The Skull Base in the Evaluation of Sinonasal Disease

Pediatric Odontogenic and Paranasal Sinus Infections

Odontogenic and sinogenic infections are frequently encountered in the pediatric population. Although the diagnosis is often suspected clinically, imaging can play a significant role in localizing the site of infection, assessing for involvement of deep neck spaces, detection of abscess and other potentially life-threatening complications, and providing valuable information to help with treatment planning. This article reviews the general imaging considerations and anatomy relevant to odontogenic and paranasal sinus infections and describes the salient clinical and imaging features of infectious diseases of the dentition and sinuss.

Imaging of Skull Base Tumors

The skull base provides a platform for supporting the brain while serving as a conduit for major neurovascular structures. In addition to malignant lesions originating in the skull base, there are many benign entities and developmental variants that may simulate disease. Therefore, a basic understanding of the relevant embryology is essential. Lesions centered in the skull base can extend to the adjacent intracranial and extracranial compartments; conversely, the skull base can be secondarily involved by primary extracranial and intracranial disease. CT and MRI are the mainstay imaging methods and are complementary in the evaluation of skull base lesions. Advances in cross-sectional imaging have been crucial in the management of patients with skull base pathology, as this represents a complex anatomical area that is hidden from direct clinical exam. Furthermore, the clinician must rely on imaging studies for therapy planning and to monitor treatment response. It is crucial to have a thorough understanding of skull base anatomy and its various pathologies, as well as to recognize the appearance of treatment-related changes. In this review, we aim to describe skull base tumors and tumor-like lesions in an anatomical compartmental approach and present imaging methods that aid in diagnosis, management, and follow-up.

Malignant and Nonmalignant Sinonasal Tumors

Sinonasal tumors are rare, diverse, complex lesions with overlapping demographic and clinical features. Malignant tumors are more common, with a grave prognosis, and require biopsy for accurate diagnosis. This article briefly reviews the classification of sinonasal tumors and provides imaging examples and imaging characteristics of each clinically important nasal and paranasal mass lesions. Although there are no true pathognomonic imaging features, it is important for the radiologist to have a broad knowledge of the various CT and MR imaging findings that can help narrow the differential diagnosis and aid in early diagnosis and mapping of tumor for treatment planning.

Anatomy and Diseases of the Greater Wings of the Sphenoid Bone

The greater wings of the sphenoid bone (GWS) comprise the components of the sphenoid bone that make up most of the posterior orbital wall and form the anterior and medial parts of the floor of the middle cranial fossa. Many important skull base foramina, which transmit vital neurovascular structures, are present in these paired wings on either side of the central body of the sphenoid bone. A wide variety of diseases can affect the GWS, ranging from benign osseus lesions to malignant primary and secondary bone abnormalities. The complex three-dimensional curved (winged) shape of the GWS and the wide array of pathologic entities that affect this bone can make it challenging for the radiologist to report the imaging findings accurately, especially in relation to the important skull base foramina. The authors describe a systematic approach to understanding the three-dimensional anatomy of the GWS and review important diseases, with the aid of imaging examples. Useful imaging "pearls" that can help in making specific diagnoses are provided throughout the article. ^©RSNA, 2022.

Whole-body hybrid positron emission tomography imaging yields clinically relevant information in the staging and restaging of sinonasal tumors

Background

Whole‐body hybrid positron emission tomography (PET) imaging is increasingly used for sinonasal tumors. However, only empirical data exist on the additional, clinically relevant information derived from these techniques.

Methods

This study included 96 regionalized magnetic resonance imaging (MRI) of the sinonasal tract/neck and separate hybrid FDG‐PET/CT or FDG‐PET/MRI in 74 patients. Additional radiological information (ARI) obtained from each hybrid examination was analyzed and its clinically relevance was determined. Clinically relevant information (CRI) was categorized with regard to primary tumor site, regional lymph node metastases, distant metastases, second primary tumors, and non‐neoplastic findings.

Results

A total of 45/96 (46.9%) hybrid PET examinations revealed ARI. CRI was found in 32/96 (33.3%) examinations and concerned the primary tumor site (6.1%), regional lymph node metastases (4.1%), distant metastases (14.3%), second primary tumors (7.3%), and non‐neoplastic findings (5.1%).

Conclusions

Hybrid PET imaging yields additional radiological information translating into clinically relevant information in a substantial proportion of patients with sinonasal tumors.

MRI of Sinonasal Malignancies

ABSTRACT

Sinonasal cavity is an important subsite in head and neck tumors. There are a myriad of malignancies that present within this area. Adequate staging for treatment planning requires multimodality evaluation. Magnetic resonance imaging (MRI) forms an important component in the evaluation of sinonasal tumors. We sought to review the most common sinonasal tumors, including sinonasal anatomy, clinical features, and common imaging features. A literature review was performed to evaluate common sinonasal tumors. Owing to the different tissue types within the sinonasal cavity, there are multiple different tumor pathologies within the sinonasal compartment. Most present in adults although some present in the young. Many of these tumor types have imaging overlaps, although some have a characteristic appearance. MRI can aid in soft tissue delineation, evaluation of multicompartmental extension, intracranial spread, and perineural spread. Sinonasal tumors are a heterogeneous group for which soft tissue delineation via MRI forms an important role in ensuring adequate treatment planning to improve outcomes, decreasing morbidity, and improve functional outcomes.

Imaging of adult nasal obstruction

The commonest causes of nasal obstruction are rhinitis and chronic rhinosinusitis, which affect up to 30% and 14% of the adult population, respectively. The global financial burden is huge, estimated at $5 billion for rhinitis and $8.6 billion for chronic rhinosinusitis per annum in the USA. On referral for imaging, computed tomography (CT) is indicated initially when there is a suboptimal response to medical treatment of these mucosal diseases or there are "red flags," such as persistent unilateral obstruction, epistaxis, pain, and orbital or neurological symptoms. A mass visible at rhinoscopy or endoscopy in the nose or nasopharynx and lymphadenopathy are further indications. The anterior (cartilaginous) nose plays a key role in the aetiology of nasal obstruction as it accounts for 50-75% of the total resistance to airflow in the upper airway. It has been ignored in the imaging literature, but extensively evaluated by clinicians using a range of methods, including CT. Oblique reconstructions perpendicular to the parabolic curve of lamellar airflow provide accurate assessment of the anterior nose. A thorough and systematic approach to assessing the nose addresses the discrepancy between imaging and clinical evaluation of structural causes of nasal obstruction, especially septal deviation, reported in the surgical literature. Nasal tumours are a very uncommon cause of nasal obstruction; magnetic resonance imaging is commonly performed to assess their full extent and improve the specificity of diagnosis.

The Appearance of The Infraorbital Canal and Infraorbital Ethmoid (Haller's) Cells on Panoramic Radiography of Edentulous Patients

Objectives. The aim of the study is to detect the prevalence and the characteristics of infraorbital canal and Haller's cells on panoramic radiography of edentulous patients. Methods. The study group comprised 291 panoramic radiographs of edentulous patients. Radiographs were interpreted for the visibility and characteristics of infraorbital canal and Haller's cells. For classification of infraorbital canal, a method based on the image characteristics of the border of the canal (Types I, II, and III) was used. Haller's cells were grouped according to the number and the shape of loculations. Results. Infraorbital canal was observed in 246 (84.6%) radiographs. The most prevalent of the observed canals were Type III for both sides (39.9 % for right and 32.3% for left side). The visibility of Haller's cells was 23.7%. The frequencies of Haller's cells' visibility were approximately equal for both genders. There is no significant difference between genders for the visibility of infraorbital canal and Haller's cells. Conclusions. The surgeons, implantologists, and radiologists should take into consideration infraorbital canal and Haller's cell for planning implant surgery of maxillary anterior region and undefined orofacial pain for edentulous patients.

Imaging of Paranasal Sinuses and Anterior Skull Base and Relevant Anatomic Variations

This article reviews the normal anatomy and variants of the anterior skull base and sinonasal cavities that are relevant to endoscopic sinus and skull base surgery. Radiologists should be aware of sinonasal anatomy that can be impediments to surgical access and increase risk of vascular or cranial nerve injury during surgery. Imaging features of the paranasal sinuses and anterior skull base pathologies are also discussed.