Craniovertebral Junction Instability Research Articles

Exoscopic removal of the fourth ventricle choroid plexus papilloma with use of a midline suboccipital osteoplastic craniotomy.

Choroid plexus papillomas are relatively rare vascular tumors. In this video, the authors present a pediatric patient who underwent exoscopic removal of the fourth ventricle choroid plexus papilloma with the use of a midline suboccipital osteoplastic craniotomy. The exoscope in the fourth ventricle lesion helps to improve visualization in all directions, with the surgeon being able to maintain a comfortable position throughout the procedure. In addition, the midline suboccipital osteoplastic craniotomy helps to reduce the potential risks of complications, in particular, CSF leak and craniovertebral junction instability. The video can be found here: https://stream.cadmore.media/r10.3171/2023.10.FOCVID23106.

Mobility Assessment Using Multi-Positional MRI in Children with Cranio-Vertebral Junction Anomalies.

This study aimed to assess the relevance of using multi-positional MRI (mMRI) to identify cranio-vertebral junction (CVJ) instability in pediatric patients with CVJ anomalies while determining objective mMRI criteria to detect this condition. Data from children with CVJ anomalies who underwent a mMRI between 2017 and 2021 were retrospectively reviewed. Mobility assessment using mMRI involved: (1) morphometric analysis using hierarchical clustering on principal component analysis (HCPCA) to identify clusters of patients by considering their mobility similarities, assessed through delta (Δ) values of occipito-cervical parameters measured on mMRI; and (2) morphological analysis based on dynamic geometric CVJ models and analysis of displacement vectors between flexion and extension. Receiver operating characteristics (ROC) curves were generated for occipito-cervical parameters to establish instability cut-off values. (3) Additionally, an anatomical qualitative analysis of the CVJ was performed to identify morphological criteria of instability. Forty-seven patients with CVJ anomalies were included (26 females, 21 males; mean age: 10.2 years [3-18]). HCPCA identified 2 clusters: cluster №1 (stable patients, n = 39) and cluster №2 (unstable patients, n = 8). ΔpB-C2 (pB-C2 line delta) at ≥2.5 mm (AUC 0.98) and ΔBAI (Basion-axis Interval delta) ≥ 3 mm (AUC 0.97) predicted instability with 88% sensibility and 95% specificity and 88% sensitivity and 85% specificity, respectively. Geometric CVJ shape analysis differentiated patients along a continuum, from a low to a high CVJ motion that was characterized by a subluxation of C1 in the anterior direction. Qualitative analysis found correlations between instability and C2 anomalies, including fusions with C3 (body p = 0.032; posterior arch p = 0.045; inferior articular facets p = 0.012; lateral mass p = 0.029). We identified a cluster of pediatric patients with CVJ instability among a cohort of CVJ anomalies that were characterized by morphometric parameters with corresponding cut-off values that could serve as objective mMRI criteria. These findings warrant further validation through prospective case-control studies.

Clinical and Radiological Outcomes after Surgical Stabilization of Craniovertebral Junction – A Single-center Experience

Abstract Background and Objectives: Craniovertebral instability and its surgical management require a thorough knowledge of the anatomy and dynamics of the craniovertebral junction (CVJ). Due to the wide range of mobility and proximity of vital neurovascular structures, these surgeries demand high technical skill and precision. It is very difficult to suggest a single good technique for CVJ stabilization as each procedure has got its own indications and benefits. Novel techniques and gadgets like neuro navigation and robotic arms help surgeons to minimize complications, thereby improving the overall functional outcome. In this study, we are analyzing the retrospective data of CVJ instabilities surgically managed by freehand technique in our institute. Materials and Methods: We did a retrospective analysis of 33 patients operated on for craniocervical junction instability for 7 years from January 1, 2015, to December 31, 2021. We analyzed the clinical and radiological presentations and postoperative outcomes at 3 weeks, 6 months, and after 1 year. The distribution of clinical presentation in terms of neck pain, myelopathy, restricted neck movements, and lower cranial nerve palsy was evaluated and correlated with the demographic parameters. The paired “t”- test was used to correlate the clinical and radiological outcomes after surgery. Results: The paired “t” value of the clinical improvement assessed with the preoperative and postoperative Japanese Orthopedic Association (JOA) myelopathic scores was − 4.376 with P < 0.001, which indicates a significant clinical improvement 6 months after surgery. Among the 33 patients evaluated, only three patients developed a slight reduction in the JOA score after surgery, which was improved within 1 year. All the patients achieved satisfactory trabecular bone formation at the graft site and decorticated joint facets without any clinical or radiological evidence of implant failure. Among the C2 pedicle screws, 3 (7.5%) were having vertebral foraminal impingement, and 2 (5%) were having medial cortical violation and spinal canal impingement. All the patients with radiological evidence of implant malposition were clinically intact and did not show any deterioration of the studied myelopathic score (JOA). Conclusions: As the bony anatomy and the vascular course of the CVJ vary from patient to patient, thorough preoperative planning is mandatory for the surgical management of CVJ instability. In our study, the clinical and radiological improvement after surgical stabilization of craniovertebral instability by freehand technique is comparable with the available data. The overall risk of screw malposition and associated lethal complications may be minimized by adding modern technologies such as neuronavigation, robotic arms, and three-dimensional C-arm in the armamentarium.

Craniovertebral Junction Instability after Oncological Resection: A Narrative Review.

The craniovertebral junction (CVJ) is a complex transition area between the skull and cervical spine. Pathologies such as chordoma, chondrosarcoma and aneurysmal bone cysts may be encountered in this anatomical area and may predispose individuals to joint instability. An adequate clinical and radiological assessment is mandatory to predict any postoperative instability and the need for fixation. There is no common consensus on the need for, timing and setting of craniovertebral fixation techniques after a craniovertebral oncological surgery. The aim of the present review is to summarize the anatomy, biomechanics and pathology of the craniovertebral junction and to describe the available surgical approaches to and considerations of joint instability after craniovertebral tumor resections. Although a one-size-fits-all approach cannot encompass the extremely challenging pathologies encountered in the CVJ area, including the possible mechanical instability that is a consequence of oncological resections, the optimal surgical strategy (anterior vs posterior vs posterolateral) tailored to the patient's needs can be assessed preoperatively in many instances. Preserving the intrinsic and extrinsic ligaments, principally the transverse ligament, and the bony structures, namely the C1 anterior arch and occipital condyle, ensures spinal stability in most of the cases. Conversely, in situations that require the removal of those structures, or in cases where they are disrupted by the tumor, a thorough clinical and radiological assessment is needed to timely detect any instability and to plan a surgical stabilization procedure. We hope that this review will help shed light on the current evidence and pave the way for future studies on this topic.

Surgical treatment of craniovertebral junction instability in children with Down syndrome: a systematic review.

Down syndrome (DS) affects 1 in 700 live births and approximately one-third of patients develop craniovertebral junction (CVJ) instability, diagnosed by clinical examination and radiological measures such as the atlantodens interval (ADI) and space available for the cord (SAC). Patients with symptomatic CVJ instability are at increased risk for spinal cord injury. There are no guidelines for surgical management of CVJ instability in DS, the existing literature is sparse, and there is a lack of consistent pediatric data. This systematic review aimed to synthesize practice patterns of the surgical management of CVJ stability in pediatric DS patients to facilitate future standardization of care. Peer-reviewed studies reporting surgical management of CVJ instability in pediatric DS patients were systematically reviewed. Inclusion criteria were studies reporting primary data on patients younger than 18 years with DS, who had CVJ instability evaluation and underwent surgical treatment. Bias risk was assessed. Descriptive statistics of the independent patient data were presented. Interval variables were analyzed using the Wilcoxon rank-sum test. Of 1056 records, 38 studies were included. Of the included patients, 169 (6%) underwent surgery. The surgical indication was symptomatic, radiologically confirmed CVJ instability in 81% of the patients, presenting with myelopathy (30%), weakness (25%), abnormal gait (24%), torticollis (15%), and neck pain (14%). A cutoff of ADI ≥ 4 mm or SAC ≤ 14 mm, cord compression, cord signal change, and anomalous bony anatomy were used in diagnosing CVJ instability. Surgical approaches focused on internal fixation with posterior occipitocervical or atlantoaxial instrumented fusion in 57% and 44% of patients, respectively. Autograft, wiring, and allograft constructs were used in 48%, 45%, and 9% of patients. Anterior cervical approaches were performed in 6% of patients. Preoperative and postoperative external orthoses were used in approximately 50% of patients. The surgical mortality rate was 3%, and the complication rate was 36%. Assessment of CVJ instability in DS is based on radiographic and clinical factors. Surgery is recommended if symptoms are present, and the procedure type depends on patient factors, degree of instability, anomalous bony anatomy, and reduction results to relieve cord compression. Most commonly, posterior instrumented fusion is used. However, further research is required to determine the strength of evaluation methods, create standardized guidelines for evaluation and surgical treatment, and investigate the long-term results of different surgical techniques.

Diffuse idiopathic skeletal hyperostosis: A functional enemy of vertebral stability - Case series and surgical consideration of craniovertebral junction involvement.

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. 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. This was a multicentric case series. 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. 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. 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.

Morphological analysis and morphometry of the occipital condyle and its relationship to the foramen magnum, jugular foramen, and hypoglossal canal: implications for craniovertebral junction surgery.

Anatomical knowledge of the occipital condyle (OC) and its relationships to surrounding structures is important for avoiding injury during craniovertebral junction (CVJ) surgeries. This study was conducted to evaluate the morphology and morphometry of OC and its relationship to foramen magnum, jugular foramen (JF), and hypoglossal canal (HC). Morphometric parameters including length, width, height, and distances from the OC to surrounding structures were measured. The oval-like condyle was the most common OC shape, representing for 33.0% of all samples. The mean length, width and height of OC were 21.3±2.4, 10.5±1.4, and 7.4±1.1 mm, respectively. Moreover, OC was classified into three types based on its length. The most common OC length in both sexes was moderate length or type II (62.5%). The mean distance between anterior tips and posterior tips of OC to basion, and opisthion were 11.5±1.4, 39.1±3.3, 25.2±2.2, and 27.4±2.7 mm, respectively. The location of intracranial orifice of HC was commonly found related to middle 1/3 of OC in 45.0%. JF was related to the anterior 2/3 of OC in 81.0%, the anterior 1/3 of OC in 12.5%, and the entire OC length in 6.5%. These morphological analysis and morphometric data should be taken into consideration before performing surgical operation to avoid CVJ instability and neurovascular structure injury.

Craniovertebral Junction Instability in the Setting of Chiari Malformation.

Described in the seminal paper by Hans Chiari in 1891, the Chiari I malformation (CMI) is a radiographic diagnosis commonly encountered by neurosurgeons and is often treated surgically with generally positive clinic outcomes. Studies have documented that 1% to 4% of patients undergoing MRI of the brain or cervical spine will be diagnosed with CMI, characterized by greater than 5mm tonsillar herniation below the foramen magnum. More recently CMI has been described as a spectrum of disease, which includes Chiari 0, Chiari 1.5, and the complex Chiari. Primarily through multicenter clinical outcomes research, our understanding of the pathology continues to evolve.

Perils of fusing the occipital squama to the cervical spine for craniovertebral junction instability

Perils of fusing the occipital squama to the cervical spine for craniovertebral junction instability

Evaluating Craniovertebral Stability in Chiari Malformation Coexisting with Type II Basilar Invagination: An Observational Study Based on Kinematic Computed Tomography and Its Clinical Application

Treatment of Chiari malformation (CM) is controversial, especially when it coexists with "stable" or Type II basilar invagination (CM+II-BI). Precise evaluation of craniovertebral junction (CVJ) stability is crucial in such patients; however, this has never been validated. This study aimed to dynamically evaluate atlanto-condyle and atlantoaxial stability by kinematic computed tomography (CT) and report its surgical treatment. The study recruited 101 patients (control, CM, and CM+II-BI groups: 48, 34, and 19 patients, respectively). During kinematic CT, the CVJ stability-related parameters were measured and compared between the 3 groups. The surgical strategy for treating CM+II-BI was based on these results. Preoperative and postoperative images were acquired, and functional scores were used to assess the outcome. Among the 3 groups, the length of the clivus and the height of the condyle were the shortest in the CM+II-BI group, which was accompanied by the greatest rotation of the atlas and atlanto-condyle facet movement on cervical flexion and extension. Moreover, in such patients, increased Chamberlain's baseline violation indicated the aggregate invagination of the odontoid in the flexed position, and asymmetric displacement of atlantoaxial facets was observed. Seventeen CM+II-BI patients underwent surgical treatment with atlantoaxial distraction and occipitocervical fusion. The syringomyelia width and tonsillar herniation decreased significantly, and functional scores indicated symptom relief and good outcomes. CVJ instability, especially the ultramovement of atlanto-condyle facets, commonly exists in II-BI as evaluated using kinematic CT. The surgical strategy of atlantoaxial distraction and occipitocervical fusion should be considered to treat such patients.

Surgical Anatomy of the occipital condyle and its relation to hypoglossal canal

Occipital condyles (OC) are two bony structures located laterally to the foramen magnum (FM) on the inferior surface of the occipital bone. It is commonly described as an ovoid structure. Craniovertebral junction (CVJ) is an area that connects the cranium to the upper cervical spine. It is bounded laterally by the jugular foramen (JF), hypoglossal canal (HC), and OC. Lesions at CVJ are difficult to manage because of their location and complex anatomic relations. Stability of CVJ after surgery in depends mainly on the resection of OC. HC has been used as a landmark for the extent of OC resection. It was claimed to locate in the middle part of OC. OC resection should not extend beyond HC to prevent CVJ instability. However, previous study showed that the HC was not always located at the middle part of OC. This study aimed to focus on the measurement of OC and its relation to HC in dry skull collected from Thailand for improving the successful surgical outcome.One hundred dry skulls of equal number of both sex were examined for the shape and dimension of each OC. The location of intra and extra cranial orifice of HC (iHc and eHC) related to OC length and the distance to the posterior edge of OC (OCPE‐iHC, OCPE‐eHC) were determined. The results showed that the most prevalence of OC shape was oval‐like (33%) and the least was ring like (1%). Symmetrical OC shape was found in 46% of cases. The mean OC length was 22.13+2.51mm in male and 20.50+ 2.08 mm in female with a significant difference between sex (p=000). The OC width and height were 10.41+1.48 and 7.45+ 1.14 mm in male, 10.62+ 1.34 and 7.34+ 1.13 mm in female. No statistical significant difference of OC width and OC height between sex was found. The dimension of OC did not show any significant difference between sides. The location of iHC was mostly related to middle 1/3 of OC in 54% on the left side and located at the junction between anterior and middle 1/3 of OC in 36% on the right side. In contrast, eHC was located at anterior 1/3 of OC in 81% and 67% on the left and right side, respectively. None was related to posterior 1/3 of OC. Symmetrical location of iHC and eHC was found in 36% and 64% of cases, respectively. The distance OCPE‐iHC, OCPE‐eHC was 9.16+ 1.56, 14.1.0 + 1.98 mm in male and 8.83+ 1.62, 13.30+ 2.4 mm in female. Statistical significant difference between sex was found in OCPE‐eHC (p=0.011). In conclusion, the OC length is longer in male, the eHC located more anteriorly than iHC, therefore resection of the OC should not beyond posterior 1/3 of the OC length or about 7 mm from the posterior edge of OC. These morphometric data might be a benefit for surgical planning on resection of the occipital condyle to avoid injury to neurovascular structure and reserve the stability of craniovertebral junction.

Influence of clivo-axial angle on outcome after foramen magnum decompression in adult symptomatic Chiari type 1 malformation

ObjectiveA significant number of patients with Chiari type 1 malformation (CM1) have abnormal clivo-axial angle (CXA) without other radiographic indicators of basilar invagination or craniovertebral junction (CVJ) instability. This study aimed to investigate whether abnormal CXA alone influences postoperative outcomes among patients who underwent foramen magnum decompression (FMD). MethodsA total of 44 adult patients with symptomatic CM1 undergoing FMD without CVJ fixation were enrolled. Preoperative clinical characteristics and radiographic measurement include the CXA as well as the radiographic indicators of basilar invagination and instability were recorded. The univariate and multivariate binary logistic regression tests were used to identify the potential prognostic factors for favorable outcomes. ResultsEighteen patients (41%) and 26 patients (59%) were divided into unfavorable and favorable outcome groups, respectively. Baseline demographic and imaging characteristics were similar between the two patient groups. The mean CXA was 132.3 ± 15.8 and 145 ± 13.6 degrees in the unfavorable and favorable groups, respectively (P = 0.091). In the favorable outcome group, the proportion of patients with CXA > 135 degrees was significantly higher than that of the unfavorable outcome group (77% vs. 44%; P = 0.05). The CXA > 135 degrees was found to be the only independent predictor associated with favorable outcomes (adjusted risk ratio 2.16; 95% CI 1.01–4.76; P = 0.047). ConclusionThe preoperative CXA of greater than 135 degrees was identified as a prognostic factor associated with a favorable outcome at one-year follow-up after FMD among adult patients with symptomatic CM1 without basilar invagination or CVJ instability. This factor should be incorporated into preoperative considerations.

Double Anchoring Technique of Occipito-Cervical Fixation Using Innovative Occipital Plate: A Preliminary Study.

Occipito-cervical fixation (OCF) provides immediate rigid fixation to cranio-vertebral junction (CVJ); however, in current practice, the optimal occipito-cervical fixation method is arguable. The aim of this study was to test the safety and efficacy of a newly designed inside-outside occipital (OC) plate system for the treatment of cranio-vertebral junction instability. Thirty-two patients of CVJ instability were treated using this new OC plate system. Safety and efficacy of this new OC plate was evaluated radiologically and clinically. Follow-up period ranged from 9 to 23 months. During the follow-up, no implant failure, recurrent subluxation, or newly developed instability at adjacent levels occurred, except in one patient in whom C2 screw pullout occurred due to trauma. All patients showed a satisfactory fusion at three months follow-up examination. These preliminary results suggest that this OC plate system is a simple, safe, and effective method for providing immediate internal rigid fixation of the CV junction. Long-term results are needed to determine the superiority of this OC plate over other methods of occipital fixation.

C1-C2 arthroplasty for craniovertebral junction instability: A preliminary proof of concept in human cadavers.

ABSTRACTBackground:The atlantoaxial complex contributes to significant neck movements, especially the axial rotation. Its instability is currently treated with various C1-C2 fusion techniques. This however, considerably hampers the neck movements and affects the quality of life; a C1-C2 motion preserving arthroplasty could potentially overcome this drawback.Objectives:We evaluate the range of motion (ROM) of lateral C1-C2 artificial joints in cadaveric models.Materials and Methods:This is an in vitro cadaveric biomechanical study. After C1-C2 arthroplasty through a posterior approach, the C1-C2 ROM was tested in 4 fresh-frozen human cadaveric specimens, before and after destabilization.Results:The mean axial rotation demonstrated after the placement of C1-C2 joint implants was 15.46 degrees on the right and 16.03 degrees on the left side; the prosthesis provided stability, with 46% of the baseline C1-C2 axial rotation on either side. The ROM achieved in the other axes was less compared with that of intact specimens. To initiate rotation, a higher moment of 1.5 Nm was required in the presence of joint implants compared to 0.5 NM in unimplanted specimens.Conclusions:In our preliminary ROM evaluation, the C1-C2 arthroplasty appears to be stable and provides about half of the range of atlantoaxial rotation. It has the potential for joint motion preservation in the treatment of atlantoaxial instability resulting from lateral C1-C2 joint pathologies.

The enigma of acute worsening after a latent interval in post-operative patients of craniovertebral junction instability

ObjectiveFor reasons that are poorly understood and still undocumented, few patients of craniovertebral junction (CVJ) anomalies with instability/atlantoaxial dislocation (AAD) in our practice have been seen to suffer unprecedented acute neurological deterioration with respiratory compromise about 48–72 h post-surgery. This has been specifically observed after an uneventful, stable clinical condition in the immediate postoperative period. This study attempts to elucidate the factors and outcomes related to such latent worsening. Patients and methodsThe 4-year surgical data of 268-patients with CVJ instability (AAD/basilar-invagination) who underwent C1-C2 fixation were retrospectively studied. The relevant factors of 17 patients who showed such deterioration were compared with that of the remaining in a multivariate model. ResultsSeventeen patients had acute neurological worsening with respiratory arrest after a latent period. Ten improved at follow-up. Contrary to the general expectation, poor preoperative neurological score or severe dislocation that needed considerable manipulation did not influence such worsening. Dural injury in patients with associated Chiari malformation and vertebral arterial (VA) injury emerged as independent factors (p < 0.01) associated with this pattern of delayed neurological decline. ConclusionsWe report our management and outcomes of a unique subset of AAD with neurological worsening in the postoperative period after 48–72 h. Such a subgroup was not previously identified in literature. Dural lacerations in AAD with Chiari, and VA injury seem to predispose to such complications and should be prevented at best. Close observation, and caution regarding early extubation (<72 h) is recommended in this subset despite an apparently uneventful immediate postoperative neurological status.

Fiberoptic bronchoscopy versus video laryngoscopy guided intubation in patients with craniovertebral junction instability: A cinefluroscopic comparison.

Background: Manipulation during endotracheal intubation in patients with craniovertebral junction (CVJ) anomalies may cause neurological deterioration due to underlying instability. Fiberoptic-bronchoscopy (FOB) is better than video laryngoscope (VL) for minimizing cervical spine movement during intubation. However, evidence suggesting superiority of FOB in patients with CVJ instability is lacking. We prospectively compared dynamic movements of the upper cervical spine during intubation using FOB with VL in patients with CVJ anomalies.Methods: A prospective, randomized, and clinical trial was conducted in 62 patients of American Society of Anaesthesiologist Grade I-II aged between 12 and 65 years with CVJ anomalies. Patients were randomized for intubation under general anesthesia with either VL or FOB. The intubation process was done with application of skeletal traction and recorded cinefluroscopically. The dynamic interrelationship of bony landmarks (horizontal, vertical, and diagonal distances between fixed points on posterior C1 and C2) was analyzed to indirectly calculate alteration of the upper cervical spinal canal diameter (at CVJ). Atlanto-dental interval (ADI) was calculated wherever possible.Results: The alteration in canal diameter (using bony landmarks) at CVJ during intubation was not significant with the use of either VL or FOB (P > 0.05). In 41 patients, where ADI could be measured, ADI was reduced (increased spinal canal diameter) in a greater number of patients in VL group when compared to FOB group (P < 0.05).Conclusion: Using rigid skull traction, intubation under general anesthesia with VL offers similar advantage as FOB in terms of the spinal kinematics in patients with CVJ anomalies/instability. Nevertheless, greater number of patients intubated with VL may have an advantage of increased cervical spinal canal diameter when compared to FOB.

Aspects of Surgical Treatment of Spinal Pathology in the Patient with Gurler Syndrome

The clinical case of surgical treatment of combined spinal pathology in the child with Gurler syndrome is described in the article. Indications, major risk factors and aspects of surgical treatment of spinal pathology at this nosology are described in detail; all the approaches are analyzed according to the literature. Background. We would like to draw the attention of our colleagues to this problem with this clinical case. We want to emphasize the peculiarities of orthopedic manifestations in patients with mucopolysaccharidosis type IH (MPS IH). The most crucial is timely detection and surgical treatment. Clinical case description. This article describes the aspects of surgical treatment of spinal pathology in the patient with MPS IH: progressive kyphotic deformation, stenosis and craniovertebral junction instability, significant neurological deficit, internal organs functional disorders. Conclusion. Patients with MPS are characterized by multilevel orthopedic pathology which requires continuous follow-up throughout the life by single multidisciplinary team of specialists.

Atlantoaxial and Subaxial Cervical Spinal Instability in Two Cases with Neurofibromatosis-Type 1.

This is a report of two patients who were diagnosed to have NF-1. The patients had severe dystrophic soft tissue and bone changes leading to craniovertebral junction and subaxial cervical spinal instability and deformity. Both the patients underwent atlantoaxial and subaxial cervical spinal stabilization. No bone, soft tissue or tumor resection was done for decompression. Both patients had gratifying clinical recovery. Follow-up in both the patients is more than 12 months.

Craniovertebral junction chordomas: Case series and strategies to overcome the surgical challenge.

Introduction:Chordomas are rare and malignant primary bone tumors. Different strategies have been proposed for chordomas involving the craniovertebral junction (CVJ) compared to other locations. The impossibility to achieve en bloc excision, the impact on stability and the need for proper reconstruction make their surgical management challenging.Objective:The objective is to discuss surgical strategies in CVJ chordomas operated in a single-center during a 7 years' experience (2013-2019).Methods:Adult patients with CVJ chordoma were retrospectively analyzed. The clinical, radiological, pathological, and surgical data were discussed.Results:A total number of 8 patients was included (among a total number of 32 patients suffering from skull base chordoma). Seven patients underwent endoscopic endonasal approach (EEA), and posterior instrumentation was needed in three cases. Three explicative cases were reported: EEA for midline tumor involving lower clivus and upper cervical spine (case 1), EEA and complemental posterior approach for occurred occipitocervical instability (case 2), C2 chordoma which required aggressive bone removal and consequent implant positioning, focusing on surgical planning (timing and type of surgical stages, materials and customization of fixation system) (case 3).Conclusion:EEA could represent a safe route to avoid injuries to neurovascular structure in clival locations, while a combined approach could be considered when tumor spreads laterally. Tumor involvement or surgical procedures could give raise to CVJ instability with the need of complementary posterior instrumentation. Thus, a tailored preoperative planning should play a key role, especially when aggressive bone removal and implant positioning are needed.

Effect of Etiology of Craniovertebral Junction Instability on Clinical Characteristics, Course, and Outcomes in Patients Undergoing Occipitocervical Fusion

Prasad, Nikil BS; Shlobin, Nathan A; Azad, Hooman; Mitra, Akash; Hopkins, Benjamin BS; Cloney, Michael MD; Dahdaleh, Nader S MD Author Information