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Purpose The spheno-occipital synchondrosis (SOS) is an important site of endochondral ossification in the cranial base that closes prematurely in Apert, Crouzon, and Pfeiffer syndromes, which contributes to varying degrees of midface hypoplasia. The facial dysmorphology of Muenke syndrome, in contrast, is less severe with low rates of midface hypoplasia. We thus evaluated the timing of SOS fusion and cephalometric landmarks in patients with Muenke syndrome compared to normal controls. Methods Patients with Muenke syndrome who had at least one fine-cut head computed tomography scan performed from 2000 to 2020 were retrospectively reviewed. A case–control study was performed of patient scans and age- and sex-matched control scans. SOS fusion status was evaluated as open, partially closed, or closed. Results We included 28 patients and compared 77 patient scans with 77 control scans. Kaplan–Meier analysis demonstrated an insignificantly earlier timeline of SOS fusion in Muenke syndrome ( p  = 0.300). Mean sella-orbitale (SO) distance was shorter (44.0 ± 6.6 vs. 47.7 ± 6.7 mm, p  < 0.001) and mean sella-nasion-Frankfort horizontal (SN-FH) angle was greater (12.1° ± 3.8° vs. 10.1° ± 3.2°, p  < 0.001) in the Muenke group, whereas mean sella-nasion-A point (SNA) angle was similar and normal (81.1° ± 5.7° vs. 81.4° ± 4.7°, p  = 0.762). Conclusion Muenke syndrome is characterized by mild and often absent midfacial hypoplasia, with the exception of slight retropositioning of the infraorbital rim. Interestingly, SOS fusion patterns in these patients are not significantly different from age- and sex-matched controls despite an increased odds of fusion. It is possible that differences in timing of SOS fusion may manifest phenotypically at the infraorbital rim rather than at the maxilla.

Abstract BACKGROUND Basilar invagination is a developmental anomaly of the craniovertebral junction in which the odontoid abnormally prolapses into the foramen magnum. It is often associated with other osseous anomalies of the craniovertebral junction, including atlanto-occipital assimilation, incomplete ring of C1, and hypoplasia of the basiocciput, occipital condyles, and atlas. Basilar invagination is also associated with neural axis abnormalities, including Chiari malformation, syringomyelia, syringobulbia, and hydrocephalus. Patients frequently present with neurologic symptoms and deficits and warrant surgical treatment to prevent progression. OBJECTIVE To review the management of basilar invagination. METHODS The literature was reviewed in reference to the evaluation and management of basilar invagination, with particular emphasis on the surgical treatment. RESULTS Reducible basilar invagination may be treated with posterior decompression and stabilization. Ventral decompression may be necessary for basilar invagination with neural compression that is not reducible with axial cervical traction. Posterior cervical stabilization is necessary after ventral decompression. Modern rod and screw systems combined with autogenous bone graft enable correction of deformity, immediate stabilization, and high fusion rates. CONCLUSION Basilar invagination is a developmental anomaly and commonly presents with neurologic findings. Treatment is typically surgical and involves anterior decompression followed by posterior stabilization for irreducible invagination and posterior decompression and stabilization for reducible invagination.

PurposeTo describe a case of an anomalous posterosuperior course of the V3 segment of the right vertebral artery (VA) that penetrated the occipital bone (wall of the jugular foramen).MethodsA 33-year-old healthy woman underwent cranial magnetic resonance (MR) imaging and MR angiography from the upper cervical to the intracranial region using a 3-Tesla scanner to screen for asymptomatic brain lesions, including cerebrovascular diseases.ResultsMR angiography showed no pathological arterial lesions such as aneurysms; however, there was an anomalous posterosuperior course of the V3 segment of the right VA. On MR angiographic source images and coronal reformatted images, the right VA was observed to penetrate the occipital bone lateral to the right hypoglossal canal and is located on the inferoposteromedial wall of the right jugular foramen and enter the posterior fossa at a higher level than the foramen magnum.ConclusionWe present a case in which the right VA showed an anomalous posterosuperior course at the craniovertebral junction. It is extremely rare for a VA to take a higher course. To our knowledge, this is the first report of such a VA variation in the relevant English-language literature. We speculated that the right VA of our patient was formed by the persistence of one more cephalad primitive artery than the first intersegmental artery, not by the persistence of the primitive hypoglossal artery. Careful observation of MR angiographic source is useful and important for identifying the VA penetrating the occipital bone.

Morphological changes in the child skull due to mechanical and metabolic stimulation and synostosis of the suture are well known. On the other hand, few studies have focused on clinical conditions relevant for adult skull deformity. We retrospectively reviewed computed tomography (CT) findings obtained from 365 cases that were treated for head injuries, moyamoya disease, cervical internal carotid artery stenosis, and mental diseases, and investigated the morphological changes in the skull associated with these diseases. The findings from head injuries were used not only for control subjects, but also for the analysis of generational changes in skull shape based on birth year. Head shape had a brachiocephalic tendency with occipital flattening in people born from the 1950s onwards. Cases of moyamoya disease, cervical internal carotid artery stenosis, and mental diseases showed significantly thicker frontal and occipital bone than those of control subjects. The skull thickening was especially noticeable in the frontal bone in moyamoya disease. Plagiocephaly was significantly frequent in moyamoya disease. These uncommon skull shapes are useful CT findings in screening subjects for early evidence of mental diseases and intracranial ischemic diseases with arterial stenosis.

PurposeThe topic of osseous variations of the craniocervical junction is a complex morphological and embryological chapter of human anatomy, with a possible impact on neurogical and vascular functionality in this morphological variable region.Material & methodsAn until now undescribed anatomical variation of the exoccipital part of the occipital bone has been observed after maceration at the outer skull base of a West-European 68-year-old male body donor.ResultsOn both sites of the foramen magnum accessory osseous processes were observed that arise from the jugular process and point towards the lateral margin of the foramen magnum. On the left site this process forms a full arc that bridges the condylar fossa completely.ConclusionThe observed osseous bridge over the condylar fossa has not been reported on before and can be explained by the partial persistence of a primordial vertebra between atlas and occipital bone: the Proatlas. The resulting accessory structure may affect due to its topographic conditions the V3-Segment of the vertebral artery and its accompanying nerves, and thus, play a role in diagnosis and therapy of vascular and/or neurological symptoms of head and neck.

Background The pathogenesis of Chiari malformations is incompletely understood. We tested the hypothesis that different etiologies have different mechanisms of cerebellar tonsil herniation (CTH), as revealed by posterior cranial fossa (PCF) morphology. Methods In 741 patients with Chiari malformation type I (CM-I) and 11 patients with Chiari malformation type II (CM-II), the size of the occipital enchondrium and volume of the PCF (PCFV) were measured on reconstructed 2D-CT and MR images of the skull. Measurements were compared with those in 80 age- and sex-matched healthy control individuals, and the results were correlated with clinical findings. Results Significant reductions of PCF size and volume were present in 388 patients with classical CM-I, 11 patients with CM-II, and five patients with CM-I and craniosynostosis. Occipital bone size and PCFV were normal in 225 patients with CM-I and occipitoatlantoaxial joint instability, 55 patients with CM-I and tethered cord syndrome (TCS), 30 patients with CM-I and intracranial mass lesions, and 28 patients with CM-I and lumboperitoneal shunts. Ten patients had miscellaneous etiologies. The size and area of the foramen magnum were significantly smaller in patients with classical CM-I and CM-I occurring with craniosynostosis and significantly larger in patients with CM-II and CM-I occurring with TCS. Conclusions Important clues concerning the pathogenesis of CTH were provided by morphometric measurements of the PCF. When these assessments were correlated with etiological factors, the following causal mechanisms were suggested: (1) cranial constriction; (2) cranial settling; (3) spinal cord tethering; (4) intracranial hypertension; and (5) intraspinal hypotension.

The paracondylar process is a rare osseous process arising at the cervicooccipital region that belongs to a large and heterogenic group of developmental abnormalities of the craniovertebral junction. We present a rare case of a paracondylar process in an 11-year-old girl, in which the diagnosis was made with the use of MRI, thereby skipping X-ray and CT scan, thus avoiding exposure of the young patient to radiation. To our knowledge, the use of MRI has not previously been reported in the investigation and diagnosis of such an abnormality. We describe the details of this variation emphasizing on awareness of this process, its anatomic relationships and its problems to clinicians, radiologists, surgeons and chiropractors.

Occipital spur is an abnormal bony outgrowth of the external occipital protuberance (EOP). We describe an interesting and previously unreported case of fracture of an occipital spur following trauma. Our 20-year-old male patient was treated in the emergency department (ED) and discharged home without complication. Neurosurgical consultation was obtained but is not requisite for these injuries. Greater awareness of this unique presentation may help to expedite future emergency department treatment.

Objective We defined parameters that could differentiate between positional and synostotic plagiocephaly and defined a diagnostic chart for decision making. Design Prospective study. Setting We examined 411 children with non-syndromic skull abnormalities between January 2011 and December 2012. Participants A total of 8 infants under 1 year of age with proven unilateral non-syndromic lambdoid synostosis (LS) and 261 children with positional deformity were examined to outline the specific clinical features of both diagnoses. After clinical examination, an ultrasound revealed either a closed suture suggestive of LS or a patent lambdoid suture suggestive of positional deformity. For patients with synostosis, plain radiographs, MR imaging and follow-up examinations were performed. In cases of open sutures, only follow-ups were completed. Main outcome measure Clinical, imaging, genesis and treatment differences between positional plagiocephaly and LS. Results In all 8 cases of unilateral LS and 258 cases of positional plagiocephaly, the diagnosis was established by clinical examination alone. In three cases of positional plagiocephaly, diagnosis was determined after an additional ultrasonography. MR imaging revealed a unilateral tonsillar herniation in five of the eight children with LS and hydrocephalus in one child. Conclusions We have suggested a list of clinical features that specify the underlying cause of posterior plagiocephaly. An additional ultrasound scanning confirmed the diagnosis without any risks of ionising radiation or sedation as in a CT scan.