Omega-3 supplementation in postviral olfactory dysfunction: a pilot study.

BACKGROUND: This study aimed to examine whether omega-3 supplementation would support olfactory recovery among postviral olfactory dysfunction patients. METHODOLOGY: Patients with postviral olfactory dysfunction were included in this non-blinded, prospective pilot study. Structured medical history was taken from the patients, including the following: age, sex, history of COVID-19 infection, and duration of symptoms. Patients were randomly assigned to receive olfactory training only (control group) versus olfactory training with omega-3 supplementation (treatment group). All patients exposed themselves twice a day to four odours (phenyl ethyl alcohol [rose], eucalyptol [eucalyptus], citronellal [lemon], and eugenol [cloves]). Olfactory function was measured before and after training using 'Sniffin' Sticks', comprised of tests for odour threshold, discrimination, and identification. The average interval between olfactory tests was 3 months. RESULTS: Fifty-eight patients were included in the study, 25 men and 33 women. Generally, an improvement in olfactory scores was observed. Compared to the control group, the improvement in odour thresholds was more pronounced in the omega-3 group. Age, sex, and duration of symptoms had no effect on olfactory scores among both control and treatment groups. CONCLUSION: Overall, the present results indicate that omega-3 supplementation may be an option for adjunct therapy with olfactory training in patients with postviral olfactory dysfunction.

The smelling of Hedione results in sex-differentiated human brain activity.

A large family of vomeronasal receptors recognizes pheromone cues in many animals including most amphibia, reptiles, rhodents, and other mammals. Humans possess five vomeronasal-type 1 receptor genes (VN1R1-VN1R5), which code for proteins that are functional in recombinant expression systems. We used two different recombinant expression systems and identified Hedione as a ligand for the putative human pheromone receptor VN1R1 expressed in the human olfactory mucosa. Following the ligand identification, we employed functional magnetic resonance imaging (fMRI) in healthy volunteers to characterize the in vivo action of the VN1R1 ligand Hedione. In comparison to a common floral odor (phenylethyl alcohol), Hedione exhibited significantly enhanced activation in limbic areas (amygdala, hippocampus) and elicited a sex-differentiated response in a hypothalamic region that is associated with hormonal release. Utilizing a novel combination of methods, our results indicate that the putative human pheromone receptor VN1R1 is involved in extra-olfactory neuronal activations induced by the odorous substance Hedione. The activation of VN1R1 might play a role in gender-specific modulation of hormonal secretion in humans.

The fate of the inner nose: odor imagery in patients with olfactory loss.

Cerebral activations during olfactory mental imagery are fairly well investigated in healthy participants but little attention has been given to olfactory imagery in patients with olfactory loss. To explore whether olfactory loss leads to deficits in olfactory imagery, neural responses using functional magnetic resonance imaging (fMRI) and self-report measures were investigated in 16 participants with acquired olfactory loss and 19 control participants. Participants imagined both pleasant and unpleasant odors and their visual representations. Patients reported less vivid olfactory but not visual images than controls. Results from neuroimaging revealed that activation patterns differed between patients and controls. While the control group showed stronger activation in olfactory brain regions for unpleasant compared to pleasant odors, the patient group did not. Also, activation in critical areas for olfactory imagery was correlated with the duration of olfactory dysfunction, indicating that the longer the duration of dysfunction, the more the attentional resources were employed. This indicates that participants with olfactory loss have difficulties to perform olfactory imagery in the conventional way. Regular exposure to olfactory information may be necessary to maintain an olfactory imagery capacity.

The effect of a herbal combination of primrose, gentian root, vervain, elder flowers, and sorrel on olfactory function in patients with a sinonasal olfactory dysfunction.

Olfactory dysfunction is a common symptom in patients with inflammation of the nasal mucosa. Among numerous drugs, so far only the use of steroids has been shown to have a positive effect on olfactory function. Therefore the aim of the present study was to investigate whether patients with sinonasal disease would benefit in terms of olfactory function from oral treatment with a herbal drug (combination of primrose, gentian root, vervain, elder flowers, and sorrel: Sinupret(r)) which is commonly used in sinusitis. Olfactory function was tested using a standardised olfactory test kit (`sniffin` sticks`). The drug was applied in a double-blind fashion: after an initial therapy of 7 days of oral prednisolone for all participants with a sinonasal olfactory disease, participants were divided into a placebo- and a verum-group; tests were performed before and after treatment over a 2 months period. Statistical analysis did not reveal any major differences in olfactory function in relation to treatment. Considering that its benefit for the inflammatory component of sinusitis has been shown, the herbal drug may exhibit positive effects on olfactory function in a different setting, e.g., when applied without preceding administration of prednisolone, or when used in patients with certain degrees of rhinosinusitis.

Effects of deep brain stimulation of the cerebellothalamic pathways on the sense of smell.

The cerebellum and the motor thalamus, connected by cerebellothalamic pathways, are traditionally considered part of the motor-control system. Yet, functional imaging studies and clinical studies including patients with cerebellar disease suggest an involvement of the cerebellum in olfaction. Additionally, there are anecdotal clinical reports of olfactory disturbances elicited by electrical stimulation of the motor thalamus and its neighbouring subthalamic region. Deep brain stimulation (DBS) targeting the cerebellothalamic pathways is an effective treatment for essential tremor (ET), which also offers the possibility to explore the involvement of cerebellothalamic pathways in the sense of smell. This may be important for patient care given the increased use of DBS for the treatment of tremor disorders. Therefore, 21 none-medicated patients with ET treated with DBS (13 bilateral, 8 unilateral) were examined with "Sniffin' Sticks," an established and reliable method for olfactory testing. Patients were studied either with DBS switched on and then off or in reversed order. DBS impaired odor threshold and, to a lesser extent, odor discrimination. These effects were sub-clinical as none of the patients reported changes in olfactory function. The findings, however, demonstrate that olfaction can be modulated in a circumscribed area of the posterior (sub-) thalamic region. We propose that the impairment of the odor threshold with DBS is related to effects on an olfacto-motor loop, while disturbed odor discrimination may be related to effects of DBS on short-term memory.

Intranasal trigeminal sensitivity in subjects with allergic rhinitis.

Trigeminal nerve endings of the human nasal mucosa are activated by chemical, physical or thermal stimuli. Activation of these A(delta) and C fibers can be quantified through the recording of chemo-somatosensory event-related potentials (ERP). The aim of this study was to investigate whether allergy-related activation of trigeminal nerve endings leads to changes in their responsiveness to intranasal trigeminal stimulation. Gaseous carbon dioxide (CO(2)) stimuli were applied in three sessions (baseline, after NaCl solution and after allergen application) to the nasal mucosa of 13 subjects with allergic rhinitis. Chemo-somatosensory ERP were recorded, and subjects rated the intensity of rhinitis symptoms. Administration of allergen produced a significant shortening of chemo-somatosensory ERP peak latencies P1 and N1. Observed changes of latencies were in line with rhinitis symptoms subjects indicated during the session. In addition, there was a negative relation between the general symptom score and ERP peak latencies, obtained both at baseline and after allergen exposure. In conclusion, it is hypothesized that in patients suffering from allergic rhinitis, nasal itching and sneezing after allergen exposure are, at least in part, clinical correlates of the activation of trigeminal nerve endings due to local inflammatory mechanisms. The correlations between ERP latencies and the patients' symptoms indicate that ERP latencies may possess a predictive value of the subjects' responsiveness to allergens.

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.

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.

Analgesic effects of dihydrocodeine and tramadol when administered either in the morning or evening.

The aim of the study was to investigate the analgesic effects of two opioids [dihydrocodeine (DHC) and tramadol] when administered either in the morning or evening. The experimental technique used is based on chemosomatosensory event-related potentials (CSSERPs) in response to painful chemical stimuli that are applied to the nasal mucosa. Eighteen healthy volunteers participated in the experiments. The study followed a controlled, randomized, double-blind, sixfold, cross-over design. Thus, each of the three medications (90 mg DHC, 50 mg tramadol, or placebo) was perorally administered to all subjects on different days at 08:00 or 20:00 h. Measurements were performed before and 60, 120, 240, and 360 min after administration of the medication. In addition to the assessment of CSSERP, subjects rated the intensity of the stimuli. Moreover, unspecific drug effects were monitored by means of acoustical event-related potentials and the subjects' performance in a video game. The results indicated that the painful intensity of the chemical stimuli strongly increased during evening sessions. In addition, both DHC and tramadol exerted stronger analgesic effects when administered in the evening. Thus, an inflexible scheme of prescription might produce either an increase of pain in the morning due to insufficient analgesia or the unnecessary overdosing of analgesics in the evening.