Position paper on olfactory dysfunction: 2023

BACKGROUND: Since publication of the original Position Paper on Olfactory Dysfunction in 2017 (PPOD-17), the personal and societal burden of olfactory disorders has come sharply into focus through the lens of the COVID-19 pandemic. Clinicians, scientists and the public are now more aware of the importance of olfaction, and the impact of its dysfunction on quality of life, nutrition, social relationships and mental health. Accordingly, new basic, translational and clinical research has resulted in significant progress since the PPOD-17. In this updated document, we present and discuss currently available evidence for the diagnosis and management of olfactory dysfunction. Major updates to the current version include, amongst others: new recommendations on olfactory related terminology; new imaging recommendations; new sections on qualitative OD and COVID-19 OD; updated management section. Recommendations were agreed by all co-authors using a modified Delphi process. CONCLUSIONS: We have provided an overview of current evidence and expert-agreed recommendations for the definition, investigation, and management of OD. As for our original Position Paper, we hope that this updated document will encourage clinicians and researchers to adopt a common language, and in so doing, increase the methodological quality, consistency, and generalisability of work in this field.

Position paper on olfactory dysfunction.

Background: Olfactory dysfunction is an increasingly recognised condition, associated with reduced quality of life and major health outcomes such as neurodegeneration and death. However, translational research in this field is limited by heterogeneity in methodological approach, including definitions of impairment, improvement and appropriate assessment techniques. Accordingly, effective treatments for smell loss are limited. In an effort to encourage high quality and comparable work in this field, among others, we propose the following ideas and recommendations. Whilst the full set of recommendations are outlined in the main document, points include the following: • Patients with suspected olfactory loss should undergo a full examination of the head and neck, including rigid nasal endoscopy with small diameter endoscopes. • Subjective olfactory assessment should not be undertaken in isolation, given its poor reliability. • Psychophysical assessment tools used in clinical and research settings should include reliable and validated tests of odour threshold, and/or one of odour identification or discrimination. • Comprehensive chemosensory assessment should include gustatory screening. • Smell training can be helpful in patients with olfactory loss of several aetiologies. Conclusions: We hope the current manuscript will encourage clinicians and researchers to adopt a common language, and in so doing, increase the methodological quality, consistency and generalisability of work in this field.

[The Development of First Operating Microscopes from Zeiss Jena and Oberkochen to Series Production]. / Die Entwicklung der ersten OP-Mikroskope von Zeiss Jena und Oberkochen bis zur Serienfertigung.

Introduction: The history of the first operating microscopes from Zeiss is often confusing, not painstaking and partly contradictory because of the parallel development of Zeiss Jena (East Germany) and Zeiss Oberkochen (West Germany). Methods: To investigate the early beginnings of the construction of the operating microscopes documents of the Carl Zeiss Archive and the Optical Museum in Jena, the memoirs of Prof. Dr. Rosemarie Albrecht and some relevant publications were used. Results: The development of the first Jena operating microscope was initiated in 1949 by the ENT-physician Prof. Dr. Rosemarie Albrecht in the Soviet occupation zone. The first prototype was tested in the University ENT Clinic, Jena since summer of 1950. On the Leipzig Trade Fair in autumn 1952 the VEB Optik Carl Zeiss Jena presented the first operating microscope nationally and internationally. Series production began in 1953. The first operating microscope of Zeiss Oberkochen was primarily developed by technical designers (H. Littmann) as a colposcope. But in the Carl Zeiss Archive no documents could be found related to the cooperation with gynecologists. 1953 the operating microscope (OPMI 1) came into public and its series production started. From this date on, it was adopted by the otologist Prof. Dr. Horst Ludwig Wullstein to the needs of Otorhinolaryngology. Conclusion: The first Zeiss operating microscope came from Jena. The operating microscope from Zeiss Oberkochen had some advantages for the surgeons and won the competition in the future.

[Chemosensory Evoked Changes of Breathing Pattern During Propofol-induced Sedation]. / Chemosensorisch evozierte Atemänderungen während zweier Propofol-induzierter Sedierungsstadien.

BACKGROUND: The affective valence of an olfactory stimulus will be encoded in its respiratory response. Unpleasant odors shorten the inhalation of the first stimulated breaths in wakefulness and sleep. The aim of the present study was to assess the effekt of intravenous anesthetic propofol on the chemosensory evoked changes of breathing pattern. MATERIAL AND METHODS: 13 ASA 1/2 patients got intranasal chemosensory stimuli (H2S and CO2) by flow-olfactometer during "deep" (EEG-based bispectral analysis, BIS:≤60) and "moderate" (BIS>60) propofol-induced sedation with preserved spontaneous breathing. The duration of the in- and exhalation was analyzed for 5 breaths before and for 2 breaths after the onset of stimulation. RESULTS: During deep sedation respiratory reactions were observed only by CO2 irritation. During moderate sedation respiratory responses were evoked by H2S stimuli, too. In moderate sedation extensions of the inhalations of the first breath after both the unpleasant pure olfactory H2S stimuli and the trigeminal stimuli were more frequent than reductions. CONCLUSION: Olfactory stimuli change the breathing only during moderate sedation, trigeminal stimuli during deep and moderate propofol-induced sedation. In opposite to both wakefulness and sleep the duration of inhalation is often extended by H2S-stimuli during moderate sedation.

Position paper on olfactory dysfunction.

BACKGROUND: Olfactory dysfunction is an increasingly recognised condition, associated with reduced quality of life and major health outcomes such as neurodegeneration and death. However, translational research in this field is limited by heterogeneity in methodological approach, including definitions of impairment, improvement and appropriate assessment techniques. Accordingly, effective treatments for smell loss are limited. In an effort to encourage high quality and comparable work in this field, among others, we propose the following ideas and recommendations. Whilst the full set of recommendations are outlined in the main document, points include the following: - Patients with suspected olfactory loss should undergo a full examination of the head and neck, including rigid nasal endoscopy with small diameter endoscopes. - Subjective olfactory assessment should not be undertaken in isolation, given its poor reliability. - Psychophysical assessment tools used in clinical and research settings should include reliable and validated tests of odour threshold, and/or one of odour identification or discrimination. - Comprehensive chemosensory assessment should include gustatory screening. - Smell training can be helpful in patients with olfactory loss of several aetiologies. CONCLUSIONS: We hope the current manuscript will encourage clinicians and researchers to adopt a common language, and in so doing, increase the methodological quality, consistency and generalisability of work in this field.

[Global and Spatial Gustatory Function after Proven Unilateral Transsection of the Chorda Tympani]. / Globales und regionales Schmeckvermögen nach einseitiger Durchtrennung der Chorda tympani.

BACKGROUND: A transection of the chorda tympani results in loss of spatial gustatory function on the ipsilateral tongue. Most patients do not notice anymore this alteration. The cause is unclear. Do adjacent gustatory areas become more sensitive or is the gustatory perception rather independent of the size of stimulated area? METHODS: 51 patients with proven unilateral transection of the chorda tympani and 51 healthy subjects were tested for gustatory recognition thresholds. The methods used were the "three-drops-choice-technique" by Henkin to evaluate the whole mouth taste (global taste examination) and the "spatial taste test" to evaluate the local gustatory function on 4 areas of the tongue. The taste solutions were sweet, sour, salty and bitter with increasing concentrations. RESULTS: The global gustatory function of the patients and of the control group did not differ in either the 4 taste qualities but the composite score was increased within the group of patients. Most patients did not realize that. The spatial taste examination showed reduction of taste perception on 3 of the 4 gustatory areas of the tongue in the patients. The decreased gustatory function on the area of the transected chorda remained unchanged over time. The taste attenuation on the ipsilateral back area and the contralateral front area improved over time. CONCLUSION: Transection of chorda tympani also leads to an attenuation of spatial gustatory function in adjacent areas. Therefore, adjacent areas cannot be taken as reference. Instead, taste function has to be compared to the results of healthy probands.

[Position paper "Chemosensory testing for expert opinion in smell disorders"]. / Positionspapier "Die chemosensorische Testung bei der gutachterlichen Abklärung von Riechstörungen"

Providing expert opinion in the context of smell disorders is often challenging, not only with regard to general aspects of providing an expert opinion but particularly with regard to chemosensory testing. Currently there is no consensus which chemosensory test should be selected and how they should be executed. This positions paper from Committee on Olfaction and Gustation of the German Society of Otorhinolaryngology, Head and Neck Surgery aims to give concrete recommendations for chemosensory testing for providing expert opinion for smell disorders with regard to the selection and execution of these test.

[The regularity of the breathing pattern of both sitting and reclining adults is not different]. / Die Regelmäßigkeit der Ruheatmung sitzender und liegender Erwachsener unterscheidet sich nicht.

BACKGROUND: A prestimulatory regular breathing is required for the respiration-olfactometry. In a sitting position, just about every second prestimulatory breathing sequence fulfilled this requirement checking off -line. It should be examined whether breathing in reclining position is more regular. METHODS: The coefficients of variation of the time parameters of breathing in reclining and sitting position during 30 min were determined and compared. RESULTS: Breathing regularity did not increase in reclining position with 48 healthy persons (age group 1: 18 to 30 years, n = 24, 18 women; age group 2: > 55 years, n = 24, 13 women). The age and gender had no eff ect on the proportion of regular breathing. With 7 persons, the yield of 5 on each other following regular breaths was inadequate. Additionally one person excluded from our study was not able to breathe regularly without interruptions. CONCLUSION: The respiration-olfactometry cannot be performed in each person. It is not more successful in reclining than in sitting position.

Olfactory training for patients with olfactory loss after upper respiratory tract infections.

Olfactory training consisting of daily suprathreshold odor exposure over 12 weeks seems to improve olfactory function. It is unknown if a longer period of training might be more effective. A prospective non-randomized clinical study was performed including 39 patients with olfactory loss after an upper respiratory tract infection (URTI) of less than 24 months duration. Patients exposed themselves with suprathreshold concentrations of four odors (rose, eucalyptus, lemon, cloves) applied in ''Sniffin' Sticks'' felt-tip pens over 32 weeks. Olfactory function was performed before (T1), after 16 weeks (T2), and 32 weeks of training (T3) using the 'the Sniffin' Sticks test kit calculating the TDI score (Threshold, Discrimination, Identification). The mean TDI score showed a non-significant trend of improvement at T2, and was significantly increased at T3 (p = 0.021). Overall, 31 patients (79%) showed an increased TDI score at T3. The increase of TDI from T1 to T3 was 4.6 ± 5.1. Age, gender, duration and initial severity of olfactory loss had no influence on the improvement (all p > 0.05). Only patients with a D score lower than the median value of 8 showed a significantly higher increase of the D score at T3 (p = 0.004). The present study confirmed that olfactory training improves olfactory function in patients with olfactory loss after URTI. A longer duration of training over 32 weeks seems to increase the effectiveness in comparison to a 12-week period. This was tested in a completed German multicenter trial to be published soon containing a control group to include the effect of a spontaneous recovery after URTI.

[Ability of smelling is reduced reversibly by acute smoking and permanently by chronic smoking]. / Riechsinn wird durch akutes Rauchen reversibel und durch chronisches Rauchen dauerhaft geschädigt.

BACKGROUND: Whether smoking affects the sense of smell is in debate. To exclude a bias by presbyosmia, we analyzed the influence of acute and chronic smoking on the ability to smell in young adults. MATERIAL AND METHODS: 40 smokers (23 women, 17 men) aged between 18-34 years were included. They smoked in average 19.6 cigarettes per day and had an average of 7.96 pack years (minimum: 2.5; maximum: 25). The sense of smell was evaluated using the Sniffin' sticks© olfactory test-battery in 215 min 5 times. The impact of a 2 h controlled abstinence time and subsequent smoking of a cigarette were measured. 43 never smokers were tested as control group. RESULTS: Smoking had a 2-fold impact on the sense of smell: there was a reversible impairment after acute smoking and a permanent reduction of olfaction in relation to the pack years. In summary, the young smokers remained normosmic, although they showed significantly worse test results compared to the group of never smokers. The olfactory capacity of different groups of smokers differed up to maximum of 4.5 TDI points (sum of olfactory threshold-, discrimination- and identification-score). CONCLUSIONS: The damage caused by smoking seems to be settled in the border area between norm- and hyposmia. In case of an expert opinion the patient should be asked for the pack years and should keep 2 h controlled smoking abstinence prior to olfactory testing.

Differences in anosmic and normosmic group in bimodal odorant perception: a functional- MRI study.

So-called bimodal odorants are able to stimulate the intranasal trigeminal system at relatively low concentrations. Using them as stimuli, the current study focused on the interaction between the olfactory and trigeminal systems at a cerebral level. In the experiment, menthol was used at two concentrations, low and high, and these were delivered to two groups of subjects, a healthy control group and an anosmic group who were unable to perceive smells. A computer-controlled olfactometer based on principles of air-dilution was used to deliver the stimuli, while the brain functions were assessed by a functional magnetic resonance imaging (fMRI) technique. SPM5 was used for data analysis. The results showed that normosmic subjects exhibited activation in the anterior cingulate cortex (ACC) and posterior cingulate cortex (PCC), prefrontal cortex (PFC), and cerebellum. Whilst anosmic subjects activated the same area inside the anterior cingulate; moreover a cluster of activation was found in the left parahippocampal gyrus. In controls, an effect of stimulus intensity was localized between the anterior cingulated, the medial frontal gyrus and the cerebellum; such areas could not be found in anosmic subjects. These results suggest that the olfactory system modifies trigeminally mediated information causing an evident effect in the differentiation between stimulus intensities.

[Smokers develop a nasal obstruction in supine position]. / Raucher bekommen im Liegen eine nasale Obstruktion.

BACKGROUND: We found in a previous study a healthy non-smoker nose does not develop obstruction lying in supine position . We examined whether a designated smoker nose behaves consistently. MATERIAL AND METHODS: 39 healthy young smokers participated. The daily consumption was Ø 21 cigarettes. 9 test positions have been realized. Acoustic rhinometry was used for the estimation of nasal volumes and the nasal minimum cross-sectional areas as parameters for nasal respiration. Additionally, blood pressure and heart rate were measured to control the cardiovascular behavior. RESULTS: The total nasal volume decreased significantly lying down. Only one third of the volunteers noticed this obstruction. Going upstairs all measured parameters increased. 2 min later all rhinometric parameters, the diastolic blood pressure and heart rate had reached its baseline level. Systolic blood pressure took about 4 min. CONCLUSIONS: A cigarette smoke-induced nasal obstruction can be demonstrated during supine position using the acoustic rhinometry. One third of smokers noted a deterioration of nasal breathing. During stairs climbing the sympathic tone is increasing followed by nasal decongestion, raised blood pressure and heart rate. If smokers complaint of nasal obstruction in lying position - whether alert or during sleep - it is advisable to lift the bed-head. In medium term a therapy of chronic rhinitis with topical corticosteroids, in longer term a smoking cessation is recommended.

[Volume alterations in the gray matter of anosmic subjects. Lessons we can learn from voxel-based morphometry]. / Volumenänderungen der grauen Hirnsubstanz bei Anosmikern. Erkenntnisse durch voxelbasierte Morphometrie.

Alterations in the central nervous system in patients with a loss of sense of smell are well documented for the olfactory bulb (OB). Here we present a voxel-based morphometry (VBM) study on cerebral alterations in the gray matter of patients with anosmia above the OB. 3-Tesla MRI datasets were obtained from 17 patients with anosmia as well as from 17 normosmic controls. Data processing and evaluation was performed using the SPM5 software package (Wellcome Department of Imaging Neuroscience Group, London, UK) and the implemented VBM5 toolbox. Patients with anosmia showed a significant volume decrease in the gray matter in the primary olfactory cortex as well as in secondary olfactory areas (insular cortex, orbitofrontal cortex, cingulate cortex and hippocampus). Furthermore, volume decreases in areas like the nucleus accumbens with adjacent subcallosal gyrus and the dorsolateral prefrontal cortex were found. Longer disease duration was associated with more profound alterations in the gray matter. VBM is appropriate to document brain alterations in patients with olfactory disorders.

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.

[Detection of olfactory areas in functional MRI--how many repetitions are necessary?]. / Darstellung olfaktorischer Areale mittels funktionellem MRT--wieviele Reize sind notwendig?

BACKGROUND AND PURPOSE: A useful tool for the investigation of the human olfactory system is functional magnetic resonance tomography (fMRI). Since the length of the fMRI examination is a limiting factor for its usefulness in clinical routine in this study a fast, reliable paradigm should be found in order to reduce the overall examination time and the olfactory habituation. METHODS: A MRI-compatible constant flow olfactometer was developed. 9 healthy normosmic subjects were stimulated 16 times with the odorant phenyl-ethyl-alcohol (PEA) using an event-related design. The statistical evaluation of the data was performed by the MATLAB based SPM5 software package. RESULTS: The group analysis showed cerebral activations within the insula, the adjacent operculum and orbitofrontal cortex bilaterally. Furthermore, bilateral activations were measured in the cingulum, piriform cortex and the cerebellum. All mentioned areas could be already identified after 8 repetitions of odorant condition. Bilateral insular activations and activations in the left piriform cortex were even shown after 4 repetitions. In the single subject analysis, all 9 subjects exhibited insular activity and in 3 subjects showed activation of the piriform cortex after 4 repetitions. CONCLUSION: In olfactory fMRI, stimulus repetition more than 8 did not improve the quality and reliability of the results. Therefore, 4-8 stimuli are expected to be sufficient.

Olfactory bulb ventricles as a frequent finding--a myth or reality? Evaluation using high resolution 3 Tesla magnetic resonance imaging.

Data on the prevalence of persistent olfactory bulb ventricles (OBV) in humans remain contradictory. The aim of this study was to investigate the hypothesis of large cystic-like OBVs filled with cerebrospinal fluid (CSF) as a frequent finding in magnetic resonance imaging (MRI). Fifty normosmic volunteers (25 men and 25 women, mean 40 years) underwent 3 Tesla MRI of the anterior skull base. Normal smell function was determined by testing of the odor threshold discrimination identification score using the Sniffin' Sticks test kit. The voxel size of the constructive interference in steady state (CISS) sequence was 0.4×0.4×0.4 mm (TR 12.18 ms, TE 6.09 ms) using a 12-channel head coil. Image quality was rated by three observers according to predefined criteria on an ordinal scale. Additionally, contrast-to-noise (CNR) and signal-to-noise (SNR) ratios were calculated. Quantitative signal intensity (SI) measurement of olfactory bulb (OB) structures and small Virchow-Robin spaces (VRS) was performed using multi planar reconstruction mode. Ninety-one OBs were eligible for evaluation. Image quality was rated as adequate in 55% and as excellent in 36% of cases. CNR and SNR calculations resulted in values of 21.59 and 19.06, respectively. Wilcoxon signed rank test revealed significant higher SI values for OB center compared to OB surface (P<0.001) and to OB base (P<0.001) but also significant lower SI values compared to small VRS (P<0.001) in 94.5%. In 5.5%, SI measurement revealed signs for CSF-filled structures in the OB. High-resolution 3 Tesla MRI did not verify the hypothesis of large cystic CSF-filled OBVs as a frequent finding although evidence is growing that the hyperintense signal in the center of OBs might be associated with interstitial or finely dispersed CSF/fluid or with tiny, histologically detectable remnants of OBVs.

[Olfactory dysfunctions are substantially more frequent than they are complained]. / Riechstörungen sind wesentlich häufiger als sie beklagt werden.

BACKGROUND: Probably less than 0.1% of the population of the western world might seek medical advice because of olfactory or gustatory dysfunctions. In contrast, it can be assumed that the prevalence of olfactory dysfunction is about 20%. The estimated number of unreported cases must be high. Related to the population of the city of Jena it shall be investigated, how many patients visit a doctor because of an olfactory dysfunction. MATERIALS AND METHODS: Data of all patients, who underwent olfactory testing at the ENT department of the university hospital in Jena between 1998 and 2004 and had their main residence in Jena were identified. Based on subjective self-assessment of smelling function and on different olfactory test procedures subjectively smelling-disturbed people and objectively smelling-disturbed people were separated. Calculation of the prevalence was based on data from the registration office of Jena. RESULTS: Related to the total population of Jena 0.23% of Jena's inhabitants underwent olfactory testing procedure between 1998 and 2004. 0.08% complained about subjective olfactory dysfunction. Only 0.05% were really suffering from olfactory dysfunction confirmed by olfactory testing. DISCUSSION: Only a small percentage of Jena's inhabitants visit a doctor because of olfactory dysfunction. Therefore, in Jena no other health behaviour concerning olfactory disorders can be observed than in other industrial countries. The estimated number of unreported cases of olfactory disturbances is higher than supposed. The medical professional societies should to an increased education of medical doctors and patients regarding symptoms, refined diagnostics, outlook and risen therapeutical chances of olfactory disorders.

[Gustatory input affects breathing pattern: a method for objectifying of gustatory perception]. / Geschmacksreize verändern das Atemmuster: Methodik zum objektiven Nachweis einer Schmeckwahrnehmung.

INTRODUCTION: There is currently no commercial tool available to examine gustatory perception objectively. We investigated whether early changes of breathing patterns can be evoked by gustatory stimulation, and whether there are differences between sweet, sour, salty and bitter stimulation. METHODS: Using a randomised design, 34 young adult subjects (15 male, 19 female; average age: 24.6 years, median: 23, minimum: 22, maximum: 33) with normal sense of taste were stimulated by supra-threshold taste solutions for approximately 6 s. A pressure sensor recorded nasal respiratory changes using LabView software. The interstimulus-interval was longer than 1 min depending on regular status of unstimulated breath. Durations of inspiration (DIN) and expiration (DEX) were analysed. Values outside the 95%-confidence intervals were defined as gustatory evoked changes. RESULTS: The rates of alteration differed significantly in the first, second and third post stimulatory breath. The rates were regarding to DIN between 25.87% and 36.49%, and regarding to DEX between 35.31% und 43.13%. Blank stimuli showed a rate between 5.97% and 8.96% in DIN and in DEX between 10.66% and 11.48%. There were no differences in reaction frequency between the four taste solutions. Every subject reacted to gustatory stimulation more frequently than to blanks. DISCUSSION: Like other sensory modalities, gustatory input is able to evoke early respiratory orienting responses. The reaction rate is not dependent on the hedonic component of the gustatory input, as has already been shown for respiration-olfactometry.

[Investigations of nasal deposition efficiency of wheaten flour and corn starch]. / Untersuchungen zur nasalen Depositionseffizienz für Weizenmehl- und Maisstärke-Staub.

BACKGROUND: In-vivo-evaluation of the nasal deposition efficiency is problematic, because a postnasal measurement of the dust particle concentration is difficult. A new method is represented, which measures in front of the nose the dust loading after ortho- and retronasal passage relative easily. METHODS: 36 healthy subjects were nasally dust-exposed sitting in an exposure chamber. With the help of dust sampling system (Respicon) the particle size-referred dust loading before and after the nasal airflow passage was gravimetrically determined. The constant flow rate was 3.111 per minute. A contamination with breathing air was excluded by an active velopharyngeal closure. The subjects breathed orally over a breathing tube clean air. They were in each case 15 min exposed to the constant pre-nasal wheaten flour or corn starch dust produced over a brush disperser (Palas, RBG 1000). The time interval between both exposures was seven days excluding cross over effects. RESULTS: The deposition efficiency of both types of food powder was particle size dependent. Highest it was -as expected- with the particle sizes between 5-100 microm. Here it lay between 92% and 99%. The small particles of wheaten flour respective corn starch with an aerodynamic diameter between 1-4 microm deposited nasally 31% respectively 74%. CONCLUSIONS: The new relatively simple method of measurement of nasal deposition efficiency does not load the deeper respiratory tract. The results confirm the good filtering capability of the healthy nose for large dust particles. The nasal deposition of particles smaller than 5 microm is reduced but not absent. The small dust particles of wheaten flour and corn starch are very different nasally deposited. The different electrostatic charges of the two food powders may explain these differences.