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Neuroradiology Jan 2021As the global COVID-19 pandemic evolves, our knowledge of the respiratory and non-respiratory symptoms continues to grow. One such symptom, anosmia, may be a neurologic...
As the global COVID-19 pandemic evolves, our knowledge of the respiratory and non-respiratory symptoms continues to grow. One such symptom, anosmia, may be a neurologic marker of coronavirus infection and the initial presentation of infected patients. Because this symptom is not routinely investigated by imaging, there is conflicting literature on neuroimaging abnormalities related to COVID-19-related anosmia. We present a novel case of COVID-19 anosmia with definitive olfactory bulb atrophy compared with pre-COVID imaging. The patient had prior MR imaging related to a history of prolactinoma that provided baseline volumes of her olfactory bulbs. After a positive diagnosis of COVID-19 and approximately 2 months duration of anosmia, an MRI was performed that showed clear interval olfactory bulb atrophy. This diagnostic finding is of prognostic importance and indicates that the olfactory entry point to the brain should be further investigated to improve our understanding of COVID infectious pathophysiology.
Topics: Anosmia; Atrophy; COVID-19; Female; Humans; Magnetic Resonance Imaging; Olfactory Bulb; Young Adult
PubMed: 32930820
DOI: 10.1007/s00234-020-02554-1 -
PloS One 2016The changes in olfactory bulb (OB) volume in Parkinson's disease (PD) patients have not yet been comprehensively evaluated. The purpose of this meta-analysis was to... (Meta-Analysis)
Meta-Analysis Review
OBJECTIVE
The changes in olfactory bulb (OB) volume in Parkinson's disease (PD) patients have not yet been comprehensively evaluated. The purpose of this meta-analysis was to explore whether the OB volume was significantly different between PD patients and healthy controls.
METHODS
PubMed and Embase were searched up to March 6, 2015 with no language restrictions. Two independent reviewers screened eligible studies and extracted data on study characteristics and OB volume. Additionally, a systematic review and meta-analysis using a random-effects model were conducted. Publication bias was determined by using funnel plots and Begg's and Egger's tests. Subgroup analyses were performed to assess possible sources of heterogeneity.
RESULTS
Six original case-control studies of 216 PD patients and 175 healthy controls were analyzed. The pooled weighted mean difference (WMD) in the OB volume between the PD patients and the healthy participants was -8.071 for the right OB and -10.124 for the left OB; these values indicated a significant difference among PD patients compared with healthy controls. In addition, a significant difference in the lateralized OB volume was observed in PD patients, with a pooled WMD of 1.618; these results indicated a larger right OB volume than left OB volume in PD patients. In contrast, no difference in the lateralized OB volume was found in healthy controls. No statistical evidence of publication bias among studies was found based on Egger's or Begg's tests. Sensitivity analyses revealed that the results were consistent and robust.
CONCLUSIONS
Overall, both the left and the right OB volume were significantly smaller in PD patients than in healthy controls. However, significant heterogeneity and an insufficient number of studies underscore the need for further observational research.
Topics: Humans; Olfactory Bulb; Organ Size; Parkinson Disease
PubMed: 26900958
DOI: 10.1371/journal.pone.0149286 -
PloS One 2020To introduce new ways to calculate OB volumes, checking their validity and comparing them to already established technique i.e. OB volumetric based on manual...
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.
Topics: Female; Humans; Magnetic Resonance Imaging; Male; Middle Aged; Olfactory Bulb; Organ Size; Smell
PubMed: 33326498
DOI: 10.1371/journal.pone.0243941 -
PloS One 2017The early olfactory system is organized in parallel, with numerous, specialized subsystems established by the modular and topographic projections of sensory inputs....
The early olfactory system is organized in parallel, with numerous, specialized subsystems established by the modular and topographic projections of sensory inputs. While these anatomical sub-systems are in many cases demarcated by well-known marker genes, we stand to learn considerably more about their possible functional specializations from comprehensive, genome-scale descriptions of their molecular anatomy. Here, we leverage the resources of the Allen Brain Atlas (ABA)-a spatially registered compendium of gene expression for the mouse brain-to investigate the early olfactory system's genomic anatomy. We cluster thousands of genes across thousands of voxels in the ABA to derive several novel parcellations of the olfactory system, and concomitantly discover novel sets of enriched, subregion-specific genes that can serve as a starting point for future inquiry.
Topics: Animals; Brain Mapping; Gene Expression Profiling; Gene Expression Regulation; Genetic Markers; Genome; Mice; Mice, Inbred C57BL; Olfactory Bulb
PubMed: 28542411
DOI: 10.1371/journal.pone.0178087 -
AJNR. American Journal of Neuroradiology Mar 2018Although the olfactory bulb volume as assessed with MR imaging is known to reflect olfactory function, it is not always measured during olfactory pathway assessments in...
BACKGROUND AND PURPOSE
Although the olfactory bulb volume as assessed with MR imaging is known to reflect olfactory function, it is not always measured during olfactory pathway assessments in clinical settings. We aimed to evaluate the utility of visual olfactory bulb atrophy and neuropathy analyses using MR imaging in patients with olfactory dysfunction.
MATERIALS AND METHODS
Thirty-four patients who presented with subjective olfactory loss between March 2016 and February 2017 were included. Patients underwent a nasal endoscopic examination, olfactory testing with the Korean Version of the Sniffin' Sticks test, and MR imaging. All patients completed the Sino-Nasal Outcome Test and Questionnaire of Olfactory Disorders. Olfactory bulb atrophy and neuropathy were evaluated on MR images by 2 head and neck radiologists.
RESULTS
The etiology of olfactory loss was chronic rhinosinusitis with/without nasal polyps in 15 (44.1%) patients, respiratory viral infection in 7 (20.6%), trauma in 2 (5.9%), and idiopathic in 10 (29.4%) patients. Although 10 (29.4%) of the 34 patients were normosmic according to the Sniffin' Sticks test, their scores on the other tests were like those of patients who were hyposmic/anosmic according to the Sniffin' Sticks test. However, the detection rate of olfactory bulb atrophy was significantly higher in patients with hyposmia/anosmia than it was in patients with normosmia ( = .002). No difference in olfactory bulb neuropathy was identified among patients with normosmia and hyposmia/anosmia ( = .395).
CONCLUSIONS
MR imaging evaluations of olfactory bulb atrophy can be used to objectively diagnose olfactory dysfunction in patients with subjective olfactory loss.
Topics: Adult; Aged; Atrophy; Female; Humans; Magnetic Resonance Imaging; Male; Middle Aged; Olfaction Disorders; Olfactory Bulb; Young Adult
PubMed: 29269404
DOI: 10.3174/ajnr.A5491 -
Chemical Senses May 2019Post-upper respiratory tract infection related olfactory dysfunction typically occurs due to neural damage after an upper respiratory tract infection associated with a...
Post-upper respiratory tract infection related olfactory dysfunction typically occurs due to neural damage after an upper respiratory tract infection associated with a common cold or influenza. At present, Tokishakuyakusan, a Japanese traditional Kampo medicine, has been found to be effective for post-viral olfactory dysfunction. However, the pharmacodynamics of Tokishakuyakusan in the treatment of post-viral olfactory dysfunction remains unresolved. We investigated the effects of Tokishakuyakusan on the regeneration of olfactory neurons and expression of nerve growth factor (NGF) in neural systems, using in vivo murine studies and in vitro cell culture studies. Eight-week-old BALB/C female mice were fed a pellet diet with or without Tokishakuyakusan. Degeneration of cells in olfactory epithelium was induced by intraperitoneal methimazole injection. Regeneration of olfactory neurons was observed by histological and immunohistochemical procedures. NGF expression in the olfactory bulb was measured by enzyme-linked immunosorbent assay. NGF gene and protein expression were measured using rat primary cultured astrocytes by real-time polymerase chain reaction and enzyme-linked immunosorbent assay. We found that olfactory marker protein, Ki-67, and NGF were more highly expressed in the olfactory epithelium during the regeneration period in mice receiving Tokishakuyakusan. In cultured astrocytes, Tokishakuyakusan as well as its individual components, Atractylodes lancea rhizome and Japanese angelica root, increased NGF expression. Screening assays revealed that NGF production was increased by atractylodin and levistolide A, which are ingredients in Atractylodes lancea rhizome and Japanese angelica root, respectively. These results suggest that Tokishakuyakusan promotes regeneration of olfactory neurons by increasing NGF expression in the olfactory bulb.
Topics: Administration, Oral; Animals; Astrocytes; Cells, Cultured; Drugs, Chinese Herbal; Epithelium; Female; Injections, Intraperitoneal; Methimazole; Mice; Mice, Inbred BALB C; Nerve Growth Factors; Neurons; Olfactory Bulb
PubMed: 30989168
DOI: 10.1093/chemse/bjz023 -
The Journal of Comparative Neurology Jan 2020Detection of chemical cues is important to guide locomotion in association with feeding and sexual behavior. Two neural pathways responsible for odor-evoked locomotion...
Detection of chemical cues is important to guide locomotion in association with feeding and sexual behavior. Two neural pathways responsible for odor-evoked locomotion have been characterized in the sea lamprey (Petromyzon marinus L.), a basal vertebrate. There is a medial pathway originating in the medial olfactory bulb (OB) and a lateral pathway originating from the rest of the OB. These olfactomotor pathways are present throughout the life cycle of lampreys, but olfactory-driven behaviors differ according to the developmental stage. Among possible mechanisms, dopaminergic (DA) modulation in the OB might explain the behavioral changes. Here, we examined DA modulation of olfactory transmission in lampreys. Immunofluorescence against DA revealed immunoreactivity in the OB that was denser in the medial part (medOB), where processes were observed close to primary olfactory afferents and projection neurons. Dopaminergic neurons labeled by tracer injections in the medOB were located in the OB, the posterior tuberculum, and the dorsal hypothalamic nucleus, suggesting the presence of both intrinsic and extrinsic DA innervation. Electrical stimulation of the olfactory nerve in an in vitro whole-brain preparation elicited synaptic responses in reticulospinal cells that were modulated by DA. Local injection of DA agonists in the medOB decreased the reticulospinal cell responses whereas the D2 receptor antagonist raclopride increased the response amplitude. These observations suggest that DA in the medOB could modulate odor-evoked locomotion. Altogether, these results show the presence of a DA innervation within the medOB that may play a role in modulating olfactory inputs to the motor command system of lampreys.
Topics: Animals; Dopamine; Dopamine Agonists; Dopaminergic Neurons; Female; Locomotion; Male; Odorants; Olfactory Bulb; Olfactory Nerve; Petromyzon; Smell
PubMed: 31286519
DOI: 10.1002/cne.24743 -
Particle and Fibre Toxicology Jan 2019Airborne pollution, especially from diesel exhaust (DE), is known to have a negative effect on the central nervous system in exposed human populations. However, the...
BACKGROUND
Airborne pollution, especially from diesel exhaust (DE), is known to have a negative effect on the central nervous system in exposed human populations. However, the consequences of gestational exposure to DE on the fetal brain remain poorly explored, with various effects depending on the conditions of exposure, as well as little information on early developmental stages. We investigated the short-term effects of indirect DE exposure throughout gestation on the developing brain using a rabbit model. We analyzed fetal olfactory tissues at the end of gestation and tested behaviors relevant to pups' survival at birth. Pregnant dams were exposed by nose-only inhalation to either clean air or DE with a content of particles (DEP) adjusted to 1 mg/m by diluting engine exhaust, for 2 h/day, 5 days/week, from gestational day 3 (GD3) to day 27 (GD27). At GD28, fetal olfactory mucosa, olfactory bulbs and whole brains were collected for anatomical and neurochemical measurements. At postnatal day 2 (PND2), pups born from another group of exposed or control female were examined for their odor-guided behavior in response to the presentation of the rabbit mammary pheromone 2-methyl-3-butyn-2-ol (2MB2).
RESULTS
At GD28, nano-sized particles were observed in cilia and cytoplasm of the olfactory sensory neurons in the olfactory mucosa and in the cytoplasm of periglomerular cells in the olfactory bulbs of exposed fetuses. Moreover, cellular and axonal hypertrophies were observed throughout olfactory tissues. Concomitantly, fetal serotoninergic and dopaminergic systems were affected in the olfactory bulbs. Moreover, the neuromodulatory homeostasis was disturbed in a sex-dependent manner in olfactory tissues. At birth, the olfactory sensitivity to 2MB2 was reduced in exposed PND2 pups.
CONCLUSION
Gestational exposure to DE alters olfactory tissues and affects monoaminergic neurotransmission in fetuses' olfactory bulbs, resulting in an alteration of olfactory-based behaviors at birth. Considering the anatomical and functional continuum between the olfactory system and other brain structures, and due to the importance of monoamine neurotransmission in the plasticity of neural circuits, such alterations could participate to disturbances in higher integrative structures, with possible long-term neurobehavioral consequences.
Topics: Air Pollutants; Animals; Animals, Newborn; Behavior, Animal; Dopaminergic Neurons; Female; Fetal Development; Inhalation Exposure; Male; Olfactory Bulb; Pregnancy; Prenatal Exposure Delayed Effects; Rabbits; Serotonergic Neurons; Sex Factors; Synaptic Transmission; Tissue Distribution; Vehicle Emissions
PubMed: 30654819
DOI: 10.1186/s12989-018-0288-7 -
PLoS Biology Apr 2020Interhemispheric connections enable interaction and integration of sensory information in bilaterian nervous systems and are thought to optimize sensory computations....
Interhemispheric connections enable interaction and integration of sensory information in bilaterian nervous systems and are thought to optimize sensory computations. However, the cellular and spatial organization of interhemispheric networks and the computational properties they mediate in vertebrates are still poorly understood. Thus, it remains unclear to what extent the connectivity between left and right brain hemispheres participates in sensory processing. Here, we show that the zebrafish olfactory bulbs (OBs) receive direct interhemispheric projections from their contralateral counterparts in addition to top-down inputs from the contralateral zebrafish homolog of olfactory cortex. The direct interhemispheric projections between the OBs reach peripheral layers of the contralateral OB and retain a precise topographic organization, which directly connects similarly tuned olfactory glomeruli across hemispheres. In contrast, interhemispheric top-down inputs consist of diffuse projections that broadly innervate the inhibitory granule cell layer. Jointly, these interhemispheric connections elicit a balance of topographically organized excitation and nontopographic inhibition on the contralateral OB and modulate odor responses. We show that the interhemispheric connections in the olfactory system enable the modulation of odor response and contribute to a small but significant improvement in the detection of a reproductive pheromone when presented together with complex olfactory cues by potentiating the response of the pheromone selective neurons. Taken together, our data show a previously unknown function for an interhemispheric connection between chemosensory maps of the olfactory system.
Topics: Animals; Animals, Genetically Modified; Calcium; Interneurons; Odorants; Olfactory Bulb; Olfactory Cortex; Olfactory Pathways; Smell; Zebrafish
PubMed: 32310946
DOI: 10.1371/journal.pbio.3000701 -
The Journal of Comparative Neurology Feb 2023Circuit operations of the olfactory bulb are modulated by higher order projections from multiple regions, many of which are themselves targets of bulbar output. Multiple...
Circuit operations of the olfactory bulb are modulated by higher order projections from multiple regions, many of which are themselves targets of bulbar output. Multiple glutamatergic regions project to the olfactory bulb, including the anterior olfactory nucleus (AON), prefrontal cortex (PFC), piriform cortex (PC), entorhinal cortex (EC), and tenia tecta (TT). In contrast, only one region provides GABAergic projections to the bulb. These GABA neurons are located in the horizontal limb of the diagonal band of Broca extending posteriorly through the magnocellular preoptic nucleus to the nucleus of the lateral olfactory bulb. However, it was unclear whether bulbar projecting GABAergic neurons collaterallize projecting to other brain regions. To address this, we mapped collateral projections from bulbar projecting GABAergic neurons using intersectional strategies of viral and traditional tract tracers. This approach revealed bulbar projecting GABAergic neurons show remarkable specificity targeting other primary olfactory cortical regions exhibiting abundant collateral projections into the accessory olfactory bulb, AON, PFC, PC, and TT. The only "nonolfactory" region receiving collateral projections was sparse connectivity to the medial prefrontal orbital cortex. This suggests that basal forebrain inhibitory feedback also modulates glutamatergic feedback areas that are themselves prominent bulbar projection regions. Thus, inhibitory feedback may be simultaneously modulating both synaptic processing of olfactory information in the bulb and associational processing of olfactory information from primary olfactory cortex. We hypothesize that these olfactory GABAergic feedback neurons are a regulator of the entire olfactory system.
Topics: Olfactory Bulb; Brain; Prefrontal Cortex; Preoptic Area; GABAergic Neurons; Olfactory Pathways
PubMed: 36463397
DOI: 10.1002/cne.25434