The relationship between pneumatized middle turbinate and the anterior ethmoid roof dimensions: a radiologic study

The development of pneumatized middle turbinate may affect anterior ethmoid roof formation. The aim of this study was to investigate the relationship between the pneumatized middle turbinate and the dimensions of the anterior skull base structures using computed tomography scans. The coronal reconstructed images of the computed tomography scans were evaluated retrospectively. The lateral and medial ethmoid roof points, the width of the cribriform plate (CP), and the anterior ethmoid roof were identified at the first coronal cut, which was determined by the infraorbital nerve. The pneumatized middle turbinates were measured on the axial, vertical, and sagittal planes. The images of 101 patients were evaluated. The mean axial diameters of the pneumatized middle turbinate on the right and left sides were between 6.93 and 4.95 mm, respectively. The correlation between the axial diameters of the pneumatized middle turbinate and the width of the anterior ethmoid roof (termed AER width) was significant for both sides and gender (p < 0.05). There was a higher correlation on the right side where the pneumatized middle turbinate was observed more frequently (r = 0.357). The relationship between CP width and the diameters of the pneumatized middle turbinate was not significant (p > 0.05) for both sides. Iatrogenic lesions of the skull base occur predominantly in the lateral lamella of the CP. The risk of this complication may decrease with increasing of the AER width. Pneumatized middle turbinate may cause an increase in the width of the anterior ethmoid roof and provide more reliable endoscopic intervention of the anterior skull base and frontal sinus.     

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.     

Anterior skull base trauma during endoscopic sinus surgery for nasal polyposis preferred sites for iatrogenic injuries

OBJECTIVE: To determine typical locations for traumatic lesions of the anterior skull base during endoscopic sinus surgery. STUDY DESIGN: In this retrospective study 12 patients were included who had undergone endoscopic sinus surgery for nasal polyposis and were referred to the author for revision surgery after iatrogenic trauma of the anterior skull base during the procedure. Each patient had been operated by a different surgeon, all of the physicians being in an advanced stage of their surgical career and being board certified otolaryngologists. RESULTS: During endoscopically controlled revision surgery, all lesions could be detected, 10 of them being located in the ethmoid roof, while one injury had occurred in the lateral lamella of the cribriform plate and another one in the olfactory groove between the medial turbinate and the nasal septum. CONCLUSION: In contrast to reports in the literature, the preferred site for anterior skull base injuries during endoscopic sinus surgery in our group was not the lateral lamella of the cribriform plate, but the anterior part of the ethmoid roof, just behind the frontal recess. Apparently the course of the ethmoid roof might be misinterpreted during sinus surgery even by surgeons who are familiar with the operative technique.     

Bilateral choanal atresia associated with malformation of the anterior skull base: embryogenesis and clinical implications.

A number of craniofacial and systemic malformations have been described in association with choanal atresia. We report a case of bilateral choanal atresia associated with congenital absence of the cribriform plate, crista galli, and perpendicular plate of the ethmoid bone. The anterior skull base defect was detected by using high-resolution computed tomography with three-dimensional reconstructions. The findings support the mesodermal flow theory of choanal atresia, in which there is excess migration of neural crest cells into the developing nasal septum and posterior choanae. This occurs at the expense of cells that would otherwise form the rest of the ethmoid complex. Clinical implications include the need for adequate preoperative imaging of the anterior skull base and consideration of potential intracranial complications during surgical repair.     

中国人的嗅沟及其邻近结构的影像解剖研究

目的 对于复杂颅前窝的理解对于鼻内镜手术至关重要,在CT三维重建的图像中对嗅沟及邻近结构数据进行测量,应用动态的解剖学的观测有利于医师做出术前精细的手术计划以避免对前颅底的损伤.方法 100例成年人的鼻窦图像在EBW2.0工作站上应用多平面重建技术进行重建,在嗅沟最前端的冠状面对两侧筛板深度及其邻近结构的数据进行测量,邻近结构包括嗅沟的侧板的高度,筛板与同侧眶纸样板的距离,中鼻甲的高度,眼眶的高度,筛板与鼻底的高度.结果 嗅沟被划分为有别于KEROS分型的3型:平台型(60%),斜坡型(17%)和混合型(23%).其中平台型嗅沟的侧板的高度为右侧(5.03±0.17)mm,左侧(5.39±0.19)mm;混合型其高度为右侧(2.79±0.49)mm,左侧(4.72±0.49)mm,两型对比左右两侧数据有显著性差异;筛板与同侧眶纸样板的水平距离和筛板与鼻底的垂直距离在平台型和混合型嗅沟之间有显著性差异.该数据在男女性别方面也存在差异.结论 不同类型的嗅沟存在不同的特点,在进行鼻内镜手术时需谨慎.     

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.     

The surgeon's view of the anterior ethmoid artery

Objectives: To define the relationship of the anterior ethmoid artery to the frontal recess and secondly whether the degree of pneumatisation of the suprabullar recess/supraorbital cell correlates with the distance between the anterior ethmoid artery and the skull base thus making it more vulnerable to damage during surgery. Method: Thirty‐four cadaver head sides were perfused with pink latex. All specimens had high‐resolution computed tomography (CT) scans using bone windows in the axial, coronal and sagittal planes. The specimen's nasal septum was removed and the ethmoid sinuses dissected to locate the anterior ethmoid artery. Calipers were used to measure distance between the artery and the frontal recess and from the skull base. Results: The anterior ethmoid artery was found in all the specimens and scans. The distance between the anterior ethmoid artery and the posterior wall of the frontal recess was 11 mm (range 6–15 mm). In all specimens, the artery was seen between the second and third lamella. The commonest location of the artery was in the suprabullar recess (85.3%). Supraorbital cells were seen in 16 specimens. The ethmoid sinuses were well pneumatised with a large supraorbital cell in 10 of these specimens and in these the artery was lying 3.7 mm (range 1–8 mm) away from the skull base. Six specimens had poor pneumatisation and a small supraorbital cell and in these the artery was found close to or with in the skull base. In specimens without a supraorbital cell, the artery lay at the skull base in all but one. Conclusions: The position of the anterior ethmoidal artery is very variable. The artery is found between the second and third lamella. When the ethmoid sinuses are more pneumatised and in particular when there is a supraorbital cell, the artery lies below the skull base. A good strategy is to identify the degree of pneumatisation of the ethmoid sinuses from CT scans preoperatively to see if the artery is at an increased risk of being damaged.     

Lateral lamella of the cribriform plate: software-enabled computed tomographic analysis and its clinical relevance in skull base surgery

OBJECTIVE: To describe a quantitative analysis of the lateral lamella of the cribriform plate (LLCP) height in computed tomographic (CT) images. The LLCP is the thinnest anatomic structure in the skull base. DESIGN: Software-enabled CT scan measurements. SETTING: Academic center. RESULTS: The CT scans from 50 patients were analyzed. The median height of the LLCP in 100 sides was 2.4 mm. The LLCP height was 0 to 3.9 mm in 83 sides, 4.0 to 7.0 mm in 15 sides, and greater than 7.0 mm in 2 sides. When analyzing differences among sides, the LLCP height was greater on the right side in 28 patients and greater on the left side in 22. The differences between sides was 0 to 1.9 mm in 39 patients, 2.0 to 3.9 mm in 9 patients, and greater than 4.0 mm in 2 patients. CONCLUSIONS: Computer-aided CT scan analysis allows for a quantitative analysis of the paranasal sinus skull base anatomy. Knowledge of these dimensions is invaluable during surgical planning and navigation. Asymmetry of the relative ethmoid roof position is common. Thus, the rhinologic surgeon must exercise caution to prevent unintentional skull base injury and cerebrospinal fluid leak.     

筛泡基板前上端在鼻内镜额窦手术中的定位作用

目的寻找适合鼻内镜手术下开放额窦的解剖学标志,以降低手术并发症的发生率。方法对30例(60侧)慢性鼻窦炎病人行鼻窦CT扫描,根据CT扫描中筛泡基板前上端向上附着的部位与纸样板/筛顶的关系,术中以筛泡基板前上端为标志,寻找额窦开口,进行鼻内镜额窦手术。并与同期40例(75侧)依据前筛顶额突为标志进行鼻内镜额窦开放术的手术并发症的发生率进行比较。结果30例(60侧)病人在以筛泡基板前上端为解剖标志进行鼻内镜额窦开放术中,手术并发症的发生率为3.3%(1/30),与同期40例(75侧)病人依照颅底额突作解剖标志进行鼻内镜额窦开放术的手术并发症的发生率20%(8/40)进行比较有统计学意义(P<0.05)。结论在鼻内镜额窦手术中以筛泡基板前上端为解剖标志,能有效地帮助寻找额窦开口,降低手术并发症的发生率。     

Anterior skull base: High risk areas in endoscopic sinus surgery in chronic rhinosinusitis: A computed tomographic analysis

Computed Tomography (CT) scan of nose and paranasal sinuses play a key role in preoperative evaluation of patients undergoing endoscopic sinus surgeries (ESS) for chronic rhinosinusitis. The asymmetry of ethmoid fovea olfactory fossa, anatomical variations of lateral lamella and course of anterior ethmoid artery are critical in ESS as it may predispose to dangerous consequences like hemorrhage. CSF leak and intracranial complications. A prospective study was done on 75 patients of clinically and diagnostically proven chronic rhinosimusits. The coronal CT scan was evaluated with special attention to anatomical variations of anterior skull base including ethmoid fovea, olfactory fossa, lateral lamella and course of anterior ethmoid artery. The endoscopic surgeon's awareness of these variations and its role in preventing complications are highlighted.     

Endoscopic reconstruction of the anterior skull base in cerebrospinal rhinorrhea

Cerebrospinal rhinorrhea is a discharge of cerebrospinal fluid caused by the break continuity in dura mater and by bone defect in the base of anterior skull base. The pathological connections appear mainly in the regions of the skull base with the weaker bone structure (the roof of the frontal, ethmoid, sphenoid sinus and cribriform plate). The aim of the study was presenting the possibility of the endoscopic-surgical closing the fistula within the ethmoid roof. The E.N.T Department in Poznań treated 5 patients with cerebrospinal rhinorrhea. In four cases, cerebrospinal rhinorrhea was caused by operative trauma. In one case the rhinorrhea could not be established. All patients with traumatic rhinorrhea underwent operation treatment based on covering of the loss in dura mater with a piece of mucous membrane together with perichondrium of nasal septum or lyophilised dura. The material used for the plastic operation was sealed by tissue adhesive. In 2 cases rhinorrhea recurred. Using the endoscopic technique, after the identification the leak of the cerebrospinal fluid within ethmoid roof, the fistula has been reconstructed with use of the adipose tissue and temporal muscle fascia. Both cases led to complete recovery. Easy access, precision and accuracy of performance the surgery, the approach without external incision of the patient, makes the endoscopic technique very valuable method in treating rhinorrhea caused by the loss in ethmoid roof and cribriform plate.     

Computed tomography anatomy of the anterior ethmoid canal

The roof of the anterior ethmoid swings up anteriorly from its more or less horizontal course at the point where the anterior ethmoid canal (AEC) is situated. The AEC is an important structure in endoscopic sinus surgery since its injury results in bleeding into the nasal cavity and may result in intraorbital bleeding. We therefore investigated the location of this canal and the anatomic characteristics of the area surrounding the canal using coronal computed tomography (CT) of the paranasal sinuses. One hundred sides of 50 paranasal coronal CT images in patients with sinusitis were analyzed to assess the location of the AEC, the shape of the superolateral wall of the ethmoid sinus anterior and posterior to the AEC, and pneumatization of the roof of the anterior ethmoid sinus. The AEC is situated in the second quarter of the roof of the ethmoid sinus. The superolateral wall anterior to the AEC demonstrated an acute angle in 99% of sides, while the superolateral wall posterior to the AEC showed an obtuse angle in 87% of sides. The ethmoid cell anterior to the AEC pneumatized posteriorly over the AEC in 26% of sides. We conclude that coronal CT confirmation of the anatomic characteristics of the AEC, and the area surrounding the canal, is invaluable for preoperative planning for endoscopic sinus surgery.     

Lateral rhinotomy.

The lateral rhinotomy is a technique which affords excellent exposure of the nasal cavity and lateral nasal wall and creates minimal cosmetic or functional disability. The approach will allow excision of the lateral nasal wall from the anterior tip of the turbinates to the eustachian tube and from the cribriform plate and roof of the ethmoid to the floor of the nose     

筛窦顶壁影像学分析

目的:探讨筛窦顶壁高度及形态影像解剖学特征。方法:回顾性分析160例冠状位鼻窦CT,观察左 右侧筛窦顶壁形态及高度对称性、筛窦顶壁与筛板连接方式,测量左右侧筛窦顶壁高度差及筛窦顶壁与筛板间高 度差。结果:左右侧筛窦顶高度(差>1mm)不对称者25例(15.63%),其中右侧筛窦顶较左侧低13例 (52.00%),左右侧筛窦顶高度差平均为2.35mm。左右侧筛窦顶形态62例(38.75%)不对称,一侧鸟翼状另一 侧扁平状。筛窦顶与筛板水平式连接116侧(36.25%),高台式连接204侧(63.75%)。高台型筛窦顶与筛板高 度差平均为2.80mm。结论:筛顶在高度及形态上存在左右侧不对称性,且以形态的不对称性为常见。筛窦顶壁 与筛板的连接方式以高台式多见。鼻内镜手术前及手术中仔细阅读患者鼻窦CT片具有重要意义。     

The extended maxillotomy and subtotal maxillectomy for excision of skull base tumors

An approach to tumors of the middle compartment of the skull base is described with three case reports. It is accomplished by extending the subtotal maxillectomy or maxillotomy to include removal of a part of the malar bone, coronoid process of the mandible, nasal turbinates, ethmoid and sphenoid sinuses, posterior nasal septum, and pterygoid plates. Extension of the incision through the anterior tonsillar pillar and lateral pharyngeal wall into the retropharyngeal space will assist to expose the craniocervical region from the sphenoid roof to the fifth cervical vertebra and the skull base between each eustachian tube and carotid canal. The function of the trigeminal, facial, and hypoglossal nerves, hearing, and nasal airway are preserved without mastoidectomy. A temporalis muscle flap closes the defect. Dysphagia and aspiration are not handicaps.     

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.     

Endoscopic anterior ethmoidal artery ligation: a cadaver study

OBJECTIVE: The objective of this study was to investigate the radiologic and endoscopic anatomy of the anterior ethmoidal canal (AEC) and feasibility of endoscopic ligation of the anterior ethmoidal artery (AEA). STUDY DESIGN: The authors conducted a prospective analysis of computed tomography (CT) of the paranasal sinuses and endoscopic cadaver dissection. METHODS: Twenty-two cadaver heads had CT scans of the paranasal sinuses. The height of the lateral lamella of the cribriform plate was calculated and staged according to the Keros staging system. The presence of a bony mesentery, distance from AEC to the skull base, and dehiscence of the AEC were documented. Forty-four dissections were performed, the AECs identified, and AEA ligation attempted. RESULTS: The mean height of the lateral lamella was 5.4 mm on the right and 4.7 mm on the left. In all cadaver heads with asymmetry, the right lateral lamella was longer (P<.005). A Keros type 1 pattern was seen in 23%, type 2 in 50%, and type 3 in 27%. Thirty-six percent of AECs were in a bony mesentery. AEC distance from the skull base was greater on the right (P<.009). A longer lateral lamella was correlated with the artery being in a mesentery. Sixteen percent of the AECs were dehiscent. Sixty-six percent of AEAs were unable to be clipped. Twenty percent were clipped effectively, all in a mesentery. In 14%, the AEA was not effectively clipped. CONCLUSIONS: Endoscopic AEA ligation may be possible in some patients. The AEA should be in a mesentery for an effective clip to be placed and be associated with a dehiscence of the AEC. If the lateral lamella is classified as Keros grade 2 or 3, it is likely the AEC will be found in a mesentery.     

Radiological analysis of the ethmoid roof in the Malaysian population

Objective

To ascertain the prevalence of the lateral lamella of the cribriform plate height according to Keros classification in the Malaysian population, and to find if there is any difference between the major ethnic groups in Malaysia (Malay, Chinese, Indian).

Methods

Retrospective analysis of 150 CT scan studies of the paranasal sinuses.

Results

The mean height of the lateral lamella of the cribriform plate (LLCP) in 300 sides was 2.64 mm. Keros type I was seen in 240 sides (80%), while, Keros type II was seen in 60 sides (20%). There was no significant difference in the distribution of Keros classification among the major ethnic groups of Malaysia (Malay, Chinese, Indian). Keros type I was seen in 103 sides in males and 137 sides in females. Significant difference was observed in type II between the male and female (47 sides in males and 13 sides in female; p-value <0.001). When comparing the difference in the height of the LLCP in the same individual, asymmetry was observed in 139 patients. The LLCP height was higher on the left side in 71 patients and higher on the right in 68.

Conclusion

The understanding of the anatomy of the ethmoid roof with its possible variation is crucial to give the surgeon the optimal information about the possible risk that one can face during the surgery.     

PHACE syndrome: report of a case with a glioma of the anterior skull base and ocular malformations

PHACE syndrome consists of the constellation of manifestations including Posterior fossa anomalies of the brain (most commonly Dandy-Walker malformations), Hemangiomas of the face and scalp, Arterial abnormalities, Cardiac defects, and Eye anomalies. We present the case of a patient who presented with respiratory distress at birth secondary to a large nasal glioma. She was subsequently found to have a ventricular septal defect (VSD), a facial hemangioma, and a malformation of the eye and optic nerve head. The nasal glioma, which extended to the cribriform plate, has not been described in this syndrome. The tumor was resected through a coronal incision, midline nasal bone osteotomy, and a retrograde dissection from the nasal bones to the anterior skull base. Glioma of the skull base is a novel and serious manifestation of this uncommon condition.     

Anterior craniofacial resection for ethmoid and nasal cancer with free flap reconstruction

Two surgical approaches were used for nasal and ethmoid cancers involving the anterior skull base. A craniofacial operation with the assistance of a neurosurgeon was employed when the cribriform plate was infiltrated. A frontofacial operation through the frontal sinus was preferred when the cribriform plate was radiologically intact. Thirty patients underwent radical surgery with a minimum three-year follow-up. Thirteen of 16 patients with adenocarcinoma survived. Since 1980, nine patients have had their surgical defects repaired with a revascularized tensor fascia lata muscle and skin flap. The flap is tailored to support the cranial contents, provide muscle bulk for the orbitomaxillectomy cavity, and provide skin for the face, nasal, and palatal surfaces. There were two free flap failures.