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

OBJECTIVES

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.

METHODS

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.

RESULTS

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).

CONCLUSIONS

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.

Olfactory training with four and eight odors: comparison with clinical testing and olfactory bulb volumetrics

PURPOSE

Post-infectious olfactory dysfunction (PIOD) is one of the most common causes of olfactory impairment but has limited treatment options. Recently, olfactory training (OT) has been considered an effective treatment method; however, several questions have arisen regarding its optimal scheme. The aim of this study was to assess whether an OT scheme with 8 odors is more effective than the classic OT scheme with 4 odors by comparing psychophysical test results and olfactory bulb (OB) volumetrics.

METHODS

In this prospective cohort study, 72 patients with PIOD were included. The patients followed either the classic 4-odor OT scheme (COT; n = 34 patients) or an extended 8-odor scheme (EOT; n = 38 patients) for 16 weeks. All patients underwent olfactory testing with a Sniffin'Sticks battery test at 0, 8, and 16 weeks. Of the patients, 38 underwent brain magnetic resonance imaging for OB volumetric assessment before and after treatment.

RESULTS

The comparison of the olfactory test results did not show any significant difference between the two study groups, in agreement with the OB volumetrics. The convex OB showed better test results than the non-convex OB, with significantly better improvement after treatment regardless of OT type. The EOT group presented significantly better adherence than the COT group.

CONCLUSION

The number of odors did not appear to play a significant role in the effect of the OT. However, the training scheme with more than four odors showed better adherence among the patients in a long-term treatment plan. The shape of the OB may have prognostic value in clinical assessment and warrants further investigation.

Neuroimaging the Development of Olfactory Function in a Woman With No Olfactory Bulbs

This case report describes a woman with lifelong anosmia in her 20s who presented with the acquisition of unpleasant olfactory phantoms.

Functional MRI of murine olfactory bulbs at 15.2T reveals characteristic activation patters when stimulated by different odors

Thanks to its increased sensitivity, single-shot ultrahigh field functional MRI (UHF fMRI) could lead to valuable insight about subtle brain functions such as olfaction. However, UHF fMRI experiments targeting small organs next to air voids, such as the olfactory bulb, are severely affected by field inhomogeneity problems. Spatiotemporal Encoding (SPEN) is an emerging single-shot MRI technique that could provide a route for bypassing these complications. This is here explored with single-shot fMRI studies on the olfactory bulbs of male and female mice performed at 15.2T. SPEN images collected on these organs at a 108 µm in-plane resolution yielded remarkably large and well-defined responses to olfactory cues. Under suitable T2* weightings these activation-driven changes exceeded 5% of the overall signal intensity, becoming clearly visible in the images without statistical treatment. The nature of the SPEN signal intensity changes in such experiments was unambiguously linked to olfaction, via single-nostril experiments. These experiments highlighted specific activation regions in the external plexiform region and in glomeruli in the lateral part of the bulb, when stimulated by aversive or appetitive odors, respectively. These strong signal activations were non-linear with concentration, and shed light on how chemosensory signals reaching the olfactory epithelium react in response to different cues. Second-level analyses highlighted clear differences among the appetitive, aversive and neutral odor maps; no such differences were evident upon comparing male against female olfactory activation regions.

Reduced olfactory bulb volume and olfactory sulcus depth in obsessive compulsive disorder

Many studies have shown that limbic system abnormalities are seen in obsessive-compulsive disorder (OCD), but the neurobiological changes in OCD are still unclear. Moreover, olfactory bulb volume (OBV) and its association with symptom severity have not been yet investigated in patients with OCD. This is the first study on OBV and olfactory sulcus depth (OSD) values in OCD patients, to the best of our knowledge. Between January 2018 and March 2022, 25 patients with OCD and 26 healthy controls with brain magnetic resonance imaging (MRI) were included. Detailed disease history of OCD patients was taken, and Yale-Brown obsessive-compulsive scale (YBOCS) was applied. The mean age of the patient group was 33.40±9.58, the mean age of the control group was 32.84±8.01. LOBV, ROBV, TOBV, and LOSD in the patient group were significantly lower than in the control group (p=.013, p=.005, p=.001, p=.015, respectively). ROBV and TOBV were negatively correlated with YBOCS total and subscale scores. A negative correlation was found between ROBV and TOBV and disease duration (r=-0.749 and r=-0.640, respectively). The negative correlation of ROBV and TOBV values with disease duration and disease severity can be used to monitor the neurodegenerative process of OCD disease.

The potential for clinical application of automatic quantification of olfactory bulb volume in MRI scans using convolutional neural networks

The olfactory bulbs (OBs) play a key role in olfactory processing; their volume is important for diagnosis, prognosis and treatment of patients with olfactory loss. Until now, measurements of OB volumes have been limited to quantification of manually segmented OBs, which is a cumbersome task and makes evaluation of OB volumes in large scale clinical studies infeasible. Hence, the aim of this study was to evaluate the potential of our previously developed automatic OB segmentation method for application in clinical practice and to relate the results to clinical outcome measures. To evaluate utilization potential of the automatic segmentation method, three data sets containing MR scans of patients with olfactory loss were included. Dataset 1 (N = 66) and 3 (N = 181) were collected at the Smell and Taste Center in Ede (NL) on a 3 T scanner; dataset 2 (N = 42) was collected at the Smell and Taste Clinic in Dresden (DE) on a 1.5 T scanner. To define the reference standard, manual annotation of the OBs was performed in Dataset 1 and 2. OBs were segmented with a method that employs two consecutive convolutional neural networks (CNNs) that the first localize the OBs in an MRI scan and subsequently segment them. In Dataset 1 and 2, the method accurately segmented the OBs, resulting in a Dice coefficient above 0.7 and average symmetrical surface distance below 0.3 mm. Volumes determined from manual and automatic segmentations showed a strong correlation (Dataset 1: r = 0.79, p < 0.001; Dataset 2: r = 0.72, p = 0.004). In addition, the method was able to recognize the absence of an OB. In Dataset 3, OB volumes computed from automatic segmentations obtained with our method were related to clinical outcome measures, i.e. duration and etiology of olfactory loss, and olfactory ability. We found that OB volume was significantly related to age of the patient, duration and etiology of olfactory loss, and olfactory ability (F(5, 172) = 11.348, p < 0.001, R2 = 0.248). In conclusion, the results demonstrate that automatic segmentation of the OBs and subsequent computation of their volumes in MRI scans can be performed accurately and can be applied in clinical and research population studies. Automatic evaluation may lead to more insight in the role of OB volume in diagnosis, prognosis and treatment of olfactory loss.

Cholinergic Nucleus 4 Degeneration and Cognitive Impairment in Isolated Rapid Eye Movement Sleep Behavior Disorder

BACKGROUND

Cholinergic nucleus 4 (Ch4) degeneration is associated with cognitive impairment in Parkinson's disease and dementia with Lewy bodies, but it is unknown if Ch4 degeneration is also present in isolated rapid eye movement sleep behavior disorder (iRBD).

OBJECTIVE

The aim was to determine if there is evidence of Ch4 degeneration in patients with iRBD and if it is associated with cognitive impairment.

METHODS

We analyzed the clinical and neuropsychological data of 35 iRBD patients and 35 age- and sex-matched healthy controls. Regional gray matter density (GMD) was calculated for Ch4 using probabilistic maps applied to brain magnetic resonance imaging (MRI).

RESULTS

Ch4 GMD was significantly lower in the iRBD group compared to controls (0.417 vs. 0.441, P = 0.02). Ch4 GMD was also found to be a significant predictor of letter number sequencing (β-coefficient = 58.31, P = 0.026, 95% confidence interval [7.47, 109.15]), a measure of working memory.

CONCLUSIONS

iRBD is associated with Ch4 degeneration, and Ch4 degeneration in iRBD is associated with impairment in working memory. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Is abnormal metabolism in the olfactory bulb and amygdala associated with bipolar disorder?

Accumulated evidence has demonstrated abnormal amygdala activation in bipolar disorder (BD). The olfactory bulb (OB) has vigorous connections with the amygdala. Although odor-related functions of the OB decreased during the evolutionary process, we hypothesized that an evolved OB with increased activation in emotion regulation may be one of the main factors affecting amygdala functions in BD. Our aim was to investigate metabolism in the OB and amygdala in patients with BD. Twenty-six patients diagnosed with BD according to DSM-5 diagnostic criteria were included in this cross-sectional study. Metabolism in the OB and amygdala was assessed using fluorodeoxyglucose positron emission tomography/CT in patients with BD. The OB and amygdala metabolism was compared with the patients' Z scores. Both OB and amygdala metabolic activities were significantly higher than in the controls. A positive correlation was detected between right/left amygdala metabolism and right OB metabolism (p < 0.05, r:467 and r:662, respectively). This study increased our understanding of the etiopathogenesis of BD. In BD, the main cause of hypermetabolism in the amygdala may be increased metabolism in the OB. During evolution, the OB may have assumed a dominant role in emotional processing rather than olfactory functions.

Deep Learning-Based Segmentation of Post-Mortem Human’s Olfactory Bulb Structures in X-ray Phase-Contrast Tomography

The human olfactory bulb (OB) has a laminar structure. The segregation of cell populations in the OB image poses a significant challenge because of indistinct boundaries of the layers. Standard 3D visualization tools usually have a low resolution and cannot provide the high accuracy required for morphometric analysis. X-ray phase contrast tomography (XPCT) offers sufficient resolution and contrast to identify single cells in large volumes of the brain. The numerous microanatomical structures detectable in XPCT image of the OB, however, greatly complicate the manual delineation of OB neuronal cell layers. To address the challenging problem of fully automated segmentation of XPCT images of human OB morphological layers, we propose a new pipeline for tomographic data processing. Convolutional neural networks (CNN) were used to segment XPCT image of native unstained human OB. Virtual segmentation of the whole OB and an accurate delineation of each layer in a healthy non-demented OB is mandatory as the first step for assessing OB morphological changes in smell impairment research. In this framework, we proposed an effective tool that could help to shed light on OB layer-specific degeneration in patients with olfactory disorder.

Transient modifications of the olfactory bulb on MR follow-up of COVID-19 patients with related olfactory dysfunction

BACKGROUND

Olfactory dysfunction (OD) has been reported with a high prevalence on mild to moderate COVID-19 patients. Previous reports suggest that volume and signal intensity of olfactory bulbs (OB) have been reported as abnormal on acute phase of COVID-19 anosmia, but a prospective MRI and clinical follow-up study of COVID-19 patients presenting with OD was missing, aiming at understanding the modification of OB during patients'follow-up.

METHODS

A prospective multicenter study was conducted including 11 COVID-19 patients with OD. Patients underwent MRI and psychophysical olfactory assessments at baseline and 6-month post-COVID-19. T2 FLAIR-Signal intensity ratio (SIR) was measured between the average signal of the OB and the average signal of white matter. OB volumes and obstruction of olfactory clefts (OC) were evaluated at both evaluation times.

RESULTS

The psychophysical evaluations demonstrated a 6-month recovery in 10/11 patients (90.9%). The mean values of OB-SIR significantly decreased from baseline (1.66±0.24) to 6-month follow-up (1.35±0.27), reporting a mean variation of -17.82±15.20 % (p<0.001). The mean values of OB volumes significantly decreased from baseline (49.22±10.46 mm3) to 6-month follow-up (43.70±9.88 mm3), (p=0.006).

CONCLUSION

Patients with demonstrated anosmia reported abnormalities in OB imaging that may be objectively evaluated with the measurement of SIR and OB volumes. SIR and OB volumes significantly normalized when patient recovered smell. This supports the underlying mechanism of a transient inflammation of the OB as a cause of Olfactory Dysfunction in COVID-19 patients.

[Prognostic value of olfactory bulb volume in patients with post-viral olfactory dysfunction]

Objective:The purpose of this study was to compare the olfactory function examination results of patients with post-viral olfactory dysfunction（PVOD） in different prognostic groups and analyze prognostic factors, especially the influence of olfactory bulb volume（OBV） on prognosis, so as to provide objective basis for clinical diagnosis and treatment. Methods:After approval by the hospital ethics committee, the patients with PVOD admitted to Beijing Anzhen Hospital's outpatient department from January 2019 to December 2019 were followed up for at least 1 year. These patients completed the Sniffin' Sticks test and MRI examination of the olfactory pathway before treatment. According to the results of the Sniffin' Sticks test after 1 year follow-up（threshold-discrimination-identification（TDI） score of the patients was increased at least 6 points）, the patients were divided into two groups as the improvement group and the non-improvement group. The prognostic factors of PVOD patients were preliminarily determined by comparing the differences of various factors and the results of olfactory function examination between the two groups. Results:In this study, 47 patients with PVOD were included, with the smell improvement rate was 53.2%. Compared with the improvement group, the patients in the non-improvement group had longer duration, poorer initial olfactory function, higher olfactory threshold, and poorer olfactory discrimination and recognition ability（All P<0.01）. There was no statistical difference in terms of gender, age, allergic rhinitis and smoking between the two groups（All P>0.05）.The OBV of the non-improvement group was （59.48±23.92） mm³, which was significantly lower than that in the improvement group（[92.77±14.35]mm³, P<0.001）. Multiple logistic regression analysis showed that prognostic factors included course of disease（OR 0.677, 95%CI 0.461-0.993, P=0.046）, initial T value（OR 263.806, 95%CI 1.028-67 675.884, P=0.049） and OBV（OR 1.160, 95%CI 1.002-1.343, P=0.047）. The area under the receiver operating characteristic curve（ROC curve） of OBV was 0.888（0.797-0.979, P<0.001）. The correct diagnostic index of OBV≥78.50 mm³was used to determine the prognosis of olfactory function, with a specificity of 0.818 and a sensitivity of 0.840. The ROC curve analysis showed that the area under the ROC curve of duration was 0.822（0.703-0.940, P<0.001）. The correct diagnostic index of the duration ≤6 months was used to determine the prognosis of olfactory function, with a specificity of 0.727 and a sensitivity of 0.800. The area of T score was 0.793（0.662-0.924, P=0.001）. T score ≥1.25 was used as the correct diagnostic index to determine the prognosis of olfactory function. The specificity and sensitivity were 0.818 and 0.680, respectively. Conclusion:The prognosis of olfactory function in PVOD patients is related to the course of disease, the degree of olfactory loss and OBV. Those with no improvement in olfactory function have a longer disease course, aggravated olfactory damage and reduced OBV than those with improved olfactory function. The factors of Duration ≤6 months, T value ≥1.25 and OBV≥78.50 mm³suggested better prognosis, and the results of objective olfactory examination have greater value in evaluating the prognosis of olfactory function.

Identification of FOXG1 mutations in infantile hypotonia and postnatal microcephaly

ABSTRACT

FOXG1, located at chromosome 14q12, is critical for brain development, and patients with FOXG1 mutation exhibit developmental encephalopathy with high phenotypic variability, known as FOXG1 syndrome. Here, we report 3 cases of FOXG1 syndrome that presented with infantile hypotonia and microcephaly.A total of 145 children with developmental delay and/or hypotonia were evaluated by whole-exome sequencing (WES) in the pediatric neurology clinic and medical genetics center at Asan Medical Center Children's Hospital, from 2017 to 2019. Each FOXG1 mutation was confirmed by Sanger sequencing. The clinical findings of each patient with FOXG1 mutation were reviewed.WES identified de-novo, pathogenic, and heterozygous FOXG1 mutations in 3 of 145 patients in our patient cohort with developmental delay and/or hypotonia. The characteristics of brain magnetic resonance imaging (MRI) were reported as callosal anomaly, decrease in frontal volume, fornix thickening, and hypoplastic olfactory bulbs. A phenotype-genotype correlation was demonstrated as a patient with a novel missense mutation, c.761A > C (p.Tyr254Ser), in the forkhead domain had better outcome and milder brain abnormalities than the other 2 patients with truncating mutation in the Groucho binding domain site, c.958delC (p.Arg320Alafs), or N-terminal domain, c.506dup (p.Lys170GlnfsThe). Importantly, all 3 patients had hypoplastic olfactory bulbs on their brain MRI, which is a distinct and previously unrecognized feature of FOXG1 syndrome.This is the first report of FOXG1 syndrome in a Korean population; this condition accounts for 2% (3 of 145 patients) of our patient cohort with developmental delays and/or hypotonia. Our report contributes to understanding this extremely rare genetic condition in the clinical and genetic perspectives.

Automated olfactory bulb segmentation on high resolutional T2-weighted MRI

The neuroimage analysis community has neglected the automated segmentation of the olfactory bulb (OB) despite its crucial role in olfactory function. The lack of an automatic processing method for the OB can be explained by its challenging properties (small size, location, and poor visibility on traditional MRI scans). Nonetheless, recent advances in MRI acquisition techniques and resolution have allowed raters to generate more reliable manual annotations. Furthermore, the high accuracy of deep learning methods for solving semantic segmentation problems provides us with an option to reliably assess even small structures. In this work, we introduce a novel, fast, and fully automated deep learning pipeline to accurately segment OB tissue on sub-millimeter T2-weighted (T2w) whole-brain MR images. To this end, we designed a three-stage pipeline: (1) Localization of a region containing both OBs using FastSurferCNN, (2) Segmentation of OB tissue within the localized region through four independent AttFastSurferCNN - a novel deep learning architecture with a self-attention mechanism to improve modeling of contextual information, and (3) Ensemble of the predicted label maps. For this work, both OBs were manually annotated in a total of 620 T2w images for training (n=357) and testing. The OB pipeline exhibits high performance in terms of boundary delineation, OB localization, and volume estimation across a wide range of ages in 203 participants of the Rhineland Study (Dice Score (Dice): 0.852, Volume Similarity (VS): 0.910, and Average Hausdorff Distance (AVD): 0.215 mm). Moreover, it also generalizes to scans of an independent dataset never encountered during training, the Human Connectome Project (HCP), with different acquisition parameters and demographics, evaluated in 30 cases at the native 0.7 mm HCP resolution (Dice: 0.738, VS: 0.790, and AVD: 0.340 mm), and the default 0.8 mm pipeline resolution (Dice: 0.782, VS: 0.858, and AVD: 0.268 mm). We extensively validated our pipeline not only with respect to segmentation accuracy but also to known OB volume effects, where it can sensitively replicate age effects (β=-0.232, p<.01). Furthermore, our method can analyze a 3D volume in less than a minute (GPU) in an end-to-end fashion, providing a validated, efficient, and scalable solution for automatically assessing OB volumes.

More that ACE2? NRP1 may play a central role in the underlying pathophysiological mechanism of olfactory dysfunction in COVID-19 and its association with enhanced survival

Three mechanisms have been proposed to account for COVID-19 associated olfactory dysfunction; obstruction of the olfactory cleft; epithelial injury and infection of the sustentacular supporting cells, which are known to express ACE2, or injury to the olfactory bulb due to axonal transport through olfactory sensory neurones. The absence of ACE2 expression by olfactory sensory neurones has led to the neurotropic potential of COVID-19 to be discounted. While an accumulating body of evidence supports olfactory epithelial injury as an important mechanism, this does not account for all the features of olfactory dysfunction seen in COVID-19; for example the duration of loss in some patients, evidence of changes within the olfactory bulb on MRI imaging, identification of viral particles within the olfactory bulb in post-mortem specimens and the inverse association between severity of COVID-19 and the prevalence of olfactory loss. The recent identification of a second route of viral entry mediated by NRP1 addresses many of these inconsistencies. Expression by the olfactory sensory neurones and their progenitor cells may facilitate direct injury and axonal transport to the olfactory bulb as well as a mechanism for delayed or absent recovery. Expression by regulatory T cells may play a central role in the cytokine storm. Variability in expression by age, race or gender may explain differing morbidity of infection and inverse association between anosmia and severity; in the case of higher expression there may be a higher risk of olfactory function but greater activation of regulatory T cells that may suppress the cytokine storm.

A novel technique for olfactory bulb measurements

Background

To introduce new ways to calculate OB volumes, checking their validity and comparing them to already established technique i.e. OB volumetric based on manual segmentation of OB boundaries.

Methods

Two approaches were used to calculate OB volumes (1) Manual Segmentation using planimetric manual contouring; (2) Box-frame method, calculating the parameters based on a box placed around the OB.

Results

We calculated OB volumes using both techniques and found comparable outcomes. High inter-observer reliability was found for volumes calculated by both observers. For manual segmentation, Cronbach’s alpha (α) was 0.91 and 0.93 for right and left OB volume, respectively, whereas for the box-frame method α was 0.94 and 0.90 for right and left OB, respectively.

Conclusions

The simple box-frame method of OB volume calculation appears reliable. Its results are comparable to an established technique.

Olfactory epithelium histopathological findings in long-term coronavirus disease 2019 related anosmia

BACKGROUND

Olfactory dysfunction represents one of the most frequent symptoms of coronavirus disease 2019, affecting about 70 per cent of patients. However, the pathogenesis of the olfactory dysfunction in coronavirus disease 2019 has not yet been elucidated.

CASE REPORT

This report presents the radiological and histopathological findings of a patient who presented with anosmia persisting for more than three months after infection with severe acute respiratory syndrome coronavirus-2.

CONCLUSION

The biopsy demonstrated significant disruption of the olfactory epithelium. This shifts the focus away from invasion of the olfactory bulb and encourages further studies of treatments targeted at the surface epithelium.

Olfactory bulb magnetic resonance imaging in SARS-CoV-2-induced anosmia in pediatric cases

In this paper, we report three cases of pediatric patients with COVID-19 infection who presented with different symptoms and also anosmia and/or ageusia. The common feature of these 3 patients is that the smell and / or taste disorder developed without nasal symptoms such as nasal congestion, nasal obstruction or rhinorrhea. Although 40% of anosmies contains viral etiologies, COVID- 19 differs from other viral anosmies by the lack of nasal congestion and runny nose. Coronaviruses could invade the brain via the cribriform plate close to the olfactory bulb and the olfactory epithelium. We may expect some structural changes in the olfactory bulb so we evaluated our patient with cranial imaging.

Radiological evidence to changes in the olfactory bulb volume depending on body mass index in the childhood

OBJECTIVE

Energy balance is preserved through the exchange between body weight and adipose tissue across the multi-faceted complex network that is composed of the sensorial, metabolic, and neuro-endocrine circuits. The olfactory control of energy homeostasis is maintained through the interplay between the olfactory bulb (OB) and adipose tissue. While extremely studied, most researches still report controversial results and sensorial regulation of obesity is not fully understood. This study aims to investigate the interplay between olfactory bulb volume (OBV) as a radiological clue of sensorial control and obesity in children.

SUBJECTS AND METHOD

Children (n = 195) were classified into four groups based on body mass index (BMI) percentiles: normal weight (n = 89), overweight (n = 31), obese (n = 32) and morbidly obese (n = 43). OBV were calculated using MRI.

RESULTS

Mean OBV was higher in children with obesity than in those of normal weights. The means of OBV are found higher in the overweight and obese children (43.76 ± 9.50-49.29 ± 8.61 mm³) than in those of morbidly obese (38.23 ± 11.52 mm³) (p < 0.001). In overweight and obese children, a positive correlation were found between the BMI and OBV (r_overweigh = 0.275-r_obese = 0.377), while in the morbidly obese group, there was a negative correlation (r_{severelyobese} = -0.445).

CONCLUSION

This study reveals that OBV is higher in obese children. Also, it shows that there is a positive correlation between OBV and BMI in overweight and obese children and a negative correlation in the morbidly obese group. These radiological bimodal changes in OBV indicate that olfactory control acts to provide energy balance, mediated by positive in the overweight and obese children, negative feedback in the morbidly obese group.

Unexplained repeated pregnancy loss is associated with altered perceptual and brain responses to men's body-odor

Mammalian olfaction and reproduction are tightly linked, a link less explored in humans. Here, we asked whether human unexplained repeated pregnancy loss (uRPL) is associated with altered olfaction, and particularly altered olfactory responses to body-odor. We found that whereas most women with uRPL could identify the body-odor of their spouse, most control women could not. Moreover, women with uRPL rated the perceptual attributes of men's body-odor differently from controls. These pronounced differences were accompanied by an only modest albeit significant advantage in ordinary, non-body-odor-related olfaction in uRPL. Next, using structural and functional brain imaging, we found that in comparison to controls, most women with uRPL had smaller olfactory bulbs, yet increased hypothalamic response in association with men's body-odor. These findings combine to suggest altered olfactory perceptual and brain responses in women experiencing uRPL, particularly in relation to men's body-odor. Whether this link has any causal aspects to it remains to be explored.

Volumetric analysis and morphological assessment of the ascending olfactory pathway in an elasmobranch and a teleost using diceCT

The size (volume or mass) of the olfactory bulbs in relation to the whole brain has been used as a neuroanatomical proxy for olfactory capability in a range of vertebrates, including fishes. Here, we use diffusible iodine-based contrast-enhanced computed tomography (diceCT) to test the value of this novel bioimaging technique for generating accurate measurements of the relative volume of the main olfactory brain areas (olfactory bulbs, peduncles, and telencephalon) and to describe the morphological organisation of the ascending olfactory pathway in model fish species from two taxa, the brownbanded bamboo shark Chiloscyllium punctatum and the common goldfish Carassius auratus. We also describe the arrangement of primary projections to the olfactory bulb and secondary projections to the telencephalon in both species. Our results identified substantially larger olfactory bulbs and telencephalon in C. punctatum compared to C. auratus (comprising approximately 5.2% vs. 1.8%, and 51.8% vs. 11.8% of the total brain volume, respectively), reflecting differences between taxa, but also possibly in the role of olfaction in the sensory ecology of these species. We identified segregated primary projections to the bulbs, associated with a compartmentalised olfactory bulb in C. punctatum, which supports previous findings in elasmobranch fishes. DiceCT imaging has been crucial for visualising differences in the morphological organisation of the olfactory system of both model species. We consider comparative neuroanatomical studies between representative species of both elasmobranch and teleost fish groups are fundamental to further our understanding of the evolution of the olfactory system in early vertebrates and the neural basis of olfactory abilities.

Anosmia in COVID-19 Associated with Injury to the Olfactory Bulbs Evident on MRI

Patients with coronavirus disease 2019 (COVID-19) may have symptoms of anosmia or partial loss of the sense of smell, often accompanied by changes in taste. We report 5 cases (3 with anosmia) of adult patients with COVID-19 in whom injury to the olfactory bulbs was interpreted as microbleeding or abnormal enhancement on MR imaging. The patients had persistent headache (n = 4) or motor deficits (n = 1). This olfactory bulb injury may be the mechanism by which the Severe Acute Respiratory Syndrome coronavirus 2 causes olfactory dysfunction.

Antagonistic odor interactions in olfactory sensory neurons are widespread in freely breathing mice

Odor landscapes contain complex blends of molecules that each activate unique, overlapping populations of olfactory sensory neurons (OSNs). Despite the presence of hundreds of OSN subtypes in many animals, the overlapping nature of odor inputs may lead to saturation of neural responses at the early stages of stimulus encoding. Information loss due to saturation could be mitigated by normalizing mechanisms such as antagonism at the level of receptor-ligand interactions, whose existence and prevalence remains uncertain. By imaging OSN axon terminals in olfactory bulb glomeruli as well as OSN cell bodies within the olfactory epithelium in freely breathing mice, we find widespread antagonistic interactions in binary odor mixtures. In complex mixtures of up to 12 odorants, antagonistic interactions are stronger and more prevalent with increasing mixture complexity. Therefore, antagonism is a common feature of odor mixture encoding in OSNs and helps in normalizing activity to reduce saturation and increase information transfer.

The human olfactory system in two proteinopathies: Alzheimer's and Parkinson's diseases

Alzheimer's and Parkinson's diseases are the most prevalent neurodegenerative disorders. Their etiologies are idiopathic, and treatments are symptomatic and orientated towards cognitive or motor deficits. Neuropathologically, both are proteinopathies with pathological aggregates (plaques of amyloid-β peptide and neurofibrillary tangles of tau protein in Alzheimer's disease, and Lewy bodies mostly composed of α-synuclein in Parkinson's disease). These deposits appear in the nervous system in a predictable and accumulative sequence with six neuropathological stages. Both disorders present a long prodromal period, characterized by preclinical signs including hyposmia. Interestingly, the olfactory system, particularly the anterior olfactory nucleus, is initially and preferentially affected by the pathology. Cerebral atrophy revealed by magnetic resonance imaging must be complemented by histological analyses to ascertain whether neuronal and/or glial loss or neuropil remodeling are responsible for volumetric changes. It has been proposed that these proteinopathies could act in a prion-like manner in which a misfolded protein would be able to force native proteins into pathogenic folding (seeding), which then propagates through neurons and glia (spreading). Existing data have been examined to establish why some neuronal populations are vulnerable while others are resistant to pathology and to what extent glia prevent and/or facilitate proteinopathy spreading. Connectomic approaches reveal a number of hubs in the olfactory system (anterior olfactory nucleus, olfactory entorhinal cortex and cortical amygdala) that are key interconnectors with the main hubs (the entorhinal-hippocampal-cortical and amygdala-dorsal motor vagal nucleus) of network dysfunction in Alzheimer's and Parkinson's diseases.

A novel heterozygous intron mutation in SEMA7A causing kallmann syndrome in a female

Kallmann syndrome (KS) is a rare inherited disorder, which has significantly genotypic and phenotypic heterogeneity. KS is clinically characterized by the combination of hypogonadotropic hypogonadism and hypo/anosmia. At present, there is no relevant report that intron mutation in SEMA7A gene helps induce KS. A 17-year-old Chinese female (46, XX) came to our department due to primary amenorrhea, who actually had hyposmia since her childhood. Hypogonadotropic hypogonadism was then detected. Luteinizing hormone (LH) and follicle-stimulating hormone (FSH) levels were remarkably low. And estradiol level was extremely low. The laboratory test results were consistent with KS. A heterozygous point mutation of intron 13 in SEMA7A (NM_003612.3:c.1640-3C > A) was identified. The patient received the treatment of pulsatile gonadotropin-releasing hormone (GnRH) pump, which could imitate physiological ovarian stimulation, thus resulting in mature follicle and a peak of LH. The patient was injected subcutaneously every 90 min with a dose of 10 µg per pulse, which had bona efficacy. She acquired menarche at about 43 days after the treatment. We firstly report a case of KS caused by a novel mutation site in the intron of SEMA7A gene. We mainly provide insight into the clinical manifestations, genetic diagnosis and treatment of KS.

Spatiotemporal dynamics of odor responses in the lateral and dorsal olfactory bulb

The mammalian olfactory bulb (OB) plays an essential role in odor processing during the perception of smell. Optical imaging of the OB has proven to be a key tool in elucidating the spatial odor mapping and temporal dynamics that underlie higher-order odor processing. Much is known about the activation of olfactory sensory neuron (OSN) glomerular responses in the dorsal olfactory bulb (dOB) during odor presentation. However, the dorsal bulb provides access to only approximately 25% of all glomeruli, and little is known about how the lateral bulb functions during this critical process. Here, we report, for the first time, simultaneous measurements of OSN glomerular activity from both the dOB and the lateral olfactory bulb (lOB), thus describing odor-specific spatial mapping and the temporal dynamics of olfactory input to both the dorsal and lateral bulb. Odor responses in the lateral bulb tended to be most prominent in the dorso-lateral (D-L) region. Lateral glomeruli became active in a dorso-ventral (D-V) sequence upon odor inhalation, unlike the anterio-posterior (A-P) activity wave typical of the dorsal glomeruli. Across the entire D-L bulb, the spatial organization of these dynamics can be explained neither by the purely mechanosensitive dynamics (to breathing clean air) nor by the response amplitudes across glomeruli. Instead, these dynamics can be explained by a combination of zonal receptor distributions, associated OB projections, and air flow paths across the epithelium upon inhalation. Remarkably, we also found that a subset of OSN glomeruli in the lOB was highly sensitive to extranasal air pressure changes, a response type that has not been reported in dorsal glomeruli.

The mammalian olfactory bulb plays an essential role in odor processing during the perception of smell, but most studies have focused on the dorsal olfactory bulb, which contains only a quarter of all glomeruli. In this study, imaging of the lateral olfactory bulb reveals new properties in smell processing.

Normalized averaged range (nAR), a robust quantification method for MPIO-content

Micron-sized paramagnetic iron oxide particles (MPIO) are commonly used as contrast agents in magnetic resonance imaging (MRI) that produce negative contrast enhancement, i.e. darkening, on T2^*-weighted images. However, estimation and quantification of MPIO in vivo is still challenging. This limitation mainly arises from smearing and displacement of the negative contrast of the MPIO, so-called blooming, potentially leading to false-positive detection. Further, the bias field induced by the MR coils also hinders visualization and quantification of the MPIO. To mitigate these drawbacks, a positive contrast image can be generated, for example by using a frequency offset technique, which can significantly improve the accuracy of quantification methods. In this research, we introduce the normalized average range (nAR) as a new way to quantify the relative MPIO content within a study. The method compares the average value of test ROIs to that of a control ROI in range filtered images. The nAR can be used on both positive and negative contrast images. The nAR was tested on agar phantoms containing various MPIO concentrations, and on a rostral migration model for MPIO labeled stem cells in mice. The amount of MPIO was quantified for biased and unbiased data, and both for positive and negative contrast images. In addition, the presence of MPIOs in the olfactory bulb was verified by histology. The results show the nAR can indicate the presence and relative content of MPIO for both negative and positive images. However, the nAR showed slightly higher sensitivity in optimized positive contrast images compared to negative contrast images. In all cases, the bias field played a minor role in the quantification, making debiasing less of a concern. The dependency of the nAR values on the MPIO content in the ROI was further validated histologically. Thus, the nAR provides a robust and reliable tool for quantification of MPIO in mice.

Assessing the feasibility of intranasal radiotracer administration for in brain PET imaging

Introduction

The development of clinically useful tracers for PET imaging is enormously challenging and expensive. The intranasal (IN) route of administration is purported to be a viable route for delivering drugs to the brain but has, as yet, not been investigated for the delivery of PET tracers. If the intranasal (IN) pathway presents a viable option, it extends the PET imaging field by increasing the number of tracers available for human use.

Here we report the results of a rodent study testing the feasibility of the IN route to administer radiotracers for brain PET imaging.

Methods

We used two different, well characterised, brain penetrant radiotracers, [¹⁸F]fluorodeoxyglucose ([¹⁸F]FDG) and [¹⁸F]fallypride, and aimed to evaluate the pharmacokinetics after administration of the tracers via the intranasal route, and contrast this to intravenous administration. Image acquisition was carried out after tracer administration and arterial blood samples were collected at different time intervals, centrifuged to extract plasma and gamma counted. We hypothesised that [brain region]:[plasma] ratios would be higher via the intranasal route as there are two inputs, one directly from the nose to the brain, and another from the peripheral circulation. To assess the feasibility of using this approach clinically, we used these data to estimate radiation dosimetry in humans.

Results

Contrary to our hypothesis, in case of both radiotracers, we did not see a higher ratio in the expected brain regions, except in the olfactory bulb, that is closest to the nose. It appears that the radiotracers move into the olfactory bulb region, but then do not progress further into other brain regions. Moreover, as the nasal cavity has a small surface area, the extrapolated dosimetry estimations for intranasal human imaging showed an unacceptably high level (15 mSv/MBq) of cumulative skin radiation exposure.

Conclusions

Therefore, although an attractive route for brain permeation, we conclude that the intranasal route would present difficulties due to non-specific signal and radiation dosimetry considerations for brain PET imaging.

High-yielding 18F radiosynthesis of a novel oxytocin receptor tracer, a probe for nose-to-brain oxytocin uptake in vivo

A novel Al18F labelled peptide tracer for PET imaging of oxytocin receptor has been accessed through a high radiochemical yield approach. This tracer showed comparable affinity and higher selectivity and stability compared to oxytocin, and was used to demonstrate direct nose-to-brain uptake following intranasal administration, a common yet controversial delivery route for oxytocin-based therapeutics.

fMRI study of the role of glutamate NMDA receptor in the olfactory processing in monkeys

Studies in rodents show that olfactory processing in the principal neurons of olfactory bulb (OB) and piriform cortex (PC) is controlled by local inhibitory interneurons, and glutamate NMDA receptor plays a role in this inhibitory control. It is not clear if findings from studies in rodents translate to olfactory processing in nonhuman primates (NHPs). In this study, the effect of the glutamate NMDA receptor antagonist MK801 on odorant-induced olfactory responses in the OB and PC of anesthetized NHPs (rhesus monkeys) was investigated by cerebral blood volume (CBV) fMRI. Isoamyl-acetate was used as the odor stimulant. For each NHP, sixty fMRI measurements were made during a 4-h period, with each 4-min measurement consisting of a 1-min baseline period, a 1-min odor stimulation period, and a 2-min recovery period. MK801 (0.3 mg/kg) was intravenously delivered 1 hour after starting fMRI. Before MK801 injection, olfactory fMRI activations were observed only in the OB, not in the PC. After MK801 injection, olfactory fMRI activations in the OB increased, and robust olfactory fMRI activations were observed in the PC. The data indicate that MK801 enhances the olfactory responses in both the OB and PC. The enhancement effects of MK801 are most likely from its blockage of NMDA receptors on local inhibitory interneurons and the attenuation of the inhibition onto principal neurons. This study suggests that the mechanism of local inhibitory control of principal neurons in the OB and PC derived from studies in rodents translates to NHPs.

Reduced olfactory bulb volume in depression-A structural moderator analysis

BACKGROUND

Removal of the olfactory bulb (OB) leads to depression like behavior in rodents. A link between depression and olfactory function is also established in humans. We hypothesized that the human OB volume relates to depressive state and tested whether such a potential coherence is moderated by structural alterations in other brain regions.

METHODS

Eighty-three participants (32 patients with major depression and 51 matched healthy controls) underwent structural MR scanning. Individual OB volumes were compared between patients and controls and the impact of depression and comorbidity was analyzed with multiple regression analysis. Whole-brain voxel-based morphometry revealed structures co-varying with both depressive state and OB volume.

RESULTS

The OB volume of patients was significantly reduced and this reduction averaged out at 17% compared to the controls. The OB volume was correlated to the volume of the insula, superior temporal cortex, and amygdala. The independent variables of depression (β = -.37), age (β = -.25), and gender (β = -.40) explained the individual OB volume variation (R2  = .37). The correlation between OB volume and depression was moderated by volumetric reductions in a cluster including the insula and superior temporal gyrus (STG).

CONCLUSIONS

The OB volume relates to depression in humans and to the volume of structures which are critical for salience detection. We assume that a reduced OB volume causes diminished neural olfactory input which facilitates volume reduction in the insula and STG. The OB volume may hence constitute a factor of vulnerability to depression. Olfactory-based deep brain stimulation is discussed as a future therapeutic approach.

Spectrum of Clinical and Associated MR Imaging Findings in Children with Olfactory Anomalies

BACKGROUND AND PURPOSE

The olfactory apparatus, consisting of the bulb and tract, is readily identifiable on MR imaging. Anomalous development of the olfactory apparatus may be the harbinger of anomalies of the secondary olfactory cortex and associated structures. We report a large single-site series of associated MR imaging findings in patients with olfactory anomalies.

MATERIALS AND METHODS

A retrospective search of radiologic reports (2010 through 2014) was performed by using the keyword "olfactory"; MR imaging studies were reviewed for olfactory anomalies and intracranial and skull base malformations. Medical records were reviewed for clinical symptoms, neuroendocrine dysfunction, syndromic associations, and genetics.

RESULTS

We identified 41 patients with olfactory anomalies (range, 0.03-18 years of age; M/F ratio, 19:22); olfactory anomalies were bilateral in 31 of 41 patients (76%) and absent olfactory bulbs and olfactory tracts were found in 56 of 82 (68%). Developmental delay was found in 24 (59%), and seizures, in 14 (34%). Pituitary dysfunction was present in 14 (34%), 8 had panhypopituitarism, and 2 had isolated hypogonadotropic hypogonadism. CNS anomalies, seen in 95% of patients, included hippocampal dysplasia in 26, cortical malformations in 15, malformed corpus callosum in 10, and optic pathway hypoplasia in 12. Infratentorial anomalies were seen in 15 (37%) patients and included an abnormal brain stem in 9 and an abnormal cerebellum in 3. Four patients had an abnormal membranous labyrinth. Genetic testing was performed in 23 (56%) and findings were abnormal in 11 (48%).

CONCLUSIONS

Olfactory anomalies should prompt careful screening of the brain, skull base, and the pituitary gland for additional anomalies. Genetic testing should be considered.

Chemosensory processing in children with attention-deficit/hyperactivity disorder

BACKGROUND

In attention-deficit/hyperactivity disorder (ADHD) not only deficits in dopamine-related cognitive functioning have been found but also a lower dopamine-sensitive olfactory threshold. The aim of the present study was to proof that only olfactory but not trigeminal sensitivity is increased in ADHD. Structural magnetic resonance imaging (MRI) was used to show increased olfactory bulb (OB) volume- a structure which is strongly shaped by olfactory performance through the mechanism of neuroplasticity (e.g. synaptogenesis). To elucidate whether cortical mechanisms are involved in altered olfaction in ADHD, functional MRI (fMRI) was introduced.

METHODS

A total of 18 boys with ADHD and 17 healthy controls (aged 7-12) were included in the study. Olfactory as well as trigeminal detection thresholds were examined. OB sizes were measured by means of structural MRI and an analysis of effective functional (fMRI) coupling of primary olfactory cortex was conducted. The frontal piriform cortex (fPIR) was chosen as seed region because of its importance in processing both trigeminal and olfactory stimuli as well as having profound influence on inner OB-signaling.

RESULTS

Increased olfactory sensitivity as well as an increase in OB volume was found in ADHD. There were no group differences in sensitivity towards a trigeminal stimulus. Compared to healthy controls, the fPIR in ADHD was more positively coupled with structures belonging to the salience network during olfactory and, to a lesser extent, during trigeminal stimulation.

CONCLUSIONS

Olfactory functioning is superior in subjects with ADHD. The observed increase in OB volume may relate to higher olfactory sensitivity in terms of neuroplasticity. During the processing of chemosensory stimuli, the primary olfactory cortex in ADHD is differently coupled to higher cortical structures which might indicate an altered top-down influence on OB structure and function.

Respiratory epithelial adenomatoid hamartoma of the olfactory groove: A report of 4 cases and a review of the literature

Respiratory epithelial adenomatoid hamartoma (REAH) is a rare benign lesion that affects the nasal cavity and paranasal sinuses. We present 4 cases of REAH that involved the olfactory clefts; 1 case was bilateral. Each of the cases was treated surgically, and no recurrence was observed. Most reports have indicated that REAH occurs in the presence of sinonasal inflammation, particularly nasal polyposis, yet all 4 of our cases occurred in the absence of concurrent rhinosinusitis. This suggests that the etiology of REAH is multifactorial. In addition, we review the literature on REAH, and we discuss its presentation, differential diagnosis, radiology, histopathology, and underlying treatment principles.

Computed tomography of the anterior skull base in Kallmann syndrome reveals specific ethmoid bone abnormalities associated with olfactory bulb defects

CONTEXT

Kallmann syndrome (KS) is characterized by congenital hypogonadotropic hypogonadism (CHH) and an impaired sense of smell related to defective development of the olfactory system.

OBJECTIVE

The aim of the study was to use high-resolution computed tomography (CT) to detect specific abnormalities in the ethmoid bone region surrounding the olfactory bulbs in patients with KS.

PATIENTS

Thirty-seven KS patients were compared to normosmic CHH (nCHH) patients (n = 15) and controls (n = 30) of similar age.

DESIGN AND METHODS

We conducted a prospective study in a single referral center. Subjects underwent CT in bone windows with axial, coronal, and sagittal reconstructions centered on the olfactory fossa (OF) and cribriform plate (CP). We characterized the OF structure by measuring OF height, width, and surface area and a series of angles. The CP foramina were counted bilaterally. Olfactory bulb magnetic resonance imaging, performed in parallel, was compared with CT findings.

RESULTS

OF height, width, and surface area were all significantly lower in KS patients than in nCHH patients and controls (P < .0001). KS patients also had wider angles than nCHH patients and controls (P < .0001). KS subjects with olfactory bulb agenesis on magnetic resonance imaging or who harbored KAL1 mutations had the most marked changes in OF measurements and angles. Coronal OF height distinguished KS patients from controls with the best sensitivity and specificity. The mean number of CP foramina was similar in KS, nCHH, and control subjects.

CONCLUSIONS

KS is associated with specific ethmoid bone abnormalities. The preserved number of CP foramina in KS patients suggests that the integrity of olfactory structures is not mandatory for their formation during fetal development or their maintenance in adult life.

Identification of two novel missense mutations in the KAL1 gene in Han Chinese subjects with Kallmann Syndrome

OBJECTIVES

To identify mutations in the KAL1, the KAL2, and PROKR2/PROK2 genes and to characterize phenotypic features in 5 Chinese subjects with Kallmann Syndrome (KS) and 6 subjects with normosmic hypogonadotrophic hypogonadism (NHH) in Taiwan.

DESIGN AND PATIENTS

Five unrelated males (age range 22-52 yr) with clinical manifestations of KS and 6 unrelated males (age range 24-47 yr) with NHH were analyzed. In addition, 5 relatives of KS subjects were also evaluated. Genomic DNA extraction, PCR, and DNA sequence analyses were performed using standard procedures.

RESULTS

The 1st patient had a single missense mutation in his copy of the KAL1 gene, a T→G transversion in codon 134 that results in replacement of cysteine by gly cine. The 2nd affected subject had a single missense mutation in the KAL1 gene, a T→C transition in codon 163 that results in replacement of cysteine by arginine. The 3rd case was hemizygous for a nonsense mutation in codon 424 of exon 9 (c.CGA→TGA) of the KAL1 gene. This mutation predicts a markedly truncated protein. Two of the mutations (p.C134G and p.C163R) we identified in the KAL1 gene are novel.

CONCLUSIONS

We identified 3 mutations, including 2 novel mutations, in the KAL1 gene in patients with KS in Taiwan. These data extend the variety of KAL1 gene mutations in KS and further define the role of the KAL1 protein in olfactory bulb development.

Quantitative magnetic resonance imaging evaluation of the olfactory system in Kallmann syndrome: correlation with a clinical smell test

OBJECTIVES

To measure olfactory bulbs and sulci using dedicated magnetic resonance imaging (MRI) sequences and specific measurement tools in Kallmann syndrome (KS) patients with a well-established genotype and phenotype, as well as correlate MRI findings with a clinical smell test.

METHODS

MRI was performed in 21 patients with KS and 16 healthy volunteers; olfactory dysfunction was assessed using the Smell Identification Test (UPSIT), a qualitative suprathreshold olfaction test. Coronal turbo spin echo T2-weighted and volumetric T1-weighted gradient echo sequences were acquired in a 1.5T system. ImageJ software was used to obtain olfactory bulb volumes and olfactory sulcus depths and lengths. Data were analyzed with SPSS 15.0 and the Kappa index was used to evaluate the agreement between the UPSIT and MRI.

RESULTS

The UPSIT showed 14 patients with anosmia and 6 with moderate hyposmia. Eighteen patients (85%) presented altered rhinencephalon structures in the MRI. Sixteen patients (76%) presented olfactory bulb aplasia (14/16 bilaterally), and these patients presented a total of 16 aplastic sulci. There was moderate agreement between the MRI quantitative evaluation and the UPSIT (overall Kappa = 0.55), but when considering the presence of aplastic bulbs and anosmia, we found almost perfect agreement (Kappa = 0.87). Three patients had normal rhinencephalon structures, including one with a KAL1 gene mutation.

CONCLUSION

Olfactory bulb and sulcus aplasia were the most common findings in KS patients. We objectively demonstrated agreement between MRI findings and the smell test, especially the presence of bulb aplasia and anosmia. Therefore, our findings help ascertain MRI accuracy in the diagnosis of KS, differentiating patients with hypogonadotropic hypogonadism with an apparently normal or difficult to evaluate sense of smell.

Imaging the olfactory tract (cranial nerve #1)

This review paper browses pros and cons of the different radiological modalities for imaging the olfactory tract and highlights the potential benefits and limitation of more recent advances in MR and CT technology. A systematic pictorial overview of pathological conditions affecting olfactory sense is given. Techniques for collecting quantitative data on olfactory bulb volume and on olfactory sulcus depth are described. At last, insights into functional imaging of olfactory sense are shown.

Digital volume tomography (DVT) measurements of the olfactory cleft and olfactory fossa

CONCLUSION

Preoperative imaging is important, because of the small size of the cribriform plate, different anatomical variants of the olfactory fossa in varied patients and unequal width of the cribriform plate in the anterior and posterior third.

OBJECTIVE

Digital volume tomography (DVT) is a rather new imaging technique for the diagnosis of diseases of paranasal sinuses. This technology is dedicated to the evaluation of the distinctive structures of the anterior skull base due to the high resolution of the DVT. Based on the Keros classification this anatomic area was analyzed radiologically and also in relation to the uncinate process.

METHODS

The investigation was performed on 111 patients. The Accu-I-tomo F17 was used. Patients with total nasal polyposis and patients who had undergone sinus surgery were excluded from the study.

RESULTS

Keros type I was found in 11.25% of the patients, type II in 68.05% and type III in 20.7%. Significant asymmetry of the olfactory fossa was identified in nine patients (8.1%). The width of the olfactory cleft varied from 0 to 3.25 mm. No relation between Keros type and a particular onset of the uncinate process to orbit, skull base or middle turbinate could be detected.

Enduring effects of infant memories: infant odor-shock conditioning attenuates amygdala activity and adult fear conditioning

BACKGROUND

Early life adverse experience alters adult emotional and cognitive development. Here we assess early life learning about adverse experience and its consequences on adult fear conditioning and amygdala activity.

METHODS

Neonatal rats were conditioned daily from 8-12 days-old with paired odor (conditioned stimulus, CS) .5mA shock, unpaired, odor-only, or naive (no infant conditioning). In adulthood, each infant training group was divided into three adult training groups: paired, unpaired or odor-only, using either the same infant CS odor, or a novel adult CS odor without or with the infant CS present as context. Adults were cue tested for freezing (odor in novel environment), with amygdala (14)C 2-DG autoradiography and electrophysiology assessment.

RESULTS

Infant paired odor-shock conditioning attenuated adult fear conditioning, but only if the same infant CS odor was used. The (14)C 2-DG activity correlated with infant paired odor-shock conditioning produced attenuated amygdala but heightened olfactory bulb activity. Electrophysiological amygdala assessment further suggests early experience causes changes in amygdala processing as revealed by increased paired-pulse facilitation in adulthood.

CONCLUSIONS

This suggests some enduring effects of early life adversity (shock) are under CS control and dependent upon learning for their impact on later adult fear learning.

Surgical anatomy of the cribriform plate and adjacent areas

Continuous improvement of surgical techniques is needed in skull base surgery in order to decrease intraoperative complications during various operations. However, the basis of minimizing damage in the operative field is a comprehensive knowledge of microsurgical anatomy. This article provides a detailed description of the cribriform plate and adjacent areas, based on investigations of over one thousand dried skulls and 225 computerized tomography scans of the anterior skull base. The main anatomic structures and the different types of the cribriform plate are demonstrated on color photographs and identified on CT scans as well. The variations important in anterior skull base approaches are also discussed and compared with the data found in the literature. The surface anatomy and development of the cribriform plate is described.

Imaging of chemosensory loss

Clinical assessment of olfactory dysfunction can be challenging. Because olfactory disturbances comprise most chemosensory abnormalities with imaging findings, this article focuses on the imaging of smell disorders. This article reviews the normal imaging appearance of the olfactory apparatus, discusses the respective roles of CT and MRI, provides illustrative imaging of typical pathologic lesions, and discusses a clinically based imaging strategy.

Two occult skull base malformations causing recurrent meningitis in a child: a case report

Occult malformations of the skull base are rare anomalies, but can cause severe complications such as meningitis. Detailed skull base investigations for detecting cerebrospinal fluid fistulas or celes are often not initiated until after a history of recurrent meningitis. We present a child first seen at the age of 12 with recurrent episodes of bacterial meningitis since early childhood, requiring antibiotic prophylaxis for years. High-resolution computed tomography revealed a chronic sinusitis and a bony defect on the right olfactory groove, while magnetic resonance imaging and CT-cisternography indicated no cerebrospinal fluid fistula or cele at that time. Endonasal surgery for chronic sinusitis was performed with a confirmed bony defect on the right olfactory groove and an olfactory fibre without its sleeve-like dura prolongation running into an adjacent ethmoidal cell, necessitating that it be covered. In the absence of any antibiotics a new episode of meningitis occurred 5 years after surgery. CT-cisternography and magnetic resonance imaging were repeated, now indicating a transclival bony defect with a meningocele in its proximal part, most probably presenting a canalis basilaris medianus. Endonasal surgery confirmed this bony defect after adenoidectomy, and closure was accomplished. No further meningitis has been observed for 2 years. Congenital skull base defects may be difficult to detect, but sufficient surgical closure after their precise delineation is mandatory to prevent infectious endocranial complications. The presence of more than one developmental skull base defect should be considered during careful radiological skull base evaluation, which has to include the clivus in order not to overlook rare basilar malformations.

Recurrence of olfactory groove meningiomas

OBJECTIVE

Despite apparent gross total resection, olfactory groove meningiomas have a high rate of late recurrence (average, 23%). In this retrospective study, we confirmed that the sites of these recurrences are the cranial base and paranasal sinuses. We postulated that these recurrences stem from conservative handling of the underlying invaded bone. Therefore, we analyzed patient outcomes according to the radicality of surgical resection.

METHODS

Fifteen consecutive patients with a diagnosis of olfactory groove meningioma were treated surgically between 1992 and 2001 (nine new cases, six recurrent). Only patients with benign meningiomas were included; atypical and malignant meningiomas were excluded. Surgical resection included the dura and drilling of the underlying bone and resection of involved mucosa. We reviewed each patient's clinical records, radiological studies, sites of recurrence, grade of previous resection, and complications.

RESULTS

Olfactory groove meningiomas invaded the underlying bone in 13 cases. All patients with recurrence had previously undergone a surgical resection corresponding only to Simpson Grade 2, which does not include the removal of underlying invaded bone. The sites of recurrence were in the cranial base or adjacent paranasal sinuses. The time to recurrence varied from 1 to 12 years (average, 7 yr; mean, 8 yr). Three patients had undergone one previous resection, two had undergone two previous resections, and one had undergone four previous operations. The ethmoid sinus was involved in all cases of recurrence, either with the sphenoid sinus or with an intracranial recurrence. Thirteen patients underwent complete resection of underlying bone and the invaded paranasal sinuses, then reconstruction of the anterior fossa. No patient died. There were three instances of cerebrospinal fluid leakage (one requiring operative repair), one case of delayed worsening vision after initial improvement, and two cases of transient cranial nerve palsy (Cranial Nerves III and IV). There was no recurrence at follow-up (average, 3.7 yr; range, 1-7.3 yr).

CONCLUSION

The cranial base and paranasal sinuses are sites of predilection for recurrence of olfactory groove meningiomas. Recurrence is the result of a direct extension attributable to incomplete resection of involved bone and regrowth at the edge of a previous surgical field. Extensive resection of all suspicious underlying bone is a complement to radical removal of these lesions. Reconstruction with a vascularized pericranial flap to prevent cerebrospinal fluid leakage is crucial.

Congenital anosmia

We present two cases demonstrating congenital anosmia. In both cases, magnetic resonance imaging (MRI) has served to highlight an interesting clinical oddity. To date, there has only been one study of the use of MRI in the assessment of patients with congenital anosmia who do not have Kallmann's syndrome.

Olfactory bulb and tract and temporal lobe volumes. Normative data across decades

The sense of smell shows a diminution with age as measured by the University of Pennsylvania Smell Identification Test (UPSIT). To ascertain whether the volumes of the olfactory bulbs and tracts (OBTs) and the temporal lobes (TL) declined in parallel to smell function, we examined 36 individuals from ages 22 to 78 who did not complain of any loss of the sense of smell using magnetic resonance (MR) imaging. The OBT volumes showed an initial increase to the 4th decade of life and then a decrease with increasing age, while the trend in TL volume was not as dramatic. There was no correlation between OBT or TL volumes with unilateral or total UPSIT scores. The normative data by decades can be used to assess the OBTs of cohorts of patients with neurodegenerative disorders that affect olfaction.

Children who can't smell the coffee: isolated congenital anosmia

Two children with isolated congenital anosmia, a rare syndrome of deficient restricted neuronal migration, are presented with early diagnosis confirmed by standardized smell testing and detailed neuroimaging studies. Recognition of this disorder and its spectrum of presentations provides important insights into the molecular mechanisms underlying the development of the olfactory system.

Evidence for olfactory function in utero

Pregnant rats received 2-[14C]deoxy-D-glucose (2DG) intravenously on the last day of gestation, and their fetuses were delivered 1 hour later by cesarean section. Fetal brains showed high 2DG uptake spread throughout the accessory olfactory bulb and little or no differential uptake in the main olfactory bulb. These findings demonstrate that functional activity occurs in the accessory olfactory bulb in utero and suggest that the accessory olfactory system may be the pathway by which fetal rats detect the odor quality of their intrauterine milieu.