Olfactory dysfunction in patients with Wilson's Disease.

INTRODUCTION: Many neurodegenerative disorders are associated with olfactory dysfunction (OD), but little is known about OD in Wilson's Disease (WD). We evaluated olfactory function in patients with WD. MATERIAL AND METHODS: OD was examined in 68 patients with WD and 70 sex- and age-matched healthy controls using subjective testing with 'Sniffin Sticks'. Threshold discrimination identification (TDI) score and its three components (odour detection threshold, discrimination, and identification) were assessed. RESULTS: Compared to controls, patients with WD had a significantly weaker sense of smell in terms of TDI (p < 0.01), odour discrimination (p < 0.01), and identification (p < 0.01), but not in terms of odour detection threshold (p = 0.27). Patients with predominantly neurological symptoms were characterised by greater OD by TDI (p < 0.01), odour detection threshold (p = 0.01), and discrimination (p = 0.03). The presence of pathological lesions (p = 0.04) in brain magnetic resonance imaging and generalised brain atrophy (p = 0.02) predisposed to worse TDI. In the WD group, weak inverse correlations between age and TDI score (r = -0.27), odour detection threshold (r = -0.3), and discrimination (r = -0.3) were found. Male gender was a risk factor for abnormal TDI in both WD and controls (both p = 0.02). CONCLUSIONS: Patients with WD, particularly older individuals, more frequently had OD than healthy volunteers. Predominantly neurological symptoms, and the presence of typical brain MRI changes, predisposed patients with WD to smell disorders.

Olfactory Dysfunction: Etiology, Diagnosis, and Treatment.

BACKGROUND: Disorders of the sense of smell have received greater attention because of the frequency with which they occur as a symptom of SARS-CoV-2 infection. Olfactory dysfunction can lead to profound reduction in quality of life and may arise from many different causes. METHODS: A selective literature review was conducted with consideration of the current version of the guideline issued by the Association of the Scientific Medical Societies in Germany. RESULTS: The cornerstones of diagnosis are the relevant medical history and psychophysical testing of olfactory function using standardized validated tests. Modern treatment strategies are oriented on the cause of the dysfunction. While treatment of the underlying inflammation takes precedence in patients with sinunasal dysosmia, olfactory training is the primary treatment option for other forms of the disorder. The prognosis is determined not only by the cause of the olfactory dysfunction and the patient's age, but also by the olfactory performance as measured at the time of diagnosis. CONCLUSION: Options for the treatment of olfactory dysfunction are available but limited, depending on the cause. It is therefore important to carry out a detailed diagnostic work-up and keep the patient informed of the expected course and prognosis.

Evaluation of subjective and tested olfactory dysfunction as a screening tool for COVID-19 in children.

INTRODUCTION: Olfactory dysfunction (OD) is an extremely frequent symptom of SARS-CoV-2 infection in adults. However, the symptomatology in the paediatric population remains understudied and heavily reliant on questionnaires. The aims of this study were to evaluate the prevalence of OD in children with SARS-CoV-2 infection and to assess the use of olfactory testing in predicting COVID-19 in children. Furthermore, we aimed to investigate the correlation between subjective and objective sense of smell in children. METHODS: Children aged 6-12 years presenting at Test Centre Aarhus for a reverse transcription PCR for SARS-CoV-2 were invited to participate during the study period (from 8 January to 22 February 2022). They underwent olfactory testing with Sniffin' Sticks 16 Identification Kit and they were asked about their subjective assessment of smell and any confounding factors. RESULTS: A total of 78 children completed inclusion of whom 51 had a positive SARS-CoV-2 PCR test. We found no correlation between either current SARS-CoV-2 status and Sniffin' Sticks Identification score (p = 0.500) or previous self-reported infection. We also found no correlation between subjective and objective sense of smell (p = 0. 109). CONCLUSION: The lack of correlation between SARS-CoV-2 infection and OD may indicate that OD is not a dominant symptom in children. Therefore, olfactory testing is not recommended as a screening method for SARS-CoV-2 as was suggested in adults. Likewise, subjective questioning is not a reliable tool in assessing olfactory function in children. FUNDING: Laura Danielsen received funding for salary from Forskningsfond Hospitalsenheden Vest (now Forskningsfond Regionshospitalet Gødstrup). Alexander Wieck Fjældstad wishes to acknowledge research salary funding for other projects from Velux Fonden. The sponsors had no say, roles or responsibilities in relation to the study, including (but not limited to) the study design, data collection, management, analysis or decision to publish. TRIAL REGISTRATION: Not relevant.

Diode laser in management of loss of taste sensation in patients with post-COVID syndrome: a randomized clinical trial.

OBJECTIVE: Loss of taste (ageusia) is a symptom observed following recovery from COVID-19 infection. The loss of taste and smell sensation may negatively affect patients' quality of life (QoL). The present study aimed to evaluate the effectiveness of the Diode Laser in managing loss of taste sensation in patients with post-COVID syndrome versus the placebo. MATERIAL AND METHOD: The study sample was 36 patients who complained of persistent loss of taste sensation following COVID-19. The patients were randomly assigned to one of the two groups according to the received treatment: Group I (laser treatment) and Group II (light treatment), with each patient receiving a diode laser treatment or placebo from the same operator. Taste sensation was subjectively measured after treatment for four weeks. RESULTS: The results demonstrated a significant difference between both groups regarding taste restoration after one month (p = 0.041), with Group II having a significantly higher percentage of cases 7 (38.9%) with partial taste restoration. In contrast, a significantly higher proportion of Group I 17 cases (94.4%) had complete taste restoration (p < 0.001). CONCLUSION: The present study concluded that using a Diode laser 810 nm aided in a more rapid recovery from loss of taste dysfunction.

Olfactory dysfunction in COVID-19: a marker of good prognosis?

INTRODUCTION: In May 2020, the World Health Organization recognized olfactory dysfunction as a COVID-19 symptom. The presence of hyposmia/anosmia may be a marker of good prognosis in COVID-19. OBJECTIVE: To associate the presence of olfaction disorder to the clinical condition severity in patients with COVID-19. METHODS: Individuals with the flu syndrome caused by SARS-CoV-2, diagnosed from March to June 2020, were recruited. They were divided into three groups: mild flu syndrome, severe flu syndrome (admitted to hospital wards) and critical illness (admitted to the ICU). Inpatients were interviewed by telephone contact after hospital discharge and their medical records were also evaluated regarding complementary test results. Outpatients answered an electronic questionnaire containing only clinical information. RESULTS: A total of 261 patients participated in the study: 23.75% with mild flu syndrome, 57.85% with severe flu syndrome and 18.40% with critical illness. A total of 66.28% patients with COVID-19 had olfaction disorders. In approximately 56.58% of the individuals the smell alterations lasted between 9 days and 2 months. There was a significantly higher proportion of individuals with olfactory dysfunction in the group with mild flu syndrome than in the severe flu syndrome group (mild × severe - p < 0.001; Odds Ratio = 4.63; 95% CI [1.87-10.86]). This relationship was also maintained between patients with mild flu syndrome and critically-ill patients (mild × critical - p <  0.001; Odds Ratio = 9.28; 95% CI [3.52-25.53]). CONCLUSION: Olfaction dysfunction was significantly more prevalent in patients with mild flu syndrome in COVID-19. It may be a predictor of a good prognosis for this infection. New population-based studies must be carried out to corroborate these findings.

Olfactory-related quality of life impacts psychological distress in people with COVID-19: The affective implications of olfactory dysfunctions.

BACKGROUND: Coronavirus disease 2019 (COVID-19) often causes chemosensory impairment, and olfactory dysfunctions may have negative consequences on psychological distress. This study aimed at assessing which dimension of perceived olfactory disfunctions (i.e., subjective olfactory capability, smell-related problems, or olfactory-related quality of life [QoL]) was most associated with psychological distress in people diagnosed with COVID-19. METHODS: 364 participants (65 men and 299 women) diagnosed with COVID-19 on average 7 months prior to the beginning of the study were recruited between June 5 and 21, 2021, to take part in an online cross-sectional survey. Participants answered questions on demographics, clinical factors, perceived olfactory functioning, and psychological distress. Hierarchical multiple linear regression analysis was conducted, assessing the role of demographics, clinical factors, and perceived olfactory functioning dimensions on psychological distress. RESULTS: More than half of the participants met the cut-off for all perceived olfactory dysfunctions scales and psychological distress. Being women, smoker, with comorbidities, and greater severity of COVID-19 symptoms were associated with higher scores on psychological distress. Among perceived olfactory functioning scales, only impairment in olfaction QoL was associated with psychological distress. LIMITATIONS: Limitations concerned the cross-sectional nature of the study and the unbalanced sample in terms of gender. CONCLUSIONS: The study confirmed the core intertwining between mood, perceived QoL, and olfactory functioning, showing how impairments in olfactory processing are strongly correlated with psychological distress through the impact they have on the perceived QoL.

[Olfaction and respiratory viruses A relationship revealed by Covid-19]. / Odorat et virus respiratoires :une relation révélée par la Covid-19.

The sense of smell has been underestimated for a long time in humans. It has been brought to the fore by its sudden disappearance during the Covid-19 pandemic of which anosmia (complete loss of smell) is one of the major symptoms. However, respiratory viruses have long been associated with smell disorders, 25% of which are linked to a viral infection. Olfaction begins in the nose within the olfactory epithelium which has the particularity of containing neurons in direct contact with the environment. Several respiratory viruses are known for their replicative capacity within this epithelium. This is particularly the case for the flu virus (influenza) and bronchiolitis (respiratory syncytial virus) but their tropism for this tissue is much lower than SARS-CoV-2. The understanding of the SARS-CoV-2 pathophysiology in the nasal cavity makes it possible to reveal part of the links between viral infection and olfactory disorders.

Title: Odorat et virus respiratoires :une relation révélée par la Covid-19. Abstract: L'odorat, sens pendant longtemps sous-estimé chez l'homme, a été mis sur le devant de la scène par sa soudaine disparition, survenue pendant la pandémie de Covid-19, dont l'anosmie est un des symptômes majeurs. Pourtant, depuis longtemps, les virus respiratoires ont été associés aux troubles de l'odorat, dont 25 % seraient liés à une infection virale. L'olfaction débute dans le nez, au sein d'un épithélium olfactif qui a la particularité de contenir des neurones en contact direct avec l'environnement. Plusieurs virus respiratoires sont connus pour leur capacité réplicative au sein de cet épithélium. C'est notamment le cas du virus de la grippe (influenza) et du virus de la bronchiolite (VRS, pour virus respiratoire syncytial), mais leur tropisme pour ce tissu est bien moindre que celui du SARS-CoV-2. La physiopathologie de ce virus dans la cavité nasale a permis de commencer à comprendre les liens existant entre une infection virale et les troubles de l'olfaction.

Effectiveness and safety of PRP on persistent olfactory dysfunction related to COVID-19.

INTRODUCTION: Olfactory dysfunction (OD) is a well know symptom of coronavirus disease 2019 (COVID-19), accounting for 48 to 85% of patients. In 1 to 10% of cases, patients develop a chronic olfactory dysfunction (COD), lasting more than 6 months. Recently, platelet-rich plasma (PRP) was used in patients with non-COVID-19 COD and authors reported encouraging results. METHODS: In the present study, we investigated the usefulness and safety of PRP injection in 56 patients with COVID-19 COD by the Sniffing Stick test (TDI score) and a linker-scale from 0 (none) to 3 (strong) and we compare the result to a control group. RESULTS: At 1 month post-PRP injection, the mean TDI scores significantly improved by 6.7 points in the PRP group (p < 0,001), the mean self-assessment of improvement in smell function was 1.8 (mild-to-moderate) in the PRP group, which was significantly higher than the score (0.3) in the control group (p < 0,001). CONCLUSION: Our results showed that PRP in the olfactory cleft can increase the olfactory threshold 1 month after the injection. Moreover, our results suggest that timing of treatment may be an important factor and that PRP is a safe treatment, because no adverse effects were reported throughout the study. TRIAL REGISTRATION NUMBER: NCT05226546.

Antibody response, associated symptoms and profile of patients presumably infected by SARS-CoV-2 with taste or smell disorders in the SAPRIS multicohort study.

BACKGROUND: Taste or smell disorders have been reported as strongly associated with COVID-19 diagnosis. We aimed to identify subject characteristics, symptom associations, and antibody response intensity associated with taste or smell disorders. METHODS: We used data from SAPRIS, a study based on a consortium of five prospective cohorts gathering 279,478 participants in the French general population. In the analysis, we selected participants who were presumably infected by SARS-CoV-2 during the first epidemic wave. RESULTS: The analysis included 3,439 patients with a positive ELISA-Spike. Sex (OR = 1.28 [95% CI 1.05-1.58] for women), smoking (OR = 1.54 [95% CI 1.13-2.07]), consumption of more than 2 drinks of alcohol a day (OR = 1.37 [95% CI 1.06-1.76]) were associated with a higher probability of taste or smell disorders. The relationship between age and taste or smell disorders was non-linear. Serological titers were associated with taste or smell disorders: OR = 1.31 [95% CI 1.26-1.36], OR = 1.37 [95% CI 1.33-1.42] and OR = 1.34 [95% CI 1.29-1.39] for ELISA-Spike, ELISA-Nucleocapsid and seroneutralization, respectively. Among participants with taste or smell disorders, 90% reported a wide variety of other symptoms whereas 10% reported no other symptom or only rhinorrhea. CONCLUSIONS: Among patients with a positive ELISA-Spike test, women, smokers and people drinking more than 2 drinks a day were more likely to develop taste or smell disorders. This symptom was strongly associated with an antibody response. The overwhelming majority of patients with taste or smell disorders experienced a wide variety of symptoms.

Diffusion-weighted imaging measurements of central smell regions in COVID-19 patients: insular gyrus, corpus amygdala, and thalamus.

OBJECTIVE: The aim of this study was to investigate central smell centers with cranial magnetic resonance imaging (MRI) diffusion-weighted imaging (DWI) in COVID-19. PATIENTS AND METHODS: This retrospective study evaluated cranial MRI images of 54 adults. The experimental group (Group 1), consisting of 27 patients with positive COVID-19 real-time polymerase chain reaction (RT-PCR) assays, was compared to the control group (Group 2), comprising 27  healthy controls without COVID-19. The apparent diffusion coefficient (ADC) values were measured in the corpus amygdala, thalamus, and insular gyrus in both groups. RESULTS: Thalamus ADC values of the COVID-19 group were significantly lower compared to the control group bilaterally. However, no differences were found in the insular gyrus and corpus amygdala ADC values between the two groups. Positive correlations were observed between the insular gyrus and corpus amygdala ADC values and the thalamus ADC values. Insular gyrus ADC values (right) were higher in females. Left insular gyrus and corpus amygdala ADC values were higher in COVID-19 patients with smell loss. Right insular gyrus and left corpus amygdala ADC values were lower in COVID-19 patients with lymphopenia. CONCLUSIONS: Diffusion restriction in olfactory areas can be considered an obvious indicator that the COVID-19 virus affects and damages the immune system at the neuronal level. Given the urgency and lethality of the current pandemic, acute onset odor loss should be considered a high suspicion-adhesive index for patients with SARS-CoV-2 infection. Therefore, the sense of smell should be considered and evaluated simultaneously with other neurological symptoms. DWI should be widely used as an early imaging method for central nervous system (CNS) infections, especially in relation to COVID-19.

Smell and taste of milk during tube feeding of preterm infants: neurodevelopmental follow-up of the randomized TASTE trial, study protocol.

BACKGROUND: The Taste And Smell To Enhance nutrition (TASTE) trial investigated the effects of smell and taste of milk with tube feeding compared to routine care on the growth of preterm infants. There was no difference between groups in growth (weight, head circumference, length) z-scores at discharge from the hospital. Infants in the intervention group had higher head circumference and length z-scores at 36 weeks postmenstrual age, both secondary outcomes. The objective of this follow-up study is to assess 2-year neurodevelopmental and growth outcomes after exposure of preterm infants to the smell and taste of milk with tube feeding compared to routine care. METHODS: This is a neurodevelopmental follow-up study of a two-center, placebo-controlled randomized trial. Infants born before 29 weeks postmenstrual age and/or with a birth weight of less than 1250 g were randomized to smell and taste of milk with each tube feed or routine care. The current follow-up assessed the 2-year neurodevelopmental and growth outcomes of participants of the TASTE trial discharged from the hospital (n = 334). The primary outcome is survival free of any major neurodevelopmental impairment comprising any moderate/severe cerebral palsy (Gross Motor Function Classification System score II-V), Bayley Scales of Infant and Toddler Development, Third/Fourth Edition (Bayley-III/Bayley-4) motor, cognitive, or language scores < -2SD, blindness, or deafness at 2 years of age. Other outcomes include death, breastfeeding within the first year, and respiratory support, oral feeding, and anthropometric parameters at 2 years of age. The Human Research Ethics Committees of Mater Misericordiae Limited and the Royal Women's Hospital approved the TASTE trial including the neurodevelopmental follow-up described in this protocol. DISCUSSION: For patients and their families, the neurodevelopmental outcomes of preterm infants are of utmost importance. Consequently, they should be investigated following any interventional study performed during the newborn period. Furthermore, improved weight gain and head growth in the hospital are associated with better long-term neurodevelopmental outcomes. Smelling and tasting of milk is an uncomplicated and cost-effective intervention that may improve the growth and neurodevelopmental outcomes of preterm infants. Potential limitations affecting this follow-up study, caused by the COVID-19 pandemic, are anticipated and discussed in this protocol. TRIAL REGISTRATION: Name of the registry: Australian and New Zealand Clinical Trials Registry; Registration number: ACTRN12617000583347 ; Registration date: 26 April 2017.

Quantitative but not qualitative flavor recognition impairments in COVID-19 patients.

BACKGROUND: Smell and taste dysfunctions (STDs) are symptoms associated with COVID-19 syndrome, even if their incidence is still uncertain and variable. AIMS: In this study, the effects of SARS-CoV-2 infection on chemosensory function have been investigated using both a self-reporting questionnaire on smell and flavor perception, and a simplified flavor test. METHODS: A total of 111 subjects (19 hospitalized [HOS] and 37 home-isolated [HI] COVID-19 patients, and 55 healthy controls [CTRL]) were enrolled in the study. They received a self-evaluation questionnaire and a self-administered flavor test kit. The flavor test used consists in the self-administration of four solutions with a pure olfactory stimulus (coffee), a mixed olfactory-trigeminal stimulus (peppermint), and a complex chemical mixture (banana). RESULTS: After SARS-CoV-2 infection, HOS and HI patients reported similar prevalence of STDs, with a significant reduction of both smell and flavor self-estimated perception. The aromas of the flavor test were recognized by HI and HOS COVID-19 patients similarly to CTRL; however, the intensity of the perceived aromas was significantly lower in patients compared to controls. CONCLUSION: Data reported here suggests that a chemosensory impairment is present after SARS-CoV-2 infection, and the modified "flavor test" could be a novel self-administering objective screening test to assess STDs in COVID-19 patients. CLINICAL TRIAL REGISTRATION NO: NCT04840966; April 12, 2021, retrospectively registered.

Recovery from Covid-19 smell loss: Two-years of follow up.

OBJECTIVE: To report long-term patterns of recovery and non-recovery in a large nationwide cohort of subjects with COVID-19 associated smell loss. STUDY DESIGN: Prospectively, longitudinal questionnaires. SETTING: Web-based national survey. METHODS: A longitudinal survey of adults with COVID-19 and/or sudden change in smell or taste since January 1, 2020 was launched April 10, 2020. Participants were queried again in late May 2022 regarding recovery. Data from respondents with >2 years since loss were analyzed and compared to recovery status of those more recently effected. RESULTS: 1103 responded to the survey of whom 946 met inclusion criteria. Among the 267 respondents for whom at least 2 years of follow up was available, 38.2 % reported full recovery, 54.3 % partial, and 7.5 % no recovery. For the entire cohort (all with ≥3 months since smell loss), 38.7 % reported complete recovery, 51.0 % reported partial recovery (ranging from mild complaints to severe phantosmia or dysosmia), and 10.3 % reported no improvement at all. Complete recovery of smell function was significantly higher in those under 40 years old (45.6 % compared to 32.9 % in those over 40). CONCLUSION: Although the vast majority of subjects who do recover do so within the first 3 months, long-term spontaneous recovery can occur. Rates of recovery do not seem to differ depending on when during the pandemic the loss first occurred.

[Parosmia and phantosmia: clinical update]. / Parosmie et fantosmie: mise à jour.

Olfactory disorders became known by large parts of the population since the Covid-19 pandemic. The causes of olfactory dysfunctions are manifold. Similar to other sensory impairments the disruption can be qualitative or quantitative. Quantitative olfactory disorders such as anosmia or hyposmia are well explored, whereas the knowledge on qualitative disorders such as parosmia or phantosmia is still limited. This article gives an update on the current clinical knowledge and workup of parosmia and phantosmia.

Depuis la pandémie de Covid-19, la population est davantage informée sur les troubles de l'odorat. Ils peuvent être d'origines multiples. Comme pour toute modalité sensorielle, il existe des atteintes quantitatives et qualitatives. Les troubles quantitatifs sont mieux connus et pris en charge mais les troubles qualitatifs restent méconnus. Cet article traite des troubles de l'odorat qualitatifs, notamment de la parosmie et de la fantosmie, ainsi que de leur prise en charge.

Natural trajectory of recovery of COVID-19 associated olfactory loss.

IMPORTANCE: Prevalence of post-viral olfactory loss has increased dramatically due to the frequency and severity of olfactory dysfunction associated with infection by the SARS-CoV-2 virus. OBJECTIVE: To determine the trajectory of COVID-19 olfactory loss over a six-month period. A key secondary objective is to assess predictive factors associated with the recovery of olfaction. DESIGN: Longitudinal repeated-measures study that enrolled from May 5, 2020 to February 2, 2021, with the last date of data collection on June 15, 2021. SETTING: Barnes-Jewish HealthCare/Washington University School of Medicine facilities (Saint Louis, Missouri, USA). PARTICIPANTS: Individuals who tested positive for SARS-CoV-2 by real-time polymerase chain reaction on nasopharyngeal swab and indicated olfactory loss on COVID-19 screening questionnaire. Individuals were excluded if they had previously diagnosed history of olfactory loss, neurodegenerative disorders, <18 years of age, admitted to hospital service, unable to read, write, and understand English, or lacked computer or internet access. INTERVENTIONS/EXPOSURES: Watch and wait for spontaneous recovery. MAIN OUTCOME(S) AND MEASURE(S): Participants completed olfactory assessments every 30 days for six months. Each assessment consisted of the University of Pennsylvania Smell Identification Test (UPSIT), an objective "scratch-and-sniff" test, and Clinical Global Impressions (CGI), a subjective Likert rating scale. RESULTS: The mean age was 41 years old (SD = 16). 39 (80 %) were female and 42 (86 %) white. At baseline assessment of objective olfaction, 18 (36 %) participants had anosmia or severe hyposmia. Subjective, complete recovery at six months was 81 % (95 % CI 74 % to 88 %). Likelihood of recovery was associated with age <50 years (aHR = 8.1 (95 % CI 1.1 to 64.1)) and mild olfactory loss at baseline (UPSIT = 30-33 for males and 31-34 for females) (aHR 6.2 (95 % CI 1.2 to 33.0)). CONCLUSIONS AND RELEVANCE: The trajectory of olfactory recovery among adults with COVID-19 olfactory loss illustrated rapid recovery within 2-3 weeks of infection, and by six months 81 % had recovered based on self-report. Age <50 years old and mild severity of olfactory loss at baseline were associated with increased likelihood of recovery of olfaction. These findings can be used to inform shared decision-making with patients.

Solitary Anosmia/Ageusia in Prison: Results From a COVID-19 Cluster.

A prison setting with its congregate environment is at high risk for widespread transmission of respiratory illnesses. Identifying COVID-19 cases as early as possible and isolating cases and tracing contacts is critical to halting the spread of this disease. The Centers for Disease Control and Prevention (CDC) added new loss of taste or smell to its list of symptoms and, initially, only if associated with at least one of six other symptoms. The CDC has since updated the guidance to remove this qualifier as of May 13, 2020. New loss of taste or smell, alone, can help to identify COVID-19 cases. Solitary anosmia/ageusia should be strongly considered in routine symptom screening protocols for COVID-19.

[Mechanisms and Management of COVID-19-Associated Taste Disorders].

The taste buds in the human tongue contain specialized cells that generate taste signals when they are stimulated. These signals are then transmitted to the central nervous system, allowing the human body to distinguish nutritious substances from toxic or harmful ones. This process is critical to the survival of humans and other mammals. A number of studies have shown that dysgeusia, or taste disorder, is a common complication of coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, which can severely affect patients' nutritional intake and quality of life. Based on the physiological process of taste perception, the direct causes of dysgeusia include dysfunction of taste receptors and damage to the taste nervous system, while indirect causes include genetic factors, aging-related changes, bacterial and viral infections, and cancer treatments such as radiotherapy and chemotherapy. The pathogenic factors of dysgeusia are complicated, further research is needed to fully understand the underlying mechanisms, and some of the reported findings and conclusions still need further validation. All these form a great challenge for clinical diagnosis of the cause and targeted treatment of dysgeusia. Herein, we reviewed published research on the physiological process of taste perception, the potential mechanisms of taste disorders related to SARS-CoV-2 infection, and strategies for prevention and treatment, providing theoretical support for establishing and improving the comprehensive management of COVID-19 complicated by taste disorders.

Structural brain changes in post-acute COVID-19 patients with persistent olfactory dysfunction.

OBJECTIVE: This research aims to study structural brain changes in patients with persistent olfactory dysfunctions after coronavirus disease 2019 (COVID-19). METHODS: COVID-19 patients were evaluated using T1-weighted and diffusion tensor imaging (DTI) on a 3T MRI scanner, 9.94 ± 3.83 months after COVID-19 diagnosis. Gray matter (GM) voxel-based morphometry was performed using FSL-VBM. Voxelwise statistical analysis of the fractional anisotropy, mean diffusivity (MD), radial diffusivity (RD), and axial diffusivity was carried out with the tract-based spatial statistics in the olfactory system. The smell identification test (UPSIT) was used to classify patients as normal olfaction or olfactory dysfunction groups. Intergroup comparisons between GM and DTI measures were computed, as well as correlations with the UPSIT scores. RESULTS: Forty-eight COVID-19 patients were included in the study. Twenty-three were classified as olfactory dysfunction, and 25 as normal olfaction. The olfactory dysfunction group had lower GM volume in a cluster involving the left amygdala, insular cortex, parahippocampal gyrus, frontal superior and inferior orbital gyri, gyrus rectus, olfactory cortex, caudate, and putamen. This group also showed higher MD values in the genu of the corpus callosum, the orbitofrontal area, the anterior thalamic radiation, and the forceps minor; and higher RD values in the anterior corona radiata, the genu of the corpus callosum, and uncinate fasciculus compared with the normal olfaction group. The UPSIT scores for the whole sample were negatively associated with both MD and RD values (p-value ≤0.05 FWE-corrected). INTERPRETATION: There is decreased GM volume and increased MD in olfactory-related regions explaining prolonged olfactory deficits in post-acute COVID-19 patients.

Olfactory training in long COVID-19 patients with lasting symptoms including olfactory dysfunction.

INTRODUCTION: Two-thirds of patients with COVID-19 developed smell and taste dysfunction, of whom half experienced improvement within the first month. After six months, 5-15% still suffered from significant olfactory dysfunction (OD). Before COVID-19, olfactory training (OT) was proved to be effective in patients with post-infectious OD. Therefore, the present study aimed to investigate the progress of olfactory recovery with and without OT in patients with long COVID-19. METHODS: Consecutive patients with long COVID-19 referred to the Flavour Clinic at Gødstrup Regional Hospital, Denmark, were enrolled. The diagnostic set-up at the first visit and follow-up included smell and taste tests, questionnaires, ENT examination and instructions in OT. RESULTS: From January 2021 to April 2022, 52 patients were included due to long COVID-19-related OD. The majority of patients complained of distorted sensory quality, in particular, parosmia. Two-thirds of the patients reported a subjective improvement of their sense of smell and taste along with a significant decline in the negative impact on quality of life (p = 0.0001). Retesting at follow-up demonstrated a significant increase in smell scores (p = 0.023) where a minimal clinically important difference (MCID) in smell scores was found in 23% of patients. Full training compliance was significantly associated with the probability of MCID improvement (OR = 8.13; p = 0.04). CONCLUSIONS: The average effect of OT is modest; however, full training compliance was significantly associated with an increased probability of a clinically relevant olfactory improvement. FUNDING: none. TRIAL REGISTRATION: not relevant.