogonadotrophic hypogonadism.

Olfactory function assessed with orthonasal and retronasal testing, olfactory bulb volume, and chemosensory event-related potentials

OBJECTIVE: To investigate whether differences in olfactory function between healthy individuals and patients with olfactory loss could be detected by various diagnostic tests. DESIGN: Psychophysical testing of orthonasal and retronasal olfactory functions, magnetic resonance imaging of olfactory bulb (OB) volume, and chemosensory event-related potential (ERP) measurement performed between January 1, 2005, and October 31, 2005. SETTING: Academic tertiary referral medical center. PATIENTS: Eleven healthy individuals with normal olfactory function (NL) and 11 patients with nasal polyposis (NP), 11 with posttraumatic olfactory loss (PT), and 11 with postinfectious olfactory loss (PI) were included in this study. MAIN OUTCOME MEASURES: Orthonasal and retronasal olfactory test results, magnetic resonance imaging-based OB volume, and ERPs to both olfactory and intranasal trigeminal stimulation. RESULTS: Orthonasal and retronasal testing revealed that NL individuals had higher scores than patients with NP, PT, or PI. Retronasal scores were higher in NP patients compared with PT and PI patients. The OB volumes were higher in NL individuals compared with NP, PT, and PI patients. The OB volumes in PT patients were significantly lower than those from NP and PI patients. Olfactory ERPs were different between NL individuals and NP, PT, and PI patients, and trigeminal ERPs were significantly different when comparing NL individuals with NP patients. For the entire cohort, a significant correlation was found between orthonasal testing and OB volume, between retronasal testing and OB volume, and between both orthonasal and retronasal testing and olfactory ERP amplitudes. Olfactory ERPs were recorded in the 11 NL individuals and in 3 NP, 3 PT, and 4 PI patients, defined as responders. Orthonasal and retronasal test scores, OB volume, and olfactory ERPs were significantly larger in responders compared with nonresponders. CONCLUSIONS: Significant differences in various tests that evaluate olfactory function were detectable in a cohort of NL individuals and NP, PT, and PI patients. This finding suggests that these diagnostic tools provide information in terms of the clinical assessment of olfactory function. Future studies will investigate their combined use in terms of the prognosis of olfactory function in patients with olfactory loss.     

Retronasal and orthonasal olfactory function in relation to olfactory bulb volume in patients with posttraumatic loss of smell

OBJECTIVE: The aims of this study were to evaluate olfactory function with orthonasal and retronasal testing in patients with posttraumatic olfactory loss and to investigate the relation between residual olfactory function and olfactory bulb (OB) volume. METHOD: A retrospective study of 25 patients with posttraumatic olfactory loss was performed. Orthonasal olfactory function was assessed with the Sniffin' Sticks test kit; retronasal olfactory function was assessed with intraorally applied odors. Magnetic resonance imaging was used to determine OB volume and cortical damage in the frontal and temporal areas. RESULTS: The main outcomes of the present study were the demonstration of a correlation between olfactory function and OB volume, which was more pronounced for retronasal than for orthonasal olfactory function; retronasal olfactory function was most affected in the patients with the most extensive cerebral damage and was least compromised in patients without such damage; OB volumes were smaller in patients with parosmia compared with those without; and the presence of parosmia was clearly associated with the presence of cerebral damage. CONCLUSION: The data confirm that OB volume is an indicator of olfactory function but, interestingly, in this study, it is largely determined by retronasal olfactory sensitivity. In addition, these results emphasize the role of higher cortical centers in olfactory function, and especially in parosmia, which may, at least in some cases, be related to lesions in the fronto-orbital and anterior temporal cortices. It would be of interest to investigate OB volume further in relation to the prognosis of the disorder.     

Non-sinonasal-related olfactory dysfunction: A cohort of 496 patients

Introduction and aimThere is a high prevalence of olfactory dysfunction in the general population. Several causes of olfactory dysfunction have been reported and this disorder is classically divided into sinonasal and non-sinonasal-related olfactory dysfunction. The aims of this study were firstly, to evaluate the frequency of the various aetiologies of olfactory dysfunction in a population of patients with non-sinonasal-related olfactory dysfunction and secondly, to evaluate the degree of olfactory impairment associated with these various aetiologies.Material and methodsWe retrospectively reviewed a cohort of 496 patients with non-sinonasal-related olfactory dysfunction. The aetiology of the olfactory dysfunction was recorded for each patient. The aetiology was determined by a complete clinical assessment, including medical history, complete otorhinolaryngological examination, psychophysical testing of olfactory function, recording of olfactory event-related potentials and brain magnetic resonance imaging. Six groups of patients were defined on the basis of the aetiology of the disease and orthonasal and retronasal psychophysical olfactory performances were evaluated in each group.ResultsPost-infectious and post-traumatic aetiologies were the most common causes, representing 37.9% and 33.1% of patients, respectively, followed by idiopathic (16.3%), congenital (5.9%), toxic (3.4%) and neurological (3.4%) olfactory dysfunction. Anosmia was significantly more frequent in congenital (93.1%) and post-traumatic (62.8%) olfactory dysfunction, whereas hyposmia was more frequent in the post-infectious group (59.6%). Orthonasal and retronasal olfactory function tests were significantly correlated in all groups except for the congenital group.ConclusionsThe data of this study confirm that the most common causes of non-sinonasal-related olfactory dysfunction are post-infectious and post-traumatic. Post-infectious olfactory dysfunction is mainly observed in middle-aged women and is mainly associated with hyposmia, whereas post-traumatic olfactory dysfunction is mainly observed in young men and is associated with a high rate of anosmia.     

Clinical assessment of olfactory functions in children who underwent adenotonsillectomy during pre- and post-operative period

Objective

The aim of this study was to investigate the changes of both ortho- and retronasal olfactory function in children who underwent adenotonsillectomy (AT) operation due to infectious and/or obstructive adenotonsillar disease.

Material and methods

A total of 25 children with adenotonsillar disease are included in the study; the children were followed for 6 months in the conducted clinics and underwent AT operation. An age- and sex-matched control group was constituted with 25 healthy children free of adenotonsillar disease. Adenoid and tonsillar hypertrophy was graded according to the subjective size scales. Each subject’s orthonasal and retronasal olfactory functions were assessed using odor identification test and retronasal olfactory testing. These tests were performed once, at the beginning of the study, for the control group and performed twice, at the beginning of the study and the third month follow-up, for the disease group. Parents of children in the adenotonsillar disease group filled out a visual analog scale to evaluate the children’s appetite at the same time with olfactory testing.

Results

The current investigation produced four major findings: (1) both ortho- and retronasal olfactory abilities of participants were improving following AT operation, (2) adenoid hypertrophy had a significant negative effect on both ortho- and retronasal olfaction, whereas tonsil hypertrophy had significant negative effect only on the retronasal olfactory score, (3) retronasal olfaction was found to be more affected by the adenoid size than the orthonasal, as shown with correlation analysis, and (4) the increase in appetite of children after AT operation had been specified by parents.

Conclusions

Children with adenotonsillar disease have increased olfaction abilities, namely ortho- and retronasal olfactory function following AT operation. In addition, retronasal olfactory function, an important component of flavor, seems to be more affected than orthonasal function. These results also explain the increased appetite of operated children.     

How do children with adenoid hypertrophy smell and taste? Clinical assessment of olfactory function pre- and post-adenoidectomy

OBJECTIVE: To assess the ability to smell and appreciate food in children with adenoid hypertrophy pre and post-adenoidectomy. METHODS: A total of 35 children with adenoid hypertrophy admitted for adenoidectomy (aged 5-9.3 years, mean age 5.9 years) were tested preoperatively. In a follow up appointment 3 months postoperatively, 28 of them returned and were tested again. The control group consisted of 30 healthy children (aged 5-10.2 years, mean age 6.1 years). Orthonasal olfactory function was assessed psychophysically using "Sniffin sticks" 12 item odor identification test. Retronasal olfaction was assessed using a collection of 12 grocery available powders applied to the oral cavity. RESULTS: Both orthonasal and retronasal olfactory function of the study group preoperatively were significantly lower in comparison with the results of the control group (p<0.0001). The difference in retronasal olfaction between groups was significantly higher in comparison with the difference in orthonasal odor identification (p=0.048). There is a strong correlation between adenoid hypertrophy grade and retronasal testing results (t=-5.461, p<0.0001), but not with the orthonasal results (t=-1.677, p=0.9). Significant improvement of orthonasal and retronasal olfaction was observed in the follow-up appointment (p<0.0001). Relative increase postoperatively was higher for the retronasal olfaction compared to orthonasal olfaction (p=0.0029). CONCLUSIONS: Children with adenoid hypertrophy have a reduced ability to smell, with retronasal olfactory function being more affected. Surgery had a greater impact on retronasal olfaction.     

The combined olfactory test in a Chinese population

OBJECTIVE: To establish an olfactory test in the Hong Kong Chinese population. STUDY DESIGN: Prospective analysis of the results of a combined olfactory test (COT) for patients with olfactory dysfunction and for normal subjects attending a secondary and tertiary ear, nose and throat centre. METHOD: Our COT was based on and modified from the Connecticut Chemosensory Research Centre test. It consisted of an odour identification test involving nine substances and a threshold test using a series of threefold dilutions of 1-butanol. From September 1998 to June 2002, 188 Hong Kong Chinese patients with olfactory dysfunction and subjects with normal olfaction were prospectively recruited. The subjects were categorized into normal, hyposmic and anosmic groups. The olfactory function of the main group of subjects (n = 153) was assessed with the COT by a blinded observer and also quantified with a visual analogue scale; the results were analysed to validate the discriminative ability of the COT. Another subgroup of subjects (n = 35) was tested with the COT twice with a two-week interval to evaluate test-retest reliability. RESULTS: There were 42 normal, 68 hyposmic and 43 anosmic subjects within the main group (total n = 153). The identification scores, threshold scores and combined olfactory scores were statistically significantly different between the anosmic, hyposmic and normal groups of subjects (p < 0.001). The combined olfactory score correlated with the visual analogue score and the correlation coefficient was 0.56 (p < 0.01). The mean time spent on each COT was 8.6 minutes (standard deviation = 3.4 minutes). The test-retest reliability of the COT was satisfactory, with a one-way model intraclass correlation coefficient of 0.87 (n = 35). CONCLUSION: The satisfactory discriminative ability and test-retest reliability of the COT have been demonstrated in this study. The COT is a feasible method for assessing sense of smell in the Hong Kong Chinese population.     

Trigeminal event-related potentials in patients with olfactory dysfunction

OBJECTIVE: There are mutual interactions between the olfactory and trigeminal systems. The purpose of this study was (1) to assess trigeminal sensitivity using chemosensory event-related potentials (CSERPs) in patients with olfactory dysfunction and (2) to evaluate whether trigeminal ERPs were different with regard to the presence or absence of olfactory ERPs. MATERIALS AND METHODS: Prospective study of 60 patients who presented with olfactory dysfunction (postinfectious olfactory loss: n = 19, posttraumatic olfactory loss: n = 28, and olfactory loss due to idiopathic, or toxic causes: n = 13). All patients were extensively evaluated with an orthonasal olfactory test based on the "Sniffin' Sticks". In addition, chemosensory ERPs were recorded in response to olfactory and trigeminal stimulation. RESULTS: Olfactory/trigeminal ERPs were recorded in 25/60 patients, respectively. Patients with no detectable olfactory ERPs, considered as severely affected, demonstrated an altered trigeminal sensitivity as indicated by an increase in P2 latencies and a decrease in both, P2 and N1-P2 amplitudes compared to patients with detectable olfactory ERPs. A regression analysis showed a negative relation between P2 latencies and the "Sniffin' Sticks"score (r = -0.46, p < 0.001). CONCLUSIONS: Patients with severe olfactory dysfunction demonstrated decreased trigeminal sensitivity as indicated by electrophysiological measures. This study supports the idea of interactions between the chemical senses. Whether altered responses to trigeminal stimulation may be used as a prognostic measure related to recovery from olfactory loss remains to be demonstrated.     

嗅觉味觉功能的临床检测

目的:探讨嗅觉障碍患者嗅觉和味觉功能的改变。方法:284例受试者中,健康人92例,嗅觉功能减退92例,嗅觉功能丧失100例,分别采用T&T、嗅觉事件相关电位(OERPs)及三滴法进行嗅觉和味觉功能检测。结果:T&T结果,嗅觉功能减退和丧失患者跟健康人比较差异有统计学意义(P<0.05)。OERPs结果显示,嗅觉功能障碍患者跟健康人比较N1、P2波潜伏期延长且振幅降低,差异有统计学意义(P<0.05)。三滴法结果显示,嗅觉功能障碍患者跟健康人比较味觉功能有明显减退,差异有统计学意义(P<0.05)。各组之间男女比较差异无统计学意义。结论:嗅觉功能障碍患者同时伴有味觉功能的减退,嗅觉和味觉功能的减退与性别关联不大。嗅觉味觉的联合检查可以全面系统反映受试者的化学感觉功能,为临床诊断和治疗提供科学依据。     

What is the correlation between ratings and measures of olfactory function in patients with olfactory loss?

BACKGROUND: Major complaints of many patients with olfactory dysfunction relate to the impairment of quality of life. Nevertheless, it is unclear to what extent there is a correlation between ratings of olfactory abilities/impairment and olfactory function. METHODS: Patients with olfactory dysfunction (n = 152) were examined psychometrically using the "Sniffin' Sticks" test battery. Ratings of olfactory function and ratings of impairment were recorded using visual analog scales. RESULTS: Following standardized olfactory testing, 78 of the 152 patients were categorized as functionally anosmic, 64 as hyposmic, and 10 as normosmic. Groups differed significantly with regard to ratings of olfactory function. Functionally anosmic patients rated impairment to be significantly higher compared with hyposmic and normosmic patients. Ratings of olfactory function correlated significantly with measured olfactory function (r = +0.57) and ratings of impairment (r = -0.30). CONCLUSION: There was a moderate correlation between ratings and measures of olfactory function. On average, functionally anosmic patients recognized their olfactory loss, although, on an individual basis, there were striking differences between measures and ratings of olfactory function.     

Validation of the combined olfactory test

A new test of olfactory function, the combined olfactory test, has been designed to assess odours easily recognizable by the test population. The test consists of an odour recognition test of nine odours, where an odour in a bottle is chosen from a list of four possible odours in a forced choice manner. This is followed by a threshold test using a series of three-fold dilutions of l-butanol. The mean of the two scores is the combined olfactory score. The test was subjected to a validation study. It was performed on 133 participants with a normal sense of smell and a normal rhinological examination and on 94 participants who said that they did not have a sense of smell. There was a highly significant difference between the combined olfactory score in the normal and ‘anosmic’ groups (P < 0.001). This significant difference was the same between the two groups for the threshold and odour recognition arms of the test. There was a highly significant differece (P < 0.001) between the two subgroups of ‘completely anosmic’ and ‘almost anosmic’ participants, indicating that the test could grade the degree of olfactory dysfunction.     

Grade 4 tonsillar hypertrophy associated with decreased retronasal olfactory function: a pilot study

Tonsillar hypertrophy is common in children, but it can also be present in adults. Enlarged tonsils, a significant anatomical barrier, may affect the flow of odor molecules from the oral cavity to the nasal passages, which has not yet been studied. Thus, we aimed to investigate the mass effect of palatine tonsillar hypertrophy on retronasal olfaction. This study was carried out in 146 subjects, with a mean age of 22.1 ± 2.2 years, ranging 20–29 years. An oropharyngeal examination of the participants was completed, and tonsillar hypertrophy was graded according to the subjective tonsil size scale. The participants were divided into four groups according to their tonsil size grading; then, each subject’s orthonasal olfactory and retronasal olfactory functions were assessed using “Sniffin’ Sticks” and retronasal olfactory testing. There were no differences observed between the groups in terms of age, gender, cigarette smoking, or alcohol consumption. In addition, there was no difference between the groups in terms of “Sniffin’ Sticks” subtests and TDI scores. It was determined that the retronasal olfactory scores of the participants with grade 4 tonsil size were significantly lower than the retronasal olfactory scores of the participants with grade 1 tonsil size. The current investigation demonstrates that grade 4 tonsillar hypertrophy has significant negative effects on the retronasal route of olfactory sensing, when compared with grade 1 tonsillar hypertrophy.     

Clinical significance of results from olfactory testing

BACKGROUND: Although widely used in healthy subjects and patients with olfactory loss, the significance of changes of scores from validated olfactory tests is unknown. AIM AND METHODS: The aim of the present study was to relate the self-assigned changes of olfactory function in terms of "better," "unchanged," and "worse" in patients with smell disorders with the results from olfactory testing by means of a validated test set. Olfactory function of 83 anosmic or hyposmic patients (40 women, 43 men; age 12-84 yr) was tested on two occasions (mean interval 136 days, minimum 7 days, maximum 6.7 yr). Olfactory function was assessed using a validated technique ("Sniffin' Sticks"). This test consists of three subtests, one for odor threshold (T), odor discrimination (D), and odor identification (I), with possible results ranging up to 16 points each. From the sum of the results from the three subtests a composite "TDI" score was obtained. RESULTS: Forty-four patients indicated an improvement of olfactory function, whereas 39 patients reported no change. No subject reported deterioration of olfactory sensitivity. Subjects assigned to group BETTER had higher TDI scores in the second olfactory tests than subjects assigned to the group UNCHANGED, both in absolute terms and as compared with the first olfactory test (effect "test occasion" by "self-assessed improvement," P < .001). There was no significant difference between groups with respect to age and sex (P = .99 and .84, respectively). Logistic regression showed that more than 60% of the subjects reported an improvement of olfactory sensitivity when the TDI score increased by 5.5 points. CONCLUSION: We show that there is a statistically significant relation between measured and perceived improvement of olfactory function in patients who first presented with the diagnosis of anosmia or hyposmia. The results indicate that improved olfactory function in patients with olfactory deficiency is perceived as such in everyday life and is quantitatively related to an improvement in the composite TDI score of the "Sniffin' Sticks" olfactory test battery. This is the basis for the application of a specific therapy for olfactory loss because of a possible gain in quality of life for the patients.     

Psychophysiological and electrophysiological testing of olfactory and gustatory function in patients with multiple sclerosis

The olfactory (OF) and gustatory function in multiple sclerosis (MS) patients and possible influencing variables of the disease, such as depression or fatigue, were determined. In an open prospective controlled clinical study 30 patients with MS and 30 healthy controls matched for age, sex and smoking-habits were investigated. With Mini Mental State Examination cognitive dysfunction was excluded, with Expanded Disability Status Scale the patient’s ability to accomplish the tests was ensured. The severity of depression was measured with the self-reported Beck Depression Inventory. The orthonasal olfactory function was derived with olfactory event related potentials (OERP) and TDI-score (Threshold, Discrimination and Identification, Sniffin’ Sticks). Retronasal olfactory function was tested with Taste-Powder-score, gustatory function with Taste-strip-score. There was a significant loss of olfactory function measured with TDI-score [12/30 (40%), p = 0.002] and gustatory function [5/23 (21.7%), p < 0.001] in MS-patients, 23.8% (5/21) of MS-patients showed hyposmia with OERPs, significantly correlating with the TDI-score (p = 0.03). The Expanded Disability Status scale score inversely correlated with the TDI-score (p = 0.002). This study confirms the incidence of olfactory disorder in MS-patients and reveals a frequent gustatory deficit. The Identification subtest can be proposed as a marker of the OF in MS-patients: it includes complex cognitive tasks and may be influenced by depression and fatigue, which are common symptoms of MS. It inversely correlates with the disability status.     

Retronasal testing of olfactory function: an investigation and comparison in seven countries

Flavor perception is to a large extent determined by olfaction, and persons who lost their sense of smell consequently complain about strongly reduced enjoyment of food. The retronasal olfactory function is especially important for flavor appreciation. The aim of this study was to compare retronasal function across different cultures and to develop a test that is applicable across cultures. Identification of 39 retronasal applied odor probes was tested in a total of 518 participants of seven countries; 292 of them were healthy, and 226 exhibited a smell disorder. A retest was performed with 224 of the healthy participants. Furthermore, all participants were tested for orthonasal threshold, identification, and discrimination ability. Significant cultural differences in identification ability were found in 92 % of the probes. The 20 probes that could be identified above chance in healthy participants of all countries and that could differentiate between patients and controls were selected for the final retronasal test. This test was well able to differentiate between controls and patients in different countries and showed a good coherence with the orthonasal test (r = 0.80) and a good retest-reliability (r = 0.76). Furthermore, it is age-independent. The strong cultural differences observed in retronasal identification underline the necessity to develop a culturally independent instrument. This retronasal test is easy to apply and can be used across different countries for diagnostics and clinical research.