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

Depth of olfactory sulcus and olfactory function

The aim of this study was to identify whether the depth of the olfactory sulcus relates to olfactory function in healthy subjects. Forty-four healthy, male volunteers (age range 22-45 years, mean age 28.3 years) were included in this study. Olfactory function was measured for phenyl ethyl alcohol odor thresholds, odor discrimination, and odor identification. Magnetic resonance imaging of the olfactory sulcus was performed immediately following olfactometry. Based on previous investigations the depth of the olfactory sulcus was measured in the plane of the posterior tangent through the eyeballs. Olfactory function correlated significantly with left-sided depth of the olfactory sulcus (r(44)=0.33, P=0.03); no such correlation was seen for the right side. In addition, olfactory sulcus depth was found to be significantly deeper on the right compared to the left side (t=5.61, P<0.001). The present results suggest that there is small, but significant relation between morphological brain structures and measures of olfactory function. Further, lateralization of olfactory sulcus depth may correlate to functional lateralization in the olfactory system. Thus, it may be carefully speculated that sensory input in the olfactory system results in cortical growth in the area of the olfactory sulcus, at least at some developmental stage.

Effects of olfactory function, age, and gender on trigeminally mediated sensations: a study based on the lateralization of chemosensory stimuli

The present investigation aimed to compare trigeminal nasal function of anosmic and hyposmic patients to healthy controls. Further, we aimed to study effects of age and gender on trigeminally mediated sensations following intranasal chemosensory stimulation. Participants were 35 patients with olfactory dysfunction (n=13: functional anosmia; n=22: hyposmia; age 28-69 years, mean age 56 years). Their results were compared with 17 normosmic subjects (28-82 years, mean 52 years). To analyze effects of age and gender in healthy subjects, an additional 24 healthy subjects were included (19-27 years; mean 24 years). Olfactory function was assessed using the 'Sniffin' Sticks' test kit (butanol odor threshold, odor discrimination, odor identification). The subjects' ability to lateralize odors was investigated for benzaldehyde and eucalyptol. Patients with olfactory dysfunction had lower scores in the lateralization task than controls (P<0.001) indicating decreased trigeminal sensitivity. Among anosmic patients scores were not different in relation to different causes of olfactory dysfunction (P>0.29). There was a weak, but significant, correlation between localization of eucalyptol and duration of olfactory dysfunction (P=0.017). When investigating normosmic subjects only, no gender-related difference was apparent for lateralization scores. However, older subjects had lower scores than younger ones (P<0.01). Results of partial correlational analyses controlling for age suggested a relation between the trigeminal and the olfactory systems. In conclusion, results of the present study indicate that patients with olfactory dysfunction have lower trigeminal sensitivity compared with normosmic controls. This seems to be independent of the cause of olfactory loss. The deficit appears to improve with duration of the olfactory dysfunction, possibly indicating adaptive mechanisms. Further, the data suggest an age-related decrease of intranasal trigeminal sensitivity in healthy subjects. Analyses additionally indicate a correlation between olfactory and trigeminal sensitivity.

Test-retest reliability of chemosensory evoked potentials

This study investigated the test-retest reliability of chemosensory event-related potentials in humans. Olfactory event-related potentials and chemosomatosensory event-related potentials were evaluated in 20 healthy, normosmic subjects. Phenyl ethyl alcohol (PEA, 40% v/v) and H(2)S (4 ppm) served as olfactory stimuli whereas CO(2) (60% v/v) was the chemosomatosensory stimulus. Fifteen stimuli of each compound were applied to each nostril. Identical stimulation sequences were used during three test sessions. Sessions 1 and 2 were separated by a mean of 6.8 days; sessions 2 and 3 by 12.5 days. Electroencephalographic recordings were made from Fz, Cz, Pz, C3, and C4. Amplitudes and latencies of P1, N1, P2, N2, and P3 were measured. Pearson's correlation coefficient was calculated to test the test-retest reliability, and the general linear model examined the differences. Most correlations ranged between 0.4 < r < 0.75. Latencies correlated significantly better (P = 0.008) between sessions than amplitudes, even though with CO(2) stimulus amplitudes correlated significantly better than with PEA (P = 0.006) or H(2)S (P = 0.003). No differences arose between measurements from different nostrils for any stimulus. Chemosensory event-related potentials show good test-retest reliability. Carbon dioxide amplitudes exhibit better signal-to-noise ratios than PEA or H(2)S amplitudes. Chemosensory event-related potentials are a clinically valuable objective and are reproducible.

Reduced olfactory sensitivity, discrimination, and identification in patients with alcohol dependence

BACKGROUND

Various olfactory deficits have been reported in the alcohol-induced amnestic syndrome (Korsakoff's syndrome). Less is known about olfactory functioning in nonamnesic and nondemented alcoholic patients.

METHODS

Olfactory performance of 30 alcohol-dependent patients was assessed unirhinally using the Sniffin' Sticks (threshold, discrimination, identification, composite TDI score) and compared with that of 30 healthy controls, matched for sex, age, and smoking status.

RESULTS

Patients showed significantly reduced olfactory sensitivity (higher threshold), discrimination, and identification compared with controls. No group differences were observed in laterality. Identification and discrimination group differences remained significant after controlling for differences in sensitivity. Olfactory deficits in patients were present independent of age, gender, and duration of abstinence (<3 months) and were not attributable to smoking or general cognitive abilities. More than half of the patients (56.7%) could be classified as hyposmic. Lower overall olfactory functioning (TDI) was associated with longer duration of a regular alcohol intake and higher values of gamma-glutamyltransferase (GGT).

CONCLUSIONS

Olfactory dysfunction is common in nonamnesic and nondemented patients with alcohol dependence. Results suggest a detrimental effect of alcohol on central olfactory processing.

Assessment of the Sniff Magnitude Test as a clinical test of olfactory function

Olfactory threshold and odor identification tasks currently serve as the standard approaches to the clinical assessment of olfactory function. Although these methods can be used effectively with the average patient, they suffer from some limitations when used to evaluate children, people with cognitive impairment, or people from diverse cultural backgrounds. A novel approach to the clinical evaluation of olfactory function, the Sniff Magnitude Test, attempts to minimize the cognitive demands of an olfactory test and thereby overcome some of the limitations of alternative tests. This is achieved by measuring the reflex-like reduction in sniffing that occurs when a malodor is encountered. The reliability and the validity of the Sniff Magnitude Test were assessed by testing people on two occasions using the University of Pennsylvania Smell Identification Test (UPSIT), a butanol threshold task, the Alcohol Sniff Test, and the Sniff Magnitude Test. The test-retest reliability of the Sniff Magnitude Test was r=.80, higher than the butanol thresholds and Alcohol Sniff Test but somewhat lower than the UPSIT. Performance on the Sniff Magnitude Test (the sniff magnitude to a malodor relative to nonodorized air) was correlated between r=-.61 and r=-.66 with the other measures of olfactory function. This range of correlations was comparable to that observed between the butanol threshold, the UPSIT, and the Alcohol Sniff Test. Finally, evidence for the advantages of the Sniff Magnitude Test, as compared to the UPSIT, was provided by a study with young children. It is concluded that the Sniff Magnitude Test has significant potential as a clinical measure of olfactory function, and that further testing and development of this method are warranted.

Event-related potentials to intranasal trigeminal stimuli change in relation to stimulus concentration and stimulus duration

Few data are available on the relation of EEG-derived trigeminal event-related potentials (ERPs) to stimulus duration or stimulus concentration. Thus, the aim of this study was to analyze the relation between ERP components and both stimulus duration and stimulus concentration. Twenty healthy young subjects participated. Trigeminal ERPs were recorded after stimulation with CO(2). Five concentrations (45 to 65% volume per volume CO(2)) and five stimulus durations (100 to 300 msec) were used. Trigeminal ERPs were quantified in terms of amplitudes and latencies of its major peaks N(410) (termed N1) and P(622) (termed P3). The relation between stimulus duration, concentration, and amplitudes or latencies of trigeminal ERP components could be described as a model of power, following the formula p = b + k.I g1.D(g2). A linear relationship was found between stimulus concentration, amplitude N1, and amplitude P3, and between stimulus duration and amplitude P3 respectively. Furthermore, a linear relationship was seen between intensity ratings, and stimulus duration and concentration. These data confirm that the different ERP components encode different stimulus characteristics. Specifically, later components of the trigeminal ERP encode not only stimulus concentration but, other than earlier ERP components, also encode stimulus duration. Thus, they reflect the integration of stimuli over relatively long periods of time.

Olfactory changes at threshold and suprathreshold levels following septoplasty with partial inferior turbinectomy

Partial inferior turbinectomy with septoplasty is routinely carried out for airway obstruction. However, its effects on the sense of smell have not been systematically evaluated. The aim of this prospective study was to evaluate the influence of septoplasty with partial inferior turbinectomy on threshold and suprathreshold olfactory acuity. The subjects were 30 patients undergoing septoplasty including partial inferior turbinectomy. Olfactory function was determined by the "Sniffin' Sticks," which allow the assessment of odor thresholds, odor discrimination, and odor identification. The patients rated both olfactory function and nasal airflow using visual analog scales. Nasal airflow was measured by anterior rhinomanometry. Multivariate analyses of variance for repeated measures were used to analyze the results before and after surgery (mean interval, 9.1 weeks). After operation, 87% of the patients had increased airflow, 80% had improved olfactory function in terms of odor identification, and in 70% odor discrimination was found to be improved - but only 54% had improved olfactory function in terms of odor thresholds. Surgery increased ratings of nasal airflow in 93%, and those of olfactory function in 77% (p < .001). Similarly, bilateral inspiratory nasal flow increased (p < .001) and olfactory function was improved (p < .001) after surgical treatment. However, this increase was most pronounced for suprathreshold tests, while it was moderate for odor thresholds (interaction "surgery" x "olfactory test," p = .001). The present investigation suggests that septoplasty in combination with inferior turbinectomy has a beneficial effect on olfaction, mainly on suprathreshold olfactory functions. This effect may be partly due to interactions between the increased perception of nasal airflow and cognitive factors involved in olfactory sensitivity. According to the present results and data from the literature, a moderate decrease of olfactory function appears to occur in as many as 20% of patients. However, anosmia seems to be an extremely rare complication of septoplasty and partial turbinectomy.

Olfactory modulation of nausea during early pregnancy?

OBJECTIVES

To investigate whether nausea and vomiting and olfactory sensitivity are correlated, we determined whether subjects with little or no nausea and vomiting are less sensitive to odours than subjects who indicate a high degree of nausea and vomiting, and whether subjects with relatively low olfactory sensitivity are less prone to nausea and vomiting than subjects with relatively higher olfactory sensitivity.

DESIGN

Cross sectional study.

SETTING

The Unit of Perinatal Physiology, Department of Obstetrics, University Hospital, Zurich, Switzerland.

POPULATION

Fifty-three women in early pregnancy.

METHODS

Following a detailed history related to olfaction and nausea and vomiting, subjects filled in a nausea profile which provided a 'general nausea score' comprised of the factors 'somatic distress', 'gastrointestinal distress', and 'emotional distress'. Olfactory function was assessed using pen-like odour dispensing devices ('sniffin' sticks'). Tests included n-butanol odour threshold, odour discrimination and odour identification.

MAIN OUTCOME MEASURES

Olfactory function assessed by means of the sniffing sticks nausea profile.

RESULTS

Correlational analyses between results of olfactory sensitivity and scores from the nausea questionnaire were not significant. Further, when subjects were divided into groups with relatively low or relatively high overall scores in the nausea profile, olfactory sensitivity did not differ between groups. Similarly, other analyses did not indicate a modulation of nausea and vomiting through olfactory sensitivity.

CONCLUSIONS

These findings do not support the hypothesis that higher olfactory sensitivity relates to an increase of nausea. However, they do support the idea that olfactory-induced nausea is independent of subjectively perceived intensity. Olfactory-induced nausea appears to be due to the cognitive processing of olfactory information which, in early pregnancy, is reported to be altered in an unsystematic fashion.

Lipoic acid in the treatment of smell dysfunction following viral infection of the upper respiratory tract

OBJECTIVES/HYPOTHESIS

The study aimed to investigate the potential therapeutic effects of alpha-lipoic acid in olfactory loss following infections of the upper respiratory tract. Possible mechanisms of actions include the release of nerve growth factor and antioxidative effects, both of which may be helpful in the regeneration of olfactory receptor neurons.

STUDY DESIGN

Unblinded, prospective clinical trial.

METHODS

A total of 23 patients participated (13 women, 10 men; mean age 57 y, age range 22-79 y; mean duration of olfactory loss, 14 mo; range, 4 to 33 mo); 19 of them were hyposmic and 4 had functional anosmia. Alpha-lipoic acid was used orally at a dose of 600 mg/day; it was prescribed for an average period of 4.5 months. Olfactory function was assessed using olfactory tests for phenyl ethyl alcohol odor threshold, odor discrimination, and odor identification.

RESULTS

Seven patients (30%) showed no change in olfactory function. Two patients (9%) exhibited a moderate decrease in olfactory function; in contrast, six patients (26%) showed moderate and eight patients (35%) remarkable increase in olfactory function. Two of the 4 patients with functional anosmia reached hyposmia; 5 of 19 hyposmic patients became normosmic. Overall, this resulted in a significant improvement in olfactory function following treatment (P =.002). At the end of treatment parosmias were less frequent (22%) than at the beginning of therapy (48%). Interestingly, recovery of olfactory function appeared to be more pronounced in younger patients than in patients above the age of 60 years (P =.018).

CONCLUSIONS

The results indicate that alpha-lipoic acid may be helpful in patients with olfactory loss after upper respiratory tract infection. However, to judge the true potential of this treatment, the outcome of double-blind, placebo-controlled studies in large groups of patients must be awaited, especially when considering the relatively high rate of spontaneous recovery in olfactory loss after upper respiratory tract infection.

Assessment of pharyngeal sensitivity to mechanical stimuli using psychophysical and electrophysiological techniques

The investigation was aimed to assess pharyngeal sensitivity by means of intensity ratings and event-related potentials (ERPs) to mechanical stimulation. Twenty healthy subjects participated (14 female, mean age 23.6 years). Both intensity ratings and ERP were obtained in response to three intensities of mechanical stimuli (air puffs) applied to the nasal cavity or the pharynx. Test-retest reliability was investigated for two sessions performed on different days. The study provided the following: (1) intensity ratings of nasal or pharyngeal stimuli increased with increasing stimulus intensity (P < 0.001); (2) they also exhibited a significant test-retest reliability (r </= 0.78) which was best for higher stimulus intensities; (3) ERP amplitudes increased and latencies shortened with increasing stimulus intensity (factor 'intensity': P < 0.013); (4) test-retest reliability was best at centro-frontal recording sites where significant correlations were found for both ERP amplitudes and latencies; (5) ERP to pharyngeal stimulation correlated significantly with perceived stimulus intensity (e.g., latency N1 at Cz: r = -0.73, P = 0.001). In conclusion, mechanical stimulation of the pharynx can be applied to reliably elicit ERPs which are related to both stimulus intensity and intensity ratings. This model may be useful in the investigation of cough-related changes in pharyngeal sensitivity.

Olfactory function in Parkinsonian syndromes

The study aimed to compare olfactory function in idiopathic Parkinson's disease (IPD) and nonidiopathic Parkinson's syndrome (PS). At their first visit 50 PS patients (age 38-80 years) received testing for odor threshold, olfactory discrimination and identification. All patients underwent extensive neurological diagnostics including PET scans. Patients were followed up for 6-12 months. Most of IPD patients were functionally anosmic (n=19), the remaining IPD patients had severe/moderate hyposmia (n=18). PS patients diagnosed with multiple system atrophy had less severe olfactory deficits (7 hyposmia, 1 normosmia). With the exception of 1 hyposmic patient, other PS patients had no olfactory deficits (progressive supranuclear palsy, corticobasal degeneration, psychogenic PS, essential tremor). This study added to previous findings: (1) there was no major difference betwesen olfactory function in IPD subtypes; (2) all olfactory tests differentiated IPD from nonIPD. These data suggest that olfactory probes improve the diagnostic armamentarium in IPD.

Development of a continuous respiration olfactometer for odorant delivery synchronous with natural respiration during recordings of brain electrical activity

The continuous respiration olfactometer (CRO) was designed as a respiration-synchronous method for delivering odorants during recordings of brain electrical activity, providing control and monitoring of the timing of the delivery as well as the quantities of odorant involved. The CRO incorporates a purpose-built electronic system designed with very specific temporal and quantitative characteristics, and is composed of four main parts: the respiratory monitoring apparatus, the odorant/air delivery system, the serial interface device and the respiratory monitoring software. Tests were undertaken to determine the performance of the system with reference to the accuracy and precision of timing and control of odorant delivery. Tests were also undertaken to determine the effects of variations in natural respiration between subjects on the capability of the respiratory monitoring system, using a group of 50 subjects, to test the success of a variable gain control to optimize the range of the digitized respiratory output. The delivery system was able to provide information concerning quantities of air or odorant delivered, and the stimulus timing information required for integration with neurophysiological recording techniques.

Olfactory function in HIV-positive subjects

The aim of this study was to reinvestigate previous reports of chemosensory dysfunction in HIV-positive subjects. Odor thresholds, odor discrimination and odor identification were assessed using the Sniffin' Sticks test battery. Seventy-four HIV-positive patients were tested. According to CDC criteria, 38 subjects were classified as stage A, 10 as stage B and 26 as stage C. None of the subjects exhibited severe cognitive impairment. Compared to normative data all subjects had normal odor identification and discrimination. However, odor thresholds were well below the median of a normal population. There were no significant differences between stage A, B or C subjects. This may be interpreted as indicating that olfactory dysfunction is among the primary deficits of HIV infection and occurs independently of disease stage. These results confirm previous work suggesting that odor thresholds are elevated early in HIV infection whereas a decline in identification and discrimination abilities is correlated with reduced cognitive abilities.

Olfactory Modulation of Steady- State Visual Evoked Potential Topography in Comparison with Differences in Odor Sensitivity

Summary Research was undertaken to determine whether olfactory stimulation can alter steady-state visual evoked potential (SSVEP) topography. Odor-air and air-only stimuli were used to determine whether the SSVEP would be altered when odor was present. Comparisons were also made of the topographic activation associated with air and odor stimulation, with the view toward determining whether the revealed topographic activity would differentiate levels of olfactory sensitivity by clearly identifying supra- and subthreshold odor responses. Using a continuous respiration olfactometer (CRO) to precisely deliver an odor or air stimulus synchronously with the natural respiration, air or odor (n-butanol) was randomly delivered into the inspiratory airstream during the simultaneous recording of SSVEPs and subjective behavioral responses. Subjects were placed in groups based on subjective odor detection response: “yes” and “no” detection groups. In comparison to air, SSVEP topography revealed cortical changes in response to odor stimulation for both response groups, with topographic changes evident for those unable to perceive the odor, showing the presence of a subconscious physiological odor detection response. Differences in regional SSVEP topography were shown for those who reported smelling the odor compared with those who remained unaware of the odor. These changes revealed olfactory modulation of SSVEP topography related to odor awareness and sensitivity and therefore odor concentration relative to thresholds.

Gustatory and olfactory function in the first trimester of pregnancy

OBJECTIVE

To investigate gustatory and olfactory sensitivity in the first trimester of pregnancy using validated test kits.

DESIGN

Prospective study.

SETTING

Department of Obstetrics, University Hospital Zurich, Switzerland.

POPULATION

Total 53 pregnant women and 59 controls in a known phase of the menstrual cycle.

METHOD

Gustatory sensitivity was assessed by requiring subjects to discriminate between four basic-taste tablets ('sweet', 'salty', 'sour', and 'bitter'). Olfactory testing was performed using the 'Sniffin' sticks' kit. Subjects rated the intensity and hedonic tone of the four tastants and of 10 common odors.

RESULTS

Pregnant women had significantly lower overall gustatory sensitivity scores. There were no differences in olfactory sensitivity. However, pregnant women rated the odors 'rum', 'cigarette' and 'coffee' as more aversive than did non-pregnant women.

CONCLUSION

Our data do not support the hypothesis of a generalized increase in chemosensitivity in early pregnancy. In terms of adaptive changes of the olfactory system may act as a sentinel to potentially harmful chemicals. In contrast, the gustatory system appears to retreat to allow a greater intake of electrolytes and a more widely sourced diet.

Screening of olfactory function with a four-minute odor identification test: reliability, normative data, and investigations in patients with olfactory loss

The study aimed to create a screening test on the basis of the odor identification test as used in the "Sniffin' Sticks" olfactory test kit. It should appeal to the practitioner in terms of 1) time required for testing, 2) reliability, 3) separation of "normal" from "abnormal," and 4) the fact that it allows lateralized screening. Experiments should provide a normative database (number of subjects > 1,000), establish test-retest reliability (n > 100), and compare results from patients with olfactory loss (n > 200). The correlation between results on 2 repetitive tests was .78. The test differentiated anosmics, hyposmics, and normosmics (p < .001). None of the 112 anosmics reached a score higher than 8; the 90th percentile was at a score of 6. When only 6 odors were used for calculating scores, for anosmics the 95th percentile was at a score of 4. These data provide a basis for the screening of patients by means of "Sniffin' Sticks."

Brain activation during odor perception in males and females

Several studies indicate that women outperform men in olfactory identification tasks. The psychophysical data are more divergent when it comes to gender differences at levels of odor processing which are cognitively less demanding. We therefore compared cerebral activation with H2(15)O PET in 12 females and 11 males during birhinal passive smelling of odors and odorless air. The odorous compounds (odorants) were pure olfactory, or mixed olfactory and weakly trigeminal. Using odorless air as the baseline condition, activations were found bilaterally in the amygdala, piriform and insular cortices in both sexes, irrespective of the odor. No gender difference was detected in the pattern of cerebral activation (random effect analysis SPM99, corrected p < 0.05) or in the subjective perception of odors. Males and females seem to use similar cerebral circuits during the passive perception of odors. The reported female superiority in assessing olfactory information including odor identification is probably an effect of a difference at a cognitive, rather than perceptive level of olfactory processing.

Unilateral olfactory perception and magical ideation

We assessed olfactory detection thresholds and discrimination abilities in 40 healthy right-handers (20 women and 20 men). All subjects were also required to complete the Magical Ideation (MI) scale, a well-validated 30-item schizotypy inventory. Over both nostrils, we found elevated thresholds for subjects with high MI scores (at or above the median score of 9.0) compared with those with low scores. In men but not women, specifically left-nostril acuity was inversely correlated to MI raw scores. MI was unrelated to olfactory discrimination performance. These results suggest an association, at least in healthy men, between even moderate signs of schizotypy and deficits in odor detection. The selective impairment of left-nostril performance adds to the growing evidence for left temporal lobe functional abnormalities in people high on MI. This laterality effect is known from previous studies in patients with schizophrenia. However, as a rule, in psychiatric patients olfactory identification rather than simple detection performance was found to be impaired, indicating that the integration of odor information is affected at different levels of processing in schizotypy compared with schizophrenia. Work with completely normal subjects may reasonably complement clinical studies of olfactory perception. Among its advantages are the good subject compliance and the absence of medication effects.

Qualitative and quantitative olfactometric evaluation of different concentrations of ethanol peppermint oil solutions

Selection of an adequate placebo is a major problem in clinical trials of Euminz(R) (10% peppermint oil/ethanol) which is used topically for the treatment of tension-type headache. This randomized, controlled, double-blind, cross-over study was performed to investigate whether there are qualitative differences between 10%, 1%, 0.5%, 0.1%, and 0% peppermint oil. Forty-one healthy subjects participated (age range 21-28 years); they rated both intensity, and hedonic tone of the stimuli. Verbal descriptions were combined to multiple response sets (MRS). In addition, the trigeminal impact of odorants was determined. Intensity ratings and MRS "menthol like" and "alcohol/solvent" changed with stimulus concentration. However, intensity had no significant effect on hedonics, trigeminal impact, or the number of descriptive items used. When MRS "menthol like" and "alcohol/solvent" were analysed after being weighted with intensity ratings, changes in relation to stimulus concentration were lost. Thus, the differences between the five concentrations of peppermint oil were--to their largest part--due to changes in stimulus intensity. Considering the large day-to-day variability of olfactory sensitivity the present data support the hypothesis that the odour quality of 10% peppermint oil cannot be discriminated from the odour of 0.1%, 0.5%, or 1% peppermint oil when tested on separate days.

Olfactory function in patients with olfactory groove meningioma

OBJECTIVES

Olfactory meningiomas are rare benign tumours and represent about 12% of all basal meningiomas. Anosmia is thought to be among the first symptoms, even though patients often present with headaches or visual problems. However, so far no detailed psychophysical tests of olfactory function have been performed in a large number of those patients.

METHODS

Twelve patients (five men, seven women; mean age 52 years) with olfactory meningiomas were examined. In all patients extensive preoperative and postoperative lateralised olfactory testing was performed using the "Sniffin' Sticks" test battery, a psychometric testing tool. In eight cases the meningioma was lateralised (five left, three right), in four patients a bilateral meningioma was found. In addition to a detailed ear, nose, and throat examination MRI was performed in all patients.

RESULTS

In preoperative testing six patients were found to be anosmic on the side of the tumour, two were hyposmic. Four patients were normosmic. Postoperative investigations showed lateralised anosmia in four patients on the operated side, three were normosmic on the contralateral side and one hyposmic. The remaining eight patients were completely anosmic postoperatively.

CONCLUSIONS

(1) Contrary to expectations, olfactory testing seems to be of little help in detecting olfactory meningiomas. (2) The likelihood of normal postoperative olfactory function contralateral to the tumour was high when the tumour was less than 3 cm in diameter and preoperative normosmia had been established. (3) Preservation of olfactory function ipsilateral to the tumour seems to be extremely difficult, irrespective of tumour size or surgical approach.

Olfactory and trigeminal event-related potentials in migraine

BACKGROUND

Trigeminal/neuronal hyperexcitability and spreading depression activating the trigemino-vascular system are discussed in migraine-pathophysiology. This study investigated trigeminal and olfactory event-related potentials in migraineurs.

METHODS

Nasal chemosensitivity was assessed in 19 female migraineurs with or without aura > 72 h before or after an attack and in 19 healthy females employing event-related cortical potentials (ERPs) after specific trigeminal stimulation of nasal nociceptors with short pulses of CO2, and specific olfactory stimulation with H2S. Odour thresholds and odour identification performance were also tested.

RESULTS

Migraineurs exhibited greater responses to trigeminal stimulation, indicated by significantly larger ERP amplitudes N1. In contrast, olfactory ERP amplitudes P1N1 were significantly smaller in migraineurs. A leave-one-out classification procedure on the basis of these two parameters assigned 76.3% cases correctly. The olfactory ERP amplitude discriminated better between groups than trigeminal ERPs (71.1 vs. 68.4% correct classification).

CONCLUSIONS

Our data suggest trigeminal hyperexcitability in migraineurs. A general increase of nasal chemosensitivity is not supported because of smaller olfactory ERP amplitudes in migraineurs. Olfactory ERPs discriminate better than trigeminal ERPs between migraineurs and controls, emphasizing the significance of the olfactory system in migraine.