Rethinking the Origin of the Primary Respiratory Mechanism

Spheno-occipital synchondrosis (SOS) is the joint regarded as the most important foundation for understanding cranial osteopathy and craniosacral therapy. SOS is the origin of the primary respiratory mechanism (PRM), a movement between the posterior surface of the body of the sphenoid bone and the anterior surface of the base of the occipital bone. From the PRM perspective, an alteration of the position between the two bone surfaces would create cranial and/or craniosacral dysfunction. These positional alterations of the SOS (in adults and children) would determine specific and schematical movements of the bones of the entire skull, whose movements are recognizable by palpation by trained operators. PRM expression is influenced by other elements, such as movement of the cranial bones, inherent movement of the central nervous system, cyclic movement of cerebrospinal fluid (CSF), mechanical tension of the cranial meninges, and passive movement of the sacral bone between the iliac bones. The article reviews the most up-to-date information on the evolution of cranial sutures/joints and meninges in adulthood, the fluctuations of the CSF, brain, and spinal mass movements. Research should reconsider the motivations that induce the operator to discriminate the palpable cranial rhythmic impulse, and probably, to rethink new cranial dysfunctional patterns.

When does the spheno-occipital synchondrosis close?

In forensic work, the spheno-occipital synchondrosis helps identify the deceased as a child or young adult. In the past, it was generally held that the synchondrosis closed between the late teens and 25 years, but recent studies have suggested closure in adolescence. There are also suggestions that the age at closure recorded might be influenced by ancestry and the technique used to study the joint. This comprehensive review of the literature of the past 60 years concludes that the age of closure of the spheno-occipital synchondrosis is very variable, from childhood to the mid-twenties, with no obvious association with the geographical location of the study population. We note that some studies on bony specimens indicated later closure than others using clinical images and draw attention to a possible misinterpretation of the so-called "fusion scar" which might explain this incongruity. Despite an increasing acceptance that the synchondrosis usually closes in adolescence, we are concerned that insufficient heed is being paid to reports of closure in childhood and in the early to mid-twenties. We conclude that, for forensic purposes, it is unwise to declare that the synchondrosis closes in adolescence. It would be safer to state that a closed synchondrosis indicates a person 6 years or over and that an open synchondrosis may be seen up to the mid-twenties. Clearly, for younger individuals, the dentition and, for all individuals in this age range, documentation of unfused postcranial epiphyses would be important in attempting to narrow this very broad estimation of age.

New Insights Into Cranial Synchondrosis Development: A Mini Review

The synchondroses formed via endochondral ossification in the cranial base are an important growth center for the neurocranium. Abnormalities in the synchondroses affect cranial base elongation and the development of adjacent regions, including the craniofacial bones. In the central region of the cranial base, there are two synchondroses present—the intersphenoid synchondrosis and the spheno-occipital synchondrosis. These synchondroses consist of mirror image bipolar growth plates. The cross-talk of several signaling pathways, including the parathyroid hormone-like hormone (PTHLH)/parathyroid hormone-related protein (PTHrP), Indian hedgehog (Ihh), Wnt/β-catenin, and fibroblast growth factor (FGF) pathways, as well as regulation by cilium assembly and the transcription factors encoded by the RUNX2, SIX1, SIX2, SIX4, and TBX1 genes, play critical roles in synchondrosis development. Deletions or activation of these gene products in mice causes the abnormal ossification of cranial synchondrosis and skeletal elements. Gene disruption leads to both similar and markedly different abnormalities in the development of intersphenoid synchondrosis and spheno-occipital synchondrosis, as well as in the phenotypes of synchondroses and skeletal bones. This paper reviews the development of cranial synchondroses, along with its regulation by the signaling pathways and transcription factors, highlighting the differences between intersphenoid synchondrosis and spheno-occipital synchondrosis.

Craniofacial anomalies associated with spondyloenchondrodysplasia: Two case reports

RATIONALE

Spondyloenchondrodysplasia (SPENCD) is an autosomal recessive skeletal dysplasia by biallelic mutations in ACP5 gene encoding tartrate-resistant acid phosphatase (TRAP). The extra-osseous phenotype of SPENCD is pleiotropic and involves neurological impairment and immune dysfunction. Dentofacial abnormalities and orofacial symptoms in SPENCD patients have been little discussed in the literature.

PATIENTS CONCERNS

Herein we present clinical and radiological data regarding 2 siblings with SPENCD. Both patients exhibited short stature, cervical platyspondyly, growth disturbance with multiple skeletal deformities of the wrist, and systemic lupus erythematosus related autoimmunity. They experienced prolonged pain in the temporomandibular joint (TMJ) area and exhibited delayed dental development. One patient presented with midface hypoplasia, retrognathic mandible, and anterior openbite. Computed tomographic images demonstrated delayed spheno-occipital synchondrosis, obtuse cranial base angle, overdeveloped and anteriorly displaced sphenoidal sinuses, and compressed ethmoidal sinuses.

DIAGNOSIS

The genetic analysis revealed heterozygous for a missense mutations at ACP5 in both probands.

INTERVENTIONS

Routine follow-up with conservative treatment were conducted for 12 months.

OUTCOMES

The elder sister's orofacial pain was relieved but the boy showed sustained masticatory and cervical muscle pain and TMJ arthralgia which had changed in accordance with systemic condition. No further teeth eruption or skeletal growth was observed in 2 siblings during the follow-up period.

LESSONS

These findings extend the phenotypic spectrum of SPENCD and indicate that compromised endochondral ossification and the loss of TRAP activity may affect altered dentofacial development and orofacial symptoms.

Traumatic Basilar Artery Entrapment without Longitudinal Clivus Fracture: A Case Report and Review of the Literature

In blunt cerebrovascular injury, reported traumatic basilar artery occlusions have involved dissection of the basilar artery, distal embolization due to traumatic vertebral artery dissection, or entrapment of the basilar artery into the clivus fracture. To date, however, there are no reports of traumatic basilar artery entrapment without a clivus fracture. Here, we report the first case of traumatic basilar artery occlusion caused by entrapment into an originally existing bone defect. A 67-year-old man with a history of treatment for intracranial aneurysm suffered multiple traumatic injuries in a fall. On arrival at our hospital, he presented with neurogenic shock with quadriplegia. Computed tomography (CT) showed small epidural hematoma, C4-6 cervical spinous process fracture, and Th2-3 vertebral body fracture. CT angiography revealed occlusion of the basilar artery trunk. As vertebrobasilar artery dissections and clivus fracture were not observed; however, we could not elucidate the pathology of the basilar artery occlusion. On day 4, after surgery for the cervical and thoracic lesions, he exhibited consciousness disturbance. Diffusion-weighted imaging on day 5 showed hyperintensities in the brainstem and cerebellum. Basi-parallel anatomic scanning magnetic resonance imaging showed that the basilar artery, while lacking vascular wall injuries, was tethered into the clivus. Antithrombotic therapy was performed, but the patient progressed to a locked-in state. Previous head CT before the trauma revealed a bone defect already present in the clivus. We speculated basilar artery entrapment into this preexisting bone defect. We must look for basilar artery injury in trauma patients even in the absence of clivus fracture.

Evaluation of spheno-occipital synchondrosis: A review of literature and considerations from forensic anthropologic point of view

Cranial sutures and synchondrosis have long been studied by forensic scientists, human anatomists, and anthropologists for estimation of age in different population groups. Observation of the closure of spheno-occipital synchondrosis has an important role to play in the estimation of age in the examination of unknown human remains when a skull is brought for examination. The present article reviews the studies conducted on the closure of spheno-occipital synchondrosis and presents a few valuable considerations that would be essential for carrying out research related to closure of spheno-occipital synchondrosis in humans.