Biomechanical Study on Atlantoaxial Dislocation Combined with Basilar Invagination by Different Posterior Internal Fixation Methods / 医用生物力学

Objective To investigate biomechanical differences of two posterior occipitocervical internal fixation techniques for treating basilar invagination with atlantoaxial dislocation (BI-AAD). Methods Intra-articular cage + posterior occipital plate+C2 pedicle screw (Cage+C2PS+OP), and intra-articular cage+C1 lateral mass screw+C2PS (Cage+C1LMS+C2PS) models were established based on occipitocervical CT data of the BI-AAD and clinical operation scheme, and the stability of atlantoaxial joint and stress distribution characteristics of C2 endplate and implanted instruments under different motion states were analyzed. Results Compared with the Cage+C1LMS+C2PS model, the atlantoaxial range of motion ( ROM) under flexion, extension, lateral bending and axial rotation in the Cage+C2PS+OP model were reduced by 5. 26% , 33. 33% , 43. 75% , -5. 56% , and stress peak of screw-rod fixation system were reduced by 47. 81% , 60. 90% , 48. 45% , 39. 14% , respectively. Under two internal fixation modes, stresses of C2 endplate and cage were mainly distributed on the compressive side during the motion, and both the screw-bone interface and the caudal side of screw subjected to large loading. Conclusions Two internal fixation methods could provide similar stability. However, the stress concentration of screw-rod system was more obvious and the possibility of screw loosening and fracture was greater under Cage+ C1LMS+C2PS fixation.

Craniometric parameters for the evaluation of platybasia and basilar invagination on magnetic resonance imaging: a reproducibility study / Parâmetros craniométricos para platibasia e invaginação basilar na ressonância magnética: estudo de reprodutibilidade

Abstract Objective: The present study aims to perform a reproducibility study of the clivus-canal angle (CCA), Welcker's basal angle (WBA), and the distance from the odontoid process to Chamberlain's line (DOCL) on magnetic resonance imaging (MRI). Materials and Methods: Two medical students and two radiologists respectively evaluated 100 and 50 consecutive MRI scans of adult skulls, selected randomly. Each examiner, working independently and blinded to the previous results, performed readings for each patient on two different occasions. Measurements were performed in T1-weighted sequences acquired in the midsagittal plane. The levels of intraobserver reproducibility and interobserver agreement were evaluated by calculating the intraclass correlation coefficients (ICCs) and the corresponding 95% confidence intervals. Results: The mean values obtained by the examiners were 150° for the CCA, 130° for the WBA, and 2.5 mm for the DOCL. The ICC for interobserver agreement was 0.980, 0.935, and 0.967, for the CCA, WBA, and DOCL, respectively, for the students, compared with 0.977, 0.941, and 0.982, respectively, for the radiologists, and 0.980, 0.992, and 0.990, respectively, for all of the examiners together. In the analysis of intraobserver agreement, the ICC ranged from 0.929 to 0.959 for the CCA, from 0.918 to 0.964 for the WBA, and from 0.918 to 0.981 for the DOCL. Conclusion: The measurement of the CCA, WBA, and DOCL appears to show excellent intraobserver reproducibility and interobserver agreement on MRI.

Resumo Objetivo: Realizar um estudo de reprodutibilidade do ângulo clivocanal (ACC), ângulo basal de Welcker (ABW) e distância do odontoide à linha de Chamberlain (DOLC) em ressonância magnética (RM). Materiais e Métodos: Quatro examinadores, dois graduandos de medicina e dois radiologistas, avaliaram, respectivamente, 100 e 50 indivíduos adultos submetidos a RM de crânio, consecutiva e aleatoriamente. Cada um realizou duas leituras para cada paciente em diferentes ocasiões, de forma cega e independente. As análises de concordância intraobservador e interobservador foram realizadas pelo coeficiente de correlação intraclasse (CCI), com intervalo de confiança de 95%. Resultados: As medidas médias, considerando todos os examinadores, foram: ACC = 150°, ABW = 130°, DOLC = 2,5 mm. A análise interobservador entre os estudantes revelou CCI de 0,980, 0,935 e 0,967 para ACC, ABW e DOLC, respectivamente, e para os radiologistas, CCI de 0,977, 0,941 e 0,982, respectivamente. A análise interobservador entre estudantes e radiologistas revelou CCI de 0,980, 0,992 e 0,990, respectivamente. Em relação à análise intraobservador, as medidas do ACC tiveram CCI variando entre 0,929 e 0,959, ABW entre 0,918 e 0,964 e DOLC entre 0,918 e 0,981. Conclusão: ACC, ABW e DOLC obtiveram excelentes reprodutibilidades intraobservador e interobservador na RM.

Reduction of the atlantoaxial dislocation associated with basilar invagination through single-stage posterior approach: using Xuanwu occipital-cervical reduction surgical suite / 中华外科杂志

Objective@#To examine the effect of posterior reduction in atlantoaxial dislocation (AAD) associated with basilar invagination(BI) using Xuanwu occipital-cervical fusion system in single stage.@*Methods@#Thirty-seven AAD accompanied with BI cases treated at Department of Neurosurgery, Xuanwu Hospital, Capital Medical Universiy and the Second Hospital of Hebei Medical University were retrospective analyzed. There were 15 males and 22 females with age of (42.3±12.3) years (range: 18-69 years). All the cases had congenital osseous abnormalities, such as assimilation of atlas and abnormal cervical fusion. Anterior tissue was released through posterior route followed by cage implantation into facet joint and occipital-cervical fixation with cantilever technique. The clinical results were evaluated using Japanese Orthopedic Association scale(JOA) and the main radiological measurements including anterior atlantodental interval (ADI), the distance of odontoid tip above Chamberlain line, clivus-canal angle(CCA) and the length of syrinx were collected. The preoperative and postoperative JOA score and radiological measurements were compared by paired t-test.@*Results@#The mean JOA score of the patients increased from 10.5 to 14.4 at the one-year follow-up(t=14.3, P=0.00). Complete reduction of AAD and BI was achieved in 34 patients.The mean clivus-canal angle improved from (118.0±6.5) degrees preoperative to (143.7±5.0) degrees postoperative(t=6.2, P=0.00). Shrinkage of the syrinx was observed 1 week after surgery in 24 patients, and 6 months in 31 patients.Twenty-eight patients achieved bone fusion 6 months after surgery. All the patients achieved bone fusion 12 months after surgery. One-side vertebral artery occlusion was diagnosed in 1 case postoperatively for transient dizziness, and relieved in 2 weeks.Two patients developed moderate neck pain after surgery, and relieved in 1 month. No implant failure, spacer subsidence or infection was observed.@*Conclusions@#The treatment of AAD associated with BI using Xuanwu occipital-cervical fusion system from posterior approach in single stage is effective and safe. Cage implantation intraarticularly and fixation with cantilever technique achieve complete reduction in most cases.

Basilar invagination associated with chiari malformation type I: A literature review

Basilar invagination (BI) and Chiari malformation type I (CM-I) are very important anomalies that introduce instability and compression in the occipitocervical transition region and have complex clinical characteristics. These anomalies vary according to the affected structures. The present study revises current knowledge regarding the anatomy, anatomo-physiology, clinical manifestations, and radiological findings of these entities and the associated surgical treatment approaches. A bibliographic survey was performed through a search in the Medline, PubMed, SciELO, Science and LILACS databases. When associated, these craniovertebral malformations result in neurological deficits due to neural parenchyma compression; however, the presence of microtraumas due to repetitive lesions caused by the bulb and cervical marrow instability has been highlighted as a determinant dysfunction. Surgical treatment is controversial and has many technical variations. Surgery is also challenging due to the complex anatomical characteristics and biomechanics of this region. Nevertheless, advances have been achieved in our understanding of related mechanisms, and compression and atlantoaxial instability are considered key elements when selecting the surgical approach.

Direct Intraoperative Reduction of Basilar Invagination Associated with Atlantoaxial Subluxation ­ Technical Note

In the present article, we describe a technique of direct intraoperative reduction of congenital atlantoaxial subluxation associated with severe basilar invagination and atlas assimilation. It consists of a wide dissection of the craniovertebral junction, exposing the region between the superior facet of C2 and the occiput (described as a "pseudoarticulation" by some authors). After exposure, a self-rotating small dissector or Kobe is used bilaterally, pushing C2 anteriorly and inferiorly, with reduction of the dislocation, followed by craniovertebral fixation. The technique is safe and eliminates the need for an anterior approach to the odontoid reduction, as well as the need to dissect the C1­2 joint.

Neste artigo, descrevemos a técnica de redução intraoperatória direta de subluxação atlantoaxial congênita associada a invaginação basilar grave e assimilação do atlas. Ela consiste em ampla dissecção da junção craniovertebral, expondo a região entre a face superior da C2 e o osso occipital (descrita como uma "pseudoarticulação" por alguns autores). Após exposição, um descolador pequeno ou Kobe é usado bilateralmente com rotação própria, deslocando C2 anterior e inferiormente, com redução da luxação, seguido de fixação craniovertebral. A técnica é segura e elimina a necessidade de uma abordagem anterior para a ressecção do odontoide, além de evitar a dissecação da junta C1­C2.

Management of a Complex Basilar Invagination Case with Multiple Revision Surgeries ­ Case Report

We describe a Basilar Invagination (BI) case with craniocervical instability and many previous failure surgeries and poor wound coverage. The patient had been submitted to a large posterior fossa craniectomy (which greatly limited the availability of an adequate area for bone fixation) and showed a poor quality of the surgical wound in the posterior craniocervical region. We performed an occipito-cervical fixation, using the bone overlying the torculla as a point of cranial fixation. Craniocervical realignment was achieved by the use of distractive maneuvers with occipital rods, followed by coverage of the hardware via a pedicled longitudinal trapeze myocutaneous flap. We used local ribs removed from the region where the myocutaneous flap was harvested as autologous bone grafts for craniocervical fusion. Post-operatively, the patient was placed in a halo-vest for three months. The patient improved substantially after the procedure, recovered some muscular strength and experienced total relief of her pain. We hereby discuss the surgical strategy used for treating this complex case in details, with illustrative pictures.

Descrevemos caso de paciente com diagnóstico de invaginação basilar e instabilidade crânio cervical com múltiplas cirurgias prévias e deiscência de ferida operatória. Devido a falha de osso na escama occipital, assim como da cobertura cutânea adequada, realizamos realinhamento craniocervical, com descompressão indireta anterior, fixação occipitocervical na região da tórcula e cobertura da pele com flap miocutâneo longitudinal pediculado de trapézio. As costelas removidas da região do retalho miocutâneo foram transferidas para serem usadas como enxerto autólogo de osso para fusão craniocervical. No pós-operatório, a paciente utilizou um halo-vest por 3 meses. No presente artigo, apresentamos nuances ilustrados de manobras para realinhamento craniocervical por via posterior na invaginação basilar, bem como estratégias para otimizar a artrodese e o fechamento cutâneo.

Congenital Absence of Posterior Elements of C2 Vertebra with Atlanto-Axial Dislocation and Basilar Invagination: A Case Report and Review of Literature

Developmental anomalies of the axis are commonly encountered, especially anomalies involving the odontoid process. Anomalies of the posterior elements are uncommon. We describe a unique case of agenesis of posterior elements of C2 with basilar invagination and atlanto-axial dislocation. An obese 8-year-old boy presented with symptoms of cervical myelopathy. Radiological workup revealed a craniovertebral junction anomaly with occipitalised atlas, absent posterior elements of axis, and hypertrophied C3 spinous process. Atlanto-axial instability and basilar invagination was present. Magnetic resonance angiography revealed hypoplastic left vertebral artery. Traction with cervical tongs failed to improve the alignment and symptoms. Anterior trans-oral release, followed by posterior decompression and custom-made instrumentation, was done. The patient recovered completely and was asymptomatic at the end of two years. X-ray and computed tomography scan demonstrated reduction of basilar invagination and maintenance of alignment. This is the first case to be reported of agenesis of posterior elements of axis associated with basilar invagination. One should look for this condition in patients with hypertrophied spinous process of C3. Utilization of hypoplastic pedicle of axis serves as an additional fixation point to increase the stability of the construct.

Craniovertebral Junction Instability: A Review of Facts about Facets

Craniovertebral junction surgery involves an appropriate philosophical, biomechanical and anatomical understanding apart from high degree of technical skill and ability of controlling venous and arterial bleeding. The author presents his 30-year experience with treating complex craniovertebral junction instability related surgical issues. The facets of atlas and axis form the primary site of movements at the craniovertebral junction. All craniovertebral junction instability is essentially localized to the atlantoaxial facet joint. Direct manipulation and fixation of the facets forms the basis of treatment for instability.

Incidence of basilar invagination in patients with tonsillar herniation ? a case control craniometrical study / Incidência da invaginação basilar com heriação tonsilar ? estudo da craniometria do tipo caso-controle

A retrospective case-control study based on craniometrical evaluation was performed to evaluate the incidence of basilar invagination (BI). Patients with symptomatic tonsillar herniation treated surgically had craniometrical parameters evaluated based on CT scan reconstructions before surgery. BI was diagnosed when the tip of the odontoid trespassed the Chamberlain’s line in three different thresholds found in the literature: 2, 5 or 6.6 mm. In the surgical group (SU), the mean distance of the tip of the odontoid process above the Chamberlain’s line was 12 mm versus 1.2 mm in the control (CO) group (p<0.0001). The number of patients with BI according to the threshold used (2, 5 or 6.6 mm) in the SU group was respectively 19 (95%), 16 (80%) and 15 (75%) and in the CO group it was 15 (37%), 4 (10%) and 2 (5%).

Realizamos estudo retrospectivo tipo caso-controle baseado na avaliação craniométrica para avaliar a incidência da Invaginação Basilar (IB). Pacientes com herniação tonsilar sintomática tratada cirurgicamente foram avaliados quanto a parâmetros craniométricos obtidos em reconstrução de TC antes da cirurgia. IB foi diagnosticada quando a ponta do odontóide passava acima da linha de Chamberlain em 2, 5 ou 6,6 mm. No grupo cirúrgico (CI), a distância média da ponta do odontóide acima da linha de Chamberlain foi de 12 mm versus 1,2 mm no grupo controle (CO) (p<0.0001). O número de pacientes com IB conforme o critério diagnóstico usado (2, 5 ou 6,6 mm) foi de 19 (95%), 16 (80%) e 15 (75%) no grupo CI, respectivamente, contra 15 (37%), 4 (10%) e 2 (5%) no grupo CO. Pacientes com herniação tonsilar tinham maior incidência de IB comparados ao grupo controle.

Alterações radiográficas de coluna cervical em artrite reumatoide / Radiographic changes of cervical spine in rheumatoid arthritis

INTRODUÇÃO: O envolvimento da coluna cervical é comum na artrite reumatoide (AR). OBJETIVO: Estudar a prevalência das alterações radiológicas de coluna cervical em pacientes com AR e sua associação com perfil clinico e sorológico da doença. MÉTODOS: Analisaram-se as radiografias de coluna cervical em perfil neutro hiperextensão, hiperflexão e transoral de 80 pacientes com AR para presença de subluxação atlanto-axial (LAA), invaginação basilar (IB) e instabilidade subaxial (ISA). Dados de perfil demográfico, clínico (nódulos, pneumonite intersticial, síndrome Sjögren secundária, uso de medicamentos etc.) e sorológico (FR, anti-CCP e FAN) foram obtidos por revisão de prontuários. RESULTADOS: Havia alguma alteração de eixo de coluna cervical em 26/80 (32,5%); em 12/80 (15%) havia LAA; em 6/80(7,5%) existia IB; em 13/80 (16,2%) existia ISA. Erosões em odontoide foram vistas 16/80 (20,0%). As alterações do eixo cervical estavam associadas com idade de início da doença e duração da mesma (P = 0,03 e 0,02, respectivamente). Não se encontrou associação das alterações em coluna cervical com raça, gênero, nódulos, pneumonite intersticial, Sjögren secundário, FR, FAN ou anti-CCP. Pacientes com alterações do eixo cervical apresentavam mais erosões de odontoide (P = 0,03). CONCLUSÕES: Alterações radiológicas em eixo de coluna cervical são comuns e aparecem mais frequentemente em indivíduos com diagnóstico mais precoce de AR e maior tempo de doença.

INTRODUCTION: The involvement of the cervical spine is a common feature of rheumatoid arthritis (RA). OBJECTIVE: To study the prevalence of radiographic changes of the cervical spine in patients with RA and their association with clinical and serological profiles of the disease. METHODS: We analysed lateral (neutral position, hyperextension, hyperflexion) and transoral views of cervical spine radiographs from 80 individuals with RA to investigate the presence of atlanto-axial subluxation (AAS), basilar invagination (BI), and subaxial instability (SAI). Demographic, clinical (nodules, interstitial pneumonitis, secondary Sjögren's syndrome, medications etc.), and serologic (rheumatoid factor - RF, cyclic citrullinated peptide antibody - anti-CCP, and antinuclear factor - ANF) data were obtained from the clinical records. RESULTS: Cervical spine misalignments were identified in 26/80 (32.5%) participants; AAS occurred in 12/80 (15%) participants, BI in 6/80 (7.5%), and SAI in 13/80 (32.5%). Odontoid erosions were identified in 16/80 (20.0%) participants. Cervical spine misalignment exhibited associations with age at onset and disease duration (P = 0.03 and 0.02, respectively). No associations were identified between the cervical spine changes and the participants' ethnicity or gender, presence of nodules, interstitial pneumonitis, secondary Sjögren's syndrome, RF, ANF, or anti-CCP. The participants with cervical spine misalignment exhibited higher frequencies of odontoid erosion (P = 0.03). CONCLUSIONS: Cervical spine misalignment was a common radiographic finding and occurred more frequently in participants with earlier onset and longer length of RA.

Analysis of Measurement Accuracy for Craniovertebral Junction Pathology : Most Reliable Method for Cephalometric Analysis

OBJECTIVE: This study was designed to determine the most reliable cephalometric measurement technique in the normal population and patients with basilar invagination (BI). METHODS: Twenty-two lateral radiographs of BI patients and 25 lateral cervical radiographs of the age, sex-matched normal population were selected and measured on two separate occasions by three spine surgeons using six different measurements. Statistical analysis including intraclass correlation coefficient (ICC) was carried out using the SPSS software (V. 12.0). RESULTS: Redlund-Johnell and Modified (M)-Ranawat had a highest ICC score in both the normal and BI groups in the inter-observer study. The M-Ranawat method (0.83) had a highest ICC score in the normal group, and the Redlund-Johenll method (0.80) had a highest ICC score in the BI group in the intra-observer test. The McGregor line had a lowest ICC score and a poor ICC grade in both groups in the intra-observer study. Generally, the measurement method using the odontoid process did not produce consistent results due to inter and intra-observer differences in determining the position of the odontoid tip. Opisthion and caudal point of the occipital midline curve are somewhat ambiguous landmarks, which induce variable ICC scores. CONCLUSION: On the contrary to other studies, Ranawat method had a lower ICC score in the inter-observer study. C2 end-plate and C1 arch can be the most reliable anatomical landmarks.

Evaluation of osteal posterior cranial fossa in adults by multi-slice CT measurements before and after operation in basilar invagination patients / 中华放射学杂志

ObjectiveTo evaluate the clinical effect of MSCT measurements in the pre- and postoperational osteal posterior cranial fossa for the adult patients of basilar invagination.Methods We reviewed the images of a cohort of 31 adult patients with basilar invagination,which were treated by surgical operation.According to the presence of atlantoaxial dislocation,the patients were divided into groups A and B.The basion-dens interval (BDI),atlanto-dental interval (ADI),space available of the spinal cord ( SAC),clivus-canal angle( CCA),Highly index( HI),and Chamberlian line(CBL) of the posterior cranial fossa were obtained in all the patients.Independent-sample Student's t test was used to compare the differences between groups A and groups B.Spearman correlations were analyzed between CT measurement data and effects of operations.ResultsIn Group A,the BDI,ADI,SAC,CCA,HI,CBL before and after surgery were 12.6 mm,8.3 mm,4.5 mm,3.3 mm;18.2 mm,20.8 mm,138.3°,150.4°,28.7 mm,43.4 mm,6.3 mm,3.3 mm respectively.There were significant differences ( t = 5.603,2.323,3.124,5.531,4.278 and 2.375,respectively,P ＜0.05 ).Preoperative JOA score in groups A was 10 points,and was 14 points after surgery.There was significant difference between the JOA scores before and after surgery ( t = 3.526,P ＜ 0.05 ).There were 7 effective cases and 4 stable cases after surgery in group A.Before and after surgery,JOA score and BDI,ADI,SAC,CCA,HI,CBL were significantly correlated( r = -0.667,- 0.673 ; - 0.571,- 0.619 ; 0.642,0.513 ; 0.525,0.558 ; 0.587,0.511 ; - 0.532,- 0.596,respectively,P＜0.05).The SAC,CCA,and CBL before and after surgery in group B were 18.3 mm,19.6 mm,146.8°,150.2°,2.7 mm,1.8 mm.The difference was statistically significant after operation ( t = 5.359,4.126,0.769,P ＜0.05).The BDI,ADI,and HI before and after surgery in group B were 7.2 mm,6.6 mm,2.4 mm,2.1 mm,39.3 mm,41.5 mm.And there were no significant differences (t = 1.482,2.374,0.153,P＞0.05).The preoperative JOA score in groups B was 11 points,and the postoperative score was 16 points.JOA scores before and after surgery were significantly different (t =2.874,P ＜0.05).There were 14 effective cases and 6 stable cases after operation in group B.The JOA score before and after surgery and BDI,ADI,and HI had no correlation (r =0.341,0.387;0.154,0.182; 0.192,0.167,P ＞0.05),and CBL,SAC and CCA were correlated (r = -0.756,-0.728;0.651,0.672; 0.726,0.695,P ＜0.05).ConclusionMSCT measurements for basilar invagination before and after surgery are helpful for understanding changes of osteal posterior fossa anatomy and comprehensive evaluation of surgical treatment.

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.

Transoral approach to the craniovertebral junction

The transoral approach provides a safe exposure to lesions in the midline and the ventral side of the craniovertebral junction. The advantages of the transoral approach are 1) the impinging bony pathology and granulation tissue are accessible only via the ventral route; 2) the head is placed in the extended position, thus decreasing the angulation of the brainstem during the surgery; and 3) surgery is done through the avascular median pharyngeal raphe and clivus. We analyzed the clinical effects of odontoidectomy after treating 38 patients with basilar invagination. The anterior transoral operation to treat irreducible ventral compression in patients with basilar invagination was performed in 38 patients. The patientsÆ ages ranged from 34 to 67 years. Fourteen patients had associated Chiari malformation and eight had previously undergone posterior decompressive surgery. The main indication for surgery was significant neurological deterioration. Symptoms and signs included neck pain, myelopathy, lower cranial nerve dysfunction, nystagmus and gait disturbance. Extended exposure was performed in 24 patients. The surgery was beneficial to the majority of patients. There was one death within 10 days of surgery, due to pulmonary embolism. Postoperative complications included two cases of pneumonia, three cases of oronasal fistula with regurgitation and one cerebrospinal fluid leak. In patients with marked ventral compression, the transoral approach provides direct access to the anterior face of the craniovertebral junction and effective means for odontoidectomy.

O acesso transoral é uma via direta e segura às lesões situadas na linha média e na face anterior da junção craniocervical. As vantagens do acesso transoral são as seguintes:1) a compressão óssea e o tecido de granulação localizam-se anteriormente e são accessíveis pela via anterior; 2) a cabeça do paciente é colocada em extensão, diminuindo a angulação do tronco cerebral durante a cirurgia; e 3) a cirurgia é feita através de um plano avascular na linha média faríngea e clivo. Analisamos os resultados obtidos após odontoidectomia por via transoral em 38 pacientes portadores de invaginação basilar. Trinta e oito pacientes com compressão ventral da junção craniocervical foram submetidos a odontoidectomia por via transoral. A idade dos pacientes variou de 34 a 67 anos. Quatorze pacientes apresentavam associação com malformação de Chiari tipo I e 8 já haviam sido submetidos à cirurgia descompressiva por via posterior. A maioria dos pacientes apresentou nucalgia, mielopatia, déficits dos nervos cranianos baixos, nistagmo, e distúrbio da marcha. Em 24 pacientes foi necessário ampliar o acesso transoral através de miotomia do palato mole, ou osteotomia do palato duro ou maxilotomia. A cirurgia proporcionou melhora dos sintomas na maioria dos pacientes. Um paciente faleceu no pós-operatório imediato por causa de embolia pulmonar. Dois pacientes tiveram pneumonia, três apresentaram fístula oronasal com regurgitação, e um teve fístula liquórica. Em pacientes com compressão ventral irredutível da junção craniocervical, a via transoral proporcionou uma abordagem direta e ampla ao processo odontoide.

Atlanto-occipital Assimilation Associated with Basilar Invagination, C1-2 Instability, C2-3 Block Vertebra,and C3-4 Retrolisthesis : A Case Report / 대한정형외과학회잡지

Congenital atlanto-occipital assimilation is frequently accompanied by basilar invagination and C1-2 instability. Occipitocervical fusion is required if these conditions cause neurological symptoms. Recently posterior fusion using occipitocervical screw fixation in the extension position has been introduced for the simultaneous decompression of the cervicomedullary junction compressed by basilar invagination, a reduction of atlantoaxial subluxation, and rigid fixation. However, it is a technically demanding procedure, and there is no domestic report of an experience with this procedure. We report a case of a patient with C2-3 block vertebra and C3-4 retrolisthesis in addition to congenital atlanto-occipital assimilation, basilar invagination and C1-2 instability. The patient underwent posterior fusion using occipitocervical screw fixation in the extension position.

Staged Decompression of Chiari Malformation Associated with Basilar Invagination: A Case Report

The staged decompression(posterior and anterior) of foramen magnum was performed in the patient with Chiari I malformation associated with basilar invagination. Three years prior to admission, the patient was admitted due to ataxia and dysmetria. After the posterior decompression of foramen magnum, the patient's cerebellar sign improved significantly. But spastic gait disturbace was noted two years later. We performed a transoral anterior decompression to relieve brain stem compression, and an occipitocervical fusion with contoured rod to prevent possible instability. Following the operation, the spasticity improved. The authors believe this sets the successful staged decompression of Chiari I malformation associated with basilar invagination.

Surgical Experience of Basilar Invagination by Transoral Transpharyngeal Approach

Basilar invagination or basilar impression involves the upward displacement of the margins of the foramen magnum into the base of the skull. That this entity may be asymptomatic or associated with symptoms referable to encroachment into the posterior fossa or embarrassment of the posterior circulation is well known. Currently the authors have experienced a young male patient with basilar invagination presented with progressive myelopathy and lower cranial neuropathies due to odontoid invagination. It was thought that a posterior decompression would be hazardous;therefore, the inferior clivus, odontoid process, and anterior arch of the atlas were removed transoral-transpharyngeally and bone fusion was performed with iliac bone. Furthermore the operative result was good without any serious complication. The operation technique is detailed.