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.     

Anterolateral extension of the lateral suboccipital approach: an anatomical study

We studied the extensions of the lateral suboccipital approach (LSOA) in seven cadaver heads, in the microsurgical laboratory, in order to establish the extensions necessary to approach the anterolateral area of the foramen magnum and the jugular foramen. The extensions (bone resection) were accomplished in five progressive steps: 1) suboccipital retrossigmoid craniectomy (LSOA retrocondylar); 2) extending the craniectomy with removal of half the occipital condyle (LSOA partial transcondylar); 3) extending the drilling of the occipital condyle to open the hypoglossal foramen, followed by removal of the jugular tubercle and opening the jugular foramen (LSOA transcondylar-transjugular); 4) complete drilling of the occipital condyle (LSOA complete transcondylar); 5) LSOA complete transcondylar plus removal of the atlas lateral mass up to the odontoid process (ASOL transcondylar-transjugular). We concluded that the extensions of LSOA should be adapted to the topography of the lesion: the LSOA retrocondylar for the lateral area of the foramen magnum; the LSOA partial transcondylar for the anterolateral portion; the LSOA transcondylar-transjugular to reach the jugular foramen; the LSOA complete transcondylar for the anterior part, and the LSOA complete transcondylar/translateral mass of the atlas for extradural lesions anterior to the foramen magnum.     

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.     

Fusions at the craniovertebral junction

INTRODUCTION: The surgical management of craniovertebral junction instability in pediatric patients has unique challenges. While the indications for internal fixation in children are similar to those of adults, the data concerning techniques, complications, and outcomes of spinal instrumentation comes from experience with adult patients. Diminutive osseous and ligamentous structures and anatomical variations associated with syndromic craniovertebral abnormalities frequently complicates the approaches and limits the use of internal fixation in children. Cervical arthrodesis in the pediatric age group has the potential for limiting growth potential and causing secondary deformity. Recent advances in image analysis have enabled preoperative planning which is critical to evaluate the size of instrumentation and its relation to the patient's anatomy. Newer techniques have recently evolved and have been incorporated in the management of pediatric patients with requirement for craniocervical stabilization. MATERIALS AND METHODS: Over 750 craniovertebral junction fusions have been reviewed in children. The indications for atlantoaxial arthrodesis were: (a) absent odontoid process, dystopic os odontoideum, absent posterior arch of C1; (b) Morquio's syndrome, Goldenhar's syndrome, Conradi's syndrome, and spondyloepiphyseal dysplasia. The acquired abnormalities of trauma, postinfectious instability, and Down's syndrome completed the indication in children. The indications for occipitocervical fusion were: (a) anterior and posterior bifid C1 arches with instability, absent occipital condyles; b) severe reducible basilar invagination, unstable dystopic os odontoideum, and unilateral atlas assimilation; (c) acquired phenomenon with traumatic occipitocervical dislocation, complex craniovertebral junction fractures of C1 and C2, after transoral craniovertebral junction decompression, cranial settling in Down's syndrome and inflammatory disease such as Grisel's syndrome. Instability was seen in children with clivus chordoma and osteoblastoma. Atlantoaxial fusions were performed mainly with interlaminar rib graft fusion and more recently with the transarticular screw fixation in the older patient. In the teenager, lateral mass screws at C1 and rod fixation were made; C2 pars interarticular screw fixation and C2 pedicle screw fixation. A C2 translaminar screw fixation is described. Occipitocervical fusions were made utilizing rib grafts below the age of 6. A contoured loop fixation was made in children above the age of 7, and recently, rod and screw fixation was also utilized. RESULTS: Abnormal cervical spine growth was not seen in children who underwent craniocervical stabilization below the age of 5. The authors have reserved rigid instrumentation for children above the age of 10 years and dependent on the anatomy.     

前屈-后伸位MRI对判断颅脊交界区畸形内固定指征的临床价值

目的分析前屈-后伸位MRI对诊断Arnold—Chiari畸形可能合并寰枢椎脱位的作用,以及指导治疗的临床意义。方法回顾分析40例Arnold—Chiari畸形患者的前屈-后伸位MRI影像学资料,测量寰齿间距,通过前屈位和后伸位颈椎椎管狭窄程度分级,判断颅脊交界区稳定性。单纯Arnold．Chiari畸形患者采用枕大孔减压和枕大池扩大成形术,存在寰枢椎脱位者兼行枕颈内固定融合术。结果经前屈．后伸位MRI检查,证实有12例患者存在颅颈失稳,于枕大孔减压的同时行枕颈内固定融合术。手术后第3天颈椎影像学检查,40例中10例脊髓空洞病灶明显缩小;12例兼行枕颈内固定融合术者颅颈复位满意,脊髓压迫解除;手术后3个月随访,脊髓空洞病灶明显缩小（17例）,颅脊交界区骨痂形成、骨融合效果良好、颅颈复位无丢失（12例）,日本矫形外科评分13．08±1．40,与手术前评分（11．08±1．61）比较,差异有统计学意义（t=5．928,P=0．000）。结论前屈．后伸位MRI对判断颅脊交界区稳定性、选择适宜的手术方式具有重要意义。     

前屈-后伸位MRI对判断颅脊交界区畸形内固定指征的临床价值

目的分析前屈-后伸位MRI对诊断Arnold-Chiari畸形可能合并寰枢椎脱位的作用,以及指导治疗的临床意义。方法回顾分析40例Arnold-Chiari畸形患者的前屈-后伸位MRI影像学资料,测量寰齿间距,通过前屈位和后伸位颈椎椎管狭窄程度分级,判断颅脊交界区稳定性。单纯Arnold-Chiari畸形患者采用枕大孔减压和枕大池扩大成形术,存在寰枢椎脱位者兼行枕颈内固定融合术。结果经前屈-后伸位MRI检查,证实有12例患者存在颅颈失稳,于枕大孔减压的同时行枕颈内固定融合术。手术后第3天颈椎影像学检查,40例中10例脊髓空洞病灶明显缩小;12例兼行枕颈内固定融合术者颅颈复位满意,脊髓压迫解除;手术后3个月随访,脊髓空洞病灶明显缩小(17例),颅脊交界区骨痂形成、骨融合效果良好、颅颈复位无丢失(12例),日本矫形外科评分13.08±1.40,与手术前评分(11.08±1.61)比较,差异有统计学意义(t=5.928,P=0.000)。结论前屈-后伸位MRI对判断颅脊交界区稳定性、选择适宜的手术方式具有重要意义。     

Surgical approaches: postoperative care and complications “posterolateral–far lateral transcondylar approach to the ventral foramen magnum and upper cervical spinal canal”

Background  Lesions that affect the lower clivus, foramen magnum, the craniocervical junction, and the upper cervical spinal canal that are anterolateral and at times intradural require access ventral to the cerebellum and spinal cord. The posterolateral transcondylar approach provides such a route. In addition, posterior craniocervical stabilization can be accomplished at the same time. The author has reviewed the technique as well as the surgical results here. Materials and methods  The posterolateral transcondylar approach to the craniocervical junction was utilized in children with schwannoma, meningioma, and chordoma affecting the cervicomedullary junction. Other entities such as neurenteric cysts and hemangioblastoma were also seen. Extradural tumors such as aneurysmal bone cysts of the atlas and the axis vertebrae as well as proatlas segmentation abnormalities and bone tumors were seen. The stability of the craniocervical junction was assessed preoperatively so that a fusion procedure could be accomplished at the same operative setting, if necessary. Preoperative evaluation of the lower cranial nerves was vital. The surgical procedure was accomplished in the prone position. The occipital bone removal was carried out up to the sigmoid sinus and toward the jugular bulb. Relocation of the vertebral artery was made at the atlas vertebra and thus provided posterolateral exposure into the posterior fossa and upper cervical spinal canal. Occipital condyle removal was limited to one-third of the medial occipital condyle. Results  Twenty-five children underwent a posterolateral transcondylar approach. New lower cranial nerve dysfunction occurred in two and only one required a tracheostomy. This was seen in a child with clivus chordoma. A complete removal was accomplished in meningioma and schwannoma as well as in neurenteric cyst and hemangioblastoma. Clivus chordomas required more than one surgical procedure. The tumors of the bone were all treated with simultaneous fusion. Conclusions  The posterolateral transcondylar route is a versatile avenue to approach a variety of lesions ventrolateral to the brain stem and upper cervical cord. Exposure is quite satisfactory with minimal or no retraction of important neurovascular structures in the region. Modifications of this theme can be applied as the lesions require.     

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.     

枕下远外侧经髁入路的显微外科解剖及临床应用

目的为枕下远外侧经髁入路提供较详细的解剖资料。方法应用16例（32侧）成人尸体头湿标本，15例干标本进行显微解剖测量。结果乳突尖、环椎横突、第2颈神经前支、枕骨髁及枕下三角都是重要的术中解剖标志。椎动脉第三段周围有丰富的静脉丛，是术中显露椎动脉时重要的出血来源。切除枕骨髁后内侧1／3，外科术野可扩大（15±1）°，切除1／2时术野扩大（18±1）°。应用此入路解剖学研究结果治疗枕骨大孔腹侧肿瘤5例，术后效果良好。结论枕下远外侧经髁入路解剖关系复杂，但可在不牵拉脑干的基础上充分显露枕骨大孔区腹侧，枕骨髁的切除范围仅限于其后内侧1／2。     

枕骨大孔区腹侧脑膜瘤的显微手术技术探讨

目的探讨远外侧入路在治疗枕骨大孔区腹侧脑膜瘤中的应用。方法对14例脑膜瘤患者采用远外侧入路显微手术治疗,其中枕髁后入路8例,经部分枕髁入路3例,经C1、2关节面侧方联合部分枕髁入路2例,经完整枕髁入路1例。结果肿瘤全切11例,次全切除3例;1例行枕颈融合,无手术死亡病例。所有患者术后均未出现寰枕关节不稳定的症状,手术并发症主要是后组颅神经损伤、椎动脉损伤、脑脊液漏以及脑干缺血。结论远外侧入路是手术治疗下斜坡区和上段颈髓腹侧、腹外侧病变的理想入路,可以理想显露肿瘤及其基底部并减少术中出血,但手术操作比较复杂且具有一定的风险。     

远外侧入路切除枕骨大孔区腹侧及腹外侧脑膜瘤的显微手术探讨(附11例报告)

目的探讨经远外侧入路切除枕骨大孔区腹侧及腹外侧脑膜瘤的显微手术技巧。方法自2003年5月至2010年5月经远外侧入路显微手术切除枕骨大孔区腹侧及腹外侧脑膜瘤11例,其中,经枕髁后入路5例,经部分枕髁入路4例,经C_1～2关节面侧方联合部分枕髁入路2例。结果肿瘤全切除（SimpsonⅠ、Ⅱ级）7例,次全切除（SimpsonⅢ级）3例,大部切除（SimpsonⅣ级）1例,无手术死亡病例。结论经远外侧入路显微手术切除枕骨大孔区腹侧及腹外侧脑膜瘤的关键在于:①合理设计磨除枕骨大孔侧方骨质的范围以充分暴露肿瘤;②术中注意保护脑干、上颈髓、后组颅神经及椎动脉等重要结构。     

Vertical atlantoaxial dislocation as a cause of failure of midline fixation

We report an 11-year-old girl who had previously undergone an operation for basilar invagination involving a foramen magnum decompression and midline wire fixation. After improving initially, her neurological condition worsened again. Repeated investigations showed a firm midline craniovertebral fixation and bone fusion. However, she was found to have a vertical mobile and reducible atlantoaxial dislocation. Treatment of the vertical dislocation by lateral mass fixation resulted in lasting relief from her symptoms. Vertical instability at the atlantoaxial joints needs to be identified and appropriately treated as it may be a cause of failure of midline fixation.     

Craniovertebral junction neoplasms in the pediatric population

INTRODUCTION: The incidence of tumors at the craniovertebral junction in the pediatric population is low. Because of the variable pathology and the rarity of these tumors, ideal therapies are only now being defined. MATERIALS AND METHODS: Thirty-eight children with tumors affecting the craniocervical junction were encountered between 1991 and 2006. These comprised neoplasms of osseous origin and neural extramedullary tumors. RESULTS AND DISCUSSION: Chordomas of the clivus and foramen magnum were seen in eight, fibrous dysplasia in four, aneurysmal bone cysts in four, eosinophilic granuloma affecting the atlas and axis vertebra in four, Ewing's sarcoma involving the atlas in two, osteoblastoma in two, neurenteric cysts in four, meningioma in five, schwannoma in two, and plexiform neurofibromas in three. The location of these tumors was predominantly ventral, and a very small number had a lateral or dorsal location. The ventral tumors included chordoma, meningioma, fibrous dysplasia, aneurysmal bone cyst, and osteoblastoma. Plexiform neurofibroma affecting the craniocervical junction was ventral to the clivus and upper cervical spine causing severe kyphosis of the craniocervical region. Pain in the head and neck occurred in 70%. Paresthesias and dysesthesias in the hands were seen in 40% and spastic weakness of extremities in 22%. Cranial nerve palsies were seen in 33%. Twenty-eight percent of children showed dysphagia or dysarthria. The cranial nerves affected were the vagus followed by hypoglossal and glossopharyngeal nerves. This led to dysphagia, slurred speech, repeated aspiration pneumonia, and weight loss. The most common findings for chordomas at the craniocervical junction were isolated hypoglossal nerve palsy. All individuals underwent magnetic resonance imaging, computed tomography, and 3D computed tomography and angiography. Vertebral angiography was used to understand the dynamics of collateral circulation and tumor vascularity. Tumor embolization was performed in chordoma and aneurysmal bone cysts. Our experience and results are presented here.     

远外侧锁孔入路切除枕骨大孔腹侧区肿瘤临床研究

目的 采用显微锁孔入路切除枕骨大孔腹侧区肿瘤，重点探讨手术入路及手术技巧。方法 总结我院1999年6月至2006年6月采用显微锁孔入路切除8例枕骨大孔腹侧区肿瘤的经验。手术入路：远外侧经髁后入路5例，远外侧经髁入路3例。结果8例肿瘤全切除6例，次全切除2例，无一例死亡。结论 远外侧入路是切除枕骨大孔腹侧区肿瘤的最佳手术入路。经髁后和部分经髁锁孔入路足够暴露和切除枕骨大孔腹侧区肿瘤。     

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.     

远外侧入路不同部位骨质切除与显露范围的对比研究

目的 量化分析枕下远外侧入路中不同部位骨质切除与其相对应的显露范围的差别.方法 15例(30侧)经福尔马林固定的成人头颅湿标本模拟基础远外侧入路,行骨窗成形后分为3组:分别模拟经髁入路、髁旁人路及髁上入路,比较其对应的显露范围.结果 基础远外侧入路对斜坡方向显露范围为(15.77±1.67) mm,对枕骨大孔前缘向侧方的显露范围为(-1.85±0.63) mm,距颈静脉孔后缘手术距离为(11.23±0.46) mm,距枕骨大孔前缘的手术距离为(21.78±1.49) mm.与基础远外侧入路比较,经髁入路显著增加斜坡方向和枕骨大孔前缘方向的显露范围,明显缩短距枕骨大孔前缘的手术距离(P＜0.05);髁旁入路明显缩短距颈静脉孔后缘的手术距离(P＜0.05);髁上入路显著增加斜坡方向的显露范围(P＜0.05).结论 磨除枕髁可显著增加枕骨大孔腹侧和下斜坡的显露,磨除颈静脉结节可显著增加中斜坡的显露,磨除髁旁骨质可显著增加颈静脉孔区的显露.     

远外侧锁孔入路切除枕骨大孔区脑膜瘤显微手术体会

目的探讨采用显微锁孔入路切除枕骨大孔区脑膜瘤的手术入路及手术技巧。方法我院1999年6月至2006年6月采用显微锁孔入路切除10例枕骨大孔区脑膜瘤，其中远外侧经髁后入路5例，远外侧经髁入路3例，枕下中线入路2例。结果10例肿瘤全切除8例，次全切除2例，无死亡病例。结论远外侧经髁后和部分经髁锁孔入路是切除枕骨大孔区脑膜瘤的最佳手术入路，术中应注意避免损伤椎动脉及其分支，保护后组颅神经。     

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.     

枕下极外侧入路的显微解剖及临床应用

目的探讨枕下极外侧入路相关的显微解剖及临床应用效果。方法采用福尔马林固定的成人头颅标本12例和28例成人干性颅骨标本进行模拟枕下极外侧入路的显微解剖学研究和相关参数的测量。并临床应用切除斜坡下段和枕骨大孔区肿瘤21例。结果乙状窦、枕髁和椎动脉是该入路重要的解剖标志。乳突尖到枕髁外缘中点为29.56±3.24mm;枕髁后缘距舌下神经管内口为12.23±3.13mm。临床应用该入路切除斜坡下段和枕骨大孔区肿瘤21例,肿瘤全切8例,次全切除9例,大部切除4例,无手术死亡。结论采用枕下极外侧入路可以增加术野空间,减少对脑干和重要血管神经的牵拉,是较为理想的手术入路。     

远外侧经髁入路到颈静脉孔区的国人显微解剖

目的:探讨远外侧经髁入路到颈静脉孔区的显微解剖结构,为颈静脉孔区手术入路提供解剖学基础。方法:对10例经福尔马林固定的成人湿性头颅标本和10例成人头颅骨标本进行解剖学观察,通过模拟该手术入路对颈静脉孔区的重要解剖标志进行描述和测量。结果:颈静脉孔内口距内耳门为4.54±0.88mm;颈静脉孔内口距舌下神经管内口为9.06±1.24mm;舌下神经管内口到枕骨髁后缘的距离是10.08±0.76mm;舌下神经管内口到颈静脉结节的距离是7.22±1.44mm;该手术入路的关键是枕髁的正确磨除和椎动脉的安全显露,并且在手术过程中要注意小脑前下动脉的变异。结论:通过远外侧经髁入路可以较好地从后方暴露颈静脉孔区及其毗邻结构,避免了颞骨岩部的磨除,面神经的移位,减少了神经损伤等不利因素。