[Post-COVID patients with persistent chemosensory symptoms are rare in the general population]. / Post-COVID-Patienten mit persistierenden chemosensorischen Symptomen sind in der Bevölkerung selten.

OBJECTIVE: The prevalence of long-/post-COVID-associated chemosensory symptoms is reported in the literature to be significantly higher than clinical reality reflects. METHODS: 1. N= 4062 adults acutely infected with SARS-CoV-2 and their symptoms transmitted by the Jena health office to the Robert Koch Institute between March 2020 and September 2021 were evaluated. 2. Part of the same cohort (N = 909 of 4062) answered an extensive questionnaire at least 3 months after the start of the infection, including existing chemosensory post-COVID-associated complaints. 3. Fourteen post-COVID Jena patients with chemosensory symptoms who had become acutely infected during the same period were diagnosed, treated and advised in our ENT specialist outpatient clinic. RESULTS: The prevalence of chemosensory symptoms at the onset of infection was 19% (600/3187). About every second written respondent of the formerly acutely infected (441/890) remembered chemosensory symptoms during their COVID-19 infection. Of these, around 38% (167/441) complained of persistent chemosensory post-COVID symptoms after an average of 14.5 months. Only 2.3% (14/600) of the previously acutely infected patients with chemosensory symptoms sought medical help in a special consultation. Quantitative chemosensory damage could only be objectified in half, i.e. 1.2% (7/600) of the total cohort. CONCLUSIONS: Despite a high prevalence of subjective chemosensory symptoms in acutely and formerly SARS-CoV-2 infected people, there is only a low need for specialized treatment, so that, unlike other post-COVID-associated complaints, the healthcare system as a whole appears to be less significantly burdened.

[Reported and measured olfactory and gustatory findings in a long-COVID cohort]. / Berichtetes und gemessenes Riech- und Schmeckvermögen in einer Long-COVID-Kohorte.

INTRODUCTION: Disorders of the sense of smell and taste are often complained as a long-COVID symptom. In a special long-COVID consultation (ENT-LCS), we wanted to figure out how large the proportion of pathological olfactory or gustatory diagnoses actually is in this cohort. METHODS: 48 adult patients who visited the ENT-LCS because of their own suffering were asked about their history, rated their ability to smell (SER) and taste (SES) with school grades and completed the extended Sniffin' Sticks test and the 3-drop test as a taste test. Diagnoses were made from the SDI smell score and the total taste score using normative values. Correlations were calculated between the measured scores and the self-assessment and between SER and SES. RESULTS: Pathological chemosensory diagnoses were present in 90%. Pathological olfactory diagnoses were twice as common as gustatory ones. No pathological diagnosis could be verified in 10% of the cohort. Anosmia-ageusia syndrome was diagnosed in six patients. SER correlated strongly with SDI. SES correlated moderately with SScore-total. SER correlated strongly with SES. CONCLUSIONS: There is a risk of smell-taste confusion when interpreting reported chemosensory symptoms. This is another reason why reference is made to the importance of quantifying the chemical senses with validated tests.

[Subjective and objectified smell and taste disorders from an ENT post-Covid-19 consultation]. / Subjektive und objektivierte Riech- und Schmeckstörungen aus einer HNO-Post-COVID-19-Sprechstunde.

INTRODUCTION: Olfactory disorders are among the four most common post-COVID-19 complaints. The aim of our prospective study from a university ENT post-COVID consultation (PCS) was to substantiate the symptoms with psychophysical test results. METHODS: After an ENT examination, 60 post-COVID-19 patients (41 women) were asked in writing about their medical history. Their ability to smell was tested using the extended Sniffin' Sticks test battery and their ability to taste was determined using the 3-drop test. From these data, three quantitative olfactory (RD) and gustatory (SD) diagnoses could be defined from normal value tables. Every second patient took part in a control examination. RESULTS: Up to the first examination, 60 patients reported smell and 51 taste disorders; their average duration was 11 months in both cases. Objectified pathologic RD and SD had 87% and 42% of the total cohort, respectively. Every third patient suffered from an objectified combination of olfactory and gustatory damage. About every second patient complained of parosmia. Parosmic patients with two visits came earlier for a check-up. Six months after the initial examination, the detection thresholds, the TDI and the RD had improved in these patients. The self-assessment of olfactory ability had not changed. CONCLUSIONS: Objectified pathologic RD persisted in our PCS for a mean of 1.5 years from the onset of infection. Parosmics had a better prognosis. For the healthcare system and especially for the patients affected, they continue to be a burden even after the pandemic.

High prevalence of long-term olfactory dysfunction confirmed by olfactory testing after a community COVID-19 outbreak.

PURPOSE: The prevalence of long-term olfactory and gustatory dysfunction in participants suffering from sudden chemosensory loss due to coronavirus disease 2019 (COVID-19) is unknown. Furthermore, evaluations of the reliability of participants' self-reporting of olfactory function (SOF) and gustatory function (SGF) using extended objective psychophysical testing are missing. METHODS: In this population-based cohort study in a PCR-tested community in Thuringia, Germany, olfactory function was extensively examined 4 months after a COVID-19 outbreak using the "Sniffin Sticks" test battery to determine the TDIa score, i.e., the sum of results obtained for threshold, discrimination, and identification scores averaged for both nasal sides. Gustatory function was assessed using the three-drop test resulting in the gustatory composite score (CSg). The data were compared with SOF and SGF. RESULTS: Of 43 adult convalescents (median age: 68 years; 58% female) after SARS-CoV­2 infection, 18 participants (42%) had olfactory complaints due to SOF, one participant (2%) complained of taste disturbance due to SGF. The TDIa was 22.0 ± 5.9. Normosmia, hyposmia, and anosmia were seen in 17, 18, and eight participants, respectively. TDIa correlated with SOF (rs = -0.434, p = 0.004); CSg was 23.5 ± 2.7. Normogeusia and hypogeusia were objectified in 39 and four participants, respectively. The prevalence of long-term olfactory dysfunction and gustatory dysfunction in the study group was 60.5 and 9.3%, respectively. CONCLUSION: The SOF was reliable, especially for participants who felt a sudden chemosensory dysfunction during the outbreak. At 4 months after SARS-CoV­2 infection, a high proportion of participants were dysosmic, whereas nearly all of them had normal taste function.

[Smell of fish slightly increases the heart rate and only one parameter of variability in adults]. / Gesunde erhöhen unter Fischgeruch die Herzfrequenz nur schwach und nur einen Variabilitätsparameter.

INTRODUCTION: Cardiac olfactory stimulus reactions could expand the range of objectifying test methods for testing olfactory function. In a pilot study, it was investigated whether and how pleasant and unpleasant odors change the heart rate (HR) and its variability. METHODOLOGY: 32 healthy people with normal smell function inhaled nasally for seven minutes the smell of four Sniffin' Sticks (banana, fish, garlic and rose) alternating with blanks. At the same time, the ECG was recorded and offline the NN intervals (distance of the R-waves) and six parameters of the heart rate variability were determined and compared with the values of a blank irritation using generalized estimation equations (GEE). In addition, the values of the subjective assessment of intensity and hedonic valence of the four odors were correlated with the heart rate. RESULTS: The unpleasant odor fish smell increased the heart rate slightly but significantly in the first stimulus minute. The fish smell increased a single heart rate variability parameter (LF/HF) during the continuous stimulation, too, and showed a significant moderate correlation between HR and the scaling of intensity and hedonics in the first stimulus minute. The pleasant and the garlic odors did not affect the analyzed cardiac parameters. CONCLUSIONS: Olfactory evoked changes in HR should be further investigated as an indicator of the integrity of olfactory function. The most promising and time- and cost-effective is probably an 1-minute irritation with the unpleasant fishy smell from the identification set of the Sniffin' Sticks during the ECG recording.

[Breath changes induced by short chemosensory stimuli cannot be intentionally suppressed]. / Atemänderungen durch kurze chemosensorische Reize lassen sich nicht absichtlich unterdrücken.

INTRODUCTION: Breathing changes induced by repeated short olfactory stimuli are used as an objective indicator of the integrity of the olfactory system. Until now, it has not been investigated whether chemosensorically induced changes in inspiratory and expiratory time parameters can be suppressed intentionally. The same applies to breathing changes due to weak CO2 stimuli. METHODOLOGY: 34 healthy adult normosmics were stimulated during relaxed regular nasal breathing using a flow olfactometer with nine differently concentrated H2S and three weak CO2 stimulation pulses. They were instructed to intentionally maintain regular nasal breathing during the stimulation. A significant breathing change was present if the duration of the inspiration (DIN) or the expiration (DEX) of the first stimulatory breath was outside the double standard deviation of the mean of five prestimulatory regular breaths. These could be shortened or extended the DIN or DEX. RESULTS: Despite high motivation, the chemosensorically induced breathing changes could not be suppressed intentionally. Rest breathing reacted to both stimulants by changes in both the inspiratory and the expiratory time parameters. However, it outweighed the expiratory reactions. CO2 evoked more breathing changes than H2S. The frequency of reaction rate of H2S stimuli was not concentration-dependent. Strong H2S stimuli induced more frequent shortening than prolongation of DEX. CONCLUSIONS: Chemosensorically triggered breathing changes cannot be suppressed intentionally. They therefore provide an additional objective tool to check the functionality of nasal chemosensory afferents.

[The active butanol detection threshold remains the same during exercise]. / Die aktive Butanol-Wahrnehmungsschwelle bleibt bei körperlicher Belastung gleich.

BACKGROUND: The active butanol detection thresholds (B-DT), determined using the sniffin' sticks, show a high intra- and inter-individual test-retest reliability, although the internal stimulus concentration may vary considerably depending on the dilution of the external stimulus concentration with odorless ambient air during active sniffing. There are various hypotheses for this surprising result. In this study, it should be tested whether a larger respiratory effort (vigor) under physical stress changes the active B-DT. METHODS: In 28 young, healthy, normosmic adults, sitting on a stationary bicycle ergometer at rest phase, during aerobic exercise and in the recovery phase, the monorhinal B-DT using Sniffin' Sticks were determined. Various vital parameters such as blood pressure, heart frequency, body temperature, respiratory frequency and blood lactate characterized the three test phases. The individual stress perception was estimated according to the Borg scale. RESULTS: The B-DT did not change in the three test phases. All examined vital parameters were significantly larger in the loading phase than in the resting phase. In the case of a moderate to severe stress sensation (Borg-scale: 13-15), an aerobic physical stress could be confirmed on the basis of the vital parameters. CONCLUSIONS: The investigations support the hypothesis that vigor is not the decisive factor for a constant olfactory perception of external equal stimulus concentrations. The integration of internal stimulus concentration and nasal flow velocity and the empirical evaluation of the current odor concentration probably play a greater role.

[Hydrogen sulphide stimuli shorten exhalation during sleep as well as in wakefulness]. / Schwefelwasserstoffreize verkürzen im Schlaf- wie im Wachzustand die Ausatmung.

BACKGROUND: In the attentive waking state, pleasant odours often prolong inhalation while unpleasant odours often shorten the exhalation. It should be checked whether this induced breathing pattern is maintained even during sleep. METHODOLOGY: 23 healthy normosmic adults were examined by polysomnography for one night and randomized pulsed either with H2S, phenylethyl alcohol (PEA) or CO2 via a flow olfactometer. The determination of the sleep stages was based on the standard polysomnography curves. From the breathing curves (respiratory nasal pressure breathing, thoracic or abdominal belt breathing) a low-artefact curve was selected and seven breaths were measured from their breathing signal around the trigger impulse. The duration of inspiration (DIN) and the duration of the expiration (DEX) were determined from the six prestimulatory breaths and from breath with the stimulus onset and thus defined a reaction index (RI) indicating whether there is a significant change in shortening or prolonging DIN and/or DEX. These different RI were corrected by the spontaneous baseline RI and analysed according to the type of stimulus and the sleep stages. RESULTS: Reaction indices with reductions of DEX were larger than spontaneous RI and RI for PEA and H2S stimulation. In the case of CO2 irritation, RI with reductions of DIN and DEX were larger than with olfactory stimulation. All RI were equal in their amount between sleep stages. In REM, the difference between olfactory RI with shortened DEX between H2S and PEA stimulation was greatest. CONCLUSION: When stimulated with an unpleasant smell in sleep, the respiratory reaction pattern from the awake state is preserved. RI with shortened DEX can be considered as an imperfect arousal.

[Detection rates of chemosensory evoked Potenzials with healthy and anosmic subjects]. / Erkennungsraten von chemosensorisch evozierten Potenzialen bei gesunden und anosmischen Erwachsenen.

BACKGROUND: The detection rate of olfactory chemosensory event-related EEG Potentials (oCSERP) and trigeminal chemosensory event-related EEG Potentials (tCSERP) is also dependent on the stimulants and the evaluator of the averaged EEG curves. METHODS: In 45 subjects with age-appropriate normal olfactory capacity (NP) and 20 anosmics (AN), oCSERP (stimulation by hydrogen sulphide, H2S 6 ppm and phenylethyl alcohol, PEA 30 % v/v,) and tCSERP (irritation with CO2 20-60 % v/v, intensity standardized) were derived by default. Two investigators categorized the averaged EEG curves in: CSERP recognizable, no CSERP recognizable and artefact. Investigator 1 knew whether the subject was a NP or an AN, and which stimulants was used, whereas investigator 2 lacked this information. RESULTS: AN needed higher trigeminal stimulus concentrations but showed same intensity ratings compared to NP. The attention (tracking game) did not deteriorate in the course of test. The detection rate of H2S-CSERP was higher than that of PEA-CSERP. The match of H2S-CSERP detection rates between the two investigators was higher than that of PEA-CSERP and CO2-CSERP. CONCLUSION: For the standard derivation of oCSERP, stimulation with H2S is usually sufficient. Stimulation with PEA and CO2 as well as a blinded investigator is not necessary.

[Aerobic exercises during mouth breathing do not change the detection threshold of H2S]. / Aerobe Belastung bei Mundatmung verändert die Wahrnehmungsschwelle für H2S nicht.

BACKGROUND: In a previous study, the detection threshold for H2S during aerobic exercise worsened with forced nasal breathing. The cause remained unclear. It is to be examined how the detection threshold changes with exclusive mouth breathing. MATERIAL AND METHODS: During a resting phase, an aerobic physical load and subsequent recovery phase, different H2S concentrations were applied inspiratory-synchronously intranasal using a flow-olfactometer in a staircase procedure. The missing nasal breathing was objectified online and offline. The reaction times were determined. In parallel, various vital parameters have been measured. RESULTS: The passive detection thresholds for H2S between the load and recovery phases did not differ. In the resting phase, the threshold was highest. The reaction times were not different in the three experimental phases. CONCLUSION: An increased sympathetic tone, resulting from an approximately half-hour aerobic exercise, did not change the passive olfactory threshold for H2S during oral respiration compared to the subsequent recovery period. The high olfactory threshold in the resting phase might be explained by initial adaptation difficulties to the experimental conditions.

[On the assessment of spontaneous respiratory changes in respiration-olfactometry]. / Zur Bewertung spontaner Atemänderungen bei der Respirations-Olfaktometrie.

INTRODUCTION: Alterations of breathing pattern evoked by odors are used to proof the integrity of the olfactory system in the sense of respiratory olfactometry. Spontaneous breathing changes normally cannot be distinguished from evoked changes. It is therefore necessary to repeatedly apply stimuli with a pure odorant during tidal breathing, randomized with neutral air, to detect a majority of olfactory-evoked respiratory changes. METHODS: In 26 adult normosmics, 15 H2S and 15 neutral air stimuli (duration: 2 sec) were randomly applied with an interstimulus interval of at least 1 minute, using a flow olfactometer. Before stimulation, the respiration was not allowed to scatter significantly (variation coefficient of the duration of inspiration (DIN) and expiration (DEX) ≤0.1). A respiratory response was fulfilled when respectively DIN and DEX of the stimulus breath exceeded the double standard deviation of the same parameters in the five preceding respiratory cycles. The number of reactions was normalized to the number of stimuli and to the off-line as regularly calculated respiratory complexes and thus reaction indices were formed. RESULTS: H2S stimuli clearly evoked more respiratory changes than neutral air stimuli. DIN and DEX decreased with olfactory stimulation more frequently than with an application of neutral air. Extensions of DIN and DEX were not different between the two stimulus qualities. CONCLUSIONS: Only the randomized nasal stimulation with an odor and a blank makes the respiration-olfactometry meaningful.

[Aerobic exercises worsen the detection threshold of short H2S pulses]. / Aerobe Belastung verschlechtert die Wahrnehmungsschwelle kurzer H2S-Impulse.

BACKGROUND: Whether smelling is reduced during aerobic exercise is described contradictorily in the sparse literature. MATERIAL AND METHODS: To clarify this question, in healthy subjects the passive detection thresholds for short H2S stimuli were determined by means of a flow olfactometer in an inspiration-synchronous manner during nasal breathing in a staircase procedure during a resting phase, a subsequent submaximal load on a bicycle ergometer and a subsequent recovery phase. In parallel, the measurements of heart rate, blood pressure, blood lactate and body temperature were monitored to confirm an aerobic exercise. RESULTS: The participants achieved the highest values for the detection threshold in the load phase. By means of rm-ANOVA and post-hoc tests, a significant difference in the mean values of detection thresholds between the measurements at rest and during cycling as well as between the recovery and load phases was observed. However, the mean values of the detection thresholds between the resting and recovery phases did not differ. CONCLUSION: The worsening of olfactory detection thresholds during acute aerobic physical exercise and their immediate improvement during recovery phase to rest values suggests that the detection threshold is influenced by exercise. The most probable cause for this is a dilution effect caused by additional inflowing neutral ambient air in the case of forced nasal breathing.

Imaging of lamination patterns of the adult human olfactory bulb and tract: in vitro comparison of standard- and high-resolution 3T MRI, and MR microscopy at 9.4 T.

PURPOSE: Neurological and smelling disorders (e.g. Alzheimer's disease, sinonasal disease) negatively affect the microstructural integrity of the olfactory bulb's (OB) cortical layers. Recovery processes depend on active restoration of this microstructural integrity enabled by neuroneogenesis in the OB. The aim of this study was to evaluate lamination patterns of the OB and adjacent tract (OT) using high resolution MRI at 3 Tesla (T) as well as MR microscopy at 9.4 T in comparison with histological sections. MATERIAL AND METHODS: Twenty-four human OBs were imaged in vitro using standard (2mm slice thickness) and high resolution (0.2mm slice thickness) T1w and T2w MR imaging at 3T. Based on signal intensity differences, the number of OB layers and the OB lamination patterns were assessed by two observers in consensus. Results were compared using Wilcoxon test. Signal intensity profiles were compared to reference Nissl stained histological sections and imaging results of MR microscopy. OT lamination patterns were assessed and different configurations of cross sectional areas were compared to macroscopic results and OB/OT lamination patterns. RESULTS: Standard resolution at 3T identified three layers in 8.3%, two layers in 83.3%, and one layer in 8.3%. High resolution at 3T (4 layers in 91.7%, 3 layers in 8.3%) significantly performed better (P<0.001). Signal intensity profile analysis at 3T and 9.4 T (yielding up to 6 different signal intensities) correlated with histological sections and enabled quantitative evaluation of OB lamination patterns. 3T MRI of the OT revealed two separate signal intensities in T2w in 73%, a hyperintense core and a hypointense sheath, and the number of OT signal intensities positively correlated (ρ=0.541, P=0.006) with the increasing complexity of the OTs' cross sectional area configurations. Additionally, cross sectional area configurations correlated with macroscopic results (ρ=0.558, P=0.002) and OB lamination patterns (ρ=0.446, P=0.022). CONCLUSIONS: 3T MRI and MR-microscopy indicate the possibility to identify the lamination pattern of the human OB/OT and to reflect the histological status. If further development will be able to provide technical equipment that complies with the condition of human in vivo high resolution imaging achieving a good enough signal noise ratio, the method of signal intensity profile analysis could prospectively enable scientists to assess the OB's microstructural status in neurological and smelling disorders.

Comparison of the orthonasal and retronasal detection thresholds for carbon dioxide in humans.

Several studies have investigated the orthonasal detection threshold for carbon dioxide (CO(2)) in humans. The aim of current study was to investigate whether 24 healthy young subjects exhibited differences of CO(2) detection thresholds during orthonasal or retronasal stimulation. As nasal mucosa is believed to desensitize to CO(2) concentrations at or below 4% (v/v) during expiration, the second aim of the study was to explore the influence during nasal versus oral breathing on the detection thresholds. CO(2) stimuli of varying concentrations and a duration of 1000 ms were applied with an air-dilution olfactometer in either the anterior nasal cavity or the nasopharynx during nasal respectively oral breathing. In these 4 conditions, the mean CO(2) detection thresholds using the staircase forced-choice procedure were between 3.9% and 5.3% (v/v). Statistical analysis revealed a significant difference between orthonasal and retronasal stimulation. The CO(2) detection threshold was lower in retronasal stimulation. The nasopharyngeal mucosa is more sensitive to perithreshold CO(2) stimuli than the nasal mucosa. The breathing route had no influence on the detection thresholds. The results of this study indicate that the natural contact of the nasal mucosa with approximately 4% (v/v) CO(2) during nasal expiration does not influence CO(2) detection thresholds.

Anosmia leads to a loss of gray matter in cortical brain areas.

Chronic olfactory disorders, including the complete loss of the sense of smell (anosmia), are common. Using voxel-based morphometry (VBM) in magnetic resonance imaging (MRI), structural changes in the cerebral gray matter (GM) of a group of patients with anosmia compared with a normosmic, healthy control group were evaluated. Patients with anosmia presented a significant decrease of GM volume mainly in the nucleus accumbens with adjacent subcallosal gyrus, in the medial prefrontal cortex (MPC) including the middle and anterior cingulate cortices, and in the dorsolateral prefrontal cortex (dlPFC). These areas are part of the limbic loop of the basal ganglia and except the dlPFC secondary olfactory areas. They also play an important role in many neurological diseases. Furthermore, volume decreases in smaller areas like the piriform cortex, insular cortex, orbitofrontal cortex, hippocampus, parahippocampal gyrus, supramarginal gyrus, and cerebellum could be seen. Longer disease duration was associated with a stronger atrophy in the described areas. No local increases in the GM volume could be observed. A comparison with results of an additionally executed functional MRI study on olfaction in healthy subjects was performed to evaluate the significance of the observed atrophy areas in cerebral olfactory processing. To our knowledge, this is the first study on persisting structural changes in cortical GM volume after complete olfactory loss.

[Hyposmics have less evoked respiratory orienting reactions than normosmics]. / Hyposmiker haben weniger evozierte respiratorische Orientierungsreaktionen als Normosmiker.

BACKGROUND: Respiratory orienting reactions after olfactory stimulation can be seen as an indicator of an intact olfactory processing. Olfactory stimuli have to be recognized and they have to be important for a subject in order to generate a respiratory orienting reaction. METHODS: Hyposmic patients were stimulated pre-nasally with one sub-threshold and two supra-threshold concentrations of hydrogen sulfide (H(2)S) using a flow olfactometer. Nasal respiration was measured unilaterally using a differential pressure transducer. The data were processed after digitalization with the LabView software package. Duration of inspiration (DIN) and duration of expiration (DEX) were used as test variables for the evaluation of a regular resting respiration or a poststimulation respiration complex (PRC), respectively. RESULTS: The rate of poststimulatory respiration alterations (47%) in hyposmic subjects was significantly higher than the rate of spontaneous changes after resting respiration (31%). The reaction rate was not stimulus concentration-dependent. In spite of the stimulus recognition poststimulatory respiration alterations were less often in hyposmic subjects compared to normosmic subjects. DISCUSSION: Maybe this is due to the reduced significance of perceptible odors for hyposmic persons.

Electrophysiologic assessment of olfactory and gustatory function.

This chapter reviews approaches for assessing human and gustatory function using electrophysiologic methods. Its focus is on changes in electrical signals, including summated generator potentials that occur after nasal or oral stimulation. In the first part of the review, we describe tools available to the clinician for assessing olfactory and nasotrigeminal function, including modern electroencephalography (EEG) analysis of brain responses both in the time domain and in the time-frequency (TF) domain. Particular attention is paid to chemosensory event-related potentials (CSERPs) and their potential use in medical-legal cases. Additionally, we focus on the changes of summated generator potentials from the olfactory and respiratory nasal epithelium that could provide new diagnostic insights. In the second part, we describe gustatory event-related potentials (gCSERPs) obtained using a relatively new computer controlled gustometer. A device for presenting different pulses of electrical current to the tongue is also described, with weaker pulses likely reflecting gCSERPs and stronger ones trigeminal CSERPs. Finally, summated generator potentials from the surface of the tongue during gustatory stimulation are described that may prove useful for examining peripheral taste function.

Improvement of olfactory function after sinus surgery correlates with white matter properties measured by diffusion tensor imaging.

Impaired olfaction is associated with a volume decrease in the olfactory bulb as well as in the gray matter of cortical olfactory areas. On the other hand, restitution of an impaired olfaction results in a regain of volume in these regions. Studies investigating similar changes in the cerebral white matter are virtually not existent. The aim of this prospective study therefore was to investigate cerebral white matter using magnetic resonance diffusion tensor imaging (DTI). 31 patients (54±13years) with olfactory impairment (chronic rhinosinusitis) and planned functional endoscopic sinus surgery (FESS) were included. Magnetic resonance imaging (MRI) data sets were acquired pre-operatively and 3months after surgery. Pre- and postoperative olfactory testing was performed to assess the olfactory threshold, discrimination, and identification (TDI) score. A significant postoperative TDI improvement by 9.06±8.81 points was observed. Two groups were subsequently formed - one with relevant postoperative olfactory gain (ΔTDI≥10 points, 12 patients) and one without gain (ΔTDI<10 points, 19 patients). DTI parameter showed a significant correlation with the TDI score in the left anterior cingulate cortex and the right amygdala. In the group with relevant olfactory improvement higher values of fractional anisotropy and apparent diffusion coefficient were found in the right parahippocampal area and in the white matter below the left inferior temporal sulcus. Tract-specific diffusion property analysis revealed significant group differences in the cingulate cortex in spatial relationship to the perisplenial cortex. Overall, this prospective study indicates structural changes in white matter after postoperative restoration of olfaction.

[Testing the sense of smell using validated procedures]. / Die Prüfung des Riechvermögens mit validierten Verfahren.

There is a growing interest into the investigation of smell disorders in both research and clinical practice. For psychophysical ("subjective") investigations related to the sense of smell a variety of test kits are available, namely the various "Sniffin' Sticks" kits, the UPSIT (University of Pennsylvania Smell Identification Test) or the CCSIT (Cross-Cultural Smell Identification Test). Recording of olfactory evoked potentials (OEPs) and respiration olfactometry can be used for diagnosing smell dysfunctions in a more objective way.