Value of secondary coronal reconstructions in computed tomography of the paranasal sinuses

INTRODUCTION: Before sinus surgery, computed tomography (CT) of the paranasal sinuses and anterior skull base is a standard procedure in the diagnostic evaluation. However, coronal sections necessary for the analysis of the complex anatomy of this region are often not applicable in multiple injured or elderly patients due to the impossibility to maintain the required position for the coronal scans. Secondary coronal reconstruction of primary axially acquired scans could help to overcome this problem. This technique was, however, hampered so far by an insufficient resolution in case of conventional CT. We therefore compared the quality of primary coronally acquired conventional CT images with the resolution of multiplanar reformatted coronal images of primary axially acquired scans by means of a new CT generation, the Multidetector Computed Tomography (MDCT). MATERIAL AND METHODS: 10 patients were each examined with conventional CT or MDCT respectively. The quality of primary coronally acquired conventional scans (CT) versus secondary coronal reconstructions (MDCT) was compared by evaluating typical anatomic landmarks. RESULTS: As compared to conventional CT, the coronal reconstruction of primary axially acquired scans by means of MDCT revealed an equal resolution and additionally no essential impairment by amalgam artefacts. CONCLUSION: Our results demonstrate the excellent quality of secondary coronal reconstructions by means of MDCT in the CT evaluation of the paranasal sinuses and the anterior skull base as compared to primary coronally acquired images via conventional CT.     

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.     

The usefulness of computed tomography scans in cystic fibrosis patients with chronic sinusitis

BACKGROUND: This study was performed to evaluate the usefulness of computed tomography (CT) scans of the sinuses in children with cystic fibrosis (CF) as an outcomes measurement for medical and surgically treated chronic rhinosinusitis. METHODS: Patients with CF who had sinus scans performed at the study institution from January 1999 to September 2003 were identified. The scans and any available prior scans were scored according to the Lund-MacKay system. A retrospective chart review determined if hospitalization with i.v. antibiotic therapy or operative intervention had occurred between scans and if the scans showed improvement secondary to the intervention. RESULTS: One hundred thirty-four patients were identified who met inclusion criteria. A total of 290 scans were reviewed, with the average number of CT scans per patient of 2.24 (range, 1-10). The average Lund-MacKay score for scans closest in time to the first sinus surgery was 14.5. (range, 7-24), and for the first postoperative scans, the score was 14.7 (8-24). There was no significant difference between the preoperative and postoperative Lund-MacKay score after initial surgery (p = 0.99) or in subsequent scans despite medical or surgical interventions (p = 0.90). CONCLUSION: CT scanning of the sinuses does not appear to be useful in determining outcomes of intervention in CF patients.     

鼻内镜鼻窦手术前筛窦颅底高度的CT评估价值

目的 探讨内镜鼻窦手术前应用CT评估筛窦颅底高度的价值。 方法 选取就诊于我院的100例共200侧的鼻窦冠状CT扫描图像,测量筛前动脉水平的筛顶中点至眶水平中线的距离,根据测量数据进行分型,同时进行Keros分型,用皮尔森相关系数来确定两者之间是否存在相关性。 结果 筛前动脉管水平的筛顶中点至眶水平中线的距离作为筛窦颅底高度。根据筛窦颅底的高度进行分型,其中Ⅰ型即筛窦颅底高度>7 mm(高位颅底)占44%(88/200),Ⅱ型即筛窦颅底高度介于4~7 mm(中位颅底)占41%(82/200),Ⅲ型即筛窦颅底高度<4 mm(低位颅底)占15%(30/200)。按Keros方法进行测量并分型,Ⅰ型占37%(74/200),Ⅱ型占52%(104/200),Ⅲ型占11%(22/200);Keros分型与筛窦颅底高度之间的皮尔森相关系数为0.384(P<0.001),Keros分型与筛窦颅底高度呈弱相关性。 结论 筛窦颅底高度存在明显差异,术前进行CT影像评估,可有效识别低颅底变异,有助于避免颅底损伤,进而减少内镜手术并发症。     

Vidian canal: analysis and relationship to the internal carotid artery

OBJECTIVES: The purpose of this study is to describe the anatomy and relationships of the vidian canal to known endonasal and skull base landmarks. This will allow the endoscopic skull base surgeon to safely approach the anterior genu of the petrous carotid artery during expanded endonasal approaches to the skull base. STUDY DESIGN: The study is a prospective cohort study. METHODS: Axial, coronal, and sagittal computed tomography scans of the paranasal sinuses and skull base of 44 patients were examined. Individuals with known skull base pathology were excluded. Measurements included the length of the vidian canal, the relationship of the vidian canal to the anterior genu of the petrous carotid artery, and the type of pneumatization of the sphenoid sinus as it pertains to foramen rotundum and the vidian canal. In addition, we will focus on the relationship of the vidian canal to the sphenopalatine foramen and base of the medial pterygoid plate. RESULTS: The degree of pneumatization of the sphenoid sinus is highly variable. The mean length of the vidian canal is 18 mm (10-23 mm). The vidian canal is found entirely within bone in 27% to 30% of scans reviewed. The anterior genu of the petrous internal carotid artery is found superior-medial to the vidian canal in 44 of 44 of the CT scans reviewed. The vidian canal runs medial to lateral in 93% to 98% of patients studied. CONCLUSIONS: As a result of this study the endoscopic skull base surgeon has a number of anatomical landmarks and measurements that may be helpful in safely localizing the anterior genu of the petrous internal carotid artery during expanded endonasal approaches to the skull base.     

Clinical applications of three-dimensional CT images for diseases of the anterior and middle cranial base

CT scanning has made significant contributions to the diagnostic, therapeutic and prognostic aspects for the managements of the lesions in the paranasal sinuses and the orbit. The current availability of 3-D imaging reformatted from CT scans has added a new dimension to anatomic investigations and pre- and postoperative evaluations of the skull base structures. Twenty-five craniomaxillofacial 3-D CT examinations were performed during the year of the 1989 for the purpose of the diagnosis of the pathology, surgical planning and postoperative evaluation in reconstructive surgery of the skull base. Results: 1. The use of 3-D CT improves the display of the location and volume of the pathology and affords the accurate therapeutic and surgical planning. 2. Preoperative 3-D CT imagings are useful for the display of the bony erosion of the skull base. Stereotaxic 3-D CT imagings are particularly appreciated in the diagnostic aspects of the management of the pathology. 3. In the reconstructive surgery of the skull base, an accurate prefabricated model of the bony defect can be made to aid the surgery. 4. A major limitation of 3-D CT is its inability to reconstruct the pathology of soft tissues with the same fidelity afforded bony structures.     

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.     

The predictive value of so-called secondary reconstruction in fractures of the frontal skull base

While MRI offers excellent possibilities to visualize different planes of a structure of interest, CT is limited to the axial and coronal plane. In most cases, CT examination can be carried out in the traumatised patient in the axial plane only. Therefore, in the present study the authors tried to investigate the value of multiplanar reconstruction of CT scans in anterior skull base traumatology, 18 patients (6 female, 12 male) aged between 18 and 57 years with bony lesions of the anterior skull base caused by different traumatic events were examined under a CT scanner of the fourth generation. A high-resolution mode was used in 14 out of 18 patients. The axial scans were reformated in coronal and sagittal planes. The clinical value of the reconstructed images, however, was poor. They would not supply additional information compared to the original scans; the quality of the reconstructed scans was even worse. Artifacts could not be distinguished from bony lesions. The results indicate that multiplanar reconstructions of CT scans are not sufficient in the evaluation of bony lesions of the anterior skull base.     

Study of surgeons' agreement on the presence of bony anomalies on coronal CT of paranasal sinuses

We conducted a study to determine the level of agreement among five surgeons who assessed the surgical risk to key neighboring structures prior to endoscopic sinus surgery as depicted on coronal computed tomography (CT). The five observers studied preoperative CT scans that had been performed on 29 patients. Two scoring systems were used to rate each scan; the Lund-Mackay system and our own risk-assessment system. Kappa analysis was used to measure interobserver agreement. We found that the overall level of agreement among the five surgeons according to the Lund-Mackay criteria was moderate, while agreement according to our risk-assessment system was only slight. We conclude that surgeons' agreement on the bony detail of risk structures is not as strong as our agreement on other factors, such as staging disease.     

Intraoperative computed tomography in otorhinolaryngology

CONCLUSIONS: Intraoperative CT surgery provides the surgeon with additional information about the altered surgical site in difficult anatomical situations. The skull base and lamina papyracea may be revealed by means of intraoperative CT, which may be beneficial in endonasal sinus surgery involving difficult surgical sites, although individual ethmoid cells cannot be assessed owing to blood artefacts. This provides the surgeon with valuable information that may facilitate the procedure considerably. In soft-tissue surgery it is advisable to apply a contrast agent in order to achieve good soft-tissue contrast, thus allowing the tumour to be adequately distinguished from benign tissue. The intraoperative application of CT is a fairly time-consuming procedure, partly owing to the preparation time (set-up of the appliance; 10-min warming-up phase) and partly due to the length of time required to calculate each image (15 s). OBJECTIVE: CT is a well-established imaging method for the assessment of osseous and soft-tissue structures in the head and neck region. Saving information and transferring it to the intraoperative site may, however, be problematic. Computer-assisted navigation systems are now able to assist difficult surgical procedures in the field of otolaryngology. To investigate the indications for intraoperative CT, we used it in various surgical procedures in the head and neck region. MATERIAL AND METHODS: Intraoperative CT was applied using the Tomoscan M in 46 cases in order to demonstrate the surgical benefit of the following procedures: endonasal surgical procedures on the paranasal sinuses (maxillary and ethmoidal sinusitis, anterior fracture of the sphenoidal sinus); tumour removal by means of laser surgery (carcinomas of the hypopharynx and larynx); and cochlear implantation (to verify the electrode position). After positioning the patient on the CT table, the workstation was set up in the operating theatre. If necessary, the gantry could be moved over the patient's head without repositioning the patient. RESULTS: Intraoperative CT was used to assist in the exposure of the skull base and lamina papyracea in endonasal surgery of the paranasal sinuses. Individual ethmoidal sinuses could not be evaluated owing to blood artefacts. Intraoperative imaging proved particularly helpful in revision surgery for chronic sinusitis in cases with missing anatomical landmarks owing to previous surgeries, where there is an increased risk of inflicting damage to the skull base or orbita. The resection margins can be determined in craniofacial resections. In soft-tissue procedures, such as tumour removal by means of laser surgery, it proved possible to visualize the resection borders of malignant tumours. Assessment of the electrode position in cochlear implantation is particularly useful in revision cases and in cases of cochlear obliteration.     

翼管在内镜经鼻颅底手术中的标志作用

目的通过影像学和解剖学方法进行研究以明确翼管在鼻内镜经鼻颅底手术中的价值并为临床提供参考。方法选23具尸头行冠状位及轴位高分辨CT扫描,观察翼管及其与周围结构的关系,并测量相关距离。选其中3具经过动脉灌注的尸头,分别采用经上颌窦、经鼻至翼腭窝-海绵窦入路进行鼻内镜下的解剖学研究。结果高分辨CT能够清晰显示翼管形态、走行及其与周围结构的关系。所有翼管均位于颈内动脉管水平段或其以下层面。鼻内镜解剖与相应的影像学提示相同,翼管内容恒定地指向颈内动脉前膝;翼管和圆孔之间的距离标定了一个手术门户。结论翼管是内镜经鼻颅底手术的一个重要解剖标志,作为骨性管道,高分辨CT可以清晰显示翼管。     

Lack of significant correlation between rhinosinusitis symptoms and specific regions of sinus computer tomography scans

BACKGROUND: The sinonasal computer tomography (CT) scan is frequently used to help confirm the diagnosis of rhinosinusitis. However, little data exist correlating patient symptoms with CT findings. METHODS: Immediately preceding CT of the sinuses, 94 subjects without evidence of trauma, nasal tumors, or previous sinus surgery completed the Rhinosinusitis Outcome Measure 31 symptom questionnaire and were asked to locate areas of facial pain or pressure. CT scans were graded according to the Lund-MacKay system, and agger nasi and ethmoid bulla cells were measured. Data from CT scans and symptom/pain questionnaire responses were analyzed for significant correlations. RESULTS: No correlation was identified when comparing total Lund-MacKay scores, opacification of individual sinuses, and size of the agger nasi and ethmoid bulla cells with the Rhinosinusitis Outcome Measure 31 subset scores and areas of facial pain or pressure. CONCLUSION: The sinus CT scan is a necessary tool for preoperative planning; however, it should not be used to predict symptoms or to localize areas responsible for facial pain or pressure.     

The anterior ethmoidal artery: radio-anatomical comparison and its application in endonasal surgery

CONCLUSION: High-resolution CT scans are able to determine with accuracy the location of the anterior ethmoidal artery in relation to the roof of the ethmoid. This investigation should greatly help functional endoscopic sinus surgery to avoid accidental injury of the artery and to coagulate the vessel in cases of severe epistaxis. OBJECTIVES: This was a radio-anatomical study of the anterior ethmoid artery in order to assess the course of the artery prior to endoscopic cauterization. MATERIALS AND METHODS: Eighteen ethmoid sinuses (nine heads) were dissected and high-resolution CT scans were performed in axial, coronal and sagittal planes. RESULTS: All anterior ethmoidal arteries were identifiable. The arteries were included in the roof of the ethmoid in eight cases. In three cases the arteries were prominent under the roof. In seven cases the dissection found the arteries distant from the roof. This anatomical feature was associated with pneumatization of the floor of the orbit. The correlation between CT scan and dissection was very satisfactory.     

筛泡前气房CT三维重组的影像特征及手术技巧

目的筛泡前气房可严重阻碍额窦引流,但却常被忽视,本文通过CT三维重组技术分析筛泡前气房的影像特点及其同额窦引流通道的关系,探讨手术去除筛泡前气房、开放额窦的技巧。方法对鼻及鼻窦炎患者术前轴位薄层螺旋CT扫描,冠状位、矢状位重组,明确筛泡前气房的存在,在鼻内镜下确认,分析它同额隐窝引流通道的关系。结果筛泡前气房在矢状位和轴位CT均表现为额窦区域后上方的气房,从额隐窝沿着颅底进人额窦：手术中沿着筛泡前气房的前壁可顺利找到额窦口。结论 CT三维重组对明确筛泡前气房和额窦引流通道的关系有重要意义,筛泡前气房是筛泡过度气化形成从颅底越过额窦口延伸至额窦内影响额窦引流,手术中去除筛泡前气房,可明显扩大额窦口,改善额窦引流。     

Height and shape of the skull base as risk factors for skull base penetration during endoscopic sinus surgery

OBJECTIVES: Computed tomography (CT) and magnetic resonance imaging have identified several risk factors for life-threatening complications of skull base penetration during endoscopic sinus surgery (ESS). We compared these risk factors between groups of patients with and without penetration. METHODS: We performed a retrospective review of direct coronal paranasal sinus CT scans. Using preoperative CT scans of 100 patients without and 7 patients with penetration, we classified height into 4 groups and contour into 2 groups. The frequencies of shape and height differences of the right and left halves of the skull base were calculated in each group. RESULTS: In 6 of the 7 patients who had skull base penetration, ESS was performed by a resident or junior staff member who had less than 3 years of experience with this technique. Shape asymmetry was seen in 4 of the 7 patients (57%) with penetration, which was a significantly higher rate than in patients without penetration (18 of 100; p = .032). The frequencies of a low skull base and a height difference were 15% and 28%, respectively. CONCLUSIONS: The most important risk factor for skull base penetration was the surgeon's inexperience. An asymmetry of shape of the right and left halves of the skull base was significantly related to inadvertent skull base penetration during ESS.     

影像导航引导鼻内镜下前颅底骨化纤维瘤切除术

目的 探讨影像导航系统在经鼻内镜切除前颅底骨化纤维瘤手术中的作用。方法 选择影像导航引导下经鼻内镜手术切除累积眶纸板、颅底骨质的筛窦骨化纤维瘤12例男性患者,初次手术9例,复发病例3例。术前行鼻窦CT连续扫描,骨算法,层厚1mm。结果 CT显示所有病例筛骨水平板、眶纸板受累。4例前界至额隐窝前缘（鼻骨后）;6例累及眶尖与蝶窦外侧壁交界处：1例广泛累及上颔骨、蝶骨大翼、蝶鞍和斜坡。11例彻底切除病灶,1例（病变广泛者）切除大部分肿瘤。平均手术时间3．2小时,影像导航配准过程平均25分钟。1例术中并发脑脊液漏,术中鼻内镜下修补成功;3例术中损伤眶纸板,无手术及术后并发症。术后随访5个月～4年,姑息手术病例肿瘤生长缓慢,其余病例无复发,症状明显改善。结论 借助影像导航引导,经鼻内镜手术切除累及眶纸板、前颅底骨质的骨化纤维瘤,具有一定优势,但病灶不应广泛侵及额隐窝、蝶骨及斜坡。     

Radiological studies in trigeminal nerve pathology

The authors have used CT scans and MRI to study pathology in anatomical and radiological correlations of brain slices. The CT scan was particularly useful for studying structures at the skull base, although at the level of the posterior fossa such scans could visualize only those tumors that were larger than 8 mm. even after injection. The CT scan was found to be the most useful examination before surgery for facial neuralgia. In contrast MRI gave a precise cisternal course of the trigeminal nerve and its relations with vascular structures.     

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.     

The analysis of anterior skull base from two different perspectives: coronal and reconstructed sagittal computed tomography

The aim of the study was to determine the heights of the anterior skull base and the distances between the anterior nasal spine and the skull base at three levels by means of coronal and reformatted sagittal images of computed tomography. The present study was performed on coronal and reformatted sagittal CT scans of 30 patients with sinonasal complaints. On the coronal view, the heights of the cribriform plate, the roof of ethmoid, and lateral lamella and the medial take-off angle between the ethmoid roof and cribriform plate were measured at different levels. On the reformatted sagittal images the distances from the nasal spine to the anterior cranial base at three different levels were measured. Then, the side-to-side variability of these measurements was statistically compared. The variations with normal distribution and abnormal distribution were analysed by paired t test and Wilcoxon paired-signed rank test, respectively. A statistically significant difference was detected only between the right and left sides in the height of the lateral lamella at the crista galli level (p < 0.05). The lateral lamella at the crista galli level on the left side was higher than on the right side. No statistically significant differences between the left and the right sides were noted in the heights and the distances of other data (p > 0.05). The normal anatomy of the anterior skull base has been described in detail on coronal and reconstructed sagittal computed tomography. These measurements may be helpful in the presurgical evaluation of patients undergoing endoscopic sinus surgery to optimize surgical safety.     

Preoperative CT scanning for endoscopic sinus surgery: a rational approach

Recent research on inflammatory sinus disease has implicated a central role for the ethmoid labyrinth, which may influence changes in the maxillary and frontal sinuses. CT can provide excellent definition of the paranasal sinuses and particularly the ethmoids, which is a prerequisite for endoscopic surgery. We describe a prospective series of 110 coronal CT scans performed on patients with a clinical diagnosis of sinusitis who had undergone diagnostic nasal endoscopies and medical treatment prior to surgery. 86% of the scans showed abnormal mucosal thickening. The ethmoids were affected in 73% and the maxillary sinus in 64%. Pneumatization of the middle turbinate was a common variant and when present was associated with anterior ethmoid disease in 60% of patients. Anterior ethmoid inflammatory changes were demonstrable in 95% of patients with maxillary sinus disease. Direct coronal CT can readily demonstrate disease in the infundibulum, frontal recess and posterior ethmoids in the same orientation confronting the endoscopist, and helps in the planning of ethmoidal surgery. Following surgery the sinuses can be directly inspected in outpatients which reduces the need for any further plain radiographs. It is important that the diagnosis of sinusitis is not based on CT findings alone as isolated areas of mucosal thickening are common in the normal population.