Craniocervical developmental anatomy and its implications

Introduction  Congenital and developmental osseous abnormalities and anomalies that affect the craniocervical junction complex can result in neural compression and vascular compromise and can manifest itself with abnormal cerebrospinal fluid dynamics. An understanding of the development of the craniocervical junction is essential to recognize the pathological abnormalities. Materials and methods  Atlas assimilation, segmentation failures, os odontoideum, basilar invagination, and the various syndromes that affect the craniocervical junction have been analyzed. The natural history provides an added insight into its treatment. Results  Proatlas segmentation abnormalities surrounded the foramen magnum and the posterior arch of C1. Hindbrain herniation was associated in 33 of the 90 children involved. Spastic quadriparesis presented in 80% and lower cranial nerve abnormalities in 33%. Vertebrobasilar dysfunction was observed in 40% and trauma presentation seen in 60% of individuals. Atlas assimilation was present in 550 individuals who were evaluated for craniovertebral junction abnormalities. Hindbrain herniation occurred in 38%. Segmentation failure of C2 and C3 vertebrae compounded the abnormal dynamics resulting in atlantoaxial instability. This was a reducible instability with formation of pannus around the odontoid process until it became irreducible at approximately 14 years of age. Unilateral atlas assimilation caused torticollis in children. Os odontoideum was investigated regarding craniocervical trauma at a young age. Conclusion  The conclusion was that os odontoideum was associated with an unrecognized fracture in children below the age of 5 with a previously normal odontoid structure as observed in our series. Atlas and axis abnormalities were reviewed in this series. This large database has provided an understanding of the natural history of many entities and allowed treatment protocols to be established that have stood the test of time.     

齿状突切除术后颅颈连接不稳定的处理

目的探讨术前未能明确诊断，而齿状突切除术后颅颈连接不稳定的诊断和治疗方法。方法回顾性分析术后8例不稳定病例的诊断治疗经过。结果7例经枕下减压，枕颈融合固定取得了满意效果。无并发症及死亡病例。结论齿状突切除术后颅颈连接不稳定可以通过枕下减压，枕颈融合治疗。     

Surgical approaches: postoperative care and complications “transoral–transpalatopharyngeal approach to the craniocervical junction”

INTRODUCTION: The ventral approach to the craniocervical border has been described for decompression of irreducible extradural pathology. The procedures utilized encompass the transoropharyngeal and median mandibulotomy with glossotomy and the transpalatal procedures. This study was aimed to review the utility of the transoral-transpalatopharyngeal approach. CLINICAL MATERIALS AND METHODS: Seven hundred thirty-three patients underwent transpalatopharyngeal approach for decompression of the brain stem and cervicomedullary junction. Of these, 280 were children below the age of 16 years. The main indication was irreducible ventral pathology compressing the brain stem and cervicomedullary junction. Two hundred two children had irreducible basilar invagination, 28 had proatlas segmentation abnormalities, os odontoideum with a dystopic os odontoideum in 30, and spinal tumors in seven (chordoma, fibrous dysplasia, osteoblastoma). Seven patients with Down's syndrome and irreducible bony compression of the ventral cervicomedullary junction were seen. There were six other miscellaneous diagnoses. All children required craniocervical stabilization which was carried out under the same anesthetic as the transoral procedure. OPERATIVE PROCEDURE: The procedure entailed fiber-optic intubation. The patient was placed in cervical traction prior to the anterior procedure. The soft palate was split only in individuals with a short clivus with a high riding clivus-odontoid articulation. Craniocervical stabilization was performed in the prone position under the same anesthetic. RESULTS: There was one retropharyngeal infection postoperatively. No cesium fluoride leaks were encountered. Velopalatine incompetence was seen in five children who already had preoperative brain stem dysfunction. Neurological recovery was the rule. Patients who had preoperative syringohydromyelia had resolution of the syrinx on postoperative magnetic resonance imaging. DISCUSSION: The author's technique is described. Since 1977, the procedure has been performed in 732 patients (280 children) and has evolved into a safe and direct approach to the ventral cervicomedullary junction with minimal morbidity and mortality.     

Occipitocervical fixation in the surgical treatment of pathologies of the craniovertebral junction

BACKGROUND AND PURPOSE: New surgical approaches to the tumors of the skull base necessitate removal of certain bone structures of the base. In the case of the transcondylar far-lateral approach, the whole occipital condyle and lateral mass of C1 are removed resulting in iatrogenic instability. Consequently, an occipitocervical fixation is needed. The aim of the study was to assess the usefulness of the CCD cervical system for the occipitocervical fixation in the surgery of the tumors of the craniovertebral junction. MATERIAL AND METHODS: The authors present the application of the CCD cervical system produced by Medtronic Sofamor-Danek in three patients who underwent surgery of tumors of the foramen magnum, clivus or craniovertebral junction. The system consists of two titanium rods, which adjusted to the curvature of the spine and the occiput, are fixed by laminar cervical and occipital hooks, fixed to the trepanation hole edge or the edge of the foramen magnum. It is also possible to use screws driven to the occipital bone if it is more than 7 mm thick. RESULTS: The system fixation is simple and relatively short. Good stabilization was achieved in all patients. No complications caused by the implants have been observed. CONCLUSIONS: The CCD cervical system can be successfully used for the occipitocervical fixation in a lateral transcondylar approach and in the cases of other non-traumatic craniocervical instability. It is especially recommended in cases of unusual thinning of the occipital bone or in osteoporotic states.     

Surgical treatment of os odontoideum

Os odontoideum is a rare disease. There have been few reports of os odontoideum in the literature. In this study we retrospectively reviewed eight surgically treated patients. One patient underwent C1-2 transarticular screw fixation, five patients underwent C1-2 polyaxial screw and rod fixation and two patients with dystopic os odontoideum underwent occipito-cervical (O-C) fusion. Of the eight patients, neck pain was alleviated in seven (87.5%). Of the six patients who had neurological signs and symptoms, five (83.3%) exhibited neurological improvement. Radiologically, solid fusion was observed in seven patients (87.5%). Active surgical treatment should be considered even in patients with os odontoideum who exhibit mild symptoms. In most patients with os odontoideum, use of the C1-2 polyaxial screw and rod technique may be the most appropriate treatment. In patients with dystopic os odontoideum, O-C fusion should be considered.     

Clinical experience with rigid occipitocervical fusion in the management of traumatic upper cervical spinal instability.

Traumatic injuries of the craniovertebral junction or the upper cervical spine may result in occipitocervical (OC) or upper cervical spinal instability. Internal fixation can provide immediate stability to this region. Over a 6-year period, 16 patients with traumatic upper cervical spinal instability underwent a posterior approach OC fusion, using a plate and screw system, at the neurosurgical department of our institution. One patient died. The postoperative course of all the other patients was uncomplicated. At the most recent follow-up examination, all patients had satisfactory fusion. OC fusion with a plate and screw system is a safe and effective method for the treatment of traumatic craniovertebral and high cervical spine instability. Accurate imaging diagnosis and strict patient selection are the keys to a successful outcome.     

Odontoid compression of the brainstem without basilar impression-- "odontoid invagination".

We report five patients with odontoid invagination, in which the odontoid process bulges upward into the foramen magnum and compresses the brainstem without deformity of the occipital bone. Two patients had a craniovertebral abnormality associated with Chiari malformation without instability of the craniovertebral junction (stable odontoid invagination). The other three patients had dislocation of the craniovertebral junction due to iatrogenic destruction of the occipital condyle, rheumatoid arthritis or an anomaly of C2 (unstable odontoid invagination). Patients with stable odontoid invagination underwent a transoral odontoidectomy followed by occipitocervical fixation. Those with unstable odontoid invagination underwent cervical traction followed by posterior fixation in reducible cases, while in irreducible cases odontoidectomy with subsequent occipitocervical fixation was performed. Decompression of the neuraxis together with symptomatic improvement was achieved in all patients and none became unstable or developed new symptoms during follow-up ranging from 3 to 15 years.     

Protection of the C1 posterior arch in atlantal lateral mass fixation: technical case report.

Screw fixation of the C1 lateral mass is a relatively new technique designed to allow for C1/C2 fixation in scenarios where transarticular screw fixation is not safe or possible. In order to place the screw at the base of the C1 arch, it has been recommended to drill at the junction of the C1 posterior arch and the lateral mass of C1, to accommodate the screw head. This may, however, weaken the C1 arch, making it prone to fracture. In this new technique, we describe a modification to the current technique to allow placement of this screw without compromising the C1 arch. A case of atlantoaxial instability secondary to os odontoideum is described. C1 lateral mass fixation is achieved by selecting a screw 10 mm longer than required and placing the screw 10 mm above the bony entry point, for easier placement of the rod and avoidance of drilling at the base of the C1 arch. Adequate and safe C1/C2 fixation was achieved. Sublaminar wiring was performed around the C1 arch with no weakening or fracture of the arch. We believe that in order to place reasonable C1 lateral mass screws, it is inadvisable to drill the base of the junction between the C1 posterior arch and lateral mass as this may lead to arch weakening and failure. Easier instrumentation can be performed and the integrity of the C1 arch maintained using this alternate technique.     

Vertical reduction using atlantoaxial facet spacer in basilar invagination with atlantoaxial instability

Although posterior segmental fixation technique is becoming increasingly popular, surgical treatment of craniovertebral junctional disorders is still challenging because of its complex anatomy and surrounding critical neurovascular structures. Basilar invagination is major pathology of craniovertebral junction that has been a subject of clinical interest because of its various clinical presentations and difficulty of treatment. Most authors recommend a posterior occipitocervical fixation following transoral decompression or posterior decompression and occipitocervical fixation. However, both surgical modalities inadvertently sacrifice C0-1 and C1-2 joint motion. We report two cases of basilar invagination reduced by the vertical distraction between C1-2 facet joint. We reduced the C1-2 joint in an anatomical position and fused the joint with iliac bone graft and C1-2 segmental fixation using the polyaxial screws and rods C-1 lateral mass and the C-2 pedicle.     

Surgical Treatment of Craniovertebral Junction Instability : Clinical Outcomes and Effectiveness in Personal Experience

Objective

Craniovertebral junction (CVJ) consists of the occipital bone that surrounds the foramen magnum, the atlas and the axis vertebrae. The mortality and morbidity is high for irreducible CVJ lesion with cervico-medullary compression. In a clinical retrospective study, the authors reviewed clinical and radiographic results of occipitocervical fusion using a various methods in 32 patients with CVJ instability.

Methods

Thirty-two CVJ lesions (18 male and 14 female) were treated in our department for 12 years. Instability resulted from trauma (14 cases), rheumatoid arthritis (8 cases), assimilation of atlas (4 cases), tumor (2 cases), basilar invagination (2 cases) and miscellaneous (2 cases). Thirty-two patients were internally fixed with 7 anterior and posterior decompression with occipitocervical fusion, 15 posterior decompression and occipitocervical fusion with wire-rod, 5 C1-2 transarticular screw fixation, and 5 C1 lateral mass-C2 transpedicular screw. Outcome (mean follow-up period, 38 months) was based on clinical and radiographic review. The clinical outcome was assessed by Japanese Orthopedic Association (JOA) score.

Results

Nine neurologically intact patients remained same after surgery. Among 23 patients with cervical myelopathy, clinical improvement was noted in 18 cases (78.3%). One patient died 2 months after the surgery because of pneumonia and sepsis. Fusion was achieved in 27 patients (93%) at last follow-up. No patient developed evidence of new, recurrent, or progressive instability.

Conclusion

The authors conclude that early occipitocervical fusion to be recommended in case of reducible CVJ lesion and the appropriate decompression and occipitocervical fusion are recommended in case of irreducible craniovertebral junction lesion.     

Magnetic resonance imaging confirmation of resolution of periodontoid pannus formation following C1/C2 posterior transarticular screw fixation.

Chronic odontoid fractures are considered unstable spinal lesions. Chronic instability in this region leads to the development of an inflammatory pannus, which can progress resulting in spinal cord compression radiographically and a myelopathy syndrome clinically. In this report we document three cases of reversal of pannus after C1/C2 transarticular screw fixation of an unstable odontoid fracture. Three patients were identified with chronic odontoid fractures and spinal cord compression due to periodontoid pannus formation. All patients presented with a progressive myelopathy syndrome. All patients underwent preoperative and postoperative magnetic resonance imaging (MRI) of the craniovertebral junction. C1/C2 transarticular screw fixation was performed for stabilization of C1/C2. Postoperatively there were no complications. Postoperative MRI at 6 months demonstrated resolution of the ventral pannus. Moreover, all patients exhibited improvement of preoperative neurological deficits. MRI is the imaging technique of choice for diagnosis and follow-up of patients with chronic odontoid fractures and ventral pannus. C1/C2 transarticular screw fixation provides a viable method for spinal stabilization in this region. In addition, stabilization can result in resolution of inflammatory pannus formation secondary to instability of the C1/C2 articulation.     

Decision making

INTRODUCTION: The craniocervical junction is affected by numerous pathological processes. This involves congenital, developmental, and acquired abnormalities. It can result in neurological deficit secondary to neurovascular compression, abnormal cerebrospinal fluid dynamics, and craniovertebral instability. A physiological approach based on an understanding of the craniovertebral junction dynamics, the site of encroachment and stability was formulated in 1977 and has stood the test of time. The author has reviewed 5,300 patients with neurological symptoms and signs secondary to an abnormality of the craniocervical junction. This includes 2,100 children. TREATMENT OF CRANIOVERTEBRAL JUNCTION ABNORMALITIES: The factors that influence the specific treatment are: (1) reducibility of the lesion, (2) mechanics of compression and the direction of encroachment, (3) the presence of abnormal ossification centers and epiphyseal growth plates, and (4) the cause of the pathological process. STABILITY AT THE CRANIOCERVICAL JUNCTION: Instability at the craniocervical junction is considered when the predental space is more than 5 mm in children below the age of 8, when the separation of the lateral atlantal masses is more than 6 mm where the cruciate ligament is felt to be disrupted, and if there is vertical translation of more than 2 mm between the clivus and the odontoid process signifying occipital instability. The gap between the occipital condyle and the lateral atlas facet should never be visible on lateral cervical radiographs. Present day magnetic resonance imaging can visualize disrupted transverse cruciate ligament, alar ligaments, tectorial membrane, and bony malalignment. The primary aim of treatment is to relieve compression at the cervicomedullary junction. Hence, stabilization is paramount in reducible lesions to maintain neural decompression. Irreducible lesions require decompression at the site where the compression has occurred; these were divided into ventral and dorsal compression states. In the former compression state, the operative procedure was a ventral decompression through a palatopharyngeal route, LeForte dropdown maxillotomy, or the lateral extrapharyngeal approach. In dorsal or dorsolateral compression states, a posterolateral decompression is required. If instability is present after decompression, posterior fixation is mandated.     

齿状突游离小骨合并寰枢椎脱位的外科治疗临床经验

目的总结齿状突游离小骨合并寰枢椎脱位患者外科治疗的经验。方法回顾性分析唐都医院神经外科2010年8月~2015年12月治疗的9例齿状突游离小骨合并寰枢椎脱位患者的临床资料。所有患者均采用颈后路寰枢椎椎弓根螺钉或者枕颈螺钉内固定植骨融合术进行治疗,统计并比较术前术后影像学测量指标(改良寰齿前间距MADI,脊髓可用间隙SAC)及JOA评分评价手术疗效。结果 9例患者均成功实施手术,无手术相关并发症发生;术后患者的症状均明显改善,MADI明显缩小,SAC明显增加,颈髓角135°;手术前和手术后3个月时的JOA评分比较,差异有统计学意义(P0.05);术后3个月时复查寰枢椎均达到复位和骨性融合。结论对齿状突游离小骨合并寰枢椎脱位患者,采用术中寰枢椎复位,寰枢椎椎弓根螺钉或枕颈螺钉内固定术可以有效进行寰枢椎的融合,固定效果良好,缓解脊髓受压,改善了齿状突游离小骨及寰枢椎脱位导致的神经功能症状。     

Os odontoideum as a rare but possible complication in children with dyskinetic cerebral palsy: a clinical and neuroradiologic study

The authors describe a 12-year-old boy with dyskinetic (athetoid-dystonic subtype) cerebral palsy and os odontoideum. Dystonic and choreoathetotic components in cerebral palsy are movement disorders that are difficult to treat and cause major disability. Dystonic posturing causes excessive flexion, extension, and rotation of the neck. Repetitive abnormal movements in patients with this type of cerebral palsy give rise to a higher incidence of pathologic conditions affecting the craniovertebral junction. Os odontoideum is one of these pathologies, and it represents a rare anomaly of the odontoid process. There are only a few reports describing os odontoideum in children with dyskinetic cerebral palsy. This clinical and neuroradiologic study focuses on the problem of atlantoaxial instability and os odontoideum in these forms of cerebral palsy, which is too often underestimated.     

Fixating techniques of craniocervical junction: selection criteria

Adequate choice of fixation technique at craniocervical junction depends on many factors: anatomical conditions at fusion site (e.g. anterior dislocations of the odontoid and rupture of the transverse ligament are contraindications for direct odontoid screw fixation. Sublaminar wiring and interlaminar clamps are useless in case of deficiency of posterior bony elements of C1 and C2 whether a result of laminectomy or destruction), bone quality (osteopenic bone is contraindication for screw techniques either transarticular or transpedicular). Enclosing of occipital bone into instrumentation may be difficult in wire and clamping techniques. In contrast screw techniques allow for easy grip the occipital bone. Screw techniques seem ideal in cases requiring enclosing of the occipital bone. The fusion rate at C1/C2 level seems independent of fixation techniques. When supplemented with external immobilization even biomechanically inferior wiring or interlaminar clamping provide nearly 100 rate of fusion. Screw techniques are technically demanding but they seem the method of choice when occipital bone is to be enclosed in instrumentation.     

内镜经口入路齿状突切除治疗颅底凹陷简

目的探讨不伴颈枕融合的内镜经口入路切除齿状突治疗颅底凹陷的可行性。方法回顾性分析6例具有难以缓解的延颈髓交界区压迫症状病人的临床资料,临床表现为颈痛、肢体感觉异常、脊髓性四肢轻瘫。术前影像学检查显示后半脱位的游离齿状突压迫颈枕交界区。病人均在没有颈枕后固定和骨性融合的情况下实施内镜经口入路齿状突切除术。结果病人经单纯内镜经口齿状突切除术后均成功获得颈枕交界区减压,且术后清醒即拔除麻醉插管,未行气管切开或术后置入胃管。本组病例术后未出现鼻咽反流、脑脊液漏、局部感染或脑膜炎等术后并发症。术后CT和MRI显示齿状突全切除和颈枕交界区充分减压。随访1～5年,未见颈枕交界区不稳定,且病人神经功能均显著恢复。结论内镜经口入路是到达寰椎和齿状突最近、最直接的手术入路。该入路在实现齿状突完全切除、颈枕交界充分减压的同时,不需要行颈枕后固定及融合,不要求气管切开,不会增加发生并发症的风险。     

经口咽前路寰枢椎复位钢板置入内固定治疗颅颈交界部畸形的MRI评价

背景：颅颈交界部畸形经口咽前路寰枢椎复位钢板置入内固定治疗过程中,X射线、CT对于颅颈交界部病变的检查只能显示其骨性结构,无法显示脊髓情况。 目的：分析颅颈交界部畸形经口咽前路寰枢椎复位钢板内固定前后的磁共振图像,探讨MRI成像对其内固定术式的选择及效果判断的价值。 方法：选择2009-06/2010-04收治的颅颈交界部畸形患者25例,男9例,女16例,术前均行X射线、CT、MRI检查,采用经口咽前路寰枢椎复位钢板置入内固定治疗方式,置入后6个月内行MRI复查。 结果与结论：所有患者均顺利完成内固定,未出现脊髓血管损伤等严重并发症。25例患者置入后MRI成像显示内固定在位,寰枢椎复位,脊髓受压情况改善,11例随访患者中,原上颈椎局部疼痛、活动受限等情况有9例明显改善或消失。提示MRI能够多方位清晰显示颅颈交界部畸形情况,对脊髓及颅内病变的显示更直接,可为颅颈交界部畸形经口咽前路寰枢椎复位钢板置入内固定手术方式的选择、脊髓受压情况及手术效果的判断、术后恢复提供客观依据。     

Occipital condyle screw placement and occipitocervical instrumentation using three-dimensional image-guided navigation

Occipital condyle (OC) screws are an alternative cephalad fixation point in occipitocervical fusion. Safe placement of occipital, C1 lateral mass, and C2 pars screws have been described previously, but not OC screws. The craniocervical junction is complex, and a thorough understanding of the anatomy is needed.Three-dimensional (3D) image-guided navigation was used in six patients. There were no complications related to image-guided navigation during the placement of 12 OC screws and we found that this navigation can serve as a useful adjunct when placing an OC screw. Technical considerations of placing OC and C1 lateral mass screws are discussed with particular reference to patient positioning and the StealthStation® S7? image-guided navigational platform (Medtronic, Minneapolis, MN, USA). The reference arc is attached to the head-clamp and faces forward. The optical camera and monitor are positioned at the head of the table for a direct, non-obstructed line-of-sight. To minimize intersegmental movement, the OC should not be drilled until all other screws have been placed. We conclude that 3D image-guided navigation is a useful adjunct that can be safely and effectively used for placement of instrumentation of the upper cervical spine including the OC.     

High cervical C3-4 'disc' compression associated with basilar invagination

A 20-year-old male had torticollis and short neck since birth. He presented with symptom of progressive quadriparesis over a two-year period. Investigations revealed basilar invagination with marked rotation in the craniovertebral region and relatively large C3-4 region osteophytes. Serial MRI over two years showed persistent signal opposite C3-4 disc space suggestive of cord compression. Although the cord was humped over the odontoid process, there was no clear radiological evidence that the cord was compromised at this level. During surgery, instability was identified only at the craniovertebral region and not at the level of C3-4. Distraction of the lateral masses of atlas and axis and fixation using interarticular spacers and bone graft and direct screw implantation in the lateral mass of the atlas and pars of the axis resulted in reduction of the basilar invagination and of atlantoaxial dislocation. The patient had marked clinical recovery, despite the fact that no direct procedure was done for C3-4 disc decompression. The case suggests that C3-4 disc changes could be secondary to primary instability at the craniovertebral junction.     

Traumatic retroclival epidural hematoma—a pediatric entity?

Background Traumatic retroclival epidural hematoma is very rare and only a few cases are described in literature. All previous cases occurred in the pediatric population and were classically seen in pedestrians or cyclists hit by speeding motor vehicles. It is probable that horizontal articulation between the cranium and the atlas and ligamentous laxity at the craniocervical junction in this age group predispose them to ligamentous injury at the craniospinal junction and formation of retroclival hematoma. MRI or three-dimensional reconstructed CT is considered essential for diagnosing this condition. Conservative treatment is an option if neurological deficits are mild and brainstem compression is not significant. Bony fixation is, however, required if there is suspicion of instability.Case Report The authors describe the case of an 8-year-old girl who developed traumatic retroclival epidural hematoma after a motor vehicle accident and who was managed conservatively with good recovery.Conclusion This case and the review of literature suggest that retroclival epidural hematoma is a pediatric entity usually associated with ligamental injury at the craniocervical junction.