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Study Design: Retrospective radiographic analysis., Objectives: Evaluation of the anatomic features of the craniovertebral junction in patients with occipitalization with and without atlantoaxial dislocation (AAD)., Summary of Background Data: Atlas occipitalization is a common feature of congenital AAD and usually requires surgical intervention. However, not all instances of occipitalization necessarily lead to AAD. No study has specifically examined and compared the craniovertebral bony morphology in occipitalization with, and without, AAD., Materials and Method: We reviewed computed tomography (CT) scans of 2500 adult outpatients. Occipitalization cases without AAD (ON) were selected. Meanwhile, a series of 20 inpatient occipitalization cases with AAD (OD) were obtained in parallel. Another 20 control cases without occipitalization were also included. Multi-directional reconstructed CT images of all cases were analyzed., Results: A total of 18 adults with ON were found in all 2500 outpatients (0.7%). Both anterior height and posterior height of C1 lateral mass in the control group were significantly larger than those in both the ON and OD groups, whereas posterior height in the OD group was significantly less than that in the ON group. Three morphologic types of the occipitalized atlas posterior arch were identified: Type I, bilateral sides were unfused with opisthion; Type II, unilateral side was unfused with opisthion, whereas the other side was fused; and Type III, bilateral sides were fused with opisthion. In the ON group, three cases were type I (17%), six cases were type II (33%), and nine cases were type III (50%). In the OD group, all 20 cases were type III (100%)., Conclusions: Atlas occipitalization with, and without, AAD results from a distinctly different bony morphology at the craniovertebral junction. The novel classification system based on reconstructed CT images may be useful in prognosticating AAD in the setting of atlas occipitalization., Competing Interests: The authors report no conflicts of interest., (Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.)

Study Design: Retrospective case analyses., Objective: The aim of this study was to investigate the incidence and characteristics of associated upper cervical spine injuries in 15 survival cases of traumatic atlanto-occipital dislocation (AOD)., Summary of Background Data: Traumatic AOD is a rare and generally fatal injury. Information regarding associated upper cervical spine injuries that may affect treatment methods, outcomes, and prognosis is limited., Methods: Fifteen patients (11 patients with posterior-type AOD and four patients with vertical-type AOD) who survived traumatic AOD were included in this study. Plain radiographs, computed tomography, magnetic resonance imaging, and medical records were reviewed. The incidence and characteristics of associated upper and lower cervical spine and thoracolumbar spine injuries and brain injuries were evaluated., Results: Thirteen patients with traumatic AOD (11 patients with posterior-type AOD and two patients with vertical-type AOD) showed associated upper cervical spine injuries; the overall incidence was 87% (100% in posterior-type AOD and 50% in vertical-type AOD). In posterior-type AOD, eight (72.7%) patients had C1 fractures (four patients had three-part fracture, three patients had two-part fracture, and one patient had four-part fracture), four (36.4%) patients had C1 lateral mass fractures, two (18.2%) patients had transverse atlantal ligament injuries. In vertical-type AOD, two (50%) patients had C1-C2 vertical subluxation with C1 anterior arch horizontal and sagittal split fractures. In posterior-type AOD, two (18%) patients had lower cervical spine injuries and one (9%) patient had brain injury. In vertical-type AOD, one (25%) patient had thoracic spine injury, and three (75%) patients had brain injuries additionally., Conclusion: Survival cases with traumatic AOD showed a high incidence of associated upper cervical spine injuries and brain injuries. High index of suspicion and careful radiologic examination are needed to investigate the presence of associated upper cervical spine injuries and brain injuries in traumatic AOD, which affects treatment, outcome, and prognosis., Level of Evidence: 4.

Study Design: We investigate on the surgical reliability of nasal palatine line for the transnasal approach and introduce a conceptually analogue radiological line as a reliable predictor of the maximal superior extension of the transoral approach. We have also compared radiological and surgical lines to find possible radiological references points to predict preoperatively the maximal extent of superior dissection for the transoral approach., Objective: After comparing the surgical exposition angle and the working channel volume of both the approaches in our previous article, now we compare the radiological (theoretical) with the "surgical" (effective) Nasopalatine line and the latter with the recently introduced Nasal Axial Line. We conceived a radiological line with a similar significance for the transoral approach and we called it Mandibulopalatine line; then we compared the radiological with the "surgical" one., Summary of Background Data: Endoscopy represents both an alternative and a useful complement to the standard microsurgical approach to the anterior craniovertebral junction (CVJ). Both the surgical routes have a limitation caused by the hard palate., Methods: Ten fresh nonperfused cadavers were studied. Transnasal and transoral linear and angled exposure of the CVJ were evaluated by means of X-ray and CT scan in the sagittal plane., Results: The angular difference between the radiological and surgical transoral endoscopic lines was significantly smaller compared with the difference between the radiological and surgical transnasal lines. Finally we found how to calculate preoperatively the "surgical" (effective) Mandibulopalatine line by a simple lateral preoperative radiological study of the CVJ., Conclusion: Naso-axial line is confirmed to be a reliable preoperative predictor of the maximal extent of inferior dissection for transnasal approach. Surgical Palatine Inferior dental Arch line will draw the maximal extent of superior dissection for the transoral approach with simple lateral head X-ray examination by open mouth., Level of Evidence: 3.

Study Design: A case report., Objective: To describe a unique craniocervical junction anomaly and its implications both on mobility and stability of the skull base., Summary of Background Data: Congenital variations in the craniocervical junction (CVJ) are rare and frequently symptomless. Mild traumas may commonly rouse symptoms which help to unveil such anomalies through radiological investigations., Methods: A 73-year-old woman developed a monoparesis of the right arm after a mild craniofacial trauma. Neurological examination revealed hyper-reflexia in the upper limbs, confirming the strength impairment in the right one. Radiology showed a post-traumatic bulbo-medullary contusion sustained by a unique and unstable association of the first occipital condyles congenital dislocation ever reported with a rare condylus tertius. The patient underwent posterior decompression and occipitocervical screw-rod fixation and fusion. Clinico-radiological follow-up highlighted a gradual recovery of the neurologic impairment and the posterior decompression with resolution of the spinal cord contusion., Results: Although apparently stable the hyperostosis and the irregularly shaped condylar surfaces behind the 3-points mechanism of skull base support played a critical role in determining axial instability. The imbalance due to skull-cervical spine malpositioning may consequently trigger a vicious cycle of development of osteophytes leading to spinal cord narrowing with neurologic decline. A surgical strategy providing for posterior decompression and fixation satisfied the need to solve both bulbo-medullary constriction and skull base instability., Conclusion: Clinical evidences about CVJ anomalies are lacking and symptoms, when present, tend to be vague. Although extremely rare clinicians should be aware of CVJ variations by engaging to improve their knowledge of imaging anatomy, embryology, CVJ basic craniometry and anatomic relationships. Studies on developmental control genes may offer future perspectives of early diagnosis and targeted treatments., Level of Evidence: 4.

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

Study Design: Observational and quantitative study with 3-dimensional (3D) computerized tomographic (CT) analysis., Objective: To establish the 3D configuration and morphometric data of obliquity of the lateral atlantoaxial articulations (LAA) in congenital anomaly with occipitalization., Summary of Background Data: Plane radiographs and normal CT scans cannot clearly demonstrate the configuration of LAA as the hindrance of circumambient bony structures. The morphology of anomalous LAA with occipitalization is underreported., Methods: A series of 63 cases with occipitalization and 20 control subjects underwent thin-slice CT scanning. The 3D configuration of LAA were analyzed and categorized based on the degree of olisthy and inclination orientation of the atlantoaxial articular facets (AAF). The obliquity of the AAF was measured in reconstructed sagittal and coronal planes, respectively., Results: Four types of configuration of LAA with occipitalization were found: type I, characterized by slight anteversion of LAA without olisthy of the inferior and superior facets (16% of 126 sides); type II, characterized by partial olisthy of the 2 facets and evident anteversion of LAA (48%); type III, defined by the separation or complete olisthy of the 2 facets (13%); and type IV, wherein the articular facets sloped dorsally (23%). Forty-eight of 49 cases in the former 3 types wherein AAF sloped ventrally had atlantoaxial dislocation (AAD). All type IV cases wherein AAF sloped dorsally had no AAD. In control subjects, LAA had no evident obliquity of anteversion or retroversion., Conclusion: Instability at the C1-C2 junction in congenital anomaly with occipitalization is likely a direct result of the anteversion of LAA and bony malformation of this region, and it aggratates with the increasing obliquity of anteversion of the AAF. Demonstrating 3D morphological changes of LAA may provide a new means to diagnosis instability in congenital anomaly at craniovertebral junction and a basis for rational surgical treatment.

Study Design: Case report., Objective: To report a new surgical technique of the primary cervical osteosarcoma in the atlas., Summary of Background Data: Primary osteosarcoma of the atlas is extremely rare. This is the first report that describes a surgical treatment of the primary osteosarcoma in the atlas. Resection of an osteosarcoma in the atlas is very difficult because of the complex and important anatomic structures that surround it, and secure reconstruction of the atlas is difficult as well., Methods: A 48-year-old man was referred to our institute with a 10-month history of a palpable painful mass on the right posterior neck. His neck mass was diagnosed as chondroblastic osteosarcoma by open bone biopsy. The plain radiograph of the lateral cervical spine revealed the osteoblastic lesion of the vertebra and an extraosseous mass formation from the C1 to C3 vertebrae. Computed tomography of the cervical spine revealed approximately a 7 × 3 × 7 cm-sized extraosseous calcified mass that originated from the right lateral mass of the atlas. The magnetic resonance imaging of the cervical spine did not show any spinal cord compression., Results: The patient underwent excision of this tumor using the direct lateral approach and reconstruction of the lateral mass of the atlas. On gross examination of the mass, there was a reactive thin membrane ("pseudomembrane") between soft tissue and tumor. At 3 months after surgery, the computed tomographic scan showed the solid fusion state of the occipitocervical joint. He rarely complained of any problems except for mild limitation of neck motion., Conclusion: We report a rare case of complete excision of an osteosarcoma of the C1 lateral mass in our patient via a direct lateral and posterior approach to secure additional fixation of occipitocervical joint. We describe our technique for reconstructing the lateral mass of the atlas. This reconstruction technique will also be applicable to other resection surgeries involving the occipitocervical junction.

Study Design: Radiographic analysis using normal patients., Objective: To analyze the relationship between the cervical alignment and the oropharyngeal space., Summary of Background Data: Few clinical studies stress the effect of the occipito-C2 (O-C2) alignment on the oropharyngeal space. A previous study showed dysphagia and/or dyspnea after occipitocervical fusion was caused by oropharyngeal stenosis resulting from O-C2 fixation in a flexed position. Other independent researchers showed that development or improvement of obstructive sleep apnea in rheumatoid arthritis patients was related to the O-C2 alignment. However, there are limited basic data demonstrating the relationship between the O-C2 alignment and the oropharyngeal space., Methods: Plain lateral cervical radiographs in five tested positions--neutral, flexion, extension, protrusion, and retraction--of 40 asymptomatic volunteers were collected. The O-C2 angle, the C2-C6 angle, and the anterior-posterior distance of the narrowest oropharyngeal airway space (nPAS) were measured, and the changes in value from the neutral to the other four positions were calculated for each patient., Results: According to the multiple regression analysis, there was an extremely strong linear correlation of the change in the O-C2 angle with the percentage change in the nPAS. Referring to the multiple regression analysis, a decrease of 10° in the O-C2 angle caused a 37% reduction in the nPAS in the neutral position. In contrast, no significant correlation was found between the change in the C2-C6 angle and the percentage change in the nPAS., Conclusion: Our results show the impact of the O-C2 angle on the oropharyngeal space. This knowledge will be useful for the diagnosis and treatment of the upper cervical lesion combined with the upper airway stenosis, and for the determination of the optimal fixation angle in occipitocervical fusion.

Study Design: A case-series study., Objectives: To measure the 3-dimensional (3D) morphology and kinematics of the craniovertebral junction (CVJ) using a 3D computed tomography (CT) model; to reveal abnormal patterns and the relationships between pathology and kinematics., Summary of Background Data: Evaluations using radiography, 2-dimensional (2D) CT and magnetic resonance imaging have limitations because of the complex 3D structure of the CVJ., Methods: Twenty-four rheumatoid arthritis patients (21 females, 3 males) with cervical involvement underwent CT scanning of the cervical spine from the basilar process of the occipital bone to the first thoracic vertebra in neutral and flexed positions. The 3D morphology of the occipital condyle, atlas, and axis were classified based on the type of deformity observed. Periodontoid lesions (continuous bony lesions between the atlas and the odontoid process) were also noted. The 3D kinematics in the atlanto-occipital and atlantoaxial joints were evaluated using the volume merge method., Results: Deformities in the atlanto-occipital joints appeared more frequently than those in the atlantoaxial joints. The most common instability pattern was flexural rotation during flexion at the CVJ. The direction of translational motions during flexion was posterior in the atlanto-occipital joint and anterior and caudal in the atlantoaxial joint., Conclusion: The results suggest that bilateral occipital condyle deformation, unilateral and bilateral mass collapse, and periodontoid lesions may affect flexion/extension rotational instability in the atlantoaxial joint. In addition, unilateral occipital condyle deformation and atlantoaxial joint stability may affect sagittal translational instability to the posterior side in the atlanto-occipital joint. The noninvasive 3D CT imaging technique employed here would be useful for predicting the prognosis of patients with rheumatoid deformities at the CVJ.

Study Design: Case series., Objective: To analyze factors that contribute to the development of sleep apnea in patients with rheumatoid arthritis (RA) and upper cervical lesions., Summary of Background Data: No large prospective study has analyzed the association between sleep apnea and upper cervical involvement resulting from RA. Furthermore, only 1 report in the literature describes a case of sleep apnea accompanying rheumatoid vertical subluxation of the odontoid process., Methods: The authors analyzed 8 consecutive RA patients with upper cervical lesions who underwent occipitocervical (O-C) fusion. The patients were examined with all-night polysomnography before and after surgery. Patients with apnea-hypopnea index values>or=5 were diagnosed to have sleep apnea. O-C2 angles were calculated from cervical radiographs., Results: All 8 patients were diagnosed as having sleep apnea, and most of their apneic episodes were obstructive in origin. Among the 4 patients with medullary compression, central apneic episodes comprised

Study Design: Radiologic evaluation of computed tomography (CT) scans using screw insertion simulation software., Objective: To investigate the optimal entry point and trajectory of atlantooccipital transarticular screws., Summary of Background Data: To our knowledge, no large series focusing on the placement of atlantooccipital transarticular screws have been published., Methods: We used 1.0-mm sliced CT scans and 3-dimensional screw trajectory software to simulate 4.0-mm screw placement. Four entry points were evaluated. Screw placement success rate, safe range of medial angulation, and screw length using each entry point were determined., Results: CT scans of 126 patients were evaluated, for a total of 252 screws for each entry point. On simulation, the 2 lateral entry points showed significantly higher success rates and safe range of medial angulation than the 2 middle points. The 2 lateral entry points had similar success rates (98.0% for anteriolateral (AL) point and 97.6% for posteriolateral (PL) point). Although the safe range of medial angulation was significantly wider for the AL point (26.1 degrees) than for the PL point (23.7 degrees), the screw lengths were significantly longer for the PL point (32.6 mm) than for the AL point (29.4 mm). For both points, 30 degrees of medial angulation led to highest rate of successful screw placement, but the rate was only 79.4% and 80.2%, respectively., Conclusion: Although there was no significant difference in success rates between AL and PL points, PL is likely the best entry point. Although 30 degrees medial and approximately 5 degrees upward angulation led to the highest rate of successful screw placement, the rate was only around 80%. Given the wide individual variation, we recommend that a preoperative 3-dimensional CT scan be obtained when attempting atlantooccipital transarticular screw fixation.

Study Design: Case report and literature review., Objective: To discuss the diagnosis, limitations, and treatment of combined occipital-cervical and atlantoaxial disassociation with normal neurologic function., Summary of Background Data: Injuries to the craniocervical junction can lead to devastating neurologic deficits. Occipital-cervical disassociation is a well-documented injury pattern that can lead to pain, spinal cord injury, and death. Early diagnosis and treatment can preserve neurologic function. Combined injuries to both the occipital-cervical and atlantoaxial segments are less common and, to date, have only been described with severe neurologic injury., Methods: Retrospective review of a case. Literature review was performed through Medline and Pubmed searches., Results: This is the first case to present a combined occipital-cervical and atlantoaxial disassociation with a neurologically intact patient. Initial physical examination was limited, but early imaging revealed evidence of instability. Early diagnosis and early (< 24) surgical stabilization was performed with no complications and neurologic preservation. One-year follow-up visit revealed normal neurologic examination with neck pain VAS = 2/10 and neck disability index = 6., Conclusion: Combined injuries to the occipital-cervical and atlantoaxial can result in upper cervical instability. Despite previous reports, neurologic preservation remains a possibility in this injury pattern. Limitations in physical examination and radiographic imaging persist, but early diagnosis and surgical stabilization may improve neurologic outcomes.

Study Design: A cross-sectional clinico-radiologic evaluation of occipito-atlantoaxial (OC1C2) region of 2 population groups., Objective: Determine the prevalence of OC1C2 osteoarthritis in porters involved in carrying loads on the head and general male population. Describe its clinico-radiologic manifestations., Summary of the Background Data: In addition to age, head loading is a known cause of degeneration affecting the occipito-cervical region. The impact of head loading in the population aged between third and sixth decade is unknown. Head loading is a common custom in the developing countries., Material and Methods: Study group (n = 107) included randomly selected male porters from railway stations who underwent computed tomography (CT) study of the OC1C2 region, plain radiographs of the cervical spine and detailed clinical examination. Control group (n = 107) included randomly selected male patients undergoing CT scan study for diseases of paranasal sinuses with coincidental screening of OC1C2 region along with clinical assessment. The data were analyzed using SPSS 15 software., Result: Mean age for study group was 32.6 years and controls was 34.6 years (P = 0.156). In the study group, duration of occupational exposure was 10.9 (+/-8.7) years; 81.3% porters being symptomatic with an age of 33.4 (+/-9.6) years. Radiologic prevalence of OC1C2 osteoarthritis in study group was 91.6% and in control group was 6.8%; age of affected individuals was 33.4 (+/-9.3) and 47.9 (+/-8.0) years, respectively. Most common complaint was suboccipital neck pain (69.7%); while the CT finding was decreased joint space with sclerosis and irregularity of the margins (81.3%). No statistically significant association was found between presence of radiologic changes and symptoms. Age, duration of occupational exposure and its relationship with various clinico-radiologic manifestations was studied., Conclusion: This condition has significant prevalence in porters, beginning at an early age. Diagnosis is based on the clinico-radiologic presentation. CT is the investigation of choice. Resultant functional limitations make early identification of this condition imperative.

STUDY DESIGN.: Observational study with 3-dimensional computed tomography angiography analysis. OBJECTIVE.: To examine the course of the vertebral artery (VA) at the craniovertebral junction (CVJ) in individuals with occipitalization of the atlas. SUMMARY OF BACKGROUND DATA.: The anatomy of the VA at the CVJ should be completely understood to decrease the risk of iatrogenic injury. Although quantitative anatomic studies have focused on the normal VA, the anomalous VA with occipitalization of the atlas has not been fully explored. METHODS.: A consecutive series of 36 cases with occipitalization of the atlas underwent 3-dimensional computed tomography angiography. Seventy-two vertebral arteries were analyzed. In this setting, the safety of placing lateral mass screws (LMS) was studied. RESULTS.: Four different pathways of the VA at the CVJ with occipitalization of the atlas were found. Type I, wherein the VA enters the spinal canal below the C1 posterior arch, and the course of the VA is below the occipitalized C1 lateral mass (8.3% of 72 vertebral arteries); Type II, the VA enters the spinal canal below the C1 posterior arch, and the course of the VA is on the posterior surface of the occipitalized C1 lateral mass, or makes a curve on it (25%); Type III, wherein the VA ascends externally laterally after leaving the axis transverse foramen, enters an osseous foramen created between the atlas and occipital bone, then into the cranium (61.1%); and Type IV, in which the VA is absent (5.6%). CONCLUSION.: Four types of VA with occipitalization of the atlas are confirmed. Type-I and type-IV VA have relatively low risks for C1 LMS perforation. Type-II and type-III anomalies will probably increase the risk of VA injury during C1 LMS placement. Definite caution should also be taken during the procedure on the contralateral side of a type-IV VA.

Study Design: Biomechanical study using human cadaveric cervical spines., Objective: To evaluate the construct stability of 3 different segmental occipitoatlantoaxial (C0-C1-C2) stabilization techniques., Summary of Background Data: Different C0-C1-C2 stabilization techniques are used for unstable conditions in the upper cervical spine, all with different degrees of risk to the vertebral artery. Techniques with similar stability but less risk to the vertebral artery may be advantageous., Methods: Six human cadaveric cervical spines (C0-C5) (age: 74 +/- 5.0 years) were used. After testing the intact spines, instability was created by transecting the transverse and alar ligaments. The spines were instrumented from the occiput to C2 using 3 different techniques which varied in their attachment to C2. All spines had 6 screws placed into the occiput along with lateral mass screws at C1. The 3 variations used in attachment to C2 were (1) C2 crossing laminar screws, (2) C2 pedicle screws, and (3) C1-C2 transarticular screws. The C1 lateral mass screws were removed before placement of the C1-C2 transarticular screws. Range of motion across C0-C2 was measured for each construct. The data were analyzed using repeated measures ANOVA. The following post hoc comparisons were made: (1) intact spine versus each of the 3 techniques, (2) laminar screw technique versus the pedicle screw technique, and (3) laminar screw technique versus the transarticular screw technique. The level of significance was alpha = 0.01 (after Bonferroni correction for 5 comparisons)., Results: All 3 stabilization techniques significantly decreased range of motion across C0-C2 compared to the intact spine (P < 0.01). There was no statistical difference among the 3 stabilization methods in flexion/extension and axial rotation. In lateral bending, the technique using C2 crossing laminar screws demonstrated a trend toward increased range of motion compared to the other 2 techniques. CT scans in both axial and sagittal views demonstrated greater proximity to the vertebral artery in the pedicle and transarticular screw techniques compared to the crossing laminar screw technique., Conclusion: Occipitoatlantoaxial stabilization techniques using C2 crossing laminar screws, C2 pedicles screws, and C1-C2 transarticular screws offer similar biomechanical stability. Using the C2 crossing laminar screw technique may offer an advantage over the other techniques due to the reduction of the risk to the vertebral artery during C2 screw placement.

Study Design: Reconstructive computed tomography (CT) study of occipito-atlanto and atlantoaxial joints in RA patients., Summary of Background Data: The occipitocervical region is one of the most common sites of rheumatoid arthritis (RA). Although lateral radiography has been used for the diagnosis of atlantoaxial subluxation and vertical subluxation, reconstructive CT imaging of the occipito-atlanto and atlantoaxial joints is more sensitive in detecting morphologic changes in this region. We investigated this region in RA patients, using coronal-view reconstructive CT images, and examined the relationship between the morphology and other radiographic parameters., Methods: The occipitocervical region was examined in 58 female RA patients by reconstructive CT, plain radiography, and MRI. The degree of destructive change on reconstructive CT was compared to that on other radiographic evaluations., Results: Coronal-view reconstructive CT revealed primary destructive changes before detection by lateral radiography, using Redlund-Johnell or Ranawat values. A Redlund-Johnell value less than 34 mm was diagnostic for occipitocervical subluxation in female RA patients., Conclusion: Coronal-view reconstructive CT is useful for the diagnosis of occipitocervical joint subluxation in RA.

Study Design: A case report of the presyrinx state at the craniocervical junction with vanishment of an intramedullary high-signal lesion followed by decompression and fixation., Objective: To report the reversible change of an intramedullary high-signal lesion on T2-weighted MRI as a presyrinx state., Summary of Background Data: The pathology of a T2-weighted high-signal intensity area in the spinal cord has not yet been described in detail. The case presented here showed the vanishment of this lesion after the surgical procedure, which implies that some high-signal intensity lesions might be reversible as a presyrinx state., Methods: A 75-year-old man presented with severe cervical myelopathy. Neurologic findings and observations on various images indicated compression myelopathy due to both a pseudotumor at the craniocervical junction and spondylosis at C3-C4 disc level due to Klippel-Feil syndrome. The most obvious finding was a vast high-signal intensity lesion at the craniocervical junction, which was speculated to be a syringomyelia before surgery., Results: The MRI at 1 month after surgical treatment (occipito-spinal fusion with the decompression by enlargement of foramen magnum) revealed complete vanishment of the vast high intensity lesion at the craniocervical junction, which remained undetected at the 2 years and 8 months follow-up and corresponded with improvement in the clinical symptoms of myelopathy., Conclusion: The vanishment of these signal changes on MRI after surgery was interpreted as a presyrinx state, demonstrating this reversible pathology in the spinal cord.

Study Design: A retrospective clinical study., Objective: To confirm the impact of the O-C2 angle on dyspnea and dysphagia after posterior occipitocervical (O-C) fusion., Summary of Background Data: Dyspnea and dysphagia are complications of posterior O-C fusion with malalignment, and may be prolonged or occasionally serious. However, it is difficult to select a safe alignment during surgery, and no indicators of the appropriate alignment have been available to preclude these complications., Methods: The authors retrospectively reviewed 29 consecutive patients who had undergone O-C or occipitocervicothoracic fusion between 2003 and 2008. Data were analyzed for O-C2 angles on plain radiographs and the axial computed tomographic cross-sectional areas of the oropharynx just cranial to the epiglottis before and after surgery. The patients were grouped according to whether they developed postoperative dyspnea and/or dysphagia (group A) or not (group B)., Results: After surgery, 4 patients complained of dysphagia, and 1 patient had dyspnea and dysphagia, although they had all undergone short O-C fusions. The difference in the O-C2 angle (dOC2A = postoperative O-C2 angle--preoperative O-C2 angle) and the percentage change in the cross-sectional area of the oropharynx (S) before and after surgery (% dS) were linearly correlated. Both dOC2A and % dS were significantly lower in group A than in group B. All patients with dOC2A of less than -10 degrees showed % dS of less than -40%, and developed dyspnea and/or dysphagia after surgery. Conversely, no patients with positive dOC2A developed these complications., Conclusion: The O-C2 angle has considerable impact on dyspnea and/or dysphagia after O-C fusion. The O-C2 angle is easily measured during surgery and can be a practical index with which to avoid postoperative dyspnea and dysphagia.

Study Design: A case report of a patient who survived a traumatic disassociation of both atlanto-occipital and atlantoaxial joints. OBJECTIVE.: To describe a rare case of concurrent atlanto-occipital and atlantoaxial dislocation with a review of the related literature regarding occipitocervical dislocation., Summary of Background Data: Cases of isolated atlanto-occipital or atlantoaxial dislocation have typically resulted in death or devastating neurologic deficit. Survival after the simultaneous dislocation at both joints is extremely rare., Methods: The initial evaluation, subsequent management, and surgical treatment of a 25-year-old male who sustained a concurrent dislocation of the atlantoaxial and atlanto-occipital joints from a motor vehicle collision are reported and the related literature is discussed., Results: The patient was transferred to our hospital after initial stabilization according to Emergency Medical Service criteria and management based on the Advanced Trauma Life Support protocol. A complete (ASIA A) spinal cord injury was diagnosed on admission. Radiographic evaluation revealed dislocations of the atlanto-occipital and atlantoaxial joints. Subsequently, the patient underwent surgical stabilization with instrumented posterior fusion from the occiput to C5. Intraoperatively, traumatic pseudomeningocele was diagnosed and repaired with pericranial autograft. The vital function parameters currently remain stable, but the patient is ventilator-dependent and did not regain motor or sensory function., Conclusion: The rapid response time of emergency medical services and stabilization according to the Advanced Trauma Life Support protocol now lead to the survival of patients with significant deficit from occipitocervical injuries. A high index of suspicion is required to appropriately manage a patient with this devastating injury in order to maximize the chance for survival.

Study Design: We present, to the best of our knowledge, the first reported case of craniovertebral junction tuberculosis with complete quadriplegia in an infant., Objective: To describe report of an unusual case and discuss the difficulties and peculiarities of diagnosis, management, and follow-up of craniovertebral tuberculosis in an infant., Summary of Background Data: Spinal tuberculosis is prevalent in areas where tuberculosis is endemic, and its incidence is on the rise in developed nations with the rising incidence of HIV/AIDS. Although common in children and young adults, spinal tuberculosis is rare in infants. Again, craniovertebral tuberculosis is one of the rarest forms of spinal tuberculosis., Methods: The infant presented to us at the age of 9 months with Grade IV quadriplegia. Among many of the clinical differential diagnoses, craniovertebral tuberculosis was suspected only on MRI and proved after fine needle aspiration cytology demonstrated granulomas. The patient was subjected to transoral debridement, immobilized with help of a pair of pillows by either side of the head and multidrug antitubercular treatment was started, which continued for duration of 12 months., Results: At the last follow-up of 1 year, the patient had recovered fully and caught up with the milestones suitable for her age., Conclusion: Craniovertebral tuberculosis is difficult to diagnose and treat in infants. A high index of suspicion is essential for a prompt diagnosis and treatment, which is all the more crucial in this age group.

Study Design: Case report of a patient with Pierre Robin sequence who presented with occipitoatlantoaxial instability and congenital thoracic deformity., Objective: As there are lack of similar cases in the literature, we would like to introduce a case of a patient with associated malformations, the consultations that we consider that are obligatory, and our decision-making process. We would also like to demonstrate the follow-up plan and the further key points about either the conservative or the surgical solution of the problem., Summary of Background Data: The occurrences of 2 malformations (Pierre Robin sequence and occipitoatlantoaxial instability) together are very rare. We have found only 1 publication in the related literature about this topic. We consider that this rare appearance is due to the difficulty in diagnosing this problem. There is no clinical evidence that musculoskeletal examinations are indicated in a patient with Pierre Robin sequence, and it is difficult to check for all the possible deformities., Method: As congenital scoliosis appeared only at 6 years of age in the case of this child with Pierre Robin syndrome, we promptly began to investigate for other musculoskeletal defects. We would like to demonstrate the investigation process and emphasize the necessity of conventional and functional radiographs, computed tomography, and magnetic resonance images., Results: We have not found similar cases to refer to, so we made our decision about conservative treatment of the craniocervical instability knowing that we will have to follow up the progression of both the congenital thoracic scoliotic deformity and the occipitoatlantoaxial instability later., Conclusion: To recognize a rare case is a big challenge indeed due to the lack of the investigational protocol, the key points of the decision process, the prognostic classification system, and the progression of the disease. We recommend that one should individualize and follow up the patient frequently.

Study Design: Retrospective case series., Objective: Evaluate the change in lordosis at the occipitocervical junction occurring during growth in skeletally immature children treated with posterior occipitocervical arthrodesis versus patients skeletally mature at arthrodesis., Summary of Background Data: Posterior occipitocervical arthrodesis is often indicated for children who have instability of the upper cervical spine develop. Theoretically, in skeletally immature children, this approach retards the growth of the posterior spinal elements but allows the anterior spinal column to continue to grow with the risk of excessive lordosis of the cervical spine developing., Methods: There were 21 children, younger than 11 years (range 1.9-10.9) at surgery and expected to have normal spinal growth, followed radiographically for an average of 6.3 years (range 2.0-12.4). Postoperative lateral neutral radiographs were compared to those at most recent follow-up to measure the change in occipitocervical angle. These results were then compared to a series of control patients who were skeletally mature at surgery., Results: Average overall change in lordosis at the occipitocervical junction was -4.6 degrees (range -12.8 degrees to +6.5 degrees). Average annualized change was -0.28 degrees per vertebral level per year (range -1.13 degrees to +0.67 degrees). This annualized change in angle was statistically significant compared to the average change of +0.01 degrees (range -0.09 degrees to +0.11 degrees) measured in the control series of patients skeletally mature at surgery (P = 0.01)., Conclusions: Increasing lordosis occurs at the occipitocervical junction following fusion in skeletally immature children. If occipitocervical arthrodesis is indicated in a skeletally immature child, fusion in excessive extension and overtightening of posterior wires should be avoided.

Study Design: Case report of a child with a congenital skeletal anomaly who underwent instrumented surgery at the craniovertebral junction (CVJ)., Objectives: To describe the utility of surgical simulation using three-dimensional full-scale models for preoperative planning., Summary of Background Data: Instrumented fusion of cervical spine with pedicle screws has several advantages compared with conventional sublaminar wiring, such as stronger fixation and reduction of malalignment. However, studies have reported a risk of injury to the vertebral artery (VA) from the insertion of screws. Especially in pediatric patients, the safety of pedicle screw insertion has not been fully established., Methods: A 7-year-old girl with a congenital skeletal anomaly presented with gait disturbance and clumsiness of her right hand. Radiographs showed dysplasia of the C1 posterior arch, leading to compression of the spinal cord posteriorly. Data from three-dimensional computed tomography (CT) angiography showed that the right VA was dominant and was shifted medially at the C2 pedicle. A surgical procedure was scheduled to resect the C1 posterior arch and perform an instrumented occiput-C2 fusion with a system of rod and screws. To evaluate the adaptation of the system to the small and deformed anatomic structure of her CVJ, we produced a three-dimensional full-scale model from CT data and performed a simulation of the scheduled surgery., Results: Simulation of the surgery on the model showed acceptable adaptation of the system. However, the right C2 pedicle screw penetrated the medial wall of the VA foramen. In response to these results, we altered the surgical procedure and performed occiput-C3 fixation with a system of contoured loop and wiring. Although the patient had to use a halo-vest for 2 months, no complication occurred during surgery, and she experienced relief of her myelopathy after surgery., Conclusions: The three-dimensional full-scale model was useful for determining the safety of instrumented posterior occipitocervical fusion for a pediatric patient with a skeletal anomaly.

Study Design: This is a case report of a patient who survived traumatic atlanto-occipital dislocation with atlantoaxial subluxation., Objective: To describe the useful points of 3-dimensional computerized tomography (CT) and magnetic resonance imaging (MRI) for an evaluation of atlanto-occipital dislocation., Summary of Background Data: Atlanto-occipital dislocation is a severe ligamentous injury that usually results in either a fatal outcome or severe neurologic deficit. To our knowledge, no patient who has survived atlanto-occipital dislocation with atlantoaxial subluxation has yet been reported., Methods: Three-dimensional CT was performed to confirm the diagnosis of atlanto-occipital dislocation and precisely evaluate the magnitude of displacement. MRI clearly showed a disruption of the ligamentous structures, which play a role as the primary stabilizers of the cranium on the cervical spine., Results: As soon as the patient's general condition improved, the posterior spinal fusion with internal fixation was performed to maintain the stability of cervical spine. A significant degree of motor function was regained within 2 years after injury., Conclusions: In this case, the diagnosis was accurately confirmed, and the cervical spine was evaluated in detail using both 3-dimensional CT and MRI as a reliable examination for atlanto-occipital dislocation.

Study Design: This study examined the extraosseous and intraosseous anomalies of vertebral arteries in patients who underwent surgery of the craniovertebral junction., Objectives: To describe the usefulness of three-dimensional computed tomography angiography for evaluating vertebral artery anomalies before surgery., Summary of Background Data: Previous studies using catheter angiograms have identified anomalous courses of the vertebral artery at the craniovertebral junction. Studies using computed tomography reconstruction also showed deviation of the vertebral artery groove at the C2 isthmus, demonstrating a risk of vertebral artery injury for C1-C2 transarticular screw placement. These analyses provided us with useful information for identifying anomalies of the vertebral artery, but they could not visualize the artery and its circumferential osseous tissue simultaneously, nor could they analyze the reciprocal anatomy of both tissues., Methods: Thirty-one consecutive patients who submitted to surgery at the craniovertebral junction were evaluated before surgery by three-dimensional computed tomography angiography. Eleven of the patients had congenital osseous anomalies at the craniovertebral junction including os odontoideum and ossiculum terminale. Anomalous vertebral arteries at the extraosseous region were visualized by three-dimensional reconstruction images, and the intraosseous deviation of the vertebral artery at the C2 isthmus was evaluated by multiplanar reconstruction images., Results: Extraosseous and/or intraosseous vertebral artery anomalies were detected in 9 cases. Eight of the 9 cases had osseous anomalies at the craniovertebral junction. Abnormal courses of the vertebral artery at the extraosseous region were detected in 4 cases: 2 had fenestration and 2 had persistent first intersegmental artery. Asymmetry of bilateral vertebral arteries was found in 5 cases: the right was dominant in 3 cases and the left in 2 cases. A high-riding vertebral artery at the C2 isthmus was detected in 5 cases. Based on these findings, we modified our surgical approach and the screw placement; consequently, no vertebral artery injury occurred., Conclusions: In patients having osseous anomalies at the craniovertebral junction, the frequency of vertebral artery anomalies at the extraosseous and intraosseous regions is increased. With preoperative three-dimensional computed tomography angiography, we can precisely identify the anomalous vertebral artery and reduce the risk of intraoperative injury to the vertebral artery, in advance.

Study Design: A case of a child with a traumatic atlanto-occipital dislocation (AOD), with unexpected secondary redislocation in a halo vest is presented. An extensive literature review was performed., Objectives: To show the difficulties in diagnosing AOD, to emphasize its intrinsic instability, and to make recommendations for treatment of this condition., Summary of Background Data: AOD is a rare condition that is difficult to diagnose. Because of the high neurologic morbidity, this injury often results in death. Different diagnostic approaches have been evaluated throughout the literature. Also, there are different opinions on how to treat AOD. There is no large trial that compares conservative treatment with surgery., Methods: A 4-year-old child with a longitudinal distraction of the head is described. Because of his tenuous medical condition, initial treatment was in a halo vest. However, redislocation occurred inside the vest, so surgical stabilization was performed as soon as the patient's condition allowed., Results: To diagnose AOD, different measuring techniques can be applied on a lateral cervical spine radiograph. Using a combination of these tools, the sensitivity of the examination can be increased. There are 3 types of dislocation. Type II, which is a longitudinal distraction, is most unstable. Once confirmed, AOD should be immobilized. This can temporarily be performed with a halo-frame, but our case shows that this does not necessarily provide a stable situation, and early surgical reconstruction should be considered., Conclusions: AOD can be an extremely unstable lesion and is difficult to diagnose. Although initial treatment in a halo vest is recommended, redislocation can occur even in the vest. We recommend urgent surgical stabilization.

Study Design: Blinded comparison of 5 methods to diagnose atlanto-occipital dislocation (AOD) on plain radiographs and computerized tomography (CT) of the cervical spine., Objective: To determine the best method to diagnose AOD., Summary of Background Data: Several methods are proposed for the diagnosis of AOD, including the Power's ratio, X-line method, basion-dens interval, condylar gap, and Harris method. No blinded comparison of the results of these methods has been compared to patient outcome, and there is no information available regarding the accuracy of these methods applied to CT scans., Methods: Plain lateral radiographs and CTs of the cervical spine were reviewed in 104 patients, including 6 with AOD. Images underwent a blinded review by a board certified neurosurgeon (D.K.R.), orthopedist (P.A.A.), radiologist (J.C.), and emergency physician (D.B.B.). Each diagnostic method for AOD was applied for determination of sensitivity, specificity, and positive and negative predictive values. The ability to identify relevant anatomic landmarks was also tabulated., Results: Average values for sensitivities, specificities, positive and negative predictive values for each method applied to plain radiographs are: 0.4625-1.0, 0.8933-0.9725, 0.2775-0.45, and 0.975-1.0, respectively. These values for each method applied to CT scans are: 0.7075-1.0, 0.8725-0.9775, 0.3175-1, and 0.98-1.0, respectively. Identification of relevant anatomic landmarks occurred 99.75% of the time when these methods were applied to CT scans compared to 39% to 84% of the time on plain radiographs., Conclusions: Sensitivity, specificity, positive and negative predictive values of these methods improve when applied to CT scans because of better visualization of anatomic landmarks. This result suggests CT scans of the cervical spine may be warranted in all trauma patients suspected of having cervical spine injury.

Study Design: A case report of traumatic atlanto-occipital dislocation complicated by the development of anterior and posterolateral pseudomeningoceles and the late development of syringohydromyelia is presented., Objective: To describe a unique post-traumatic and postsurgical course following atlanto-occipital dislocation., Summary of Background Data: Syringomyelia is a significant potential long-term complication in patients recovering from traumatic atlanto-occipital dislocation. Cord enlargement and increased T2 signal can be a marker of abnormal cerebrospinal fluid flow dynamics. This "presyrinx state" can be seen before clinical evidence of neurologic compromise. Pseudomeningocele formation after atlanto-occipital dislocation is rare, with only 3 reported cases. To our knowledge, all reported cases describe retropharyngeal pseudomeningoceles, and posterolateral pseudomeningocele as seen in this case has not previously been described., Methods: A single case is reported with an emphasis on the imaging findings related to the patient's subsequent neurologic deterioration., Results: Following a pedestrian-motor vehicle collision, the patient received initial evaluation and treatment at a local foreign medical facility, where his cervical spine was cleared. Several days following stabilizing treatment and surgery, the patient was transferred to a foreign-based United States military medical facility and ultimately to our institution, where magnetic resonance imaging demonstrated occipitocervical dissociation. The patient was taken to the operating room for surgical stabilization. Four months after his index operation, the patient underwent halo removal. Follow-up magnetic resonance imaging revealed thickening of the cervical spinal cord in conjunction with diffuse high cord T2 signal and a small low cervical segment of syringomyelia. The patient was observed with follow-up magnetic resonance imaging obtained after 1 month. At this time, the low cervical syrinx had enlarged slightly, a small thoracic syrinx was observed, and cine imaging of cerebrospinal fluid flow demonstrated obstruction at the level of the foramen magnum. The patient was taken to the operating room fordecompression of the foramen magnum and posterior fossa and duraplasty. One month later, the patient's clinical condition began to deteriorate, and repeat imaging showed continued enlargement of the patient's syrinx and hydrocephalus. He was admitted for an urgent shunt procedure but unfortunately sustained cardiorespiratory arrest while on the ward awaiting surgery., Conclusions: Atlanto-occipital dislocation is rarely survivable, and delayed diagnosis can negatively affect long-term clinical outcome. This case illustrates how, despite early signs of improvement, post-traumatic syringomyelia may occur months or even years after spinal trauma and should always be considered in patients who experience late neurologic deterioration after atlanto-occipital dislocation.

Study Design: Case report of a Down syndrome patient with right vertebral artery fenestration and abnormalities of the craniovertebral junction., Objectives: Describe the utility of 3-dimensional computed tomography angiography for evaluating vertebral artery anomalies before surgery., Summary of Background Data: Previous reviews evaluating catheter angiograms identified various anomalies of vertebral artery at the craniovertebral junction. The frequency of vertebral artery anomalies is increased in patients having osseous anomalies at the craniovertebral junction. Down syndrome is associated with a high incidence of bone abnormalities at the craniovertebral junction, but there have been no published reports of vertebral artery anomalies per se at the craniovertebral junction., Methods: A 16-year-old woman with trisomy 21 presented with gait abnormalities and myelopathy in association with bone abnormalities at the craniovertebral junction, including hypoplastic odontoid and ossiculum terminale. Computed tomography angiography showed that right vertebral artery bifurcated after exiting the C2 transverse foramen with one branch passing through the C1 transverse foramen, whereas the other turned posteromedially and entered the spinal canal between C1 and C2., Results: Occipito-C2 posterior fusion was performed with a rod and screw system. Intraoperatively, the course of the anomalous right vertebral artery was identified by Doppler angiography, and the surgical approach was modified to allow safe pedicle screw insertion while avoiding vertebral artery injury. After surgery, myelopathy resolved within 3 months., Conclusions: Before corrective surgery of craniovertebral junction anomalies in patients with Down syndrome, the possibility of vertebral artery anomalies associated with abnormal craniovertebral junction anatomy should be considered. With preoperative 3-dimensional computed tomography angiography, we can precisely identify the anomalous vertebral artery and modify the surgical approach to reduce the possible risk of intraoperative vertebral artery injury in advance.

Study Design: A retrospective review of 21 patients with spondyloepiphyseal dysplasia congenita (SEDC), including 7 operated patients for atlantoaxial subluxation., Objectives: To clarify the morphological findings of atlantoaxial subluxation in SEDC patients and to evaluate the operative procedures based on these image findings., Summary and Background Data: The presence of atlanto axial sublucation with hypoplasia of the odontoid and/or lax ligaments leads to myelopathy in patients with spondyloepiphyseal dysplasia congenita., Methods: We retropectively reviewed the physical and morphological findings on atlantoaxial images and the clinical findings of myelopathy in 21 patients with SEDC., Results: Myelopathy was found in 9 individuals with severe SEDC who presented with marked short stature and severe coxa vara; of these, 6 had gait disturbances. On the images of the 9 patients with myelopathy, the average sagittal canal diameter (SCD) at the level of the atlas was only 9.2 mm (range, 7-12 mm) with progressive atlantoaxial subluxation. The average atlantodental interval (ADI) was 3.5 mm (range, 2-6 mm) in the presence of a sagittal atlas diameter (SAD) of less than 27.1 mm (range, 22-36 mm). Surgery was performed for 6 of the patients with myelopathy. Since their SADs were small, and the average SCD, at 9.9 mm (8-14 mm), was narrow even at the position of extension (the position of reduction for atlantoaxial subluxation), C1 laminectomy was needed for all these patients, and occipital-cervical posterior fusion was performed. Stability was satisfactory in all cases and the operative outcome for myelopathy was excellent for 1 case, fine for 4, and fair for 2., Conclusion: A small SAD may limit the effectiveness of reducing atlantoaxial subluxation. Persistent narrowing of the SCD may require concomitant C1 laminectomy and occipital-cervical fusion.

Study Design: A case report is presented., Objectives: To describe the diagnostic procedure, treatment, and outcome of a 56-year-old man with posterior atlanto-occipital dislocation and concomitant discoligamentous C3-C4 instability., Case Report: A 56-year-old male seat-belted driver of a car was involved in an accident. After initial spontaneous breathing and weak movements of all his extremities, artificial respiration became necessary because of increasing respiratory insufficiency. Radiologic diagnostics, including computed tomography scans, showed a posterior atlanto-occipital dislocation and a Grade 2 craniocerebral trauma with occipital subarachnoidal bleeding. Further examination showed a serial rib fracture with concomitant hemopneumothorax. After stabilization of the patient, magnetic resonance imaging of the cervical spine showed a contusion of the upper cervical spinal cord. Additionally, rupture of the interspinal ligaments and the posterior longitudinal ligament could be seen, as well as a rupture of the intervertebral C3-C4 disc. Operative stabilization was performed by posterior fusion of C0-C4 using the CerviFix-System and autogenous bone grafts taken from the iliac crest. At 12 months after the operation, the patient had only slight weakness of the left arm and a 70% limitation in the range of motion of the cervical spine., Conclusions: With improvements in advanced trauma life support, the number of patients with atlanto-occipital dislocation admitted to hospital alive is increasing, so this particular lesion must be kept in mind. When the patient survives the accident, the long-term prognosis is quite good, with a high rate of recovery after initial neurologic deficits.

Study Design: The significance of occipitoaxial angle in the development of subaxial subluxation after occipitocervical fusion was determined in a minimum 5-year follow-up study performed retrospectively., Objective: To clarify the association between the position of the fixed occipital bone and axis and the development of subaxial subluxation., Summary of Background Data: There have been few reports describing the association between the position of fixation of the occipital bone and axis and subaxial lesion in occipitocervical fusion., Materials and Methods: Thirty-eight patients with rheumatoid arthritis who underwent occipitocervical fusion for irreducible atlantoaxial dislocation were reviewed. The angle between the McGregor line and the inferior surface of the axis (O-C2) was measured in healthy volunteers and patients who had undergone occipitocervical fusion. The association between any changes in the alignment of the cervical vertebrae and the development of subaxial subluxation during follow-up periods was studied., Results: The number of the patients in whom postoperative kyphosis and swan neck deformity developed was only five, but in four (80%) of them, retroversion of the occipital bone was used to increase the O-C2 angle. In 14 patients, in whom anteversion of the occipital bone against the axis was excessive, 12 (86%) patients experienced subaxial subluxation after surgery. In the patients in whom fixed O-C2 angles were in normal range, only one patient developed such abnormal changes in the middle and lower cervical vertebrae., Conclusion: It is necessary to give attention to the position of the fixed occipital bone and axis during procedures of occipitoaxial fusion for patients with rheumatoid arthritis.

Study Design: A finite element investigation to determine the causal mechanisms that lead to odontoid fracture., Objectives: To elucidate which loading scenarios, including rotational moments, compression-tension, and lateral and anteroposterior shear, can result in Type I, Type II, and Type III odontoid failures., Summary of Background Data: There is considerable controversy about the major loading path that causes odontoid fractures. A review of the clinical and laboratory research literature did not provide a consensus on this issue., Methods: A three-dimensional, nonlinear finite element model of the occipito-atlantoaxial (C0-C1-C2) complex was generated from human cadaveric data. Force loads were applied at the posterior margin of the occiput and were applied as lone entities or after the model was prepositioned in flexion, extension, or lateral-bending moments through applied rotation moments. Intraosseous stresses were reported to characterize the probability of fracture due to the applied loadings., Results: The data indicate that hyperextension can lead to failure of the odontoid at its superior tip (Type I). Finite element model predictions also demonstrated the propensity of loads that induce axial rotation to create relatively high maximum von Mises stress in the Type II fracture region. Flexion prepositioning reduced the stress response of the odontoid., Conclusions: Force loading that puts the head in extension coupled with lateral shear or compression leads to Type I fractures, whereas axial rotation and lateral shear can produce Type II fractures. The model failed to elucidate causal mechanisms for Type III fractures. Flexion seems to provide a protective mechanism against force application that would otherwise cause a higher risk of odontoid failure.

Study Design: Evaluation of results a longer than 10-year follow-up of patients with upper cervical lesions due to rheumatoid arthritis who underwent occipitocervical fusion., Objective: To determine the final outcome of patients with upper cervical lesions due to rheumatoid arthritis treated by occipitocervical fusion., Summary of Background Data: There are few studies reporting the final outcome of patients with rheumatoid arthritis treated by occipitocervical fusion and observed for longer than 10 years., Methods: The subjects were 16 patients with rheumatoid arthritis with myelopathy who underwent occipitocervical fusion with a rectangular rod more than 10 years ago. All 16 patients had irreducible atlantoaxial dislocation, and 11 also had vertical dislocation of the axis. All patients had preoperative nuchal pain, and were classified into Class II (two patients), Class IIIA (nine patients), and class IIIB (five patients) according to Ranawat's preoperative neurologic classification., Results: The atlas-dens interval remained the same as immediately after surgery. Vertical dislocation returned to the preoperative condition, despite successful surgical correction. Preoperative occipital pain disappeared or was reduced in all cases. Myelopathy improved in 12 of the 16 patients (75%) by more than one class in the Ranawat preoperative neurologic classification. Survival rate at 10 years after surgery was 38%; mean age at death was 70.7 years. The postoperative periods during which patients could walk by themselves ranged from 6 months to 13 years (mean, 7.5 years)., Conclusions: Occipitocervical fusion for patients with rheumatoid arthritis is useful for decreasing nuchal pain, reducing myelopathy, and improving prognosis.

Study Design: A retrospective clinical review of patients with atlanto-occipital dislocations., Objectives: To determine if fusion of the occiput to C1 can be accomplished without extension to the axis., Summary of Background Data: Patients with atlanto-occipital dislocations who have preservation of spinal cord function are quite rare. The standard approach to stabilization has been fusion of the occiput to the axis (C2). This may compromise rotation unnecessarily, however. The authors investigated the success of attempting to fuse only the occiput to C1 in children., Methods: Two children with atlanto-occipital dislocation who had normal neurologic function underwent fusion from the occiput to the atlas after reduction., Results: Both cases showed successful fusion with no unwanted extension to lower levels. Full head rotation was preserved., Conclusions: This technique restores stability without restricting rotation.

Study Design: This study compared the reproducibility of three techniques used to measure translation between the occiput and C1 in children with Down syndrome., Objectives: Intraobserver and interobserver variability were computed to determine if there is a reliable way to measure occiput-C1 instability., Summary of Background Data: No studies have been performed comparing measurement techniques in children with Dow syndrome., Methods: Powers ratios, basion-axial intervals, and translational anteroposterior motion as described by Wiesel and Rothman were calculated for 50 pairs of flexion-extension lateral cervical radiographs from children with Down syndrome. Calculations were made on two occasions by four reviewers., Results: Mean differences between measurements for two observers were 0.14 for the Powers ratio, 1.3 mm for the Wiesel technique, and 1.8 mm for the basion-axial interval. The 95th percentiles of the differences between measurements for two observers were 0.38 for Powers ratios, 3.5 mm for the Wiesel technique, and 5.3 mm for the basion-axial interval., Conclusions: Measurement of atlanto-occipital translation by any of these methods is not reproducible. Although the technique by Wiesel and Rothman is the easiest to apply, confirmation of instability with magnetic resonance imaging should guide management.

Study Design: The sensitivity of plain radiographs for diagnosing traumatic atlanto-occipital dislocation and its association with craniocervical junction subarachnoid hemorrhage was examined in a retrospective review of seven patients., Objective: The purpose of this study was to demonstrate the frequency of nondiagnostic plain radiographs and the common association of craniocervical junction subarachnoid hemorrhage in the context of reported cases of atlanto-occipital dislocation to facilitate better recognition of this injury. The use of sagittal reconstructions of computed tomography or sagittal magnetic resonance imaging for diagnosis was evaluated., Summary of Background Data: Although traumatic atlanto-occipital dislocation is a common cause of motor vehicle fatalities, survival has been more common in the last 16 years. However, the diagnosis was missed on lateral cervical radiographs in 38% of children and 59% of adults; fewer than half were diagnosed subsequently with plain radiography. Moreover, the diagnosis of traumatic atlanto-occipital dislocation often was not considered, because more than half of the survivors had no neurologic abnormality or unilateral deficit. Consequently, more than one third of initially undiagnosed patients experienced neurologic deterioration due to inadequate cervical immobilization. Additional radiographic studies allowing diagnosis were prompted by the neurologic worsening., Methods: The authors reviewed seven patients treated with traumatic atlanto-occipital dislocation during a 14-year period. Emergency department records were compared with reexamination of initial cervical radiographs to determine the success in diagnosis by means of published methods. The frequency of cranio-cervical junction subarachnoid hemorrhage on computed tomography was determined, and the use of sagittal imaging for subsequent diagnosis was evaluated., Results: In the emergency department, only one patient's condition was diagnosed as atlanto-occipital dislocation. Review of the initial radiographs identified an additional four patients for whom atlanto-occipital dislocation could be diagnosed. Sagittal computed tomography reconstruction or sagittal magnetic resonance imaging identified the remaining two. All but one patient had craniocervical junction subarachnoid hemorrhage. A review of reported cases revealed a common association of craniocervical junction subarachnoid hemorrhage with traumatic atlanto-occipital dislocation but not with traumatic head injury., Conclusions: The diagnosis of traumatic atlanto-occipital dislocation is often missed in the emergency department, and current methods for evaluating the integrity of the atlanto-occipital joint on cervical radiographs fail to identify all patients with this injury. Although infratentorial subarachnoid hemorrhage is uncommon in traumatic head injury, craniocervical junction subarachnoid hemorrhage is often associated with atlanto-occipital dislocation and should raise the suspicion of severe craniocervical ligamentous injury. Sagittal computed tomography reconstructions or sagittal magnetic resonance imaging can allow for the diagnosis when plain radiography is inconclusive.

Study Design: In this study, the authors evaluated upper cervical spine in 75 children and adolescents with Down syndrome on the basis of lateral flexion-extension radiographs., Objective: To assess occipitoatlantal motion and occipitoaxial motion in children and adolescents with Down syndrome compared with age-matched control subjects., Summary of Background Data: Although previous studies have described a high prevalence of occipitoatlantal hypermobility in Down syndrome, there have been no comparisons with age-matched control subjects. Only a few reports have mentioned the physiologic relation between the occiput and axis other than basilar impression. Moreover, there have been no reports examining anteroposterior mobility in abnormal conditions., Methods: Seventy-five children and adolescents with Down syndrome and 30 age-matched control subjects were examined. Lateral radiographs of the upper cervical spine in flexion and extension were taken, and anteroposterior translation of the occiput in relation to the atlas and axis was measured., Results: Anteroposterior occipitoatlantal hypermobility was found to be present in children and adolescents with Down syndrome even when compared with age-matched control subjects. Occipitoaxial hypermobility was observed only when atlantoaxial instability was present., Conclusion: In evaluating the upper cervical spine in Down syndrome, it is necessary to pay attention to the relation between the occiput, atlas, and axis.

Study Design: The upper cervical spines of 57 subjects with Down's syndrome were retrospectively examined, with special attention to atlanto-occipital mobility., Objective: To examine the magnitude of atlanto-occipital mobility and its clinical significance in subjects with Down's syndrome., Summary of Background Data: Atlanto-occipital translation of more than 1 mm in adults implies instability. However, the normal value in children with Down's syndrome has not been established, and the value in Down's syndrome has not been evaluated based on a comparison between subjects with Down's syndrome and control subjects., Methods: Measurements were made by Wiesel and Rothman's method in 38 subjects with Down's syndrome and 34 control subjects., Results: Atlanto-occipital translation in the Down's syndrome group ranged from 0-6.4 mm (mean, 2.3 mm), whereas in the control group it ranged from 0-2.1 mm (mean, 0.61 mm). The difference was statistically significant. Of the 38 subjects with Down's syndrome, 37 were asymptomatic., Conclusion: The magnitude of atlanto-occipital translation, as expected, apparently was greater in subjects with Down's syndrome than in control subjects. Although the possibility of neurologic complications should be considered whenever unusually high atlanto-occipital mobility is seen, a majority of the subjects with Down's syndrome were asymptomatic.

Study Design: Five asymptomatic subjects underwent provocative injections of the lateral atlanto-axial and atlanto-occipital joints., Objectives: This study isolated and stimulated the lateral atlanto-axial and atlanto-occipital joints via fluoroscopically guided intra-articular injections to determine if they are potential pain generators. If they are pain generators, preliminary pain pattern maps will be constructed., Summary of Background Data: The cervical zygapophyseal joints (C2-3 to C6-7) are potential pain generators as demonstrated by referred pain induced via isolated intra-articular joint injections in normal subjects. Tentative referral patterns based on direct mechanical stimulation of the lateral atlanto-axial and atlanto-occipital joints have not been reported., Methods: Five volunteers without histories of upper cervical pain underwent two joint injections each. In all five subjects, the left atlanto-occipital and right lateral atlanto-axial joints were stimulated via injection of contrast medium causing distension of the joint capsule., Results: Referred pain was produced with all ten injections. The lateral atlanto-axial injections resulted in consistent referral patterns, whereas the atlanto-occipital referral patterns varied significantly. A tentative composite diagram of the experimentally induced pain was created for each joint., Conclusion: This study confirms the nociceptive ability of these cervical synovial joints. This study may assist the clinician in the differential diagnosis of head and neck pain.

Study Design: A simple method, thin-slice contrast-enhanced computed tomographic (CT) scan, was evaluated as a first-line rapid screening procedure for diagnosing traumatic occlusion of the vertebral artery at the craniovertebral junction., Objectives: This procedure was performed in patients suffering from injuries of the high cervical spine or the craniovertebral junction. Vertebral angiography was undertaken after this procedure to confirm the diagnosis., Summary of Background Data: Well-enhanced vertebral arteries can be demonstrated clearly in normal subjects by using this method. Occlusion of the vertebral artery produces delayed contrast enhancement of the proximal artery and abrupt interruption of its course., Methods: Thin-slice CT scan was performed from the atlas to the occipital condyles after an intravenous injection of angiograffin. The plane of the CT scan was aligned in a parallel manner to the upper margin of the atlas. The CT scanning was repeated until the contrast enhancement of the vertebral arteries became faint., Results: Occlusion of the unilateral vertebral artery was successfully diagnosed in a patient with Jefferson's fracture by using the present technique. A subsequent vertebral angiography confirmed the diagnosis., Conclusions: The present technique should be performed as a routine screening procedure in patients suffering from injuries to the craniovertebral junction.

Several cases of occipito-atlantal instability have been reported in patients with Down's syndrome. However, standards for radiographic measurement and normal values for translational motion at the occiput-C1 level have not been established for the Down's patient. A retrospective analysis of 102 flexion and extension lateral cervical spine radiographs of 73 patients with Down's syndrome was performed. Patients with congenital cervical spine anomalies, C1-C2 instability, or previous neck surgery were excluded. Occiput-C1 translation was measured by the technique described by Wiesel and Rothman. In normal adult patients, occiput-C1 translation should be no more than 1 mm by this method. Analysis of the data demonstrated a range of 0 to 10 mm, with a mean of 2.62 mm and a standard deviation of +/- 1.94 mm. Only 30 sets of films (29%) representing 27 patients (37%) showed anteroposterior translation of 1 mm or less. This laxity was not dependent on patient age in the current study group. A review of these patients' medical records did not disclose any evidence of impaired neurologic function related to cervical spine instability. The authors' data suggest that the prevalence and magnitude of occipito-atlantal instability in Down's syndrome is greater than previously appreciated.

A young adult sustained a traumatic atlantooccipital dislocation together with fracture-dislocation at C.4/5 level and had total neurologic deficit below C4 segment. He retained full consciousness but required respiratory support. He developed a stress ulcer with hemorrhage and evidence of "shock lung." He responded to intensive care. Surgery on the 11th day secured reduction and internal fixation at both levels. Death due to respiratory and cardiac arrest followed on the 14th day. Postmortem examination revealed edema of the brain and brainstem.

Lateral cervical spine films from 175 normal examinations of adults performed in the emergency room of North Carolina Baptist Hospital were analyzed to establish some norms and relationships in the upper cervical spine. The predens angle was found to be between 0 degree-13 degrees (mean 5.57 degrees) in neutral position and 0-18 degrees (mean 9.27 degrees) in flexion in most persons. Ninety-two percent of persons have angles greater than 3 degrees in flexion. A V-shaped predens space is not indicative of injury to the cruciate ligament. Virtually every person has posterior slanting or tilting of the dens and the range of values is up to 35 degrees (mean 17.43 degrees). Ninety-eight percent of persons have an angle greater than 6 degrees. A tilted dens does not indicate acute or remote trauma. No relationship was identified between the predens angle and the dens tilt angle. The posterior arch of the atlas can be found at any position between the occiput and spinous process of C2 in all positions of the head and neck. Hence, fanning or widening of the C1-C2 interspinous distance is not a reliable index of ligamentous injury in the upper cervical spine.