Pictorial review: radiology of the sphenoid bone

The Evaluation of Variations in Patterns of Sphenoid Sinus Pneumatization Using Computed Tomography in a South Indian Population

Background and objective

Knowledge about sphenoid sinus pneumatization is critical for skull base surgeries and functional endoscopic sinus surgery (FESS) in order to avoid serious complications like postoperative meningitis, sinusitis, cerebrospinal fluid (CSF) rhinorrhea, and intracranial hematoma. In this study, we aimed to assess the proportion of anatomical variants in sphenoid sinus pneumatization and to determine the common sphenoid pneumatization pattern in a South Indian population.

Methods

This retrospective study was conducted over a period of six months from July 2019 to December 2019 among 573 patients who underwent non-contrast CT (NCCT) or contrast-enhanced CT (CECT) of the brain, paranasal sinuses (PNS), orbit, and face.

Results

Most of the patients were in the age group of 20-39 years. The male-to-female ratio was 2.45:1. Among the posterior extensions, the most common variant was type D, followed by type C, type B, and type A. Among the clival extensions, the most common variant was Cliv-A, followed by Cliv-B, Cliv-C, and Cliv-D. The most common lateral wall pneumatization was bilateral lateral wall pneumatization followed by unilateral sinus wall pneumatization. Lat-A was the most common lateral wall pneumatization pattern followed by Lat-D, Lat-B, and Lat-C.

Conclusion

Our study intends to classify the sphenoid sinus pneumatization pattern and identify the most common variant among them, thereby guiding the skull base and FESS surgeons in choosing the correct mode of the operative procedure and also anticipating and avoiding complications of surgery.

Cone Beam Computed Tomographic Evaluation of Intracranial Physiologic Calcifications

OBJECTIVE

The aim of the present study was to evaluate the incidence of physiologic intracranial calcifications detected in cone beam computed tomography (CBCT) images of a Turkish subpopulation.

METHODS

The CBCT image of the full head of 573 patients taken between 2015 and 2018 was evaluated retrospectively. The prevalence of habenular calcification, petroclinoid ligament, coroid plexus, interclinoid ligament (ICL), and carotico-clinoid ligament (CCL) calcifications was investigated. The age and gender of the patients were recorded.

RESULTS

Intracranial calcification was found in 190 (33.1%) of 573 cases. The frequency of physiological calcifications is respectively; 19.2% were found as habenular, 4.88% as ICL, 3.83% as CCL, 2.7% as petroclinoid ligament, and 2.4% as choroid plexus. 38.2% of the women and 29.3% of the men had intracranial calcification. In 4 patients, both ICL and CCL ossification were detected. No statistically significant relationship was found between age, gender, and calcifications.

CONCLUSION

Cone beam computed tomography is a widely used imaging technique for dental diagnosis and treatment. Intracranial physiological calcifications may be a common incidental finding of CBCT scans.

Imaging sphenoid diseases

In this review we provide comprehensive analysis of the imaging features of diseases affecting the sphenoid sinus, including a large and heterogeneous spectrum of pathologies such as sinusitis, pseudotumours, bony pathologies, and tumours. Clinical symptomatology related to sphenoid pathologies is often non-specific and patient clinical examination and endoscopic investigations are not definitive; thus, radiological imaging is mandatory for diagnosis. Strengths and limitations of both morphological and functional imaging methods such as computed tomography (CT), magnetic resonance imaging (MRI), and combined positron-emission tomography/computed tomography (PET/CT) have been considered and integrated into a well-defined clinical context in order to recognise specific imaging features and to underline their clinical relevance for an early and accurate diagnosis. An overview of several sphenoid conditions is herein selected with a didactic objective including both common and less common diseases.

A comparative study of the deviation of the menton on posteroanterior cephalograms and three-dimensional computed tomography

Purpose

Facial asymmetry has been measured by the severity of deviation of the menton (Me) on posteroanterior (PA) cephalograms and three-dimensional (3D) computed tomography (CT). This study aimed to compare PA cephalograms and 3D CT regarding the severity of Me deviation and the direction of the Me.

Materials and Methods

PA cephalograms and 3D CT images of 35 patients who underwent orthognathic surgery (19 males and 16 females, with an average age of 22.1±3.3 years) were retrospectively reviewed in this study. By measuring the distance and direction of the Me from the midfacial reference line and the midsagittal plane in the cephalograms and 3D CT, respectively, the x-coordinates (x₁ and x₂) of the Me were obtained in each image. The difference between the x-coordinates was calculated and statistical analysis was performed to compare the severity of Me deviation and the direction of the Me in the two imaging modalities.

Results

A statistically significant difference in the severity of Me deviation was found between the two imaging modalities (Δx=2.45±2.03 mm, p<0.05) using the one-sample t-test. Statistically significant agreement was observed in the presence of deviation (k=0.64, p<0.05) and in the severity of Me deviation (k=0.27, p<0.05). A difference in the direction of the Me was detected in three patients (8.6%). The severity of the Me deviation was found to vary according to the imaging modality in 16 patients (45.7%).

Conclusion

The measurement of Me deviation may be different between PA cephalograms and 3D CT in some patients.

Classification and characteristics of pterygoid process fracture associated with maxillary transverse fracture

OBJECTIVE

This study aimed to classify pterygoid process fractures associated with maxillary transverse fractures.

STUDY DESIGN

Pterygoid process fractures in 100 patients with maxillary transverse fractures were observed 2- and 3-dimensionally using image processing software. Fracture line course and height and sphenoid sinus involvement were recorded.

RESULTS

Pterygoid process fractures were classified as follows: class I, vertical (simple separation between medial and lateral plates); or class II, transverse (3 subcategories according to location of fracture line: II-1, within pterygoid fossa; II-2, above pterygoid fossa, not extending to sphenoid sinus floor; II-3, above pterygoid fossa, involving sphenoid sinus floor). Class I fracture was observed on 5 sides (2.7%); II-1, on 125 (66.5%); II-2, on 36 (19.1%); and II-3, on 22 (1.7%).

CONCLUSIONS

Pterygoid process fractures were predominantly near the upper edge of the pterygoid fossa. Pneumatization of the pterygoid process is a risk in fractures involving the sphenoid sinus floor.

Imaging of the central skull base

The central skull base (CSB) constitutes a frontier between the extracranial head and neck and the middle cranial fossa. The anatomy of this region is complex, containing most of the bony foramina and canals of the skull base traversed by several neurovascular structures that can act as routes of spread for pathologic processes. Lesions affecting the CSB can be intrinsic to its bony-cartilaginous components; can arise from above, within the intracranial compartment; or can arise from below, within the extracranial head and neck. Crosssectional imaging is indispensable in the diagnosis, treatment planning, and follow-up of patients with CSB lesions. This review focuses on a systematic approach to this region based on an anatomic division that takes into account the major tissue constituents of the CSB.

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.

Biometric study of the optic canal during cranial development

To study optic canal dimensions and symmetry during cranial development, 146 silicon rubber left- and right-side models of the optic canal were cast from 51 dry skulls and 22 individual bones. The sample was divided in three age groups: fetuses (including newborns), children and adults with ages ranging from seven months of fetal life to 68-year-old. A digital caliper was used to measure the optic canal orbital and cranial diameters as well as model length. Results for the right and the left sides were, respectively, in millimeters: a) Maximum diameter of the orbital opening: fetuses, 4.68/4.47--children, 5.51/5.41--adults, 5.43/5.34; b) Minimum diameter of the orbital opening: fetuses, 2.89/2.84--children, 3.54/3.61--adults, 3.78/3.73; c) Diameter of the cranial opening: fetuses, 3.79/3.76--children, 4.67/4.72--adults, 5.24/5.43; d) Length of the optic canal: fetuses, 3.27/3.05--children, 3.93/3.71--adults 4.94/5.21. The diameter of the cranial opening of the optic canal increases significantly (p < 0.001) during the fetal period and throughout child and adulthood. The greater and smaller orbital apertures increase during the fetal period and during childhood, keeping the same size in adulthood. Optic canal length increases at some point between childhood and adulthood. Concerning symmetry, the only significant difference found was greater right than left optic canal diameter on the orbital side.

Imaging of the nasopharynx and skull base

The prerequisite for the correct diagnosis and accurate delineation of skull base lesions is familiarity with the complex anatomy of the skull base. Imaging plays a central role in the management of skull base disease because this region is often difficult to evaluate clinically. CT and MR imaging are complementary; they are often used together to demonstrate the full disease extent. This article focuses on the critical anatomy of the skull base and how this knowledge contributes to accurate disease assessment.

Imaging of the nasopharynx and skull base

The prerequisite for the correct diagnosis and accurate delineation of skull base lesions is familiarity with the complex anatomy of the skull base. Imaging plays a central role in the management of skull base disease because this region is often difficult to evaluate clinically. CT and MR imaging are complementary; they are often used together to demonstrate the full disease extent. This article focuses on the critical anatomy of theskull base and how this knowledge contributes to accurate disease assessment.

Compartments of the adult parasellar region

In the infant the region lateral to the sella turcica which is traditionally termed the 'cavernous sinus' is composed of 3 individual compartments. The aim of this study was to demonstrate a similar compartmentation of the adult cavernous sinus and to identify and quantify the adipose bodies which are located within the compartments. The region of the cavernous sinus in 136 adults was analysed by microdissection and histology. We demonstrate that in 66% of the cavernous sinus in adults is composed of at least 2 compartments and in 22% it is made up of 3. Assimilating the renaming in infants we termed the compartments 'pterygopalatine', 'orbital' and 'lateral sellar'. The pterygopalatine and orbital compartments are connected with extracranial tissue spaces via the superior orbital fissure and contain characteristic adipose bodies. Exact topographic descriptions and measurements of the compartments and their adipose bodies are provided. Our study clearly defines compartmentation of the adult parasellar space in most individuals and thus changes the anatomical view of this space. The direct connection of 2 of these compartments with extracranial tissue spaces and the measurements of their adipose bodies are of interest for surgeons and neuroradiologists.

Imaging the sphenoid sinus: pictorial essay

This paper focuses on the spectrum of sphenoid sinus lesions that may be seen radiologically and the mapping of disease extent. Imaging plays a central role in the assessment of sphenoid sinus disease. Although primary sphenoid sinus disease is uncommon, this sinus is nevertheless affected secondarily by a variety of pathological processes.