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Some reports have been recently published on olfactory loss in people with severe COVID-19. It is suggested to take into consideration the recommendations of the American Academy of Otolaryngology and the British Association of Otorhinolaryngology to include olfactory loss as an early clinical symptom of COVID-19 and consider sudden olfactory loss, as a high index of suspicion of SARS-CoV-2 infection. It can be established that the majority of patients with olfactory loss due to COVID-19, present hyposmia and not anosmia. Patients with olfactory loss, who had SARS-CoV-2 infection, should be classified as loss secondary to viral infection.

Alterations in the sense of smell (dysosmia, anosmia, hyposmia) are frequently experienced by patients with chronic kidney disease. However, currently, the aetiology and consequences are poorly understood, with no effective treatments available to address such impairment. In general, the capacity of olfactory perception is affected in patients with chronic kidney disease (even in those who have not undergone dialysis therapy), and whether these alterations improve after dialysis is disputed. Patients in peritoneal dialysis and haemodialysis have the same olfactory perception defects. Kidney transplantation improves olfactory perception, and one important consequence of such impairment is the potential impact on the patient's nutritional status., (Copyright © 2019 Sociedad Española de Nefrología. Published by Elsevier España, S.L.U. All rights reserved.)

Introduction: Hyposmia and substantia nigra hyperechogenicity (SN+) are characteristic markers of Parkinson's disease (PD), although their diagnostic value in isolation may be limited. We evaluated the combined prevalence of both disorders in patients diagnosed with PD and assessed their diagnostic yield compared to a sample with essential tremor (ET) and another group of healthy subjects., Methods: Patients diagnosed with PD and ET and treated in our outpatient clinic were enrolled. Olfaction was assessed using the "Sniffin' Sticks" odour identification test (SS-12) and hyperechogenicity of the substantia nigra (SN+) was assessed by transcranial duplex ultrasound., Results: A total of 98 subjects were analysed, comprising 30 with PD, 21 with ET, and 47 controls. The respective prevalence rates of hyposmia (SS-12 < 8) and SN+ (area > .24cm(2)) were 70% and 83.3% in PD, 33.3% and 9.5% in ET, and 17% and 10.6% in controls. Both markers were present in 63% of patients with PD, none of the patients with ET, and only 2 of the controls., Conclusions: Combined use of substantia nigra sonography and olfactory testing with SS-12, two rapid, safe, and accessible tests, was more specific than each isolated marker for distinguishing patients with PD from patients with ET and control subjects. Since both markers have been described in very early phases of PD, combined use may be helpful in providing early diagnosis of PD., (Copyright © 2013 Sociedad Española de Neurología. Published by Elsevier España, S.L.U. All rights reserved.)

Introduction: The cerebellum has been linked to multiple functions, such as motor control, cognition, memory, and emotional processing. As for its involvement in the sensory systems, the role of the cerebellum in the sense of smell remains unclear. We suggest that sexually naive male rats will present increased neuronal activity in the cerebellar vermis after being stimulated with almond odour or oestrous odour from receptive females., Methods: We compared activity in the cerebellar vermis using Fos immunoreactivity after olfactory stimulation. Stimulation took place during 60 min in a cube-shaped acrylic chamber with a double bottom. Stimuli were clean woodchip bedding, bedding with almond extract, and bedding taken from a cage of receptive females. Male rats were subsequently anaesthetised with intraperitoneal sodium pentobarbital. Cerebellar tissue was fixed with paraformaldehyde for later immunohistochemical analysis., Results: The number of Fos immunoreactive cells in all lobes of the cerebellar vermis was similar between groups stimulated with almond extract and with oestrous odour, and higher than in the clean woodchip group., Conclusions: Stimulation of the main olfactory system (almond) and the accessory system (oestrous odour) increases Fos protein production in the granular layer of the cortex of the cerebellar vermis in naive male rats., (Copyright © 2014 Sociedad Española de Neurología. Published by Elsevier España, S.L.U. All rights reserved.)

This study evaluated the neonatal responsiveness to the odor of amniotic fluid during the first hours of life. Twenty five newborn infants born by C-section at 36-40 weeks of gestation were evaluated with 1; 5 or 25 drops of amniotic fluid at 1 hour, 3.5 hours and 6 hours of life. A five stimuli habituation plan was used and global motor activity was recorded. Mixed-design ANOVAs for repeated measures demonstrated time differences and showed the highest reactivity at 1 hour, a reduction at 3.5 hours and a recovery at 6 hours (p < 0.0000). Maximum response was observed at the beginning, with a subsequent reduction (p < 0.0088). T tests were used to compare mean differences from baseline to the stimulation period. It was observed that one drop was enough to trigger a response, even at 6 hours of life (p = 0.045). Apparently, babies are able to detect minimum amounts of amniotic fluid and habituate the response with repeated exposure during their first hours of life.

Objective: To show the results of a device that generates automated olfactory stimuli suitable for functional magnetic resonance imaging (fMRI) experiments., Material and Methods: Ten normal volunteers, 5 women and 5 men, were studied. The system allows the programming of several sequences, providing the capability to synchronise the onset of odour presentation with acquisition by a trigger signal of the MRI scanner. The olfactometer is a device that allows selection of the odour, the event paradigm, the time of stimuli and the odour concentration. The paradigm used during fMRI scanning consisted of 15-s blocks. The odorant event took 2s with butanol, mint and coffee., Results: We observed olfactory activity in the olfactory bulb, entorhinal cortex (4%), amygdala (2.5%) and temporo-parietal cortex, especially in the areas related to emotional integration., Conclusions: The device has demonstrated its effectiveness in stimulating olfactory areas and its capacity to adapt to fMRI equipment., (Copyright © 2010 Elsevier España, S.L. All rights reserved.)

Background: Olfaction dysfunction is linked to neurodegenerative diseases, therefore the evaluation of this function is becoming important, Aim: To evaluate olfaction in healthy participants., Material and Methods: We evaluated 44 healthy males and 55 females, aged 21 to 89 years with the Sniffing Sticks battery to determine normal values in Chilean population. During the test, participants must correctly identify 12 different odors., Results: Normal olfaction, hyposmia and anosmia were defined. An age related decline in olfaction was observed, especially among males aged 59 years or more., Conclusions: This study provides age and gender specific normal values for the Sniffing Sticks battery.

As discussed in the first part of this review, the development of the olfactory system offers a series of fascinating peculiarities that make it one of the models that has been most widely studied in order to reach an understanding of the mechanisms involved in the development of the nervous system. In the first part we reviewed the different mechanisms based on contact (laminins, cell adhesion molecules, ephrins, etc.) and on secretion (semaphorins, slits, growth factors, etc.) that are involved in the formation of the synaptic connections among the olfactory epithelium, the olfactory bulb and the olfactory cortex. In this second part we will review the molecular mechanisms responsible for the intracortical connections in the main olfactory system, as well as the limited information available concerning the accessory olfactory system. We shall also review the mechanisms involved in the migration of the interneuron precursors from the sub-ventricular area of the forebrain to the olfactory bulb, which is another crucial event in the development of this system.

The physiological particularities that occur during the development of the olfactory system make it one of the most fascinating parts of the central nervous system and one of models that has been most widely studied in order to understand the mechanisms related with axonal growth and guidance towards the right targets. A variety of mechanisms are known, some mediated by contact (laminins, cell adhesion molecules, ephrins, etc.) and others that are secreted (semaphorins, slits, growth factors, etc.), to play diverse roles in establishing the synaptic interactions among the olfactory epithelium, the olfactory bulb and the olfactory cortex. In relation to this, other specific mechanisms for this system have also been proposed, including the incredible family of close to 1000 different olfactory receptors. In recent years, different reviews have focused on the partial elements of this system, especially on the mechanisms involved in the formation of the olfactory nerve. However, no detailed review of those related with the development of the connections between the different olfactory structures (epithelium, bulb and cortex) has been put forward to date. In this first part of the review, we address this topic from the following perspective: the different cellular and molecular mechanisms that guide the formation of the olfactory nerve and the lateral olfactory tract.

The five senses have had a fundamental importance for survival and socialization of human beings. From an evolutionary point of view the sense of smell is the oldest. This sense has a strong representation within the genome, allowing the existence of many types of receptors that allow us to capture multiple volatile odor producing molecules, sending electrical signals to higher centers to report the outside world. Several cortical areas are activated in the brain, which are interconnected to form an extensive and complex neural network, linking for example, areas involved with memory and emotions, thus giving this sense of perceptual richness. While the concept of flavor is largely related to the sense of taste, smell provides the necessary integration with the rest of the senses and higher functions. Fully understanding the sense of smell is relevant to health professionals. Knowing the characteristics of the receptors, the transduction processes and convergence of information in the higher centers involved, we can properly detect olfactory disorders in our patients.

Introduction: The sense of smell, which was once studied because of its biological and evolutionary significance, is today one of the centres of interest in research on normal and pathological ageing. The latest scientific developments point to an inversely proportional relationship between age and olfactory sensitivity. In certain neurodegenerative diseases this sensory decline is one of the first symptoms of the disorder and is correlated with the progression of the disease., Development: In this work we are going to review the scientific knowledge on loss of sense of smell in ageing and in neurodegenerative diseases, with special attention given to Alzheimer's and Parkinson's diseases., Conclusions: A survey of studies that have examined the olfactory deficits in ageing and in some neurodegenerative diseases offers conclusive results about the presence of these impairments in the early stages of these disorders and even among healthy elderly persons. Although a number of causes contribute to these sensory losses in physiological ageing, a common neurological foundation has been proposed for Alzheimer's and Parkinson's diseases. Nevertheless, despite certain initial similarities, the olfactory deficits shown in these disorders seem to be qualitatively different.

Introduction: Different studies on normal and pathological ageing have shown structural and functional impairment by means of psychophysical measures, electrophysiological studies and brain imaging studies. Lower sensory perception from peripheral olfactory structures, together with alterations in the medulla oblongata and cortex, are the most frequent causes of olfactory impairment in ageing., Aim: To outline the most important tests that can be applied in clinical evaluation., Development: The article begins by reviewing concepts involved in olfactory anatomy and physiology and then goes on to describe the different methods of examination and their applicability to medical diagnosis., Conclusions: Incorporating olfactory tests into clinical practice makes it possible to study the presence of sensory and cognitive impairment in greater depth, especially in ageing and in neurodegenerative diseases; this will allow a possible diagnosis to be expanded and completed.

Introduction: Osmophobia is often reported by migraine patients. This study evaluates osmophobia in connection with the diagnosis of episodic migraine with or without aura, chronic migraine and episodic and chronic tension-type headache., Methods: We recruited from our Headache Unit 68 patients (59 female, 9 male; age 37+/-14.7 years), of whom 24 were migraine without aura (MoA), 11 migraine with aura (MA), 10 chronic migraine (CM) and 23 TTH (episodic-TTH). Patients with two or more forms of primary headache were excluded., Results: Among migraine patients, 54% with MoA and 0% with MA, 40 %CM reported osmophobia during the attacks; none of the 23 TTH patients suffered this symptom. The crisis frequency was MoA and osmophobia 2.15 crisis per month; MoA without osmophobia 3,14. MC with osmophobia 22; MC without osmophobia 21.7., Conclusions: Osmophobia and taste abnormalities were demonstrated to be very specific in diagnosing migraine, but very insensitive. Osmophobia frequency does not depend on migraine frequency. Osmophobia seems to be more frequent in females than in males. The lack of osmophobia in MA patients could be explained by a different pathophysiological mechanism between MA and MoA.

Objectives: We study the influence of humidity and its variations on human olfactory threshold for pyridine., Material and Method: Olfactory function was tested on 154 healthy volunteers without rhino-sinusal pathology. Pyridine was used as odorant in four different concentrations investigating the ability to detect the stimulus and the acuity to estimate its intensity. All subjects were exposed to four pre-set concentrations of pyridine and their ability to detect the stimulus and its intensity was assessed. We measured the variations in ambient humidity and evaluated its effects on the results., Results: A total of 154 healthy volunteers between 20 and 60 years old (69 men and 85 women) were tested for different concentrations of pyridine with an ambient humidity variation of 50 % +/- 20 %. The average humidity was 50.74 % with a standard deviation of 4.95 %. We did not find significant differences (P>.05) for mean humidity measures between volunteers who detected the odorant and those who did not. Nor did we find significant differences when estimating intensity., Conclusions: We did not find any effect of ambient humidity variation between 42 % and 67 % on human olfactory sensitivity for pyridine.

By histochemical and immunohistochemical methods we study the effects that has the odorous stimuli privation in the first day after the birth on the activity of the olfactory bulb of the gerbil (Meriones Unguiculatus). This sensory deprivation of stimuli causes drastic reductions in given activities (Tyrosine Hydroxylase) no altering other (DOPA-Decarboxylase). This indicates that the functional ripeness of given enzymatic systems specify of an integrity of their sensorial afferences, while it is not necessary for the normal activity of other enzymes even within the same cell.

A simple examination system for the detection and follow-up of olfactory disorders is described. This model distinguishes levels of detection, variations in the characteristics of smells, recognition of smells, and the number of correct responses. A systematic procedure is described.

The objective evaluation of smell is the least used functional ear, nose and throat exploration. Evoked potentials can be recorded after chemical olfactory stimulation using a method similar to recording cortical auditory evoked potentials. Our results with this technique and peppermint oil as the stimulant were fully satisfactory. In 10 patients with normal smell, a characteristic wave with a long latency was recorded in the absence of auditory and visual stimuli. In contrast, in 10 anosmic patients this characteristic recording was absent. The easy recording technique proposed here can be useful for olfactory assessment of objective disorders, detection of malingers, and medical-legal reports.

An histologic study was performed by light microscopy of the rat nasal cavity. A neuroepithelial lining is found in the backside of the cavity and the medial portion of vomeronasal organ. A respiratory seudostratified epithel with a great deal of submucous glandulae cover the remainder of the cavity.

A smell evolution it is done from two isolation experiences, in a cave by a speologyst in Eastern Pyriness. The investigation verified the smell recovery from a person who is used to living in town with big pollution. This work was done with twenty four fragrant essences, twenty of them were oriented to olfactory nerve exploration and four of them to trigeminal response. These tests were done with each nostril separately.