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Background: Nablus mask-like facial syndrome (NMFLS) is an extremely rare genetic syndrome characterized by facial dysmorphia as well as developmental delay. In the present report we describe a potential association between non-traumatic atlanto-occipital dislocation and NMFLS in an 11-year old female lacking typical facial features of NMFLS., Case Description: An 11-year-old female with autism presented with symptoms of persistent headache and vomiting as well as neck stiffness. Further investigation and CT imaging revealed congenital malformation of the skull base and craniocervical junction with complete posterior subluxation of the left occipital condyle. MRI findings later corroborated the findings on CT., Conclusions: The patient was successfully treated with occipitocervical fusion. The findings in this case suggest the possibility that atlanto-occipital instability and generalized occipitocervical may be associated with NMFLS., Competing Interests: Declaration of Competing interest report no conflicts of interest. The authors alone are responsible for the content and writing of the article., (Copyright © 2024 The Authors. Published by Elsevier Masson SAS.. All rights reserved.)

The craniovertebral junction not only contains anatomically important structures such as the medulla oblongata, upper cervical spinal cord, and vertebral artery, but also controls the dynamic movements of flexion, extension, and rotation of the head and neck. Consequently, instability and spinal deformities can easily occur in the craniovertebral region, and appropriate treatment should be selected based on the specificity of the lesion. Basilar invagination often involves bone and vascular anomalies and fusion surgery is often required. Therefore, careful pre-operative simulations are necessary. The creation and use of three-dimensional bone models, including image navigation, are useful for surgical simulation.

Background: Our previous study suggested that atlanto-occipital instability (AOI) is common in patients with type II basilar invagination (II-BI)., Objective: To further understand the pathogenesis of AOI in Chiari malformations (CM) and CM + II-BI through systematic measurements of the bone structure surrounding the craniocervical junction., Methods: Computed tomography data from 185 adults (80 controls, 63 CM, and 42 CM + II-BI) were collected, and geometric models were established for parameter measurement. Canonical correlation analysis was used to evaluate the morphological and positional relationships of the atlanto-occipital joint (AOJ)., Results: Among the 3 groups, the length and height of the condyle and superior portion of the lateral masses of the atlas (C1-LM) were smallest in CM + II-BI cases; the AOJ had the shallowest depth and the lowest curvature in the same group. AOJs were divided into 3 morphological types: type I, the typical ball-and-socket joint, mainly in the control group (100%); type II, the shallower joint, mainly in the CM group (92.9%); and type III, the abnormal flat-tilt joint, mainly in the CM + II-BI group (89.3%). Kinematic computed tomography revealed AOI in all III-AOJs (100%) and some II-AOJs (1.5%) but not in type I-AOJs (0%). Morphological parameters of the superior portion of C1-LM positively correlated with those of C0 and the clivus and significantly correlated with AOI., Conclusion: Dysplasia of the condyle and superior portion of C1-LM exists in both CM and II-BI cases yet is more obvious in type II-BI. Unstable movement caused by AOJ deformation is another pathogenic factor in patients with CM + II-BI., (Copyright © 2022 The Author(s). Published by Wolters Kluwer Health, Inc. on behalf of the Congress of Neurological Surgeons.)

Background: The posterior atlantooccipital membrane complex consists of the posterior atlantooccipital membrane and posterior atlantoaxial membrane. Posttraumatic, posterior atlantooccipital membrane complex injuries may have varied appearances on cervical magnetic resonance imaging. The purpose of this study was to identify the different types of posterior atlantooccipital membrane complex injuries that occur in trauma patients., Methods: Patients who suffered a posterior atlantooccipital membrane complex injury were identified retrospectively using key word searches of cervical magnetic resonance imaging reports between 2013 and 2020 using Nuance mPower software. All relevant imaging studies were reviewed by 2 neuroradiologists. A description of the location and type of posterior atlantooccipital membrane complex injury was recorded, along with additional osteoligamentous trauma of the craniocervical junction and relevant clinical history., Results: Forty-one patients were identified with acute posterior atlantooccipital membrane complex injury. Four distinct patterns of posterior atlantooccipital membrane complex injury were observed., Conclusions: A grading system for posterior atlantooccipital membrane complex injuries is proposed on the basis of these data: grade 1-edema confined to the posterior atlantooccipital and atlantoaxial membrane; grade 2-edema confined to the posterior atlantooccipital and atlantoaxial membrane and ligamentum nuchae; grade 3-stripping injury of the posterior atlantooccipital membrane with C1-C2 dorsal epidural hematoma; and grade 4-frank disruption of the posterior atlantooccipital membrane at C1 with edema in the remaining posterior atlantooccipital membrane complex., (Copyright © 2021 Elsevier Inc. All rights reserved.)

We describe a 2-year-old girl with bow hunter syndrome complicated by vertebral artery dissection and multiple ischemic infarcts. Pediatric bow hunter syndrome is a rare and likely under-recognized disorder. Interestingly, our patient had atlanto-occipital ligament calcification on CT scan, an imaging finding that has not been reported in association with bow hunter syndrome and one that might help increase recognition of this dynamic disorder of the posterior circulation.

Calcifying pseudoneoplasms of the neuroaxis (CAPNON) are rare, slow-growing, fibro-osseous lesions that can occur throughout the entire neuroaxis with few reported cases. We describe a case of craniocervical CAPNON that was treated by our unit and review the available literature. CAPNON are rare benign lesions occurring throughout the neuroaxis. Although rare, these lesions should be considered in cases of histopathological and radiology features of calcified lesions in both brain and spine. Despite a paucity of reports complete safe surgical resection should remain the goal to obtain the best clinical outcomes., (Copyright © 2019. Published by Elsevier Ltd.)

Background: Intraspinal degenerative cysts in the cervical region are rare disorders that may cause myelopathy or radiculopathy. Most of the intraspinal degenerative cysts reported are extradural cysts. This case report includes the neuroimaging, intraoperative, pathologic, and postoperative findings obtained in a patient with a degenerative intradural cyst at the craniovertebral (CV) junction., Case Description: We report a patient presenting with progressive spastic quadriparesis resulting from compressive myelopathy due to intradural degenerative cyst at the CV junction. Preoperative magnetic resonance imaging showed the intradural cyst at the cervicomedullary junction with degenerative changes causing myelopathy. We performed decompression of the CV junction, and histopathology of the cyst revealed degenerative cyst. Postoperatively the symptoms were relieved with no apparent complication. Intraspinal degenerative cysts causing compressive myelopathy are rare. To the best of our knowledge, this is the first case of intradural degenerative cyst at the CV junction., Conclusions: In this case report, we demonstrated the clinical, imaging, intraoperative, and pathologic features of a degenerative intraspinal cyst at the CV junction that was intradural in location. Compression of the spinal cord resulted in a gradually progressive myelopathy that showed remarkable improvement immediately after decompression by cystectomy., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Objective: The craniocervical junction permits a certain amount of mobility for the cervical spine. The biomechanical properties of occipital bone-atlas joint mainly depend on the bony structure, and atlas-axis joint biomechanical properties mainly depend on ligamentous structure. The underlying etiologic factor of Chiari malformation (CM) is debatable. Nowadays, some researchers argue that stabilization difference is one of the suspicious factors for etiopathogenesis. We aim to analyze the ligamentous morphometric differences of CM., Methods: Magnetic resonance images of 93 adult healthy subjects (n = 93) without any craniocervical junction development abnormalities and 25 (n = 25) adult patients with craniocervical junction development abnormalities (Arnold CM) were evaluated. Length, width, and length-width ratios of ligaments were evaluated., Results: Length of transverse ligament (mean: 23 ± 3.6 [range: 12.1-31.4]) in the normal population was significantly longer than transverse ligament length in CM patients (mean: 21.3 ± 2.5 [range: 17.2-24.9]). Length of alar ligament (mean: 10.7 ± 2 [range: 5.1-15.4]) in the normal population was significantly longer than alar ligament length in CM patients (mean: 8.8 ± 3.8 [range: 1.1-16.6]) (P = 0.007)., Conclusions: Craniocervical ligaments play an important role in maintaining stability and motion capacity of this region. This study promoted better understanding of craniocervical junction anomalies and provided data that facilitate performing more precise surgical treatment., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Background and Purpose: Although advances in imaging have allowed earlier and more accurate diagnosis of various fetal anomalies, Dandy-Walker malformation (DWM) remains one of the more challenging central nervous system anomalies to diagnose accurately before birth. Basilar invagination (BI), which is a dislocation of the dens in an upward direction, is occasionally accompanied by Klippel-Feil syndrome (KFS). We report a pediatric case of BI caused by atlanto-occipital subluxation (AOS) in KFS, suspected of having DWM prenatally but head magnetic resonance images (MRI) showed no evidence of that at 7 months of age., Case: At 28 weeks of gestation, fetal MRI study revealed a small cerebellar vermis, leading us to suspect a DWM. The patient was born at 40 weeks of gestation. Head CT showed inferior vermian hypoplasia without findings of hydrocephalus. Cervicothoracic CT showed cervical lamina assimilations, thoracic hemivertebrae, and cervicothoracic scoliosis. He was diagnosed with Dandy-Walker variant and KFS. At 7 months of age, head MRI showed near normal cerebellum and vermis and there was no evidence of the DWM. He did not have intellectual or developmental delay and imaging studies were performed periodically. At 9 years of age, an already existing cough headache deteriorated. Three-dimensional reconstructed images from CT scan showed C1 hypoplasia, fusion of C1 and C2, BI, and AOS. Sagittal T2-weighted MRI showed protrusion of cerebellar tonsils inferiorly to the level of the posterior arch of C2. Serum calcium, phosphate, and parathyroid hormone levels were normal. The diagnosis was tonsillar herniation related to BI following AOS in KFS. Posterior occipitocervical fixation was performed under traction., Conclusions: We found out two important clinical issues: DWM findings after birth can be disappearing and BI can present sequential deterioration because of AOS in KFS. Our observation indicated the possible prognosis of pediatric BI with long follow-up and can help us decide on its surgical treatment timing when associated with AOS.

Objective: Occipitalization of the atlas (OA) often is associated with atlantoaxial dislocation and basilar invagination. The purpose of this study is to determine the biomechanical difference between normal and OA conditions in the craniovertebral junction and to further explore the rationale for development of atlantoaxial dislocation and basilar invagination using the finite element model (FEM)., Methods: A ligamentous, nonlinear, sliding-contact, 3-dimensional FEM of the occipitoatlantoaxial complex was generated. Validation of the model was accomplished by comparing kinematic predictions with experimental data. We defined the atlantooccipital joint as a tie contact to simulate the OA deformity. The range of motion and the value of the maximum Von Mises stress were compared between the intact and OA models., Results: We found all of the predicted data in the intact FEM fell within 1 standard deviation of the cadaver data for all 6 loadings. The OA simulation significantly reduced the overall range of motion of the occipitoatlantoaxial complex at all loadings. The maximum Von Mises stress was predicted to increase at the transverse ligament and the superior articular facet of the axis for all the flexion, extension, lateral bending, and axial rotation loadings., Conclusions: The OA could result in hypermobility of the atlantoaxial segment and cause overstress in the transverse ligament and the lateral atlantoaxial joints. These changes explain the pathogenesis of atlantoaxial dislocation and basilar invagination associated with OA. Follow-up should be scheduled regularly due to the nature of the dynamic development of atlantoaxial dislocation and basilar invagination., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Background: Basilar invagination (BI) is a developmental anomaly and commonly presents with neurologic findings. The incidence of BI associated with other osseous anomalies of the craniovertebral junction is high, including incomplete ring of C1 with spreading of the lateral masses, atlanto-occipital assimilation, hypoplasia of the atlas, basiocciput hypoplasia, and occipital condylar hypoplasia. However, BI combined with C1 prolapsing into the foramen magnum (FM) is an extremely rare condition., Case Description: A previously healthy 6-year-old girl (case 1) presented with extremities numbness and left limb weakness over a period of 3 months. Radiograph and computed tomography (CT) scan demonstrated basilar invagination with C1 and dens upward into the FM and C2-3 congenital fusion. Magnetic resonance imaging (MRI) showed ventral brainstem and medulla compression, and the medulla-cervical angle was about 100°. The patient underwent transoral anterior decompression, reduction, and fusion by transoral atlantoaxial reduction plate surgery. The symptoms of extremities numbness and limb weakness were all alleviated after surgery. Postoperative MRI showed that the medulla-cervical angle improved from 100° to 143°. An 11-year-old boy (case 2) presented with a 2-month history of limbs numbness and weakness. CT scan and MRI demonstrated BI and compression of the spinal cord, with a craniospinal angle of only 63°. The 3-dimensional (3D) printed model showed that the anterior arch and lateral of C1 was 90° flipping and vertically upward prolapsing into the FM together with the dens, and the width of the atlas was greater than the maximum diameter of the FM, which resulted in structural incarceration. The patient received posterior occipitocervical fixation and fusion surgery with hyperextension skull traction. Postoperative CT scan revealed the craniospinal angle increased to 102°., Conclusions: We present 2 rare cases of BI combined with C1 prolapsing into the FM. We adopted different surgical strategies with satisfying outcome for these patients. We deem that the treatment of unique BI should be individualized according to the different image characteristics. The image-based modern rapid prototyping and 3D printed techniques can provide invaluable information in presurgical planning for complex craniovertebral junction anomalies., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Background: Isolated hypoglossal nerve palsy caused by an atlantooccipital synovial cyst is a rare lesion, with fewer than 5 cases reported in the literature., Case Description: Our patient presented with acute hypoglossal nerve dysfunction. Our differential included neoplasm, trauma, stroke, multiple sclerosis, or other inflammatory/infectious etiology. Imaging revealed a peripherally enhancing, extradural focus in the left premedullary cistern, most likely consistent with a synovial cyst., Conclusions: A left suboccipital craniectomy was performed in the region of the left hypoglossal canal, in which a cystic structure was noted at the occipital condyle and C1 vertebral junction. The nerve was adequately decompressed via aspiration of the cyst. Postoperatively, the patient substantially improved. Although rare, synovial cysts must be included in the differential diagnosis of atlantooccipital lesions., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Objective: Surgical treatment of pathological processes involving the ventral craniocervical junction (CCJ) traditionally involves anterior and posterolateral skull base approaches. In cases of bilateral extension, when lesions extend beyond the midline to the contralateral side, a unilateral corridor may result in suboptimal resection. In these cases, the lateral extent of the tumor will prevent extirpation of the lesion via anterior surgical approaches. The authors describe a unilateral operative corridor developed along an extreme lateral trajectory to the anterior aspect of the clival and upper cervical dura, allowing exposure and resection of tumor on the contralateral side. This approach is used when the disease involves the bone structures inherent to stability at the anterior CCJ., Methods: To achieve exposure of the ventral CCJ, an extreme lateral transcondylar transodontoid (ELTO) approach was performed with transposition of the ipsilateral vertebral artery, followed by drilling of the C1 anterior arch. Resection of the odontoid process allowed access to the contralateral component of lesions across the midline to the region of the extracranial contralateral vertebral artery, maximizing resection., Results: Exposure and details of the surgical procedure were derived from anatomical cadavers. At the completion of cadaveric dissection, morphometric measurements of the relevant anatomical landmarks were obtained. Illustrative case examples for approaching ventral CCJ chordomas via the ELTO approach are presented., Conclusions: The ELTO approach provides a safe and direct surgical corridor to treat complex lesions at the ventral CCJ with bilateral extension through a single operative corridor. This approach can be combined with other lateral approaches or posterior infratemporal approaches to remove more extensive lesions involving the rostral clivus, jugular foramen, and temporal bone.

Background: The treatment of atlantoaxial dislocation in very young children is challenging and lacks a consensus management strategy., Discussion: We review the literature on infantile occipitocervical (OC) fusion is appraised and technical considerations are organized for ease of reference. Surgical decisions such as graft type and instrumentation details are summarized, along with the use of bone morphogenic protein and post-operative orthoses., Illustrative Case: We present the case of a 12-month-old who underwent instrumented occipitocervical (OC) fusion in the setting of traumatic atlanto-occipital dislocation (AOD)., Conclusion: Occipitocervical (OC) arthrodesis is obtainable in very young infants and children. Surgical approaches are variable and use a combination of autologous grafting and creative screw and/or wire constructs. The heterogeneity of pathologic etiology leading to OC fusion makes it difficult to make definitive recommendations for surgical management.

Objective: To conduct a comparative analysis of 2 groups of patients with skull base chordomas extending onto the craniovertebral junction, who underwent surgical treatment using extracranial approaches with and without craniocervical fusion., Methods: The study group included 29 patients with skull base chordomas, extending to the craniovertebral junction, who were operated on from 2000 to 2015. The patients underwent the following surgical treatment: posterior craniocervical fusion followed by tumor removal using transoral and combined transoral and transnasal approaches. The reference group included 21 patients with the same disease, who underwent tumor removal surgery using the transoral approach without craniocervical fusion., Results: In the study group, in 27.5% of all cases (8 patients), the tumors were removed radically; in 65.5% of all cases (19 patients), the tumors were removed subtotally; and in 7% of all cases (2 patients), the tumors were removed partially. In the reference group, the extent of surgical radicality was as follows: radical, 0%; subtotal, 19% (4 cases); partial, 81% (17 cases)., Conclusions: Use of the proposed surgical technique in clinical practice may help increase the radicality of tumor excisions, decrease the number of postoperative complications, accelerate the rehabilitation process, and increase the quality of life in patients with skull base tumors extending to the craniovertebral junction., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Background: After a far-lateral transcondylar approach, patients may maintain neutral alignment in the immediate postoperative period, but severe occipitoatlantal subluxation may occur gradually with cranial settling and possible neurological injury. Previous research is based on assumptions regarding the extent of condylar resection and the change in biomechanics that produces instability., Objective: To quantify the extent of bone removal during a far-lateral transcondylar approach, determine the changes in range of motion (ROM) and stiffness that occur after condylar resection, and identify the threshold of condylar resection that predicts alterations in occipitocervical biomechanics., Methods: Nine human cadaveric specimens were biomechanically tested before and after far-lateral transcondylar resection extending into the hypoglossal canal (HC). The extent of condylar resection was quantified using volumetric comparison between pre- and postresection computed tomography scans. ROM and stiffness testing were performed in intact and resected states. The extent of resection that produced alterations in occipitocervical biomechanics was assessed with sensitivity analysis., Results: Bone removal during condylar resection into the HC was 15.4%-63.7% (mean 35.7%). Sensitivity analysis demonstrated that changes in biomechanics may occur when just 29% of the occipital condyle was resected (area under the curve 0.80-1.00)., Conclusion: Changes in occipitocervical biomechanics may be observed if one-third of the occipital condyle is resected. During surgery, the HC may not be a reliable landmark to guide the extent of resection. Patients who undergo condylar resections extending into or beyond the HC require close surveillance for occipitocervical instability., (Copyright © 2016 by the Congress of Neurological Surgeons)

Background: Traumatic atlanto-occipital dislocation is an uncommon, severely unstable pathology, which can lead to detrimental or even fatal neurological impairment. Specifically, children have consistently been reported to be more susceptible to this type of injury because of their disproportionately larger head, ligament laxity, and injury mechanisms. However, to date, rates of missed injury and outcomes including neurologic recovery of pediatric and adult populations following this insult have not been comparatively evaluated., Methods: Standard search engines were used to investigate outcomes of traumatic atlanto-occipital dislocation in children and adolescents compared to adults., Conclusions: Based on case reports and small series from the literature, it seems that children and adolescents tend to have a better likelihood of survival with the possibility of long-term neurological complications. Comparatively, adults who suffer traumatic atlanto-occipital dislocation either succumb to their injuries or survive with very little if any neurological complications.

Background: Congenital anomalies are commonly encountered in the craniovertebral junction because of its unique embryologic development. The craniovertebral junction usually comprises the occiput, atlas, and axis. However, malrotation of the atlas (C1) in between the occiput (C0) and axis (C2) with Chiari I malformation as well as unilateral hypertrophy of the atlanto-occipital joint and a lateral mass manifesting features of high cervical myelopathy is a rarely reported anomaly., Case Description: A 22-year-old woman presented to us with high cervical compressive myelopathy. Imaging revealed rotation of the C1 vertebra approximately 20° toward the left side with right atlanto-occipital joint dislocation and hypertrophy. Imaging also revealed hypertrophy of a right lateral mass of C1, Chiari I malformation, and right atlantoaxial dislocation exposing the right C2 superior facet. She underwent a right extreme far lateral approach comprising a right C1 posterior arch excision and medialization of the right vertebral artery with excision of the hypertrophied atlanto-occipital joint extradurally and posteromedial excision of the superior articular facet of C1. The patient's compressive myelopathy features improved postoperatively., Conclusions: We report the successful management of this rare congenital anomaly and review the literature., (Copyright © 2016 Elsevier Inc. All rights reserved.)

The occipitocervical junction comprises of the occiput condyles, the atlas, and the axis. The radiological evaluation of this region is supported by craniometric measurement methods which are based on predefined anatomical landmarks. The main pathologies of the occipitocervical junction are traumatic injuries, congenital anomalies or normal variants, infections, arthropathies, and tumors. In this article, the anatomy of the occipitocervical junction as well as the most important craniometric measurement methods are explained. Moreover various pathologies and similar appearing normal variants are presented.

Canine atlantooccipital overlapping (AOO) is characterized by a decreased distance between the dorsal arch of the atlas and the supraoccipital bone. Current diagnostic criteria for this condition are subjective and clinician-dependent; objective criteria are needed to allow a reliable and reproducible diagnosis in clinical and research settings and assess clinical significance. We propose four standardized MRI-based measurements to objectively assess the proximity of the atlas to the foramen magnum. Inclusion criteria for dogs in this study were bodyweight <15 kg, age >5 months, and availability of a complete MRI study performed with the craniocervical junction in extension. Exclusion criteria were space-occupying lesions and poor image quality (i.e. unclear bony margins). Measurements also included blinded determinations of skull type, presence of craniocervical junction anomalies and presence and severity of syringomyelia. Clinical status at the time of imaging was noted. Measurements were obtained in 271 dogs; these were reproducible and reliable. Findings varied by skull type: dolichocephalic dogs had smaller foramen magnum, whereas brachycephalic dogs had more cranially and dorsally positioned atlas bodies in comparison to the other skull types. Measurements also increased with increases in bodyweight. This study demonstrated a close association between AOO, syringomyelia and clinical signs. Toy and small breed dogs (including Cavalier King Charles spaniels) showed higher than previously reported prevalence of AOO; its occurrence was also associated with lower bodyweights within the study population of <15 kg toy/small breed dogs., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Approximately one-third of all cervical spine injuries involve the craniocervical junction (CCJ). Composed of the occiput and the first two cervical vertebrae, this important anatomic landmark, in conjunction with an intricate ligamentous complex, is essential to maintaining the stability of the cervical spine. The atlantoaxial joint is the most mobile portion of the spine, predominantly relying on the ligamentous framework for stability at that level. As acute onsite management of trauma patients continues to improve, CCJ injuries, which often lead to death onsite where the injury occurred, are increasingly being encountered in the emergency department. Understanding the anatomy of the CCJ is crucial in properly evaluating the cervical spine, allowing the radiologist to assess its stability in the trauma setting. The imaging findings of important CCJ injuries, such as atlanto-occipital dissociation, occipital condyle fractures, atlas fractures with transverse ligament rupture, atlantoaxial distraction, and traumatic rotatory subluxation, are important to recognize in the acute setting, often dictating patient management. Thin-section multidetector computed tomography with sagittal and coronal reformats is the study of choice in evaluating the extent of injury, allowing the radiologist to thoroughly evaluate the stability of the cervical spine. Furthermore, magnetic resonance (MR) imaging is increasingly being used to evaluate the spinal soft tissues and ligaments, and to identify associated spinal cord injury, if present. MR imaging is also indicated in patients whose neurologic status cannot be evaluated within 48 hours of injury. ., ((©)RSNA, 2015)

Purpose: The aim of this study was to review cases of paediatric patients with craniovertebral junction (CVJ) tuberculosis with a view to try and stratify the cases into different groups which would help plan treatment and hence develop a protocol for treatment of a fairly uncommon condition still widely seen in the developing world., Methods: Twenty-three cases of paediatric craniovertebral tuberculosis had their clinical features and radiology reviewed. The treatment plan in each case was analyzed according to their presentation. The results of treatment after 1 year were assessed in each case., Results: The clinical presentations varied from neck pain with hypoglossal nerve palsy to frank spastic quadriparesis, and frank instability at the atlanto-axial junction was seen in five out of 23 patients. Cold abscesses were seen in 18/23 cases, and severe torticollis was the presentation in 6/23. We graded the children with this condition into three groups: 1) those with instability and gross neurodeficit who required early operative intervention (1 needed trans-oral decompression with posterior fixation and 4 required posterior fixation) 2) those who had severe torticollis and large cold abscesses who were treated with trans-oral aspiration of cold abscess followed by neck immobilization (6/23) and 3) those who did not have significant neck muscle spasm or torticollis and who were treated with immobilization alone (12/23). Only one child in group 3 required delayed intervention for instability which developed after completion of the course of anti-tubercular medication., Conclusions: We concluded that children with craniovertebral tuberculosis should be treated according to their clinical presentation coupled with evidence of radiological instability. Those with gross deficit and instability need early stabilization, those with minimal deficit and no instability but severe pain or torticollis need aspiration of the cold abscess with external immobilization, whereas those without deficit, instability or severe pain may be managed by external orthoses alone. Of course, medical treatment for tuberculosis is necessary in each case.

Object: The craniovertebral junction (CVJ) is unique in the spinal column regarding the degree of multiplanar mobility allowed by its bony articulations. A network of ligamentous attachments provides stability to this junction. Although ligamentous injury can be inferred on CT scans through the utilization of craniometric measurements, the disruption of these ligaments can only be visualized directly with MRI. Here, the authors review the current literature on MRI evaluation of the CVJ following trauma and present several illustrative cases to highlight the utility and limitations of craniometric measures in the context of ligamentous injury at the CVJ., Methods: A retrospective case review was conducted to identify patients with cervical spine trauma who underwent cervical MRI and subsequently required occipitocervical or atlantoaxial fusion. Craniometric measurements were performed on the CT images in these cases. An extensive PubMed/MEDLINE literature search was conducted to identify publications regarding the use of MRI in the evaluation of patients with CVJ trauma., Results: The authors identified 8 cases in which cervical MRI was performed prior to operative stabilization of the CVJ. Craniometric measures did not reliably rule out ligamentous injury, and there was significant heterogeneity in the reliability of different craniometric measurements. A review of the literature revealed several case series and descriptive studies addressing MRI in CVJ trauma. Three papers reported the inadequacy of the historical Traynelis system for identifying atlantooccipital dislocation and presented 3 alternative classification schemes with emphasis on MRI findings., Conclusions: Recognition of ligamentous instability at the CVJ is critical in directing clinical decision making regarding surgical stabilization. Craniometric measures appear unreliable, and CT alone is unable to provide direct visualization of ligamentous injury. Therefore, while the decision to obtain MR images in CVJ trauma is largely based on clinical judgment with craniometric measures used as an adjunct, a high degree of suspicion is warranted in the care of these patients as a missed ligamentous injury can have devastating consequences.

Objective: To assess what kind of information MR examination in flexed and extended positions provides in Down syndrome subjects with suspected cranio-cervical instability., Methods: Between 2005 and 2008, 35 subjects with DS were recruited in the study. Ethics committee approval was granted and a signed informed consent was obtained from the parents. All the subjects were affected by hypotonic status and ligament laxity established by clinical evaluation, but were asymptomatic about focal neurological symptoms due to medullar damage caused by cranio-cervical instability. Each patient underwent lateral supine radiographs and MR imaging in the neutral, active flexed and extended positions. For evaluating the atlanto-axial and atlanto-occipital joint stability, multiple measurements were calculated., Results: A significant reduction of anterior subarachnoid space in flexed position was evident in DS subjects compared to healthy controls in neutral and flexed positions. Both, space available for cord and ligamentous thickness showed significant differences between DS subjects and healthy controls. In DS subjects with occipito-cervical instability, the anterior subarachnoidal space reduction was significantly reduced in flexed position., Conclusions: In DS subjects with asymptomatic cranio-cervical instability, anterior subarachnoidal evaluation and ligamentous status could add new information about the risk of spinal cord damage.

The craniocervical junction (CCJ) functions within a complicated regional anatomy necessary to protect and support vital neurovascular structures. In select instances, vascular pathology can be attributed to this complicated interplay of motion and structure found within this narrow space. The authors report 3 cases of complex vascular pathology related to motion at the CCJ and detail the management of these cases. Two cases involved posterior circulation vascular compression syndromes, and one case involved a vascular anomaly and its relation to aneurysm formation and rupture. The patient in Case 1 was a 66-year-old man with a history of syncopal episodes resulting from the bilateral vertebral artery becoming occluded when he rotated his head. Successful microsurgical decompression at the skull base resulted in patent bilateral vertebral artery V3 segments upon head movement in all directions. The patient in Case 2 was a 53-year-old woman who underwent elective resection of a right temporal meningioma and who experienced postoperative drowsiness, dysphagia, and mild right-arm ataxia. Subsequent MRI demonstrated bilateral posterior inferior cerebel-lar artery (PICA) strokes. Cerebral angiography showed a single PICA, of extradural origin, supplying both cerebellar hemispheres. The PICA exhibited dynamic extradural compression when the patient rotated her head; the bilateral PICA strokes were due to head rotation during surgical positioning. In Case 3, a 37-year-old woman found unconscious in her home had diffuse subarachnoid hemorrhage and evidence of a right PICA aneurysm. A right far-lateral craniectomy was performed for aneurysm clipping, and she was found to have a dissecting aneurysm with an associated PICA originating extradurally. There was a shearing phenomenon of the extradural PICA along the dura of the foramen magnum, and this microtraumatic stress imposed on the vessel resulted in a dissecting aneurysm. This series of complex and unusual cases highlights the authors' understanding of vascular pathology of the CCJ and its management.

Object: Metastatic spinal tumors of the atlantoaxial region are quite uncommon, and surgery is challenging. The aim in this study was to evaluate the safety and efficacy of transoral or transpedicular vertebroplasty combined with posterior fixation in C-2 metastatic disease., Methods: The authors collected from a hospital database all cases of C-2 metastatic tumor treated in the period from January 2009 to December 2012. Cases with histologically confirmed metastatic disease were included, but those with epidural tumorous propagation and signs of spinal cord compression were excluded., Results: Five patients (3 females, 2 males) with osteolytic C-2 metastasis were eligible for this study. In 3 cases a purely posterior approach was taken to perform a dorsal open C-2 biopsy and transpedicular vertebroplasty followed by posterior occipitocervical fixation. In the other 2 cases a transoral C-2 biopsy and vertebroplasty were performed in combination with dorsal occipitocervical fixation during the same operative session. Patients were followed up with regular fluoroscopy, MRI, and CT studies as well as neurological examinations. During an average follow-up of 13 months (range 8-19 months), no surgical or neurological complications were associated with this combined approach. In all cases spinal stability and pain reduction were detected. The average pain score according to the visual analog scale was 3.5 after surgery (range 2-5); before surgery, the average score was 7 (range 6-8). The average volume of polymethylmethacrylate injected was 4 ml. The body and dens of the C-2 vertebra was filled more than 60% for each patient., Conclusions: In this small series, simultaneous intraoperative transoral or transpedicular vertebroplasty and dorsal occipitocervical fixation proved to be a safe and effective treatment for patients with osteolytic C-2 metastatic tumors. These techniques may provide excellent pain relief and improvements in quality of life. The true value of these combined techniques should be evaluated in larger series.

We describe an unusual and rare case of isolated left hypoglossal nerve palsy secondary to compression from a prominent degenerative osteophyte from the left atlanto-occipital joint. The hypoglossal nerve is a purely motor cranial nerve innervating the tongue musculature. Palsy of the hypoglossal nerve is frequently associated with other cranial nerve palsies and can be related to vascular, neoplastic, infectious or traumatic conditions. Isolated hypoglossal nerve palsy is quite rare and very few cases have been reported in the literature to date.

Craniovertebral dislocation is uncommon, but its diagnosis is important taking into account the potential severity of the neurologic complications. A number of causes are known; the most common are Down syndrome, rheumatoid arthritis, Paget's disease, other metabolic bone diseases, and craniocervical trauma. Down's syndrome is a relatively common clinical condition but craniovertebral subluxation is only observed in a small percentage of patients. About half of all cervical spine injuries affect the atlanto-occipital region and C2 vertebra. In rheumatoid arthritis, craniocervical dislocation occurs in up to 40% of patients with severe disease. In Paget's disease, involvement of the craniovertebral region occurs in about 30% of all cases. The clinical neurologic syndrome is characterized by local pain, features of upper spinal cord and medullary compression, positive Lhermitte phenomenon, syncope associated with neck flexion, vertebral artery obstruction or dissection leading to stroke, and asymmetrical lower cranial nerve palsies. Neuroimaging is essential to confirm the clinical diagnosis and to categorize severity. The treatment of this disorder is usually surgical, but traction and external immobilization is relevant in some cases. Specific conditions may require additional treatments such as radiotherapy, antibiotics, or chemotherapy., (© 2014 Elsevier B.V. All rights reserved.)

Fatal falls often involve a head impact, which are in turn associated with a fracture of the skull or cervical spine. Prior authors have noted that the degree of inversion of the victim at the time of impact is an important predictor of the distribution of skull fractures, with skull base fractures more common than skull vault fractures in falls with a high degree of inversion. The majority of fatal fall publications have focused on skull fractures, and no research has described the association between fall circumstances and the distribution of fractures in the skull and neck. In the present study, we accessed data regarding head and neck fractures resulting from fatal falls from a Swedish autopsy database for the years 1992-2010, for the purposes of examining the relationships between skull and cervical spine fracture distribution and the circumstances of the fatal fall. Out of 102,310 medico-legal autopsies performed there were 1008 cases of falls associated with skull or cervical spine fractures. The circumstances of the falls were grouped in 3 statistically homogenous categories; falls occurring at ground level, falls from a height of <3 m or down stairs, and falls from ≥3 m. Only head and neck injuries and fractures that were associated with the fatal CNS injuries were included for study, and categorized as skull vault and skull base fractures, upper cervical injuries (C0-C1 dislocation, C1 and C2 fractures), and lower cervical fractures. Logistic regression modeling revealed increased odds of skull base and lower cervical fracture in the middle and upper fall severity groups, relative to ground level falls (lower cervical <3 m falls, OR = 2.55 [1.32, 4.92]; lower cervical ≥3 m falls, OR = 2.23 [0.98, 5.08]; skull base <3 m falls, OR = 1.82 [1.32, 2.50]; skull base ≥3 m falls, OR = 2.30 [1.55, 3.40]). C0-C1 dislocations were strongly related to fall height, with an OR of 8.3 for ≥3 m falls versus ground level. The findings of increased odds of skull base and lower cervical spine fracture in falls from a height are consistent with prior observations that the risk of such injuries is related to the degree of victim inversion at impact. The finding that C0-C1 dislocations are most common in falls from more than 3 m is unique, an indication that the injuries likely result from high energy shear forces rather than pure tension, as previously thought., (Copyright © 2013 Elsevier Ltd and Faculty of Forensic and Legal Medicine. All rights reserved.)

Atlanto-occipital dislocation (AOD) is a grave injury that is rarely survivable. Patients who do survive often have long-term sequelae resulting from the intracranial damage sustained during the traumatic event. The high impact needed to cause AOD is translated to the intracranial vessels, which can lead to vascular injury. Pseudoaneurysm is one of the possible outcomes of damage to the vessel wall. We present a case of basilar artery pseudoaneurysm diagnosed 5 months after a traumatic AOD who was treated with intracranial stent placement and coiling.

Fixation at the craniovertebral junction (CVJ) is necessary in a variety of pediatric clinical scenarios. Traditionally an occipital bone to cervical fusion is preformed, which requires a large amount of hardware to be placed on the occiput of a child. If a patient has previously undergone a posterior fossa decompression or requires a decompression at the time of the fusion procedure, it can be difficult to anchor a plate to the occipital bone. The authors propose a technique that can be used when faced with this difficult challenge by using the occipital condyle as a point of fixation for the construct. Adult cadaveric and a limited number of case studies have been published using occipital condyle (C-0) fixation. This work was adapted for the pediatric population. Between 2009 and 2012, 4 children underwent occipital condyle to axial or subaxial spine fixation. One patient had previously undergone posterior fossa surgery for tumor resection, and 1 required decompression at the time of operation. Two patients underwent preoperative deformity reduction using traction. One child had a Chiari malformation Type I. Each procedure was performed using polyaxial screw-rod constructs with intraoperative neuronavigation supplemented by a custom navigational drill guide. Smooth-shanked 3.5-mm polyaxial screws, ranging in length from 26 to 32 mm, were placed into the occipital condyles. All patients successfully underwent occipital condyle to cervical spine fixation. In 3 patients the construct extended from C-0 to C-2, and in 1 from C-0 to T-2. Patients with preoperative halo stabilization were placed in a cervical collar postoperatively. There were no new postoperative neurological deficits or vascular injuries. Each patient underwent postoperative CT, demonstrating excellent screw placement and evidence of solid fusion. Occipital condyle fixation is an effective option in pediatric patients requiring occipitocervical fusion for treatment of deformity and/or instability at the CVJ. The use of intraoperative neuronavigation allows for safe placement of screws into C-0, especially when faced with a challenging patient in whom fixation to the occipital bone is not possible or is less than ideal.

Object: Many methods to stabilize and fuse the craniocervical junction have been described. One of the early designs was a contoured (Luque) rod fixated with wires, the so-called Hartshill-Ransford loop. In this study, the authors report their 20-year experience with this surgical technique in children., Methods: The authors reviewed the medical records of patients 18 years of age or younger who underwent dorsal occipitocervical fusion procedures between March 1992 and March 2012 at Le Bonheur Children's Hospital using a contoured rod and wire construct. Data on basic patient characteristics, causes of instability, neurological function at presentation and at last follow-up, details of surgery, complications, and radiographic outcome were collected., Results: Twenty patients (11 male) were identified, with a mean age of 5.5 years (range 1-18 years) and a median follow-up of 43.5 months. Fourteen patients had atlantooccipital dislocation, 2 patients had atlantoaxial fracture-dissociations, 2 had Down syndrome with occipitocervical and atlantoaxial instability, 1 had an epithelioid sarcoma from the clivus to C-2, and 1 had an anomalous atlas with resultant occipitocervical instability. Surgical stabilization extended from the occiput to C-1 in 3 patients, C-2 in 6, C-3 in 8, and to C-4 in 3. Bone morphogenetic protein was used in 2 patients. Two patients were placed in a halo orthosis; the rest were kept in a hard collar for 6-8 weeks. All patients were neurologically stable after surgery. One patient with a dural tear experienced wound dehiscence with CSF leakage and required reoperation. Eighteen patients went on to achieve fusion within 6 months of surgery; 1 patient was initially lost to follow-up, but recent imaging demonstrated a solid fusion. There were no early hardware or bone failures requiring hardware removal, but radiographs obtained 8 years after surgery showed that 1 patient had an asymptomatic fractured rod. There were no instances of symptomatic junctional degeneration, and no patient was found to have increasing lordosis over the fused segments. Five (31%) of the 16 trauma patients required a shunt for hydrocephalus., Conclusions: Despite the proliferation of screw-fixation techniques for craniocervical instability in children, the contoured rod-wire construct remains an effective, less expensive, and technically easier alternative that has been in use for almost 30 years. It confers immediate stability, and therefore most patients will not need to be placed in a halo device postoperatively. A secondary observation in our series was the high (30%) rate of hydrocephalus requiring a shunt in patients with traumatic instability.

Objectives: Few studies have described morphological deviations in obstructive sleep apnoea (OSA) patients on two-dimensional (2D) lateral cephalograms, and the reliability of 2D radiographs has been discussed. The objective is to describe the morphology of the cervical vertebral column on cone beam CT (CBCT) in adult patients with OSA and to compare 2D lateral cephalograms with three-dimensional (3D) CBCT images., Methods: For all 57 OSA patients, the cervical vertebral column morphology was evaluated on lateral cephalograms and CBCT images and compared according to fusion anomalies and posterior arch deficiency., Results: The CBCT assessment showed that 21.1% had fusion anomalies of the cervical column, i.e. fusion between two cervical vertebrae (10.5%), block fusions (8.8%) or occipitalization (1.8%). Posterior arch deficiency occurred in 14% as partial cleft of C1 and in 3.5% in combination with block fusions. The agreement between the occurrence of morphological deviations in the cervical vertebral column between lateral cephalograms and CBCT images showed good agreement (κ = 0.64)., Conclusions: Prevalence and pattern in the cervical column morphology have now been confirmed on CBCT. The occurrence of morphological deviations in the cervical vertebral column showed good agreement between lateral cephalograms and CBCT images. This indicates that 2D lateral cephalograms (already available after indication in connection with, e.g. treatment planning) are sufficient for identifying morphological deviations in the cervical vertebral column. For a more accurate diagnosis and location of the deviations, CBCT is required. New 3D methods will suggest a need for new detailed characterization and division of deviations in cervical vertebral column morphology.

Background: Occipitocervical disease (OCD) in elderly patients will become increasingly common as the population ages. Our experience with occipitocervical fusions (OCF) in this population suggests mixed outcomes., Methods: Twenty consecutive patients over 65 years old underwent OCF between 1995 and 2005. A retrospective review of demographic, presentation, surgical and outcome data was performed., Results: Twenty patients averaging 75.3 years of age (range 65 to 91) were identified. All patients had evidence of myelopathy; however, the primary surgical indications were progressive spinal cord dysfunction (15), brainstem compression (3), and pain (2). Surgical approach was isolated posterior (9), or anterior transoral odontoidectomy followed by posterior stabilization (11). Overall, surgery improved function modestly; average modified Japanese Orthopedic Association functional score (improved 0.9 grades), average Ranawat Myelopathy Score (improved 0.4 grades), and average Nurick Myelopathy Grade (improved 0.6 grades). However, patients with poor preoperative functional assessment (Ranawat grade ≥ III) had greater neurologic improvement than those with good preoperative function, measured by Nurick grade improvement (1 vs. -0.28; P = .03) and Ranawat grade improvement (0.7 vs. -0.2; P = .03). Additionally, the posterior approach demonstrated significant improvement in Japanese Orthopedic Association functional assessment over patients with anterior/posterior approaches (2.2 vs. -0.3; P = .03), with fewer complications (posterior: 1 minor; anterior/posterior: 1 death, 2 major, 8 minor). Perioperative mortality occurred in 5%, and major morbidity in 10% of patients., Conclusions: Preventing or stabilizing neurologic deficit in patients with OCD may require OCF, despite the patient's age. In the elderly population, our data favor using the posterior approach when possible, and demonstrate greater neurologic improvement in patients with poor preoperative function., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Our objectives were to establish a magnetic resonance (MR) protocol for the examination of, and then describe, the normal ligaments and the supporting structures of the occipitoatlantoaxial region. This was done in 10 cadaver dogs. In addition, MR images of three patients with cervical pain localized to the occipitoatlantoaxial region are included to provide examples of ligamentous abnormalities. All ligaments were hypointense in all pulse sequences. The apical, dorsal atlantoaxial, and dorsal longitudinal vertebral ligaments were seen best in the sagittal T1W and PD-weighted images. The transverse ligament was best visualized in the transverse plane in all pulse sequences and appeared to be confluent with the dorsal longitudinal vertebral ligament dorsal to the dens in the sagittal plane. A 20° dorsal plane reconstructed image in 0.6-mm slice thickness was necessary to visualize the alar ligaments, which were visible in 9/10 dogs. The dorsal longitudinal vertebral ligament appeared continuous with the apical ligament and tectorial membrane. Abnormalities in clinically affected dogs included thickening of the alar ligaments, absence of transverse ligament and elongation, and irregularity of the apical ligament., (© 2012 Veterinary Radiology & Ultrasound.)

Background: Approaches to the foramen magnum and upper cervical spine traditionally include the posterior midline, far lateral, and endoscopic endonasal approaches. The far lateral approach is a well-established technique for the removal of pathology ventrolateral to the brainstem and the craniocervical junction, but it may be too extensive for lesions limited to areas far from the midline., Objective: To present an alternative to the commonly used approaches to the foramen magnum and upper cervical., Methods: We used an approach directly overlying ventral or lateral pathology., Results: Two cases are presented in which the direct lateral approach followed by an occipitocervical fusion was successfully performed., Conclusion: This approach can be considered for patients in whom a ventral decompression is necessary but an endoscopic endonasal approach is undesirable or when a ventral, lateral, and ventrolateral resection of tumor, pannus, or infection is required.

The normal anatomy of the cervical spine and various imaging techniques for the evaluation of torticollis are reviewed, and possible causes of torticollis in infants and children are discussed, with an emphasis on relevant imaging findings. Torticollis is a congenital or acquired deformity characterized by rotational deformity of the cervical spine with secondary tilting of the head. Although torticollis is a sign of an underlying disease process, its presence does not imply a specific diagnosis, and the cause should be sought if torticollis persists or is associated with other symptoms. Congenital torticollis, seen in neonates and infants, usually results from craniocervical vertebral anomalies or muscular causes, although ocular abnormalities such as congenital paralytic squint (strabismus) and congenital nystagmus should also be considered. Acquired torticollis, seen in older children and adolescents, is often secondary to trauma, infection, or tumors. Imaging should be used as a general screening tool only after a complete medical history and clinical findings have been obtained. In newborns or infants with congenital torticollis, ultrasonography (US) is the modality of choice. In cases of acquired torticollis resulting from trauma, conventional radiography (lateral and anteroposterior views) should be the first-line imaging modality. In nontraumatic acquired torticollis, computed tomography (CT) of the neck or cervical spine is the initial imaging study. If CT findings are negative, magnetic resonance (MR) imaging of the brain and cervical spine should be performed. The use of multiple imaging modalities (conventional radiography, US, CT, and MR imaging) is common in the radiologic work-up of torticollis, and radiologists must understand the role of each imaging modality in patients of various ages., (© RSNA, 2012.)

Study Design: Evaluation by simulation of screw insertion using fine-cut computed tomographic (CT) scans and screw trajectory software., Objective: To evaluate the feasibility and optimal trajectory of the occipital condylar screw., Summary of Background Data: To the best of our knowledge, no large series examining the feasibility and optimal trajectory of occipital condylar screws have been published., Methods: We simulated unicortical placement of a 4 × 18-mm screw using 1-mm sliced CT scans and 3-dimensional screw trajectory software in 314 occipital condyles of 157 patients. With the screw tip directed toward a point just below the tip of the basion on lateral fluoroscopy, 3 entry points were compared in view of success rate of screw placement, safe range of medial angulation in an axial plane, and maximum screw length., Results: The lateral entry point had the highest success rate (93.0%) of screw placement, mean safe range of the medial angulation (10.9°), and maximum screw length (20.7 mm), followed by the middle (92.0%, 10.8°, and 20.6 mm, respectively) and medial (74.2%, 7.7°, and 19.7 mm, respectively) entry points. While the lateral and the middle entry points did not have any statistically significant difference in the 3 parameters, they were significantly better than the medial entry point. All 3 entry points had highly variable ranges of safe medial angulation, making it difficult to provide a single recommended value., Conclusion: Screw placement is feasible in up to 93% of the occipital condyles. The lateral and the middle entry points are significantly better than the medial entry point. Selection between the middle and the lateral entry points should be individualized taking into account local anatomic variation. Because the medial angulation of these screws is highly variable, preoperative 3-dimensional CT evaluation and possibly even intraoperative navigation may be required.

Ganglion cysts (ganglia) are benign lesions of the soft tissue arising in the periarticular space. We present a 54-year-old woman with a 5-month history of headache and weakness of the tongue with deviation to the left side who had a rare extraneural intradural bilobate ganglion cyst of the atlanto-occipital joint compressing the hypoglossal nerve. An MRI showed a bilobate cystic lesion in the premedullary cistern on the left side at the level of the hypoglossal canal. This lesion was removed using a lateral suboccipital approach in the semi-sitting position with removal of the C1 hemiarch. The lesion proved to be a ganglion cyst on histopathology. Intracranial juxtafacet (ganglion and synovial) cysts compressing the hypoglossal nerve should be considered in the differential diagnosis with other lesions of this region. Although there was no recurrence at 30-month follow-up, there was no significant improvement of the tongue weakness. We describe our surgical strategy and discuss the pathogenesis of the cyst., (Copyright © 2011 Elsevier Ltd. All rights reserved.)

Objective: The aim of the current study was to investigate the biomechanical stability and fixation strength provided by a posterior approach reconstruction technique to realign the craniovertebral junction., Methods: We tested seven human cadaver occipito-cervical spines (occiput-C4) by applying pure moments of ± 1.5 Nm on a spine tester. Each specimen was tested in the following modes: 1) intact; 2) injured; 3) spacers alone at C1-C2 articulation (S); 4) spacers plus C1-C2 Posterior Instrumentation (S+PI); and 5) spacers plus C1-C2 posterior instrumentation plus midline wiring (S+PI+MLW). C1-C2 range of motion for each construct was obtained in flexion-extension, lateral bending, and axial rotation., Results: In all the loading modes, S, S+PI, and S+PI+MLW constructs significantly reduced range of motion compared with the intact and injured condition (P < 0.05). There was no statistical difference between any of the three instrumentation constructs (P > 0.05)., Conclusions: This study investigated the biomechanics of the posterior approach technique for realignment of the craniovertebral junction and also made comparisons with additional posterior fixations. The stand-alone spacers were stable in all three loading modes. Posterior instrumentation increased the stability as compared to stand-alone spacers. The third point of fixation, carried out by using midline wiring, increased the stability further. However, there was not much difference in the stability imparted with the midline wiring versus without. The present study highlights the biomechanics of this novel concept and reaffirms the view that distraction of the C1-C2 articular facets and direct articular joint atlantoaxial fixation would be an ideal method of management of basilar invagination., (Copyright © 2012 Elsevier Inc. All rights reserved.)