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Osteogenesis Imperfecta (OI) is a disease that causes bone fragility and deformities, affecting both the cranial base and the craniocervical junction, and may lead to other neurological disorders. A retrospective cross-sectional study was carried out based on cephalometric analysis of the cranial base in a sample of patients with OI, in lateral skull radiographs and magnetic resonance imaging (MRI), comparing them with a sample of age-matched controls. When the different variables of the craniocervical junction were analyzed, significance was found in comparisons with the different age groups. All measurements of the variables studied stabilized as growth progressed. For most of the variables, the severity of the disease influences the measurements of the skull base, with statistically significant differences. Both age and severity of the disease are factors that directly influence the anatomy of the craniocervical junction in these patients and may serve as indicators in the early detection and prevention of other derived alterations.

OBJECTIVE The goal of this study was to assess the social determinants that influence access and outcomes for pediatric neurosurgical care for patients with Chiari malformation type I (CM-I) and syringomyelia (SM). METHODS The authors used retro- and prospective components of the Park-Reeves Syringomyelia Research Consortium database to identify pediatric patients with CM-I and SM who received surgical treatment and had at least 1 year of follow-up data. Race, ethnicity, and insurance status were used as comparators for preoperative, treatment, and postoperative characteristics and outcomes. RESULTS A total of 637 patients met inclusion criteria, and race or ethnicity data were available for 603 (94.7%) patients. A total of 463 (76.8%) were non-Hispanic White (NHW) and 140 (23.2%) were non-White. The non-White patients were older at diagnosis (p = 0.002) and were more likely to have an individualized education plan (p < 0.01). More non-White than NHW patients presented with cerebellar and cranial nerve deficits (i.e., gait ataxia [p = 0.028], nystagmus [p = 0.002], dysconjugate gaze [p = 0.03], hearing loss [p = 0.003], gait instability [p = 0.003], tremor [p = 0.021], or dysmetria [p < 0.001]). Non-White patients had higher rates of skull malformation (p = 0.004), platybasia (p = 0.002), and basilar invagination (p = 0.036). Non-White patients were more likely to be treated at low-volume centers than at high-volume centers (38.7% vs 15.2%; p < 0.01). Non-White patients were older at the time of surgery (p = 0.001) and had longer operative times (p < 0.001), higher estimated blood loss (p < 0.001), and a longer hospital stay (p = 0.04). There were no major group differences in terms of treatments performed or complications. The majority of subjects used private insurance (440, 71.5%), whereas 175 (28.5%) were using Medicaid or self-pay. Private insurance was used in 42.2% of non-White patients compared to 79.8% of NHW patients (p < 0.01). There were no major differences in presentation, treatment, or outcome between insurance groups. In multivariate modeling, non-White patients were more likely to present at an older age after controlling for sex and insurance status (p < 0.01). Non-White and male patients had a longer duration of symptoms before reaching diagnosis (p = 0.033 and 0.004, respectively). CONCLUSIONS Socioeconomic and demographic factors appear to influence the presentation and management of patients with CM-I and SM. Race is associated with age and timing of diagnosis as well as operating room time, estimated blood loss, and length of hospital stay. This exploration of socioeconomic and demographic barriers to care will be useful in understanding how to improve access to pediatric neurosurgical care for patients with CM-I and SM.

Background: We describe patients who were recognized via conventional radiographs of the skull as manifesting wormian bones. Wormian bones are not a specific diagnostic entity and can be seen in variable forms of syndromic disorders. Materials and Methods: Seven children and three adults (of 10–28 years) were seen and diagnosed in our departments. The principal complaints for the pediatric and adult group were: ligamentous hyperlaxity, a history of delayed walking and occasional fractures, which later in life started to manifest a constellation of neurological symptoms such as nystagmus, persistent headache, and apnea. Conventional radiographs were the first traditional tools used to recognize wormian bones. We performed 3D reconstruction CT scans to further understand the precise etiology and the nature of these wormian bones and attempted to connect them with a broad spectrum of unpleasant clinical presentations. Our group of patients was consistent with the phenotypic and genotypic diagnoses of osteogenesis imperfecta type I and type IV as well as patients with multicentric carpotarsal osteolysis syndrome. Results: Three-dimensional reconstruction CT scan of the skulls confirmed that these worm-like phenotypes are in fact stemmed from the progressive softening of the sutures. The overall phenotype of the melted sutures is akin to overly stretched pastry. The most concerning sutures in this pathological process are the lambdoid. The overstretching of the lambdoid sutures was responsible for the development of sub-clinical basilar impression/invagination. Patients with certain forms of skeletal dysplasia such as osteogenesis imperfecta type I and IV manifested the heterozygous mutation of COL1A1/COLA2, shown as typical overstretching of the sutures. Similarly, patients with multicentric carpotarsal osteolysis syndrome with a heterozygous missense mutation of MAFB also manifested the phenotype of overly stretched pastry along the skull sutures. Conclusion: What we encountered via 3D reconstruction CT scan in our group of patients was entirely different than the traditional description that can be found in all relevant literature of the last decades. The worm-like phenomenon is in fact a pathological sequel occurring as a result of a progressive softening of the sutures, which results in the overstretching of the lambdoid sutures, a pathological process roughly similar to an overly stretched soft pastry. This softening is totally connected to the weight of the cerebrum (the occipital lobe of the cerebrum). The lambdoid sutures represent the weight-bearing zone of the skull. When these joints are loose and soft, they adversely alter the anatomical structures of the skull and lead to a highly hazardous derangement of the craniocervical junction. The latter causes the pathological upward invasion of the dens into the brain stem, leading to the development of morbid/mortal basilar impression/invagination.

Objective Patients with instability because of congenital craniovertebral anomalies often have complex C1-C2 osseovascular anomalies. C2 nerve root sacrifice has been described to address such difficult anatomy during posterior C1-C2 fixation and has its own downsides. Its preservation as a recent alternative poses greater surgical challenge, and the considerations differ from other causes of craniovertebral junctional instability; the pertaining outcomes have been scarcely studied. The objective of this study was to prospectively determine the feasibility and outcomes related to C2 nerve root preservation in patients with congenital atlantoaxial dislocation (CAAD) after posterior C1-C2 fixation. Methods In this observational study, 63 patients (126 nerve roots) with CAAD after posterior fixation were prospectively assessed. Underlying osseovascular anomalies affecting the feasibility of C2 nerve root preservation, and C2 nerve–related dysfunction at 12 months follow-up were analyzed. Results The overall C2 nerve root preservation rate was 89.7%. Even in the presence of extreme joint obliquity/spondyloptosis and anomalous vertebral artery, it was feasible in about three fourths. After preservation, 28.3% patients developed new-onset C2 nerve root dysfunction: neuralgia in 2, dysesthesia in 6, and hypoesthesia/paresthesia in 9. The symptoms were not disabling in most patients. Conclusions In most patients with CAAD, C2 nerve root preservation is feasible despite an aberrant bony and vascular anatomy. A few patients after nerve root preservation develop related symptoms that are conservatively manageable, with no significant adverse consequences. Given the controversy in the literature on C2 nerve sacrifice–related outcomes, we favor an attempt at C2 nerve root preservation.

Occipitocervical fusion is necessary for many pathologies of the craniocervical junction. The anatomy of the region is unique, and fusion can cause significant morbidity. This retrospective review aims to investigate the complication rates and outcomes of occipitocervical fixation. This is a retrospective review of 128 patients with occipitocervical fixation operated between 1994 and 2020. The average follow-up is 63 months. The indications of occipitocervical fixation were basilar invagination (53 patients; 41.4%), trauma (25 patients; 19.5%), tumor (23 patients; 18%), instability due to rheumatoid arthritis (13 patients; 10.2%), cervical deformity (7 patients; 5.5%) and os odontoideum (7 patients; 5.5%). There were six early postoperative (1st month) deaths. We observed complications in 67 patients (52%). Most common complication was implant-related (32%), followed by wound problems (23.4%), systemic and other complications (11.7%), neurologic complications (6.2%). Implants are removed in 31 patients (24%) for different reasons: deep wound infection (7), local pain and restriction of head movements (21), respiratory distress and swallowing problems (2), screw fracture and local pain (1). Occipitocervical fixation has quite large number of complications and significantly restricts head movements. With the advent of our biomechanical concepts, indications should be limited, and shorter cervical fixations should be preferred. Diagnostic: individual cross-sectional studies with consistently applied reference standard and blinding.

Craniocervical abnormalities in osteogenesis imperfecta (OI) such as basilar invagination or cervical kyphosis can cause severe neurological morbidity. These abnormalities may be more frequent in OI type V compared with other OI subtypes of similar disease severity, underlining the importance of screening in this group. Craniocervical abnormalities in osteogenesis imperfecta (OI) can cause severe neurological morbidity. Although radiological cranial base abnormalities in OI have been well described in the literature, there are limited data on these abnormalities in OI type V and their association with clinical sequelae. A retrospective case series on patients with craniocervical abnormalities in OI type V at our institution. Craniocervical abnormalities were present in 7 of 37 patients with OI type V (19%). For 5 patients (age at last follow-up: 5 to 26 years; 2 females), sufficient information was available for inclusion in the case series. All had genetically confirmed OI type V. Age range at diagnosis of the craniocervical abnormality was 1 day to 18 years. Basilar invagination was present in 3 patients; 2 had cervical kyphosis. Dysplasia of upper cervical vertebrae or base of skull was seen in 3 patients. The severity of the craniocervical abnormality did not clearly correlate with the severity of the OI phenotype. Three patients required surgical intervention (ages 7, 11, and 26 years) due to compression of the spinal cord or brainstem. Craniocervical abnormalities were detected incidentally or on screening in 3 patients, and only 2 had significant positive findings on neurological examination. A variety of craniocervical abnormalities are seen in OI type V including dysplasia of the cervical vertebrae. These cases highlight the importance of screening patients with OI type V with lateral skull and cervical spine x-rays throughout childhood and after skeletal maturity.

Sleep apnoea is common in patients with Basilar Invagination with Arnorld Chiari Malformation (ACM). Various studies have shown its incidence in the range of 60-70% among such patients. Most of the studies have shown improvement in sleep disturbances after decompressive surgeries for Chiari Malformations. There is no report of postoperative deterioration due to sleep apnoea in these patients. Authors report two cases of basilar invagination associated with ACM and Platybasia, who deteriorated probably due to worsening of pre-existing sleep disorders on 3rd and 7th postoperative days after their surgeries, despite clinico-radiological improvements during their early post-operative courses. Authors discuss literature related to sleep apnoea in basilar invagination associated with Chiari Malformations and share precautions, which are relevant and should be undertaken in such patients especially during early post-operative periods to avoid alarming complication which may occur even in experienced hands.

Atlas assimilation (AA) may be associated with atlantoaxial dislocation, Chiari malformation (CM), and basilar invagination. The importance of AA in the context of craniocervical junction (CVJ) anomalies is unclear. Considering this context, this study's objective is to discuss the role of AA in the management of CVJ anomalies, especially in CM. A comprehensive literature review was performed. In addition, some illustrative cases were discussed on the basis of our review. Finally, we propose a theoretic algorithm to evaluate patients with AA and CM. AA is a proatlas segmentation anomaly that may be complete or incomplete. It may be totally asymptomatic or symptomatic as the result of transferred shifted forces onto the C1-2 joints, leading to clear instability (atlantoaxial dislocation) or mild C1-2 instability. Cautious surgical planning may be required due to associated vertebral artery anomalies. AA with concomitant C2-C3 segmentation failure is highly associated with late C1-C2 instability. CVJ decompression failure was reported in patients with CM and a low clivus canal angle (130-135 degrees). Patients with assimilated anterior C1 arches usually have evident AAD. CM patients with AA generally have type 1 BI or type 2 BI and are reported with higher rates of CVJ instabilities when compared with those "pure" CM. Dynamic examinations may provide additional evidence of atlantoaxial instability. Although AA per se is not considered an unstable configuration, further and detailed evaluations of patients with CM associated with AA are necessary. Some associated unstable configurations required concomitant CVJ fixation.

Case report. Juvenile rheumatoid arthritis (JRA) typically presents with fever, rash, anterior uveitis, and/or joint pain. We present three cases with initial torticollis due to rotatory subluxation of C1–C2 as an initial sign of JRA. Three girls, ages 5–9, presented with C1-2 rotatory subluxation. Traction was able to reduce the atlanto-axial joint in all cases. Based on imaging, history, exam, and laboratory results, they were diagnosed with JRA. After reduction of the atlantoaxial joint, they were transitioned to a halo vest and disease-modifying antirheumatic drugs (DMARDs). The older 2 children underwent C1-2 fusion. The younger child has minimal symptoms and has not undergone surgical intervention 4 years from initial presentation. Rotatory subluxation can be the first presenting sign of JRA. Younger children may be able to be treated conservatively with traction and medication, while older children may require occiput to C2 fusion due to bony destruction and basilar invagination. IV.

Background The knowledge of the development and the anatomy of the posterior cranial fossa (PCF) is crucial to define the occurrence and the prognosis of diseases where the surface and/or the volume of PCF is reduced, as several forms of craniosynostosis or Chiari type I malformation (CIM). To understand the functional and morphological changes resulting from such a hypoplasia is mandatory for their correct management. The purpose of this article is to review the pertinent literature to provide an update on this topic. Methods The related and most recent literature addressing the issue of the changes in hypoplasic PCF has been reviewed with particular interest in the studies focusing on the PCF characteristics in craniosynostosis, CIM, and achondroplasia. Results and conclusions In craniosynostoses, namely, the syndromic ones, PCF shows different degrees of hypoplasia, according to the different pattern and timing of early suture fusion. Several factors concur to PCF hypoplasia and contribute to the resulting problems (CIM, hydrocephalus), as the fusion of the major and minor sutures of the lambdoid arch, the involvement of the basal synchondroses, and the occlusion of the jugular foramina. The combination of these factors explains the variety of the clinical and radiological phenotypes. In primary CIM, the matter is complicated by the evidence that, in spite of impaired PCF 2D measurements and theories on the mesodermal defect, the PCF volumetry is often comparable to healthy subjects. CIM is revealed by the overcrowding of the foramen magnum that is the result of a cranio-cerebral disproportion (altered PCF brain volume/PCF total volume). Sometimes, this disproportion is evident and can be demonstrated (basilar invagination, real PCF hypoplasia); sometimes, it is not. Some recent genetic observations would suggest that CIM is the result of an excessive growth of the neural tissue rather than a reduced growth of PCF bones. Finally, in achondroplasia, both macrocephaly and reduced 2D and 3D values of PCF occur. Some aspects of this disease remain partially obscure, as the rare incidence of hydrocephalus and syringomyelia and the common occurrence of asymptomatic upper cervical spinal cord damage. On the other hand, the low rate of CIM could be explained on the basis of the reduced area of the foramen magnum, which would prevent the hindbrain herniation.

Introduction. Each of the pathologies is rare and can lead to compression of the brainstem and spinal cord, with the development of a “mixed” clinical picture. The tactics of treating such patients differs from one author to another.The objective is to present the author’s experience in treating patients with basilar invagination associated with type I Chiari malformation and to analyze the literature on the methods of surgical treatment of this pathology.Materials and methods. From 2014 to 2019, 3 patients with a basilar invagination and type I Chiari malformation were surgically treated at the N. I. Pirogov National Medical and Surgical Center. Indications for surgical intervention were long-term progressive neurological disorders, lack of effect from conservative therapy. Patients underwent anterior transnasal and posterior decompression of nerve structures followed by stabilization.Results. All patients were evaluated 12 months after surgery. All patients in neurological status showed positive dynamics. According to magnetic resonance imaging of the craniovertebral junction, 2 patients showed positive dynamics: regression of the myelopathy, a decrease in the diameter of the syringomyelic cyst.Conclusion. The criteria for anterior transnasal decompression are the predominance of bulbar disorders and / or paresis in the extremities in the clinical picture; posterior decompression of nerve structures, indicated in the presence of specific symptoms of type I Chiari malformation and / or syringomyelia. Taking into account the results of the latest published studies it can be assumed that stabilization is a necessary option in the treatment of patients with this pathology.

We describe our experience with management of basilar invagination (BI) with the atlantoaxial dislocation (C1/C2) joint reduction technique, including posterior atlantoaxial internal fixation.From 2008 to 2018, eleven patients with atlantoaxial dislocation (AAD) and BI underwent surgical reduction using C1/C2 the joint reduction technique with a fibular graft/peek cage placement followed by C1 lateral mass/C2 pedicle screw fixation. In two cases that we originally planned to perform C1/C2 joint reduction, occiput-C2 pedicle screw fixation was performed instead due to intraoperative challenges. Post-operative course and surgical complications will be discussed.A total of 13 patients, with an average age of 30.46 ± 13.23 years (range 12-57), were operated. In one patient, iatrogenic vertebral artery injury occurred without any neurological complication. JOA score improved from 10.45 ± 1.128 to 15.0 ± 1.949 (C1/C2 joint reduction technique with fibular graft/cervical PEEK cage of BI patients together with AAD seems to be an effective and safe surgical method of treatment.

Objective The conventional criteria for defining the basilar invagination (BI) focus on the relationship of odontoid tip to basion and opisthion, landmarks that are intrinsically variable especially in presence of occipitalised atlas. A universal single reference line is proposed that helps in unequivocally establishing the diagnosis of BI, may be relevant in establishing both Goel types A and B BI, as well as in differentiating a ‘very high’ from ‘regular’ BI. Methods Study design – case-control study. In 268 patients (group I with BI [n = 89] including Goel type A BI [n = 66], Goel type B BI [n = 23], and group II controls [n = 179]), the perpendicular distance between odontoid tip and line subtended between posterior tip of hard palate-internal occipital protuberance (P-IOP line) was measured. Logistic regression analysis determined factors influencing the proposed parameter (p < 0.05). Results In patients with a ‘very high’ BI (n = 5), the odontoid tip intersected/or was above the P-IOP line. In patients with a ‘regular’ BI (n = 84), the odontoid tip was 6.56 ± 3.9mm below the P-IOP line; while in controls, this distance was 12.53 ± 4.28 mm (p < 0.01). In Goel type A BI, the distance was 7.01 ± 3.78 mm and in type B BI, it was 5.07 ± 4.19 mm (p = 0.004). Receiver-operating characteristic curve analysis identified 9.0 mm (8.92–9.15 mm) as the cut-point for diagnosing BI using the odontoid tip-P-IOP line distance as reference. Conclusion The odontoid tip either intersecting the P-IOP line (very high BI) or being < 9 mm below the P-IOP line (Goel types A and B BI) is recommended as highly applicable criteria to establish the diagnosis of BI. This parameter may be useful in establishing the diagnosis in all varieties of BI.

Study design Retrospective study. Objective To evaluate the morphologic features of the subaixal cervical spine in patients with basilar invagination (BI) and provide information for the accurate screw placement in this region. Summary of background data BI is a congenital anomaly, comprising a wide range of abnormal structures. The screw fixation can be required in situation that BI is combined with subaxial cervical spine pathologies. However, there are no literatures specifically addressed the subaxial cervical morphology of BI. Method A total of 42 BI patients were included in this retrospective study. Forty-two patients without head or cervical disease were matched for sexes and ages. Information on radiographic features of the subaxial cervical spine was collected and compared systematically. Results There were no differences in the age and sex between the BI and control group. The BI group manifested a wider pedicle and laminar than the control group at all cervical levels, except for the pedicle of C6 and C7, and the laminar of C3 and C6. In addition, the BI group had a wider lateral mass from C3 to C5 than the control group. There were no differences in most measurements of the length of pedicle, laminar, and lateral mass. Conclusion BI patients have a wider pedicle and laminar than the general population in the subaxial cervical spine, but the same size in length of pedicle, laminar and lateral mass.Level of Evidence: 4.

CONTEXT: Spinal-generated movement disorders are a complex group of medical conditions, frequently misdiagnosed, originating in the spinal cord or from combined peripheral and central nervous system involvement. In this case report, we describe a novel form of position-dependent dyskinesia due to severe craniocervical malformation. FINDINGS: An 83-year-old woman with basilar invagination at the C2 vertebra above the line of Chamberlain, occipitocervical lordosis, platybasia with a short clivus, ankylosis of the C1–C2 complex and fusion of the C1 arch developed an unusual pattern of position-dependent left arm dyskinesia triggered by bending her neck forward with simultaneous contact of the flexed elbow with a flat surface. Symptoms did not improve with anticonvulsants and she progressed and died suddenly. CONCLUSION/CLINICAL RELEVANCE: A newly described form of position-dependent arm dyskinesia can be associated with severe craniocervical malformation.

Cerebellofaciodental syndrome is characterized by facial dysmorphisms, intellectual disability, cerebellar hypoplasia, and dental anomalies. It is an autosomal-recessive condition described in 2015 caused by pathogenic variants in BRF1. Here, we report a Brazilian patient who faced a diagnostic challenge beginning at 11 months of age. Fortunately, whole-exome sequencing (WES) was performed, detecting the BRF1 variants NM_001519.3:c.1649delG:p.(Gly550Alafs*36) and c.421C>T:p.(Arg141Cys) in compound heterozygosity, thus finally achieving a diagnosis of cerebellofaciodental syndrome. The patient is currently 25 years old and is the oldest patient yet reported. The clinical report and a review of published cases are presented. Atlanto-occipital fusion, a reduced foramen magnum and basilar invagination leading to compression of the medulla-spinal cord transition are skeletal findings not reported in previous cases. The description of syndromes with dental findings shows that such anomalies can be an important clue to relevant differential diagnoses. The cooperation of groups from different international centers made possible the resolution of this and other cases and is one of the strategies to bring medical advances to developing countries, where many patients with rare diseases are difficult to diagnose definitively.

Revision surgery in an irreducible atlantoaxial dislocation (IAAD) previously operated with a posterior approach is challenging. Multiple modalities using anterior, posterior, and dual approaches have been described. We report a so far unreported technique of revision surgery by posterior implant removal and decompression with anterior transoral release followed by posterior instrumentation. 14-year male with basilar invagination (BI) with IAAD, previously operated with posterior decompression and instrumented occipitocervical fusion presented three months later with post-traumatic recurrence of myelopathy with quadriparesis with Di Lorenzo grade 4 and loss of reduction. He was operated with a posterior implant and early fusion mass removal with extended foramen magnum decompression (FMD), followed by anterior transoral release with a satisfactory reduction on traction, and finally, a posterior revision instrumented occipitocervical fusion. At 2-year follow-up, the patient was symptom-free with Di Lorenzo grade 1 and cervicomedullary angle improvement from 97.4° to 141.2°; achieving bony fusion. Single-stage posterior-anterior transoral-posterior approach can be used to achieve satisfactory reduction for a revision BI with IAAD with prior posterior instrumentation.

Study design A Prospective Study. Objective To assess results of posterior occipito-cervical decompression and fusion operated with intra-operative traction/manipulation and instrumented reduction in cases of Basilar Invagination(BI). Methods Total 22 patients of 8–65 years with diagnosed BI were operated for posterior occipito-cervical fusion by intra-operative traction/manipulation and instrumented reduction. Fusion was done using autologous bone graft taken from iliac crest. Immediate post-operative, first month and then every 3 months’ follow-up examination were done for minimum period of 2 years. Results 22 patients (10 males,12 females) with mean age of 23.9 years having BI were included. 11 patients had C1 occipitalization, 4 had platybasia and 9 had atlanto-axial dislocation (AAD). 1 patient with os odontoideum with kyphotic deformity expired on 4th postoperative day due to respiratory insufficiency (mortality rate 4.54%). Neurological improvement by at least by one grade according to RANAWAT’s and/or NURICK’S scale was observed in 17/21 patients (80.95%). 3 patients remained static and 1 had neuro-worsening. Mean mJOA score of 13.14 improved to 16.24. All had reduction of dens below foramen magnum according to McRae, chamberlain line and Ranawat index. Bone graft fused in all patients as confirmed with CT scan and dynamic X-rays. 1 wound dehiscence and 1 asymptomatic implant loosening were seen on follow-up. Conclusion Surgical treatment of BI with intra-operative traction/manipulation, instrumented reduction and posterior occipito-cervical fusion can achieve good correction of radiology, functional performance and clinical neurology as well as excellent fusion rates without adverse effects of trans-oral surgery.

Atlantoaxial joint distraction is a key procedure for the treatment of selected patients affected by basilar invagination (BI). In recent years, several authors have reported various techniques of distraction and fixation of the C1-C2 joint using different types of intra-articular spacers, with or without posterior fixation. We review the pertinent literature and propose a feasibility study on the use of a new device for the distraction of the C1-C2 joint aimed to the descent of the dens out of the foramen magnum suggesting its application on selected cases of BI.The GL-DTRAX Cervical Cage-SE is a cage approved by the Food and Drug Administration for distraction and fixation of subaxial cervical spine. Five adult cadaveric specimens were dissected surgically to evaluate the feasibility of DTRAX insertion inside the C1-C2 joint through a posterior approach.The cages were uneventfully set into the C1-C2 intra-articular space of all samples without the need to sacrifice C2 nerve roots and ganglia. Postoperative cervical computed tomography scanning confirmed the correct fitting of the devices in every sample.This cadaveric study highlights the feasibility of the DTRAX cage as a C1-C2 intra-articular device producing a substantial distraction of atlantoaxial complex and suggesting a possible therapeutic role in selected cases of BI.

OBJECTIVE To describe the foramen magnum angle (FMA) as a new parameter for basilar invagination (BI) type B. METHODS The FMA was performed on sagittal slice of magnetic resonance imaging (MRI) as a line from the hard palate to the opisthion (angle vertex), and another line from the opisthion to the basion. The MRIs from 31 participants with BI type B and 96 controls were used. Intraclass correlation coefficient, descriptive data, and receiver operating characteristic (ROC) curve were used for statistical analysis at the 95% confidence interval. RESULTS The interobserver agreement of the FMA was 0.952. Patients with BI type B had a FMA significantly greater (25.9° ± 9.3°) than control participants (11.6° ± 4.9°) (P < 0.001). The area under the ROC curve showed a diagnostic value of 0.947. The FMA showed sensitivity 0.900 and specificity 0.854 for the cutoff criterion 17° (P < 0.001). CONCLUSIONS The FMA had an optimal diagnostic value that provided complementary evidence to investigate BI type B.

Purpose: Rheumatoid arthritis (RA) affecting the cervical spine results in instability and deformity that can be divided into the subtypes C1–C2 horizontal (atlantoaxial instability), C0–C2 vertical (basilar invagination), subaxial, and combined instabilities. The aim of this study was to compare the surgical treatments and outcomes of RA-related deformity and instability in a population-based setting. Patients and Methods: All patients with RA in the national Swespine register from January 1, 2006, to March 20, 2019, were assessed. Baseline characteristics, surgical treatments, European Myelopathy Scale (EMS), Neck Disability Index, the Visual Analog Scale for neck and arm pain as well as pre- and postoperative imaging were analyzed. The follow-up time points were at 1-, 2-, and 5 years after surgery. Results: A total of 176 patients were included. There were 62 (35%) patients with C1–C2 horizontal instability, 48 (27%) with C0–C2 vertical instability, 19 (11%) patients with subaxial instability, 43 (24%) patients with combined instability, and 4 patients without instability served as controls. The EMS improved in the C1–C2 horizontal instability group after fusion surgery (Δ =2.6 p) but remained within baseline confidence intervals in the other groups. All patients regardless of instability improved in pain. The subaxial instability had the highest risk of death within 5 years after surgery (11/19, 58%). The most dangerous complications due to implant failure were seen in patients instrumented with laminar hooks. Conclusion: The neurological outcome after fusion surgery is poor and the death rate is high in patients with cervical RA-related instability and deformity.

OBJECTIVEWhile a select population of pediatric patients with Chiari malformation type I (CM-I) remain asymptomatic, some patients present with tussive headaches, neurological deficits, progressive scoliosis, and other debilitating symptoms that necessitate surgical intervention. Surgery entails a variety of strategies to restore normal CSF flow, including increasing the posterior fossa volume via bone decompression only, or bone decompression with duraplasty, with or without obex exploration. The indications for duraplasty and obex exploration following bone decompression remain controversial. The objective of this study was to describe an institutional series of pediatric patients undergoing surgery for CM-I, performed by a single neurosurgeon. For patients presenting with a syrinx, the authors compared outcomes following bone-only decompression with duraplasty only and with duraplasty including obex exploration. Clinical outcomes evaluated included resolution of syrinx, scoliosis, presenting symptoms, and surgical complications.METHODSA retrospective review was conducted of the medical records of 276 consecutive pediatric patients with CM-I operated on at a single institution between 2001 and 2015 by the senior author. Imaging findings of tonsillar descent, associated syrinx (syringomyelia or syringobulbia), basilar invagination, and clinical assessment of CM-I–attributable symptoms and scoliosis were recorded. In patients presenting with a syrinx, clinical outcomes, including syrinx resolution, symptom resolution, and impact on scoliosis progression, were compared for three surgical groups: bone-only/posterior fossa decompression (PFD), PFD with duraplasty (PFDwD), and PFD with duraplasty and obex exploration (PFDwDO).RESULTSPFD was performed in 25% of patients (69/276), PFDwD in 18% of patients (50/276), and PFDwDO in 57% of patients (157/276). The mean follow-up was 35 ± 35 months. Nearly half of the patients (132/276, 48%) had a syrinx. In patients presenting with a syrinx, PFDwDO was associated with a significantly higher likelihood of syrinx resolution relative to PFD only (HR 2.65, p = 0.028) and a significant difference in time to symptom resolution (HR 2.68, p = 0.033). Scoliosis outcomes did not differ among treatment groups (p = 0.275). Complications were not significantly higher when any duraplasty (PFDwD or PFDwDO) was performed following bone decompression (p > 0.99).CONCLUSIONSIn this series of pediatric patients with CM-I, patients presenting with a syrinx who underwent expansile duraplasty with obex exploration had a significantly greater likelihood of syrinx and symptom resolution, without increased risk of CSF-related complications, compared to those who underwent bone-only decompression.

Objectives: Craniovertebral junction (CVJ) abnormalities constitute a group of treatable neurological disorders, especially in the Indian subcontinent. Thus, it is essential that clinicians should be able to make a precise diagnosis of abnormalities and rule out important mimickers on multidetector computed tomography (MDCT) as this information ultimately helps determine the management, prognosis, and quality of life of patients. CVJ is the most complex part of the cervical region. Congenital malformations of this region can cause serious neurological deficit and require a surgical intervention. The present study was undertaken to know the embryological basis of the CVJ and to identify commonly observed congenital CVJ abnormalities, their frequency, and mode of presentation. Materials and Methods: Diagnosed cases of CVJ anomalies on dynamic MDCT head were reviewed at a tertiary care center between January 2014 to December 2019. Type of anomaly, clinical presentation, and associated malformations were recorded. Different types of variations were expressed in terms of percentage. Results: Congenital anomalies were seen in 42 cases. Fifteen types of anomalies were detected. Anomalies were either singly or in combination. The CVJ anomalies were more common in young adults (28%), almost equal in both sexes. The most common anomaly was basilar invagination (52.3%), followed by atlanto-occipital assimilation (33.3%), and Arnold–Chiari malformation is the most common soft tissue anomaly. In fourteen cases, additional anomalies of other vertebrae were present. The most common symptoms were weakness of extremities, neck pain, paresthesia, torticollis, and gait disturbances. About 28 patients got improved, 8 patients had residual deficit as that of preoperative status, and 4 patients got deteriorated after surgery, at 1-month follow-up. About 34 patients had improved, 5 remained static, and 3 patients got worsened at the end of 3-month follow-up. About 37 patients had improved, 4 patients remained static, and 2 patients got deteriorated at 6 months of follow-up. The patients with increased atlantodens interval 3–5 mm showed 77% improvement after surgery. Conclusion: Congenital CVJ anomalies, though rare, are fatal. CVJ abnormalities constitute an important group of treatable neurological disorders with diagnostic dilemma. The atlantodental interval is the most important preoperative prognostic marker. Dynamic CT imaging can provide additional useful information to the diagnosis of CVJ instability. To prevent long-term neurological problems, early diagnosis and treatment of congenital bony CVJ anomalies is important.

Background Introduction of a posterior spacer for atlantoaxial joint distraction followed by posterior stabilization is a commonly performed procedure for irreducible atlantoaxial dislocation. We present a unique case in which posterior distraction was associated with increased risk of injury to the vertebral artery (VA) owing to its anomalous course, and hence a novel anterior distraction technique was used. Case Description A 45-year-old woman presented with severe neck pain for 1 month with gait imbalance and history of occipital headache for 1 year. Clinical examination revealed upper motor neuron–type findings. Hoffmann sign was positive bilaterally. Clinically, the patient had Nurick grade 4 cervical myelopathy. Magnetic resonance imaging showed basilar invagination along with Arnold-Chiari malformation and syrinx formation at C3-C4 vertebral levels. CT angiography revealed anomalous VAs directly overlying the atlanto-occipital joint. Owing to the anomalous route of the VA and unfavorable slope of facet joints, a 2-step anterior reduction followed by posterior stabilization surgery was planned. We achieved complete reduction using a 10-mm titanium cage inserted via a retropharyngeal approach. Following anterior reduction, instrumented in situ occipitocervical fusion was performed using a plate and screw construct. At 2-year follow-up, the patient is ambulating independently without gait imbalance and with successful radiologic fusion. Conclusions The craniovertebral junction has a unique pathoanatomy, and the course of the vertebral artery is variable. Appropriate investigations, including computed tomography angiography, with adequate surgical planning will provide a desirable long-term outcome. Our novel technique has the potential to add a new dimension to the management of irreducible atlantoaxial dislocation.

Background The management of atlantoaxial dislocation (AAD) associated with basilar invagination (BI) is challenging, and traditional posterior-only approaches lack the ability to release the anterior soft tissue resulting in unsatisfactory reduction. Furthermore, vertebral artery anomalies and deformed anatomy increase surgical risks. Objective To introduce a safe and efficient technique to reduce congenital AAD and BI through a single-stage posterior-only approach. Methods A total of 65 patients with AAD and concomitant BI who had congenital osseous abnormalities were retrospectively analyzed. All patients had anterior soft tissue released through a posterior-only approach, followed by intra-facet cages implantation, cantilever correction, and instrumentation. Clinical results were measured using the Japanese Orthopedic Association (JOA) scale, and radiographic measurements included the atlanto-dental interval, the distance of odontoid tip above Chamberlain's line, clivus-canal angle (CCA), and syrinx length. Paired t-tests were used to compare preoperative and postoperative measurements. Results The mean JOA score increased from 10.98 to 14.40 at 1-yr follow-up. Complete reduction of AAD and BI was achieved in 48 patients (73.8%). The mean CCA improved from 115° preoperatively to 129° postoperatively. Reduction of syrinx size was observed in 14 patients at 1 wk and in 35 patients 1 yr after surgery. All patients achieved bony fusion. Conclusion Posterior intra-articular distraction followed by cage implantation and cantilever correction can achieve complete reduction in most cases of congenitally anomalous AAD associated with BI.

We evaluate the efficacy, safety and indications of single stage posterior release, reduction, and fixation of basilar invagination (BI) with irreducible atlantoaxial dislocation (IAAD).Seventeen patients with BI and IAAD consecutively underwent one-stage release, reduction, and fixation by a posterior approach from July 2000 to June 2015 were followed up for at least 12 months. There were 8 males. Mean age was 56 35.2 ± 13.8 years (range 12-56). The clinical symptoms and signs of the patients were recorded. Pre- and postoperative imaging examinations were performed. Neurological function was assessed using the Japanese Orthopedic Association (JOA) and Ranawat scores.Average follow-up time was 47.4 months (12-97 months). The JOA score increased from preoperative 4-10 (8.06 ± 2.52) to postoperative 13-16 (15.20 ± 0.62). The preoperative Chamberlain line, McRae line, Wackenheim line, atlantodens interval, and cervico medullary angle were 12.52 ± 5.17 mm, 6.59 ± 3.04 mm, 6.96 ± 4.32 mm, 9.88 ± 1.93 mm, and 115.35 ± 12.40°, respectively. The postoperative values were 2.0 ± 3.67 mm, -3.06 ± 1.85 mm, -1.76 ± 2.88 mm, 1.17 ± 1.18 mm, and 136.76 ± 11.44°, respectively.One-stage release, reduction, and fixation for patients with BI and IAAD through a posterior approach is safe and efficient.

BACKGROUND: Occipital-cervical fusion (OCF) and ventral decompression (VD) may be used in the treatment of pediatric Chiari-1 malformation (CM-1) with syringomyelia (SM) as adjuncts to posterior fossa decompression (PFD) for complex craniovertebral junction pathology. OBJECTIVE: To examine factors influencing the use of OCF and OCF/VD in a multicenter cohort of pediatric CM-1 and SM subjects treated with PFD. METHODS: The Park-Reeves Syringomyelia Research Consortium registry was used to examine 637 subjects with cerebellar tonsillar ectopia ≥ 5 mm, syrinx diameter ≥ 3 mm, and at least 1 yr of follow-up after their index PFD. Comparisons were made between subjects who received PFD alone and those with PFD + OCF or PFD + OCF/VD. RESULTS: All 637 patients underwent PFD, 505 (79.2%) with and 132 (20.8%) without duraplasty. A total of 12 subjects went on to have OCF at some point in their management (PFD + OCF), whereas 4 had OCF and VD (PFD + OCF/VD). Of those with complete data, a history of platybasia (3/10, P = .011), Klippel-Feil (2/10, P = .015), and basilar invagination (3/12, P

OBJECTIVE Developmental bony craniovertebral junction (CVJ) anomalies seem to have a genetic basis and also abnormal joint morphology causing atlantoaxial dislocation (AAD) and basilar invagination (BI). METHODS DNA extracted polymerase chain reaction single-stranded conformation polymorphism (SSCP) performed for mutation screening of FBN1 gene (n = 50 cases+ 50 age/sex-matched normal; total: 100). Samples with a deviated pattern of bands in SSCP were sequenced to detect the type of variation. Computed tomography (CT) scans of 100 patients (15-45 years old) compared with an equal number of age/sex-matched controls (21.9 ± 8.2 years). Joint parameters studied: sagittal joint inclination (SI), craniocervical tilt (CCT), coronal joint inclination (CI). RESULTS Thirty-nine samples (78%) showed sequence variants. Exon 25, 26, 27, and 28 showed variable patterns of DNA bands in SSCP, which on sequencing gives various types of DNA sequence variations in intronic region of the FBN1 gene in 14%, 14%, 6%, and 44% respectively. CT radiology:SI and CCT correlated with both BI and AAD (p < 0.01). The mean SI value in controls: 83.35° ± 8.65°, and in patients with BI and AAD:129° ± 24.05°. Mean CCT in controls: 60.2° ± 9.2°, and in patients with BI and AAD: 86.0° ± 18.1°. Mean CI in controls:110.3° ± 4.23°, and in cases: 125.15° ± 16.4°. CONCLUSION The study showed mutations in FBN1 gene (reported in Marfan syndrome). There is also an alteration of joint morphology, correlating with AAD and BI severity. Hence, we propose a double-hit hypothesis: the presence of weak ligaments (due to FB1 gene alterations) and abnormal joint morphology may contribute to AAD and BI.

Chiari malformation type I (CMI) cases are frequently associated with basilar invagination (BI), which complicates the understanding of the pathology of CMI. We specifically evaluated the morphometric and volumetric alterations in the bony structures of CMI patients without BI.Fifty adult CMI patients without BI treated at our institution from January 2015 to December 2019 were retrospectively studied. The morphometric and volumetric characteristics of the posterior cranial fossa (PCF) were analyzed using thin-slice computed tomography images.Compared with the controls, the clivus length (P0.001), supraoccipital length (P0.001), Klaus height index (P0.001), axial length (P0.001), clivo-axial angle (P0.001), tentorial angle (P0.05), and bony PCF volume (P0.001) of the CMI-only group were significantly smaller, and the distance between the Chamberlain line and the dens axis (P0.001), clivus angle (P0.001), and basal angle (P0.001) of the CMI-only group were significantly larger, while the distance between the McRae line and the dens axis, McRae line, anteroposterior diameter of the PCF, occipital angle, occipital canal angle, and tentorial Twining line angle showed no significant difference between the 2 groups.Hypoplasia of the clivus and occipital bone were confirmed in CMI patients without BI, thus providing further evidence for the notion that CMI is secondary to the underdevelopment of the PCF.

Syringomyelic affliction of spinal cord is usually seen in association with variety of craniovertebral junction anomalies i.e. Chiari malformations, basilar invagination/impression, atlantoaxial instability etc. The natural history is not very clearly understood and a majority of patient present with slowly progressive neurological deficit followed by sudden rapid deterioration. At present, there is a general consensus to offer surgical decompression in all patients diagnosed with Chiari I malformation with Syrinx irrespective of their symptoms in order to prevent delayed neurological worsening. Few authors have reported spontaneous resolution of syrinx with persistent tonsillar herniation without operative treatment. We report one such patient and propose anterior spinal cord fissuring as a plausible cause of spontaneous drainage of syrinx. We also propose an idea to keep such patients with anterior spinal cord fissure seen in index scans to be followed up conservatively closely instead of upfront Chiari decompression.

Objective To examine the morphological characteristics of the bone structure in the posterior cranial fossa in adult patients with Chiari malformation type Ⅰ (CMⅠ) without basilar invagination. Methods Thirty-eight adult patients with CMⅠ without basilar invagination treated in our department between January, 2018 and June, 2020 were enrolled in this study as the observation group, and 38 gender- and age-matched healthy adults served as the control group. The differences in the linear and angular variables in the posterior cranial fossa were analyzed between the 2 groups based on thin-slice CT data. Results Compared with the control subjects, the patients with CMⅠ showed significantly decreased clivus length (P < 0.001), supra-occipital length (P < 0.01), occipital length (P < 0.01), Klaus height index (P < 0.001), posterior compressive value (P < 0.01), tentorial angle (P < 0.05) and sagittal area of the bony posterior cranial fossa (P < 0.001) and significantly increased odontoid compressive value (P < 0.01), odontoid and soft tissue compressive value (P < 0.01), anterior compressive value (P < 0.01) and basal angle (P < 0.01). Conclusion In adult patients with CMⅠ patients but without basilar invagination, the clivus and occipital bone are shortened and elevated with co-existing ventral cervicomedullary compression by the posterior margin of the odontoid process.

Craniovertebral junction (CVJ) deformity is a challenging pathology that can result in progressive deformity, myelopathy, severe neck pain, and functional disability, such as difficulty swallowing. Surgical management of CVJ deformity is complex for anatomical reasons; given the discreet relationships involved in the surrounding neurovascular structures and intricate biochemical issues, access to this region is relatively difficult. Evaluation of the reducibility, CVJ alignment, and direction of the mechanical compression may determine surgical strategy. If CVJ deformity is reducible, posterior in situ fixation may be a viable solution. If the deformity is rigid and the C1–2 facet is fixed, osteotomy may be necessary to make the C1–2 facet joint reducible. C1–2 facet release with vertical reduction technique could be useful, especially when the C1–2 facet joint is the primary pathology of CVJ kyphotic deformity or basilar invagination. The indications for transoral surgery are becoming as narrow as a treatment for CVJ deformity. In this article, we will discuss CVJ alignment and various strategies for the management of CVJ deformity and possible ways to prevent complications and improve surgical outcomes.

Objective: To evaluated the prevalence and some associated factors of basilar invagination (BI) in a group of Sri Lankan adults. Material and methods: Brain computed tomographic images (CT) of adults admitted to Teaching Hospital Rathnapura, Sri Lanka were studied, excluding subjects with craniofacial syndromes, cerebral or spinal pathologies. The distance between Chamberlain's line (CL) and odontoid process (OP) measured in sagittal CT images (bone window). BI is defined when the OP is 2mm above CL. Results: The study group (n=135; male=67; female=68) was in 20-97 years age range (mean-56±18 years). BI was present in 11.8% (n=16), of which the mean position of OP was 2.33±1.06 cm above CL (range=0.6-4.7 mm). In 13.4%, OP was at the same level as CL. When BI is absent, the mean position of OP was 2.1±1.9 cm below CL. The OP was below CL in 86.6% (n=58) of males and 75% (n=51) of females demonstrating no significant (X2=2.904;p=0.088) gender variation in BI. Internal cranial height (OR=0.823; 95%CI=0.678-0.990; p=0.044) was negatively associated with the incidence of BI. However, age (OR=1.015; 95%CI=0.984-1.047; p=0.341), gender (OR=0.707; 95%CI=0.226-2.218; p=0.553), posterior fossa height (OR=0.912; 95%CI=0.808-1.030; p=0.136), or Klaus' height index (OR=1.099; 95% CI=0.874-1.383; p=0.419) had no significant influence on BI. Conclusion: Current study, for the first time, documents the incidence of BI among asymptomatic Sri Lankans. Since ethnic variation in the incidence of BI is reported, such populationspecific data would be invaluable in diagnosing the asymptomatic BI cohort, which in turn, will facilitate to prevent permanent disability and lifethreatening emergencies.

Retrospective study. Congenital craniovertebral (CV) anomalies include a wide variety of conditions involving basilar invagination (BI), atlantoaxial dislocation (AAD), bony congenital anomalies and Chiari malformation. The management of these disorders is more surgeon dependent rather than based on clear guidelines. This study aims to provide a step-by-step algorithmic approach to the management of congenital CV anomalies to achieve good CV alignment, neural recovery and long lasting stability. The study retrospectively analyses 71 patients of congenital CV anomalies treated by our algorithmic approach. Clinical assessment was done with the help of Nurick’s grading pre- and post-operatively. Radiological outcome was assessed by plain radiographs, and computed tomographic scan was done at 12-month follow-up. Mean age at presentation was 17.9 years (6–41 years). Mean Nurick score pre-operatively was 3.8 which was reduced to 1.3 at a mean follow-up of 13.6 months. Sixty-one patients had type I BI, 6 had type II BI, and 4 patients had os odontoideum. Most common symptom at presentation was weakness in limbs, neck pain and difficulty in walking. Patients of isolated AAD with os odontoideum required posterior atlantoaxial fixation and fusion only. Thirty-two patients of type I BI and 4 patients of type II BI required anterior release procedures prior to occipitocervical instrumentation. Bony fusion was achieved in 96% (68) cases with the help of autologous bone grafting. Three patients of occipitocervical fusion developed pseudoarthrosis. Our retrospective analysis demonstrates that the algorithm is effective in ensuring long lasting results in all types congenital CV anomalies.

Atlanto-occipital non-segmentation failure of segmentation between the fourth occipital sclerotome and the first cervical sclerotome results in atlanto-occipital non-segmentation/ assimilation, also known as occipitalization of the atlas.1The incidence of occipitalisation has been reported to be between 0.08% to 3% of the general population, affecting males and females equally.2 A cartilaginous cleft and an open synchondrosis between the osseous posterior arches of the atlas is a normal finding in children up to four years of age; therefore, a true defect in the posterior arch was diagnosed only in patients who were more than four years old.3 Atlanto-occipital fusion reduces the foramen magnum dimension leading to neurological complications due to compression of spinal cord.4 The slow development of the fibrosis was the source of gradual spinal-cord compression with increasing symptoms.5 Fusion of atlanto-occipital joints can also result in restricted neck movement.6 Basilar invagination is an abnormality at the craniocervical junction (CVJ) either congenital or degenerative, where the odontoid tip is inside the foramen magnum with or without neurological symptoms.7

The occipital bone is often involved in the surgical treatment of basilar invagination (BI). However, the anatomy of the occipital bone associated with BI patients has yet to be investigated.To present a morphological map of the occipital bone in BI patients and help guide screw placement for occipitocervical fusion.A retrospective case-control study.Radiological measurements of the occipital bone were performed on computed tomography images based on a matrix of 99 points centered around the external occipital protuberance (EOP) in a cohort of 50 BI patients and 50 cases with no head and cervical disease. The comparison between the BI group and the control group was assessed using Student t analysis and p.05 was considered statistically significant.All thicknesses measured from points of the matrix in the BI group were thinner than those in the control group (p.05). The maximum thicknesses in both groups were located at the center of the EOP, which were 15.11±2.84 mm in the BI group and 17.56±3.03 mm in the control group, respectively. Additionally, thickness decreased with the distance away from the center of EOP.The occipital bone in BI patients is thinner than that in the general population. A limited safe zone in BI patients is available for surgeons to place screws, which may need to be fully evaluated before operation.

Objective To investigate the incidence of cervical anomalies (CA), including cervical intraspinal neural axis abnormalities (CIINAA) and/or cervical osseous abnormalities (COA), and the clinical relevance in severe spinal deformities (SSD) at a single center. Methods A retrospective study of SSD admitted for spinal surgery from January 2003 to January 2015 was conducted at a single center. Inclusion criteria patients who present with coronal Cobb over 90° (and/or sagittal cobb ≥90°); and patients with complete imaging and clinical data preoperatively. Exclusion criteria ankylosing spondylitis, adult onset scoliosis, scoliosis secondary to bone destruction. There were 108 SSD patients who fulfilled the criteria in this research (41 males and 67 females). The mean age of the patients was 18.1 ± 2.7 years (range, 10-45 years). The clinical and radiological data of these patients were reviewed to identify CA and to analyze the relationship between clinical and radiographic characteristics in the population of SSD. Results The major curves of scoliosis and segmental kyphosis were 109.1° ± 24.7° and 91.2° ± 29.1°. Cervical abnormalities were detected in 56 patients (51.85%) with 9 different CA, including 28 patients (25.9%) with 6 different COA, 21 patients (19.4%) with 3 different CIINAA, and 7 patients (6.5%) with a combination of COA and cervical intraspinal neural axis abnormalities (CINAA). Basilar invagination and Klippel-Feil syndrome were the most frequent COA. Syringomyelia was the most frequent CINAA. SSD with COA in upper vertebral levels (UVL) had a higher incidence of CINAA than those in subaxial vertebral levels (SVL) (P = 0.024) and SSD with multiple COA (mCOA) in UVL had a higher incidence of CINAA than those with single COA (sCOA) (P = 0.029). In the present study, 83.9% of the SSD with CA were asymptomatic. Conclusion The incidence of CA in SSD was 51.85%, with most presenting with intact neurologic status. As the diversity of COA increased, we found a higher incidence of CINAA, especially in UVL.

Introduction Recently, a novel hypothesis has been proposed concerning the origin of craniovertebral junction (CVJ) abnormalities. Commonly found in patients with these entities, atlantoaxial instability has been suspected to cause both Chiari malformation type I and basilar invagination, which renders the tried and tested surgical decompression strategy ineffective. In turn, C1-2 fusion is proposed as a single solution for all CVJ abnormalities, and a revised definition of atlantoaxial instability sees patients both with and without radiographic evidence of instability undergo fusion, instead relying on the intraoperative assessment of the atlantoaxial joints to confirm instability. Methods The authors conducted a comprehensive narrative review of literature and evidence covering this recently emerged hypothesis. The proposed pathomechanisms are discussed and contextualized with published literature. Conclusion The existing evidence is evaluated for supporting or opposing sole posterior C1-2 fusion in patients with CVJ abnormalities and compared with reported outcomes for conventional surgical strategies such as posterior fossa decompression, occipitocervical fusion, and anterior decompression. At present, there is insufficient evidence supporting the hypothesis of atlantoaxial instability being the common progenitor for CVJ abnormalities. Abolishing tried and tested surgical procedures in favor of a single universal approach would thus be unwarranted.

Objective To analyze the association between basilar invagination (BI) and stenosis in the hypoglossal canal (HC). Methods A case-control study with magnetic resonance images (MRIs) of the head from a local database was performed. The study used MRIs of 31 patients with BI (type B) and 36 controls, both groups over 18 years of age and without sex distinction. The internal (ID) and external (ED) diameters of the HC were measured on the coronal plane using the Osirix in its free version 3.9.2 (Mac-Apple platform). We used the Kolmogorov-Smirnov test (with Lilliefors adjustment) to evaluate the normality of the variables, the Levine test to verify the homogeneity of the variances, and Student's t test to verify differences between groups. All analyses were within the 95% confidence interval. Results Control group presented right and left ED values of 4.7 ± 0.8 mm and 4.6 ± 0.9 mm, respectively, while the right and left ID showed 4.4 ± 0.9 mm and 4.3 ± 0.8 mm, respectively. The group with BI showed right and left ED values of 3.3 ± 0.9 mm and 3.1 ± 0.9 mm, and the right and left ID had values of 2.8 ± 0.7 mm and 2.7 ± 0.7 mm, respectively. Both ED and ID were smaller in the group with BI (P Conclusions Patients with BI of type B presented the narrowing of HC when compared with control participants.

Background Lumbar puncture is a common procedure that can be safely performed in most patients. Certain populations may have increased risk for complications following lumbar puncture, but the significance of basilar invagination is often underappreciated. Case Description A 45-year-old woman with basilar invagination received multiple lumbar punctures in the workup of acute meningitis. Preprocedural computed tomography was obtained. Following lumbar puncture, the patient developed locked-in syndrome. Magnetic resonance imaging obtained several days later demonstrated severe compression and infarction of the medulla and inferior cerebellum by the odontoid process and ectopic cerebellar tonsils. The patient was transferred but at this point, surgical decompression was not possible. She did not regain significant neurologic function. Conclusions Basilar invagination is a risk factor for devastating neurologic complications following lumbar puncture. Awareness of this complication and prompt recognition of its occurrence may prevent future morbidity of lumbar puncture in patients with basilar invagination.

To evaluate the reliability and validity of the multi-positional magnetic resonance imaging in measuring occipitocervical parameters using the standard cervical dynamic radiographs as a reference. Patients were included if they underwent both dynamic radiograph and cervical multi-positional MRI within a 2-week interval from January 2013 to December 2016. Twelve occipitocervical parameters were measured on both image modalities in all positions (neutral, flexion and extension): Posterior Atlanto-Dental Interval, Anterior Atlanto-Dental Interval (AADI), Dens-to-McRae distance, Dens-to-McGregor distance, Occipito-atlantal Cobb angle (C01 angle), Occipito-axis Cobb angle (C02 Cobb angle), Atlas-axis Cobb angle (C12 angle), Redlund-Johnell, Modified Ranawat, Clivus canal angle, Occiput inclination, and Occiput cervical distance. Pearson correlation and linear regression analysis were used to evaluate the correlation of both modalities for each parameter. A p value of 0.4) for Modified Ranawat, Clivus canal angle, C02 Cobb angle and C02 distance in all neck position. The intra-class correlation (ICC) of intra- and inter-observer showed good to excellent reliability, and ICCs were 0.67–0.98. Multi-positional MRI can be a reliable imaging option for diagnosis of occipitocervical instability or basilar invagination compared to standard dynamic radiographs.

Objective The recently described C1-C2 fixation without foramen magnum decompression (FMD) for the management of Chiari malformations (CMs) has sparked a controversy. C1-C2 fixation has been reported to be more effective than traditional FMD. However, the results after such a procedure have not been as well validated. We assessed the efficacy of C1-C2 distraction and fusion without FMD in patients with CM and without demonstrable atlantoaxial instability. Methods A total of 40 patients with CM had undergone C1-C2 distraction and fusion without FMD. The preoperative and follow-up clinicoradiological data were prospectively compared using the Klekamp neurologic score, visual analog scale, pBC2 index (ventral brainstem compression), and Vaquero index (syringomyelia). Results Of the 40 patients, 28 (70%) showed improvement in their neurological score and visual analog scale, 8 remained in same status, 3 showed deterioration, and 1 died during the follow-up period. The clinical improvement did not correlate with the severity of ventral cervicomedullary compression or the presence of osseous deformities (assimilated C1 arch, platybasia and basilar invagination) despite the reduction in the mean pBC2 index (7.9 vs. 5.9). The syringomyelia had decreased in 51.7%, with a reduction in the Vaquero index at follow-up (0.48 vs. 0.38). Conclusions The overall results after C1-C2 distraction and fusion for CM without instability were not exceptionally better and appeared to be similar to the outcomes reported with FMD. The neurological improvement seen in some patients had possibly resulted from indirect ventral decompression (due to distraction of C1-C2) rather than the stabilization itself. The presence of bony anomalies such as an assimilated C1 arch, platybasia, basilar invagination, and ventral brainstem compression did not significantly influence the outcomes.

This is a retrospective study.The objective of this study was (1) to measure the occipito-C2 angle (OC2A) and the posterior occipitocervical angle (POCA) in a normal population, and (2) to observe the effects of OC2A and POCA selection on postoperative clinical efficacy and lower cervical curvature after occipitocervical fusion (OCF) in patients with basilar invagination (BI) and atlantoaxial fracture and dislocation (AAFD).OC2A has received special attention with respect to the clinical efficacy during OCF. However, none of studies have focused on the relationship between OC2A and POCA and have assessed their impact on clinical outcomes in patients with different occipiocervical diseases.One hundred fifty healthy subjects without any cervical disease (healthy group) were randomly selected based on sex and age. Three spine surgeons measured the OC2A and POCA in the healthy group and averaged the values. Forty-two patients with BI (BI group) and 32 patients with AAFD (AAFD group) who underwent OCF between January 2012 and January 2017 were reviewed. OC2A, POCA, and cervical spinal angle (CSA) were measured preoperatively, postoperatively immediately after surgery and ambulation, and at the final follow-up visit. The preoperative and final follow-up visual analog scale (VAS), Japanese Orthopaedic Association score (JOA), neck disability index (NDI), and the change of CSA from postoperatively immediately after surgery and ambulation to the final follow-up (dCSA) were recorded.The values of OC2A and POCA were 14.5±3.7 and 108.2±8.1 degrees in the healthy group, respectively, and the respective 95% confidence intervals were 7.2-21.8 and 92.3-124.0 degrees as the normal range. There was a negative correlation between OC2A and POCA (r=-0.386, P0.001). The preoperative value of OC2A (5.6±4.3 degrees) in BI group was smaller than that in the healthy group (P0.05); however, the preoperative value of POCA (123.0±10.4 degrees) in the BI group was larger than that in the healthy group (P0.05). There was no significantly different of OC2A and POCA between the healthy group and the AAFD group before the operation (P0.05). The preoperative value of CSA (25.7±9.5 degrees) in the BI group was larger than that in the AAFD group (16.5±5.1 degrees) (P0.05). In the BI group, 26 patients had ideal OC2A and POCA (both within 95% confidence interval of the healthy group) postoperatively immediately after surgery and ambulation as a subgroup of the ideal angle group. In the remaining patients with BI (nonideal angle group), VAS, JOA, and NDI at the final follow-up were significantly better than those in the ideal angle group (P0.05). The ideal angle group showed statistically greater dCSA than the nonideal angle group of the BI group (P0.05). On the contrary, in the AAFD group, the NDI in the ideal angle group (20 patients) was better than that in the nonideal angle group at the final follow-up, and the ideal angle group had a smaller dCSA compared with the nonideal angle group (P0.05).The biomechanical balance of occipitocervical region in patients with occipitocervical diseases with different pathogenesis is different. On the basis of the different types of occipitocervical diseases, an appropriate range of OC2A and POCA should be selected by the surgeon during OCF, which can further improve the clinical efficacy and reduce the loss of the lower cervical curvature after surgery.

Complex Chiari malformation (CCM) is a spectrum of congenital bony and soft tissue abnormalities, which includes Chiari 1.5 malformation, medullary kinking, retroflexed odontoid, abnormal clival-cervical angle (CXA), occipitalization of the atlas, basilar invagination, syringomyelia, and scoliosis. CCM usually manifests in the pediatric age group and is a challenging entity to treat. It requires detailed evaluation of craniometric indices to decide the appropriate surgical management. Patients with maximum perpendicular distance of dens to the line from the basion to the inferoposterior part of the C2 body (pBC2 line) of more than 9 mm and CXA

Background The majority of the abnormalities and diseases that affect the craniovertebral junction (CVJ) have already been reported, and therefore it is exceedingly rare to identify new pathology that affects the CVJ. Immunoglobulin G4–related disease (IgG4-RD) is an immune mediated process treated with immunosuppressive medications. To our knowledge, this is the first reported case of IgG4-RD affecting the CVJ. Case Description The authors report the case of a woman aged 71 years with IgG4-RD of the CVJ. She presented with intractable left occipital pain and limited flexion, extension, and rotation of the neck. Computed tomography and magnetic resonance imaging revealed a lytic enhancing lesion of the left occipital condyle, left C1 lateral mass, and left C1 anterior arch resulting in cranial settling, basilar invagination, and CVJ instability. An open biopsy, subtotal resection, and occiput to C2 fusion was performed. Pathology revealed IgG4-RD. The patient was subsequently placed on rituximab immunotherapy with complete resolution of enhancement on magnetic resonance imaging and bone growth at the previous site of the lytic IgG4-RD lesion. Conclusions To our knowledge, this case describes the first case of IgG4-RD affecting the CVJ, which mimicked a tumor-like process. When IgG4-RD affects the CVJ, stability must be accounted for, especially in the cases of osteolytic destruction. The combination of medical therapy to target the underlying inflammatory process and surgery to provide structural stability was successful.

We sought to identify predictors of basilar invagination (BI) prognosis and compare diagnostic properties between logistic modeling and machine learning methods.We conducted a single-center retrospective study. Patients at our hospital who met the inclusion and exclusion criteria were identified between August 2015 and August 2020 for inclusion. Candidate predictors, such as demographics, clinical scores, radiographic parameters, and outcome, were included. The primary outcome was the prognosis evaluated by the change in patient-reported Japanese orthopaedic association (PRO-JOA) score. Conventional logistic regression models and machine learning algorithms were implemented. Models were compared, considering the area under the curve (AUC), sensitivity, specificity, positive and negative predictive values, and calibration curve.Overall, the machine learning algorithms and traditional logistic regression models performed similarly. The postoperative cervicomedullary angle, head-neck flexion angle (HNFA), atlantodental interval, postoperative clivo-axial angle, age, postoperative clivus slope, postoperative cranial incidence, weight, postoperative HNFA, and postoperative Boogaard's angle (BoA) were identified as important predictors for BI prognosis. Among the surveyed radiographic parameters, postoperative BoA was the most important predictor of BI prognosis. In the validation dataset, the bagged trees model performed best (AUC, 0.90).Through machine learning, we have demonstrated predictors of BI prognosis. Machine learning methods did not provide too many advantages over logistic regression in predicting BI prognosis but remain promising.

Background Context: Inflammatory arthritis of the cervical spine is common and begins early after the onset of rheumatoid arthritis. Atlantoaxial instability is the most common pattern followed by cranial settling or basilar invagination, with subaxial subluxation being least common. Vertical migration of the odontoid (basilar invagination) poses an increased risk of sudden death from compression of the brain stem. A combination of transoral decompression and posterior occipitocervical fusion has been described, although a single posterior approach stabilization may suffice and avoid the associated comorbidities with an anterior/posterior surgery in a high-risk rheumatoid patient. Purpose: To report a case of odontoid resorption and cervicomedullary angle improvement after occipitocervical fusion. Study Design: A retrospective case report. Methods: Radiographic analysis. Results: After posterior occipitocervical fusion alone for basilar invagination there was a reduction of cervicomedullary angle to 127 degrees at 3 years follow up. This was improved from an initial 115 degrees through odontoid remodeling. Conclusions: Basilar invagination treated with posterior alone occipitocervical stabilization may suffice in providing stability and long term decompression of the cervicomedullary junction through resorption and remodeling of the odontoid. This case study supports the viability of avoiding a transoral resection for an irreducible severely migrated odontoid.

Purpose Occipitocervical fusion is necessary for many pathologies of the craniocervical junction. The anatomy of the region is unique, and fusion can cause significant morbidity. This retrospective review aims to investigate the complication rates and outcomes of occipitocervical fixation. Material and methods This is a retrospective review of 128 patients with occipitocervical fixation operated between 1994 and 2020. The average follow-up is 63 months. Results The indications of occipitocervical fixation were basilar invagination (53 patients; 41.4%), trauma (25 patients; 19.5%), tumor (23 patients; 18%), instability due to rheumatoid arthritis (13 patients; 10.2%), cervical deformity (7 patients; 5.5%) and os odontoideum (7 patients; 5.5%). There were six early postoperative (1st month) deaths. We observed complications in 67 patients (52%). Most common complication was implant-related (32%), followed by wound problems (23.4%), systemic and other complications (11.7%), neurologic complications (6.2%). Implants are removed in 31 patients (24%) for different reasons: deep wound infection (7), local pain and restriction of head movements (21), respiratory distress and swallowing problems (2), screw fracture and local pain (1). Conclusions Occipitocervical fixation has quite large number of complications and significantly restricts head movements. With the advent of our biomechanical concepts, indications should be limited, and shorter cervical fixations should be preferred.

Marfan syndrome is a spectrum of disorders caused by a genetic defect involving connective tissue and is heritable by the autosomal dominant mode of inheritance. Atlantooccipital assimilation is a partial or complete fusion of the atlas and the occiput base congenitally. Although primarily asymptomatic, some patients with atlantooccipital assimilation may present with neurological issues, including myelopathy. Here, we are discussing a case of an 18-year-old male who presented with bilateral paraesthesia, tingling and neck pain which, upon investigations, turned out to be a case of atlantooccipital assimilation along with basilar invagination with spinal cord compression. The patient also had marfanoid features like tall stature, reduced upper to lower segment ratio, and increased arm span to height with positive wrist and thumb signs. As myelopathy had already developed, the patient was treated surgically rather than with medical management with a favorable outcome.

The skull base is a critical structure in the craniofacial region, supporting the brain and vital facial structures in addition to serving as a passageway for important structures entering and exiting the cranial cavity. This paper will review and highlight some of the embryology, developmental anatomy, including ossification, and related abnormalities of the anterior, central and posterior skull base using illustrative cases and tables. Pathologies such as dermoids/epidermoids, cephaloceles, nasal gliomas, glioneuronal heterotopias, various notochordal remnants, persistent craniopharyngeal canal, teratomas, platybasia, basilar invagination, clival anomalies and Chiari malformations will be discussed. Developmental pearls and pitfalls will also be highlighted.