A new non-invasive method for recording the electro-olfactogram using external electrodes

Olfactory dysfunction in chronic rhinosinusitis: insights into the underlying mechanisms and treatments

INTRODUCTION

Olfactory dysfunction (OD) is a typical symptom of chronic rhinosinusitis (CRS), which adversely affects the patient's quality of life and results in mood depression. Studies investigating the impairment of olfactory epithelium (OE) have indicated that inflammation-induced cell damage and dysfunction in OE plays a vital role in the development of OD. Consequently, glucocorticoids and biologics are beneficial in the management of OD in CRS patients. However, the mechanisms underlying OE impairment in CRS patients have not been fully elucidated.

AREAS COVERED

This review focuses on mechanisms underlying inflammation-induced cell impairment in OE of CRS patients. Additionally, the methods used for detection of olfaction and both currently available and potentially new clinical treatments for OD are reviewed.

EXPERT OPINION

Chronic inflammation in OE impairs not only olfactory sensory neurons but also non-neuronal cells that are responsible for regeneration and support for neurons. The current treatment for OD in CRS is mainly aimed at attenuating and preventing inflammation. Strategies for use of combinations of these therapies may achieve greater efficacy in restoration of the damaged OE and consequently better management of OD.

Electrophysiological and olfactometric evaluation of long-term COVID-19

COVID-19 is a public health emergency with cases increasing globally. Its clinical manifestations range from asymptomatic and acute respiratory disease to multiple organ dysfunction syndromes and effects of COVID-19 in the long term. Interestingly, regardless of variant, all COVID-19 share impairment of the sense of smell and taste. We would like to report, as far as we know, the first comprehensive neurophysiological evaluation of the long-term effects of SARS-CoV-2 on the olfactory system with potential-related neurological damage. The case report concerns a military doctor, with a monitored health history, infected in April 2020 by the first wave of the epidemic expansion while on military duty in Codogno (Milan). In this subject, we find the electrophysiological signal in the periphery, while its correlate is absent in the olfactory bulb region than in whole brain recordings. In agreement with this result is the lack of metabolic signs of brain activation under olfactory stimulation. Consequently, quantitative and qualitative diagnoses of anosmia were made by means of olfactometric tests. We strongly suggest a comprehensive series of olfactometric tests from the first sign of COVID-19 and subsequent patient assessments. In conclusion, electrophysiological and metabolic tests of olfactory function have made it possible to study the long-term effects and the establishment of neurological consequences.

Effect of Lidocaine on Olfactory Perception in Humans

Objective:

The effect of local anesthesia to the nasal mucosa on olfactory acuity is the subject of some debate. This study was aimed to investigate the effect of local anesthesia on olfactory perception.

Materials and Methods:

Six healthy participants, five males and one female, were chosen from the academic population of Cardiff University. Olfactory perception was monitored at intervals following administration of 4% lidocaine to the nasal mucosa in the volunteers. Lidocaine was administered using a nasal spray as used in routine otolaryngological investigations. The olfactory stimulus (amyl acetate) was delivered directly to the nostril using an olfactometer. Olfactory perception was determined by the use of a 13 trial, forced choice scoring task.

Results:

Lidocaine caused a small, transient reduction in olfactory perception. The maximum reduction in olfactory perception (35%) was achieved by 60 mg lidocaine 15 min following administration, but perception could be increased to almost normal levels by increasing the odor stimulus dose. Detection of the lowest stimulus strength returned to normal levels after 30 min.

Conclusions:

Intranasal application of lidocaine, caused a reduction in olfactory perception, however, did not abolish the olfactory function 15 min following administration. Physiological/psychometric olfactory testing would not be precluded under these circumstances, and the effects of anesthesia could be overcome by increasing the stimulus strength.

Electrophysiology of Olfactory and Optic Nerve in Outpatient and Intraoperative Settings

Evoked potentials are time-locked electrophysiologic potentials recorded in response to standardized stimuli using scalp electrodes. These responses provide good temporal resolution and have been used in various clinical and intraoperative settings. Olfactory evoked potentials (OEPs) may be used as an adjunct tool in identifying patients of Parkinson disease and Alzheimer dementia. In clinical practice, visual evoked potentials (VEPs) are particularly useful in identifying subclinical cases of optic neuritis and in treatment surveillance. In recent times, pattern electroretinograms and photopic negative response have been gaining attention in identifying glaucoma suspects. During surgical manipulation, there is a risk of damage to optic or olfactory nerve. Intraoperative neurophysiologic monitoring can provide information regarding the integrity of olfactory or visual pathway. OEPs and VEPs, however, show high degree of variability and are not reliable tools because the responses are extremely susceptible to volatile anesthetic agents. Newer techniques that could possibly circumvent these drawbacks have been developed but are not used extensively. In this article, we briefly review the available techniques to obtain OEPs and VEPs, diagnostic applications, the utility of intraoperative monitoring, the limitations of the current techniques, and the future directions for research.

Quantitative instruments used to assess children's sense of smell: a review article

PURPOSE

To systematically gather from the literature available the quantitative instruments used to assess the sense of smell in studies carried out with children.

RESEARCH STRATEGY

The present study included a survey in the Pubmed and Bireme platforms and in the databases of MedLine, Lilacs, regional SciELO and Web of Science, followed by selection and critical analysis of the articles found and chosen.

SELECTION CRITERIA

We selected original articles related to the topic in question, conducted only with children in Portuguese, English, and Spanish. We excluded studies addressing other phases of human development, exclusively or concurrently with the pediatric population; studies on animals; literature review articles; dissertations; book chapters; case study articles; and editorials.

DATA ANALYSIS

A book report protocol was created for this study, including the following information: author, department, year, location, population/sample, age, purpose of the study, methods, and main results.

RESULTS

We found 8,451 articles by typing keywords and identifiers. Out of this total, 5,928 were excluded by the title, 2,366 by the abstract, and 123 after we read the full text. Thus, 34 articles were selected, of which 28 were repeated in the databases, totalizing 6 articles analyzed in this review.

CONCLUSION

We observed a lack of standardization of the quantitative instruments used to assess children's sense of smell, with great variability in the methodology of the tests, which reduces the effectiveness and reliability of the results.

Odorant concentration dependence in electroolfactograms recorded from the human olfactory epithelium

Electroolfactograms (EOGs) are the summated generator potentials of olfactory receptor neurons measured directly from the olfactory epithelium. To validate the sensory origin of the human EOG, we set out to ask whether EOGs measured in humans were odorant concentration dependent. Each of 22 subjects (12 women, mean age = 23.3 yr) was tested with two odorants, either valeric acid and linalool (n = 12) or isovaleric acid and l-carvone (n = 10), each delivered at four concentrations diluted with warm (37 degrees C) and humidified (80%) odorless air. In behavior, increased odorant concentration was associated with increased perceived intensity (all F > 5, all P < 0.001). In EOG, increased odorant concentration was associated with increased area under the EOG curve (all F > 8, all P < 0.001). These findings substantiate EOG as a tool for probing olfactory coding directly at the level of olfactory receptor neurons in humans.

Repetitive olfactory exposure to the biologically significant steroid androstadienone causes a hedonic shift and gender dimorphic changes in olfactory-evoked potentials

The function of a sensory system is to transduce and relay sensory information in a constant and reproducible manner. However, in the olfactory processing of certain steroids this precept of sensory constancy does not appear to apply. Using threshold testing, psychometrics, and electrophysiological techniques, we investigated the effects of a repetitive exposure protocol on the response to androstadienone. Androstadienone is a steroid found in human secretions that has been widely proposed as a candidate for a human pheromone. The detection threshold, hedonic perception, and evoked potential response all changed following repetitive exposure to androstadienone and not to a control odorant, benzaldehyde. Furthermore, the exposure-dependent changes in evoked potentials exhibited a gender dimorphism in which there were changes in the later components of the evoked potentials specific to women. These components have been associated with cognitive and perceptual operations. This 'learning' to smell a compound found in sweat may be related to biological signaling.

Inflammatory Obstruction of the Olfactory Clefts and Olfactory Loss in Humans: A New Syndrome?

The first step in the olfactory perception is the activation by odorants of sensory neurones in the olfactory epithelium. In humans, this sensory epithelium is located at 2 narrow passages, the olfactory clefts, at the upper part of the nasal cavities. Little is known about the physiology of these clefts. We examined, in 34 patients, the impact of obstructed clefts upon detection and postlearning identification of 5 odorants. The location and extension of the obstructions were assessed using endoscopy, CT scans, and MRI. The inflammatory obstruction was usually bilateral, extending anteroposteriorly, and confined to the clefts, with no sign of obstruction or any inflammatory disease in the rest of the nasal cavities and sinuses. When tested with 5 odorants, these patients showed greatly impaired olfaction compared with a group of 73 normosmic subjects. The majority of these 34 patients had sensory deficits equivalent to that found in another group of 41 congenital anosmic patients, where inspection with MRI indicated the lack of olfactory bulbs. This study demonstrates that the olfactory clefts, in human, function as an entity that is different from other regions of the nasal cavity and is the target for local inflammatory events that are apparently not responding to corticoid and antibiotic treatments.

A new method for measuring reaction times for odour detection at iso-intensity: Comparison between an unpleasant and pleasant odour

A psychophysical detection test was developed to measure the reaction time of human subjects to a pleasant and an unpleasant odour. The response latencies to stimulation with a malodour (valeric acid) and pleasant odorant (amyl acetate) were compared over a range of different stimulus strengths. By expressing reaction time as a function of detection rate, the responses to the two odours can be compared at iso-intensity across the concentration range. This is the first study that allows odorants to be compared at the same intensity over a range of concentrations. The malodour valeric acid was detected more rapidly than amyl acetate; at the 50% detection level the reaction time for the detection of amyl acetate was 1.74 s compared 1.36 s for valeric acid (380 ms or 22% faster). Women were significantly faster than men at detecting both the unpleasant (by 18%) and pleasant (by 26%) odour at the 50% detection level and this disparity increased with decreasing stimulus strength. In conclusion, we demonstrate the ability of a new method for the measurement of reaction times to odour detection to discriminate between two different odours - a malodour and a non-malodour.