Search

Aim: The "Sniffin' Sticks" test is widely used in Europe as a standard test to assess olfaction. Several culturally-adapted versions have been developed. However, no version adapted to Sub-Saharan African populations exists. The aims of the present study were (1) to assess the applicability of the Sniffin' Sticks test in the population of South Kivu (DR Congo), and (2) to develop a culturally adapted version with normative values., Materials and Methods: In a first study, 157 volunteers were tested with the original Sniffin' Sticks test. Based on these results, we selected odors that were poorly recognized in the identification test and replaced them by culturally adapted odors. In a second study, we assessed the modified version of the Sniffin' Sticks test in 150 volunteers and defined normative values., Results: In the first study, we found that olfactory function (threshold-discrimination-identification: TDI score) significantly decreased with age and was better in females. Five odors were poorly recognized and were replaced by culturally adapted odors. In the second study, we found that this adapted version led to a higher rate of correctly identified odors. We defined normative values for the South-Kivu population (TDI score: 18-35 years: 30.4±6.0; 36-55 years: 26.2±5.3; >55 years: 25.6±5.0)., Conclusion: This culturally adapted version of the Sniffin' Sticks test is culturally adapted to the South Kivu population. The normative values will provide the basis for clinical evaluation of pathologic subjects., (Copyright © 2020 Elsevier Masson SAS. All rights reserved.)

The presence of cerebral lesions in patients with neurosensory alterations provides a unique window into brain function. Using a fuzzy logic based combination of morphological information about 27 olfactory-eloquent brain regions acquired with four different brain imaging techniques, patterns of brain damage were analyzed in 127 patients who displayed anosmia, i.e., complete loss of the sense of smell (n = 81), or other and mechanistically still incompletely understood olfactory dysfunctions including parosmia, i.e., distorted perceptions of olfactory stimuli (n = 50), or phantosmia, i.e., olfactory hallucinations (n = 22). A higher prevalence of parosmia, and as a tendency also phantosmia, was observed in subjects with medium overall brain damage. Further analysis showed a lower frequency of lesions in the right temporal lobe in patients with parosmia than in patients without parosmia. This negative direction of the differences was unique for parosmia. In anosmia, and also in phantosmia, lesions were more frequent in patients displaying the respective symptoms than in those without these dysfunctions. In anosmic patients, lesions in the right olfactory bulb region were much more frequent than in patients with preserved sense of smell, whereas a higher frequency of carriers of lesions in the left frontal lobe was observed for phantosmia. We conclude that anosmia, and phantosmia, are the result of lost function in relevant brain areas whereas parosmia is more complex, requiring damaged and intact brain regions at the same time.

Background: Olfactory dysfunction is deemed to be a significant contributor to poor quality of life in chronic rhinosinusitis (CRS)., Objective: To assess and to compare the effectiveness of three modalities of corticosteroids administration in patients with CRS., Study Design: A prospective randomized controlled study, Methods: Thirty patients with CRS were randomized in three groups depending on the route of corticosteroids administration: 16 days by oral route (Medrol (Pfizer, Belgique), 32 mg/8 days -16 mg/4 days-8 mg/4 days); nasal spray (Rhinocort (AstraZeneca, Belgique), 2 × 2 × 64 µg/nostril); or sonic nebulization (Pulmicort (AstraZeneca, Belgique), 2 × 1 mg/4 mL) (Sonic nebulizer, AOHBOX-NL11SN, DTF, France). Olfactory function was assessed using orthonasal threshold discrimination identification and retronasal psychophysical olfactory tests (RNT) before and after the treatment. Same intranasal modalities were previously tested for in vitro airways scintigraphic deposition., Results: In vitro differences in drug deposition pattern between both intranasal modalities were demonstrated. Threshold discrimination identification and RNT were similar between three groups at baseline. Threshold discrimination identification improved by 5.5, 5.8, and -1.1 for sonic nebulization, oral, and nasal spray groups, respectively (P = 0.010). This improvement was clinically relevant for oral and nebulized administration. It was similar between oral and nebulized administration but significantly higher than nasal spray administration. Retronasal psychophysical olfactory tests improved similarly for the three groups (P = 0.231) CONCLUSION: Effectiveness of sonic nebulized and oral administration is demonstrated on orthonasal olfactory. The clinical benefit is better than with nasal spray., (© 2014 The American Laryngological, Rhinological and Otological Society, Inc.)

Background: Olfactory dysfunction is associated with Alzheimer's disease (AD), and already present at pre-dementia stage., Objectives: Based on the assumption that early neurodegeneration in AD is asymmetrical and that olfactory input is primarily processed in the ipsilateral hemisphere, we assessed whether unirhinal psychophysical and electrophysiological assessment of olfactory function can contribute to the diagnostic workup of mild cognitive impairment (MCI)., Methods: Olfactory function of 13 MCI patients with positive amyloid PET, 13 aged-matched controls (AC) with negative amyloid PET and 13 patients with post-infectious olfactory loss (OD) was assessed unirhinally using (1) psychophysical testing of olfactory detection, discrimination and identification performance and (2) the recording of olfactory event-related brain potentials. Time-frequency analysis was used to enhance the signal-to-noise ratio of the electrophysiological responses. Psychophysical and electrophysiological assessment of auditory and trigeminal chemosensory function served as controls., Results: As compared to AC and OD, MCI patients exhibited a significant asymmetry of olfactory performance. This asymmetry efficiently discriminated between MCI and AC (sensitivity: 85% , specificity: 77% ), as well as MCI and OD (sensitivity: 85% , specificity: 70% ). There was also an asymmetry of the electrophysiological responses, but not specific for MCI. In both MCI and OD, olfactory stimulation of the best nostril elicited significantly more activity than stimulation of the worse nostril, between 3-7.5 Hz and 1.2-2.0 s after stimulus onset. Trigeminal and auditory psychophysical testing did not show any difference between groups., Conclusion: MCI patients exhibit a marked asymmetry of behavioral olfactory function, which could be useful for the diagnostic workup of MCI.

Flavor perception is to a large extent determined by olfaction, and persons who lost their sense of smell consequently complain about strongly reduced enjoyment of food. The retronasal olfactory function is especially important for flavor appreciation. The aim of this study was to compare retronasal function across different cultures and to develop a test that is applicable across cultures. Identification of 39 retronasal applied odor probes was tested in a total of 518 participants of seven countries; 292 of them were healthy, and 226 exhibited a smell disorder. A retest was performed with 224 of the healthy participants. Furthermore, all participants were tested for orthonasal threshold, identification, and discrimination ability. Significant cultural differences in identification ability were found in 92% of the probes. The 20 probes that could be identified above chance in healthy participants of all countries and that could differentiate between patients and controls were selected for the final retronasal test. This test was well able to differentiate between controls and patients in different countries and showed a good coherence with the orthonasal test (r = 0.80) and a good retest-reliability (r = 0.76). Furthermore, it is age-independent. The strong cultural differences observed in retronasal identification underline the necessity to develop a culturally independent instrument. This retronasal test is easy to apply and can be used across different countries for diagnostics and clinical research.

Background: The clinical usefulness of olfactory event-related brain potentials (OERPs) to assess olfactory function is limited by the relatively low signal-to-noise ratio of the responses identified using conventional time-domain averaging. Recently, it was shown that time-frequency analysis of the obtained EEG signals can markedly improve the signal-to-noise ratio of OERPs in healthy controls, because it enhances both phase-locked and non phase-locked EEG responses. The aim of the present study was to investigate the clinical usefulness of this approach and evaluate its feasibility in a clinical setting., Methodology: We retrospectively analysed EEG recordings obtained from 45 patients (15 anosmic, 15 hyposmic and 15 normos- mic). The responses to olfactory stimulation were analysed using conventional time-domain analysis and joint time-frequency analysis. The ability of the two methods to discriminate between anosmic, hyposmic and normosmic patients was assessed using a Receiver Operating Characteristic analysis., Results: The discrimination performance of OERPs identified using conventional time-domain averaging was poor. In contrast, the discrimination performance of the EEG response identified in the time-frequency domain was relatively high. Furthermore, we found a significant correlation between the magnitude of this response and the psychophysical olfactory score., Conclusion: Time-frequency analysis of the EEG responses to olfactory stimulation could be used as an effective and reliable diagnostic tool for the objective clinical evaluation of olfactory function in patients.

Objectives: Several prognostic factors influencing the recovery from olfactory dysfunction have been described. The aim of this study was to investigate whether olfactory bulb volume could be used as a new predictor of olfactory recovery in postinfectious and posttraumatic olfactory loss., Study Design: Cohort study; Level of evidence, 4. Setting Tertiary university clinic, department of otolaryngology., Subjects and Methods: A cohort of 60 patients with postinfectious (n = 28) and posttraumatic olfactory loss (n = 32) was investigated. Assessment of olfactory function was performed using orthonasal (Sniffin' Sticks test) and retronasal psychophysical olfactory tests, at the time of the diagnosis (t1) and 15 months later (t2). All patients were examined on 3 tesla magnetic resonance imaging, and the olfactory bulbs volume was assessed using planimetric contouring at the time of the diagnosis (t1)., Results: Recovery rate was 25% in patients with posttraumatic olfactory loss and 36% in patients with postinfectious olfactory loss. There was a correlation between both orthonasal and retronasal olfactory testing and the initial measurement of the total olfactory bulb volume. In addition, we observed a significant correlation between changes in olfactory functions and initial measurement of the total olfactory bulb volume, with larger volumes relating to higher improvement of olfactory function. Finally, we found that none of the patients with a total olfactory bulb volume of 40 mm(3) or less exhibited recovery of olfactory function., Conclusion: Olfactory bulb volume seems to be a predictor of olfactory recovery in patients with postinfectious and posttraumatic olfactory loss.

Electroencephalographic techniques are widely used to provide an objective evaluation of the chemosensory function and to explore neural mechanisms related to the processing of chemosensory events. The most popular technique to evaluate brain responses to chemosensory stimuli is across trial time-domain averaging to reveal chemosensory event-related potentials (CSERP) embedded within the ongoing EEG. Nevertheless, this technique has a poor signal-to-noise ratio and cancels out stimulus-induced changes in the EEG signal that are not strictly phased-locked to stimulus onset. The fact that consistent CSERP are not systematically identifiable in healthy subjects currently constitutes a major limitation to the use of this technique for the diagnosis of chemosensory dysfunction. In this review, we will review the different techniques related to the recording and identification of CSERP, discuss some of their limitations, and propose some novel signal processing methods which could be used to enhance the signal-to-noise ratio of chemosensory event-related brain responses.

Background: The recording of olfactory and trigeminal chemosensory event-related potentials (ERPs) has been proposed as an objective and non-invasive technique to study the cortical processing of odors in humans. Until now, the responses have been characterized mainly using across-trial averaging in the time domain. Unfortunately, chemosensory ERPs, in particular, olfactory ERPs, exhibit a relatively low signal-to-noise ratio. Hence, although the technique is increasingly used in basic research as well as in clinical practice to evaluate people suffering from olfactory disorders, its current clinical relevance remains very limited. Here, we used a time-frequency analysis based on the wavelet transform to reveal EEG responses that are not strictly phase-locked to onset of the chemosensory stimulus. We hypothesized that this approach would significantly enhance the signal-to-noise ratio of the EEG responses to chemosensory stimulation because, as compared to conventional time-domain averaging, (1) it is less sensitive to temporal jitter and (2) it can reveal non phase-locked EEG responses such as event-related synchronization and desynchronization., Methodology/principal Findings: EEG responses to selective trigeminal and olfactory stimulation were recorded in 11 normosmic subjects. A Morlet wavelet was used to characterize the elicited responses in the time-frequency domain. We found that this approach markedly improved the signal-to-noise ratio of the obtained EEG responses, in particular, following olfactory stimulation. Furthermore, the approach allowed characterizing non phase-locked components that could not be identified using conventional time-domain averaging., Conclusion/significance: By providing a more robust and complete view of how odors are represented in the human brain, our approach could constitute the basis for a robust tool to study olfaction, both for basic research and clinicians.

This paper reviews the contribution of the different parts of the oral cavity and the pharynx to the basic physiology of breathing, phonation, speech, swallowing, and of Waldeyer's ring to the functioning of the immune system. We discuss the development of taste and smell, as well as possibilities for chemosensory testing in children.

Atrophic rhinitis (AR) is a chronic inflammation of the nose characterized by an atrophy of the nasal mucosa. This is typically associated with an impaired sense of smell and a subjective sensation of poor nasal breathing. The aim of this study is to assess chemosensory function in patients suffering from AR using psychophysical testings and event-related potentials (ERP) responses. A cohort of nine patients was extensively studied. Eight out of nine had secondary AR sequela of a bilateral total inferior turbinectomy whereas one patient had a primary AR. All the patients had a clinical evaluation using Sniffin' Sticks test and a retro-olfaction test and an electrophysiological evaluation based upon ERPs obtained after both olfactory and trigeminal stimuli. All the patients complained of a poor nasal breathing and presented a distortion of the chemosensory function. Actually, the orthonasal psychophysical testing showed that four patients out of nine had anosmia, three out of nine had hyposmia and two out of nine were normosmic. All the patients demonstrated retro-olfaction scores inferior to the normal values. The chemosensory ERP showed that seven patients had no olfactory response whereas six had no trigeminal response. Four patients had neither olfactory nor trigeminal ERP response. In conclusion, this study demonstrates that most patients with AR secondary to a total bilateral inferior turbinectomy have a reduction of the chemosensory function measured objectively by psychophysical testings and ERP [corrected].

Adenotonsillar hypertrophy is a common paediatric/otolaryngological disorder that may be associated with secondary growth or facial growth impairment, sleep disturbances, neurocognitive deficits, or smell loss. Surgical removal of the hypertrophic tissue eliminates the mechanical obstacle of the airways and is therefore curative in most cases. The purpose of the present review is to outline the impact of adenotonsillar hypertrophy and adenotonsillectomy on growth, facial growth, sleep, behaviour and smell.

While the effects of early visual deprivation on auditory and tactile functions have been widely studied, little is known about olfactory function in early blind subjects. The present study investigated the potential effect of early blindness on the electrophysiological correlates of passive odour perception. Event-related potentials (ERPs) were recorded in eight early blind humans and eight sighted controls matched for age, sex and handedness during olfactory stimulation with 2-phenyl ethyl alcohol and trigeminal stimulation with CO2 Latencies, amplitudes and topographical distributions were analysed. As expected, the olfactory and trigeminal ERP components showed normal latencies, amplitudes and topography in both groups. Olfactory stimuli generated responses of smaller amplitude than those observed in response to trigeminal stimulation. In addition, ERP analyses did not reveal any major difference in electrocortical responses in occipital areas in early blind and sighted subjects. These results suggest that passive olfactory and trigeminal stimulation elicit the same electrophysiological responses in both groups, confirming that the neurophysiological correlates of the cross-modal compensatory mechanisms in early blind subjects do not appear during passive olfactory and trigeminal perception.

It has been shown that the volume of the olfactory bulb (OB) changes with function. The aim of this study was to investigate whether the OB volume and the olfactory function in early blind (EB) subjects increase compared with controls. Psychophysical testing of olfactory performances and OB volumetric measurements assessed by an MRI scan were studied. Quantitative olfactory function expressed in the odor discrimination and odor-free identification scores was higher in EB subjects compared with controls. The mean of right, left and total OB volume was 65.40, 75.48, and 140.89 mm, respectively for the EB subjects and 54.47, 52.11, and 106.60 mm, respectively for the controls, with these differences being significant. EB subjects have superior olfactory abilities and presented with significantly higher OB volume than the sighted controls. OB plasticity may explain this compensatory mechanism between visual deprivation and enhanced olfactory perception.

Differentiation of progenitor cells into neurons in the olfactory bulb depends on olfactory stimulation that can lead to an increase in olfactory bulb volume. In this study, we investigated whether the human olfactory bulb volume increases with increasing olfactory function due to treatment of chronic rhinosinusitis. Nineteen patients with chronic rhinosinusitis were investigated before and after treatment. For comparison, additional measurements were performed in 18 healthy volunteers. Volumetric measurements of the olfactory bulb were based on planimetric manual contouring of magnetic resonance scans. Olfactory function was evaluated separately for each nostril using tests for odour threshold, odour discrimination and odour identification. Measurements were performed on two occasions, 3 months apart. In healthy controls, the olfactory bulb volume did not change significantly between the two measurements. In contrast, the olfactory bulb volume in patients increased significantly from the initial 64.5 +/- 3.2 to 70.0 +/- 3.5 mm(3) on the left side (P = 0.02) and from 60.9 +/- 3.5 to 72.4 +/- 2.8 mm(3) on the right side (P < 0.001). The increase in olfactory bulb volume correlated significantly with an increase in odour thresholds (r = 0.60, P = 0.006, left side; r = 0.49, P = 0.03, right side), but not with changes in odour discrimination or odour identification. Results of this study support the idea that stimulation of olfactory receptor neurons impacts on the cell death in the olfactory bulb, not only in rodents but also in humans. To our knowledge, this is the first longitudinal study that describes an enlargement of the human olfactory bulb due to improvement of peripheral olfactory function.

The aim of this article is to summarise the anatomy of the chemosensory pathways. The vomeronasal organ, the olfactory system, the trigeminal system and the gustatory system will be reviewed in succession. For each of these systems, we will provide a description of the anatomy of the pathways sending the sensory message from the peripheral receptor to the cortical areas, passing through different relays in the nervous system. Particular emphasis will be paid to the anatomical features of the structures involved in chemosensory perception. This will help us to understand better how these systems interact and influence our social lives, our memories and our behaviour, and to evaluate patients with chemosensory dysfunction better.

Objectives: Post-traumatic olfactory loss (PTOL) is the third most common aetiology for olfactory disorders. Mechanisms that lead to post-traumatic olfactory disorders include sinonasal affections, damage to the olfactory nerve and lesions of the cerebral olfactory centres. The purpose of this review is to present an update of this condition and to present a cohort study of 90 patients., Methodology: A review of the literature was made on Medline Pubmed up to May 2009 and a review was also conducted of patients with post-traumatic olfactory loss., Results: The degree of olfactory impairment was related to the severity of head trauma and was particularly frequent in cases of occipital impact. Typically, patients experienced a sudden onset of olfactory symptoms and were more severely affected than in other aetiologies. Results from orthonasal and retronasal testing, chemosensory event-related potentials and olfactory bulb (OB) volume confirmed previous findings: patients are usually anosmic, OB volume correlates with the degree of olfactory loss (better correlation with retronasal scores than with orthonasal scores) and olfactory event-related potentials were recorded in only 18 patients., Conclusions: Accuracy in the evaluation of PTOL patients is based on the expertise and the time spent by the clinician on defining the complaint. Failing treatment, complete evaluation of the PTOL patients may help in counselling for the recovery prognosis, and appropriate counselling must be given to secure the environment and alimentation.

Numerous techniques are available in the clinic for the investigation of chemosensory function. Psychophysical testing using orthonasal and retronasal stimulation routes may help to distinguish anosmic from hyposmic patients. These psychophysical tests are most frequently used for odour identification and odour threshold. Chemosensory event-related potentials using olfactory and trigeminal stimulation have become part of the routine investigation of patients with olfactory loss in specialised smell and taste centres. The interpretation of results from psychophysical testing is frequently supported by the assessment of chemosensory event-related potentials. This review will discuss these methods, including how to perform them, focusing on normative data and describing some clinical examples from our centre (olfactory and trigeminal event-related potentials).

Background: Lack of an olfactory bulb (OB) is typically associated with anosmia., Methods: We present a patient with subnormal olfactory function in whom the OB could not be detected with magnetic resonance imaging (MRI)., Results: Olfactory function was evaluated on two occasions. Orthonasal olfactory function was assessed with the "Sniffin' Sticks" test providing a score equivalent to hyposmia. Retronasal olfactory function was studied with "smell powders" indicating a decreased, but not absence of, olfactory function. Importantly, chemosensory event-related potentials were clearly present in response to olfactory and trigeminal stimuli., Conclusion: This indicates that olfactory function may be present in some subjects even when an OB can not be detected with MRI.

Objective: To investigate whether differences in olfactory function between healthy individuals and patients with olfactory loss could be detected by various diagnostic tests., Design: Psychophysical testing of orthonasal and retronasal olfactory functions, magnetic resonance imaging of olfactory bulb (OB) volume, and chemosensory event-related potential (ERP) measurement performed between January 1, 2005, and October 31, 2005., Setting: Academic tertiary referral medical center., Patients: Eleven healthy individuals with normal olfactory function (NL) and 11 patients with nasal polyposis (NP), 11 with posttraumatic olfactory loss (PT), and 11 with postinfectious olfactory loss (PI) were included in this study., Main Outcome Measures: Orthonasal and retronasal olfactory test results, magnetic resonance imaging-based OB volume, and ERPs to both olfactory and intranasal trigeminal stimulation., Results: Orthonasal and retronasal testing revealed that NL individuals had higher scores than patients with NP, PT, or PI. Retronasal scores were higher in NP patients compared with PT and PI patients. The OB volumes were higher in NL individuals compared with NP, PT, and PI patients. The OB volumes in PT patients were significantly lower than those from NP and PI patients. Olfactory ERPs were different between NL individuals and NP, PT, and PI patients, and trigeminal ERPs were significantly different when comparing NL individuals with NP patients. For the entire cohort, a significant correlation was found between orthonasal testing and OB volume, between retronasal testing and OB volume, and between both orthonasal and retronasal testing and olfactory ERP amplitudes. Olfactory ERPs were recorded in the 11 NL individuals and in 3 NP, 3 PT, and 4 PI patients, defined as responders. Orthonasal and retronasal test scores, OB volume, and olfactory ERPs were significantly larger in responders compared with nonresponders., Conclusions: Significant differences in various tests that evaluate olfactory function were detectable in a cohort of NL individuals and NP, PT, and PI patients. This finding suggests that these diagnostic tools provide information in terms of the clinical assessment of olfactory function. Future studies will investigate their combined use in terms of the prognosis of olfactory function in patients with olfactory loss.

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.

Objective: The study aimed to investigate whether the degree of postinfectious olfactory loss is reflected in volume of the olfactory bulb (OB)., Study Design: Retrospective study of 26 patients with postinfectious olfactory loss., Materials and Methods: Olfactory function was assessed with the "Sniffin' Sticks" test kit, and the magnetic resonance imaging study focused on OB volume and the olfactory sulcus., Results: The study revealed that 1) OB volume varies with regard to olfactory function, 2) OB volume decreases with duration of olfactory loss, and 3) patients with parosmia had smaller OB volumes than patients who did not report such smell distortions, although their overall olfactory function was not significantly different from each other., Conclusion: The study emphasizes that OB volume is a gauge of olfactory function.

Goals: To give an overview on the theoretical and practical applications of chemosensory event-related potentials., Methods: Chemosensory event-related potentials (ERPs) may be elicited by brief and precisely defined odorous stimuli. Based on the principles of air-dilution olfactometry, a stimulator was developed in the late 1970s, which allows stimulation of the olfactory neuroepithelium and the nasal mucosa with no concomitant mechanical stimulation. Chemosensory ERPs were obtained after stimulation of the olfactory nerve (olfactory ERPs) or the trigeminal nerve (somatosensory or trigeminal ERPs). The characteristics of the stimulator for chemosensory research as well as the variables influencing the responses are discussed in this paper., Results: Implementation and normative data from our department are reported with different clinical examples from otorhinolaryngologic clinic. The bulk of the evoked response consists of a large negative component (often referred to as N1), which occurs between 320 and 450 ms after stimulus onset. This component is followed by a large positive component, often referred to as P2, occurring between 530 and 800 ms after stimulus onset. Absence of olfactory ERPs and presence (even with subtle changes) of somatosensory ERPs is a strong indicator of the presence of an olfactory dysfunction., Conclusions: This review examines and discusses the methods of chemosensory stimulation as well as the electrophysiological correlates elicited by such stimuli. The clinical applications of chemosensory ERPs in neurology and otorhinolaryngology are outlined.

Abstract: Introduction and aim: There is a high prevalence of olfactory dysfunction in the general population. Several causes of olfactory dysfunction have been reported and this disorder is classically divided into sinonasal and non-sinonasal-related olfactory dysfunction. The aims of this study were firstly, to evaluate the frequency of the various aetiologies of olfactory dysfunction in a population of patients with non-sinonasal-related olfactory dysfunction and secondly, to evaluate the degree of olfactory impairment associated with these various aetiologies. Material and methods: We retrospectively reviewed a cohort of 496 patients with non-sinonasal-related olfactory dysfunction. The aetiology of the olfactory dysfunction was recorded for each patient. The aetiology was determined by a complete clinical assessment, including medical history, complete otorhinolaryngological examination, psychophysical testing of olfactory function, recording of olfactory event-related potentials and brain magnetic resonance imaging. Six groups of patients were defined on the basis of the aetiology of the disease and orthonasal and retronasal psychophysical olfactory performances were evaluated in each group. Results: Post-infectious and post-traumatic aetiologies were the most common causes, representing 37.9% and 33.1% of patients, respectively, followed by idiopathic (16.3%), congenital (5.9%), toxic (3.4%) and neurological (3.4%) olfactory dysfunction. Anosmia was significantly more frequent in congenital (93.1%) and post-traumatic (62.8%) olfactory dysfunction, whereas hyposmia was more frequent in the post-infectious group (59.6%). Orthonasal and retronasal olfactory function tests were significantly correlated in all groups except for the congenital group. Conclusions: The data of this study confirm that the most common causes of non-sinonasal-related olfactory dysfunction are post-infectious and post-traumatic. Post-infectious olfactory dysfunction is mainly observed in middle-aged women and is mainly associated with hyposmia, whereas post-traumatic olfactory dysfunction is mainly observed in young men and is associated with a high rate of anosmia. [Copyright &y& Elsevier]