Olfactory Bulb Volume Research Articles

Seven-tesla magnetic resonance imaging of the nervus terminalis, olfactory tracts, and olfactory bulbs in COVID-19 patients with anosmia and hypogeusia.

Linking olfactory epithelium to the central nervous system are cranial nerve 1, the olfactory nerve, and cranial nerve "0," and the nervus terminalis (NT). Since there is minimal expression of angiotensin-converting enzyme-2 (ACE-2) in the olfactory nerve, it is unclear how SARS-CoV-2 causes anosmia (loss of smell) and hypogeusia (reduction of taste). In animal models, NT expresses ACE-2 receptors, suggesting a possible SARS-CoV-2 viral entry site in humans. The purpose of this study was to determine whether ultra-high-field 7 T magnetic resonance imaging (MRI) could visualize the NT, olfactory bulbs (OB), and olfactory tract (OT) in healthy controls and COVID-19 anosmia or hypogeusia and to qualitatively assess for volume loss and T2 alterations. In this study, 7 T MRI was used to evaluate the brain and olfactory regions in 45 COVID-19 patients and 29 healthy controls. Neuroimaging was qualitatively assessed by four board-certified neuroradiologists who were blinded to outcome assignments: for the presence or absence of NT; for OB, OT, and brain volume loss; and altered T2 signal, white matter T2 hyperintensities, microhemorrhages, enlarged perivascular spaces, and brainstem involvement. NT was identifiable in all COVID-19 patients and controls. T2 hyperintensity in the NT, OB, and OT in COVID-19 patients with anosmia or hypogeusia was statistically significant compared to controls and COVID-19 patients without anosmia or hypogeusia. On 7 T MRI, NT was radiographically identifiable, adjacent to OB and OT. In COVID-19 anosmia and hypogeusia, T2 hyperintensity of NT, OB, and OT was statistically significant compared to COVID-19 patients without anosmia or hypogeusia and controls. The NT may be a potential entry site for SARs-CoV-2 and may play a role in the pathophysiology of COVID-19 anosmia.

Olfactory Bulb Volume and Asymmetry as Predictors of Executive Dysfunction in Adolescents with Congenital Heart Disease.

Common sequelae for patients with congenital heart disease (CHD) are neurodevelopmental disabilities including executive function, attention, and socio-emotional deficits. Although these are common diagnoses for patients with CHD, limited research has investigated the mechanistic underpinnings of these findings. Our previous research examined the association between abnormal respiratory ciliary motion and brain abnormalities in infants with CHD. Results suggested that abnormal ciliary motion correlated to a spectrum of subtle dysplasia, notably within the olfactory bulb (OB)1. Our current study investigates whether OB anomalies predict neurodevelopmental outcomes for pediatric patients with CHD. We hypothesize that adolescents with CHD who exhibit aberrant morphological measurements in the OB are more likely to suffer from executive functional deficits. A prospective, observational study of 54 CHD and 75 healthy subjects, ages 6-25 years old, was completed under the supervision of a senior pediatric neuroradiologist. T2 3D Space and T2 Blade 2MM MRI images were manually segmented to extract volumetric bilateral regions of the OB and cerebrospinal fluid (CSF) using ITK-SNAP. Imaging metrics were correlated to OB asymmetry, CSF to OB ratio, total CSF volume, total OB volume, and independent left and right CSF and OB volumes. Linear regression was used to evaluate MRI morphologic measurements with co-variates: CHD status, sex, MRI age, and segmenter. Executive function was determined by the Behavioral Rating Inventory of Executive Function (BRIEF) Parent Report and Delis-Kaplan Executive Function System (D-KEFS) for subjects ages 6-16. Cognition and olfactory function were measured with the NIH Toolbox Cognitive Battery and Odor Identification Test, respectively. No statistically significant results were reported between cohorts for asymmetry of OB, CSF to OB ratio, total CSF volume, total OB volume, nor between independent left and right CSF and OB volumes. Increased OB volume was associated with worse outcomes on the BRIEF Parent Report (p≤0.03). Asymmetry of OB predicted poorer executive functioning as reported by parents on the BRIEF (p≤0.05). Overall, the CHD cohort demonstrated worse scores on the BRIEF Parent Report compared to controls. Across groups, no significant association was reported for olfaction function measured by the NIH Toolbox Odor Identification Test on a limited subset of participants. As survival rates for CHD improve, there is an increased risk of long-term neurodevelopmental impairments. Our findings identify adolescents who are at risk for executive dysfunction, particularly those showing increased OB volume and/or asymmetry of the OB. This is particularly concerning for the CHD population with atypical OB morphology, who also exhibit significantly poorer outcomes on the BRIEF Parent Report and face a higher overall risk. Increased OB volume and OB asymmetry are olfactory-based biomarkers that may help identify at-risk CHD patients earlier, enabling more timely intervention and support.

Covariation of Skull and Brain Morphology in Domestic Dogs.

Despite their distinct embryonic origins, the skull and brain are highly integrated. Understanding the covariation between the skull and brain can shed light on anatomical, cognitive, and behavioral traits in extant and extinct species. Domestic dogs offer a unique opportunity to investigate skull-brain covariation due to their diverse skull morphologies and neural anatomy. To assess this question, we examined T2-weighted MRI studies of 62 dogs from 33 breeds, plus an additional 17 dogs of mixed or unknown breeds. Scans were opportunistically collected from a veterinary teaching hospital of dogs that were referred for neurological examination but did not have grossly observable structural brain abnormalities. As the neurocrania of dogs become broader and shorter, there is a significant decrease in the gray matter volume of the right olfactory bulb, frontal cortex, marginal gyrus, and cerebellum. On the other hand, as the neurocrania of dogs become narrower and longer, there is a significant decrease in the gray matter volume of the olfactory bulb, frontal cortex, temporal cortex, amygdala, hypothalamus, hippocampus, periaqueductal gray, cerebellum, and brainstem. Selective breeding for specific skull shapes may impact canine brain anatomy and function.

Reduced olfactory bulb volume accompanies olfactory dysfunction after mild SARS-CoV-2 infection

Despite its high prevalence, the determinants of smelling impairment in COVID-19 remain not fully understood. In this work, we aimed to examine the association between olfactory bulb volume and the clinical trajectory of COVID-19-related smelling impairment in a large-scale magnetic resonance imaging (MRI) analysis. Data of non-vaccinated COVID-19 convalescents recruited within the framework of the prospective Hamburg City Health Study COVID Program between March and December 2020 were analyzed. At baseline, 233 participants underwent MRI and neuropsychological testing as well as a structured questionnaire for olfactory function. Between March and April 2022, olfactory function was assessed at follow-up including quantitative olfactometric testing with Sniffin’ Sticks. This study included 233 individuals recovered from mainly mild to moderate SARS-CoV-2 infections. Longitudinal assessment demonstrated a declining prevalence of self-reported olfactory dysfunction from 67.1% at acute infection, 21.0% at baseline examination and 17.5% at follow-up. Participants with post-acute self-reported olfactory dysfunction had a significantly lower olfactory bulb volume at baseline than normally smelling individuals. Olfactory bulb volume at baseline predicted olfactometric scores at follow-up. Performance in neuropsychological testing was not significantly associated with the olfactory bulb volume. Our work demonstrates an association of long-term self-reported smelling dysfunction and olfactory bulb integrity in a sample of individuals recovered from mainly mild to moderate COVID-19. Collectively, our results highlight olfactory bulb volume as a surrogate marker that may inform diagnosis and guide rehabilitation strategies in COVID-19.

Effects of prenatal alcohol exposure on the olfactory system development.

Fetal Alcohol Spectrum Disorders (FASD), resulting from maternal alcohol consumption during pregnancy, are a prominent non-genetic cause of physical disabilities and brain damage in children. Alongside common symptoms like distinct facial features and neurocognitive deficits, sensory anomalies, including olfactory dysfunction, are frequently noted in FASD-afflicted children. However, the precise mechanisms underpinning the olfactory abnormalities induced by prenatal alcohol exposure (PAE) remain elusive. Utilizing rodents as a model organism with varying timing, duration, dosage, and administration routes of alcohol exposure, prior studies have documented impairments in olfactory system development caused by PAE. Many reported a reduction in the olfactory bulb (OB) volume accompanied by reduced OB neuron counts, suggesting the OB is a brain region vulnerable to PAE. In contrast, no significant olfactory system defects were observed in some studies, though subtle alterations might exist. These findings suggest that the timing, duration, and extent of fetal alcohol exposure can yield diverse effects on olfactory system development. To enhance comprehension of PAE-induced olfactory dysfunctions, this review summarizes key findings from previous research on the olfactory systems of offspring prenatally exposed to alcohol.

Effects of Endoscopic Sinus Surgery on Olfactory Bulb Volume among Patients with Chronic Rhinosinusitis: A Systematic Review and Meta-Analysis.

Endoscopic sinus surgery (ESS) could significantly improve olfactory function among patients with chronic rhinosinusitis (CRS). This study aimed to perform a meta-analysis to evaluate the effect of ESS on the olfactory bulb volume (OBV) among patients with CRS. A systemic search of PubMed, Medline, Embase, Web of Science, and other databases was conducted to identify studies assessing OBV changes in patients with CRS after ESS utilizing magnetic resonance imaging. A total of four studies with 168 participants were included. Comparing the changes in OBV of patients with CRS before and after surgery within 3-6 months, the ESS significantly improved the overall OBV (P = 0.005, I2 = 66%), with the left OBV increased by 5.57mm3 (P = 0.84, I2 = 0%), and the right OBV increased by 8.63mm3 (P = 0.09, I2 = 53%). A difference in OBV persists between healthy controls and patients with CRS 3-6 months after ESS. The overall OBV of patients with CRS after ESS was significantly smaller than controls (mean difference = -3.84, P = 0.04), with a mean difference of 4.13mm3 on the left side (P = 0.72, I2 = 0%), and a mean difference of 3.22mm3 on the right side (P = 0.0001, I2 = 89%). ESS significantly increases the OBV among patients with CRS.

Lateralisation of nasal cycle is not reflected in the olfactory bulb volumes and cerebral activations.

Nasal cycle (NC) is a rhythmic change of lateralised nasal airflow mediated by the autonomous nervous system. Previous studies reported the dependence of NC dominance or more patent side on handedness and hemispheric cerebral activity. We aimed to investigate firstly the possible lateralised effect of NC on olfactory bulb volume and secondly the association of NC with the lateralised cerebral dominance in terms of olfactory processing. Thirty-five subjects (22 women and 13 men, mean age 26 ± 3 years) participated in the study. NC was ascertained using a portable rhino-flowmeter. Structural and functional brain measurements were assessed using a 3T MR scanner. Vanillin odorant was presented during functional scans using a computer-controlled olfactometer. NC was found to be independent of the olfactory bulb volumes. Also, cerebral activations were found independent of the NC during odorant perception. NC potency is not associated with lateralised structural or functional differences in the cerebral olfactory system.

Vitamin D3 deficiency and smell regions in adolescents: an MRI evaluation

Abstract OBJECTIVES. We investigated the effect of vitamin D3 deficiency on peripheral and central odor centres by using cranial magnetic resonance imaging (MRI). MATERIAL AND METHODS. In this retrospective study, cranial MRI images of 23 adolescents with vitamin D3 deficiency and 18 adolescents with normal vitamin D3 levels (≥ 20 ng/ml) were evaluated. Blood tests for vitamin D3, B12, hemoglobin and calcium levels were also taken from the database of our hospital. Peripheral odor centers, olfactory bulb (OB) volume and olfactory sulcus (OS) depth, and also central odor centers, insular gyrus and corpus amygdala area were measured on cranial MRI. RESULTS. The insular gyrus and corpus amygdala area were not different between the study group with vitamin D3 deficiency and the control group (p>0.05). There was no difference between OB volume of the study and control groups (p>0.05). Although the right insular area was lower in girls than males (p<0.05), there was no correlation between OB volume and gender (p>0.05). Higher hemoglobin levels were related to higher OB volume on the right side (p<0.05). CONCLUSION. In the group with vitamin D3 deficiency, olfactory bulb volume of the left side was asymmetrically larger than the one on the right side. Therefore, the measurements of vitamin D3 should be performed in adolescents, and the patients with the vitamin D3 levels of < 20 ng/ml should be supplemented with medical treatment and reinforcing vitamin D synthesis by the exposure of sunlight more.

Inflammation-related pathology in the olfactory epithelium: its impact on the olfactory system in psychotic disorders.

Smell deficits and neurobiological changes in the olfactory bulb (OB) and olfactory epithelium (OE) have been observed in schizophrenia and related disorders. The OE is the most peripheral olfactory system located outside the cranium, and is connected with the brain via direct neuronal projections to the OB. Nevertheless, it is unknown whether and how a disturbance of the OE affects the OB in schizophrenia and related disorders. Addressing this gap would be the first step in studying the impact of OE pathology in the disease pathophysiology in the brain. In this cross-species study, we observed that chronic, local OE inflammation with a set of upregulated genes in an inducible olfactory inflammation (IOI) mouse model led to a volume reduction, layer structure changes, and alterations of neuron functionality in the OB. Furthermore, IOI model also displayed behavioral deficits relevant to negative symptoms (avolition) in parallel to smell deficits. In first episode psychosis (FEP) patients, we observed a significant alteration in immune/inflammation-related molecular signatures in olfactory neuronal cells (ONCs) enriched from biopsied OE and a significant reduction in the OB volume, compared with those of healthy controls (HC). The increased expression of immune/inflammation-related molecules in ONCs was significantly correlated to the OB volume reduction in FEP patients, but no correlation was found in HCs. Moreover, the increased expression of human orthologues of the IOI genes in ONCs was significantly correlated with the OB volume reduction in FEP, but not in HCs. Together, our study implies a potential mechanism of the OE-OB pathology in patients with psychotic disorders (schizophrenia and related disorders). We hope that this mechanism may have a cross-disease implication, including COVID-19-elicited mental conditions that include smell deficits.

Asymptomatic COVID-19 and structural changes in the brain

Aims: Neurological symptoms are the most prevalent extrapulmonary complications of coronavirus disease 2019 (COVID-19). In this context, the objective of this study is to assess the brain magnetic resonance imaging (MRI) parameters of asymptomatic COVID-19 individuals one year after diagnosed with COVID-19 in comparison with healthy control subjects. Methods: The population of this prospective study consisted of individuals who have not developed olfactory impairment or other complications within one year after diagnosed with COVID-19. For the study, 8 male, 25 female, 4 male and 23 female individuals were accepted for PCG and CG, respectively, according to the inclusion and exclusion criteria. The mean age was found to be 37.75±11.56 and 37.11±10.67, respectively. All participants included in the study underwent olfactory sulcus (OS) depth, olfactory bulb (OB) volume, hippocampal sclerosis (HS), insular gyrus area, and corpus amygdala area measurements. Results: The bilateral OB volume, insular gyrus area and corpus amygdala area were significantly lower in the post-COVID-19 group (PCG) than in the control group (CG) (p<0.05). On the other hand, the bilateral OS depth was significantly higher in PCG than in CG (p<0.05). In the PCG, the insular gyrus area and corpus amygdala area values of the right side were significantly higher than those of the left side (p<0.05). In addition, bilateral HS was detected in five patients in the PCG, right-sided HS in two patients, and left-sided HS in one patient. Conclusion: The findings of this study have shown that COVID-19 infection, albeit asymptomatic, can trigger neurodegeneration. We believe that in the future COVID-19 infection will play a role in the etiopathogenesis of many neurodegenerative diseases.

Prevalence of smell and taste dysfunction in different clinical severity groups of COVID-19 patients

BACKGROUND: Studies on the long-term prevalence of smell and taste impairment concerned with severe disease in the acute phase of COVID-19 are limited. The aim of our study was to assess and compare psychophysical testing and self-reported smell and taste disturbances and recovery between three patient groups suffering from critical, severe, or mild COVID-19 in a follow-up at six-months after the acute phase. METHODOLOGY: The prospective controlled study of 227 participants comprised 72 intensive-care-unit-treated (ICU-treated), 53 pulmonology- or infectious-diseases-ward-treated (WARD-treated), and 48 home-isolated patients (HOME) with preceding COVID-19, and 54 individuals with no history of COVID-19 (CONTROL). All participants visited a follow-up clinic for a sense-of-smell screening and underwent Magnetic Resonance Imaging (MRI) of the brain, olfactory bulbs and sinonasal area at six months after acute disease. Before the follow-up visit, the participants received a questionnaire concerning smell and taste function. We sent a supplementary questionnaire including questions about phantosmia and parosmia and taste recovery at a median of 502.5 days after the acute phase. RESULTS: We found no statistically significant differences between the groups in the incidence of smell and taste dysfunction, recovery, or the occurrence of parosmia or phantosmia. There were no statistically significant differences in semi-objective smell performance across the different study groups and controls. The olfactory bulb volume was normal in all patients and controls. Mucosal thickening in paranasal sinuses was rare. CONCLUSIONS: We found no difference in a six-month follow-up in the subjective or semi-objective senses of smell and taste between three severity groups of COVID-19 and controls.

Diabetic Neuropathy Is Related to Rhinencephalon Degeneration in Adults With Type 1 Diabetes

Aims: We aimed to assess neurodegenerative changes in the rhinencephalon via magnetic resonance imaging (MRI) and relate it to olfactory function and diabetic peripheral neuropathy (DPN) in adults with type 1 diabetes (T1D).Materials and Methods: Individuals aged 18–65 with T1D duration over 10 years and control healthy subjects underwent olfactory assessment using Sniffin’Sticks and brain MRI to assess volumetric measurements of the olfactory bulbs and piriform cortex thickness.Results: 32 T1D (24 males) aged 43.5 years (IQR: 37.0–48), diabetes duration 24.5 years (IQR: 20.5–27.0), and A1C 7.95% (IQR: 7.4–8.4) were assessed. The control group consisted of 6 healthy adults (4 males) aged 41.0 years (IQR: 36.0–48.0). Significantly lower olfactory test results in TDI (threshold‐differentiation‐identification) (31.5 (IQR: 28.7–33.6) vs. 34.1 (IQR: 33.2–37.2), p = 0.02) were obtained in the T1D as compared to the controls. Summarized olfactory bulb (OB) volumes and thickness of the left pyriform cortex were significantly smaller in T1D than in controls (65.8 mm3 (IQR: 57.9–71.7) vs. 75.8 mm3 (IQR: 74.8–76.7); p = 0.0005 and 3.1 mm (IQR: 2.7–3.4) vs. 3.6 mm (IQR: 3.5–4.1); p =0.02). Patients with DPN had significantly smaller OB volumes than patients without DPN (58.1 mm3 (IQR: 54.0–70.9) vs. 69.8 mm3 (IQR: 65.0–72.2); p = 0.02). Tobacco smoking (β: −7.89; p = 0.013) and DPN (β:−7.02; p = 0.015) proved to be independent predictors of OB volume.Conclusions: In adults with a long history of T1D, olfactory function and structures are impaired. The presence of diabetic neuropathy and ongoing smoking addiction might be considered predictors of the degradation of rhinencephalon structures in people with T1D.

Olfactory Bulb Volume and Morphology Changes in COVID-19 Patients With Olfactory Disorders Using Magnetic Resonance Imaging.

The aims of the study are to explore the morphological changes of olfactory bulb (OB) and olfactory sulcus in COVID-19 patients with associated olfactory dysfunction (OD) by measuring the OB volume (OBV) and olfactory sulcus depth (OSD) and to compare the measurement values with those of healthy individuals. Between March 2020 and January 2022, 31 consecutive hospitalized patients with a diagnosis of COVID-19 with anosmia and hyposmia who underwent brain magnetic resonance imaging and 35 normosmic control individuals were retrospectively included in the study. Bilateral OBV and OSD were measured and shape of the OB was determined based on the consensus by a neuroradiologist and an otorrhynolaryngologist. The mean measurements for the right and the left sides for OBV (38 ± 8.5 and 37.1 ± 8.4, respectively) and OSD (7.4 ± 0.1 and 7.4 ± 1.0 mm, respectively) were significantly lower in COVID-19 patients with OD than those in control group (for the right and the left sides mean OBV 56.3 ± 17.1 and 49.1 ± 13.5, respectively, and mean OSD 9.6 ± 0.8 and 9.4 ± 0.8 mm, respectively). Abnormally shaped OB (lobulated, rectangular, or atrophic) were higher in patient group than those of controls.For the optimal cutoff values, OBV showed sensitivity and specificity values of 90.32% and, 57.14%, for the right, and 87.1% and 62.86% for the left side, respectively (area under the curve, 0.819 and 0.780). Olfactory sulcus depth showed sensitivity and specificity values of 90.32% and 94.29%, for the right, and 96.77% and 85.71%, for the left side, respectively (area under the curve, 0.960 and 0.944). Decrease in OBV and OSD measurements in COVID-19 patients with OD at the early chronic stage of the disease supports direct damage to olfactory neuronal pathways and may be used to monitor olfactory nerve renewal while returning back to normal function.

Evaluation of peripheral and central olfactory pathways in HIV-infected patients by MRI

To investigate peripheral and central olfactory pathways using cranial magnetic resonance imaging (MRI) in human immunodeficiency virus (HIV)-infected patients. The cranial MRI images of 37 HIV-infected adult patients and 37 adults without HIV infection having normal cranial MRI results were included in the study. In both groups, olfactory bulb (OB) volume and olfactory sulcus (OS) depth; and insular gyrus and corpus amygdala areas were measured using cranial MRI. In the HIV group, disease duration, HIV RNA, and CD4 lymphocyte count and levels as a percentage were also recorded. The HIV group had significantly lower bilateral OB volumes, insular gyrus and corpus amygdala areas compared to the control group. The HIV group showed positive correlations between OB volumes, OS depths, insular gyrus, and corpus amygdala areas bilaterally. Increases in OB volumes and OS depths were associated with an increase in the insular gyrus area. The corpus amygdala and insular gyrus areas increased similarly. There was no significant correlation between age, gender, disease duration, CD4 lymphocyte count and per cent, HIV RNA values, and the measurement values of the central and peripheral olfactory regions. A decrease in olfactory regions of OB, insular gyrus, and corpus amygdala in HIV-infected patients shows that HIV infection may cause olfactory impairment. There is no correlation between disease duration and olfactory impairment. It may be related to neuroinflammation, HIV-related brain atrophy, acquired immunodeficiency syndrome (AIDS) dementia complex, or neurocognitive impairment, which are the other explanations for the olfactory impairment in HIV. The possible toxicity from antiretroviral therapy (ART) may be another cause that should be investigated further.

Olfactory bulbectomy leads to prolonged induction phase of sevoflurane anesthesia in rats.

The effect of olfactory bulb lesions on the induction time of sevoflurane has never been studied. We aimed to investigate this issue. In this study, we found that the volume of olfactory bulbs and the pore of the fila olfactoria were significantly lower with the fibrosis of olfactory bulbs in animals subjected to olfactory bulbectomy. Volatile anesthetics induction times were measured in all groups. Prolonged induction was observed in olfactory bulbectomy group. It was concluded that increased induction times of sevoflurane may be due to the olfactory bulb lesion.

Neuronal scaling in the olfactory system of bats.

Comparative studies are a common way to address large-scale questions in sensory biology. For studies that investigate olfactory abilities, the most commonly used metric is olfactory bulb size. However, recent work has called into question the broad-scale use of olfactory bulb size. In this paper, we use three neuroanatomical measures with a more mechanistic link to olfactory function (number of olfactory sensory neurons (OSNs), number of mitral cells (MCs), and number of glomeruli) to ask how species with different diets may differ with respect to olfactory ability. We use phyllostomid bats as our study system because behavioral and physiological work has shown that fruit- and nectar-feeding phyllostomids rely on odors for detecting, localizing, and assessing potential foods, while insect-eating species do not. Therefore, we predicted that fruit- and nectar-feeding bats would have larger numbers of these three neuroanatomical measures than insect-eating species. In general, our results supported the predictions. We found that fruit-eaters had greater numbers of OSNs and glomeruli than insect-eaters, but we found no difference between groups in number of MCs. We also examined the allometric relationship between the three neuroanatomical variables and olfactory bulb volume, and we found isometry in all cases. These findings lend support to the notion that neuroanatomical measures can offer valuable insights into comparative olfactory abilities, and suggest that the size of the olfactory bulb may be an informative parameter to use at the whole-organism level.

Gray Matter Changes Following Mild COVID-19: An MR Morphometric Study in Healthy Young People.

Although COVID-19 is primarily an acute respiratory infection, 5%-40% of patients develop late and prolonged symptoms with frequent neurological complaints, known as long COVID syndrome. The presentation of the disease suggests that COVID infection may cause functional and/or morphological central nervous system alterations, but studies published in the literature report contradictory findings. To investigate the chronic effects of COVID-19 on cerebral grey matter in a group of young patients without comorbidities, with mild course of COVID infection and no medical complaints at the time of examination. Prospective. Thirty-eight young (age = 26.6 ± 5.0 years; male/female = 14/24), adult participants who recovered from mild COVID infection without a history of clinical long COVID and 37 healthy control subjects (age = 25.9 ± 2.8 years; male/female = 14/23). Three Tesla, 3D T1-weighted magnetization-prepared rapid gradient-echo, 2D T2-weighted turbo spin-echo. MRI-based morphometry and volumetry along with neuropsychological testing and self-assessed questionnaire. Fisher's exact test, Mann-Whitney U-test, and multiple linear regression analyses were used to assess differences between COVID and healthy control groups. P < 0.05 was used as cutoff for significance. In the COVID group, significantly lower bilateral mean cortical thickness (left/right-hemisphere: 2.51 ± 0.06 mm vs. 2.56 ± 0.07 mm, η2 p = 0.102/2.50 ± 0.06 mm vs. 2.54 ± 0.07 mm, η2 p = 0.101), lower subcortical gray matter (57881 ± 3998 mm3 vs. 60470 ± 5211 mm3, η2 p = 0.100) and lower right olfactory bulb volume (52.28 ± 13.55 mm3 vs. 60.98 ± 15.8 mm3, η2 p = 0.078) were found. In patients with moderate to severe anosmia, cortical thickness was significantly lower bilaterally, as compared to patients without olfactory function loss (left/right-hemisphere: 2.50 ± 0.06 mm vs. 2.56 ± 0.05 mm, η2 = 0.173/2.49 ± 0.06 mm vs. 2.55 ± 0.05 mm, η2 = 0.189). Using further exploratory analysis, significantly reduced cortical thickness was detected locally in the right lateral orbitofrontal cortex in the COVID group (2.53 ± 0.10 mm vs. 2.60 ± 0.09 mm, η2 p = 0.112). Even without any subjective or objective neurological complaints at the time of the MR scan, subjects in the COVID group showed gray matter alterations in cortical thickness and subcortical gray matter volume. 2 TECHNICAL EFFICACY: Stage 3.

Altered structural connectivity in olfactory disfunction after mild COVID-19 using probabilistic tractography

We aimed to investigate changes in olfactory bulb volume and brain network in the white matter (WM) in patients with persistent olfactory disfunction (OD) following COVID-19. A cross-sectional study evaluated 38 participants with OD after mild COVID-19 and 24 controls, including Sniffin' Sticks identification test (SS-16), MoCA, and brain magnetic resonance imaging. Network-Based Statistics (NBS) and graph theoretical analysis were used to explore the WM. The COVID-19 group had reduced olfactory bulb volume compared to controls. In NBS, COVID-19 patients showed increased structural connectivity in a subnetwork comprising parietal brain regions. Regarding global network topological properties, patients exhibited lower global and local efficiency and higher assortativity than controls. Concerning local network topological properties, patients had reduced local efficiency (left lateral orbital gyrus and pallidum), increased clustering (left lateral orbital gyrus), increased nodal strength (right anterior orbital gyrus), and reduced nodal strength (left amygdala). SS-16 test score was negatively correlated with clustering of whole-brain WM in the COVID-19 group. Thus, patients with OD after COVID-19 had relevant WM network dysfunction with increased connectivity in the parietal sensory cortex. Reduced integration and increased segregation are observed within olfactory-related brain areas might be due to compensatory plasticity mechanisms devoted to recovering olfactory function.

From Nose to Lumbar Spinal Cord – Reduced Sperm Numbers Occur by Olfactory Bulbectomy-Related Onuf’s Nucleus Degeneration: New Experimental Evidence for Kallmann Syndrome

Introduction: Olfaction and its relation to human health is an area of growing interest. Although olfaction disorders have been considered a part of Kallmann syndrome, the role of olfactory dysfunction on spermatogenesis has not been studied yet. We studied if olfactory bulbectomy (OBX) causes dysfunction in spermatogenesis as a result of Onuf’s nucleus damage. Methods: Twenty-eight male rats were divided into three groups: six as the control (G-1; n = 6), six as the only frontal burr hole applied animals SHAM (G-2; n = 6), and 16 as the study group (G-3; n = 16) in which OBX was performed. The animals were followed for 2 months. After the decapitation of the animals, olfactory bulb (OB) volumes (mm3), the neuron density of the Onuf’s nucleus (n/mm3), and sperm density (n/mm3) were estimated stereologically and analyzed. Results: OB volumes (mm3), degenerated neuron density of Onuf’s nucleus (n/mm3), and sperm numbers of control, SHAM, and study groups were estimated as: 4 ± 0.5; 6 ± 2 and 103.245 ± 10.841 in G-1; 3.5 ± 0.7; 14 ± 4 and 96.891 ± 9.569 in G-2; and 1.3 ± 0.3; 91 ± 17 and 73.561 ± 6.324 in G-3. The statistical results of degenerated neuron density of Onuf’s nucleus and sperm numbers between groups are p < 0.005 for G-1/G-2; p < 0.0005 for G-2/G-3; and p < 0.00001 for G-1/G-3. Discussion: This study first time indicates that Onuf’s nucleus degeneration secondary to OBX seems to be responsible for reduced sperm numbers.

Peripheral and central olfactory measurements in Chronic Obstructive Pulmonary Disease patients

Abstract OBJECTIVES. We investigated peripheric and central olfactory pathways on MRI in Chronic Obstructive Pulmonary Disease (COPD) patients and the relationship between olfactory measurements of COPD patients and thorax CT images of emphysema classification in them. MATERIAL AND METHODS. In this retrospective study, cranial MRI of 42 adult patients with COPD and 42 healthy adults without COPD were included. In both groups, peripheral (olfactory bulb (OB) volume and olfactory sulcus (OS) depth) and central olfactory areas (insular gyrus and corpus amygdala areas) were evaluated. We classified thorax CT findings according to emphysema by size as 1 to 4. RESULTS. In the present study, left OB volume of the COPD group was significantly lower than that in the control group (p&lt;0.05). On the right side, there were no significant differences between OB volumes of the COPD and control groups. Although right OB volume values were found to decrease proportionally, they were not found to be statistically significant. Also, insular gyrus and corpus amygdala areas of the COPD group were significantly lower than those in the control group, bilaterally (p&lt;0.05). OS depths of the COPD group were significantly higher than those in the control group, bilaterally (p&lt;0.05). In males, the right OB volume values were higher than those in females (p&lt;0.05). CONCLUSION. In COPD patients, left OB volumes decrease and OS depths increase bilaterally, and central areas decrease bilaterally, regardless of the thoracic emphysema classification. It may be related to hypoxemia that causes airway inflammation; inflammatory mediators may be harmful to the olfactory neuroepithelium.