A micro-computed tomography study of the sinus tympani variation in humans

BACKGROUND

The posterior part of the tympanic cavity comprises a depression called the sinus tympani (ST). The said structure is of outmost importance, e.g. in surgical procedures involving the middle ear, as a pathology (microbial biofilm or cholesteatoma) present in this difficult to access location might hinder its effective treatment. The aim of the study was to evaluate anatomical variants of the ST in human adult petrous bones. For this purpose, three-dimensional (3D) models of the ST were recreated from micro-computed tomography (CT) scans of 44 dry petrous bone samples (19 female, 25 male), applying 3D Slicer, Meshmixer and MeshLab software.

MATERIALS AND METHODS

Anatomical variants of the ST were classified in terms of both shape and surface configuration. The internal configuration of the ST was classified as heterogeneous - containing small bony trabeculae and crests up to 1.0 mm in size, contrasting to homogeneous ST that characterizes a relatively smooth interior, or mere presence of minor depressions and mild folds. Female STs were more bowl-shaped (57.9%) than saccular (42.1%), and had heterogeneous surface configuration (52.6%) compared to homogeneous (47.4%). On the contrary, male STs were more saccular (52.0%) rather than bowl-shaped (48.0%), and predominantly had a heterogeneous surface (84.0%) over homogeneous (16.0%).

RESULTS AND CONCLUSIONS

A complex combination of ST features comprised of a saccular shape and heterogeneous surface occurred in 52.0% of males and in 15.8% of females (a statistically significant difference; p = 0.0254, Fisher's exact test) seems to be clinically important because of its potential negative implication on health outcomes after surgery in the case of, for example, cholesteatoma, and it may also favour chronic pathological processes.

A computed tomography comprehensive evaluation of the ostium of the sphenoid sinus and its clinical significance

BACKGROUND

The purpose of this research was to evaluate the size of the sphenoid sinuses' ostia, the distance between them and the distance between the medial margin of the ostia and the median line in the Polish adult population.

MATERIALS AND METHODS

The analysis was undertaken as a retrospective study of 296 computed tomography (CT) scans of patients (147 females, 149 males) with no comorbidities in their sphenoid sinuses. The paranasal sinuses were investigated by using Spiral CT Scanner (Siemens Somatom Sensation 16), in the option Siemens CARE Dose 4D, without administering any contrast medium. Having obtained transverse planes, multiplans reconstruction tool was used in order to glean sagittal and frontal planes.

RESULTS

The average size of both sphenoid sinuses ostia was 0.31 cm for both genders (for females ranging from 0.1 to 0.5 cm and from 0.1 to 0.6 cm for males). The mean distance between both sphenoid sinuses ostia was 0.6 cm for both genders (the range for females was 0.1-1.4 cm, whereas 0.1-1.8 cm for males). The average distance between the medial margin of the ostium and the median line was 0.32 cm for both genders (0.31 cm for females in the range of 0-0.9 cm and 0.32 cm for males in the range of 0-1 cm).

CONCLUSIONS

Intraoperative identification of the sphenoid sinus ostia might prove difficult and their inadequate excision could lead to potential iatrogenic complications, hence detailed anatomical descriptions are still warranted in specific populations in order to perform safe and effective procedures.

Anatomical variations of the superficial ulnar artery: case series observed on historical specimens prepared by Ludwik Karol Teichmann

BACKGROUND

In this report we present a series of cases representing variant origin and course of the ulnar artery, namely the superficial ulnar artery, observed during the review of collection of historical specimens prepared in the 19th century by the prominent Polish anatomist Ludwik Karol Teichmann and his collaborators, exhibited in the Anatomy Museum of Jagiellonian University Medical College.

RESULTS

Three distinct variants of the superficial ulnar artery were found on anatomical specimens of the upper limb with arteries injected by using Teichmann's method. In case No. 1, the superficial ulnar artery originated from the brachial artery slightly above the interepicondylar line of the humerus. This aberrant vessel gave off the common interosseous artery in the upper half of the cubital fossa and then ran superficially to the bicipital aponeurosis and over the muscles arising from the medial epicondyle of the humerus. The cases No. 2 and 3 involved two similar variants of the superficial artery in which the common interosseous artery arose from the radial artery. In the unique case No. 4, the superficial ulnar artery arose from the radial artery.

CONCLUSIONS

The superficial ulnar artery shows diverse anatomy regarding its topography and blood supply territory. Orthopedic, hand, and plastic surgeons should be aware of anatomic variations of the SUA both in planning and in conducting surgeries of the upper limb.

Anatomy of the fundus of the internal acoustic meatus - micro-computed tomography study

The aim of this paper was to present micro-computed tomography (micro-CT) high resolution images of the fundus of internal acoustic meatus (FIAM) and characterise the normal appearance of its singular areas which are places of passage of numerous anatomical structures. By using micro-CT we obtain detailed volume rendering images presenting topography of the FIAM in 3-dimensional (3D) space. We figured out that 3D reconstructions obtained from micro-CT scans can precisely demonstrate all areas of the FIAM (facial nerve area, cochlear area, superior and inferior vestibular areas, singular foramen). Application of this technique allows finding out new anatomical structures like the foramen of the transverse crest, which is not described in literature. Hence, we estimated the size of each area of the FIAM by measuring their minimal and maximal diameter. In the studied material we did not find out any statistically significant difference between mean diameters calculated for infant and adult individuals.

The scaphocephalic skull of an adult male

The paper presents abnormal craniofacial morphology of an adult male afflicted with premature closure of the sagittal suture. The skull is well preserved and there are no visible traits of surgical management which would be aimed to correctcranial deformation. In consequence of the restricted cranial development, some diameters of the skull were significantly altered. Basically, cranial vault morphology fits apparently to the scaphocephaly, whereas the basic ranium and viscerocranium are altered only in minor degree.

Micro-computed tomography study of the abnormal osseous extensions of sella turcica

The paper presents anatomical considerations on the abnormal ossification, which occurred around the dorsum of the sella turcica in the human skull of the female individual. Probably the morphological alterations of the sellar region were associated with extensive heterotopic ossification of the dura mater attached to the dorsum of the sella turcica and the posterior clinoid processes. The analysis of gray values of the voxels representing the areas of abnormal ossification indicated on variation in bone density in the entire sample. We have established that the highest mineralisation of bony tissue occurred in the marginal parts of the osseous extensions deriving from the posterior clinoid processes. The ossified parts of dura mater attached to the posterior clinoid processes showed significantly higher content of the hydroxyapatite (1.9 g/cm3) than the dorsum of the sella turcica (1.0 g/cm3).

Enhancement of the focal depth in anatomical photography

Limited depth of field is one of the crucial disadvantages of macro photography because some details of the imagined object are blurred. This paper presents the benefits of using an algorithm which enhances focal depth in the close-up views of anatomical structures. The applied technique was based on combining a set of images of the same object (temporal bone) taken on different focal planes. In effect, a single image was generated which presented all details sharply across the photographed object. The extended depth of field of the composite image was reconstructed by CombineZP Image Stacking Software.

Possible compression of the atlantal segment of the vertebral artery in occipitalisation

The current study evaluates the passage of the atlantal segment of the vertebral artery through the atlas to the cranial cavity in the case of occipitalisation, and searches for potential bony obstacles that constrict the lumen of the vertebral artery. Morphometric analysis was performed of the ossified atlanto-occipital articulation of the dry adult male skull, particularly in the region of the posterior arch of the atlas. The distance between the floor of the right groove for the vertebral artery and the occipital bone was measured using a digital sliding caliper. On the left side, measurements of the diameters of the inlet and outlet of the canal for the vertebral artery were performed using the same technique. Fusion of the left portion of the posterior arch of the atlas with the occipital bone caused significant narrowing of the space around the normally existing groove for the vertebral artery, and converted it into the canal. The size of the intracranial opening of the canal for the vertebral artery was measured as 3.8 mm x 4.7 mm, whereas the inlet to the canal was 5.4 mm x 7.0 mm. The diameter of the canal decreases, particularly at the entrance into the cranial cavity; therefore, compression of the vertebral artery within the canal seems to be possible.

Geometry of the articular facets of the lateral atlanto-axial joints in the case of occipitalization

This study investigates if atlanto-occipital fusion affects the size and geometrical configuration of the articular facets of the atlanto-axial joint. Morphometric analysis was performed on the male adult skull, the occipital bone of which is assimilated with the first cervical vertebrae (the atlas). The perimeter, Feret's diameter, surface area, and circularity of the inferior articular fa-cets were measured. However, we did not observe significant bilateral differences in size of the inferior articular facets of the assimilated atlas compared to normal first cervical vertebrae. Geometrical conformation of the articular facets of the atlas and axis was assessed using a coordinate measuring machine (PMM - 12106, Leitz). The results obtained from this machine indicated that the inferior articular facets of the assimilated atlas presented asymmetrical orientation compared to the normal anatomy of the atlas. Hence, in the case of occipitalization, the gap between the articulating facets of the atlas and the axis was measured to be greater than in the normal atlanto-axial joint. Computer assisted tomography was applied to visualise the anatomical relationship between the inferior articular facets of the assimilated atlas and the corresponding facets located on the axis. In this case, radiographic examination revealed that the bilaterally articulating facets (inferior and superior) showed disproportion in their adjustment within the lateral atlanto-axial joints. Thus, we concluded that the fusion of the atlas with the occipital bone altered the geometry of the inferior articular facets of the atlas and influenced the orientation of the superior articular facets of the axis.

A case of occipitalization in the human skull

Occipitalization of the atlas is an osseous anomaly of the craniovertebral junction. The aim of this paper is to present an anatomical variant of the fused atlas with the occipital bone and discuss similar cases described in literature. The skull of an adult male analysed in this study belonged to the cranial collection of the Department of Anatomy of the Jagiellonian University, Medical Collage. A tight bony fusion between the anterior arch of the atlas, the left portion of the posterior arch, the lateral masses of the atlas, and the occipital bone was observed. Hence, the left and right superior articular facets of the atlas were fused with the corresponding occipital condyles. The anteroposterior dimension of both inferior articular facets was the same (20 mm), while the transverse diameter of the right one was considerably smaller (12 mm). The transverse diameter of the left inferior articular facets was 17 mm. The right and the left transverse process of the atlas were normally developed, each of them contained transverse foramen, and they were not fused with the occipital bone. The circumference of the foramen magnum was minimally diminished by the osseous structures of the atlas fused to the occipital bone. The sagittal and transverse diameters of the foramen magnum (38 mm x 34 mm) were within the normal range of variation. However, the asymmetrical anatomy of the inferior articular facets of the atlas give rise to speculation that movement in the atlantoaxial joint was disturbed by assimilation with the occipital bone.

Bilateral ossification of the stylohyoid ligament

This paper presents the case of an adult male skull with bilateral ossification of the stylohyoid complex. The total length of the stylohyoid complex amounts to 62 mm on the left side and 65 mm on the right side. Visual inspection of the stylohyoid revealed the presence of callosities that are located on both stylohyoid complexes at nearly the same level. These sites are regarded as the ossified attachments of the stylohyoid ligaments to the corresponding styloid processes. The skull studied is an example of extreme development of the stylohyoid complex, which could cause severe pain and a restriction of head and neck movement.

The clinical significance of the petroclinoid ligament

This report describes the topography and structure of the petroclinoid ligament with reference to its clinical significance. Observations of this ligament were performed on 24 sections of human heads. Remnants of the ossified form of this ligament were sought in 73 dry human skulls. It was found that the petroclinoid ligament existed as an anterior and posterior fold of the dura mater and stretched from the petrous apex and the anterior and posterior clinoid process respectively. We assessed the close proximity of this ligament to the oculomotor nerve. In one case we found a partially ossified posterior petroclinoid ligament, which appeared as a bony spike that arose posteriorly and inferiorly from the posterior clinoid process.

An atypical position of the foramen ovale

Visual inspection of a dry adult human skull revealed absence of a typical foramen ovale on the left side of the cranial base. The region of the foramen ovale was covered by an osseous lamina, which was continuous with the lateral pterygoid plate and thus formed a wall of an apparent canal, which opened on the lateral side of the pterygoid process. This canal is referred to as an oval canal (canalis ovalis), instead of the foramen ovale. It runs superiorly, medially from the infratemporal fossa, and opens into the middle cranial fossa. The altered osseous morphology of this basicranial region may affect the course of the neurovascular structures which pass through the foramen ovale. As a consequence, clinical symptoms could occur, including paresthesiae of the inner aspect of the cheek and compression and neuralgia of the mandibular nerve or its branches.

The ossified interclinoid ligament

The paper presents an anatomical description of the ossified interclinoid ligament which was found in a male human skull. In the case studied the ossified ligament exists as a bony bridge between the anterior and posterior clinoid processes on the left side of the skull. The length of this connection was measured as 5.0 mm, while its thickness was 3.2 mm. We conjecture that the presence of a considerably thick bony trabecula within the sella region might have had an impact on the course of the internal carotid artery or the oculomotor nerve, causing compression of these structures.

Modelling the calvarium diploe

The paper presents the effects of computer modelling of the inner structure of the calvarium from CT scans using MeeSoft Image Analyzer software. This software generates a model image, which can be enlarged and viewed from different angles without visible distortion or blurring of the contours. Similar manipulation with the original CT scan produces destructive effects, which hinder visualisation of the anatomical structures.