Implications of the olfactory fossa anatomy in intracranial complications of inferomedial orbital decompression

Two patients with thyroid eye disease underwent inferomedial orbital decompression complicated by a cerebrospinal fluid (CSF) leak. One of the cases developed a postoperative pneumocephalus resolved with conservative measures. In the second case, the CSF leak was managed intraoperatively. In both patients, a computed tomography (CT) scan revealed a pronounced slope of the lateral lamella of the cribriform plate, forming an obtuse angle with its lateral bony extension. When this anatomical disposition of the olfactory fossa (OF) is present, the course of the anterior ethmoidal artery (AEA) is usually embedded in the skull base, and its foramen should not be taken as the upper limit of the transconjunctival ethmoidectomy. The shape and relative height of the olfactory fossa and fovea ethmoidalis, and the course of the AEA should always be assessed before transconjunctival medial decompressions.

Examination of ethmoidal roof regarding Keros and Yenigun classifications in a Turkish population: a computerized tomography study

PURPOSE

Understanding ethmoid roof morphology is crucial to prevent complications in endoscopic sinus surgery. This study aimed to evaluate the morphological properties of the ethmoidal roof regarding gender and age differences using Keros and Yenigun classifications on high-resolution computed tomography images.

METHODS

We retrospectively analyzed 891 high-resolution computed tomography paranasal sinus study images and measured the depth of the cribriform plate in coronal sections and the anterior-posterior length in axial planes. The study retrospectively examined CT images of paranasal sinuses of patients living in the eastern Anatolian region of Turkey.

RESULTS

In both Keros and Yenigun Classifications, the most common class was type 2, and the least common class was type 3. According to Keros et al.'s method, no significant difference was observed between men and women (p = 0.698). However, according to Yenigun et al., the average values of women in terms of the anterior-posterior distance of the ethmoid roof were significantly higher than men (p = 0.001). When examined according to age, a very low, negative correlation was revealed regarding Keros and Yenigun classifications (p = 0.047 and p < 0.001 retrospectively). According to Keros and Yenigun's classification, there was no significant difference between the left and right sides (p = 0.488 and p = 0.919, respectively).

CONCLUSION

The morphological properties of the ethmoidal roof have importance to be considered for preoperative planning. Studying larger patient groups and meta-analyses that gather various research results about this subject might help better understand the ethmoidal roof morphology among populations.

Review of olfactory cleft roof anatomy

Progress in skull-base endoscopic surgery has improved our knowledge of olfactory cleft (OC) anatomy. This article presents a review of current knowledge concerning the OC roof: descriptive anatomy, radiological exploration, and endoscopic observation. The OC is a narrow area in the most superior part of the nasal cavity. Its roof is the thinnest structure separating the nasal cavities from the brain; it comprises three superimposed tissues: nasal mucosa, ethmoid cribriform plate (ECP), and dura mater. The ECP comprises the anterior ECP containing the ethmoidal slit (ES) medially and the cribroethmoidal foramen (CEF) laterally; and the posterior ECP, comprising the olfactory foramina. The OC roof is bordered anteriorly by the nasal bone roof, laterally by the lateral ethmoid masses, and posteriorly by the jugum and anterior wall of the sphenoid sinuses. Imaging is crucial for analyzing this wall, providing precise detailed information on conformation and anatomic relations with adjacent structures such as the anterior ethmoidal artery. Understanding OC roof anatomy and correct interpretation of imaging are essential for safety in present-day functional endoscopic sinus surgery and anterior skull-base oncologic surgery.

Patterns of Pneumatization of the Posterior Nasal Roof

(1) Background: For good surgical performance, sound knowledge of anatomy is required. Although the ethmoid air cells and sphenoid sinuses are subject to a high degree of variation, their possible extensions above the nasal fossa at the posterior end of the cribriform plate of the ethmoid bone (CPEB) were seemingly overlooked. (2) Methods: We retrospectively studied 162 case files from 55 male and 107 female cases, with ages varying from 42 to 80, which were scanned using Cone Beam Computed Tomography. (3) Results: In 56.17% of cases, an unpneumatized CPEB (type I) was found. Nasal roof recesses of ethmoidal origin (type II) were found at the posterior end of the CPEB in 20.37% of cases. Different types of sphenoidal pneumatizations of the posterior end of the CPEB (type III) were found in 22.83% of the cases. Onodi cells projected nasal roof recesses (type IV) in only 10 cases. In all types, nasal roof recesses were found either above the CPEB or within/underneath it. Moreover, such nasal roof recesses were found to be either unilateral, extended contralaterally, or bilateral. (4) Conclusions: As such recesses of the posterior CPEB, previously overlooked, belong to the posterior rhinobase, they should be carefully documented preoperatively to avoid unwanted surgical damage to the olfactory bulb or CSF fistula.

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.

Incidence of anatomical variations according to the International Frontal Sinus Anatomy Classification (IFAC) and their coincidence with radiological sings of opacification

BACKGROUND

The endonasal access to the frontal recess and sinus may be complicated by a variety of anatomical variations. Previous classifications of these variants were characterized by proper names or position information without anatomical reference. The IFAC is intended to simplify the classification of anatomical variations of the frontoethmoidal complex. The aim of this study was to analyse a representative number of sinus CT scans to assess the incidence of anatomical variations according to the IFAC and to compare the results with previous classifications. In addition, the coincidence of complex anatomical variations and radiological sings of opacification was investigated.

METHODOLOGY/PRINCIPAL

Two hundred and forty-nine sinus CT scans were analysed in multiplanar reconstructions. Exclusion criteria were previous operations on the paranasal sinuses, malignant diseases, and an insufficient image quality. All anatomical variants were analysed according to the IFAC criteria. In addition, the coincidence of radiological sings of opacification and the presence of anatomical variations of the frontal recess and sinus were investigated.

RESULTS

The analysis revealed Agger nasi cells in 95% of the CT scans. Supra agger cells (SACs) were detected in 49% and Supra agger frontal cells (SAFCs) in 25% of the data sets. Suprabulla cells (SBCs) were detected in 89% and Supra bulla frontal cells (SBFCs) in 27% of the scans. Supraorbital ethmoid cells (SECs) were detectable in 9% and interfrontal septal cells in 28% of the scans. Despite a partially strong narrowing of the frontal recess, no increased occurrence of radiological sings of opacification could be detected (p > 0.05).

CONCLUSIONS

Anatomical variations in the frontoethmoidal area are very common. According to the IFAC criteria, in 43% of the patients, cells could be detected with pneumatization to or into the frontal sinus. The IFAC is structured more clearly compared to previous classifications due to the anatomical aspect. It represents the most consistent classification regarding surgical planning. Further studies will demonstrate the scientific and clinical value of this classification.

Morphological variation in the anterior cranial fossa

The anterior cranial fossa is an important anatomical landmark in clinical orthodontics consisting of the frontal, ethmoid, and sphenoid bones. The relationships between these bones remain poorly understood. The purposes of the present study were to describe the morphological relationships among the three bones and to discuss the factors contributing to individual variations in adult skulls based on postnatal development. Skulls of 100 Indian adults and 18 Japanese juveniles were observed both macroscopically and using computed tomography images in the median sagittal plane. Three types of relationship were seen among the three bones in adult skulls: (a) a triangular border between ethmoid and sphenoid bones (ethmoid spine), (b) a straight or concave border between ethmoid and sphenoid bones, and (c) frontal bone lying between the ethmoid and sphenoid bones. In the juvenile skull, structures corresponding to those in adults were observed. These three bones comprise the anterior cranial base, each with differing developmental processes, and slight differences in these processes seem to be reflected in the morphological variations seen among adults.

New detailed description of the anterior part of the cribriform plate using anatomic specimens and computed tomography

PURPOSE

Ethmoidal slit (ES) and cribroethmoidal foramen (CF) have been poorly studied, without any radiological description. They may ease cribriform plate's diseases. The objective was to describe the frequency, size, and computed tomography (CT) appearance of these foramina.

METHODS

A two-part anatomoradiological study was performed: first on dry skulls using a surgical microscope and CT, second on patients CT scans. For each, foramina were searched for, described, and measured when possible.

RESULTS

Thirteen dry macerated skulls were studied. The orbitomeatal plane was relevant for studying ES. With microscope, ES and CF were identified in, respectively, 92% and 100% of cases. Using CT, all ES and CF were visible, with a mean length and width of, respectively, 3.9 ± 1.7 mm and 0.9 ± 0.3 mm for ES and 1.6 ± 1 mm and 0.9 ± 0.3 mm for CF. CT scans from 153 patients were reviewed. ES and CF were identified in, respectively, 80% and 91% of cases, with a mean length and width of, respectively, 3.9 ± 0.8 mm and 0.8 ± 0.2 mm for ES.

CONCLUSION

Large-sized ES was found frequently, and were clearly visible in patients CT scans. CF was markedly smaller, but seen in most patient scans. ES and CF could be areas of least resistance in the anterior part of the cribriform plate. CT might be helpful in understanding their pathological implications.

The association of superior attachment of uncinate process with pneumatization of middle turbinate: a computed tomographic analysis

The frontal sinus outflow pathway is complex and can be influenced by the configuration of the uncinate process (UP). The UP can attach superior to the lamina papyracea, skull base, and middle turbinate. The factors associated with superior attachment remain unclear. This study analyzed the relationships between different types of superior UP attachment and characteristics of the surrounding structures including the agger nasi cell, skull base, and middle turbinate. This retrospective study utilized computed tomography images of 836 sides with identifiable sinus structure from 434 Taiwanese patients. Types of superior UP attachment, height of the ethmoid cribriform plate, prevalence of agger nasi cell, and degree of pneumatization of the middle turbinate were analyzed. In the current study, neither the presence of an agger nasi cell nor height of the cribriform plate had significant relationship with superior UP attachment type. However, UP attachment type was statistically significantly associated with pneumatized middle turbinate (PMT) type (p < 0.01). The PMT group had a higher incidence of UP attachment to the middle turbinate (38%) than the non-PMT group (18%). In the extensive PMT group, the incidence of UP attachment to the middle turbinate was high to 49%. In conclusion, superior UP attachment to the middle turbinate was associated with pneumatization of the middle turbinate. The UP has a greater tendency to attach to the middle turbinate in cases with more PMT.

Evaluation of anatomical variation of the crista galli using computed tomography

Pneumatization of the crista galli is a recognized incidental finding on computed tomography (CT), usually with little relevance to the clinical picture. There are, however, notable exceptions: congenital midline nasal defects including nasal dermoids have been seen to track through or near the crista galli. Mucocele development has also been seen. This study aimed to evaluate the variation in crista galli morphology and pneumatization and assess whether specific morphologies occur. A retrospective observational study was undertaken between November 2007 and January 2008. Using coronal and axial reconstructed CT views, images of the head in the region of the paranasal sinuses were assessed. Variations in the crista galli were classified according to their position relative to the cribriform plate and to the degree of pneumatization. Computed tomography findings of the morphology of the crista galli in 99 patients were reviewed and a classification system derived from the findings. Three variations of the position of the base of the crista galli were defined. In 28.3% of subjects the base of the crista galli did not extend below the level of the cribriform plate. In 63.6%, the crista galli extended less than 50% of its height below the cribriform plate and in 8.1% of the scans the crista galli extended more than 50% of its height below the cribriform plate. Pneumatization was noticed in 14.1% of the scans. Our results demonstrate the variation that occurs in the morphology and pneumatization of the crista galli. We hope this knowledge might be of help in preoperative planning of surgical approaches to sites of disease involving the crista galli.

Computed tomographic assessment of lateral lamella of cribriform plate and comparison of depth of olfactory fossa

INTRODUCTION

Endoscopic sinus surgery is an upcoming branch in rhinological practice but with some major risks since it has to play around the skull base area. Lateral lamella of cribriform plate is the thinnest area of the skull base. Thus this study is undertaken to evaluate the height of lateral lamella of cribriform plate and the depth of olfactory fossae by the help of computed tomographic images.

METHODS

Computed tomographic study of 50 patients was done in Advanced Imaging and Diagnostic center, Kathmandu Medical College. Coronal sections at the centre of infra-orbital foramina were taken as reference slide. The height of cribriform plate point was subtracted from the height of medial ethmoidal roof point to measure the length of lateral lamella of cribriform plates on both sides.

RESULTS

The median height of LLCP in 100 slides was 2.8 mm. LLCP height was 0 to 3.9 mm in 86 slides, 4 to 7 mm in 12 slides and greater than 7mm in 2 slides. The LLCP length was greater in right side in 28 (56%) patients and was greater in left side in 19 (38%) patients. It was equal in both sides in only three patients (6%).

CONCLUSIONS

As regards the length of LLCP; 0 to 3.9 mm length was most common. The olfactory fossa depth was more in the right side compared to the left side. Thus, right side is more vulnerable to injury during surgery. Thus adequate caution has to be exercised by the rhinological surgeon during endoscopic sinus surgery.

Sectional anatomy of the olfactory pathways

AIM

The purpose of this study was to provide practical anatomic data for imaging diagnosis of olfactory pathways and operation of nasal cavity and anterior cranial fossae.

METHODS

Sectional anatomy of olfactory pathways were investigated specially on 17 sets of Chinese adult cadavers and 9 sets of serial magnetic resonance (MR) imaging of normal adult on serial transverse, sagittal and coronal sections respectively.

RESULTS

We recognized olfactory bulb, olfactory tract, medial and lateral olfactory striae, olfactory trigone, anterior perforated substance and piriform lobe on transverse, sagittal and coronal sections respectively. On the 5-7 serial coronal sections from crista galli of ethmoid bone to the optic chiasm, the cusp ellipse olfactory bulb and the triangular tract were situated in the shallow part of the olfactory sulcus.

CONCLUSION

The olfactory bulb and olfactory tract lay tightly on the ethmoidal cribriform plate and jugum sphenoidale, in the olfactory cistern of the shallow part of the olfactory sulcus, the ethmoid sinus and sphenoid sinus inferiorly.

[Bulla ethmoidalis uncinata: theoretical and practical implications]

The authors describe the previously unknown morphological structure, bulla ethmoidalis uncinata, located at the medial plate of ethmoidal labyrinth that forms the upper part of the lateral wall of the nasal cavity in the region of middle nasal meatus. It was shown that the absence of semilunar hiatus in the nasal cavity may be responsible for fronto-nasal communication through the infundibular opening or the crooked fronto-nasal duct. The discovery of bulla ethmoidalis uncinata substantially extends our knowledge of the structure of human nasal cavity.

Validity of the frontolateral approach as a minimally invasive corridor for olfactory groove meningiomas

BACKGROUND

Several approaches are described for olfactory groove meningiomas (OGMs) varying from a very wide bifrontal craniotomy to minimally invasive endoscopic techniques. The goal of this study was to evaluate the results of the frontolateral approach for olfactory groove meningioma. Pitfalls related to this corridor will be described. The impact of tumor size and encasement of the anterior cerebral artery complex on the degree of tumor removal will be described on the basis of experience with 18 cases.

METHODS

Eighteen patients with OGM underwent microsurgical removal using the frontolateral approach. A retrospective study was conducted by analyzing clinical data, neuroimaging studies, operative findings, clinical outcome, and degree of tumor removal.

FINDINGS

The patients were classified into group A with tumor size less than 4 cm in diameter (7 out of 18 cases, 38.9%) and group B with tumor size more than 4 cm in diameter (11 out of 18 cases, 61.1%). CSF rhinorrhea was observed in three patients (16.7%). Postoperative left frontal intracerebral hematoma occurred in one patient (5.6%) belonging to group A. In another patient (5.6%) belonging to group B, marked right frontal lobe swelling was evident after dural opening, which necessitated partial right frontal pole resection. Total tumor removal (Simpson grade 1 and 2) was achieved in 14 out of 18 patients (77.8%), while subtotal removal (Simpson grade 3 and 4) was achieved in 4 patients (22.2%). In the 14 patients in whom total removal was achieved, 7 belonged to group A (all 7 patients of group A with 100% removal), while the remaining 7 patients belonged to group B (7 out of 11 patients, 63.6% removal; one of them had anterior cerebral artery complex encasement). The four patients in whom subtotal removal was achieved belonged to group B; three of them showed anterior cerebral artery complex encasement, and one elderly patient had non-extensive paranasal sinus involvement. One patient (5.6%) in group B died from cerebral infarction after subtotal tumor removal with anterior cerebral artery injury during its dissection from the tumor capsule.

CONCLUSION

The frontolateral approach has the advantages of both the pterional and conventional bifrontal approaches. The frontolateral approach allows quick and minimally invasive access to OGMs less than 4 cm in diameter, and also to tumors more than 4 cm in diameter without encasement of the anterior cerebral artery complex. Tumor size more than 4 cm in diameter and encasement of the anterior cerebral artery complex are limiting factors for the frontolateral approach if radical tumor removal is considered.

The nasal septum: an osteometric study of 16 cadaver specimens

Studies of the shape, dimensions, and other morphologic characteristics of the nasal septum are scant in the literature. We conducted a study of 16 male cadavers to measure six osseous components of the nasal septum and to calculate the proportional contribution that each made to the total septal bone surface area. We found a wide range of inter-specimen variations in both categories. It is our hope that a better understanding of nasoseptal anatomy will improve surgical technique.

The ethmo-frontal angle: a new anatomic and radiologic landmark for use in sinus surgery

OBJECTIVE

To identify anatomic and radiologic landmarks to assist with frontal sinus surgery.

STUDY DESIGN

Retrospective review.

SUBJECTS AND METHODS

Sinus CT scans of 50 patients were evaluated with respect to a new radiologic and anatomic landmark, the ethmo-frontal angle (EFA).

RESULTS

Right-sided EFA ranged from 135 to 171 degrees. Left-sided EFA ranged from 136 to 167 degrees. Measurements of both sides displayed a normal distribution. When right and left sides within individuals were compared, there was no correlation to indicate a high degree of variation between any particular patient's right and left side EFA.

CONCLUSION

The EFA is a new landmark to assist otolaryngologists during surgery on and around the frontal sinus. Normal values for this angle have been presented. Surgeons should be aware that asymmetry in a patient's EFA is common, and each side should be examined individually.

Giant olfactory groove meningioma: ophthalmological and cognitive outcome after bifrontal microsurgical approach

OBJECT

Olfactory groove meningiomas arise in the midline along the dura of the cribriform plate and may reach a large size before producing symptoms. We conducted a retrospective study of patients with these lesions focused on pre- and post-operative investigations for ophthalmological, personality and cognitive disturbances.

METHODS

The authors reviewed 36 patients with giant olfactory groove meningiomas surgically treated via a bifrontal approach. Ophthalmological evaluation included visual acuity, fundoscopy and visual fields while psychological evaluation included a Mini-Mental State Examination. Data was collected before, 1 and 12 months after surgery. Formal pre- and post-operative ophthalmological examinations discovered visual deficits in 55.5% of the patients. Within the first month after surgery, improvement of visual acuity and of visual field deficits was observed. In post-operative neuropsychological testing, higher mental functions showed improvement. The most frequent post-operative complication was persistent rhinorrhoea in two patients.

CONCLUSIONS

Results at longest follow up indicate that cognitive changes and visual deficits will improve in patients with giant olfactory groove meningiomas after a bifrontal approach, without additional neurological deficits.

[Image features of fundus after radial optic neurotomy in cats' eyes]

OBJECTIVE

To evaluate the imaging features of cats' optic disc after radial optic neurotomy (RON).

METHODS

Unilateral RON were performed on 10 healthy cats. Optical coherence tomography (OCT) and fundus fluorescein angiography (FFA) were performed on the 1st, 15th, 30th and 90th day after RON.

RESULTS

On the 1st d after the surgery, OCT showed that the depth of the incision reaching the posterior surface of luminal cribrosa, with the appearance of adjacent sensory retinal edema. The edema and thickening of sensory retinal disappeared 15 days after the operation. The depth of incision became shallow 30 days after the operation. On the 90th day, the scar filled the luminal cribrosa and the incision. FFA showed that the 1st d after the operation, blocked fluorescence was striped and retinal vessels leaked near the incision during the vein phase. The incision appeared as a spindle shape with hypofluorescence during the early phase and partial staining during the late phase 15 to 30 days after the operation. On the 90th day, there was obvious scar staining at the site that reached the cribriform and retina.

CONCLUSION

The imaging features of RON are in accord with the reparative process.

Removal of an orbital apex hemangioma using an endoscopic transethmoidal approach: technical note

OBJECTIVE

The posterior orbit contains a number of important and vulnerable structures, including the optic nerve, the ophthalmic artery and vein, and the ocular muscles and their motor nerves, which makes surgical access to the lesion in this region quite difficult. Transfrontal, transfrontal-ethmoidal, and transmaxillary procedures have the disadvantage of possible injuries to a number of nontumor structures, whereas an endoscopic transethmoidal approach is a minimally invasive surgery for the retrobulbar lesions. Retrobulbar cavernous hemangioma was successfully removed by a transethmoidal approach.

METHODS

Tumor removal was performed in a patient with an intraconal cavernous hemangioma of approximately 15 mm in diameter. By a transethmoidal approach, the medial-inferior part of the orbit, as well as the apex of the orbit, were clearly visualized after endonasal ethmoidectomy. After the removal of the medial orbital bone, the orbital periosteum was incised and elevated. By elevating the orbital fat, the tumor could be identified separately from the orbital contents.

RESULTS

Cavernous hemangioma at the orbital apex was removed without complications.

CONCLUSION

An endoscopic transethmoidal approach, which requires no skin incision, is a minimally invasive surgery for retrobulbar orbital tumor, leading to excellent cosmetic results with less bleeding.

Relationship between the superior attachment type of uncinate process and presence of agger nasi cell: a computer-assisted anatomic study

OBJECTIVE

The uncinate process (UP) is an important anatomic landmark in frontal recess surgery. Its superior attachment shows great anatomic variability. The agger nasi (AN) cell is another important structure that affects frontal recess anatomy and there is a close neighborhood between them. The aim of this study was to investigate the relationship between superior attachment type of UP and the presence of AN cell.

STUDY DESIGN

A retrospective anatomical study.

METHOD

Computed tomography scans were evaluated of 486 sides of 243 patients who had had paranasal sinus. In 125 (26%) sides, the superior attachment of the UP could not be identified. In the remaining 361 (74%) sides, the prevalence of superior attachment of UP types and the presence of AN cell in each side were recorded. The results were evaluated with chi2 test.

RESULTS

The AN cell was found in 290 (80.3%) of 361 sides. The prevalence of AN cell according to superior attachment of UP types were 79.6% for type 1/2, 90.1% for type 3, 71.4% for type 4, 86.5% for type 5, and 83.3% for type 6. The presence of AN cell according to superior attachment types of UP was not statistically significant (chi2= 3.54, P = 0.315).

CONCLUSIONS

The AN cell was found to be present in 80.3% of the cases. However, the relationship between the presence of the AN cell and the superior attachment types of UP was not statistically significant.

Orbital morphology in exophthalmos and exorbitism

BACKGROUND

Exophthalmos is a protrusion of the eyeball due to an increase in orbital contents in a normal bony orbit. Exorbitism is a protrusion of the eyeball due to a decrease in capacity of the orbital container, with a normal orbital content volume such as seen in a congenital form termed nonsyndromic exorbitism. High myopia can enhance proptosis. The purpose of this study was to provide values for orbital measurements from computed tomography and to suggest computed tomography criteria for nonsyndromic exorbitism.

METHODS

Seventy-three computed tomography scans were collected (57 of Graves' ophthalmopathy and 16 of nonsyndromic exorbitism). Thirty-two scans from nonproptotic patients constituted a control series. Nine measurements and two indexes, performed on a reference axial computed tomography slice transecting the neuro-ocular plane, were obtained from each scan.

RESULTS

The angle between the sagittal axis and the lateral orbital wall, as well as the width of the ethmoid bone (midinterorbital distance), was found to be more open in the nonsyndromic exorbitism population. A lateral orbital wall angle greater than or equal to 42 degrees and a midinterorbital distance greater than 30 mm were chosen as cutpoints. The association of these two criteria allowed the authors to obtain a sensitivity of 62 percent, a specificity of 78 percent, a positive predictive value of 80 percent, and a negative predictive value of 86 percent for nonsyndromic exorbitism.

CONCLUSIONS

The different mechanisms of globe protrusion have to be taken into account before an orbital expansion/decompression procedure is planned. Only a preoperative morphological analysis of the orbital shape permits a precise analysis of the relative position of the ocular globe and orbital structures, in addition to clinical examination.

Subarachnoid injection of Microfil reveals connections between cerebrospinal fluid and nasal lymphatics in the non-human primate

Based on quantitative and qualitative studies in a variety of mammalian species, it would appear that a significant portion of cerebrospinal fluid (CSF) drainage is associated with transport along cranial and spinal nerves with absorption taking place into lymphatic vessels external to the central nervous system. CSF appears to convect primarily through the cribriform plate into lymphatics associated with the submucosa of the olfactory and respiratory epithelium. However, the significance of this pathway for CSF absorption in primates has never been established unequivocally. In past studies, we infused Microfil into the subarachnoid compartment of numerous species to visualize CSF transport pathways. The success of this method encouraged us to use a similar approach in the non-human primate. Yellow Microfil was injected post mortem into the cisterna magna of 6 years old Barbados green monkeys (Cercopithecus aethiops sabeus, n = 6). Macroscopic and microscopic examination revealed that Microfil was (1) distributed throughout the subarachnoid compartment, (2) located in the perineurial spaces associated with the fila olfactoria, (3) present within the olfactory submucosa, and (4) situated within an extensive network of lymphatic vessels in the nasal submucosa, nasal septum and turbinate tissues. We conclude that the Microfil distribution patterns in the monkey were very similar to those observed in many other species suggesting that significant nasal lymphatic uptake of CSF occurs in the non-human primate.

Scaling of mammalian ethmoid bones can predict olfactory organ size and performance

The relation between size and performance is central for understanding the evolution of sensory systems, and much interest has been focused on mammalian eyes and ears. However, we know very little about olfactory organ size (OOS), as data for a representative set of mammals are lacking. Here, we present a cranial endocast method for estimating OOS by measuring an easily accessible part of the system, the perforated part of the ethmoid bone, through which the primary olfactory axons reach the olfactory bulb. In 16 species, for which relevant data are available, the area of the perforated ethmoid bone is directly proportional to the area of the olfactory epithelium. Thus, the ethmoid bone is a useful indicator enabling us to analyse 150 species, and describe the distribution of OOS within the class Mammalia. In the future, a method using skull material may be applied to fossil skulls. In relation to skull size, humans, apes and monkeys have small olfactory organs, while prosimians have OOSs typical for mammals of their size. Large ungulates have impressive olfactory organs. Relating anatomy to published thresholds, we find that sensitivity increases with increasing absolute organ size.

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.

Sagittal and coronal dimensions of the ethmoid roof: a radioanatomic study

BACKGROUND

Understanding the anatomy of the ethmoid roof is critical to safe surgical outcomes. Normative data regarding the height and slope of this region have been somewhat limited, derived primarily from cadaveric coronal computed tomography (CT) studies. With triplanar imaging programs, precise multidimensional measurements of the ethmoid roof are now possible. We present a radioanatomic study to characterize normative sagittal and coronal dimensions of the ethmoid roof.

METHODS

Bilateral measurements were taken in 100 consecutive sinus CT scans using ThinClient 3D software. In the sagittal plane, the height of the ethmoid roof was measured in quadrants at five equidistant points between the frontal beak and sphenoid face, referencing the nasal floor. In the coronal plane, the ethmoid roof was measured at three points at the level of the anterior ethmoid artery and at two points at the junction of the posterior ethmoid and sphenoid sinuses.

RESULTS

When examined sagittally, the right side showed significantly lower skull base heights in the anterior ethmoid compared with the left side (59.0 mm versus 59.8 mm, p = 0.017; 53.7 mm versus 54.5 mm, p = 0.0004). Coronal measurements of the anterior ethmoid roof showed similar significant differences. The anterior ethmoid roof had greater asymmetries of height compared with the posterior ethmoid roof, which was fairly constant.

CONCLUSION

This study provides numerical correlates to accepted concepts regarding the shape and slope of the ethmoid roof. Differences in height of the skull base between right and left sides, especially in the anterior ethmoid sinus, may be an important surgical consideration. The posterior ethmoid roof appears to be relatively constant and should serve as a reliable surgical landmark.

[Anatomic item of the human ethmoid bone -- bulla ethmoidalis uncinata]

A discovery was made in the N.N. Burdenko Voronezh State Medical Academy patented in 2002 -- earlier unknown anatomic item of human ethmoid bone -- bulla ethmoidalis uncinata. It is a pneumatized conjunction of the large ethmoid vesicle and the uncinate process located on the medial plate of ethmoid labyrinth constituting the upper part of the lateral nasal wall in the region of the middle nasal passage. The discovery concerns the field of medicine, i.e. human topographic anatomy, surgery, otorhinolaryngology.

A radiological anatomic study of the cribriform plate compared with constant structures

BACKGROUND

Understanding of the anterior skull base anatomy is crucial to avoid intracranial violations during endoscopic surgery. The aims of this study were to define the normative data about cribriform plate depth and the relationship between this dimension and the measurements of the adjacent anatomical structures such as middle turbinate length, maximal vertical orbital height and distance between the ethmoid roof and the nasal floor.

PATIENTS AND METHODS

Paranasal computerized tomographic scans of 136 healthy adults were included into the study. The cribriform plate depth compared to the ethmoid roof and the adjacent anatomical structures mentioned above were measured bilaterally.

RESULTS

The maximal vertical orbital height was detected as the most constant anatomic measurement. We found the mean level difference between the ethmoid roof and the cribriform plate as 6.1 +/- 2.3 (range 1-12 mm) on the left side and 6.1 +/- 2.2 (1-15 mm) on the right side. The middle turbinate was significantly longer in the Keros Type I group than in the other groups (p<0.05). Furthermore, the distance between the ethmoid roof and the nasal floor was lowest in the Keros Type I group (p<0.01). The distance between the ethmoid roof and the nasal floor was statistically higher in Keros group 3 among all groups (p<0.01). The deeper the cribriform plate, the higher the nasal cavity.

CONCLUSION

To the best of our knowledge, our study has a unique feature by including the data of the constant anatomical structures comparing with the cribriform plate depth. Since in the group with excessive cribriform plate depth, the middle turbinate was short, care should be taken especially during middle turbinate resections.

Transethmoidal approach to the optic canal: surgical and radiological microanatomy

BACKGROUND

The purpose of the study is to describe anatomic topographic landmarks for transethmoidal approach to optic canal for optic nerve decompression. The study focuses on microsurgical/radiologic anatomies and their relationships in the region of the optic canal and orbit.

METHODS

Human optic canal and related anatomic structures were studied in orbits of 6 formalin preserved adult human cadavers. In addition, anatomic measurements were made with digital vernier caliper on the orbits of 25 adult human skulls. The relation between ethmoidal and sinus was assessed with computed tomography (CT) scan in 25 living human heads needing cranial CT scan for any reason.

RESULTS

The suture on the conjunction of frontal, maxilla, and lacrimal bones with a location in medial side of the orbit was accepted as a landmark. When the measurements were taken from this landmark, the distances to supraorbital margin were: right(R): 16.76 +/- 2.62 mm, left (L): 17.10 +/- 1.97 mm, and to infraorbital margin were R: 20.18 +/- 3.24 mm, L: 18.94 +/- 2.19 mm. The distances to the anterior ethmoidal foramen were R: 19.66 +/- 3.96 mm, L: 19.11 +/- 2.84 mm, and to the posterior ethmoidal foramen were R: 32.01 +/- 2.90 mm, L: 32.62 +/- 3.33 mm. Mean distance between the anterior and posterior ethmoidal foramen were R: 12.55 +/- 3.4 mm, L: 13.51 +/- 4.2 mm. The posterior ethmoidal foramen and optic ring were separated only by the mean distances of R: 5.34 +/- 2.81 mm, L: 4.9 +/- 3.35 mm. The distance from the suture to the distal (orbital) opening of the optic canal was R: 37.35 +/- 2.73 mm, L: 37.52 +/- 3.47 mm and to proximal (intracranial) opening of the canal were R: 49.52 +/- 2.62 mm, L: 50.94 +/- 3.35 mm. The average widths of proximal (intracranial) canal measured were R: 7.43 +/- 1.95 mm, L: 7.38 +/- 2.01 mm and those of distal canal (orbital) were R: 5.12 +/- 1.1 mm, L: 4.95 +/- 1.32 mm. The mean lengths of the optic canal were R: 11.19 +/- 2.68 mm, L: 12.42 +/- 3.38 mm. In radiologic examinations, the mean numbers of anterior group ethmoidal cells were R: 7, L: 6 and those of posterior group ethmoidal cells were R: 4, L: 3. The results of CT demonstrated 7 (14%) Onodi or sphenoethmoidal cells in 50 orbits of living humans.

CONCLUSION

The examination of radiologic anatomy in addition to microanatomy can significantly contribute to preoperative and postoperative evaluation of the patients.

Surgical anatomy of the turbinal wall of the ethmoidal labyrinth

The upper part of the lateral nasal wall is formed by a common structure or conchal lamina that is attached all along the junction between the ethmoidal roof and the cribriform plate. From this continuous conchal lamina, the different ethmoidal turbinates take their origin. All these structures form a well defined wall that encloses the ethmoidal cells medially and that deserves the name of "turbinal wall of the ethmoidal labyrinth". The objectives of this paper were: 1) to precisely define the anatomical landmarks of the turbinal wall of the ethmoidal labyrinth, and 2) to study, from an anatomical point of view, the consequences of the surgical resection of the middle turbinate. We performed an anatomic study on 12 frozen human heads, cut in a median-sagittal plane, and then photographed with a millimetre scale in order to perform several measurements. The surface of the turbinal wall of the ethmoidal labyrinth can range from 6.1 to 11.3 cm2. The resection of the middle turbinate preserves approximately half of the turbinal wall, this being around 4.3 cm2 (range 2.6 to 6.3 cm2). The conchal lamina appears as the noble sensorial element of the turbinal wall. It can be described as a continuous bone plate, grossly rectangular in shape, measuring approximately 1 cm in height and 3.5 cm in length that forms the lateral wall of the olfactory groove. The anatomic study shows that its dimensions can vary from simple to double in different individuals. It seems to us that instead of considering the difference of height between the cribriform plate and the ethmoidal roof (Keros classification), we should consider the vertical height of the conchal lamina as a potential risk factor in ethmoidal surgery.

Coverage of anterior fossa in whole-brain irradiation

PURPOSE

Whole-brain irradiation is indispensable in the treatment of several brain tumors and requires coverage of the entire subarachnoid space. Retrospective studies have revealed frequent recurrences in the frontobasal fossa above the cribriform plate (CP). We sought to determine how accurately the latter could actually be identified on lateral radiographs such as those used for radiotherapy planning.

METHODS AND MATERIALS

The CP was localized by five radiation oncologists and five radiologists on lateral radiographs of 30 human skulls from an anatomic collection. Reference radiographs were acquired under identical conditions except for lead markers pointing to the CP and the ethmoid cells. The targeting accuracy was analyzed.

RESULTS

In 39% (n = 116), the location of the CP was correctly estimated within 2 mm. Mislocations of 2-5, 5-10, and >10 mm were noted in 34% (n = 102), 20% (n = 61), and 7% (n = 21), respectively. Neither specialty nor experience (years of training) exerted a significant influence on targeting accuracy. If the roofs of the ethmoid cells formed prominent bony edges, they were mistaken for the CP in 37%.

CONCLUSION

Lateral radiographs provide insufficient information to locate the CP accurately in whole brain irradiation. Additionally, localization was significantly impaired by prominent ethmoid cells.

Morphological relationship between the cranial base and dentofacial complex obtained by reconstructive computer tomographic images

The aims of this study were to investigate the relationships between the cranial base, including the glenoid fossa and maxillofacial morphology, obtained by three-dimensional (3D) computed tomography (CT). The specimens were 45 Skeletal I and Skeletal II dry skulls of modern Japanese males without marked crowding, anterior crossbite, or maxillofacial asymmetry, which had been preserved in the Tokyo University Museum. To examine the differences in the cranial base and maxilla between two groups classified by the median value of N line-A [N defined as a perpendicular line to Frankfort horizontal (FH) through point N, and N line-A as the distance between N and point A]. The specimens with an N-A line less than 1.5 mm were classified as the small group, and those with an N line-A more than 1.5 mm as the large group. Correlation coefficients showed that S-SE was positively related to N-Ba, S-N, S-Ba, and angleFH to S-Ba, and negatively related to SE-N. Ba-X, Ba-Y and Gf-X showed positive correlation with S-Ba and angleFH to S-Ba. For the small group S-SE was longer, angleFH to S-Ba was larger, and Ba-X, Gf-X, A-X, ANS-X, and PNS-X located more posterior and in addition more inferior in ANS-Y. The evidence suggests that S-SE, which is a main component factor of the anterior cranial base, and the antero-posterior position of glenoid fossa, is related to the position of the maxilla. The length and inclination of the posterior cranial base, which is related to Ba, influenced the position of the glenoid fossa.

Important anatomic variations of the sinonasal anatomy in light of endoscopic surgery: a pictorial review

Advances in surgical techniques and instrumentations, utilization of the imaging tools, and understanding the regional anatomy have served to make functional operations with less complications in the paranasal sinus area. In the context of this article, some of these anatomical structures and their variations were reviewed through images. These structures were as follows: course of the anterior ethmoidal artery; roof of the ethmoid; lamina papyracea; uncinate process; optic nerve; and internal carotid artery.

[Some problems of nontraumatic nasal rhinorrhea]

The paper outlines some issues of nontraumatic nasal liquorrhea. The authors state that in the vast majority of cases, liquorrhea occurs along the passage of olfactory filaments through the perforated lamina. Their morphological studies provide indirect evidence for this statement. Encephalomeningocele through the perforated lamina of the ethmoid bone or Turkish saddle is much more infrequent cause of liquorrhea. The authors have developed 2 methods of surgical treatment: 1) endonasal closure of a fistula and 2) its intracranial closure. With mode 1, the nasal mucosa in the upper nasal passage and roof is destroyed and muscle tamponade is made. This method was used to operate on 66 patients. Liquorrhea recovered in 13 patients. It is less traumatic and less expensive and less effective. With method 2, trepanation is made in the frontal region, the dura mater is dissected, the olfactory bulb is destroyed and the site of the perforated lamina is tamponed with a muscle tissue piece. A total of 23 patients were operated on, a good result was achieved in 22 patients of them. Subsequently liquorrhea did not restore in any case. The method is more traumatic, but more effective. With method 3, if liquorrhea occurs through the Turkish saddle, the procedure to close a fistula corresponds to endonasal plasty, only the site of fistular destruction is the sphenoid sinus. The tip of an aspirator is inserted through the aperture of the sinus, its mucosa is destroyed, thereafter it is tamponed with a muscle flap. Three patients were operated on. Liquorrhea ceased.

The radiological anatomy of the anterior skull base

Two complications dominate the thoughts of any surgeon undertaking functional endoscopic sinus surgery (FESS), namely damage to orbital structures and fractures of the fovea ethmoidalis. To avoid these complications, a detailed knowledge of the paranasal sinus anatomy of the patient is essential. This is usually assessed using preoperative computerized tomography (CT) scans of the paranasal sinuses. Analysis of 151 CT scans, measuring the height of cribriform plate below a supraorbital horizontal and above the hard palate was performed. Variation of shape and take-off angle of the fovea ethmoidalis was also measured. Comparison between left and right sides, and between scans showing radiological features of sinonasal disease and normal scans, was undertaken. Five patterns of fovea ethmoidalis were identified. No statistically significant difference between left and right sides was demonstrable for any parameter, irrespective of pathological status.

Management of the central nasal support complex in naso-orbital ethmoid fractures

Central nasal support structures are frequently injured in patients with naso-orbital ethmoid fractures. Diagnosis of these injuries can be difficult and, to optimally manage them, a thorough understanding of the complex anatomy is essential. The goal of surgical repair is to reestablish the aesthetics and function to this region without complication. Appropriate imaging and classification of the central nasal support injury and classification of the naso-orbital ethmoid fractures must be accomplished prior to formulating a successful treatment plan. This article reviews the anatomy, patient assessment, imaging, and classification systems. Currently accepted management of specific injuries are outlined.

An anatomic classification of the ethmoidal bulla

OBJECTIVE

The ethmoid bone is arguably the most complex and varied osseous structure in the human body. The partitions within form a unique labyrinth of lamellae and spaces from specimen to specimen or, as in this study, from patient to patient. The surgical anatomy of the ethmoid bone, and the ethmoidal bulla in particular, is ill-defined and heretofore largely unclassified. In an attempt to better understand the ethmoid labyrinth, a prospective anatomic study of 107 patients undergoing primary intranasal endoscopic ethmoidectomy was undertaken.

STUDY DESIGN

Two hundred fourteen ethmoidal bullae were dissected intraoperatively with video-documentation obtained in over 90% of cases. Based on these dissections, the compartments or cells formed by the partitioning within the ethmoidal bulla and the respective communication with adjacent spaces were the parameters used to develop the classification system.

SETTING

Private midwestern rhinologic referral practice.

RESULTS

Three main categories of ethmoidal development were identified: simple, compound, and complex. Forty-seven percent of bullae were of the simple type, 26% were compound, and 27% complex. Sixty-eight percent of ethmoidal bullae had a single opening into the hiatus semilunaris superior; 6 (2.8%) ethmoidal bullae had a single anterior opening to the ethmoidal infundibulum. The remaining 28.7% had multiple cells with multiple openings, at least 1 of which opened into the hiatus semilunaris superior 98.4% of the time. There was a cell in the complex bulla opening anteriorly to the ethmoidal infundibulum in 46.5%. In 58% of cases, there was symmetry from side to side.

CONCLUSION

A novel anatomic classification for the ethmoidal bulla is presented, with examples of the 3 types of sinus development encountered. We believe that understanding ethmoid sinus anatomy and potential drainage pathways is a core principle to functional sinus surgery.

[Configuration of ethmoid roof in children 0-14 years of age]

BACKGROUND

Knowledge of the unique anatomy of the nose, paranasal sinuses and skull base, particular concerning dangerously low positioned or deep lying cribriform plates is most important, as functional endoscopic sinus surgery has become an increasingly popular procedure for the management of pediatric sinus disease.

OBJECTIVES AND METHODS

In addition to Keros who studied the ethmoidal roof and cribriform plate in 450 adult specimen and divided them into 3 groups, retrospective analysis in 272 patients between 0 and 14 years was performed by means of coronal CT scans of the paranasal sinuses with a slice thickness of 2 mm. Measurements were carried out in the frontal, middle and dorsal section of the ethmoid.

RESULTS

The depth and width of the fossa olfactoria were significantly less in patients aged 0 - 12 months than in other age groups (p < 0.001). Among the other age groups, beginning at 2 years no differences were found: 14.2 % presented with type I according to Keros, 70.6 % with Keros II and 15.2 % with Keros III. The prevalence of asymmetric position of the ethmoidal roof was 15 % (41 patients). The height of the ethmoidal sinuses consistently increased over the years from 5 - 7 mm to 15 - 20 mm.

CONCLUSION

The current data may serve as a reference for evaluation of normal and abnormal development of the roof of the ethmoid and may be of great value in diagnostic and therapeutic management of pediatric sinus disease. Our data obviously show that the classification into the 3 types of positions of the ethmoid roof and cribriform plate according to Keros is possible in children from the second year of life.

Surgical anatomy of the anterior ethmoidal canal in ethmoid roof

OBJECTIVES/HYPOTHESIS

This study was undertaken to examine three main relationships. First, the distance and angle from the anterior ethmoidal canal to the limen nasi and the sill were measured. Second, the location of the anterior ethmoidal canal was examined in relation to the lamellas and the skull base. Third, the existence of bony defects in the canal and the course of the canal through the anterior cranial fossa were studied.

STUDY DESIGN

This study employed both sagittal computed tomography and cadaver dissection.

METHODS

Seventy sagittally divided heads from randomly chosen Korean adult cadavers were used. Sagittal computed tomography was performed on all specimens. Then they were meticulously dissected under a surgical microscope.

RESULTS

The mean distance and angle between the limen nasi and the anterior ethmoidal canal were 49.0 mm and 54.5 degrees, respectively. The anterior ethmoidal canal was located between the second and third lamella in 61 of 70 cases. In 60 of 70 cases it was attached to the base of the skull, and in the remaining 10 cases it ran 2 to 3 mm below the skull base. When viewed from the superior side, the course of the anterior ethmoidal canal formed a diagonal line from the lateral to the medial side. Partial bony defects of the anterior ethmoidal canal were observed in eight cases, and complete bony defects in none.

CONCLUSION

This study provides surgeons with a better understanding of the anatomy of the anterior ethmoidal canal.

The bulla ethmoidalis: lamella or a true cell?

BACKGROUND

The anterior ethmoidal region, including the bulla ethmoidalis, is the most common area addressed during functional endoscopic sinus surgery. Therefore, a detailed understanding of the bulla is essential for safe and effective surgery.

HYPOTHESIS

Based on a review of historical articles on sinus anatomy and review of the current understanding of sinonasal embryology, it is suggested that the ethmoidal bulla is a "lamella" structure rather than a "cell," as it is widely accepted to be.

OBJECTIVE

To analyze the anatomic conformation and nature of the ethmoidal bulla.

METHODS

Detailed gross anatomic sagittal dissection of 14 sinonasal complexes with special attention to the ethmoidal bulla and surrounding structures and pneumatization tracts.

RESULTS

The ethmoidal bulla consisted of a distinct bony lamella in all cases. The degree of development and pneumatization was variable, ranging from a rudimentary torus to a relatively well-pneumatized "bulla"-like structure. A pneumatization tract originating from the retrobullar recess was present in all specimens. This pneumatization excavated into the lamella, creating the bulla-like appearance as viewed from the middle meatus. However, the bulla was not a discrete individual ethmoid cell as it did not have a complete or discrete posterior bony wall. Rather, the posterior wall of this pneumatization tract was formed by the basal lamella.

CONCLUSION

The ethmoidal bulla lacks a distinct posterior wall and therefore is not a separate cell but rather a bony lamella with an air space behind it. From an anatomic perspective, bulla is perhaps not the best term for this structure.

A comparison of cranial base growth in Class I and Class II skeletal patterns

The purpose of this retrospective longitudinal study was to compare 7 cephalometric measurements of the cranial base in subjects with Class I and Class II skeletal patterns at ages 1 month, 2 years, and 14 years. A sample of 22 Class I and 21 Class II subjects was selected; the inclusion criteria were overjet, ANB, and Harvold unit difference. Analyses of head circumference, crown-rump length, and weight revealed no significant (P >.15) differences between the Class I and Class II infant subjects at the initial age (1 month). One angular and 6 linear measurements were first compared with a multivariate analysis of variance, which revealed significant effects for age (P <.0001) and the age by skeletal pattern interaction (P =.0266) but not for skeletal pattern (P =.3705). Analyses of variance showed significant (P <.0001) age effects for each of the cephalometric variables but no significant skeletal pattern effects (P >.10). The anterior cranial base measurement of nasion to sphenoethmoidal suture was the only variable found to have a significant age by skeletal pattern interaction (P <.006), which revealed a difference in the timing of its growth spurt that occurred between 1 month and 2 years in the Class I subjects and between 2 years and 14 years in the Class II subjects. There were no significant differences between the skeletal classes at any of the 3 ages evaluated. Conclusions from this study indicate that cranial base growth patterns are similar for Class I and Class II subjects and that the premise of a more obtuse "saddle angle" or cranial base angle in Class II skeletal patterns was not supported.

Relation of the ethmoidal cells to the floor of the anterior cranial fossa

The shape of the anterior part of the anterior cranial fossa undergoes important changes in the postnatal life depending on the degree of pneumatisation of the ethmoid labyrinth and/or the frontal sinus. There exist three possibilities in these relations: 1) From the newborn period up to 9 years of age, in the majority of the cases the cribrous plate is situated at the level of the roof of the ethmoid labyrinth with the width of the ethmoid incisure corresponding to the width of the cribrous plate. 2) In the period from 9-35 years of age, in the majority of cases, the ethmoidal cells are partly or completely incorporated into the floor of the anterior cranial fossa with the width of the ethmoid incisure corresponding to the number of cells forming the floor of the anterior cranial fossa. 3) In the period from 35-80 years of age, the cribrous lamina is in the majority of cases lowered due to the intensive development of the frontal sinus. The medial wall of the ethmoid labyrinth consists of a thin bony strip, the width of which depends upon the degree of lowering of the cribrous plate. Adequate CT imaging may clarify the situation.

Radiographic anatomy of the cribriform plate (Lamina cribrosa)

The radiographic appearance of the cribriform plate was investigated in 16 canine cadaver heads. The cribriform plate appeared as a "V"-shaped multilinear bone-opaque stripe in the caudal nasal region in projections perpendicular to the hard palate in 6 dogs with a skull index between 50.00 and 54.00. In 9 dogs with a skull index between 55.40 and 74.40, the cribriform plate had a more "C"-shaped and sharp appearance. In vertically oblique projections with an obliquity greater than 20 degrees, the cribriform plate lost its sharp outline and finally (40 degrees) disappeared. In lateral projections the cribriform plate appeared as a "C"-shaped interrupted bone-opaque stripe in all 16 dogs. In more brachycephalic dogs frontal bone structures superimposed on the cribriform plate on ventrodorsal and dorsoventral views and accentuated the radiographic appearance of the plate. Vertically oblique views separated both structures to produce two lines.

Radiographic detection of defects of the nasal boundaries

The sensitivity of conventional radiography for lesions of the cribriform plate, naso-orbital wall, lateral nasal wall and hard palate was investigated in 13 canine cadaver heads by creating measured defects in these structures. The location of the perforations were marked with a thin copper wire and the radiographic appearance of the defects was evaluated retrospectively by a single reviewer. Despite demarcation cribriform plate destruction of 2 mm could not be detected. Defects of 3 mm were detected in only 2 heads, 4 mm defects in 1 further head, an oblong 4 x 10 mm defect in 7 heads and in the remaining 3 heads only a 10 x 10 mm defect became visible as such. The naso-orbital wall had to be destroyed in its whole vertical length for detection of a defect in ventrodorsal or dorsoventral views. Therefore conventional radiography is of low diagnostic value for these lesions. Defects of 2 mm in the lateral nasal wall and the hard palate could be detected confidently in all heads indicating high sensitivity of conventional radiography. Soft tissue opacification did not alter the detectability of any nasal border structure lesion.

Fontanelle and uncinate process in the lateral wall of the human nasal cavity

OBJECTIVES

Although a complete anatomic knowledge of the fontanelle is a prerequisite to perform a surgical antrostomy opening, little is known about the boundary, shape, and size of the fontanelle. The purpose of this paper is to determine the best site for maintaining the patency of a surgical antrostomy opening by defining the anatomic boundaries, shape, and size of the fontanelle as well as its histological structure.

MATERIALS AND METHODS

One hundred sagittally divided heads were utilized. Mucosa overlying the lateral nasal wall was carefully removed with an operating microscope under 6x magnification. In some cases, a double mucous membrane, including the posteroinferior portion of the uncinate process, was cut as a whole and embedded in paraffin. The sections were stained with H&E.

RESULTS

The boundary of the fontanelle and the location of the natural ostium were described in detail. Eight patterns of the posteroinferior portion of the uncinate process were observed. There were three major fontanelle shapes when observed from the medial aspect to the lateral: triangular, pencil-like, and oval. The triangular type was the most common. The anterior portion of the fontanelle was shorter than the posterior when observed medially and was wider than the posterior portion when observed inferiorly.

CONCLUSIONS

The anterior portion of the fontanelle is more prone to stenosis than the posterior portion. An antrostomy in the posterior fontanelle may be more ideal for a middle meatal antrostomy of the maxillary sinus.

The reliability and variability of SN and PFH reference planes in cephalometric diagnosis and therapeutic planning of dentomaxillofacial malformations

Various interpretations of clinical and cephalometric data lead to different diagnostic and surgical planning in the study of dentoskeletal malformations. Many authors have identified this discrepancy as an incorrect positioning between the skeletal structures and the Frankfurt plane (PFH)--a plane that is used routinely for the sagittal measurement of the upper and lower jaw. The aim of this study was to establish a control method to verify the correct positioning of the sella-nasion point plane (SN) and the PFH. To find a reference plane, the authors concentrated their attention on measuring the intersecting angles between these two planes and the vertical posterior maxillary (PM) plane. Fifty patients (33 women and 17 men), all of whom were aesthetically and structurally harmonious class I dentoskeletal types, were analyzed using this method. Student's t-test, the Kolmogorov-Smirnov test, and Fisher's F-test were used for statistical analysis. The results were compared with those proposed by the University of Michigan. To achieve a correct diagnosis and to obtain good functional and cosmetic results in the treatment of these kinds of malformations, it is necessary to make use of the PM vertical plane during cephalometric analysis.

Computed tomographic imaging to determine the frequency of anatomical variations in pneumatization of the ethmoid bone

The present study was performed on axial and coronal CT scans of 212 patients. Scans were analyzed by an anatomist and a radiologist for the presence of Haller's cells, agger nasi cells, Onodi's cells and pneumatized crista galli. Results demonstrated the presence of Haller's cells in 21.2%, Onodi's cells in 10.4% and pneumatized crista galli in 2.4% of patients. A pneumatized anterior clinoid process was found in 0.5% of the patients. The data obtained in our study were compared with those reported in other anatomic and radiologic studies.

Development of the cribriform plate and of the lamina mediana

The development of the cribriform plate and lamina mediana was studied in macerated isolated ethmoid bones in specimens from late fetal life to the stage of its final shape (60 specimens). From fetal life to the first year of age, the ethmoid bone consisted of two separate symmetrical halves which had joined together by the end of the first year. Each half of the future ethmoid bone incorporated the superior, middle and occasionally also the supreme nasal concha. The ossification of the cribriform plate started in the new-born where it initially displayed a vertical position but became horizontal in the course of the first year. At the end of the first year both halves of the ethmoid bone had been united by the formation of the crista galli, lamina mediana and complete ossification of the cribriform plate. The lamina mediana reached its final shape by ten years of age. Each half of the ethmoid bone displayed furrows for the fila olfactoria in the region of the superior and occasionally also of the anterior part of the middle nasal concha. The furrows run in a postero-anterior direction. In the course of our investigations we found three cases where all three nasal conchae formed a unique block thus proving the common origin of these structures from the cartilaginous nasal capsule.