Causes Of Olfactory Dysfunction Research Articles

Olfactory function in acute traumatic brain injury

ObjectiveTraumatic brain injury (TBI) represents a significant public health problem and is associated with a high rate of mortality and morbidity. Although TBI is amongst the most common causes of olfactory dysfunction the relationship between injury severity and olfactory problems has not yet been investigated with validated and standardized methods in the first days following the TBI. MethodsWe measured olfactory function in 63 patients admitted with TBI within the first 12 days following the trauma by means of the Sniffin’ Sticks identification test (quantitative assessment) and a parosmia questionnaire (qualitative assessment). TBI severity was determined by means of the Glasgow Coma Scale (GCS) and by duration of post-traumatic amnesia (PTA) as measured by the Galveston Orientation and Amnesia Test. ResultsPoor olfactory scores correlated with a longer amnesia period, but not with GCS scores. Further, we observed higher parosmia scores in assault victims than in victims of falls or motor vehicle collisions. ConclusionsWe show that PTA is intimately related to olfactory problems following a TBI. Thus, a thorough evaluation of olfaction is essential in order to detect posttraumatic olfactory dysfunction and to take appropriate actions early on to help the individual deal with this impairment.

Olfaction after Endoscopic Sinus Surgery of Chronic Rhinosinusitis

Objectives: Chronic rhinosinusitis (CRS) is one of the most common causes of olfactory dysfunction. After endoscopic sinus surgery (ESS), olfactory function may improve in most cases, but may not in others. The purpose of this study was to investigate the prognostic factors for olfaction improvement after endoscopic sinus surgery in CRS. Methods: A total of 103 patients (175 nostrils) with CRS who underwent ESS were studied. We performed olfactory function test for all patients using the butanol threshold test (BTT) and Cross Cultural Smell Identification test (CC-SIT) preoperatively and postoperatively. The patients’ subjective symptoms were also recorded using the visual analog scale (VAS) pre- and postoperatively. We also analyzed the duration of disease and preoperative computed tomography by Lund-Mackay score. Results: The improvement of olfactory function after ESS in patients with longer duration of symptoms was not significantly lower than in patients with shorter duration. In multivariable study, anosmics had better improvement than hyposmics in recovery of olfaction. There were significant differences in anterior ethmoid involvement between responder and non-responder group. Conclusions: The improvement of olfaction after ESS mainly depends on the degree of preoperative olfactory function and involvement of anterior ethmoid involvement. Therefore, for the better outcome of ESS especially in olfactory function, early and proper treatment (including ESS) for CRS will be necessary.

Non-sinonasal-related olfactory dysfunction: A cohort of 496 patients

Introduction and aimThere 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 methodsWe 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. ResultsPost-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. ConclusionsThe 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.

The optimal evaluation and management of patients with a gradual onset of olfactory loss

The aim of this review is to provide an overview of the causes of olfactory dysfunction, their evaluation and management, with a main focus on the gradual/progressive loss of smell. As the sense of smell gives us essential information about our environment, its loss can cause nutritional and social problems while threatening an individual's safety. Recent surveys have shown quite a substantial prevalence of hyposmia (one out of four people) and anosmia (one out of 200 people) in a variety of populations. Nasal inflammatory diseases such as allergic rhinitis and predominantly chronic rhinosinusitis account for the major and common causes of gradual/progressive loss of smell. However, they are also among the most successfully treated forms of olfactory dysfunction. The management of gradual/progressive smell deficit must always address its etiological causes. In most cases, a detailed medical history and nasal examination, smell testing, and imaging will help to establish an appropriate diagnosis. In addition to anti-inflammatory therapy, mainly nasal and systemic corticosteroids, recent investigations on smell training suggest that the controlled exposure to selected odors may increase olfactory performance. See the Video Supplementary Digital Content 1 (http://links.lww.com/COOH/A8).

Clinical Diagnosis and Treatment of Olfactory Dysfunction

Olfactory dysfunction is a relatively common disorder that is often under-recognized by both patients and clinicians. It occurs more frequently in older ages and men, and decreases patients' quality of life, as olfactory dysfunction may affect the emotion and memory functions. Three main causes of olfactory dysfunction are sinonasal diseases, upper respiratory viral infection, and head trauma. Olfactory dysfunction is classified quantitatively (hyposmia and anosmia) and qualitatively (parosmia and phantosmia). From a pathophysiological perspective, olfactory dysfunction is also classified by conductive or sensorineural types. All patients with olfactory dysfunction will need a complete history and physical examination to identify any possible or underlying causes and psychophysical olfactory tests are essential to estimate the residual olfactory function, which is the most important prognostic factor. CT or MRI may be adjunctively used in some indicated cases such as head trauma and neurodegenerative disorders. Functional MRI (fMRI) and psychophysiological tests (olfactory event-related potential, OERP) are also used in the research setting. Compared to rapid progress that has occurred in fields of basic science and diagnostic tools for the therapy of other diseases and disorders, treatments for olfactory loss are still in a state of unmet need. In most olfactory dysfunctions, there has been no well-designed randomized controlled study to justify or prove effective treatment modalities. Therefore, with more attention to the problem and further research we can expect breakthroughs in the treatment of smell loss in the near future.

MR Volumetric Study of Piriform-Cortical Amygdala and Orbitofrontal Cortices: The Aging Effect

IntroductionThe piriform cortex and cortical amygdala (PCA) and the orbitofrontal cortex (OFC) are considered olfactory-related brain regions. This study aims to elucidate the normal volumes of PCA and OFC of each age groups (20.0-70.0 year old), and whether the volumes of PCA and OFC decline with increasing age and diminishing olfactory function.MethodsOne hundred and eleven healthy right-handed participants (54 males, 57 females), age 20.0 to 70.0 years were recruited to join this study after excluding all the major causes of olfactory dysfunction. Volumetric measurements of PCA and OFC were performed using consecutive 1-mm thick coronal slices of high-resolution 3-D MRIs. A validated olfactory function test (Sniffin’ Sticks) assessed olfactory function, which measured odor threshold (THD), odor discrimination (DIS), and odor identification (ID) as well as their sum score (TDI).ResultsThe volume of OFC decreased with age and significantly correlated with age-related declines in olfactory function. The volume of OFC showed significant age-group differences, particularly after 40 years old (p < 0.001), while olfactory function decreased significantly after 60 years old (p < 0.001). Similar age-related volumetric changes were not found for PCA (p = 0.772). Additionally, there was significant correlation between OFC and DIS on the Right Side (p = 0.028) and between OFC and TDI on both sides (p < 0.05). There was no similar correlation for PCA.ConclusionsAging can have a great impact on the volume of OFC and olfactory function while it has much smaller effect on the volume of PCA. The result could be useful to establish normal volumes of PCA and OFC of each age group to assess neurological disorders that affect olfactory function.

Assessment of Olfactory Nerve by SPECT-MRI Image with Nasal Thallium-201 Administration in Patients with Olfactory Impairments in Comparison to Healthy Volunteers

PurposeThe aim of this study was to assess whether migration of thallium-201 (201Tl) to the olfactory bulb were reduced in patients with olfactory impairments in comparison to healthy volunteers after nasal administration of 201Tl.Procedures10 healthy volunteers and 21 patients enrolled in the study (19 males and 12 females; 26–71 years old). The causes of olfactory dysfunction in the patients were head trauma (n = 7), upper respiratory tract infection (n = 7), and chronic rhinosinusitis (n = 7). 201TlCl was administered unilaterally to the olfactory cleft, and SPECT-CT was conducted 24 h later. Separate MRI images were merged with the SPECT images. 201Tl olfactory migration was also correlated with the volume of the olfactory bulb determined from MRI images, as well as with odor recognition thresholds measured by using T&T olfactometry.ResultsNasal 201Tl migration to the olfactory bulb was significantly lower in the olfactory-impaired patients than in healthy volunteers. The migration of 201Tl to the olfactory bulb was significantly correlated with odor recognition thresholds obtained with T&T olfactometry and correlated with the volume of the olfactory bulb determined from MRI images when all subjects were included.ConclusionsAssessment of the 201Tl migration to the olfactory bulb was the new method for the evaluation of the olfactory nerve connectivity in patients with impaired olfaction.

Clinical features of olfactory disorders in patients seeking medical consultation

BackgroundOlfactory disorders are common complaints in ENT clinics. We investigated causes and relevant features of olfactory disorders and the need for gustatory testing in patients with olfactory dysfunction.Material/MethodsA total of 140 patients seeking medical consultations were enrolled. All patients were asked about their olfactory disorders in a structured interview of medical history and underwent thorough otolaryngologic examinations and imaging of the head.ResultsCauses of olfactory disorders were classified as: upper respiratory tract infection (URTI), sinonasal diseases (NSD), head trauma, idiopathic, endoscopic sinus surgery, congenital anosmia, and other causes. Each of the various causes of olfactory dysfunction had its own distinct clinical features. Nineteen of 54 patients whose gustation was assessed had gustatory disorders.ConclusionsThe leading causes of olfactory dysfunction were URTI, NSD, head trauma, and idiopathic causes. Gustatory disorders were fairly common in patients with olfactory dysfunction. High priority should be given to complaints of olfactory disorders.

The Correlation between Butanol Threshold Test (BTT) and Cross Cultural Smell Identification Test (CC-SIT) According to Causes of Olfactory Disorders

Background and ObjectivesZZOlfaction is a critical function of our body that allows one to avoid potential dangers in daily living. Although there are numerous subjective and objective tests evaluating the olfactory function, there exist no studies assessing correlations among such tests for various causes of olfactory dysfunction, especially in Korea. Subjects and MethodZZWe collected the olfactory functional test results of 473 subjects who visited our outpatient clinic. We categorized these patients into 5 groups: head trauma, post-upper respiratory infection, chronic sinonasal disease, toxic exposure, and idiopathic. All patients were examined using the Butanol Threshold Test (BTT) and Cross Cultural Smell Identification Test (CC-SIT). The patients’ subjective symptoms were recorded using the Visual Analog Scale (VAS). ResultsZZThe three tests showed significant correlations in different pairs (CC-SIT and BTT; r=0.512, p<0.001, BTT and VAS; r=0.558, p<0.001 and VAS & CC-SIT; r=0.567, p<0.001). Correlation results were lower in patients with olfactory disorders caused by an upper respiratory infection and head trauma than in those with olfactory disorders caused by sinonasal diseases.

Hyposmia and executive dysfunction as predictors of future Parkinson's disease: A prospective study

Olfactory deficits and executive dysfunction are early and common symptoms in Parkinson's disease (PD). Previous studies have shown that hyposmia can be a first sign of PD. The aim of the present study was to determine which of three olfactory tests and two selected tests of executive function would be the best predictor of future PD over a 5 year period. In a cohort of 361 nonparkinsonian, nondemented first-degree relatives of PD patients, in whom alternative causes of olfactory dysfunction were excluded, we measured baseline performance on three olfactory and two executive function tasks. Five years from baseline, clinical neurological evaluation and/or a screening questionnaire, sensitive to the presence of Parkinsonism, were used to detect individuals developing clinical PD. Our results show that in first degree relatives of PD patients worse performance on each of three olfactory processing tasks was associated with an increased risk of developing PD within 5 years, whereas performance on selected tests of executive dysfunction was not associated with an increased risk of developing PD. Interestingly, impaired odor discrimination was the best predictor for future PD.

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.

Treatment with AC Pulsed Electromagnetic Fields Improves Olfactory Function in Parkinson's Disease

Olfactory dysfunction is a common symptom of Parkinson's disease (PD). It may manifest in the early stages of the disease and infrequently may even antedate the onset of motor symptoms. The cause of olfactory dysfunction in PD remains unknown. Pathological changes characteristic of PD (i.e., Lewy bodies) have been demonstrated in the olfactory bulb which contains a large population of dopaminergic neurons involved in olfactory information processing. Since dopaminergic drugs do not affect olfactory threshold in PD patients, it has been suggested that olfactory dysfunction in these patients is not dependent on dopamine deficiency. I present two fully medicated Parkinsonian patients with long standing history of olfactory dysfunction in whom recovery of smell occurred during therapeutic transcranial application of AC pulsed electromagnetic fields (EMFs) in the picotesla flux density. In both patients improvement of smell during administration of EMFs occurred in conjunction with recurrent episodes of yawning. The temporal association between recovery of smell and yawning behavior is remarkable since yawning is mediated by activation of a subpopulation of striatal and limbic postsynaptic dopamine D2 receptors induced by increased synaptic dopamine release. A high density of dopamine D2 receptors is present in the olfactory bulb and tract. Degeneration of olfactory dopaminergic neurons may lead to upregulation (i.e., supersensitivity) of postsynaptic dopamine D2 receptors. Presumably, small amounts of dopamine released into the synapses of the olfactory bulb during magnetic stimulation may cause activation of these supersensitive receptors resulting in enhanced sense of smell. Interestingly, in both patients enhancement of smell perception occurred only during administration of EMFs of 7 Hz frequency implying that the release of dopamine and activation of dopamine D2 receptors in the olfactory bulb was partly frequency dependent. In fact, weak magnetic fields have been found to cause interaction with biological systems only within narrow frequency ranges (i.e., frequency windows) and the existence of such frequency ranges has been explained on the basis of the cyclotron resonance model.