An Anatomorphometric Study of Occipital Spurs and Their Association With Dental Occlusion

Background and objective The occipital spur (OS) can be described as an abnormal elongation of the external occipital protuberance (EOP); its etiology is multifactorial and may involve biomechanical, immunological, and/or genetic factors. This study aimed to determine the frequency and characteristics of elongated EOP or OS as well as the relationship of OS with occlusion in a group of Turkish dental patients. Materials and methods Lateral cephalometric radiographs of 1925 patients taken in 2022 were retrospectively analyzed. The frequency, types, and dimensions of OS were determined based on gender and age groups. Molar occlusion and incisal bite were also evaluated. Results Of the 1925 patients, 679 were males and 1246 were females. The mean age of the cohort was 18.17 ±5.03 years (range: 4-61). OS was detected in 483 (25.1%) patients and was more common in males (p<0.001); 133 (27.5%) of the OSs were flat, 247 (51.1%) crest, and 103 (21.3%) spin type. The incidence of OS increased depending on age groups (p<0.001). There was no statistically significant association between OS presence and molar occlusion (p>0.05). However, a statistically significant association was observed between anterior incisal bite (p=0.001) and OS presence. There was a statistically significant difference in terms of OS sizes in males and females; the sizes of OS were larger in males than in females (length: p<0.05, base and thickness: p<0.001). Conclusions The frequency of OS was quite high in our cohort; it was more common and of larger size in males and older age groups. The most common type was the crest type. While there was no statistically significant association between OS frequency and molar occlusion, there was a significant relationship with incisal bite. The frequency of OS was highest in people with anterior crossbite.

Relationship of the Fusion Stage of Spheno-Occipital Synchondrosis with Midpalatal and Zygomaticomaxillary Sutures on Cone-Beam Computed Tomography Scans of Patients Aged Between 7 and 21 Years

Objective

This study assessed the relationship of the fusion stage of spheno-occipital synchondrosis (SOS) with midpalatal (MPS) and zygomaticomaxillary (ZMS) sutures on cone-beam computed tomography (CBCT) scans of 7 to 21-year-old patients.

Methods

This cross-sectional study evaluated the CBCT scans of 176 patients between 7 and 21 years presenting to a maxillofacial radiology clinic. The fusion stage of SOS was determined using a five-stage classification system. The percentage of opening depth of MPS was measured on two middle coronal cuts in the anterior and posterior half of the palate. To assess ZMS, suture fusion was evaluated in four age groups in the axial cut visualizing its maximum length. Data were analyzed using the Kruskal-Wallis, Mann- Whitney U, and Bonferroni tests and regression models.

Results

The percentage of MPS opening significantly decreased in both the anterior and posterior halves with age (p<0.002). With an increase in SOS grade, the percentage of MPS opening in both the anterior and posterior halves significantly decreased (p<0.001). By an increase in the ZMS stage, the SOS grade significantly increased (r=0.565, p<0.001).

Conclusion

The MPS opening percentage in the anterior and posterior halves decreased with age, with a greater reduction in the posterior half. A significant inverse correlation exists between the SOS fusion stage and the percentage of MPS opening. In SOS grades I-III, the mean percentage of MPS opening was 100% in all age groups (with the highest frequency of ZMS stage I), indicating a higher chance of success for orthodontic treatments such as rapid maxillary expansion in these individuals.

Full-endoscopic technique for posterior fossa decompression in Chiari malformation type I: An anatomical feasibility study in human cadavers

Although endoscope-assisted techniques have been described, a full-endoscopic approach is yet to be performed for posterior fossa decompression (PFD) in Chiari malformation type I (CM-I). This study aims to describe the full-endoscopic PFD technique and evaluate its feasibility. Five fresh-frozen anonymized adult human cadavers were operated on using an endoscope with an oval shaft cross-section with a diameter of 9.3 mm, a working length of 177 mm, and a viewing angle of 20°. It also had an eccentric working channel with a diameter of 5.6 mm, a light guide, a sheath for continuous irrigation, and a rod lens system. The instruments were introduced from the working channel. Posterior craniocervical structures were dissected, and PFD was achieved. The planned steps were performed in all five cadavers. The endoscope was introduced to the posterior craniocervical region, dissecting the structures to easily expose the suboccipital bone and C1 posterior arch. Important structures, such as the C1 posterior tubercle, rectus capitis posterior minor muscles, and posterior atlantooccipital membrane, were used as landmarks. PFD was feasible even with the dural opening. Using the full-endoscopic approach, posterior craniocervical structures can be reached, and PFD can be performed successfully. The instruments used are well-defined for spinal usage; thus, this full-endoscopic technique can be widely used in the surgical treatment of patients with CM-I.

Trabecular volumetric bone mineral density of the occipital bone at preferred screw placement sites measured by quantitative computed tomography

This study aimed at quantifying trabecular volumetric bone mineral density (vBMD) at the external occipital protuberance (EOP) and the upper cervical spine. A retrospective review of patients who underwent non-contrast enhanced computed tomography of the cervical spine that included the occipital bone up to the EOP between 2007 and 2020 was conducted. Measurements of trabecular vBMD were performed in the occipital midline area, with the region of interest extending 4.5 mm above and below the center of the EOP, as well as the C1 lateral masses and the C2 vertebral body using asynchronous quantitative computed tomography. Eighty-six patients (female, 37.2%) were included for analysis. The patient population was 81.4% Caucasian with a mean ± SD age of 62.3 ± 13.1 years. Total bone thickness at the EOP was 16.7 ± 3.4 mm, with a ratio of trabecular to total bone thickness of 0.44. Trabecular vBMD (mean ± SD) was significantly higher at the EOP than at C1 and C2 (EOP = 612.3 ± 145.8 mg/cm³ , C1 average = 290.3 ± 66.5 mg/cm³ , C2 = 305.8 ± 78.8 mg/cm³ ; p < 0.001). A significant strong correlation between trabecular vBMD of C1 and C2 was observed (r = 0.744; p < 0.001), but only low correlations between the EOP and C1 (r = 0.295; p = 0.008) and C2 (r = 0.413; p < 0.001). In individuals > 65 years of age, cervical vBMD was significantly lower, but remained high at the EOP. Clinical significance: Trabecular vBMD at the EOP is significantly higher than at the upper cervical vertebrae and remains high in older populations. Together with morphological information about the occipital bone, these results might be helpful for occipitocervical fixation when deciding about uni- or bicortical screw placement at the EOP.

Reduction of giant parietooccipital fibrous dysplasia using dynamic mirror image guidance: a case report and review of the literature

BACKGROUND

Craniofacial fibrous dysplasia (CFD) typically occurs in the facial bones and anterior cranial vault and can produce both disfigurement and functional limitations for patients disfigurement. Treatment consists of reducing the abnormal bone. Bone contouring can become challenging when the exposure does not extend to the corresponding normal contralateral structures for comparison or when normal landmarks are not available, which may compromise the overall aesthetic outcome. We describe a technique using dynamic mirroring to accurately contour the involved part of the cranium in a case of giant CFD.

OBSERVATIONS

A 49-year-old male presented with a giant deforming fibrous dysplasia of the right mastoid and parieto-temporo-occiput that was causing functional limitations due to the size of the bony mass. This was managed with multidisciplinary bony reduction. Several neurovascular structures were in proximity to the areas of planned drilling of the expansile lesion, and dynamic mirroring of the uninvolved left skull was utilized to maximize safety and symmetry of reduction. High-speed drilling of the right occipital bone was performed until the navigation system alerted the surgeon that symmetric depth had been achieved. There were no complications from the procedure and this technique maximized the limits of symmetric reduction without significantly increasing surgical complexity or duration.

LESSONS

Dynamic mirroring of bony structures in the posterior cranium is not commonly employed in neurosurgical practice. This technique may help improve the aesthetic outcomes of bony reduction in craniofacial dysplasia and a variety of similarly managed bony lesions, contour cranioplasties, and in unilateral craniosynostosis surgery.

Quantitative anatomy of primary ossification centres of the lateral and basilar parts of the occipital bone in the human foetus

BACKGROUND

Computed tomography (CT)-based quantitative analysis of primary ossification centres in the cranium has not been carried out to date due to the limited availability of the foetal human material. Detailed morphometric data about the development of primary ossification centres in human foetuses may be useful in the early detection of developmental defects. Understanding the growth and development of the occipital bone is crucial in assessing the normal and pathological development of the cranial base, and the cranium as a whole.

MATERIALS AND METHODS

The study material comprised 37 human foetuses (16 males and 21 females) aged 18-30 weeks of gestation. Using CT, digital image analysis software, three-dimensional reconstruction and statistical methods, the size of the primary ossification centres of the lateral and basilar parts of the occipital bone was evaluated.

RESULTS

The morphometric characteristics of primary ossification centres of the lateral and basilar parts of the occipital bone display neither sex nor laterality differences. These ossification centres grow linearly with respect to their sagittal and transverse diameters, projection surface area and volume.

CONCLUSIONS

The obtained morphometric data of primary ossification centres in the lateral and basilar parts of the occipital bone may be considered as normative for their respective prenatal weeks and may contribute to the estimation of gestational ages and the diagnostics of congenital defects.

A golden ratio for foramen magnum: an anatomical pilot study

BACKGROUND

The foramen magnum (FM) is an important landmark because of its close relationship to key structures such as the brainstem and spinal cord, an extension of the medulla oblongata. Because of the similarity in their shape, the existence of a relationship between cranial length and anteroposterior diameter of the FM, and between cranial width and transverse diameter of the FM may reveal the magnificent harmony of the skull and FM. Based on this idea, we investigated the existence of this harmony in skulls that we used in our study.

MATERIALS AND METHODS

In this study, 60 adult dry skulls belonging to the Turkish population were examined. The anteroposterior and transverse diameters of the foramen magnum and the length and width of the skull were measured. Measurements were made directly on the skull using a digital sliding caliper. New indices and ratios were applied with those measurements.

RESULTS

Our study suggests that FM width and FM length could be estimated by using the cranial length and cranial width measurements in the skull by accepting the mean of these coefficients (4.62) as the golden ratio. The average of the coefficients of cranial width to FM width ratio [4.62 ± 0.35 (95% CI: 4.52-4.70)] and the average of the coefficients of cranial length to the FM length ratio [4.62 ± 0.50 (95% CI): 4.49-4.76)] were found to be equal to each other. In order to check the accuracy of this hypothesis, FM width and FM lengths were estimated with the help of new equations.

CONCLUSIONS

In the present study, the ratio between the anteroposterior and transverse diameters of both FM and the cranium was estimated at 4.62, indicating a magnificent harmony between cranial and subcranial structures. With this ratio, it is easy to estimate FM's size based on simple cranial measurements.

Immersive Surgical Anatomy of the Craniocervical Junction

With the advent and increased usage of posterior, lateral, and anterior surgical approaches to the craniocervical junction (CCJ), it is essential to have a sound understanding of the osseous, ligamentous, and neurovascular layers of this region as well as their three-dimensional (3D) orientations and functional kinematics. Advances in 3D technology can be leveraged to develop a more nuanced and comprehensive understanding of the CCJ, classically depicted via dissections and sketches. As such, this study aims to illustrate - with the use of 3D technologies - the major anatomical landmarks of the CCJ in an innovative and informative way. Photogrammetry, structured light scanning, and 3D reconstruction of medical images were used to generate these high-resolution volumetric models. A clear knowledge of the critical anatomical structures and morphometrics of the CCJ is crucial for the diagnosis, classification, and treatment of pathologies in this transitional region.

Ectopic Cerebellar Tissue in the Occipital Bone: A Case Report

Ectopic cerebellar tissue has only been described in isolated case reports, with only two reported cases in adult patients. We report the case of a 63-year-old woman with progressive, medically refractory headaches. A scan showed an intraosseous lesion of the midline occipital bone. Surgical resection of the soft tissue lesion was undertaken. Her headaches ceased postoperatively. Histopathological analysis revealed cerebellar cortical tissue with a surrounding meningothelial cell layer, characteristic of cerebellar ectopia. This is the second reported case of an intraosseous location of this lesion, and only the third case described in an adult patient. Our findings illustrate a rare cause of headaches and support the therapeutic roles of surgical treatment for this extremely rare condition.

Maturation of the human foetal basioccipital: quantifying shape changes in second and third trimesters using elliptic Fourier analysis

During prenatal development, the brain is considered the best maturation criterion for the estimation of foetal physiological age, regardless of the conditions of pregnancy. Unfortunately, the brain lyses very quickly after death, but fortunately, the brain also has a major influence over osseous structures of the cranial base during development. Therefore, we considered the osseous structures of the cranial base potential indirect maturation indicators of foetal age. Because of its early formation and robustness, the basioccipital is a cranial base bone that is often used for studies in biological anthropology. Studies generally use conventional morphometry and bone size ratio to highlight morphological changes occurring during the foetal period and to create age estimation methods. These methods usually define thresholds beyond which the morphology of the basioccipital changes, but do not fully consider the form that might be valuable precisely to visualize its development or improve age estimation methods. Using geometric morphometric methods, the present study aims to analyse the development of the basioccipital during the second and third trimesters of foetal life by quantifying and visualizing shape changes in the inferior view. Basioccipital shapes are used as direct indicators of the maturation of the cranial base and as indirect indicators of the maturation of the brain and, by extension, the whole body. A sample of 221 anonymized computed tomographic (CT) scans of normal foetuses, ranging from 18 to 41 gestational weeks (GW), was used. Elliptic Fourier analysis (EFA) was used to quantify the basioccipital outline, and maturation stages were established to visualize shape changes with a principal component analysis. Our study allowed us precisely to quantify and continuously visualize shape changes occurring during prenatal life. Additionally, this study provides the first evidence of two distinct linear shape trajectories of the basioccipital. Foetuses aged between 18 and 26 GW have a rapid shape change with well-individualized stages, whereas shape changes are less visible in the second trajectory (27-41 GW). Furthermore, intra-stage shape variation is higher for the basioccipital at the beginning of the second and third trimesters than at the first trimester. By using geometric morphometric methods and EFA, this study shows that it was possible to go beyond classical methods. Indeed, the developed methodology enabled the first quantification of the overall shape changes of the basioccipital between gestational ages. The morphological shape changes throughout the foetal period can be useful for anthropological studies and provide new perspectives for immature age estimation methods.

The temporomandibular joint: pneumatic temporal cells open into the articular and extradural spaces

The pneumatisation of the articular tubercle (PAT) of the temporal squama isa rare condition that modifies the barrier between the temporomandibular joint(TMJ) space and the middle cranial fossa. During a routine examination of thecone-beam computed tomography (CBCT) files of patients who were scannedfor dental medical purposes, we identified a case with multiple rare anatomicvariations. First, the petrous apex was bilaterally pneumatised. Moreover, bilateraland multilocular PAT were observed, while on one side it was further found thatthe pneumatic cells were equally dehiscent towards the extradural space and thesuperior joint space. To the best of our knowledge, such dehiscence has not previouslybeen reported. The two temporomastoid pneumatisations were extendedwith occipital pneumatisations of the lateral masses and occipital condyles, thelatter being an extremely rare evidence. The internal dehiscence of the mandibularcanal in the right ramus of the mandible was also noted. Additionally, doublemental foramen and impacted third molars were found on the left side. Suchmultilocular PAT represents a low-resistance pathway for the bidirectional spreadof fluids through the roof of the TMJ. Further, it could add to a morphologicalpicture of hyperpneumatisation of the posterior cranial fossa floor, which couldsignify the involvement of the last four cranial nerves in the clinical picture of TMJpain.

The First Histological Analysis of the Tissues Lining the Fossa Navicularis: Insights to its Etiology

The fossa navicularis (FN) is an anatomical variant on the ventral surface of the basilar part of the occipital bone that, to date, has only been investigated in bone specimens. We aim to clarify the structure of the fossa navicularis by gross anatomical, radiological, and histological methods. The FN was found in the occipital bone of the Caucasian male cadaver. There was no bony or histological continuity between the FN and posterior cranial fossa. The histological analysis found that the overlying tissue was composed of loose connective tissue with a mixture of collagen and elastic fibers and a vascular matrix including arteries, veins, and capillaries. There was no evidence of lymphoid, glandular, or notochordal tissues. As no previous studies have performed histological analysis of the FN, this report adds to our knowledge of tissues that are involved in its formation.

Unique Image Characteristics of an Occipital Primary Chondroblastic Osteosarcoma: A Rare Case Report and a Brief Literature Review

Primary osteosarcomas of the skull and skull base are rare and comprise < 2% of all skull tumors. In head and neck osteosarcomas, the chondroblastic subtype occurs most frequently, which has an exceedingly poor outcome, but its image characteristic remains unknown. Herein, we report a case in the right occipital bone of the skull base and the unique characteristics of image. Pathologic examination of the surgical specimens led to the diagnosis of chondroblastic osteosarcomas. We believe those image characteristics can improve the understanding of skull chondroblastic osteosarcoma and the preoperative diagnosis.

The size and shape of the foramen magnum in man

Background:

The foramen magnum (FM) has garnered broad interest across the disciplines of anthropology, comparative anatomy, evolutionary biology, and clinical sciences. Most studies regarding the structure of the FM in humans have been intrapopulation morphometric studies rather than interpopulation morphologic studies. The few studies assessing the morphology of the foramen have utilized ambiguous and subjective descriptors to describe foraminal shape and are, consequently, difficult to reproduce. Therefore, detailed study of FM shape among craniofacially and geographically diverse populations through reproducible methods is warranted.

Objectives:

The aim of this study was to assess intersex and interpopulation differences in FM size and shape among diverse populations.

Materials and Methods:

The study analyzed 152 FMs of varied sex and race via traditional and geometric morphometric methods.

Results and Conclusions:

The study demonstrates that, within each distinct population, the size of the FM is significantly larger in males than in females; however, there are no significant differences in the shapes of the foramina between sexes. However, when comparing different populations to one another, there are significant differences with regard to both the size and shape of the FM. This study also presents a new model of FM ontogeny. Specifically, the growth occurring between the anterior and posterior foraminal boundaries before 5 years of age predicts the ultimate shape of the adult FM.

Skull sclerosing epithelioid fibrosarcoma: A case report and review of the literature

Sclerosing epithelioid fibrosarcoma (SEF) is an unusual variant of fibrosarcoma that was previously considered to be a low-grade tumor with an indolent course. The tumor occurs most commonly in the soft tissue of the limb, trunk, head and neck, and occasionally in the bone and visceral organs. The skull is a rare primary site for SEF, with only 3 cases reported to date. The current study reports a case of SEF occurring in the occipital bone of a 24-year-old man, who lacked neurological symptoms. Imaging revealed a large mass emanating from the occipital bone and involving the superior sagittal sinus, torcular herophili and adjacent brain tissue. Histological and immunohistochemical characteristics confirmed the diagnosis of SEF. The patient experienced local recurrence and distant metastasis at 10 and 15 months, respectively, subsequent to the resection of the primary mass. The current case and review of the literature suggest that skull SEF may behave clinically as an aggressive malignant sarcoma. Radiological findings indicated the biological and histopathological characteristics of the tumor. Thus, its clinical behavior and certain imaging features may suggest this diagnosis.

Introducing Computed Tomography Standards for Age Estimation of Modern Australian Subadults Using Postnatal Ossification Timings of Select Cranial and Cervical Sites(.)

Contemporary, population-specific ossification timings of the cranium are lacking in current literature due to challenges in obtaining large repositories of documented subadult material, forcing Australian practitioners to rely on North American, arguably antiquated reference standards for age estimation. This study assessed the temporal pattern of ossification of the cranium and provides recalibrated probabilistic information for age estimation of modern Australian children. Fusion status of the occipital and frontal bones, atlas, and axis was scored using a modified two- to four-tier system from cranial/cervical DICOM datasets of 585 children aged birth to 10 years. Transition analysis was applied to elucidate maximum-likelihood estimates between consecutive fusion stages, in conjunction with Bayesian statistics to calculate credible intervals for age estimation. Results demonstrate significant sex differences in skeletal maturation (p < 0.05) and earlier timings in comparison with major literary sources, underscoring the requisite of updated standards for age estimation of modern individuals.

Occipital Condyle Osteoid Osteoma with Severe Occipital Pain that Disappeared after Surgical Resection

Osteoid osteoma is a benign bone tumor characterized by local pain that typically increases at night. The tumor commonly occurs in the long bones of the lower extremities, and in rare instances in cranial bones. Here we report the case of a 25-year-old man diagnosed with an osteoid osteoma of the right occipital condyle. The patient suffered from severe occipital pain in the 3 years leading up to surgery, and the pain disappeared after surgical resection of the tumor. Due caution must be taken to avoid vertebral artery injury in the surgical approach in this region. An intraoperative navigation guidance system and preoperative analysis using three-dimensional reconstructed computed tomography (CT) images improved the accuracy and safety of the resection. The typical pain in osteoid osteoma is presumed to be associated with prostaglandin E2 secretion. Plasma prostaglandin E2 of this patient was elevated preoperatively and normalized after the operation. This is the first report describing an elevation of plasma prostaglandin E2 before surgical resection followed by a normalization of serum prostaglandin E2 after surgical resection.

Mapping occipital bone thickness using computed tomography for safe screw placement

OBJECT Safe and effective insertion of occipital bone screws requires morphological analysis of the occipital bone, which is poorly documented in the literature. The authors of this study present morphological data for determining the area of screw placement for optimal internal fixation. METHODS The subjects of this institutional review board-approved retrospective study were 105 individuals without head and neck disease who underwent CT imaging at the authors' hospital. There were 55 males and 50 females, with a mean age of 57.1 years (range 20-91 years). Measurements using CT were taken according to a matrix of 55 points following a grid with 1-cm spacing based on the external occipital protuberance (EOP). RESULTS The maximum thickness of the occipital bone was at the level of the EOP at 16.4 mm. Areas with thicknesses > 8 mm were more frequent at the EOP and up to 2 cm in all directions, as well as up to 1 cm in all directions at a height of 1 cm inferiorly, and up to 3 cm from the EOP inferiorly. The male group tended to have a thicker occipital bone than the female group, and the differences were significant around the EOP. The ratio of the trabecular bone to the occipital bone thickness was > 30% in the central region. At positions more than 2 cm laterally, the ratio was < 15%, and the ratio gradually decreased further laterally. CONCLUSIONS Screws that are 8 mm long can be placed in the area extending 2 cm laterally from the EOP at the level of the superior nuchal line and approximately 3 cm inferior to the center. These results suggest that it may be possible to effectively insert a screw over a wider area than the conventional reference range.

A computed tomography morphometric study of occipital bone and C2 pedicle anatomy for occipital-cervical fusion

Background:

Occipital-cervical fusion (OCF) has been used to treat instability of the occipito-cervical junction and to provide biomechanical stability after decompressive surgery. The specific areas that require detailed morphologic knowledge to prevent technical failures are the thickness of the occipital bone and diameter of the C2 pedicle, as the occipital midline bone and the C2 pedicle have structurally the strongest bone to provide the biomechanical purchase for cranio-cervical instrumentation. The aim of this study was to perform a quantitative morphometric analysis using computed tomography (CT) to determine the variability of the occipital bone thickness and C2 pedicle thickness to optimize screw placement for OCF in a South East Asian population.

Methods:

Thirty patients undergoing cranio-cervical junction instrumentation during the period 2008-2010 were included. The thickness of the occipital bone and the length and diameter of the C2 pedicle were measured based on CT.

Results:

The thickest point on the occipital bone was in the midline with a maximum thickness below the external occipital protuberance of 16.2 mm (±3.0 mm), which was thicker than in the Western population. The average C2 pedicle diameter was 5.3 mm (±2.0 mm). This was smaller than Western population pedicle diameters. The average length of the both pedicles to the midpoint of the C2 vertebral body was 23.5 mm (±3.3 mm on the left and ±2.3 mm on the right).

Conclusions:

The results of this first study in the South East Asian population should help guide and improve the safety in occipito-cervical region instrumentation. Thus reducing the risk of technical failures and neuro-vascular injury.

Giant cell tumor of the occipital bone: A case report and review of the literature

Giant cell tumors (GCTs) are usually found in the epiphysis of the long bones, and represent ~5% of all bone tumors. Only <1% of GCTs are localized in the cranium. When localized in the cranium, GCTs are commonly observed in the sphenoid or temporal bones, and rarely in the parietal or frontal bones. Occipital bone posterior fossa involvement is an extremely rare occurrence. The current study presents a 22-year-old female patient was admitted to the Department of Radiation Oncology (Karadeniz Technical University, Faculty of Medicine, Trabzon, Turkey) with complaints of neck pain and headache. The patients cranial magnetic resonance images showed a 2.5 6-cm mass in the occipital bone, which was subtotally excised. The patient was treated with radiotherapy following the surgery. At present, the patient has shown no progression after 20 months of follow-up.

Ardipithecus ramidus and the evolution of the human cranial base

The early Pliocene African hominoid Ardipithecus ramidus was diagnosed as a having a unique phylogenetic relationship with the Australopithecus + Homo clade based on nonhoning canine teeth, a foreshortened cranial base, and postcranial characters related to facultative bipedality. However, pedal and pelvic traits indicating substantial arboreality have raised arguments that this taxon may instead be an example of parallel evolution of human-like traits among apes around the time of the chimpanzee-human split. Here we investigated the basicranial morphology of Ar. ramidus for additional clues to its phylogenetic position with reference to African apes, humans, and Australopithecus. Besides a relatively anterior foramen magnum, humans differ from apes in the lateral shift of the carotid foramina, mediolateral abbreviation of the lateral tympanic, and a shortened, trapezoidal basioccipital element. These traits reflect a relative broadening of the central basicranium, a derived condition associated with changes in tympanic shape and the extent of its contact with the petrous. Ar. ramidus shares with Australopithecus each of these human-like modifications. We used the preserved morphology of ARA-VP 1/500 to estimate the missing basicranial length, drawing on consistent proportional relationships in apes and humans. Ar. ramidus is confirmed to have a relatively short basicranium, as in Australopithecus and Homo. Reorganization of the central cranial base is among the earliest morphological markers of the Ardipithecus + Australopithecus + Homo clade.

Xanthoma of the occipital bone and with preserved inner and outer bone cortex: case report

Objective We present a unique case of a midline xanthoma of the occipital bone exhibiting atypical imaging characteristics with preserved bone cortex that has not previously been described.

Participant This man presented with refractory headaches and suboccipital pain and a mass within the diploe of the occipital bone but with preserved inner and outer cortex of the bone. Magnetic resonance imaging showed a midline, enhancing, and marrow-replacing process in the occipital bone measuring 1.5 cm in anteroposterior (AP) diameter, resulting in mild indentation of the dorsal aspect of the cerebellar vermis.

Results The patient underwent a suboccipital craniectomy. Tumor resection was from the foramen magnum to the inion and laterally until normal bone was encountered. The xanthoma was yellowish and bled a moderate amount upon resection.

Conclusion An isolated cranial xanthoma with preserved inner and outer bone cortex involving the occipital bone and of midline location has yet to be described. The differential diagnosis of osteoexpansile skull lesion with preserved bone cortex should now include xanthoma. Given the broad spectrum of imaging characteristics exhibited by this unusual diagnosis, surgical intervention is indicated from a diagnostic as well as a therapeutic standpoint.

Malignant hemangioendothelioma of occipital bone

Epithelioidhemangioendothelioma is a rare vascular tumor of bone, and rarely these lesions can present as unique and extremely aggressive tumor. We report a case of highly aggressive epithelioidhemangioendothelioma and discuss the imaging findings. CT brain plain study revealed a poorly-defined, mixed density expansile and lytic lesion involving the occipital bone with extension to the left side with poorly defined trabecula formation. There was significant but irregular enhancement after intravenous administration of contrast material and also marked bone destruction. Microscopic examination of the fine needle aspiration cytology showed a tumor composed of vascular channels lined by plump endothelial cells, which had enlarged hyperchromatic nuclei. In view of the extensive infiltration the patient was submitted for the radiotherapy.