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Osteogenesis imperfecta (OI) is a hereditary bone fragility disorder that in most patients is caused by mutations affecting collagen type I. Their typical oral and craneofacial characteristics (Dentinogenesis imperfecta type I and class III malocclusion), involve the dentist in the multidisciplinary team that treat these patients. It is usual to perform lateral skull radiographs for the orthodontic diagnosis. In addition, this radiograph is useful to analyse the junctional area between skull base and spine, that could be damaged in OI. Pathology in the craneovertebral junction (CVJ) is a serious complication of OI with a prevalence ranging from rare to 37%. To diagnosis early skull base anomalies in these patients, previously the neurological symptoms have been appear, we make a simple cephalometric analysis of the CVJ. This method has four measurements and one angle. Once we calculate the values of the OI patient, we compare the result with the mean and the standard deviations of an age-appropriate average in healthy controls. If the patient has a result more than 2,5 SDs above the age appropriate average in healthy controls, we should to refer the patient to his/her pediatrician or neurologist. These doctors have to consider acquiring another diagnostic images to be used to determine cranial base measurements with more reliability. Thereby, dentists who treat these patients, must be aware of the normal radiological anatomy of the cervical spine on the lateral cephalogram., This work was supported by Grant No. AP123942013 from the Mutua Madrileña Foundation for Medical Research, Madrid, Depto. de Especialidades Clínicas Odontológicas, Fac. de Odontología, TRUE, pub

Context: Diffuse idiopathic skeletal hyperostosis (DISH) or Forestier's syndrome may reduce vertebral mobility, thus affecting the stability of adjacent vertebral segments and promoting spinal stenosis, vertebral dislocation, and unstable fracture secondary to low-energy trauma.Aims: This study aimed to contribute with a case series of three patients affected by DISH undergone surgery with occipitocervical fixation for craniovertebral junction (CVJ) instability since the poor literature about CVJ instability and surgery in patients affected by DISH.Settings and Design: This was a multicentric case series.Subjects and Methods: Literature about CVJ instability and surgery in patients affected by DISH is poor. Thus, we present a case series of three patients affected by DISH, who underwent surgery with occipitocervical fixation with different clinical and radiological patterns.Results: CVJ represents one of the most mobile joints of the spine and is at greater risk for instability. Moreover, instability itself may act as primum movens for several degenerative conditions such as cervical spondylosis, ossification of the posterior longitudinal ligament, and cervical deformities. On the contrary, DISH itself may worsen CVJ instability because of subaxial spine stiffness. In case of DISH, the rigid unit formed by several ossified vertebral bodies acts as a long lever arm, increasing the forces applied to the hypermobile CVJ and reducing the dynamic buffer capability of ossified spine. On the other hand, vertebral instability increases the odds of fractures. In such cases, CVJ posterior instrumentation and fusion is an effective and feasible surgical technique, aimed to restore vertebral stability and to halt the progression of spinal stenosis.Conclusions: Due to the altered dynamics cervical spine along with the possible comorbidities, treatment indication and surgery for patients affected by DISH must be tailored case by case.

Historically considered as a nobody's land, craniovertebral junction (CVJ) surgery or specialty recently gained high consideration as symbol of challenging surgery as well as selective top level qualifying surgery. The alliance between Neurosurgeons and Otorhinolaringologists has become stronger in the time. CVJ has unique anatomical bone and neurovascular structures architecture. It not only separates from the subaxial cervical spine but it also provides a special cranial flexion, extension, and axial rotation pattern. Stability is provided by a complex combination of osseous and ligamentous supports which allows a large degree of motion. The perfect knowledge of CVJ anatomy and physiology allows to better understand surgical procedures of the occiput, atlas and axis and the specific diseases that affect the region. Although many years passed since the beginning of this pioneering surgery, managing lesions situated in the anterior aspect of the CVJ still remains a challenging neurosurgical problem. Many studies are available in the literature so far aiming to examine the microsurgical anatomy of both the anterior and posterior extradural and intradural aspects of the CVJ as well as the differences in all the possible surgical exposures obtained by 360 degrees approach philosophy. Herein we provide a short but quite complete at glance tour across the personal experience and publications and the more recent literature available in order to highlight where this alliance between Neurosurgeon and Otorhinolaringologist is mandatory, strongly advisable or unnecessary.

BACKGROUND: We herein outline the experience matured in our equipped Cranio-Vertebral Junction Laboratory for anatomic dissection.METHODS: An extreme lateral approach (ELA) was performed on 4 fresh cadavers and submandibular approach was performed on 5. An endoscope and navigation-assisted far lateral approach (FLA) was performed in 5 injected specimens. In these specimens, a transoral approach was also performed, as well as a neuronavigation-assisted comparison between transoral and transnasal explorable distances.RESULTS: As calculated with neuronavigation, statistically significant differences both in the explored craniocaudal (P = 0.003) and lateral (P = 0.008) distances were observed between the transoral approach and endoscopic endonasal approach. In FLA, neuronavigation facilitated identification and partial removal of the occipital condyle; in one case, during endoscopic intradural exploration, tearing of the emerging roots of the 11th cranial nerve occurred. In ELA, the site where the accessory nerve pierces into the sternocleidomastoid muscle was found at a distance from the tip of the mastoid between 3 and 4 cm.CONCLUSIONS: During dissections, as in the clinical setting, endoscope and image guidance give the surgeon a constant orientation, increasing the accuracy and the safety of the approach. Nonetheless, the encumbrance of the endoscope could represent a limit in deep and narrow corridors as those running across the craniovertebral junction, especially in "oblique" FLA and ELA, in which the surgical target is often hidden by a delicate tangle of nerves and vessels. Its use appears more suitable and safer in "straight" approaches as transoral and transnasal in which there are no neurovascular structures interposed.

Background: The extreme lateral approach is a direct lateral approach which allows a good control of the entire length of the vertebral artery (VA), the jugular foramen, the lowest cranial nerves, and the jugular–sigmoid complex. Herein we try to exploit the variants of the approach and we identify indications, advantages, and disadvantages. Methods: All phases of the study were conducted at the Institute of Public Health Section of Legal Medicine and Insurance of the University. We performed the extreme lateral approach in four subjects, who died between 24 and 48 h before in non-traumatic circumstances (three men and one woman). Results: The great auricular nerve, the spinal accessory, the branches of the first ventral spinal nerves, the jugular vein, and the vertebral artery were identified in all the cadavers. In all cases the right VA exited from the transverse foramen of C1. The site of SCM piercing the accessory nerve was at a distance from the tip of the mastoid between 3 and 4 cm (3.3 in one case, 3.4 in 2 cases, and 3.7 in one case). No vessels and nerves have been damaged after being identified and isolated. Conclusions: Extradural lesions at the ventro-lateral aspect of the CVJ may require an extreme lateral approach, a procedure more aggressive comparing with far lateral approach, which represents a reasonable option for large anterior and anterolateral lesions when greater exposure is required.

Background: The craniovertebral junction (CVJ) may be affected by several diseases. It is an anatomically complex region, involving the osteoligamentous, vascular, and nervous structures, which makes surgery challenging. In a case of ventral compression, an anterior approach is preferable, although posterior fixation is often required. Anterior transmucosal approaches are associated with high rates of complications. However, decompression and fixation by the use of retropharyngeal extramucosal approaches may be challenging. Objective: To investigate the feasibility of a single-stage, anterior, extramucosal submandibular (SM) approach modification to the CVJ for simultaneous decompression and stabilization. Materials and Methods: This was a preliminary cadaveric feasibility study on 2 injected specimens. A variation of the SM approach with a short “boomerang” incision, microsurgical decompression of the ventral CVJ, and a new hybrid construct for an anterior atlantoaxial stabilization was investigated. The surgical approach, the decompression, and the instrumentation technique have been described. In addition, intraprocedural images and radiographs and also postprocedural computed tomographic images were collected. Furthermore, surgical exposure, working corridors and angles, and decompression grade were measured. Results: The SM approach provided wide exposure of the ventral CVJ and the possibility for instrumentation and decompression by removing the anterior arch of C1 and the odontoid process. Conclusion: A single- stage anterior extramucosal SM approach for decompression and stabilization of the CVJ is feasible and could result in shorter surgical duration, avoiding the complications related to both the transmucosal approach and the prone position, although specific related risks exist. Mechanical investigation of this hybrid system and in vivo studies are needed to confirm our results.

Background: The endoscopic endonasal approach has recently been added to the surgical armamentarium to access the anterior craniovertebral junction (CVJ). Comparative analyses with the transoral approach are scarce. The aim of this study was to provide a quantitative anatomical analysis of both approaches. Methods: In four specimens the endoscopic endonasal approach (before and after sphenoidectomy) and the transoral approach (without and with a soft palate split) were performed. ApproachViewer—part of GTx-UHN (Guided Therapeutics software, developed at University Health Network, Toronto, ON, Canada)—was used to quantify and visualize the working volume, as well as the exposed area, of each surgical approach. Different modalities (crossing and non-crossing) were used to quantify the exposure of the deep surface, providing an indirect quantitative value of the ‘surgical freedom’. The lowest point exposed by the endonasal approaches was compared with that predicted by preoperative radiological lines. Non-parametric Welch analysis of variance (ANOVA) was used for statistical analyses. Results: The working volume was significantly larger and the distance to the target was shorter with the transoral approaches than with the endonasal approaches. Clival exposure was better with the endonasal approaches than with the non-crossing transoral approach without a soft palate split; areas below C1 were better exposed with the transoral routes. The nasoaxial line best predicted surgical exposure with the endonasal approaches. Conclusion: Endoscopic endonasal and transoral approaches to the anterior CVJ provide optimal exposure of different areas that overlap at the level of C1 when no anatomical anomalies are present. A split of the soft palate is not necessary during the transoral approach if it is combined with an endoscopic endonasal approach.

Background: We compiled a comprehensive literature review on the anatomic and clinical results of endoscopic approaches to the craniocervical junction (CVJ) to better contribute to identify the best strategy. Methods: An updated literature review was performed in the PubMed, OVID, and Google Scholar medical databases, using the terms “Craniovertebral junction,” “Transoral approach,” “Transnasal approach,” “Transcervical approach,” “Endoscopic endonasal approach,” “Endoscopic transoral approach,” “Endoscopic transcervical approach.” Clinical series, anatomic studies, and comparative studies were reviewed. Results: Pure endonasal and cervical endoscopic approaches still have some disadvantages, including the learning curve and the deeper surgical field. Endoscopically assisted transoral surgery with 30° endoscopes represents an emerging option to standard microsurgical techniques for transoral approaches to the anterior CVJ. This approach should be considered as complementary rather than an alternative to the traditional microsurgical transoral-transpharyngeal approach. Conclusions: The transoral approach with sparing of the soft palate still remains the gold standard compared with the pure transnasal and transcervical approaches because of the wider working channel provided by the former technique. The transnasal endoscopic approach alone appears to be superior when the CVJ lesion exceeds the upper limit of the inferior third of the clivus.

Objective For many years, the microsurgical transoral approach has been accepted as the gold standard for anterior decompressions of the craniovertebral junction (CVJ). The introduction of the endoscopic endonasal approach (EEA) has gained wide recognition and overwhelming support in recent years, including for diseases of the CVJ. The aim of this study was to critically analyze and discuss all cases of CVJ diseases approached by means of an EEA so far reported in the literature, including our institutional experience consisting of 6 consecutive patients. Methods Six consecutive patients affected by CVJ disease underwent an EEA. Three patients had a tumor (2 chordomas and 1 myeloma) and 3 had impressio basilaris. Results Five patients had an uncomplicated postoperative course and 1 developed an intraoperative cerebrospinal fluid leak and subsequent meningitis and died 5 weeks after surgery. A total of 107 patients (including our 6) affected by CVJ disease and treated with EEA have been reported so far. Among these patients, cerebrospinal fluid leak was reported in 13 (12.4%), transient velopharyngeal incompetence in 6 (5.6%), postoperative epistaxis in 2 (1.86%), and respiratory dysfunction requiring a tracheostomy in 2 (1.86%). In our extended institutional series of more than 20 consecutive anterior decompressions for CVJ diseases (including transoral and transnasal microsurgical approaches), the only fatal complication was associated with EEA. Conclusions On the basis of the reviewed literature and our personal experience, the reported increased safety of the EEA needs to be reassessed and discussed.

A variety of pathological conditions may affect the clivus and the craniovertebral junction (CVJ). These include congenital disorders, chronic inflammation, neoplasms, infections, and posttraumatic conditions that could all result in CVJ compression and myelopathy Endoscopic-assisted procedures have been further developed for CVJ decompression and they have now become conventional approaches. The aims of the present study were: (1) to compare “radiological” and “surgical” nasoaxial lines (NAxLs); (2) to introduce an analogous radiological line as a predictor of the superior extension of the transoral approach (palatine inferior dental arch line (PIA); (3) to compare the “radiological” nasopalatine line (NPL) with the “surgical” NPL (SNPL) and surgical PIA (SPIA); (4) to compare “our” SNPL with the NAxL; and (5) to find possible radiological reference points to predict, preoperatively, the maximal extent of superior dissection for the transoral approach (SPIA).

Uvod: Interesovanje za kraniocervikalni prelaz (engl. „the craniocervical junction“ – CCJ) započelo je disekcijama i izvanrednim crtežima Leonarda da Vinčija, a nastavljeno je ispitivanjima Andreasa Vezalijusa u 16. veku, kao i italijanskih anatoma i umetnika u 17. i 18. stoleću (Saunders, 1973; Persaud, 1984; Düring and Poggesi, 2006; Nathan, 2007). Veliki doprinos dali su Buržer u 19. veku i Pernkopf u 20. stoleću (Pernkopf, 1963; Bourgery i Jacob, 2005). Ipak, najdetaljnija istraživanja ovog područja obavljena su u poslednjih nekoliko decenija (Martin i sar., 2010; Steinmetz i sar., 2010; Lopez i sar., 2015). Kraniocervikalni prelaz obuhvata, u najužem smislu, donji deo okcipitalne kosti, atlas i aksis. Spomenuti autori proučili su ove osteološke komponente i izvršili odgovarajuća merenja, ali ne u potpunosti. Zato smo odlučili da CCJ ispitamo mnogo detaljnije u anatomskom i radiološkom domenu, kako bismo dali doprinos neurohirurškim intervencijama u ovom području. Ciljevi: 1) precizno utvrđivanje anatomskih odnosa osteoloških komponenti CCJa, uključujući i morfometrijska ispitivanja, kao i proučavanja obližnjih neuralnih struktura, naročito odnosa kičmene moždine, moždanog stabla i tonzila cerebeluma; 2) utvrđivanje odnosa spomenutih elemenata nakon maksimalne fleksije i ekstenzije, u poređenju sa neutralnim položaj glave i vrata; 3) utvrđivanje patoloških poremećaja i urođenih malformacija komponenti CCJa; 4) poboljšanje neurohirurških intervencija u predelu CCJ u svetlosti dobijenih podataka tokom naših istraživanja. Materijal i metode: Korišćene su, najpre, standardne anatomske metode na 22 uzorka okcipitalne kosti, 7 atlasa i 7 aksisa, uključujući precizna morfometrijska proučavanja. Druga grupa uzoraka obuhvatala je tri glave s mozgom prethodno fiksiranih u 10% formalinu. Nakon zamrzavanja na minus 250 C, svaka glava je serijski sečena u predelu CCJ u jednoj od tri glavne ravni: aksijalnoj, koronalnoj i sagitalnoj. Na ovim presecima ispitani su odnosi pojed, Objective: The interest in the craniocervical junction (the CCJ) started with dissections and brilliant drawings of Leonardo da Vinci, and it was continued by the examinations of Andreas Vesalius in the 16th century, and the Italian anatomists and artists in the 17th and 18th century (Saunders, 1973; Persaud, 1984; Düring and Poggesi, 2006; Nathan, 2007). A great contribution was given by Bourgery in the 19th century and Pernkopf in the 20th century (Pernkopf, 1963; Bourgery and Jacob, 2005). However, the most detailed study of this region was performed in the recent few decades (Martin et al., 2010; Steinmetz et al., 2010; Lopez et al., 2015). The craniocervical junction, in the narrower sense, comprises the lower part of the occipital bone, the atlas and the axis. The mentioned authors examined these osteological components and made certain measurements, although not fully. Therefore we decided to examine the CCJ in much more details and thus to give a contribution to the neurosurgical interventions in this region. Aims: 1) a precise determination of the anatomic relationships of the CCJ osteological components, including the morphometric examination, as well as a study of the adjacent neural structures, especially the relationships of the spinal cord, the brain stem and the cerebellar tonsils; 2) a determination of the relationships of the mentioned elements following a maximum flextion and extension, compared to the neutral position of the head and neck; 3) a determination of the pathological disorders and the congenital malformations of the CCJ components; 4) an improvement of the neurosurgical interventions in the CCJ region in the light of the data obtained in our study. Material and methods: First of all, some standard anatomic methods were applied in 22 occipital bones, 7 atlas and 7 axis specimens, including a precise morphometric examination. The second group of the specimens comprised three heads with a brain previously fixed in a 10% formaldehyde soluti

Case study description and analysis of a complex craniovertebral dysplasia in an 8-year-old male patient, in which conventional cervical spine radiographs demonstrated a regularly differentiated occipital base, as well as the presence of two lateral masses of the proatlas vertebra and two lateral masses of the atlas vertebra. Further assessment included computed tomography of the occipital base and the upper cervical spine as well as three-dimensional reconstruction. Malsegmentation of the fourth occipital vertebra can result in various anomalies that are known as 'manifestation of the proatlas'. The occurrence of a persistent proatlas with additional segmentation of the craniovertebral junction represents an extremely rare dysplasia. To our knowledge, it is the second report concerning the persistence of a complete human proatlas vertebra. We consider the biomechanical and embryological particularities of this complex dysplasia to represent sufficient basis for future differentiation from other malformations of the fourth occipital vertebra. Comprehensive literature review and discussion about the entity will be provided.