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Concept: Squama occipitalis

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Recently we reported the development of prominent exostosis young adults' skulls (41%; 10-31 mm) emanating from the external occipital protuberance (EOP). These findings contrast existing reports that large enthesophytes are not seen in young adults. Here we show that a combination sex, the degree of forward head protraction (FHP) and age predicted the presence of enlarged EOP (EEOP) (n = 1200, age 18-86). While being a male and increased FHP had a positive effect on prominent exostosis, paradoxically, increase in age was linked to a decrease in enthesophyte size. Our latter findings provide a conundrum, as the frequency and severity of degenerative skeletal features in humans are associated typically with aging. Our findings and the literature provide evidence that mechanical load plays a vital role in the development and maintenance of the enthesis (insertion) and draws a direct link between aberrant loading of the enthesis and related pathologies. We hypothesize EEOP may be linked to sustained aberrant postures associated with the emergence and extensive use of hand-held contemporary technologies, such as smartphones and tablets. Our findings raise a concern about the future musculoskeletal health of the young adult population and reinforce the need for prevention intervention through posture improvement education.

Concepts: Biology, Prediction, Future, Occipital bone, Bones of the head and neck, Inion, Squama occipitalis, External occipital protuberance

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The Ceprano calvarium was discovered in fragments on March 1994 near the town of Ceprano in southern Latium (Italy), embedded in Middle Pleistocene layers. After reconstruction, its morphological features suggests that the specimen belongs to an archaic variant of H. heidelbergensis, representing a proxy for the last common ancestor of the diverging clades that respectively led to H. neanderthalensis and H. sapiens. Unfortunately, the calvarium was taphonomically damaged. The postero-lateral vault, in particular, appears deformed and this postmortem damage may have influenced previous interpretations. Specifically, there is a depression on the fragmented left parietal, while the right cranial wall is warped and angulated. This deformation affected the shape of the occipital squama, producing an inclination of the transverse occipital torus. In this paper, after X-ray microtomography (μCT) of both the calvarium and several additional fragments, we analyze consistency and pattern of the taphonomic deformation that affected the specimen, before the computer-assisted retrodeformation has been performed; this has also provided the opportunity to reappraise early attempts at restoration. As a result, we offer a revised interpretation for the Ceprano calvarium’s original shape, now free from the previous uncertainties, along with insight for its complex depositional and taphonomic history.

Concepts: Human, Common descent, Neanderthal, Occipital bone, Human evolution, Pleistocene, Homo erectus, Squama occipitalis

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The pathology in congenital atlantoaxial instability is usually in C1-2 joints. Addressing the joints appears to be the most rationale approach. The joints are usually approached posteriorly, manipulated, and fused. Understanding the normal and abnormal anatomy is important. Normally, the third segment of the vertebral artery courses lateral to the C1-2 joint. However, in about 20% of the cases with complex congenital craniovertberal junction anomalies the artery crosses the joint posteriorly. The artery in such cases may be injured while joint manipulation and instrumentation with disastrous consequences. Alternatively, occipital squama can be fused to the cervical spine. However, this requires fusion of multiple segments affecting the neck movements significantly. An anomalous vertebral artery can be dissected, mobilized, and safeguarded while dissecting, manipulating, and fusing the C1-2 joint. In this operative video, authors have highlighted the technique to safeguard the anomalous vertebral artery during joint manipulation. Proper informed consent was obtained from the patient.

Concepts: Informed consent, Vertebral column, Anatomy, Normal distribution, Galen, Cervical vertebrae, Occipital bone, Squama occipitalis

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Incidental findings on brain MRI may constitute a diagnostic pitfall. We observed an incidental extra-axial midline rounded pseudomass between the torcular Herophili and the occipital squama, with spontaneous resolution, which we called “torcular pseudomass.”

Concepts: Atom, Magnetic resonance imaging, Occipital bone, Bones of the head and neck, Squama occipitalis, Squama

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Mandibuloacral dysplasia with type B lipodystrophy is a rare autosomal recessive disease characterized by atrophic skin, lipodystrophy, and skeletal features. It is caused by mutations in ZMPSTE24, a gene encoding a zinc metalloproteinase involved in the post-translational modification of lamin. Nine distinct pathogenic variants have been identified in 11 patients from nine unrelated families with this disorder. We report a 12-year-old boy with mandibuloacral dysplasia with type B lipodystrophy and a novel homozygous c.1196A>G; p.(Tyr399Cys) mutation in ZMPSTE24. The patient had typical dermatological and skeletal features of mandibuloacral dysplasia with type B lipodystrophy, sparse hair, short stature, mild microcephaly, facial dysmorphism, and a striking failure of ossification of the interparietal region of the occipital bone, up to the position where transverse occipital suture can be observed. Newly recognized signs for mandibuloacral dysplasia with type B lipodystrophy were gaze palsy and ptosis. Delayed closure of cranial sutures and Wormian bones have been described in three patients, but an ossification failure strictly limited to the occipital bone, as seen in the present patient, appears to be unique for mandibuloacral dysplasia with type B lipodystrophy. This observation illustrates that ZMPSTE24 could play a specific role in membranous ossification in the interparietal part of the squama (Inca bone) but not in the intracartilaginous ossification of the supraoccipital. This failure of ossification in the squama appears to be a useful feature for the radiological diagnosis of mandibuloacral dysplasia with type B lipodystrophy. © 2016 Wiley Periodicals, Inc.

Concepts: Bone, Patient, Skeletal system, Skull, Zygosity, Intramembranous ossification, Occipital bone, Squama occipitalis

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Occipito-cervical(OC) fusion is often practiced for congenital atlanto-axial dislocation (CAAD) and basilar invagination (BI) with claims of good long term outcome. Little has been discussed about the delayed complications following fusing occipital squama to cervical spine (OC fusion). We have described and analyzed delayed complications with OC fusion in our patients that helps us understand the underlying dynamics and biomechanics.

Concepts: Lumbar vertebrae, Vertebral column, Cervical vertebrae, Thoracic vertebrae, Vertebral artery, Occipital bone, Bones of the head and neck, Squama occipitalis

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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.

Concepts: Male, Female, Sex, Ratio, Skull, Bones of the head and neck, Inion, Squama occipitalis

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OBJECTIVE Atlantooccipital fixation is an important technique in the treatment of upper cervical spine instability. Important considerations for implant devices are obtrusiveness and propagation of torque through the device caused by cervical rotation. The authors evaluated the feasibility of 3 regions of the occiput as sites for occipitocervical fixation by examining bone mineral density at these locations. METHODS Unembalmed occiputs of 9 male and 4 female cadavers were used (mean age at time of death was 61.6 years, range 36-68 years). Studies were undertaken using caliper measurements and dual-energy x-ray absorptiometry of the superior nuchal line (SNL), the external occipital protuberance (EOP), and the inferior nuchal line (INL). RESULTS Data indicate that the bone at the INL has a similar volumetric bone density as the bone at the SNL, despite having half the thickness. Also, the volumetric bone density increases laterally along the nuchal lines. CONCLUSIONS Most hardware fixation is centered on stabilization at the EOP and the SNL. On the basis of these radiological results, the INL shows promise as a potential alternative site for screw placement in occipitocervical fixation.

Concepts: Osteoporosis, Bone, Density, Dual energy X-ray absorptiometry, Trapezius muscle, Bones of the head and neck, Nuchal lines, Squama occipitalis

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Electroneurography (ENoG) is one of the most objective tests in grading the damage and prediction of prognosis in peripheral facial palsy (PFP). We aimed to determine temporal changes of ENoG recorded over occipitalis muscle in acute idiopathic PFP. Consecutive 21 patients with unilateral acute idiopathic PFP and age- and sex-matched 15 healthy volunteers were included in the study. Nasal and occipital ENoG values were recorded once in the control group and the same procedure was repeated daily between the second and eight days of the disorder in the PFP group. Occipital ENoG value began to increase on the third day while nasal ENoG value was still within the normal range (27.04 vs 7.69 %, p = 0.0001). In the fourth, fifth and sixth days, occipital ENoG value was significantly high compared to nasal ENoG value (p = 0.0001 for each day) whereas nasal and occipital ENoG values were very similar in the seventh and eighth days (p = 0.181 and p = 0.584, respectively). Our study presents further support for technical possibility of occipital ENoG which may reflect the degree of fiber degeneration earlier than the nasalis muscle in PFP.

Concepts: Medical terms, Snake scales, Bell's palsy, Posterior auricular nerve, Squama occipitalis

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Cranio-vertebral junction fixation is challenging due to the complex topographical anatomy and the presence of important anatomical structures. There are several limitations to the traditional occipital squama fixation methods. The purpose of this work is to assess the safety and feasibility of a new optimum trajectory of occipital condyle (OC) screws for occipitocervical fixation via a free-hand technique.

Concepts: Histology, Anatomy, Trajectory, Trajectory of a projectile, Occipital bone, Bones of the head and neck, Squama occipitalis, Squama