A new surgical technique to increase airflow in the olfactory cleft: superior turbinate lateralization procedure.

BACKGROUND: The olfactory cleft (OC) is the most important anatomical site for the maintenance of olfactory function. Obstruction of airflow in the OC by various conditions, such as inflammation, leads to poor olfactory function. Therefore, it is important to increase OC airflow while performing endoscopic sinus surgery (ESS). However, no technique to increase airflow has yet been established. METHODS: We designed a superior turbinate lateralization (STL) procedure that displaces the entire ST bone laterally by eliminating the connection between the posterior ST and the anterior wall of the sphenoid sinus. The effect of the STL procedure was investigated in terms of anatomy and olfactory function. RESULTS: ESS with the STL procedure was performed on seven patients with chronic rhinosinusitis and nasal polyps. The cross-sectional area of the OC at 3 months postoperatively was significantly larger than that before ESS. In addition, the Open Essence test and questionnaires revealed significantly improvements in sense of smell. Airflow in the OC was significantly higher in STL procedure group than in the non-STL procedure group. CONCLUSION: The STL procedure enlarges the bony framework of the OC, and by increasing OC airflow, facilitates the transport of odorants to the olfactory epithelium, thereby improving olfactory perception.

Caloric restriction reduces basal cell proliferation and results in the deterioration of neuroepithelial regeneration following olfactotoxic mucosal damage in mouse olfactory mucosa.

The effects of caloric restriction (CR) on cell dynamics and gene expression in the mouse olfactory neuroepithelium are evaluated. Eight-week-old male C57BL/6 mice were fed either control pellets (104 kcal/week) or CR pellets (67 kcal/week). The cytoarchitecture of the olfactory neuroepithelium in the uninjured condition and its regeneration after injury by an olfactotoxic chemical, methimazole, were compared between mice fed with the control and CR diets. In the uninjured condition, there were significantly fewer olfactory marker protein (OMP)-positive olfactory receptor neurons and Ki67-positive proliferating basal cells at 3 months in the CR group than in the control group. The number of Ki67-positive basal cells increased after methimazole-induced mucosal injury in both the control and the CR groups, but the increase was less robust in the CR group. The recovery of the neuroepithelium at 2 months after methimazole administration was less complete in the CR group than in the control group. These histological changes were region-specific. The decrease in the OMP-positive neurons was prominent in the anterior region of the olfactory mucosa. Gene expression analysis using a DNA microarray and quantitative real-time polymerase chain reaction demonstrated that the expression levels of two inflammatory cytokines, interleukin-6 and chemokine ligand 1, were elevated in the olfactory mucosa of the CR group compared with the control group. These findings suggest that CR may be disadvantageous to the maintenance of the olfactory neuroepithelium, especially when it is injured.

Low CT Attenuation Values of Sinonasal Benign Tumours Relative to the Brainstem Identify Schwannomas.

OBJECTIVES: On computed tomography (CT), sinonasal schwannoma displays as a soft-tissue mass without any distinctive features. Our aim was to define the radiological criteria for distinguishing schwannoma from other sinonasal benign tumours. METHODS: We retrospectively identified consecutive patients who were pathologically diagnosed with benign sinonasal tumours between 2007 and 2016. CT attenuation values were compared between benign tumours and the brainstem. The utilities of demographic factors, clinical factors, and CT parameters for predicting the CT attenuation values of the brainstem were analysed by univariate and multivariate regression. RESULTS: Of the 111 identified cases of benign tumours, the CT attenuation values of tumours and the brainstem were analysed in 36 cases (schwannoma, 4 cases; inverted papilloma, 26; juvenile nasopharyngeal angiofibroma, 3; cavernous haemangioma, 3). The CT attenuation values of the schwannomas were significantly lower than in the brainstem, while those of the other tumours were significantly higher than in the brainstem. No factors affected the CT attenuation values of the brainstem. CONCLUSION: Low CT attenuation values of sinonasal benign tumours relative to the brainstem could distinguish schwannomas from other benign tumours.

Infraorbital Nerve Located Medially to Postoperative Maxillary Cysts: A Risk of Endonasal Surgery.

BACKGROUND/AIMS: This study aimed to examine variations in the location of the infraorbital nerve relative to postoperative maxillary cysts to assess the potential risk of nerve injury during endonasal marsupialization. METHODS: Coronal computed tomography images of 130 patients (162 sides) with postoperative maxillary cysts who visited our clinic between 2003 and 2014 were reviewed from the viewpoint of the anatomical relationship between the infraorbital nerves and cysts. RESULTS: The proportions of the six locations were as follows: upside 45.1% (n = 73), separate 13.0% (n = 21), medial 5.6% (n = 9), lateral 14.2% (n = 23), in-between 7.4% (n = 12), and unevaluable 14.8% (n = 24). The proportion of the cases with a potential risk of infraorbital nerve damage during endoscopic marsupialization, including medial, in-between, and unevaluable locations, was 27.8%. Retrospective chart review revealed that 2 patients with a postoperative maxillary cyst that were unevaluable complained of persistent postoperative hypoesthesia of the cheek. CONCLUSION: The anatomical relationship between the infraorbital nerve and postoperative maxillary cysts varied among patients, with approximately one-fourth of the patients being at risk of infraorbital nerve injury even during endoscopic procedures.

Damage to Olfactory Progenitor Cells Is Involved in Cigarette Smoke-Induced Olfactory Dysfunction in Mice.

Exposure to cigarette smoke is a major cause of olfactory dysfunction. However, the underlying mechanisms by which cigarette smoke interferes with the highly regenerative olfactory nerve system remain unclear. To investigate whether cigarette smoke induces olfactory dysfunction by disrupting cell proliferation and cell survival in the olfactory epithelium (OE), we developed a mouse model of smoking that involved intranasal administration of a cigarette smoke solution (CSS). Immunohistological analyses and behavioral testing showed that CSS administration during a period of 24 days reduced the number of olfactory marker protein-positive mature olfactory receptor neurons (ORNs) in the OE and induced olfactory dysfunction. These changes coincided with a reduction in the number of SOX2(+) ORN progenitors and Ki-67(+) proliferating cells in the basal layer of the OE, an increase in the number of caspase-3(+) apoptotic cells, and an increase in the expression of mRNA for the inflammatory cytokines IL-1ß and IL-6. Notably, the proliferating ORN progenitor population recovered after cessation of treatment with CSS, resulting in the subsequent restoration of mature ORN numbers and olfaction. These results suggest that SOX2(+) ORN progenitors are targets of CSS-induced impairment of the OE, and that by damaging the ORN progenitor population and increasing ORN death, CSS exposure eventually overwhelms the regenerative capacity of the epithelium, resulting in reduced numbers of mature ORNs and olfactory dysfunction.

Denervation of nasal mucosa induced by posterior nasal neurectomy suppresses nasal secretion, not hypersensitivity, in an allergic rhinitis rat model.

The posterior nasal nerve is the dominant source of the parasympathetic, sympathetic, and sensory fibers that innervate the nasal respiratory mucosa. Therefore, a posterior nasal neurectomy (PNN) is thought to induce denervation of the nasal mucosa and relieve the nasal symptoms of allergic rhinitis. However, the underlying mechanisms and therapeutic action of PNN remain unknown. To investigate the impact of PNN-induced denervation of the nasal mucosa on allergic rhinitis, we developed a rat model of PNN and examined the effects of PNN on allergic rhinitis in ovalbumin-sensitized rats. This rat model of PNN was characterized by the depletion of nerve fibers, choline acetyltransferase, and neuropeptides (eg, substance P, calcitonin gene-related peptide, vasoactive intestinal peptide, and neuropeptide Y) in the nasal respiratory mucosa. These animals exhibited nasal gland and goblet cell hypertrophy in the septal mucosa and atrophy of the submucosal gland in the lateral nasal wall, as well as reduced nasal secretion due to deficient acetylcholine synthesis. In an ovalbumin-sensitized model of allergic rhinitis, PNN also induced the depletion of nerve fibers, choline acetyltransferase, and neuropeptides in the nasal mucosa and suppressed nasal secretion. However, PNN did not affect mucosal thickening, eosinophil and mast cell infiltration, interleukin-4 and interferon-γ mRNA expression, and allergic symptoms (ie, sneezing and nasal scratching). These results suggest that the peripheral nerves and corresponding neuropeptides regulate nasal secretion, but not hypersensitivity, in allergic rhinitis, and that allergic rhinitis-related mucosal reactions occur in a highly denervated mucosa after PNN. Posterior nasal neurectomy may be a therapeutic option for the treatment of hyperrhinorrhea, but not allergic rhinitis hypersensitivity.

Assessing volume growth of paranasal sinuses and nasal cavity in children using three-dimensional imaging software.

OBJECTIVE: To investigate the accurate volume changes in the paranasal sinus and nasal cavity with age development, using three-dimensional (3D) imaging software METHODS: Paranasal sinus and nasal cavity volumes from computed tomography (CT) images in patients aged 0-24 years were measured using a 3D model to examine age-related changes. Paranasal sinus and nasal cavity growth were compared between age groups. Additionally, the correlation between body height and paranasal sinus growth was examined. RESULTS: A total of 139 CT scans from 137 patients were analyzed. Volume growth of maxillary, ethmoidal, sphenoid, frontal sinuses, and nasal cavity was observed until 18, 16, 20, 20, and 22 years, respectively. Maxillary sinus rapidly grew at 2-8 and 9-12 years, ethmoid sinus 2-8 and 13-16 years, sphenoid sinus 5-8 years, frontal sinus 2-10 years, and nasal cavity 7-12 years. The median volume after growth completion for maxillary, ethmoidal, sphenoid, frontal sinuses, and nasal cavities was 21,937 mm³, 4868 mm³, 5870 mm³, 3172 mm³, and 15,555 mm³, respectively. The left-right difference in the nasal cavity volume increased with age. Sinus and nasal cavity growth completion was delayed by 2-4 years compared to general height growth. CONCLUSION: Growth of the ethmoid, maxillary, sphenoid, frontal sinus, and nasal cavity was completed in approximately 20 years. Compared to the results shown in reports based primarily on 2D measurements, the ethmoid and sphenoid sinuses and nasal cavity were found to continue to grow until older age than previously thought.

A Case of Coexistent Fungal Rhinosinusitis and Actinomycosis Caused by Gutta-Percha Points Extruded Into the Maxillary Sinus.

Dental materials can stray into the maxillary sinus, causing maxillary sinusitis. We present a case of coexistent fungal rhinosinusitis and actinomycosis caused by gutta-percha points, a core-filling material used for root canal treatment. A 56-year-old man who had undergone root canal treatment with gutta-percha points visited our oral surgery department with complaints of purulent nasal discharge lasting one month. Panoramic radiography confirmed the presence of the foreign body in the left maxillary sinus. As per his wish for tooth preservation, he was referred to our department for the transnasal removal of the material. Nasal endoscopy revealed purulent nasal discharge in the nasal cavity. Computed tomography revealed a soft tissue density lesion filling the left maxillary sinus with a rod-like and spherical radiopaque mass. We performed endoscopic sinus surgery and removed the soft material, in which Candida and actinomycetes were histologically confirmed. Some dental materials containing zinc oxide, such as gutta-percha points, have been reported to cause fungal rhinosinusitis. To our knowledge, there have been no reports of coexisting fungal rhinosinusitis and actinomycosis caused by dental materials extruded into the maxillary sinus. Clinicians should consider the possibility of fungal rhinosinusitis and actinomycosis when removing extruded dental materials.

Endoscopic Endonasal Approach Is Superior to Transcranial Approach for Small to Medium Tuberculum Sellae Meningiomas in Terms of Visual Outcome and Complications: A Retrospective Study in a Single Center.

OBJECTIVE: This study compared the effectiveness of the endoscopic endonasal approach (EEA) with the conventional transcranial approach (TCA) for treating tuberculum sellae meningiomas (TSMs), aiming to identify the superior surgical method and the risk factors affecting outcomes. METHODS: Patients treated for TSM from 1998 to 2023 at our institution were retrospectively analyzed, evaluating patient characteristics, tumor features, outcomes, and complications. A novel grading system for preoperative evaluation of TSMs was proposed. RESULTS: Among 49 patients, 26 underwent EEA and 23 underwent TCA. The maximum diameters were comparable between the groups (mean 22 mm vs. 23 mm). Gross total resection rates were 62% for EEA and 70% for TCA, showing no significant difference. However, postsurgical visual improvement was significantly higher in the EEA group compared with the TCA group (77% vs. 44%; P = 0.020), with fewer complications in the EEA group (8% vs. 35%; P = 0.032). CONCLUSIONS: EEA is a safe and effective treatment approach for small to medium TSMs, with outcomes comparable to TCA in terms of resection but superior in visual improvement and fewer complications. Selection of surgical approach should consider patient and tumor characteristics as well as surgeon experience.

The effect of a first-generation H1-antihistamine on postural control: a preliminary study in healthy volunteers.

First-generation H1-antihistamines are known to cause fatigue and drowsiness, due to their poor receptor selectivity and their high penetration rate of the blood-brain barrier. However, little is known about the effects of first-generation H1-antihistamines on postural stability. The purpose of this study was to evaluate the effects of d-chlorpheniramine on postural stability using posturography with and without foam rubber. A double-blind study with three parallel groups was conducted. Twenty-seven healthy young volunteers (mean age 21.9 years) were recruited and orally administered d-chlorpheniramine, 2 or 4 mg, or placebo. Postural sway was measured every hour up to 8 h after administration. Two-legged stance tasks were performed by each subject in four conditions: eyes open or eyes closed and with or without foam rubber. Inter-group comparisons showed that the group receiving 4-mg d-chlorpheniramine showed significantly larger sway in the eyes open with foam rubber condition (visual and vestibular information available, somatosensory information reduced). Inter-subject analysis in the 4-mg d-chlorpheniramine group showed that the effect of d-chlorpheniramine on postural control was variable. Our results suggest that among the three main sensory systems responsible for postural control (visual, vestibular, and somatosensory), d-chlorpheniramine may have a larger effect on the visual and/or vestibular systems in susceptible individuals.

Techniques in Staining of Rodent and Human Olfactory Tissue.

Staining of olfactory tissue allows for evaluation of the organization of specific cell types within the specimen and allows for assessment in abnormalities of function that may be related to changes in normal tissue architecture. Histochemical staining and immunohistochemical (IHC) techniques are the most common methods for visualizing olfactory epithelium and olfactory bulbs. Here we describe the method of IHC for olfactory tissue utilizing both fluorescent and peroxidase-based methods of visualization.

Predicting synkinesis caused by Bell's palsy or Ramsay Hunt syndrome using machine learning-based logistic regression.

Objective: To investigate whether machine learning (ML)-based algorithms, namely logistic regression (LR), random forest (RF), k-nearest neighbor (k-NN), and gradient-boosting decision tree (GBDT), utilizing early post-onset parameters can predict facial synkinesis resulting from Bell's palsy or Ramsay Hunt syndrome more accurately than the conventional statistics-based LR. Methods: This retrospective study included 362 patients who presented to a facial palsy outpatient clinic. Median follow-up of synkinesis-positive and -negative patients was 388 (range, 177-1922) and 198 (range, 190-3021) days, respectively. Electrophysiological examinations were performed, and the rate of synkinesis in Bell's palsy and Ramsay Hunt syndrome was evaluated. Sensitivity and specificity were assessed using statistics-based LR; and electroneurography (ENoG) value, the difference in the nerve excitability test (NET), and scores of the subjective Yanagihara scaling system were evaluated using early post-onset parameters with ML-based LR, RF, k-NN, and GBDT. Results: Synkinesis rate in Bell's palsy and Ramsay Hunt syndrome was 20.2% (53/262) and 40.0% (40/100), respectively. Sensitivity and specificity obtained with statistics-based LR were 0.796 and 0.806, respectively, and the area under the receiver operating characteristic curve (AUC) was 0.87. AUCs measured using ML-based LR of "ENoG," "difference in NET," "Yanagihara," and all three components ("all") were 0.910, 0.834, 0.711, and 0.901, respectively. Conclusion: ML-based LR model shows potential in predicting facial synkinesis probability resulting from Bell's palsy or Ramsay Hunt syndrome and has comparable reliability to the conventional statistics-based LR. Level of Evidence: 3.

Intracranial aspergilloma mimicking metachronous meningioma following transsphenoidal removal of a tuberculum sellae meningioma: illustrative case.

BACKGROUND: Endoscopic transsphenoidal surgery (eTSS) is a well-established approach for resection of skull-based pathologies such as tuberculum sellae meningiomas; however, central nervous system (CNS) fungal infection is a potential complication, particularly in a patient with concomitant sinusitis. OBSERVATIONS: A 58-year-old woman with a tuberculum sellae meningioma causing progressive visual disturbance and concurrent asymptomatic chronic maxillary sinusitis underwent eTSS. Six months later, a de novo dura-based mass with peripheral edema, which was assumed to be an aggressive metachronous meningioma, developed in the middle cranial fossa. The patient underwent frontotemporal craniotomy for complete resection of the lesion, and subsequent histological examination revealed an aspergilloma. She was then treated with an antifungal agent and endoscopic sinus surgery to clear the sinusitis, and no recurrent fungal infection occurred thereafter. LESSONS: CNS fungal infections may appear as a dura-based mass mimicking meningioma. The current case reiterates the importance of the appropriate management of sinusitis prior to eTSS.

Clinical and electrophysiological findings of facial palsy in a case of hereditary gelsolin amyloidosis.

Hereditary gelsolin amyloidosis (HGA) is an autosomal dominant systemic amyloidosis, characterized by cranial and sensory peripheral neuropathy, corneal lattice dystrophy, and cutis laxa. We report a case of HGA presenting with bilateral facial palsy. A 70-year-old Japanese man presented with slowly progressive bilateral facial palsy and facial twitching, which had started in his 40s. His mother also had the same symptoms due to an unknown cause but rest of the family did not. He showed incomplete facial palsy with no frontal muscle movement and partial movement of the orbicularis oris and orbicularis oculi muscles. The patient showed no synkinesis. Electroneurography revealed symmetric low compound motor action potential amplitude of the orbicularis oris muscle, and a nerve excitability test showed a symmetric increase in the response threshold. Despite the partial voluntary movement of the orbicularis oculi muscle, bilateral blink reflexes were absent. He also showed facial spasms after contraction of the orbicularis oris muscle. Genetic testing revealed a heterozygous c.640G>A mutation (p. Asp214Asn); therefore, the patient was diagnosed with HGA. HGA related facial palsy showed moderate bilateral, upper blanch-dominant axonal degeneration of the facial nerve without reinnervation, and trigeminal nerve neuropathy.

High CT Attenuation Values Relative to the Brainstem Predict Fungal Hyphae Within the Sinus.

Objectives: There is currently no established objective diagnostic indicator for the differentiation of sinus fungal ball (SFB) from unilateral nonfungal chronic sinusitis (UCRS). This study evaluated whether computed tomography (CT) attenuation values relative to those of the brainstem (relative CT number) are useful for differentiating SFB from UCRS. Materials and Methods: Consecutive patients who were pathologically diagnosed with SFB or UCRS between 2013 and 2021 were retrospectively identified. The relative CT numbers of region of interest (ROIs) within the sinuses were compared between the two patient groups. Factors with predictive power for differentiating SFBs from UCRSs were identified by uni/multivariable logistic regression analyses. Results: One hundred and eighty-three patients with unilateral chronic sinusitis were finally analyzed (SFB, 86 cases; UCRS, 97 cases). Regardless of the presence or absence of calcified lesions, the relative CT numbers in SFB were significantly higher than those in UCRS. ROIs showing high relative CT numbers were those where fungal hyphae were present. In the uni/multivariable logistic regression analysis, age (p < 0.001), relative CT number (p < 0.001), and calcification (p = 0.002) had predictive value for distinguishing SFB from UCRS. Within those cases not showing calcification, age (p = 0.004) and relative CT number (p < 0.001) were predictive factors for differentiating SFB from UCRS. A relative CT number >1.5 was significantly associated with SFB (sensitivity, 70%; specificity, 91%), with a significantly larger area under the receiver operating characteristics curve than age. Conclusions: High relative CT numbers within the sinus are strongly associated with the presence of fungal hyphae, and measurement of relative CT number is a powerful adjunctive diagnostic method for distinguishing between SFB and UCRS.

Traumatic facial nerve injury: A case of facial nerve avulsion at the cerebellopontine angle.

Post-traumatic facial nerve paralysis is a common disease, but intracranial facial nerve injury after blunt injury has rarely been reported. We report a case of facial nerve avulsion at the cerebellopontine angle. A 23-year-old female with incomplete right-sided facial nerve palsy and facial spasms presented to our hospital. She had a history of traumatic injury, having fallen off a table and hit her head at the age of 2 years. After the accident, she developed complete right-sided facial nerve palsy and underwent conservative treatment with steroids. A magnetic resonance imaging examination performed 21 years later showed avulsion of the facial nerve at the cerebellopontine angle. Magnetic resonance imaging targeting the facial nerves might provide additional information to computed tomography in cases with poor recovery with conservative treatment.

Odorant metabolism of the olfactory cleft mucus in idiopathic olfactory impairment patients and healthy volunteers.

BACKGROUND: It remains unclear whether the metabolic activity of nasal mucus in the olfactory and respiratory areas is different. Moreover, age- and olfaction-related changes may affect metabolism. METHODS: Hexanal, octanal, and 2-methylbutanal were selected for in vitro metabolism analysis and compared between the olfactory cleft and respiratory mucus of participants < 50-year-old with normal olfaction using gas chromatography mass spectrometry. The metabolic activity of hexanal in the olfactory cleft mucus was further compared between three groups, (1) normal olfaction, age < 50 years old, (2) normal olfaction, age ≥50 years old, and (3) idiopathic olfactory impairment. To characterize the enzyme(s) responsible for aldehyde reduction, we also tested if epalr22897estat and 3,5-dichlorosalicylic acid, types of reductase inhibitors, affect metabolism. RESULTS: Conversion of aldehydes to their corresponding alcohols was observed in the olfactory cleft and respiratory mucus. The metabolic production of hexanol, octanol, and 2-methybutanol was significantly higher in the olfactory cleft mucus than in the respiratory mucus (p < 0.01). The metabolic conversion of hexanal to hexanol in the mucus of the idiopathic olfactory impairment group was significantly lower than that in the age-matched normal olfaction group. Excluding the nicotinamide adenine dinucleotide phosphate (NADPH) regenerating system from the reaction mixture inhibited metabolism. The addition of either epalr22897estat or 3,5-dichlorosalicylic acid did not inhibit this metabolic conversion. CONCLUSIONS: The enzymatic metabolism of odorants in the olfactory cleft mucus is markedly higher than in the respiratory mucus and decreases in patients with idiopathic olfactory impairment.

Heterogeneous distribution of mature olfactory sensory neurons in human olfactory epithelium.

BACKGROUND: The olfactory cleft (OC) comprising the olfactory epithelium (OE) is the most important anatomical location for olfactory function. Endoscopic sinus surgery (ESS) is used to treat diseases related to the OC and improve olfactory dysfunction. However, iatrogenic OE injury occasionally occurs. Comprehensive knowledge of the olfactory region is required to avoid damage to the OE during endoscopic procedures. METHODS: Immunohistochemistry was performed on olfactory mucosa obtained from the unaffected side of olfactory neuroblastoma surgical specimens. The OE was defined as the epithelium containing mature olfactory sensory neurons (OSNs). The distribution and cell kinetics of the OE were examined. RESULTS: The OE was selectively localized to the anterior two-thirds of the superior turbinate (ST) and in the nasal septum (NS) just opposite to the ST; the OE was not detected within the mucosa of the superior meatus. The density of mature OSNs was high at the ethmoid tegmen but gradually decreased with distance from the ethmoid tegmen. The extent of cell death and proliferation was relatively even across the OE. Analysis of airflow profiles revealed that resection of inferior ST does not decrease airflow to the OC. CONCLUSION: The results indicate that the distribution and degree of differentiation of mature OSNs are heterogenous throughout the OE. Epithelial resection of the anterior or superior ST has the potential to damage olfactory function. Resection of the inferior or posterior ST or widening of the superior meatus is a safer alternative that does not damage mature OSNs or alter airflow to the OC.

Evidence for the spread of SARS-CoV-2 and olfactory cell lineage impairment in close-contact infection Syrian hamster models.

Objectives: Close contact with patients with COVID-19 is speculated to be the most common cause of viral transmission, but the pathogenesis of COVID-19 by close contact remains to be elucidated. In addition, despite olfactory impairment being a unique complication of COVID-19, the impact of SARS-CoV-2 on the olfactory cell lineage has not been fully validated. This study aimed to elucidate close-contact viral transmission to the nose and lungs and to investigate the temporal damage in the olfactory receptor neuron (ORN) lineage caused by SARS-CoV-2. Methods: Syrian hamsters were orally administered SARS-CoV-2 nonvariant nCoV-19/JPN/TY/WK521/2020 as direct-infection models. On day 3 after inoculation, infected and uninfected hamsters were housed in the same cage for 30 minutes. These uninfected hamsters were subsequently assigned to a close-contact group. First, viral presence in the nose and lungs was verified in the infection and close-contact groups at several time points. Next, the impacts on the olfactory epithelium, including olfactory progenitors, immature ORNs, and mature ORNs were examined histologically. Then, the viral transmission status and chronological changes in tissue damage were compared between the direct-infection and close-contact groups. Results: In the close-contact group, viral presence could not be detected in both the nose and lungs on day 3, and the virus was identified in both tissues on day 7. In the direct-infection group, the viral load was highest in the nose and lungs on day 3, decreased on day 7, and was no longer detectable on day 14. Histologically, in the direct-infection group, mature ORNs were most depleted on day 3 (p <0.001) and showed a recovery trend on day 14, with similar trends for olfactory progenitors and immature ORNs. In the close-contact group, there was no obvious tissue damage on day 3, but on day 7, the number of all ORN lineage cells significantly decreased (p <0.001). Conclusion: SARS-CoV-2 was transmitted even after brief contact and subsequent olfactory epithelium and lung damage occurred more than 3 days after the trigger of infection. The present study also indicated that SARS-CoV-2 damages all ORN lineage cells, but this damage can begin to recover approximately 14 days post infection.