Multicenter investigation of 1,036 subjects using a standardized method for the assessment of olfactory function combining tests of odor identification, odor discrimination, and olfactory thresholds

The influence of stimulus duration on odor perception

Although different parameters are known to alter the shape of olfactory event related potentials (ERP), ERP parameters are generally thought to be independent from stimulus duration. Evidence from recent studies investigating trigeminal ERP indicates that this may not be true. Aim of the present study was to investigate the relationship of stimulus duration and ERP. A total of 20 young healthy subjects participated. Subjects were investigated on 5 occasions on 5 different days. ERP were recorded to olfactory stimuli of two different concentrations and 3 different durations (100 ms, 200 ms, 300 ms). In two sessions olfactory ERP to PEA were recorded, in another two sessions H2S was applied. During the same sessions, intensity ratings were recorded. In the fifth session, subjects were asked to rate the duration of H2S stimuli and PEA stimuli. Whereas at weak stimulus concentrations no effect of stimulus duration could be observed, there was a clear effect of "duration" in ERP amplitudes following stimuli with higher concentrations: the longer the stimulus duration the larger the ERP amplitudes. No effect was found on ERP latencies. With regard to intensity ratings, strong stimuli and longer lasting stimuli lead to higher ratings. Similarly, ratings of stimulus duration were dependent from stimulus concentration and stimulus duration. Results of the present study showed that similar to trigeminal ERP, information about stimulus duration is encoded in olfactory ERP, mainly in amplitudes.

Chemosensory specific reduction of trigeminal sensitivity in subjects with olfactory dysfunction

Humans with olfactory loss have been found to exhibit a decreased sensitivity of the chemosensory trigeminal system. It is not clear, whether the reduced trigeminal sensitivity is restricted to the chemosensitive properties of the trigeminal nerve, or whether it reflects a general decrease of trigeminal sensitivity which is also found for cutaneous afferents. To investigate the relationship between cutaneous somatosensory and intranasal chemosensory trigeminal sensitivity, 91 subjects were investigated. Forty-five of them were considered healthy controls, whereas 46 subjects had olfactory dysfunction. Subjects with olfactory dysfunction were found to have higher thresholds for CO2 than controls indicating lower trigeminal chemosensory sensitivity in subjects with olfactory dysfunction. Both etiology and degree of olfactory dysfunction appeared to have an impact on CO2 thresholds. In contrast, no such differences were found with regard to detection thresholds for electrical cutaneous stimulation. These results indicate that the decrease of trigeminal sensitivity in subjects with olfactory dysfunction is specific for chemosensory sensations.

Executive function and memory in relation to olfactory deficits in alcohol-dependent patients

BACKGROUND

Prior research indicates that chronic alcoholism is accompanied by olfactory deficits. These have been suggested to reflect dysfunctions in olfactory brain regions. The present study investigated the role of neurocognitive functioning in tests (executive function and memory) sensitive to the functional integrity of brain areas that are crucial to olfactory processing in patients with alcohol dependence.

METHODS

Performance on olfactory functions (detection threshold, quality discrimination, identification), executive function (Wisconsin Card Sorting Test), and memory (German version of the California Verbal Learning Test) was assessed in 32 alcohol-dependent patients and 30 healthy comparison subjects, comparable in age, gender, and smoking status.

RESULTS

Compared with controls, alcohol-dependent patients were impaired in all 3 domains, olfactory functions, executive function, and memory. In patients, olfactory discrimination ability was positively correlated with executive function performance. Regression analyses conducted to clarify the relation between group (patients vs controls), executive function, memory, and olfactory functions indicated that group was the only significant predictor of olfactory detection threshold and identification, and both group and executive function were found to be the significant predictors of olfactory discrimination.

CONCLUSIONS

Olfactory deficits in alcohol dependence appear to be associated with prefrontal cognitive dysfunction. Results indicate that olfactory quality discrimination deficits are related to executive function impairment. These findings add to the available research on frontal lobe dysfunction in alcoholism, suggesting that alcohol-related olfactory discrimination deficits may be associated with impairment in the functional integrity of the prefrontal lobe.

A study on the prognostic significance of qualitative olfactory dysfunction

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

Normative data for the “Sniffin’ Sticks” including tests of odor identification, odor discrimination, and olfactory thresholds: an upgrade based on a group of more than 3,000 subjects

"Sniffin' Sticks" is a test of nasal chemosensory function that is based on pen-like odor dispensing devices, introduced some 10 years ago by Kobal and co-workers. It consists of tests for odor threshold, discrimination, and identification. Previous work established its test-retest reliability and validity. Results of the test are presented as "TDI score", the sum of results obtained for threshold, discrimination, and identification measures. While normative data have been established they are based on a relatively small number of subjects, especially with regard to subjects older than 55 years where data from only 30 healthy subjects have been used. The present study aimed to remedy this situation. Now data are available from 3,282 subjects as compared to data from 738 subjects published previously. Disregarding sex-related differences, the TDI score at the tenth percentile was 24.9 in subjects younger than 15 years, 30.3 for ages from 16 to 35 years, 27.3 for ages from 36 to 55 years, and 19.6 for subjects older than 55 years. Because the tenth percentile has been defined to separate hyposmia from normosmia, these data can be used as a guide to estimate individual olfactory ability in relation to subject's age. Absolute hyposmia was defined as the tenth percentile score of 16-35 year old subjects. Other than previous reports the present norms are also sex-differentiated with women outperforming men in the three olfactory tests. Further, the present data suggest specific changes of individual olfactory functions in relation to age, with odor thresholds declining most dramatically compared to odor discrimination and odor identification.

Loss of trigeminal sensitivity reduces olfactory function

The trigeminal and olfactory nerves share overlapping innervation areas in the nasal cavity and seem to work in an interactive way. Loss of olfactory function leads to a decreased trigeminal sensitivity, as shown in anosmic subjects. To report the impact of disturbed trigeminal sensitivity on the olfactory function, we present a patient with unilateral loss of trigeminal function resulting from a meningeoma. Thresholds to a selective olfactory stimulus were elevated by a factor of 64 on the affected side. Recordings of event-related potentials in response to olfactory stimuli showed a significantly reduced response on the affected side. This report indicates that loss of trigeminal function may affect the sense of smell.

Investigations in subjects with cough following upper respiratory tract infection

The study aimed to investigate subjects with cough following acute upper respiratory tract infection (URTI), and to compare those subjects unable to suppress cough ("non-suppressors") with those who were able to suppress cough ("suppressors"). Forty-three URTI subjects participated, 31 with cough associated with acute URTI and 12 healthy controls; 21 of the coughing subjects were "suppressors", 10 were "non-suppressors". We obtained responses to chemical and mechanical stimulation of the nasal cavity or the pharynx using both psychophysical measures and event-related potentials. The study provided the following results: (1) "non-suppressors" did not exhibit significantly different intensity ratings or event-related potentials in comparison to "suppressors" in terms of responses to intranasal irritant, mechanical, or olfactory stimuli; (2) when pharyngeal mechanical stimuli were investigated "suppressors" rated the stimuli as more intense than "non-suppressors" and controls; (3) latencies of event-related potentials to pharyngeal stimuli were longest in "non-suppressors". Keeping in mind the relatively small sample size, it appears possible to differentiate certain types of cough during uncomplicated URTI. This may help to explain interindividual differences in responsiveness to cough medication.

Olfactory Ability in the Healthy Population: Reassessing Presbyosmia

Age-associated loss of olfactory function, or presbyosmia, has been described in many studies of olfactory ability. Presbyosmia has been ascribed to idiopathic causes despite recognition that many neurodegenerative diseases also induce loss of olfactory function and increase in incidence in the aged population. Often this olfactory loss is unnoticed or unreported by affected individuals. More effective olfactory function in women compared with men is another common feature of many studies of olfactory function. Here we report on normative data from an Australian population study (n = 942) that has been divided into 2 subpopulations and reassessed as (included) a population of healthy, nonmedicated, nonsmokers with no history of nasal problems (n = 485) and (excluded) a population of participants who were either medicated, smokers or had a history of nasal problems (n = 457). The "included" data set shows a strong relationship between self-reporting of olfactory sensitivity and olfactory function score. The included data set shows a small but significant decline in olfactory ability after 65 years of age and better olfactory function in females compared with males. Data from the excluded population show a marked decline in olfactory ability after 65 years of age, no difference between males and females, and a weak relationship between self-reporting of olfactory function and actual olfactory function. The power of this approach is that it provides a normative data set against which many factors such as medication schedules and pathological conditions can be compared.

Chemosensory event-related potentials in relation to side of stimulation, age, sex, and stimulus concentration

OBJECTIVE

For chemosensory event-related potentials (ERP) significant effects of age and sex have been demonstrated. The aim of the present study was to assess the effects of stimulus concentration, side of stimulation, and sex on the topographical distribution of chemosensory ERP in a large group of subjects stratified for different age groups. In addition, psychophysical measures of both olfactory and trigeminal function should be assessed in greater detail compared to previous work.

METHODS

A total of 95 healthy subjects participated in the study. Olfactory functions were tested using the 'Sniffin' Sticks' comprising tests of odor identification, odor discrimination, and odor threshold. Trigeminal sensitivity was assessed on a psychophysical level using a lateralization paradigm. ERP to the olfactory stimulant H2S and the trigeminal irritant CO2 were recorded; stimuli were presented in different concentrations to the left and right nostril.

RESULTS

Olfactory thresholds exhibited an age-related increase while the outcome of psychophysical trigeminal tests was not significantly affected by age. In contrast, there was no significant main effect of the factor 'sex' for olfactory tests, while women scored higher than men in the trigeminal task. ERP to olfactory and trigeminal stimuli exhibited a relationship to stimulus concentration, age, and sex with youngest women showing largest amplitudes and shortest latencies. There was no significant main effect of left- or right-sided stimulation on ERP. Measures of olfactory function were found to correlate with parameters of olfactory ERP even when controlling for the subject's age. In addition, correlations between scores in the lateralization task and parameters of the trigeminal ERP were found.

CONCLUSIONS

Based on electrophysiological data obtained in a large sample size the present results established an age-related loss of olfactory and trigeminal function, which appears to be almost linear. Further, the present results emphasize that responses to chemosensory stimuli are related to sex, while the side of stimulation does not play a major role in the presently used paradigm. Finally, these data establish the lateralization paradigm as a psychophysical tool to investigate intranasal trigeminal function.

SIGNIFICANCE

The present results obtained in a representative group of healthy subjects establishes a comprehensive set of data, which will serve as reference for future work in this area of research.

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.

Transient hemiageusia in cerebrovascular lateral pontine lesions

Knowledge of human central taste pathways is largely based on textbook (anatomical dissections) and animal (electrophysiology in vivo) data. It is only recently that further functional insight into human central gustatory pathways has been achieved. Magnetic resonance imaging studies, especially selective imaging of vascular, tumoral, or inflammatory lesions in humans has made this possible. However, some questions remain, particularly regarding the exact crossing site of human gustatory afferences. We present a patient with a pontine stroke after a vertebral artery thrombosis. The patient had infarctions in areas supplied by the anterior inferior cerebellar artery and showed vertical diplopia, right sided deafness, right facial palsy, and transient hemiageusia. A review of the sparse literature of central taste disorders and food preference changes after strokes with a focus on hemiageusia cases is provided. This case offers new evidence suggesting that the central gustatory pathway in humans runs ipsilaterally within the pons and crosses at a higher, probably midbrain level. In patients with central lesions, little attention has been given to taste disorders. They may often go unnoticed by the physician and/or the patient. Central lesions involving taste pathways seem to generate perceptions of quantitative taste disorders (hemiageusia or hypogeusia), in contrast to peripheral gustatory lesions that are hardly recognised as quantitative but sometimes as qualitative (dysgeusia) taste disorders by patients.

A double-blind, randomized, placebo-controlled trial of macrolide in the treatment of chronic rhinosinusitis

OBJECTIVES

The antiinflammatory effect of macrolide antibiotics has been well-established, as has their role in the treatment of certain disorders of chronic airway inflammation. Several studies have suggested that long-term, low-dose macrolides may be efficacious in the treatment of chronic rhinosinusitis; however, these studies have lacked a control group. To date, this effect has not been tested in a randomized, placebo-controlled study.

METHOD

The authors conducted a double-blind, randomized, placebo-controlled clinical trial on 64 patients with chronic rhinosinusitis. Subjects received either 150 mg roxithromycin daily for 3 months or placebo. Outcome measures included the Sinonasal Outcome Test-20 (SNOT-20), measurements of peak nasal inspiratory flow, saccharine transit time, olfactory function, nasal endoscopic scoring, and nasal lavage assays for interleukin-8, fucose, and a2-macroglobulin.

RESULTS

There were statistically significant improvements in SNOT-20 score, nasal endoscopy, saccharine transit time, and IL-8 levels in lavage fluid (P<.05) in the macrolide group. A correlation was noted between improved outcome measures and low IgE levels. No significant improvements were noted for olfactory function, peak nasal inspiratory flow, or lavage levels for fucose and a2-macroglobulin. No improvement in any outcome was noted in the placebo-treated patients.

CONCLUSION

These findings suggest that macrolides may have a beneficial role in the treatment of chronic rhinosinusitis, particularly in patients with low levels of IgE, and supports the in vitro evidence of their antiinflammatory activity. Additional studies are required to assess their place in clinical practice.

Extrapyramidal symptoms in Wilson's disease are associated with olfactory dysfunction

Wilson's disease is a rare autosomal recessive disorder characterized by the accumulation of copper, mainly in the liver and the brain. As copper accumulation in the brain leads to disturbances in basal ganglia function, neurological-type patients typically present with hypo- and hyperkinetic extrapyramidal symptoms, with Parkinsonism being very common. Although there are numerous reports on olfactory deficits in primary neurodegenerative disorders, olfactory function has not been investigated in metabolic disorders presenting with extrapyramidal features. Twenty-four patients with Wilson's disease participated in the investigation. All patients were treated pharmacologically. They comprised patients with liver disease alone (including mild enzyme elevation in asymptomatic individuals; n = 11) and/or neurological symptoms (n = 13) at the time of testing. Twenty-one patients underwent both [18F]fluoro-2-deoxy-D-glucose positron emission tomography ([18F]FDG-PET) and magnetic resonance imaging (MRI). The severity of extrapyramidal symptoms was judged using a clinical score system ranging from 0 (no symptoms) to 3 (severe symptoms). In all patients, psychophysical testing was performed using the Sniffin' Sticks, which involved tests for odor threshold, discrimination, and identification. Results from the present study revealed that Wilson's disease patients with neurological symptoms show a significant olfactory dysfunction compared to hepatic-type patients. Individuals who are more severely neurologically affected also present with a more pronounced olfactory deficit. Of interest, there was no significant effect of long-term treatment with penicillamine on olfactory function. Olfactory function did not correlate significantly with the presence of MRI visible lesions in the basal ganglia or with any regional glucose metabolism as measured by [18]F-FDG-PET. In conclusion, these findings indicate that the underlying pathological alterations with degeneration in the basal ganglia and neuronal loss in association with a marked increase of the copper content in this brain region play a role in the olfactory deficit.

Euosmia: a rare form of parosmia

The nature of qualitative olfactory disorders such as phantosmia and parosmia is a matter of debate. Parosmia and phantosmia mainly occur in combination with post-traumatic or post-infectious olfactory loss. Rare causes of these disorders such as brain tumors, side-effects of drugs, paraneoplastic syndromes, psychiatric disorders or intracerebral haemorrhage have been reported. Parosmias are distorted sensations of smell elicited by an odor, whereas phantosmias persist permanently or occur without the presence of an odor source. Phantosmias differ widely in terms of their nature. In contrast, parosmias always seem to be unpleasant. We report the case of a female with post-infectious hyposmia who reported a pleasant parosmia to selected odorants. We have called this rare clinical presentation euosmia.

A preliminary study of neuroSPECT evaluation of patients with post-traumatic smell impairment

BACKGROUND

Most olfactory testings are subjective and since they depend upon the patients' response, they are prone to false positive results. The aim of this study was to use quantitative brain perfusion SPECT in order to detect possible areas of brain activation in response to odorant stimulation in patients with post-traumatic impaired smell in comparison to a group of normal subjects.

METHODS

Fourteen patients with post-traumatic impaired smell and ten healthy controls were entered in this prospective study. All subjects underwent brain SPECT after intravenous injection of 740-MBq 99mTc-ECD and 48 hours later, the same procedure was repeated following olfactory stimulus (vanilla powder).

RESULTS

In most of seven regions of interest (Orbital Frontal Cortex, Inferior Frontal Pole, Superior Frontal Pole, Posterior Superior Frontal Lobe, Parasagittal Area, Occipital Pole, and Cerebellar area) the post-stimulation quantitative values show increased cortical perfusion being more pronounced in normal volunteers than the anosmic patients (except cerebellar areas and the right occipital pole). Maximal activation was observed in orbitofrontal regions (right+ 25.45% and left +25.47%).

CONCLUSION

Brain SPECT is a valuable imaging technique in the assessment of post-traumatic anosmia and could be competitive as an alternative to other imaging techniques, especially when functional MRI is unavailable or unsuitable. However, this procedure may benefit from complementary MRI or CT anatomical imaging.

Mechanical obstruction of the olfactory cleft reveals differences between orthonasal and retronasal olfactory functions

Following up on recent observations in patients with nasal polyposis (NP), the present study aimed to investigate whether a mechanical obstruction of the anterior olfactory cleft (OC) would produce differential effects on orthonasal and retronasal olfactory functions. To this end, we studied 33 healthy subjects in a randomized trial. Sponges with high content of saline were either placed in the OC or on the respiratory epithelium, such that this was blinded to both subject and observer. The results indicated that orthonasal (P = 0.04) but not retronasal (P = 0.15) olfactory identification ability was lower when the OC was blocked. This confirms the idea that differences between orthonasal and retronasal olfactory functions, as observed in NP patients, are, at least to some degree, due to mechanical obstruction of the anterior portion of the OC. The present data also suggest that mechanical obstruction is a means to induce reversible hyposmia void of side effects which can be performed in a blinded fashion. This might become a valuable model of hyposmia for future investigations.

[Olfactory dysfunction due to nasal sinus disease. Causes, consequences, epidemiology, and therapy]

Olfaction not only contributes to our quality of life but, among other functions, it is also necessary for identifying potential dangers, e.g., fire or spoilt food. In general the value of olfaction is only recognized when the sense of smell is impaired or lost. Olfactory dysfunction is diagnosed according to its cause (e.g., sinonasal, post-traumatic, post-upper respiratory tract infection, neurodegenerative, and idiopathic). At present little is known about prognostic factors for predicting resolution of olfactory loss on an individual basis. In cases of impaired olfaction due to sinonasal disease, both conservative and operative treatments have been established. Corticoids are used both topically and systemically. In cases of severe mechanical obstructions or advanced stages of nasal polyposis, FESS (functional endoscopic sinus surgery) seems to be the state of the art.

Effects of radiotherapy on olfactory function

BACKGROUND AND PURPOSE

Changes in olfactory function have been reported in patients receiving significant doses of radiation to the olfactory epithelium. Aim of this study was to investigate severity and time course of changes in olfactory function in patients irradiated for tumours of the head and neck region.

MATERIAL AND METHODS

Forty-four patients receiving radiotherapy (RT) for tumours in the area of the head and neck participated (16 women, 28 men; age 11-81 y; mean 55 y). Olfactory function was measured before and bi-weekly during RT for 6 weeks. A subgroup (25 patients) was followed for 12 months. Patients were divided into two groups according to the dose to the olfactory epithelium. Twenty-two patients ('OLF group') had radiation doses to the olfactory epithelium between 23.7 and 79.5 Gy (median 62.2 Gy). In the 22 patients of the 'non-OLF group' the dose applied to the olfactory epithelium was significantly lower (2.9-11.1 Gy, median 5.9 Gy). Total tumour dose (30-76.8 Gy), age, sex distribution, and baseline chemosensory function were not significantly different between groups. Testing was performed for odour identification, odour discrimination, and olfactory thresholds.

RESULTS

Odour discrimination, but not odour identification or odour threshold, was significantly decreased 2-6 weeks after begin of therapy in the OLF group. In addition, a significant effect of the radiation dose was observed for odour discrimination. More than 6 months after therapy, OLF group patients had significantly lower odour identification scores compared to the non-OLF group.

CONCLUSION

As indicated through the non-significant change of olfactory thresholds, the olfactory epithelium is relatively resistant against effects of radiation. It is hypothesized that RT has additional effects on the olfactory bulb/orbitofrontal cortex responsible for the observed changes of suprathreshold olfactory function.

[Studies of the olfactory epithelium in anosmic patients after head trauma]

BACKGROUND

An additional diagnostic option for olfactory dysfunction is the study of the olfactory epithelium.

METHODS

Biopsies of the olfactory epithelium were performed under local anaesthesia on five patients with a history of head trauma with anosmic results in the Sniffin' Sticks test. The biopsy of a normosmic patient served as a control. Immunochemistry of frozen sections and explant culture studies were made, investigating ability to attach to the culture plate and the outgrowth of neuronal cells after growth-factor stimulation.

RESULTS

The biopsies were carried out without any complications. All biopsies were positive for neurofilament, a marker for immature neurons. Substantial differences in the explants' ability to attach to the culture plate occurred, with a rate of between 25% and 100%. The control showed 67%. After stimulation with growth factors (FGF(2)), the cultures with more attached cells showed neuronal differentiation with the appearance of bipolar cells.

CONCLUSIONS

The biopsy of the human olfactory epithelium is a minimally invasive procedure which can provide further information on specific changes and possible regenerative ability. Further studies with larger numbers of patients with different causes of an impaired sense of smell are needed to determine specific changes.

Gustatory stimulation influences the processing of intranasal stimuli

OBJECTIVES

Taste and smell interact. The aim of this study was to examine this interaction using gustatory and olfactory stimuli applied at the same time, which exhibited perceptual compatibility and incompatibility.

METHODS

Thirty-two, young, healthy normosmic subjects (16 men, 16 women) took part in two randomized sessions. Event-related potentials (ERP) were recorded in response to vanillin, or gaseous CO2. These two conditions were combined with three "taste conditions" including sweet taste, sour taste, and the intraoral presentation of an empty taste dispenser.

RESULTS

Vanillin responses were largest for the "sweet" condition, while they were smaller for the "sour condition". In contrast, responses to CO2 were largest under the "sour" condition, and smallest under the "sweet" condition. Moreover, during the "sweet" condition the latencies of P1 and N1 were shorter than in the "sour" condition, which was the other way around for CO2.

CONCLUSIONS

Results of the present investigation suggested that (1) the early processing of intranasal chemosensory stimuli is modulated through concomitant gustatory stimulation, and that (2) this modulation may depend, at least in part, on the contextual compatibility between intranasal and intraoral stimuli.

Sex differentiated responses to intranasal trigeminal stimuli

The aim of the study was to address sex-related hemispheric differences in trigeminal event-related potentials while controlling for the subjects' olfactory sensitivity. Event-related potentials to lateralized stimulation using the trigeminal stimulant CO(2) were recorded in 28 healthy young subjects (16 women). There was no sex-related difference in olfactory sensitivity. Results indicated a sex-differentiated response to trigeminally induced pain. Women were found to have generally higher amplitudes and shorter latencies of the late positive component than men. Moreover, men and women exhibited different hemispheric activations in that women expressed shorter latencies over the left hemisphere than men. The pronounced sex-related difference of the late positive component suggests a cognitive/emotional impact on the processing of intranasal pain as indicated by others.

Taste Disorders in Acute Stroke

Background and Purpose— The aim of the study was to assess whether and how frequently patients with acute first-ever stroke exhibit gustatory dysfunction.

Methods— We performed a 1-year prospective observational study. Gustatory function was assessed using the standardized “taste strips” test. In addition, we assessed olfactory function, swallowing, stroke location, comorbidities, and the patients’ medication.

Results— A total of 102 consecutive patients were enrolled (45 female, 57 male; mean age, 63 years); 31 of them (30%) exhibited gustatory loss and 7 (6%) had lateralized impairment of taste function. Predictors of impaired taste function were male gender ( P =0.003), high National Institutes of Health Stroke Scale (NIHSS) score at admission ( P =0.009), coexisting swallowing dysfunction ( P =0.026), and a stroke of partial anterior circulation subtype (PACS) ( P =0.008). In particular, in hypogeusic patients the lesion was most frequently localized in the frontal lobe ( P =0.009). Follow-up examinations in 14 patients indicated improvement of taste sensitivity.

Conclusion— Taste disorders after stroke are frequent. A significant association was found for male gender, high NIHSS score, swallowing disorder, and PACS, particularly in the frontal lobe. Generally, taste disorders after stroke seem to have a good prognosis.

Comparison of diagnostic findings using different olfactory test methods

OBJECTIVE

To quantify discrepancies in the diagnosis of olfactory function that might exist when comparing results obtained from centers using different methods of olfactory testing.

STUDY DESIGN

Prospective study of 50 healthy adult volunteers and 25 adult patients with olfactory complaints.

METHODS

Two test methods, the Connecticut Chemosensory Clinical Research Center (CCCRC) test widely used in the United States, and the Jet Stream Olfactometer (JSO) test used in Japan, were used to measure and categorize the diagnostic level of olfactory function (normosmia, mild hyposmia, moderate hyposmia, severe hyposmia, anosmia). Olfactory function was measured separately for each nostril.

RESULTS

There was a significant correlation (rs = 0.788, P < .01, n = 150 nostrils) between diagnostic categories assigned by the CCCRC and JSO test methods. Diagnostic categories were identical for 66.7% of the nostrils tested, and in only 7.3% of the cases did the results differ by more than one category. For the anosmic and normosmic categories, test results were in agreement 91.7% of the time, whereas for the hyposmic categories (mild, moderate, and severe) results were in agreement only 22.2% of the time.

CONCLUSIONS

Our results demonstrate that when comparing clinical or research data obtained from centers using different olfactory test methods, subjects with diagnoses of anosmia or normosmia may be more reliably compared than those with different levels of hyposmia.

Reduced olfactory bulb volume in post-traumatic and post-infectious olfactory dysfunction

The olfactory bulb is a highly plastic structure the volume of which partly reflects the degree of afferent neural activity. In this study, 22 patients with post-infectious olfactory deficit, nine participants with post-traumatic olfactory deficit, and 17 healthy controls underwent magnetic resonance volumetry of the olfactory bulb. Patients presented with significantly smaller olfactory bulb volumes than controls; significant correlations between olfactory function and bulb volume were observed. Patients with parosmia exhibited smaller olfactory bulb volumes than those without parosmia. Findings indicate that smell deficits leading to a reduced sensory input to the olfactory bulb result in structural changes at the level of the bulb. Reduced olfactory bulb volumes may also be considered to be characteristic of parosmia.

Intranasal trigeminal thresholds in healthy subjects

The trigeminal chemosensory system responds to irritation of the nasal cavity. Despite its dominant role as a sentinel in protecting the respiratory tract from harmful substances and its involvement in the perception of odorous substances, it has received relatively little attention compared to the olfactory system. Aim of the present study was the comparison of two psychophysical techniques to assess intranasal trigeminal thresholds, namely (A) responses of subjects who focused on intranasal trigeminally mediated sensations, and (B) the ability of subjects to identify the side of the nose receiving unilaterally presented stimuli. Method A (0.81>r>0.56) was found to show a higher test-retest reliability than Method B (0.48>r>0.40). Method A revealed thresholds that were approximately 32 times lower than those measured with method B. With method A women were found to have lower thresholds than men; no such difference could be detected between older and younger subjects. In conclusion, if the objective is to assess the level at which trigeminal sensations are detected with the utmost objectivity and unconfounded by smell, the obvious choice is B. If one's purpose is to assess the level at which trigeminal sensations are detected and the quality perceived, in the context of an odor one might opt for Method A. Thus, preference of one method over the other may depend on the question being asked, provided a well-instructed/trained panel of subjects is used.

Olfactory functions and volumetric measures of orbitofrontal and limbic regions in schizophrenia

OBJECTIVE

Olfactory deficits in schizophrenia patients have been suggested to reflect medial temporal and/or prefrontal brain abnormalities. In this study, we examined the relationship between different olfactory functions and volumes of the hippocampus-amygdala complex (HAC) and the orbitofrontal brain region using magnetic resonance imaging (MRI).

METHODS

Thirty-three young men with schizophrenia (DSM-IV) and 40 healthy controls performed unirhinal olfactory assessment including the main olfactory functions (threshold, discrimination, and identification), and odor judgements (intensity, edibility, familiarity, and pleasantness). Volumes of regions in the medial temporal lobe (hippocampus and amygdala) and the prefrontal region (orbitofrontal gray and white matter) were measured on MRI scans.

RESULTS

Compared with controls, patients showed bilaterally impaired thresholds, quality discrimination and identification, as well as edibility judgements. Olfactory deficits were not attributable to smoking, premorbid intelligence, or impaired thresholds. Relative to controls, patients had bilateral reduced hippocampus and amygdala volumes. In patients, smaller hippocampus volumes were associated with poorer olfactory discrimination ability.

CONCLUSIONS

Olfactory deficits in schizophrenia appear to be associated with morphometric abnormalities in the medial temporal rather than the orbitofrontal region (OFR). These results indicate that olfactory quality discrimination deficits are related to structural hippocampus abnormalities. Future studies of genetic and behavioral high-risk samples seem warranted.

Androstadienone odor thresholds in adolescents

A sex-related difference in olfactory sensitivity to androstenone has been reported to occur during adolescence. More males than females exhibited anosmia to androstenone, or an increase in androstenone threshold with age. The current study addressed the question whether similar, sexually dimorphic effects of aging over puberty can also be found for androstadienone. A total of 102 subjects participated (36 females, 66 males). Similar to previous investigations, subjects were divided into a group of 47 individuals with a mean age of 13.3 years, defined as pre/peri-pubertal, and a group of 55 subjects with a mean age of 17.1 years, defined as post-pubertal. All subjects underwent tests for verbal abilities, general olfactory function, and measurements of androstadienone thresholds. The study provided the following major results: (1) Male subjects exhibited higher androstadienone sensitivity in the pre/peri-pubertal group as compared to the post-pubertal group. This difference was not observed in female subjects. Correspondingly, a negative correlation between age and androstadienone sensitivity was found for male subjects, but not for female subjects. (2) In contrast to this sex-specific change of the androstadienone odor threshold, verbal skills and odor identification abilities increased with age in all subjects regardless of their sex. In conclusion, the present observations confirm previous research on sex-differentiated effects of aging during puberty on sensitivity towards odorous steroids. While the underlying causes are unknown, it may be hypothesized that the decreased sensitivity could result from the increased endogenous levels of androstadienone in male subjects. Future studies should include both steroid and non-steroid odorants to further explore these age-related changes.

Olfactory bulb volumes in patients with idiopathic Parkinson's disease a pilot study

Olfactory loss is among early signs of idiopathic Parkinson's disease (IPD). The present pilot study aimed to investigate whether this loss would be reflected in a decreased volume of the olfactory bulb (OB) established through magnetic resonance imaging. Eleven consecutive IPD patients were compared to 9 healthy, age-matched controls. Results indicated that there is little or no difference between IPD patients and healthy controls in terms of OB volume. Based upon the relation between loss of olfactory input to the olfactory bulb and consecutive decrease in volume, these data support the idea that olfactory loss in IPD is not a primary consequence of damage to the olfactory epithelium but rather results from central-nervous changes.

Detection of presymptomatic Parkinson's disease: combining smell tests, transcranial sonography, and SPECT

Olfactory loss is among the early signs of Parkinson's disease (PD). We investigated whether "idiopathic" olfactory dysfunction might relate to signs of nigral degeneration. Olfactory tests were combined with transcranial sonography of the substantia nigra and single photon emission computed tomography (SPECT) imaging. Thirty patients diagnosed with idiopathic olfactory loss participated. Eleven of these patients exhibited an increased echogenicity of the SN in the transcranial sonography. In 10 of these 11 patients, SPECT scans with (123)I-FP-CIT were performed. Median uptake ratios in the basal ganglia were pathological in 5 patients, 2 patients exhibited borderline findings, and 3 patients had normal results. Considering patients with idiopathic olfactory dysfunction, noninvasive transcranial sonography seems to be helpful in identifying patients potentially at risk to develop PD. Longitudinal follow-up studies are necessary to estimate the ratio of patients with dopaminergic cell loss in the basal ganglia who will develop PD in the future.

Olfactory deficits in anorexia nervosa

OBJECTIVE

Young patients admitted to the hospital due to anorexia nervosa report reduced pleasure and impaired perception of smell while eating. So far, two studies on odour identification ability in eating disorders did not suggest any significant deficits. Therefore a new and more detailed method of olfactory testing may be needed, in order to determine the subjective impairment of olfaction.

METHOD

By using all three subtests of the recently developed smell test called "Sniffin'Sticks", the olfactory deficits were assessed in more detail and the results of female anorectic patients (n = 17) were compared with those of healthy females (n = 15).

RESULTS

By examining the anorectic patients no deficits in the subtest odour identification were found. On the contrary, in the subtests odour discrimination and odour threshold deficits of the anorectic patients were detected.

CONCLUSION

Reduced olfactory perception might be considered as a common deficit in anorexia nervosa with possible influences and consequences for therapy.

Basic and clinical aspects of olfaction

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

A study on the frequency of olfactory dysfunction

OBJECTIVES/HYPOTHESIS

Goals of the study were to evaluate the frequency of olfactory dysfunction in a large representative population without sinonasal complaints and to investigate the extent to which general pathological conditions, medications, and aging influence olfaction.

STUDY DESIGN

Prospective.

METHODS

Results based on an odor identification test ("Sniffin' Sticks") were reported from 1240 subjects. The subjects presented themselves to an otorhinolaryngology outpatient clinic with relatively mild and transitory complaints unrelated to the upper airways. A detailed otorhinolaryngological examination in combination with a standardized interview further ascertained that these patients had no rhinological problems or symptoms relating to sinonasal disease.

RESULTS

Apart from the confirmation of the effects of age, gender, and certain otorhinolaryngological diseases on the sense of smell, the study results revealed that certain general diseases (liver diseases, nonotolaryngological cancers) appear to influence olfactory function, whereas other diseases or disorders have little or no impact on olfaction (hypertension, cardiovascular problems).

CONCLUSION

The data in the study revealed that olfactory dysfunction among subjects under 65 years of age is more frequent than previously reported.

Correspondence between three olfactory tests and suprathreshold odor intensity ratings

OBJECTIVES

The capability of three olfactory tests (European Test of Olfactory Capabilities, Sniffin' Sticks and Cross-Cultural Smell Identification Test) to similarly classify subjects as normosmics, hyposmics and anosmics as well as the relation between test performance and suprathreshold ortho- and retronasal odor intensity ratings were examined.

MATERIAL AND METHODS

A total of 48 subjects (age range 15-84 years; mean age 49.5 years) completed the 3 olfactory tests, rated aqueous solutions of vanilla (0-0.31%) and lemon aroma (0-0.17%) for odor and flavor intensity and filled in a background questionnaire. Ten subjects had case histories indicating anosmia, with the remainder having subjectively normal olfaction.

RESULTS

The test results were highly correlated and differentiated anosmic, hyposmic and normosmic subjects. At an individual level, some discrepancy was seen in the olfactory diagnoses given by the three tests. In principal component analysis, olfactory measurements were loaded on three components: (i) odor detection, discrimination and identification; (ii) suprathreshold intensity ratings; and (iii) threshold for n-butanol. Advanced age was related to impaired olfactory performance.

CONCLUSIONS

Although the three olfactory tests diagnosed the individuals slightly differently, all were considered to be valid for clinical evaluation of olfactory capabilities. The tests separated anosmics and normosmics highly significantly, and permitted an assessment of hyposmia. The suprathreshold odor intensity ratings reflected a different dimension of olfaction than the three olfactory tests.

Australian norms for a quantitative olfactory function test

Quantitative olfactory assessment is often neglected in clinical practice, although olfactory loss can assist diagnosis and leads to significant morbidity. The aim of this study was to develop normative data for the Australian population for the 'Sniffin' Sticks', an internationally established olfactory function test. As in other populations, Australian females performed better than males and both lost olfactory function with age. From the normative data, criterion test scores for males and females were established for clinical classifications ('normosmic', 'hyposmic', and 'nosmic'). These clinical classifications were assessed in Parkinson's patients: 81.1% were anosmic or severely hyposmic and only 7.7% were normosmic. A new term ('rebyosmia') is introduced to describe age-related loss of olfactory capacity of unknown aetiology. With these norms, the Sniffin' Sticks can be used in the Australian population to compare an individual's olfactory function against the population of others of similar age and sex and to identify olfactory dysfunction.

Olfactory functioning in patients with alcohol dependence: impairments in odor judgements

AIMS

Prior studies indicate that alcohol-dependent patients have impaired olfactory sensitivity, odor quality discrimination and identification ability. However, olfactory functioning with regard to the immediate, perception driven odor associations is unknown. Therefore, this study assessed olfactory judgements in nonamnesic and nondemented patients with alcohol dependence.

METHODS

Thirty alcohol-dependent patients and 30 healthy control subjects, well matched for gender, age and smoking status, and screened for olfactory sensitivity, were asked to rate intensity, familiarity, edibility and pleasantness of 16 odors using visual rating scales.

RESULTS

Compared with controls, patients showed lower scores in odor familiarity and impaired edibility judgements. These impairments were observed bilaterally, were present independently of age, gender, general mental abilities and length of abstinence, and not attributable to smoking or impaired olfactory sensitivity. No differences between groups were found in odor intensity and pleasantness judgements.

CONCLUSION

These results extend prior findings of alcohol-related olfactory deficits, indicating impairments in olfactory processes of odor familiarity and edibility in alcohol-dependent patients. Although the basis of these deficits is still unknown, our finding of a distinct pattern of olfactory functional impairment and sparing (intensity, pleasantness) [corrected] suggests that there is no generalized [corrected] olfactory dysfunction, but [corrected] neural olfactory networks may be affected differently. However, alcoholism appears to be associated with a variety of disturbances in olfactory processing [corrected]

A new method for comparing orthonasal and retronasal olfaction

Odors seem to be perceived differently when presented ortho- or retronasally. In this study, stimuli of controlled concentration and duration were applied in either the anterior nasal cavity or epipharynx by means of air-dilution olfactometry. Stimulus concentration was monitored in the olfactory cleft. In Experiment 1, odor thresholds to a food (chocolate) and a nonfood (lavender) odor were lower for orthonasal, compared with retronasal, stimulation. In Experiment 2, intensity ratings to suprathreshold odor concentrations were significantly higher for orthonasal than for retronasal stimulation with hydro- hydrogen sulfide, but not phenyl ethyl alcohol. Accordingly, amplitudes and latencies of olfactory event-related gen potentials to retronasal stimuli were found to be smaller and prolonged, respectively. This indicates differential processing of olfactory stimuli presented through the retronasal or orthonasal routes. )

Responsiveness of human nasal mucosa to trigeminal stimuli depends on the site of stimulation

There is evidence that functionally different areas can be distinguished within the nasal mucosa with regard to stimulation site and stimulus properties. The aim of the present study was the comparison of electrophysiological and psychophysical measures obtained in response to mechanical and chemosomatosensory stimulation of two different regions of the nasal mucosa. A total of 40 volunteers participated in this study (age range 21-36 years). Chemosomatosensory event-related potentials (ERPs) were recorded using gaseous CO2 as stimulant, while somatosensory ERPs were recorded in response to intranasal mechanical stimuli (air puffs). Stimuli were released to the anterior portion and to the posterior portion of the nasal cavity. A significant interaction between stimulus properties and site of stimulation could be detected after analysis of ERP parameters and intensity ratings. Thus, the chemosensory stimulus was perceived as stronger in the anterior portion of the nasal cavity whereas this was not the case for mechanosensory stimuli. In addition, mechanosensory stimuli were found to evoke ERPs with shorter latencies. These results underline the idea that the respiratory mucosa should not be seen as a homogeneous tissue. It exhibits varying sensitivities to trigeminal stimulation depending on stimulus quality and site of stimulation. Hence, perception of chemosensory stimuli seems to be most accurate in the anterior portion of the nasal cavity, while sensitivity to mechanical stimuli appears to be highest in the posterior portion. In addition, these differences within the respiratory mucosa may contribute to differences in the perception of orthonasal and retronasal odorous stimulation.

Anesthesia affects olfaction and chemosensory event-related potentials

OBJECTIVE

Olfactory and trigeminal systems interact and contribute to the perception of odorants. This study was aimed at investigating the effect of local anesthesia on olfaction.

METHODS

One percent of tetracaine on a cotton swab was applied intranasally at three different locations in 20 volunteers and 4% of lidocaine was applied to the olfactory cleft in a head-down position. Before and after anesthesia, self-assessment, psychometric testing and olfactory event-related potentials [OERPs, using H(2)S and phenyl ethyl alcohol (PEA)], and chemosomatosensory event-related potentials (CSSERPs, using CO(2)) were examined.

RESULTS

Anesthesia at all four locations significantly lowered the perceived self-assessment of olfaction, while using the cotton swab only anesthesia in the middle meatus elevated threshold (P = 0.020), lowered discrimination (P = 0.015), and prolonged OERP (PEA, P = 0.008; H(2)S, P = 0.016), as well as CSSERPs latencies (CO(2), P = 0.020). However, complete temporary anosmia was only achieved after applying 4% lidocaine into the olfactory cleft.

CONCLUSIONS

Intranasal anesthesia applied with a swab reduced self-assessment of olfaction but was unable to produce anosmia. Psychometric test results were concordant with changes in chemosensory event-related potentials.

SIGNIFICANCE

Temporary anosmia is technically difficult to achieve but could be demonstrated for the first time using local anesthesia. Even though anesthesia influences self-assessment, measurable olfactory function can remain unchanged.

Olfactory dysfunction and daily life

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

[The human vomeronasal organ]

Odors influence human behavior. The perception of so-called pheromones is frequently mentioned in the context of a functional vomeronasal organ. Vomeronasal ducts can be detected in approximately half of the population. Its functionality, still a matter of debate, seems to be unlikely, at least after birth. It is easily conceivable that pheromone-induced changes in behavior are mediated through receptors in the human olfactory epithelium.

Effects of the form of glasses on the perception of wine flavors: a study in untrained subjects

Many wine connoisseur claim that the glass shape has a direct impact on wine aroma. This hypothesis was investigated in healthy volunteers (85 m, 96 f; age 19-73 years); 89 subjects received red wine, 92 subjects white wine. Subjects compared three glasses with a white wine and three glasses with a red. Glasses were of different shape but of the same height and of comparable opening diameter. All glasses had elegant stems; two glasses of 'tulip' and 'beaker'-like shapes were used in sessions with red and white wines. Different bulbous glasses were used in either red or white wine sessions. Subjects were blinded whether they received one or more wines. Intensity, hedonic tone, and quality of the wines were rated repeatedly before and after drinking. Ratings of wine odors from different glasses were influenced by glass shape. Importantly, this appeared not to relate to the esthetic impression the glasses made. Thus, the present data indicate that the shape of glasses seems to influence the perception of wine odors.

Assessment of olfactory function and androstenone odor thresholds in humans with or without functional occlusion of the vomeronasal duct

To obtain information on the possible role of the vomeronasal duct (VND) in odor perception and human pheromone detection, the present study investigated different aspects of olfactory function, including thresholds for androstenone in adults with or without detectable VNDs. The study also examined correlations between detection thresholds of androstenone odor and general olfactory function. Subjects' olfaction was assessed with tests for odor identification, odor discrimination, and phenyl ethyl alcohol odor threshold. Measurements were performed on 1 side only, with and without covering the VND. Subjects with or without detectable VNDs did not differ in olfactory sensitivity or androstenone odor thresholds. A small but significant correlation was found between detection thresholds of androstenone and general olfactory function. Finally, covering of the VND did not affect olfactory function or androstenone sensitivity. Results suggest that the human VND does not play a major role in sensitivity toward odorants or the perception of androstenone.

Riechstörungen

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSION

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

Age-related decline of intranasal trigeminal sensitivity: is it a peripheral event?

Compared to younger subjects, older people have a reduced sensitivity of the intranasal trigeminal system which responds to irritation of the nasal cavity. It is unclear whether the cause of this difference relates to age-dependent changes in the periphery of the system. The aim of the present study was the comparison of intranasal trigeminal thresholds assessed through electrophysiological measurements in eight young (four women, four men; mean age 25 years) and eight older subjects (four women, four men; mean age 62 years). The negative mucosa potential (NMP), a peripheral correlate of trigeminal activation, was recorded from the nasal mucosa in response to stimulation with varying concentrations of the mixed olfactory/trigeminal stimulants menthol and linalool. Thresholds were estimated as the strongest concentration which did not elicit a NMP response. Older subjects were found to have higher thresholds for menthol when compared to younger subjects. Furthermore, an explorative analysis indicated that the increase of response amplitudes to increasing stimulus concentrations was shallower in older subjects. These findings indicate that age related loss of intranasal trigeminal sensitivity seems to take place, at least to some degree, in the periphery of the intranasal trigeminal system.

Circadian rhythm and desensitization in chemosensory event-related potentials in response to odorous and painful stimuli

Olfactory (H2S) and trigeminal (CO2) event-related potentials (ERPs) were studied with respect to circadian rhythm and desensitization. ERPs, perceived odor and pain intensity, oral temperature, blood pressure, heart rate, nasal volume, and sleepiness were assessed four times at 04:00, 08:00, 12:00, 16:00, 20:00, and 24:00 hr in five young men. For each of these 24 sessions per participant, H2S and CO2 were each presented in 15 series of five stimuli with a 5-s ISI within and 30-s ISI between series. ERP amplitudes, but not latencies, followed a circadian rhythm (largest at 16:00 and smallest at 04:00) similar to oral temperature and opposite to sleepiness. Amplitudes decreased (most pronounced at 16:00 and 20:00) and latencies increased with repeated stimulation, suggesting desensitization, in accordance with odor and pain intensity. These findings imply that circadian rhythm and desensitization should be considered in chemosensory ERP studies.

Clinical presentation of qualitative olfactory dysfunction

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