Intranasal Trigeminal Sensitivity Research Articles

Topical intranasal anesthesia impairs trigeminal function and airflow perception

Background: Impairment of airflow perception by the intranasal trigeminal system may explain chronic nasal obstruction (CNO), especially in cases where no major deformity or mucosal inflammation can explain reduced airflow. We aim to characterize the effect of topical intranasal anesthesia on intranasal trigeminal sensitivity and consequently the sensation of nasal obstruction. Methodology: We performed a crossover study of 16 healthy subjects, randomised for either treatment (topical intranasal anesthesia with 10% Xylocaine) or placebo (saline solution). We used the Trigeminal Lateralization Task (TLT) with eucalyptol to assess trigeminal sensitivity. We measured nasal patency objectively with Peak Nasal Inspiratory Flow (PNIF), and subjectively with a Visual Analog Scale (VAS), the Empty Nose Syndrome 6-Item Questionnaire (ENS6Q), and the Nasal Obstruction Symptom Evaluation (NOSE) questionnaire. Results: Topical intranasal anesthesia significantly reduced intranasal trigeminal sensitivity. Further, after topical intranasal anesthesia, reduced trigeminal sensitivity was associated with the subjectively reduced nasal patency, as highlighted by ENS6Q and NOSE scores. Conclusions: Topical intranasal anesthesia reduces intranasal trigeminal function resulting in subjectively reduced nasal patency. In future studies, the relation of reduced intranasal trigeminal function and subjective nasal obstruction needs to be addressed to open an avenue for potential interventions for an important portion of ENT patients.

Children and adolescents with primary headaches exhibit altered sensory profiles – a multi-modal investigation

BackgroundPediatric headache is an increasing medical problem that has adverse effects on children’s quality of life, academic performance, and social functioning. Children with primary headaches exhibit enhanced sensory sensitivity compared to their healthy peers. However, comprehensive investigations including multimodal sensory sensitivity assessment are lacking. This study aimed to compare sensory sensitivity of children with primary headaches with their healthy peers across multiple sensory domains.MethodsThe study included 172 participants aged 6 to 17 years (M = 13.09, SD = 3.02 years; 120 girls). Of these 80 participants were patients with migraine, 23 were patients with tension-type headache, and 69 were healthy controls. The following sensory measures were obtained: Mechanical Detection Threshold (MDT), Mechanical Pain Threshold (MPT), Mechanical Pain Sensitivity (MPS), detection and pain threshold for Transcutaneous Electrical Nerve Stimulation (TENS), olfactory and intranasal trigeminal detection threshold, and odor identification ability. Sensory sensitivity was compared between groups with a series of Kruskal-Wallis tests. Binomial regression models were used to compare the relative utility of sensory sensitivity measures in classifying participants into patients and healthy controls, as well as into patients with migraine and tension-type headache.ResultsPatients with migraine had lower MPT measured at the forearm than patients with tension-type headaches and healthy controls. MPS was higher in patients with migraine than in healthy controls. All patients with headaches had lower detection threshold of TENS and higher olfactory sensitivity. Healthy controls showed increased intranasal trigeminal sensitivity. Scores in MPS, TENS, and olfactory and trigeminal thresholds were significantly predicting presence of primary headaches. Additionally, scores in MPT, olfactory and trigeminal threshold were positive predictors of type of headache.ConclusionsChildren with primary headaches exhibit different sensory profiles than healthy controls. The obtained results suggest presence of increased overall, multimodal sensitivity in children with primary headaches, what may negatively impact daily functioning and contribute to further pain chronification.Trial registrationThe study was registered in the German Registry of Clinical Trials (DRKS) DRKS00021062.

Intranasal trigeminal sensitivity to mechanical stimuli is associated with the perception of nasal patency.

The aim of this prospective study was to examine the characteristics of a clinical test for the assessment of nasal trigeminal sensitivity to mechanical stimuli and its association with the perception of nasal patency. Thirty-two normosmic healthy subjects participated (17 women and 15 men; age = 26 ± 3years). Precisely defined air puffs were used with a flow rate of 2L/min for mechanical stimulation. They were presented to the nasal vestibule, nasal septum, and inferior turbinate with various stimulus durations. Thresholds were measured by single-staircase stimuli with changes in stimulus duration in steps of 10ms. Trigeminal suprathreshold intensity was rated by subjects for stimulus durations of 200, 300, 400, and 500ms. Test-retest reliability was examined by intraclass correlations (ICCs) and Bland-Altman plot with limits of agreement. Pearson's correlations were calculated between self-rated nasal patency and nasal trigeminal sensitivity. As indicated by trigeminal threshold and suprathreshold intensities, the nasal vestibule is the most sensitive area among the three locations, followed by the nasal septum and the inferior turbinate (p < 0.001). Coefficients of correlations between test and retest were 0.76 for thresholds, and 0.56 suprathreshold intensities (p < 0.001). The Bland-Altman analysis showed a good agreement between test-retest values. In addition, significant positive associations between trigeminal suprathreshold intensities and self-rated nasal obstruction were found at the inferior turbinate (r = 0.4, p < 0.05). Reliable assessment of nasal trigeminal sensitivity for air puffs appears to be possible. Nasal trigeminal suprathreshold sensitivity to mechanical stimuli is associated with the perception of nasal patency at the inferior turbinate. This opens a window into the assessment of the perception of nasal airflow in various clinical purposes, especially for patients with sinonasal diseases.

Regional brain morphology of the primary somatosensory cortex correlates with spicy food consumption and capsaicin sensitivity

ABSTRACT Objective: Habitual spicy food consumption leads to altered perception of capsaicin. Little is known about the neural morphological correlates of habitual spicy food intake and related trigeminal perceptions. In this study, we used voxel-based morphometry to identify brain regions where regional gray matter volume (GMV) correlates to spicy food consumption. Methods: Fifty-two participants were surveyed for their spicy food dietary habit by a composite score of spicy diet duration, frequency of spicy food consumption, and preferred degree of spiciness. Forty-two participants were further assessed for oral sensitivity and intensity ratings of capsaicin-induced irritation, and intranasal sensitivity and intensity of trigeminal odors. Results: We found that the composite spicy score was positively correlated to GMV of the primary somatosensory area (SI), and the primary (M1), supplementary motor areas (SMA) and the putamen. It was negatively correlated to GMV of the anterior insula, orbitofrontal cortex, frontal gyrus and angular gyrus. The GMV of the SI area was negatively correlated to capsaicin sensitivity; the GMV of the right middle frontal gyrus was positively correlated to the irritative intensity for capsaicin at high concentration (70 μM). However, we observed no correlation between the intranasal trigeminal sensitivity and spicy food consumption or the regional GMV. Discussion: Collectively our findings suggest a central neuroanatomical reflection of altered capsaicin perception in relation to habitual spicy food consumption. Future longitudinal studies should elucidate the possible causal relationship of dietary habit and brain structural plasticity.

Intranasal trigeminal sensitivity may be impaired after functional nasal surgery

Functional nasal surgery is frequently performed for sinonasal diseases not responding to medical treatment. Although surgery mostly turns out to be successful in such cases, a potential side effect of manipulating the nasal mucous membrane is impairment of intranasal trigeminal function. Not well known by specialists and clinically scarcely explored, this function provides sensory information from the nasal mucosa. It is responsible for the afferent part of protective nasal reflexes such as sneezing and coughing, but also provides the feeling of nasal airflow (1). Recent work suggests that patients with low intranasal trigeminal function are more prone to suffer from nasal obstruction and may be less satisfied with functional surgery (2-6). It has been suggested that intranasal trigeminal function decreases with mucosal changes, such as chronic inflammation and improves again once the inflammation has been treated (3). However, the influence of functional nasal surgery (i.e. surgery aimed at the improvement of nasal function) with consecutive mucosal micro-injuries on intranasal trigeminal function is not yet fully clear (2-4).

Frequent spicy food consumption is associated with reduced capsaicin and salty taste sensitivity but unchanged sour taste or intranasal trigeminal sensitivity

The trigeminal and gustatory perceptions interact with each other during food consumption. Long-term repeated exposure to sensory stimuli leads to plasticity of sensory perception. The present study was conducted to test (i) the effect of frequent spicy food consumption on oral and intranasal trigeminal sensitivity, taste perception; and (ii) the effect of capsaicin at recognition threshold concentration on taste perception among individuals with different spicy food consumption frequencies. Seventy female college students were divided into the high frequency (HF; n = 35) and the low frequency (LF; n = 35) spicy consumption groups based on their self-reported spicy food consumption frequency. We assessed the recognition threshold (using a 3-alternative forced choice task) and suprathreshold intensity (on a generalized labeled magnitude scale) for capsaicin, salty and sour tastes, as well as the intranasal trigeminal sensitivity for menthol and mustard oil odors using the odor lateralization task. Sensitivity and intensity for salty and sour tastes were assessed with and without addition of capsaicin at the group-averaged recognition threshold level (1.38 μM). Compared with the LF group, the HF group had decreased sensitivity for capsaicin and salty taste, and decreased perceived irritative intensity of suprathreshold capsaicin. However, there was no difference for sour taste perception or intranasal trigeminal sensitivity between the two groups. The addition of 1.38 μM capsaicin showed no effect on salty or sour taste sensitivity. However, decreased supra-threshold intensity for salty taste was found in the presence of 1.38 μM capsaicin among participants with high frequency of spicy food consumption (the HF group). These findings suggested that long-term habitual spicy food consumption is related to alteration of oral perception of capsaicin and certain taste.

Oral Somatosensory Sensitivity in Patients With Taste Disturbance.

The significance of the human sense of taste is typically underestimated until it is altered or even lost. Hypogeusia, a diminished capacity to taste, has an adverse influence on a patient's quality of life. Similar to interactions between the oral senses and between olfaction and intranasal trigeminal sensitivity, taste disturbance may also affect the mechanosensitivity of the tongue. In this study, we investigated the lingual tactile sensitivity of patients with subjective taste disturbance and people with normogeusia. Prospective case-control study. Forty-six patients with subjective taste disturbance (mean age 60 years) and 43 participants with normogeusia (mean age 55 years) were enrolled and underwent a stereognostic test of edge and point sensitivity based on 3D-printed letters sized from 2 to 8 mm. Gustatory function and salivary production were also tested. Patients with dysgeusia needed significantly bigger letters to recognize them compared with controls (P=.01). Apart from this, patients with dysgeusia had no significant association between gustatory function and salivary production. Duration of dysgeusia and age were not associated with the presently obtained measures of gustatory or oral mechanosensory function. The results of this study indicate that taste dysfunction has a negative impact on oral mechanosensitivity and hence possibly on oral texture perception. 3 Laryngoscope, 131:2572-2577, 2021.

Data Science-Based Analysis of Patient Subgroup Structures Suggest Effects of Rhinitis on All Chemosensory Perceptions in the Upper Airways

Viral rhinitis contributes significantly to olfactory dysfunction, but it is unclear how many patients have other chemosensory symptoms in addition to olfactory loss. This was addressed in the present reanalysis of data previously published in Pellegrino R, Walliczek-Dworschak U, Winter G, Hull D, Hummel T. 2017. Investigation of chemosensitivity during and after an acute cold. Int Forum Allergy Rhinol. 7(2):185-191, using unsupervised and supervised machine-learning methods. Fifty-eight patients with acute rhinitis and 59 healthy controls were assessed for orthonasal and retronasal olfactory function, taste, and intranasal trigeminal sensitivity. Unsupervised analysis showed that during rhinitis, clinical scores of olfactory function, expressed as threshold, discrimination, identification (TDI) values, were trimodally distributed. Two minor modes were separated from the main mode at TDI = 30.5, which corresponds to the established limit of hyposmia. This trimodal distribution was not observed after the rhinitis subsided. Olfactory function was not significantly impaired in 40% of all rhinitis patients, whereas it was transiently impaired in 59%. For this group, supervised machine-learning algorithms could be trained with information on retronasal olfactory function, gustatory function, and trigeminal sensitivity to assign patients to subgroups based on orthonasal olfactory function with a balanced classification accuracy of 64-65%. The ability to recognize patients with olfactory loss based on retronasal olfactory function as well as gustatory function and trigeminal sensitivity suggests in turn that these modalities are affected by rhinitis. However, the only modest accuracy at which this information allowed to reproduce the olfactory diagnosis indicated they are involved in the symptomatology of rhinitis to a lesser extent compared with the orthonasal olfactory function.

Chemosensory decrease in different forms of olfactory dysfunction.

The aim of this study is to investigate the effect of olfactory dysfunction (OD) on the two other chemical senses, namely gustation and the intranasal trigeminal system. Taste and trigeminal function were analyzed in a retrospective cross-sectional study of 178 participants with OD (n = 78 posttraumatic, n = 42 idiopathic, n = 27 post-infectious and n = 31 chronic rhinosinusitis (CRS) OD). All patients had been investigated for OD at our smell and taste outpatient clinic. Evaluation of olfaction was performed by means of the Sniffin' Sticks test (odor threshold, odor discrimination and odor identification), whereas gustatory function was assessed with the Taste Strips test and the intranasal trigeminal sensitivity by means of the lateralization task. The degree of olfactory impairment was found to depend on the cause of OD, but not on patients' age. Patients with posttraumatic OD showed lower olfactory function than patients with idiopathic, post-infectious and CRS OD (p = 0.01). Gustatory and trigeminal sensitivity in turn depended on age rather than the cause of olfactory dysfunction. Partial correlations between olfactory, gustatory, and trigeminal scores, with age as covariate, were significant, showing a decrease of taste and trigeminal function proportional to the OD (p < 0.05). The present data suggest that the three chemical senses are closely connected for humans underlining that in case of OD the remaining chemical senses (taste, trigeminal function) tend to decrease rather than compensate as this is seen for sensory loss in other modalities. This finding has direct clinical implications and importance when dealing with smell and taste disorders.

A Novel Device for the Clinical Assessment of Intranasal Trigeminal Sensitivity

Despite the significance of trigeminal pathology, practical clinical tests that accurately evaluate intranasal trigeminal function are scarce. The aim of the present study is to introduce a practical procedure for the assessment of intranasal trigeminal sensitivity. We developed a device to stimulate the nasal mucosa using carbon dioxide, which is self-administered intranasally by holding down a timed button until the required sensory response has been triggered. The trigeminal sensitivity is derived from the measured administration time in conjunction with the concentration of carbon dioxide administered. Sixty-three healthy participants were used to validate the device, after which the new device was compared with a standard lateralization task in an additional 16 participants. In 20 participants, the experiment was repeated to verify test-retest reliability. Statistical analysis showed significant consistency in administration-duration in healthy individuals, including those in the test-retest group. Those participants with higher scores in the lateralization task were found to show higher intranasal sensitivity measured by the new device. Herein, we present the design and validation of a novel device for the practical assessment of intranasal trigeminal sensitivity. In this study, we demonstrate the efficacy and reliability of this device.

Intranasal trigeminal sensitivity: measurements before and after nasal surgery

Nasal surgeries constitute an extensive manipulation of the nasal mucosa and therefore of structures related to trigeminal and olfactory sensitivity. While olfactory changes due to nasal surgery are relatively well investigated, there are only very few studies regarding trigeminal sensitivity. Aim of the present study was to investigate sensory changes after nasal surgery with special regard to the trigeminal sensitivity. In 38 patients prior to and around 12 weeks after nasal surgery the following psychophysical measures were performed: odor identification, odor discrimination, phenyl ethyl alcohol odor threshold, sensitivity to trigeminal stimuli, trigeminal detection thresholds and trigeminal pain thresholds. These results were compared to those of a control group (43 healthy volunteers). Psychophysical olfactory and trigeminal testing showed no major changes in patients after surgery compared to the control group. Independent from the time of measurement higher trigeminal detection thresholds were found in patients compared to healthy subjects, meaning that trigeminal thresholds were already increased before surgery. The present study revealed a decreased trigeminal sensitivity in patients already before surgery. It may be hypothesized that patients also exhibit a decreased sensitivity for nasal airflow, which may also contribute to the patients' impression of impaired nasal breathing.

Mexico City Air Pollution Adversely Affects Olfactory Function and Intranasal Trigeminal Sensitivity

Surprisingly little is known about the effects of big-city air pollution on olfactory function and even less about its effects on the intranasal trigeminal system, which elicits sensations like burning, stinging, pungent, or fresh and contributes to the overall chemosensory experience. Using the Sniffin' Sticks olfactory test battery and an established test for intranasal trigeminal perception, we compared the olfactory performance and trigeminal sensitivity of residents of Mexico City, a region with high air pollution, with the performance of a control population from the Mexican state of Tlaxcala, a geographically comparable but less polluted region. We compared the ability of 30 young adults from each location to detect a rose-like odor (2-phenyl ethanol), to discriminate between different odorants, and to identify several other common odorants. The control subjects from Tlaxcala detected 2-phenyl ethanol at significantly lower concentrations than the Mexico City subjects, they could discriminate between odorants significantly better, and they performed significantly better in the test of trigeminal sensitivity. We conclude that Mexico City air pollution impairs olfactory function and intranasal trigeminal sensitivity, even in otherwise healthy young adults.

Mexico City Air Pollution Adversely Affects Olfactory Function and Intranasal Trigeminal Sensitivity

Event Abstract Back to Event Mexico City Air Pollution Adversely Affects Olfactory Function and Intranasal Trigeminal Sensitivity Marco Guarneros1*, Thomas Hummel2, Margaríta Martinez-Gomez3 and Robyn Hudson1 1 Universidad Nacional Autonoma de Mexico, Instituto de Investigaciones Biomedicas, Mexico 2 University of Dresden, Medical School, Riechen und Schmecken Klinik, Germany 3 Universidad Autonoma de Tlaxcala, Centro Tlaxcala de Biologia de la Conducta, Mexico Using the Sniffin Sticks olfactory test battery and an established test for intranasal trigeminal function we compared the olfactory performance and trigeminal sensitivity of 30 young adult residents of Mexico City, a region with high air pollution, with the performance of an equivalent control population from the neighboring Mexican state of Tlaxcala, a less polluted region (15 men and 15 women for each region, all non-smokers). Subjects from Mexico City had significantly lower scores than subjects from Tlaxcala in the olfactory threshold and discrimination tests, as well as in the test of trigeminal sensitivity. We conclude that Mexico City air pollution impairs olfactory function and intranasal trigeminal sensitivity, even in otherwise healthy young adults. (Support to MG from CONACyT -28879- Posgrado en Ciencias Biológicas, UNAM). Conference: Summer School on Human Olfaction, Dresden, Germany, 19 Jul - 25 Jul, 2009. Presentation Type: Poster Presentation Topic: Abstracts Citation: Guarneros M, Hummel T, Martinez-Gomez M and Hudson R (2009). Mexico City Air Pollution Adversely Affects Olfactory Function and Intranasal Trigeminal Sensitivity. Conference Abstract: Summer School on Human Olfaction. doi: 10.3389/conf.neuro.09.2009.12.007 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 22 Jul 2009; Published Online: 22 Jul 2009. * Correspondence: Marco Guarneros, Universidad Nacional Autonoma de Mexico, Instituto de Investigaciones Biomedicas, Tlaxcala, Mexico, marco.mexico@hotmail.com Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Marco Guarneros Thomas Hummel Margaríta Martinez-Gomez Robyn Hudson Google Marco Guarneros Thomas Hummel Margaríta Martinez-Gomez Robyn Hudson Google Scholar Marco Guarneros Thomas Hummel Margaríta Martinez-Gomez Robyn Hudson PubMed Marco Guarneros Thomas Hummel Margaríta Martinez-Gomez Robyn Hudson Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

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.

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.

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.

Decreased Trigeminal Sensitivity in Anosmia

The present study aimed to investigate intranasal trigeminal sensitivity in a large sample of patients with anosmia due to different etiologies. We investigated the trigeminal detection threshold for formic acid in healthy controls (n = 96) and patients with anosmia due to head trauma (n = 18) or sinonasal disease (n = 54). Anosmics exhibited higher thresholds compared with normosmics (p < 0.001). In addition, thresholds were found to be higher in patients with posttraumatic anosmia compared to anosmics with sinonasal disease (p < 0.001). The data indicate that (1) loss of olfactory sensitivity in humans may be associated with a decreased sensitivity towards trigeminal stimuli and (2) alteration of intranasal trigeminal function is stronger in patients with posttraumatic anosmia compared to patients with sinonasal disease. This may have implications for the medicolegal investigation of anosmic patients where trigeminal stimuli are frequently used to assess the patient’s response bias.