Angular craniometry in craniocervical junction malformation

The craniometric linear dimensions of the posterior fossa have been relatively well studied, but angular craniometry has been poorly studied and may reveal differences in the several types of craniocervical junction malformation. The objectives of this study were to evaluate craniometric angles compared with normal subjects and elucidate the main angular differences among the types of craniocervical junction malformation and the correlation between craniocervical and cervical angles. Angular craniometries were studied using primary cranial angles (basal and Boogard’s) and secondary craniocervical angles (clivus canal and cervical spine lordosis). Patients with basilar invagination had significantly wider basal angles, sharper clivus canal angles, larger Boogard’s angles, and greater cervical lordosis than the Chiari malformation and control groups. The Chiari malformation group does not show significant differences when compared with normal controls. Platybasia occurred only in basilar invagination and is suggested to be more prevalent in type II than in type I. Platybasic patients have a more acute clivus canal angle and show greater cervical lordosis than non-platybasics. The Chiari group does not show significant differences when compared with the control, but the basilar invagination groups had craniometric variables significantly different from normal controls. Hyperlordosis observed in the basilar inavagination group was associated with craniocervical kyphosis conditioned by acute clivus canal angles.     

Skull base abnormalities in osteogenesis imperfecta: a cephalometric evaluation of 54 patients and 108 control volunteers

OBJECT: Osteogenesis imperfecta (OI), which usually results from mutations in type I collagen genes, causes bone fragility and deformities. The head is often abnormally shaped, and changes in skull base anatomy in the form of basilar impression and basilar invagination have been reported. The authors analyzed the skull base anatomy on standardized lateral cephalograms from 54 patients with OI (Types I, III, and IV) and 108 control volunteers. They were surprised to find that the previously used diagnostic measures for basilar abnormality in patients with OI were exceeded in 6.5 to 7.4% of the controls, and hence needed to be reevaluated. METHODS: The authors calculated the distance from the odontoid process to four reference lines, including a novel one, in the controls. The normal mean distances were exceeded by more than two standard deviations (SDs) in 28.3 to 35.2%, and by more than three SDs in 13.2 to 16.6% of the patients with OI. The latter figures reliably reflect the prevalence of basilar impression. As a sign of basilar invagination the odontoid process protruded into the foramen magnum or reached the foramen magnum level in 22.2% of the patients with OI, whereas none of the controls showed this feature. Platybasia (an anterior cranial base angle > 146 degrees) was present in 11.1% of the patients but in none of the controls. CONCLUSIONS: Platybasia, basilar impression, and basilar invagination were often coexpressed, but each was also present as an isolated abnormality. These three abnormalities and wormian bones were predominantly found in OI Types III and IV as well as in patients exhibiting dentinal abnormality.     

A retrospective study of congenital osseous anomalies at the craniocervical junction treated by occipitocervical plate-rod systems

Purpose

To evaluate the effectiveness of posterior occipitocervical reconstruction using the anchors of cervical pedicle screws and plate-rod systems for patients with congenital osseous anomalies at the craniocervical junction.

Methods

Twenty patients with congenital osseous lesions who underwent posterior occipitocervical fusion using the anchors of cervical pedicle screws and plate-rod systems for reduction and fixation from 1996 to 2009 were reviewed. The lesions included os odontoideum, occipitalization of the atlas, congenital C2–3 fusion, congenital atlantoaxial subluxation, congenital basilar invagination and combined anomalies. The clinical assessment and the measurements of the images were performed preoperatively, postoperatively and at most recent follow-up.

Results

The combined deformity of flexion of the occipitoatlantoaxial complex and invagination of the odontoid process associated with congenital osseous lesions at the craniocervical junction was corrected by application of combined forces of extension and distraction between the occiput and the cervical pedicle screws. Preoperative myelopathy improved in 94.7 % patients. The mean Ranawat value, Redlund-Johnnell value, atlantodental distance, occiput (O)–C2 angle, and C2–C7 lordosis angle improved postoperatively and was sustained at most recent follow-up. The mean cervicomedullary angle improved from 129.3° preoperatively to 153.3° postoperatively. The mean range of motion at the lower adjacent motion segment remained unchanged at most recent follow-up. The fusion rate was 95 %.

Conclusions

The results of the present study indicate that posterior occipitocervical reconstruction using the anchors of cervical pedicle screws and plate-rod systems is an effective technique for treatment of deformities and/or instability caused by congenital osseous anomalies at the craniocervical junction.     

Utility of three-dimensional computed tomographic angiography for assessment of relationships between the vertebrobasilar system and the cranial base

OBJECTIVE: The optimal surgical exposure for basilar tip aneurysms is dictated by the relationship of the basilar bifurcation to the cranial base. This study was designed to evaluate three-dimensional computed tomographic angiography as a means of obtaining detailed anatomic information on the basilar artery and the surrounding cranial base in individual patients before surgery. METHODS: We studied 30 patients using three-dimensional computed tomographic angiographic reconstructions from 1-mm computed tomographic slices. Detailed anatomic measurements were performed to define the relationship between the basilar artery and the cranial base. Particular attention was paid to the height of the dorsum sellae and its relationship to the basilar bifurcation. RESULTS: The heights of the basilar apex and the vertebrobasilar junction, relative to the cranial base, were extremely variable. Considerable asymmetries in the heights of the left and right posterior clinoid processes were identified; in one case, this difference was more than 1 cm (mean difference in height, 0.9 mm; range, 0-10.3 mm). The heights of the posterior clinoid processes above the sellar floor ranged from 5.8 to 14.1 mm (mean height, 9.5 mm). We were able to determine the feasibility of the pterional/orbitozygomatic, middle fossa/ anterior petrosal, and presigmoid retrolabyrinthine approaches to an individual basilar bifurcation. We also estimated the amount of bone removal required and determined the operative distances via those approaches. CONCLUSION: Three-dimensional computed tomographic angiography is a useful tool for assessing critical anatomic relationships and represents an adjunct to conventional angiography in the planning of individualized, precisely tailored, cranial base approaches to the vertebrobasilar system.     

Magnetic resonance imaging study of the craniocervical junction

PURPOSE: To confirm the accuracy of the standard parameters of Chamberlain's line, McGregor's line, McRae's line, and Ranawat's line in the diagnosis of basilar impression in a normal Asian population using magnetic resonance imaging (MRI) scans of the craniocervical junction, and to evaluate the use of MRI in the initial diagnosis of basilar impression. METHODS: We retrospectively reviewed MRI scans of the craniocervical junction in 114 Thai patients (61 men and 53 women) aged 20 to 89 years to assess the lines of Chamberlain, McGregor, McRae, and Ranawat. Patients with injury, tumour, or metastasis in the craniocervial junction; congenital anomalies; or clinical symptoms and signs of basilar impression were excluded. RESULTS: 39 of the 114 patients had the odontoid tip extended above Chamberlain's line by 1 mm to 9 mm (mean, 2.89 mm). Only 7 men and 5 women had the tip of the odontoid process extended beyond the normal range of 5 mm. The mean distance of the odontoid tip extended past McGregor's line in male and female subjects was 0.33 mm (standard deviation [SD], 1.2 mm) and 0.17 mm (SD, 0.7 mm), respectively, markedly less than those reported previously, although one male patient's odontoid tip extended 8 mm above the McGregor's line. Regarding McRae's line, no patient had the odontoid tip extended above the foremen magnum. The mean Ranawat's line in male and female subjects was 15.75 mm (range, 12-19; SD, 1.71 mm) and 14.09 mm (range, 11-17; SD, 1.38 mm), respectively. CONCLUSION: After using MRI to confirm the standard parameters of basilar impression as previously formulated from lateral skull radiographs, we recommend using McRae's line and Ranawat's line in the initial screening for basilar impression for the Asian population. Chamberlain's line and McGregor's line are viable alternatives, but clinicians must be aware of the potential for false positives.     

Treatment of basilar invagination

Purpose

Basilar invagination is a rare craniocervical malformation which may lead to neurological deficits related to compression of brainstem and upper cervical cord as well as instability of the craniocervical junction. This study presents results of a treatment algorithm developed over a 20-year period focussing on anatomical findings, short-term and long-term outcomes.

Methods

69 patients with basilar invagination (mean age 41 ± 18 years, history 64 ± 85 months) were encountered. The clinical courses were documented with a score system for individual neurological symptoms for short-term results after 3 and 12 months. Long-term outcomes were analyzed with Kaplan–Meier statistics.

Results

Patients with (n = 31) or without (n = 38) ventral compression were distinguished. 25 patients declined an operation, while 44 patients underwent 48 operations. Surgical management depended on the presence of ventral compression and segmentation anomalies between occiput and C3, signs of instability and presence of caudal cranial nerve dysfunctions. 16 patients without ventral compression underwent foramen magnum decompressions without fusion. 19 patients with ventral compression and abnormalities of segmentation or evidence of instability underwent a foramen magnum decompression with craniocervical (n = 18) or C1/2 (n = 1) stabilization. In nine patients with severe ventral compression and caudal cranial nerve deficits, a transoral resection of the odontoid was combined with a posterior decompression and fusion. Within the first postoperative year neurological scores improved for all symptoms in each patient group. In the long-term, postoperative deteriorations were related exclusively to instabilities either becoming manifest after a foramen magnum decompression in three or as a result of hardware failures in two patients.

Conclusions

The great majority of patients with basilar invagination report postoperative improvements with this management algorithm. Most patients without ventral compression can be managed by foramen magnum decompression alone. The majority of patients with ventral compression can be treated by posterior decompression, realignment and stabilization alone, reserving anterior decompressions for patients with profound, symptomatic brainstem compression.     

Management of the vertebral artery at the craniocervical junction.

OBJECTIVES: To study the surgical anatomy of the vertebral artery at the craniocervical junction and its related structures defining reliable landmarks for its safe exposure. DESIGN: Ten sides of 5 fresh cadavers were dissected using the lateral approach to the craniocervical junction. RESULTS: Experience gained in studying the anatomic details of the vertebral artery at the craniocervical junction in cadavers from its exit at the transverse foramen of the second cervical vertebra to the vertebrobasilar junction provided the initial background for us to use the lateral approaches to the skull base to safely manage 4 cases with pathology reaching the close vicinity of vertebral artery at the craniocervical junction. CONCLUSION: Thorough knowledge of the anatomy of the vertebral artery is mandatory before attempting surgery at the craniocervical junction. There are reliable landmarks that, when followed, could facilitate safe exposure and identification of the artery.     

Craniocervical junction malformation treated by transoral approach. A survey of 25 cases with emphasis on postoperative instability and outcome

Summary An experience with 25 consecutive cases of craniocervical junction (CCJ) malformations operated upon via the transoral route is reported. Twenty-two patients also underwent posterior occipitocervical stabilization with alloplastic material and in only one patient was transoral odontoidectomy and fusion with bone autograph performed.Indication for the transoral route consisted of an irreducible ventral compression of the cervicobulbar junction by the abnormal bone complex.Two patients died during the early postoperative period and the remaining 23 survivors were followed for an average of 3.5 years: 17 of these showed marked improvement and 5 a stabilization of the neurological disturbances. A further patient, who refused posterior stabilization, eventually died because of progressive cranial settling.Long-term results have shown this approach to be decisive in the surgical management of well-selected CCJ anomalies.     

Transoral-transpharyngeal approach to the anterior craniocervical junction. Ten-year experience with 72 patients

The anterior transoral-transpharyngeal operation to correct ventral irreducible compression of the cervicomedullary junction was utilized in 72 individuals. The patients' ages ranged from 6 to 82 years, and 29 were children. The pathology encountered was primary basilar invagination, rheumatoid irreducible cranial settling, secondary basilar invagination due to migration of odontoid fracture fragments, dystopic os odontoideum, granulation masses, clivus chordoma, osteoblastoma, and chondroma of the atlas. Fifteen patients had associated Chiari malformation with basilar invagination. Fifty-two patients required subsequent atlantoaxial or occipitocervical fusion. Neurological improvement was the rule. There were two deaths within 30 days of surgery: one from myocardial infarction 4 weeks after surgery and one from Gram-negative septicemia of urinary tract origin. There was one pharyngeal wound infection. The ventral transoral approach provides a safe, rapid, and effective means for decompression of the abnormal craniovertebral junction.     

Surgical management of vertebral and basilar artery aneurysms: a single center experience in 41 patients

Objective

To study an effective method for surgical management of vertebral and basilar artery aneurysms.

Methods

Forty-one patients with 43 aneurysms of the vertebral and basilar arteries were managed by microsurgical clipping. Cerebral angiography revealed basilar apex aneurysms in 17 patients, basilar trunk in six patients, vertebrobasilar (VB) junction aneurysms in three patients and vertebral aneurysms in 15 patients. One patient had two basilar aneurysms, and another had bilateral vertebral artery aneurysm.

Surgical technique

We used a pterional approach in basilar apex aneurysms (n?=?17 patients), orbitozygomatic and its variants in upper basilar trunk aneurysms (n?=?2 patients), combined petrosal and far-lateral approach in mid basilar trunk aneurysms (n?=?4 patients), far-lateral and transcondylar approach for the aneurysms at VB junction (n?=?3 patients) and transcondylar approach for the vertebral aneurysms (n?=?15 patients). Bypass graft was performed in 14 patients with fusiform and wide neck aneurysms, to prevent potential cerebral ischemia due to prolonged temporary occlusion or possibility of intraoperative parent artery sacrifice.

Results

Neurological outcomes were measured on the basis of Glasgow Outcome Score (GOS). The rate of back-to-normal life after surgery in basilar tip aneurysm, basilar trunk aneurysms, VB junction aneurysms and vertebral artery aneurysms was 15/17 (82.5 %), 5/6 (83 %), 3/3 (100 %) and 14/15 (93.3 %), respectively. Thirty-six (87.8 %) patients had uneventful postoperative courses. Two patient with basilar apex aneurysm suffered severe neurological deficits related to midbrain ischemia, two patient with occipital artery (OA) graft bypass had postoperative partial lower cranial nerve palsy, and one death with basilar trunk aneurysm occurred after the 20th day of surgery. Thirty-nine patients accepted postoperative digital subtraction angiography (DSA) and eight patients accepted computed tomography (CT) angiogram, whereas two patient denied either one. All the images demonstrated afferent and efferent vessels without aneurysm in situ. Out of 14 patients with graft bypass, 11 patients on cerebral angiographies disclosed the aneurysm clip and the graft bypass patency, one patient on angiography had unidentified graft bypass patency but no symptom related to the graft bypass patency, and two patients denied the postoperative cerebral angiographies. In 40 patients with a mean follow-up of 3.4 years, 37 patients had good outcome, two patients needed assistance for daily living, and one death occurred due to brainstem infarction related to surgery.

Conclusion

Selection of proper cranial base approach with adequate exposure is effective in clipping VB aneurysms, minimizing the postoperative complications. Graft bypass may avoid parent artery sacrifice and its branches occlusion in patients with fusiform and wide neck aneurysms.     

Spinal complications in osteogenesis imperfecta 47 patients 1-16 years of age

We examined in a cross-sectional study, 47 children (mean age 7.7 (1-16) years) with osteogenesis imperfecta (OI) to find the prevalence of spinal deformities and to correlate these observations with anthropometry. The associations between dentinogenesis imperfecta, joint hypermobility and spinal deformities were also studied.

Disproportion in stature in OI type I and type IV was mainly caused by spinal involvement, as evidenced by a greater decrease in body height than in leg length. In OI type I, the decrease in sitting height was mainly caused by platyspondyly, whereas in OI types III and IV, it was also caused by progressive scoliosis and kyphosis. Scoliosis was present in 22 children, and pathological kyphosis in 18, mainly in the severe OI types. Basilar impression was observed in 10 children, mainly in type III.

Children with dentinogenesis imperfecta seemed to be prone to develop scoliosis, pathological kyphosis and basilar impression. Children with generalized joint hypermobility were less prone to develop scoliosis and basilar impression. Our observations may contribute to a better understanding of the risk factors for progressive spinal deformities in OI.     

Giant prebulbomedullary arachnoid cyst. Case report and review of the literature

Usual locations of arachnoid cyst are the middle cranial fossa in 50-60%, cerebellopontine angle (10%) and suprasellar area (10%). Most of these malformations are asymptomatic. Premedullar arachnoid cysts are extremely rare. All previous cases reported were operated. We report a case of an asymptomatic giant craniocervical junction arachnoid cyst with a follow up of five years. In 2002, an adolescent consulted for persistent cervical pain. Encephalic MR showed a giant ventral craniocervical junction arachnoid cyst. Neurologic examination was normal. Conservative treatment was decided with a clinical follow up and repeated MR in case of persistent cervicalgia. Craniocervical junction arachnoid cysts are anecdotic. Medical care cannot be standardized. Pathogenesis and management are discussed.     

颅颈病变经口显微外科手术

目的：回顾性分析经口显微外科治疗颅颈病变的疗效。方法：应用显微外科治疗颅颈区病变１０例，其中９例为颅底陷入症，１例为齿状突骨折，全部采用经口咽显微镜下进行手术。结果：５例术后肢体恢复正常功能，３例病情明显改善，１例有改善，１例手术后一周死于肺部感染。结论：精细的显微外科手术是可以避免伤口感染和脑脊液渗漏。     

Static and dynamic bone histomorphometry in children with osteogenesis imperfecta

Osteogenesis imperfecta (OI) is a genetic disorder characterized by increased bone fragility and low bone mass. Four clinical types are commonly distinguished. Schematically, type I is the mildest phenotype, type II is usually lethal, type III is the most severe form compatible with postnatal survival, and type IV is moderately severe. Although mutations affecting collagen type I are responsible for the disease in most patients, the mechanisms by which the genetic defects cause abnormal bone development have not been well characterized. Therefore, we evaluated quantitative static and dynamic histomorphometric parameters in tetracycline-labeled iliac bone biopsies from 70 children, aged 1.5 to 13.5 years, with OI types I (n = 32), III (n = 11), and IV (n = 27). Results were compared with those of 27 age-matched controls without metabolic bone disease. Biopsy core width, cortical width, and cancellous bone volume were clearly decreased in all OI types. Decreased cancellous bone volume was due to a 41%–57% reduction in trabecular number and a 15%–27% lower trabecular thickness. Regression analyses revealed that trabecular number did not vary with age in either controls or OI patients, indicating that no trabecular loss occurred. The annual increase in trabecular thickness was 5.8 μm in controls and 3.6 μm in type I OI, whereas no trabecular thickening was evident in type III and IV OI. Wall thickness, which reflects the amount of bone formed during a remodeling cycle, was decreased by 14% in a subgroup of 17 type I OI patients, but was not determined in the other OI types. The remodeling balance was less positive in type I OI than in controls, and probably close to zero in types III and IV. Surface-based parameters of bone remodeling were increased in all OI types, indicating increased recruitment of remodeling units. No defect in matrix mineralization was found. In conclusion, there was evidence of defects in all three mechanisms, which normally lead to an increase in bone mass during childhood; that is, modeling of external bone size and shape, production of secondary trabeculae by endochondral ossification, and thickening of secondary trabeculae by remodeling. Thus, OI might be regarded as a disease in which a single genetic defect in the osteoblast interferes with multiple mechanisms that normally ensure adaptation of the skeleton to the increasing mechanical needs during growth.     

An Unrecognized Ligament and its Ossification in the Craniocervical Junction: Prevalence,Patient Characteristics,and Anatomic Evidence

BackgroundIn the craniocervical junction, the ligaments between the anterior foramen magnum and the anterior arch of the atlas are not well defined, and ossification of the ligaments in this region has rarely been reported. Characterizing the anatomy and ossification of these ligaments may help in the diagnosis and treatment of disorders in this region.Questions/purposes(1) What is the prevalence of an unrecognized ossification at the craniocervical junction in patients with cervical spine disorders, and what are the patient characteristics associated with this ossification? (2) Do patients with this ossification have a greater risk of ossification of other structures at the craniocervical junction or cervical spine? (3) Is there an unreported ligament at this ossified site?MethodsWe conducted a retrospective study of 578 hospitalized patients who underwent CT for cervical spine disorders between January 2016 and July 2020. Based on the inclusion criteria, 11% (66 of 578) were excluded because of a cervical or craniocervical tumor, deformity, infection, fracture or dislocation, or prior surgery, leaving 89% (512 of 578) for analysis. These 512 patients had diagnoses of cervical radiculopathy, cervical myelopathy, cervical spondylotic amyotrophy, cervical spinal cord injury without a radiographic abnormality, or axial neck pain. Their mean age was 57 years (range 22-90 years), and 60% of the patients were men. Patient characteristics including age, gender, and diagnosis were retrieved from a longitudinally maintained institutional database. CT images were used to assess the presence of a previously unrecognized ossification and ossification of other structures in the craniocervical junction and cervical spine, including the posterior longitudinal ligament, anterior longitudinal ligament, nuchal ligament, ligamentum flavum, transverse ligament, and apical ligament, as well as diffuse idiopathic skeletal hyperostosis (DISH). The association between these structures was also assessed. This unreported ossification was called the capped dens sign. It was defined and graded from 1 to 3. Grade 3 was defined as the typical capped dens sign. Cervical spine MRI was used to assess whether there was an unreported structure in the same region as where the capped dens sign was detected on CT images. In the database of a recent study, there were 33 patients younger than 41 years. Nine percent (three of 33) were excluded because they did not have cervical spine MRI. MRIs of the remaining 30 patients were assessed. Their mean age was 35 years (range 22-40 years), and 58% were men. All cervical spine CT images and MRIs were reviewed by one senior spine surgeon and one junior spine surgeon twice with a 2-week interval. Blinding was accomplished by removing identifying information from the radiographs and randomly assigning them to each examiner. Any discrepancy with respect to the grade of the capped dens sign was adjudicated by a third blinded senior spine surgeon. Intrarater and interrater reliabilities were assessed by calculating weighted kappa statistics. No ligament or membrane was reported at this site. MRI is not sensitive to identify thin tissue in this region, especially when severe degeneration has occurred. A cadaveric study was conducted to discover a potential ligament between the inferior margin of the foramen magnum and the anterior arch of the atlas, as prompted by the newly discovered ossification in the clinical analysis of this study. Six embalmed human cadaveric craniocervical regions (three male and three female cadavers; median age 56 years, range 45-78 years) were dissected by a senior anatomist and a senior anatomy technician. A mid-sagittal section of the craniocervical junction was created, allowing us to explore the interval between the anterior foramen magnum and anterior arch of the atlas. A histologic analysis was conducted in two of the six cadavers (a male cadaver, 45 years; and a female cadaver, 51 years). Slides were made with 4-µm sections and stained with hematoxylin and eosin.ResultsA novel capped dens sign was detected in 39% (198 of 512) of the patients and the most typical capped dens sign was detected in 19% (96 of 512) of patients. The prevalence of this sign was the highest in patients with cervical spondylotic amyotrophy (12 of 25 patients). The prevalence of ossification of the anterior longitudinal ligament, ligamentum nuchae, and apical ligament, as well as DISH, was higher in patients with a capped dens sign than in those without (p = 0.04, p < 0.001, p < 0.001, and p = 0.001, respectively). The capped dens sign was identified in 69% (18 of 26) of the patients with DISH. A thin and short band-like structure or osteophyte was detected on MRI in 87% (26 of 30), in the same region as the capped dens sign. In the cadaveric study, an unreported, distinct ligamentous structure was identified at this ossified site. It originated from the posterosuperior rim of the anterior arch of the atlas to the inferior margin of the foramen magnum, which we called the inter-atlanto-occipital ligament. It was found in all six dissected craniocervical junctions. The histologic analysis revealed dense connective tissue.ConclusionMore than one-third of the patients in this series demonstrated CT evidence of a previously unrecognized ossification in the craniocervical junction, which we called the capped dens sign. Anatomic evidence of this sign, which was a previously unidentified ligament, was also newly discovered in this region. This study was conducted among Asian patients and specimens. Further studies among diverse ethnic groups may be needed to generalize the results. An additional well-designed prospective study will be needed to provide further evidence regarding the potential pathophysiology and clinical relevance of the capped dens sign. Furthermore, the cadaveric analysis in this study was only a preliminary report of the ligament; further biomechanical research is needed to investigate its function.Clinical RelevanceKnowledge of this novel ligament may improve the diagnosis and treatment of craniocervical stability and dislocation. Ossification of this ligament is correlated with age, cervical spondylotic amyotrophy, and DISH. We wonder whether patients with cervical degenerative disorders who also have a capped dens sign may be at risk for the formation of osteophytes of an uncovertebral joint, which may result in palsy of the upper limb muscles. The capped dens sign may be the craniocervical manifestation of DISH. This possible association between the capped dens sign and DISH should be considered when performing surgery on patients with the capped dens sign.     

颅脊交界疾患经口手术的枕寰枢置钉策略

目的:探讨颅脊交界疾患经口手术枕寰枢螺钉固定的置钉策略.方法:2010年1月～2010年12月,30例颅脊交界疾患病例(包括寰枢椎脱位12例,颅底凹陷症15例和先天性颅脊交界畸形3例)均采用第三代经口寰枢椎复位钢板(transoral atlantoaxial reduction plate-Ⅲ,TARP-Ⅲ)内固定植骨融合手术进行治疗.患者术前均有颈部不适和不同程度的肢体麻木、无力等高位脊髓受压表现,影像学检查均存在脊髓腹侧受压.按美国脊髓损伤协会(American Spinal Injury Association,ASIA)分级:C级5例,D级25例.ASIA运动评分为42～96分,平均77.2±14.4分.所有病例均通过计算机辅助设计快速成型(computer aided design and rapid prototype,CAD-RP)技术制作颅脊交界区的1∶1三维模型实物,13例复杂病例术前在模型实物上模拟手术进钉.枕寰枢螺钉的选择主要采用四种方法:A,C0/C1融合者(存在先天性寰椎枕骨化畸形的患者)采用寰椎侧块枕骨髁融合体螺钉;B,C0/C1未融合者(C1侧块完整的患者)采用寰椎侧块螺钉;C,无颅底凹陷且枢椎椎弓根发育正常的患者采用枢椎经口逆向椎弓根螺钉;D,存在颅底凹陷或虽无颅底凹陷但枢椎椎弓根发育狭小或存在椎动脉高跨等无法置入椎弓根螺钉的患者,采用枢椎经口逆向关节突螺钉.本组颅底凹陷症患者TARP-Ⅲ内固定时采用AC或AD的螺钉组合,寰枢椎脱位和先天性颅脊交界畸形患者采用BC或BD的螺钉组合,从而形成TARP固定的4种螺钉组合方式:AC、AD、BC或BD.随访观察治疗效果.结果:30例患者术后颈部局部症状和肢体麻木无力症状均不同程度改善,无感染、神经血管损伤、钉板松脱等并发症发生,2例术后有短暂头晕,术后2周～1个月自愈.术后影像学检查内固定位置满意,脊髓压迫均彻底解除.术后25例ASIA分级D级患者中的8例改善至E级,其余17例分级无变化,但术后运动评分改善至87～100分(96.4±4.2分);5例C级患者均改善至D级.术后随访3～12个月,平均7.2个月,所有病例均获骨性融合,30例计120枚螺钉(包括寰椎侧块枕骨髁融合体螺钉30枚,寰椎侧块螺钉30枚,枢椎经口逆向椎弓根螺钉16枚和枢椎经口逆向关节突螺钉44枚)均位置理想.结论:不同的颅脊交界疾患病例行经口入路手术时,应选择不同的螺钉固定方法,通过枕寰枢螺钉的多种组合方式,可达到使TARP坚强固定寰枢关节的作用.     

Tussive presentation in cervicomedullary junction malformations

Two adult patients with craniocervical junction malformations presented with tussive symptom onset. These patients had acute onset of permanent neurologic symptoms. One patient had basilar invagination with tonsilar herniation and the second, a Type 1 Arnold-Chiari malformation with cord widening. Possible mechanisms include: 1) external compression of cervicomedullary structures by posterior fossa tissue that had descended through the foramen magnum secondary to increased intracranial pressure, and 2) parenchymal shear stress secondary to this caudal repositioning of these structures.     

Relevance of the cranioaxial angle in the occipitocervical stabilization using an original construct: a retrospective study on 50 patients

We present a retrospective study on a series composed of 50 patients, treated between 1992 and 2006, affected by pathologies of the craniocervical junction. All the patients were treated using an innovative procedure based on a cranial claw made up of low profile hooks, conceived by one of the authors. Advantages of this technique are, to our point of view, a higher resistance to cranial hooks dislodgment, when compared with screw fixation instrumentation, especially in pathological conditions, such as rheumatoid arthritis that leads to a qualitative deterioration of the bone stock and to the reduction of the occipital wall thickness. Occipitoaxial alignment was assessed radiographically using the McGregor line. We observed an improvement in the subjective evaluation of pain in all treated patients with a 46% improvement from the initial values. Moreover, patient stabilized with an occipitoaxial angle included in the physiological range showed better results either for the survival of the instrumentation or the onset of junctional pathology. Patients have been followed up afterwards and evaluated by the visual analogue scale for the assessment of pain and by the Nurick scale for the cases associated with myelopathy. We believe that cranial anchorage with a hook claw allows for an instrumentation provided with high stability, particularly useful in revision surgery and major instabilities. The study of the occipitoaxial angles showed that the better results and the long-lasting stability of the implant are correlated to a fusion angle included in the physiological range.     

Halo traction in basilar invagination: technical case report

BACKGROUND: In the management of basilar invagination, traction therapy may help by pulling down the odontoid process away from the brain stem that may result in clinical and radiological improvement. We aimed to discuss the role of the halo vest apparatus traction on the reduction of severe anterior compression pathologies in basilar invagination. CASE DESCRIPTION: We describe a simple and safe cervical traction method by the halo vest apparatus that is followed by rigid posterior occipitocervical fixation and foramen magnum decompression in a patient who presented with basilar invagination and symptoms of severe brain stem compression. An MR-suitable halo vest apparatus was used for reduction of the deformity. The reduction of the basilar invagination was achieved gradually by distracting the halo crown in stages. CONCLUSION: The halo vest apparatus can be safely used in complex craniocervical junction anomalies. An effective cervical traction can be performed in basilar invagination, and reduction of the deformity may be achieved without the risk of overdistraction. In some cases, even partial reduction of the deformity may facilitate brain stem and spinal cord relief without any need of posterior decompression. Patients may benefit from ambulatory functions because bed rest is eliminated in this procedure. Neurovascular structures and the degree of the reduction can be observed on MRIs when an MR-suitable device is used.