Anatomy of the olfactory nerve: A comprehensive review with cadaveric dissection

Changes in olfactory bulb volume and olfactory sulcus depth in COVID-19 infection: an autopsy study

PURPOSE

The pathophysiology of COVID-19 remains unclear. Olfactory dysfunction is one of the neurological symptoms of the disease. There is no evidence to evaluate whether there is a morphometric change in the olfactory pathways. This study aimed to examine the effect of COVID-19 on olfactory center sections through morphometric measurements obtained from autopsy cases.

METHODS

Our study was conducted on 63 autopsy cases (COVID-19 [n = 37], control (non-COVID) [n = 26]) between the ages of 18-80 years who came to Tokat Forensic Medicine Institute. The anatomical structures of the olfactory tracts were determined on the brains removed during routine autopsy. The dimensions of the structures belonging to the olfactory center sections were measured with a precision digital caliper, weights were measured with a precision digital scale, and volumes were measured with a 0.01 cm³ graduated cylinder. The Archimedes principle method was used for volume calculations.

RESULTS

In the autopsy cases examined, it was found that there was a significant decrease in bilateral olfactory bulb (OB) and olfactory tract (OT) volumes in COVID-19 group (p < 0.001). In addition, OB and OT weights were lighter in COVID-19 group on both sides (p < 0.001). The length, width and depth measurements of the examined anatomical structures were found to be shorter in COVID-19 group (p < 0.01).

CONCLUSION

Autopsy findings showed damage in olfactory center sections in COVID-19 group. We believe that knowing the OB and OT morphology in particular will make significant contributions to both clinical approaches and future studies in the pathology of infectious diseases.

Laminar Fluid Ejection for Olfactory Drug Delivery: A Proof of Concept Study

Focal intranasal drug delivery to the olfactory cleft is a promising avenue for pharmaceuticals targeting the brain. However, traditional nasal sprays often fail to deliver enough medication to this specific area. We present a laminar fluid ejection (LFE) method for precise delivery of medications to the olfactory cleft. Using a 3D-printed model of the nasal passages, we determined the precise velocity and angle of insertion needed to deposit fluid at the olfactory cleft. Then, we conducted three proof-of-concept in-vivo imaging studies to confirm olfactory delivery in humans. First, we used Technetium-99 (a radiolabeled tracer) and methylene blue (a laboratory-made dye) to visualize olfactory deposition. Both tracers showed successful deposition. In a separate study, we used functional MRI (fMRI), to compare our LFE method with a conventional nasal spray while delivering insulin. From the fMRI results, we qualitatively observed focal decreases in brain activity in prefrontal cortex following insulin delivery. Overall, these preliminary results suggest that LFE offers a targeted approach to olfactory drug delivery, opening opportunities for access to the brain.Clinical and Translational Impact Statement - Focal deposition at the olfactory cleft is a promising target for delivering medication to the brain. We present in-human tests of a laminar fluid ejection method for intranasal drug delivery and demonstrate improvements over conventional nasal spray.

Visualizing the human olfactory projection and ancillary structures in a 3D reconstruction

Visualizing in 3D the histological microanatomy of the human olfactory projection from the olfactory mucosa in the nasal cavity to the olfactory bulbs in the cranial cavity necessitates a workflow for handling a great many sections. Here, we assembled a 3D reconstruction of a 7.45 cm3 en-bloc specimen extracted from an embalmed human cadaver. A series of 10 µm coronal sections was stained with quadruple fluorescence histology and scanned in four channels. A trained anatomist manually segmented six structures of interest in a subset of the sections to generate the ground truth. Six convolutional neural networks were then trained for automatic segmentation of these structures in 1234 sections. A high-performance computing solution was engineered to register the sections based on the fluorescence signal and segmented structures. The resulting 3D visualization offers several novel didactic opportunities of interactive exploration and virtual manipulation. By extrapolating manual counts of OSNs in a subset of sections to the calculated volume of the envelope of the entire olfactory epithelium, we computed a total of ~2.7 million OSNs in the specimen. Such empirically derived information helps assess the extent to which the organizational principles of the human olfactory projection may differ from those in mice.

Influence of odor environments on cognitive efficiency: A comprehensive review

Cognitive efficiency, characterized by the rapid and accurate processing of information, significantly enhances work and learning outcomes. This efficiency manifests in improved time management, decision-making, learning capabilities, and creativity. While the influence of thermal, acoustic, and lighting conditions on cognitive performance has been extensively studied, the role of olfactory stimuli remains underexplored. Olfactory perception, distinguished by its intensity, speed of perception, and the breadth of stimuli, plays a pivotal role in cognitive efficiency. This review investigates the mechanisms through which odor environments influence cognitive performance. We analyze how odor environments can affect cognitive efficiency through two different scenarios (work and sleep) and pathways (direct and indirect effects). Current research, which mainly focuses on the interplay between odors, emotional responses, and cognitive efficiency through both subjective and objective measures, is thoroughly analyzed. We highlight existing research gaps and suggest future directions for investigating the influence of odor environments on cognitive efficiency. This review aims to establish a theoretical basis for managing and leveraging odor environments in workplace settings.

Olfaction Preservation and Long-Term Outcomes in Patients with Unilateral Endoscopic Resection of Olfactory Neuroblastoma: A Systematic Review and Institutional Experience

BACKGROUND

Endoscopic endonasal surgical resection is an effective therapeutic approach for olfactory neuroblastoma (ONB). Unilateral excision of ONBs with limited extension has been reported with the purpose of preserving olfactory function. We aimed to review implications of surgical management, olfactory preservation feasibility, and survival outcomes in patients who underwent endoscopic unilateral resection of ONB.

METHODS

A systematic literature review was conducted using the search terms [("Olfactory neuroblastoma") OR ("Esthesioneuroblastoma")] AND [("Unilateral resection") OR ("Olfaction preservation")]. Studies reporting cases of unilateral ONB endoscopic resection with postoperative olfaction assessment were included. Concurrently, records of patients who met inclusion criteria at our institution were reviewed retrospectively. The survival and olfactory outcomes were analyzed in both cohorts.

RESULTS

Thirty-three patients were identified in the published literature. Twenty-three (69.7%) reported postoperative olfaction preservation. Olfactory function after surgery did not show an association with Kadish stage (P = 0.128). No evidence of disease was observed at the latest follow-up in this group of patients. Nine patients who met inclusion criteria were identified at our institution. The extent of resection influenced the level of olfaction preservation when cribriform plate and nasal septum resection coexisted (P = 0.05). A single patient at our institution developed recurrence after being lost to follow-up for 22 months.

CONCLUSIONS

Olfaction preservation can be achieved in patients who undergo endoscopic unilateral resection and adjuvant radiotherapy. The extent of resection should aim for negative margins, particularly in the midline. Larger studies are required to assess the risk of contralateral microscopic disease, and, hence, close follow-up is advised.

Comparative ultrastructure of the olfactory system in the East African root rat (Tachyoryctes splendens) and the naked mole rat (Heterocephalus glaber)

The ultrastructure of the olfactory system of most fossorial rodents remains largely unexplored. This study sought to investigate the functional structure of the olfactory mucosa and olfactory bulb of two species of fossorial rodents that have distinct behaviour and ecology, the East African root rat (RR) and the naked mole rat (NMR). Transmission electron microscopy and scanning electron microscopy were employed. The basic ultrastructural design of the olfactory system of the two species was largely comparable. In both species, the olfactory mucosa comprised an olfactory epithelium and an underlying lamina propria. The olfactory epithelium revealed olfactory knobs, cilia and microvilli apically and sustentancular cells, olfactory receptor neurons and basal cells in the upper, middle and basal zones, respectively. The lamina propria was constituted by Bowman's glands, olfactory nerve bundles and vasculature supported by loose connective tissue. Within the olfactory bulb, intracellular and extracellular structures including cell organelles, axons and dendrites were elucidated. Notable species differences were observed in the basal zone of the olfactory epithelium and on the luminal surface of the olfactory mucosa. The basal zone of the olfactory epithelium of the RR consisted of a single layer of flattened electron-dense horizontal basal cells while the NMR had juxtaposed electron-dense and electron-lucent heterogenous cells, an occurrence seen as being indicative of quiescent and highly proliferative states of the olfactory epithelia in the two species, respectively. The olfactory epithelial surface of the NMR comprised an elaborate cilia network that intertwined extensively forming loop-like structures whereas in the RR, the surface was rugged and consisted of finger-like processes and irregular masses. With gross and histological studies showing significant differences in the olfactory structures of the two species, these findings are a further manifestation that the olfactory system of the RR and the NMR have evolved differently to reflect their varied olfactory functional needs.

Unveiling the vulnerability of the human abducens nerve: insights from comparative cranial base anatomy in mammals and primates

The topographic anatomy of the abducens nerve has been the subject of research for more than 150 years. Although its vulnerability was initially attributed to its length, this hypothesis has largely lost prominence. Instead, attention has shifted toward its intricate anatomical relations along the cranial base. Contrary to the extensive anatomical and neurosurgical literature on abducens nerve anatomy in humans, its complex anatomy in other species has received less emphasis. The main question addressed here is why the human abducens nerve is predisposed to injury. Specifically, we aim to perform a comparative analysis of the basicranial pathway of the abducens nerve in mammals and primates. Our hypothesis links its vulnerability to cranial base flexion, particularly around the sphenooccipital synchondrosis. We examined the abducens nerve pathway in various mammals, including primates, humans (N = 40; 60% males; 40% females), and human fetuses (N = 5; 60% males; 40% females). The findings are presented at both the macroscopic and histological levels. To associate our findings with basicranial flexion, we measured the cranial base angles in the species included in this study and compared them to data in the available literature. Our findings show that the primitive state of the abducens nerve pathway follows a nearly flat (unflexed) cranial base from the pontomedullary sulcus to the superior orbital fissure. Only the gulfar segment, where the nerve passes through Dorello's canal, demonstrates some degree of variation. We present evidence indicating that the derived state of the abducens pathway, which is most pronounced in humans from an early stage of development, is characterized by following the significantly more flexed basicranium. Overall, the present study elucidates the evolutionary basis for the vulnerability of the abducens nerve, especially within its gulfar and cavernous segments, which are situated at the main synchondroses between the anterior, middle, and posterior cranial fossae-a unique anatomical relation exclusive to the abducens nerve. The principal differences between the pathways of this nerve and those of other cranial nerves are discussed. The findings suggest that the highly flexed human cranial base plays a pivotal role in the intricate anatomical relations and resulting vulnerability of the abducens nerve.

Olfactory Dysfunction and Alzheimer's Disease: A Review

 Alzheimer's disease is the most common cause of dementia, and it is one of the leading causes of death globally. Identification and validation of biomarkers that herald the onset and progression of Alzheimer's disease is of paramount importance for early reliable diagnosis and effective pharmacological therapy commencement. A substantial body of evidence has emerged demonstrating that olfactory dysfunction is a preclinical symptom of neurodegenerative diseases including Alzheimer's disease. While a correlation between olfactory dysfunction and Alzheimer's disease onset and progression in humans exists, the mechanism underlying this relationship remains unknown. The aim of this article is to review the current state of knowledge regarding the range of potential factors that may contribute to the development of Alzheimer's disease-related olfactory dysfunction. This review predominantly focuses on genetic mutations associated with Alzheimer's disease including amyloid-β protein precursor, presenilin 1 and 2, and apolipoprotein E mutations, that may (in varying ways) drive the cellular events that lead to and sustain olfactory dysfunction.

The olfactory striae: A historical perspective on the inconsistent anatomy of the bulbar projections

Central olfactory pathways (i.e., projection axons of the mitral and tufted cells), and especially olfactory striae, lack common terminology. This is due to their high degree of intra- and interindividual variability, which has been studied in detail over the past century by Beccari, Mutel, Klass, Erhart, and more recently, by Duque Parra et al. These variations led to some confusion about their number and anatomical arrangement. Recent advances in fiber tractography have enabled the precise in vivo visualization of human olfactory striae and the study of their projections. However, these studies require their algorithms to be set up according to the presumed anatomy of the analyzed fibers. A more precise definition of the olfactory striae is therefore needed, not only to allow a better analysis of the results but also to ensure the quality of the data obtained. By studying the various published works on the central olfactory pathways from the first systematic description by Soemmerring to the present, I have traced the different discussions on the olfactory tracts and summarized them here. This review adopts a systematic approach by addressing each stria individually and tracing the historical background of what was known about it in the past, compared to the current knowledge. The chronological and organized approach used provides a better understanding of the anatomy of these essential structures of the olfactory system.

MRI evidence of olfactory system alterations in patients with COVID-19 and neurological symptoms

BACKGROUND AND OBJECTIVE

Despite olfactory disorders being among the most common neurological complications of coronavirus disease 2019 (COVID-19), their pathogenesis has not been fully elucidated yet. Brain MR imaging is a consolidated method for evaluating olfactory system's morphological modification, but a few quantitative studies have been published so far. The aim of the study was to provide MRI evidence of olfactory system alterations in patients with COVID-19 and neurological symptoms, including olfactory dysfunction.

METHODS

196 COVID-19 patients (median age: 53 years, 56% females) and 39 controls (median age 55 years, 49% females) were included in this cross-sectional observational study; 78 of the patients reported olfactory loss as the only neurological symptom. MRI processing was performed by ad-hoc semi-automatic processing procedures. Olfactory bulb (OB) volume was measured on T2-weighted MRI based on manual tracing and normalized to the brain volume. Olfactory tract (OT) median signal intensity was quantified on fluid attenuated inversion recovery (FLAIR) sequences, after preliminary intensity normalization.

RESULTS

COVID-19 patients showed significantly lower left, right and total OB volumes than controls (p < 0.05). Age-related OB atrophy was found in the control but not in the patient population. No significant difference was found between patients with olfactory disorders and other neurological symptoms. Several outliers with abnormally high OT FLAIR signal intensity were found in the patient group.

CONCLUSIONS

Brain MRI findings demonstrated OB damage in COVID-19 patients with neurological complications. Future longitudinal studies are needed to clarify the transient or permanent nature of OB atrophy in COVID-19 pathology.

ACR Appropriateness Criteria® Cranial Neuropathy: 2022 Update

Cranial neuropathy can result from pathology affecting the nerve fibers at any point and requires imaging of the entire course of the nerve from its nucleus to the end organ in order to identify a cause. MRI with and without intravenous contrast is often the modality of choice with CT playing a complementary role. The ACR Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer-reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances in which peer-reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

Olfactory modulation of the medial prefrontal cortex circuitry: Implications for social cognition

Olfactory dysfunction is manifested in a wide range of neurological and psychiatric diseases, and often emerges prior to the onset of more classical symptoms and signs. From a behavioral perspective, olfactory deficits typically arise in conjunction with impairments of cognition, motivation, memory, and emotion. However, a conceptual framework for explaining the impact of olfactory processing on higher brain functions in health and disease remains lacking. Here we aim to provide circuit-level insights into this question by synthesizing recent advances in olfactory network connectivity with other cortical brain regions such as the prefrontal cortex. We will focus on social cognition as a representative model for exploring and critically evaluating the relationship between olfactory cortices and higher-order cortical regions in rodent models. Although rodents do not recapitulate all dimensions of human social cognition, they have experimentally accessible neural circuits and well-established behavioral tests for social motivation, memory/recognition, and hierarchy, which can be extrapolated to other species including humans. In particular, the medial prefrontal cortex (mPFC) has been recognized as a key brain region in mediating social cognition in both rodents and humans. This review will highlight the underappreciated connectivity, both anatomical and functional, between the olfactory system and mPFC circuitry, which together provide a neural substrate for olfactory modulation of social cognition and social behaviors. We will provide future perspectives on the functional investigation of the olfactory-mPFC circuit in rodent models and discuss how to translate such animal research to human studies.

Visualizing in deceased COVID-19 patients how SARS-CoV-2 attacks the respiratory and olfactory mucosae but spares the olfactory bulb

Anosmia, the loss of smell, is a common and often the sole symptom of COVID-19. The onset of the sequence of pathobiological events leading to olfactory dysfunction remains obscure. Here, we have developed a postmortem bedside surgical procedure to harvest endoscopically samples of respiratory and olfactory mucosae and whole olfactory bulbs. Our cohort of 85 cases included COVID-19 patients who died a few days after infection with SARS-CoV-2, enabling us to catch the virus while it was still replicating. We found that sustentacular cells are the major target cell type in the olfactory mucosa. We failed to find evidence for infection of olfactory sensory neurons, and the parenchyma of the olfactory bulb is spared as well. Thus, SARS-CoV-2 does not appear to be a neurotropic virus. We postulate that transient insufficient support from sustentacular cells triggers transient olfactory dysfunction in COVID-19. Olfactory sensory neurons would become affected without getting infected.

Ambiguous "olfactory" terms for anatomic spaces adjacent to the cribriform plate: A publication database analysis and quest for uniformity

A precise nomenclature and terminology is the foundation of communication in Anatomy and related biomedical sciences. The olfactory bulbs and nerves lie above and below the cribriform plate (CP), respectively. Hence, many anatomical landmarks in this region have names adopting the term "olfactory" as qualifiers. Ambiguous use of these "olfactory" terms exists, with some potential repercussions on patient treatments. We performed a publication database analysis to determine the frequency of misuse of names for seven anatomical "olfactory" spaces close to the CP and nasal cavity. We searched PubMed® publications having the keyword "olfactory" in their title or abstract, plus one of seven other keywords: "groove", "fossa", "recess", "cleft", "vestibule", "sulcus", and "cistern". We reviewed all abstracts for accuracy of these terms relative to accepted norms or customary definitions. By February 2020, we found all these keywords in 1255 articles. For the terms olfactory "groove" and "fossa", the number of relevant articles (and percentage of those inaccurately using these terms) were 374 (1.1%), and 49 (8.2%), respectively. All 52 abstracts containing "olfactory" and "vestibule" were irrelevant, relating to the "nasal vestibule" and olfactory function, instead of "olfactory vestibule". Overall, terms used to describe "olfactory" spaces near the CP are seldom ambiguous or inaccurate, but the terms olfactory "groove" and "fossa" are occasionally misused, We propose several new "olfactory" terms for inclusion in the Terminologia Anatomica, and stress the need for uniform nomenclature leading to greater consistency and accuracy in clinical use of anatomical terms containing the word "olfactory" as a descriptor.

C-reactive protein and white matter microstructural changes in COVID-19 patients with encephalopathy

Encephalopathy is a neurological complication of COVID-19. The objective of this exploratory study is to investigate the link between systemic inflammation and brain microstructural changes (measured by diffusion-weighted imaging) in patients with COVID-19 encephalopathy. 20 patients with COVID-19 encephalopathy (age: 67.3 [Formula: see text] 10.0 years; 90% men) hospitalized in the Geneva University Hospitals for a SARS-CoV-2 infection between March and May 2020 were included in this retrospective cohort study. COVID-19 encephalopathy was diagnosed following a comprehensive neurobiological evaluation, excluding common causes of delirium, such as hypoxemic or metabolic encephalopathy. We investigated the correlation between systemic inflammation (measured by systemic C-reactive protein (CRP)) and brain microstructural changes in radiologically normal white matter (measured by apparent diffusion coefficient (ADC)) in nine spatially widespread regions of the white matter previously associated with delirium. Systemic inflammation (CRP = 60.8 ± 50.0 mg/L) was positively correlated with ADC values in the anterior corona radiata (p = 0.0089), genu of the corpus callosum (p = 0.0064) and external capsule (p = 0.0086) after adjusting for patients' age. No statistically significant association between CRP and ADC was found in the other six white matter regions. Our findings indicate high risk of white matter abnormalities in COVID-19 encephalopathy patients with high peripheral inflammatory markers, suggesting aggressive imaging monitoring may be warranted in these patients. Future studies should clarify a possible specificity of the spatial patterns of CRP-white matter microstructure association in COVID-19 encephalopathy patients and disentangle the role of individual cytokines on brain inflammatory mechanisms.

Olfactory nerve sparing technique for anterior skull base meningiomas: how I do it

BACKGROUND

Olfactory function preservation is a desirable objective in anterior skull base (ASB) surgery. The "infracerebral-supraolfactory nerve" corridor is presented.

METHOD

The technique for preserving the olfactory nerves (OlfNs) in anterior ASB meningioma removal involves the following points: deep knowledge of the ASB vascular and meningeal anatomy, precise preoperative planning, wide and sharp dissection of the OlfNs away from the frontal lobes, gravity-aided frontal lobe retraction, Gelfoam-assisted hemostasis on nervous structures, and access to the lesion through an infracerebral-supraolfactory nerve corridor.

CONCLUSIONS

This technique may be a valid option for patients affected by anterior skull base meningiomas with intact preoperative olfactory function.

Anatomical Study of Ethmoidal Foramina and Optic Canal in Endoscopic Trans-Nasal Approach to Anterior Skull Base

BACKGROUND

Surgery to anterior skull base is challenging since complex structures are involved. Injury of olfactory fila and optic nerve may result in postoperative complications. In our study, the authors aim to use computer topographic image to provide a comprehensive anatomical information of anterior skull base and set up a new classification of optic canal (OC) in ethmoid sinus by the degree of bony defect, so as to help surgeons in endoscopic transnasal approach to anterior skull base.

METHOD

Computer topographic angiography images of 112 individuals were reviewed, the measurement was performed on coronal, sagittal, and axis planes after the multiplanar reformation. Nostril and mid-sagittal lines were used to locate the anterior, middle, and posterior part of ethmoidal foramina and orbital opening of OC. Further, the authors classified OC in ethmoidal sinus into 4 types by the degree of the bony defect.

RESULT

Distance between nostril to anterior, middle, and posterior part of ethmoidal foramina and OC are 6.23 ± 0.21, 6.62 ± 0.26, 7.29 ± 0.25, and 7.76 ± 0.41 mm, respectively. Angle between line from nostril to ethmoidal foramina and horizontal plane are 47.50° ± 1.03°, 41.67° ± 1.33°, 37.20° ± 1.34°, respectively. For the 4 types of OC, the percentage is 15.6%, 11.6%, 31.3%, and 41.5%, respectively.

CONCLUSIONS

Our findings provide anatomical information of ethmoidal foramina and OC during endoscopic transnasal approach to anterior skull base, on the basis of some fixed anatomical landmarks. So as to enhance the surgical safety of this procedure and aid in the choice of the appropriate endoscopic equipment for the procedure.

Regional deposition of the allergens and micro-aerosols in the healthy human nasal airways

The nasal cavity is the inlet to the human respiratory system and is responsible for the olfactory sensation, filtering pollutant particulate matter, and humidifying the air. Many research studies have been performed to numerically predict allergens, contaminants, and/or drug particle deposition in the human nasal cavity; however, the majority of these investigations studied only one or a small number of nasal passages. In the present study, a series of Computed Tomography (CT) scan images of the nasal cavities from ten healthy subjects were collected and used to reconstruct accurate 3D models. All models were divided into twelve anatomical regions in order to study the transport and deposition features of different regions of the nasal cavity with specific functions. The flow field and micro-particle transport equations were solved, and the total and regional particle deposition fractions were evaluated for the rest and low activity breathing conditions. The results show that there are large variations among different subjects. The standard deviation of the total deposition fraction in the nasal cavities was the highest for 5 × 10 4 <impaction parameter (IP)< 1.125 × 10 5 with a maximum of 20%. The achieved results highlighted the nasal cavity sections that are more involved in the particle deposition. Particles with IP = 30,000 deposit more in the middle turbinate and nasopharynx areas, while for particles with IP = 300,000, deposition is mainly in the anterior parts (kiesselbach and vestibule regions). For small IP values, the amounts of deposition fractions in different regions of the nasal cavity are more uniform.

What's that smell? A pictorial review of the olfactory pathways and imaging assessment of the myriad pathologies that can affect them

The olfactory pathway is composed of peripheral sinonasal and central sensorineural components. The wide variety of different pathologies that can affect the olfactory pathway reflect this complex anatomical relationship. Localising olfactory pathology can present a challenge to the reporting radiologist. This imaging review will illustrate the normal anatomy of the olfactory system and describe a systematic approach to considering olfactory dysfunction. Key concepts in image interpretation will be demonstrated using examples of olfactory pathway pathologies.

Surgical anatomy and technical nuances of the endoscopic endonasal approach to the anterior cranial fossa

Endoscopic endonasal approaches (EEA) to the skull base have significantly impacted the management of lesions located in the cranial base. Specifically, lesions arising from the anterior cranial fossa, such as pituitary macroadenomas, craniopharyngiomas meningiomas and craniofacial malignancies have benefited from the development of such approaches. Understanding of the anatomy of the anterior fossa is of utmost importance for the successful selection of the approach and application of surgical techniques in EEA. In the current manuscript, we review the most relevant points of surgical anatomy and nuances of the surgical technique of EEA to the anterior fossa. Anatomical landmarks for the transtuberculum transplanum and transcribriform approaches are discussed and a step-by-step description for those approaches is presented. We reinforce that safe and effective application of such techniques follow the same principles of other skull base surgery techniques: mastering of surgical anatomy, adequate case selection, correct instrumentation and surgical experience.

Endoscopic Study of the Distribution of Olfactory Filaments: A Cadaveric Study

Objective

Provide a detailed anatomical description of the olfactory filaments (OF) and their distribution in the nasal cavity through endoscopic endonasal dissection.

Methods

Four cadaveric specimens (8 sides) were used in this study. Nasoseptal (NSM), middle (MTM) and superior turbinate (STM) mucosa dissection was performed to identify the OF and follow them superiorly to the cribriform plate (CP). Measurements of the OF were taken on the NSM, MTM, STM under direct endoscopic visualization. A Student’s T-Test was performed to compare means.

Results

The NSM contained a mean of 11 OF, distributed over surface area (SA) of 173 ± 31 mm2 with the highest density of OF being found at the posterior NSM. The MTM contained a mean 6 OF, covering a mean SA of 77 mm2, with the first OF found 5 mm from the anterior border of the MTM, on average. The STM had a mean 9 OF, with the OF covering a mean SA of 96 mm2. Overall mean OF length was 6 mm. The STM OF were significantly greater in number, with a greater distance from the first OF to last OF (p < 0.05) than the MTM OF.

Summary

The STM and MTM combined were found to have a greater density of OF than the NSM. The STM contains a significantly greater number of OF covering a greater area than the MTM OF. Preservation of the STM and MTM in skull base defect repair, and in routine sinus surgery, can be as beneficial for olfactory function as preservation of the NSM; particularly in CP defect repair. Moreover, our findings indicate that nasoseptal flap harvest performed at least 6 mm from the skull base preserves OF in the NSM. To our knowledge, this is the first anatomical study of the OF through direct endoscopic observation and measurements.

Pediatric glossopharyngeal neuralgia: a comprehensive review

INTRODUCTION

Debilitating facial pain can seriously affect an individual's daily living. Given that the pathophysiology behind neuropathic and myofascial pain is not fully understood, when chronic facial pain goes undiagnosed, it has been proposed that one of the two is the likely cause. Since their discovery, glossopharyngeal neuralgia (GN) and Eagle's syndrome have been considered mostly conditions afflicting the adult population. However, when pediatric patients present with symptoms resembling GN or Eagle's syndrome, physicians are less apt to include these as a differential diagnosis simply due to the low prevalence and incidence in the pediatric population.

MATERIALS AND METHODS

A literature review was performed with the aim to better understand the history of reported cases and to provide a comprehensive report of the anatomical variations that lead to these two conditions as well as the way these variations dictated medical and surgical management. Articles were obtained through Google Scholar and PubMed. Search criteria included key phrases such as pediatric glossopharyngeal neuralgia and pediatric Eagle syndrome. These key phrases were searched independently. PubMed was searched primarily then cross-referenced articles were found via Google Scholar. Results from non-English articles were excluded.

RESULTS

A total of 58 articles were reviewed. Most of the articles focused on adult glossopharyngeal neuralgia, and the majority was comprised of case reports. When searched via PubMed, a total of 16 articles and 2 articles returned for glossopharyngeal neuralgia and Eagle's syndrome, respectively. After criteria selection and cross-referencing, a total of seven articles were found with respect to pediatric glossopharyngeal neuralgia.

CONCLUSIONS

While they are rare conditions, there are multiple etiologies that lead to the debilitating symptoms of GN and Eagle's syndrome. The clinical anatomy proved notable as multiple causes of GN and Eagle's syndrome are due to variation in the anatomy of the neurovascular structures surrounding the glossopharyngeal nerve, an elongated styloid process, a calcified stylohyoid ligament as well as a calcified stylomandibular ligament. Due to the success of different treatment modalities, the treatment of choice is dependent on clinical judgment.

Perioperative olfactory dysfunction in patients with meningiomas of the anteromedial skull base

Olfactory dysfunction represents a main symptom in olfactory groove meningiomas (OGM). Besides this, olfactory function has been sparsely investigated in patients suffering from supratentorial meningiomas. Here, the authors explore pre- and postoperative variables associated with olfactory dysfunction in supratentorial meningioma patients. This is a retrospective study on supratentorial meningioma patients who underwent meningioma resection between January 2015 and January 2016. Preoperative and postoperative olfactory performance was quantified using a lateralized sniffin' stick odor identification test. Meningiomas affecting the olfactory system (n = 23) were compared to meningiomas in other locations among the control group (n = 40). Meningiomas that affected the olfactory system had odds of 3.6 and 3.7 in being associated with ipsilateral (lesional) and bilateral anosmia, respectively. Subgroup analysis revealed that meningiomas causing a midline shift across the frontal base and older age represented risk factors for preoperative anosmia. The odds of experiencing acquired postoperative ipsilateral anosmia were significantly increased in olfactory system affecting meningiomas (OR 11.1). Subgroup analysis highlighted OGMs to represent the predominant location associated with deterioration. General surgical complications predisposed patients to loss of contralateral (OR 12.3) and bilateral olfactory function (OR 27.8). Older age and meningiomas causing a midline shift across the frontal base predispose patients to preoperative olfactory dysfunction. Resection of OGMs and surgical complications are risk factors for postoperative olfactory deterioration to anosmia. Likely, olfactory dysfunction is underrecognized even in OGMs. In OGM surgery, however, preoperative lateralized testing might be critical to selecting an appropriate surgical route to preserve olfactory function. Clin. Anat. 32:524-533, 2019. © 2019 Wiley Periodicals, Inc.