CT and MR imaging of the central skull base. Part 2. Pathologic spectrum

The radiologist must have a thorough knowledge of the normal anatomy and the pathologic spectrum of the skull base to determine the extent of abnormality and to help plan the surgical approach. The authors describe and present examples of congenital, benign, and malignant lesions that affect this region, including cephalocele, fracture, fistula, juvenile angiofibroma, meningioma, chordoma, pituitary adenoma, chondrosarcoma, nasopharyngeal carcinoma, and rhabdomyosarcoma. Metastatic, infectious, and other miscellaneous processes are also discussed. Imaging strategies with computed tomography and magnetic resonance imaging to aid in the diagnosis are suggested.     

正常颅底的CT三维重建及其临床价值

目的：应用ＣＴ三维重建（３ＤＣＴ）研究颅底的正常解剖结构，为临床诊断及治疗提供直观的立体信息。材料与方法：选择颅底二维图像正常的１０例正常人，先做薄层高分辨力ＣＴ扫描，将二维数据输入工作站做三维重建。然后将三维重建图像与颅底标本做对照。结果：三维重建可从不同角度描述并展示颅底的正常解剖。结论：三维重建能清楚显示颅底的结构，为临床提供２Ｄ图像不能显示的立体观，特别是为手术方式和入路的选择提供依据     

筛前动脉的解剖及影像学研究进展

筛前动脉是前颅底和额隐窝的重要解剖标志,手术损伤可导致严重并发症。了解其正常走行以及邻近结构,对提高手术安全性和副鼻窦内镜手术结果有非常重要的意义。本文综述了筛前动脉解剖结构及相关影像学检查,以及320层容积CT(VCT)筛前动脉血管成像的优势。     

The radiology of the pterygoid canal: normal and pathologic findings

To better define the normal anatomy and pathologic features of the pterygoid canal, 100 normal subjects and 38 patients with disease of the paranasal sinuses, nasopharynx, and base of the skull were studied with pluridirectional tomography. Particular attention was given to the normal radiographic appearance of the pterygoid canal as well as to its anatomic variants and its relationship to the paranasal sinuses. Three radiographic signs of involvement of the pterygoid canal were detected: disappearance, enlargement, and narrowing. Moreover, a brief correlation between pluridirectional tomography and CT was made. Diagnostic accuracy in evaluating the bony lesions is the same with both techniques, but CT is superior to pluridirectional tomography in evaluating involvement of the soft tissues.     

Facial sinuses. Inflammation

The radiologist must have a thorough knowledge of the normal anatomy and the pathologic spectrum of the paranasal sinuses to in order determine the location and the extent of abnormality and to plan the surgical approach. We describe the normal anatomy and variations such as concha bullosa which can alter nose physiology. Many examples of congenital and inflammatory lesions affecting this region are described, such as naso-sinus polyposis and congenital or inflammatory lesions.     

Skull base tumours Part II. Central skull base tumours and intrinsic tumours of the bony skull base

With the advances of cross-sectional imaging radiologists gained an increasing responsibility in the management of patients with skull base pathology. As this anatomic area is hidden to clinical exam, surgeons and radiation oncologists have to rely on imaging studies to plan the most adequate treatment. To fulfil these endeavour radiologists need to be knowledgeable about skull base anatomy, about the main treatment options available, their indications and contra-indications and needs to be aware of the wide gamut of pathologies seen in this anatomic region. This article will provide a radiologists' friendly approach to the central skull base and will review the most common central skull base tumours and tumours intrinsic to the bony skull base.     

Skull base tumours part I: imaging technique, anatomy and anterior skull base tumours

Advances in cross-sectional imaging, surgical technique and adjuvant treatment have largely contributed to ameliorate the prognosis, lessen the morbidity and mortality of patients with skull base tumours and to the growing medical investment in the management of these patients. Because clinical assessment of the skull base is limited, cross-sectional imaging became indispensable in the diagnosis, treatment planning and follow-up of patients with suspected skull base pathology and the radiologist is increasingly responsible for the fate of these patients. This review will focus on the advances in imaging technique; contribution to patient's management and on the imaging features of the most common tumours affecting the anterior skull base. Emphasis is given to a systematic approach to skull base pathology based upon an anatomic division taking into account the major tissue constituents in each skull base compartment. The most relevant information that should be conveyed to surgeons and radiation oncologists involved in patient's management will be discussed.     

MR, CT, and plain film imaging of the developing skull base in fetal specimens

BACKGROUND AND PURPOSE: The developing fetal skull base has previously been studied via dissection and low-resolution CT. Most of the central skull base develops from endochondral ossification through an intermediary chondrocranium. We traced the development of the normal fetal skull base by using plain radiography, MR imaging, and CT. METHODS: Twenty-nine formalin-fixed fetal specimens ranging from 9 to 24 weeks' gestational age were examined with mammographic plain radiography, CT, and MR imaging. Skull base development and ossification were assessed. RESULTS: The postsphenoid cartilages enclose the pituitary and fuse to form the basisphenoid, from which the sella turcica and the posterior body of the sphenoid bone originate. The presphenoid cartilages will form the anterior body of the sphenoid bone. Portions of the presphenoid cartilage give rise to the mesethmoid cartilage, which forms the central portion of the anterior skull base. Ossification begins in the occipital bone (12 weeks) and progresses anteriorly. The postsphenoid (14 weeks) and then the presphenoid portion (17 weeks) of the sphenoid bone ossify. Ossification is seen laterally (16 weeks) in the orbitosphenoid, which contributes to the lesser wing of the sphenoid, and the alisphenoid (15 weeks), which forms the greater wing. CONCLUSION: MR imaging can show early progressive ossification of the cartilaginous skull base and its relation to intracranial structures. The study of fetal developmental anatomy may lead to a better understanding of abnormalities of the skull base.     

Giant Rathke cleft cyst.

The preoperative diagnosis for an unusual skull base lesion was chordoma. The combination of imaging, pathologic, and surgical findings suggests the diagnosis of Rathke cyst.     

Imaging the hypoglossal nerve

The hypoglossal nerve is a pure motor nerve. It provides motor control to the intrinsic and extrinsic tongue muscles thus being essential for normal tongue movement and coordination. In order to design a useful imaging approach and a working differential diagnosis in cases of hypoglossal nerve damage one has to have a good knowledge of the normal anatomy of the nerve trunk and its main branches. A successful imaging evaluation to hypoglossal diseases always requires high resolution studies due to the small size of the structures being studied. MRI is the preferred modality to directly visualize the nerve, while CT is superior in displaying the bony anatomy of the neurovascular foramina of the skull base. Also, while CT is only able to detect nerve pathology by indirect signs, such as bony expansion of the hypoglossal canal, MRI is able to visualize directly the causative pathological process as in the case of small tumors, or infectious/inflammatory processes affecting the nerve. The easiest way to approach the study of the hypoglossal nerve is to divide it in its main segments: intra-axial, cisternal, skull base and extracranial segment, tailoring the imaging technique to each anatomical area while bearing in mind the main disease entities affecting each segment.     

CT scanning of middle ear cholesteatoma: what does the surgeon want to know?

The history of surgery for middle ear cholesteatoma is of an evolution of techniques to meet the challenges of inaccessible disease and of post-operative cavity management. The concept has traditionally been of exploration guided by awareness and anticipation of all, possibly asymptomatic, complications. Modern imaging reliably demonstrates surgical anatomy, dictating the ideal approach, forewarns of complications and may reveal the extent of disease. An apparent resistance amongst otologists to universal CT scanning prior to mastoidectomy contrasts with the enthusiasm of skull base surgeons or rhinologists for appropriate imaging.     

Adult cranial dura I: intrinsic vessels

This is the first of two articles designed to provide user-friendly schematics of the adult dural vascular anatomy. It describes the intrinsic meningeal arteries and veins of the skull base/cranial vault and the dural partitions (the tentorium, falx cerebelli, and falx cerebri). The discussion of this anatomy is supplemented by illustrative pathologic insights. The second article focuses on the dural sinuses and their remaining tributaries from the brain, diplo?, and emissary veins from the extracranial soft tissues. This information will assist in interpreting neuroimaging studies, communications with clinicians, and teaching of this difficult subject.     

Multimodality Imaging Review of Anorectal and Perirectal Diseases With Histological,Endoscopic, and Operative Correlation,Part I: Anatomy and Neoplasms

A broad spectrum of pathology affects the rectum, anus, and perineum and understanding of its relevant anatomy is important in accurate reporting, particularly in rectal cancer. In this pictorial essay, correlative imaging, endoscopic, pathologic, and operative images are presented to illustrate normal anorectal anatomy and neoplastic conditions that affect the anus and rectum. A particular case-based focus is given to rectal adenocarcinoma with pelvic MR and surgical histopathology. Additionally, carcinoid tumor, gastrointestinal stromal tumor, condylomata acuminata, squamous cell carcinoma, melanoma, and metastatic disease about the rectum and anus are reviewed.     

CT and MRI features of ileostomies

OBJECTIVE: The purpose of this article is to describe CT and MRI features of normal anatomy, variants, and pathologic conditions of different ileostomies. CONCLUSION: Multiplanar imaging techniques are useful to identify the complications related to stoma construction and preexisting disease. Understanding the indications for ileostomy construction, surgical techniques, and postoperative anatomy is important for differentiating normal and abnormal imaging features.     

Surgical treatment of malignant tumors of the paranasal sinuses with involvement of the base of the skull

After 18 years of close cooperation between ORL and neurosurgery in the treatment of the base of the skull, the authors present their surgical conception and technique for the treatment of malignant tumors of the paranasal sinuses involving the base of the skull. Three basically different surgical procedures are possible: 1. Extracranial partial resection of the anterior base of the skull sparing the contents of the orbit. 2. Radical revision of superior maxilla, ethmoid bone, and base of the skull including exenteratio orbitae. 3. Combined intra-extracranial approach. An interdisciplinary cooperation and the combination of macro- and microsurgery will be more successful with respect to survival chances, functional and esthetic results.     

MR imaging of the nasopharynx and floor of the middle cranial fossa. Part I. Normal anatomy

The normal anatomy of the nasopharynx and floor of the middle cranial fossa was analyzed with magnetic resonance (MR) imaging. MR images from five healthy volunteers were correlated with whole-organ cryomicrotome sections from three cadavers. Anatomic connections exist between the paranasopharyngeal spaces and the surface structures of the skull base. These anatomic connections include the intimate relationship between the eustachian tube and the pharyngobasilar fascia, the attachment of the muscles of mastication and deglutition to the skull base, and vascular and nervous structures in the foramina. The inherent contrast between the soft tissues of the nasopharynx and related structures and the bone of the floor of the middle cranial fossa allowed excellent visualization of these anatomic connections.     

Paranasal sinuses and facial imaging: exploratory strategies

Advances in radiological and endoscopic imaging allow more accurate location and spread of nasosinusal diseases. These developments have led to a better understanding of sinusal anatomy and to widespread of surgical techniques as endoscopic sinus surgery. CT becomes the primary imaging modality for assessment of chronic rhinosinusitis and complex traumatic injury. Associated to CT, MRI is used to distinguish between inflammatory and neoplastic pathology and to assess lesions involving the skull base or intracranial structures. However, optimization of technical parameters according to the pathology is necessary.     

枕下乙状窦后入路磨除内听道的虚拟现实微创解剖研究

 目的 在构建虚拟现实解剖模型基础上探讨枕下乙状窦后入路微创磨除内听道的显微解剖证据。 方法 15例尸体头颅行头颅CT和MRI扫描,影像数据输入虚拟现实系统构建内听道及其周围结构的三维解剖模型。在颅盖和颅底中选择骨性标志点设计枕下乙状窦后入路磨除内听道内不同靶点的微创路径,观察测量和比较伴随路径方向和角度改变,其中解剖结构的显露情况。结果 模拟枕下乙状窦后入路磨除内听道的手术路径中清晰显示所包含的神经、血管等解剖结构的空间层叠顺序。测量和比较显示路径中骨性结构和迷路体积:路径a>路径b>路径c;路径中小脑半球体积:路径b>路径c>路径a;路径中面听神经复合体体积:路径b>路径a>路径c;差异均有统计学意义。结论 在计算机虚拟现实条件下,乙状窦后入路通过磨除岩骨到达内听道末端的模拟微创手术路径能够有效量化手术创伤和靶点显露情况,为手术操作的微创化发展提供指导信息。     

MR imaging evaluation of endoscopic cranial base reconstruction with pedicled nasoseptal flap following endoscopic endonasal skull base surgery

Introduction

Postoperative CSF leak is the most common complication of endoscopic endonasal approach (EEA) to skull base lesions. Endoscopic multilayer closure of skull base defect using pedicled nasoseptal flaps (NSF) based off the sphenopalatine artery reduces CSF leaks. EEA robustly expands in surgical arena, yet postoperative imaging evaluation remains poorly studied. This work illustrates normal MR imaging appearance of skull base reconstruction utilizing NSFs during immediate postoperative period.

Methods

We retrospectively identified patients who had skull base reconstructions utilizing NSFs following EEAs and immediate postoperative-enhanced brain MRI. NSFs and free grafts were evaluated for signal intensity, thickness, configuration, enhancement, vascular pedicle of NSF, relationship in multilayer reconstruction, and defect coverage. Imaging findings were correlated with surgical technique and CSF leaks.

Results

Twenty-eight patients had 26 multilayer reconstructions and 34 NSFs. Twenty-nine NSFs showed enhancing C-shaped arc at the skull base. Of those, 26 flaps (90%) were confidently identified by visualization of their vascular pedicles, 3 were not distinguishable from adjacent mucosa and pedicles were not identified. Five NSFs showed no enhancement (1 CSF leak). Twenty-seven enhancing NSFs approximated defects with close abutment to free grafts. One flap was displaced; one incompletely covered the defect (2 CSF leaks). Fisher exact test demonstrated an association between incomplete defect coverage and displacement of NSFs with CSF leak (P = 0.05).

Conclusion

Endoscopic skull base reconstruction utilizing NSF has characteristic MR imaging appearance. Non-enhancing mucosal gap or displacement of NSF may indicate incomplete defect coverage, identifying patients at risk for CSF leak.