Correlation Among Syrinx Resolution, Cervical Sagittal Realignment, and Surgical Outcome After Posterior Reduction for Basilar Invagination, Atlantoaxial Dislocation, and Syringomyelia.

BACKGROUND: The correlation among syrinx resolution, occipitoaxial sagittal alignment, and surgical outcome in long-term follow-up seems to have not been clarified. OBJECTIVE: To further explore the relationship between the syrinx resolution and occipitoaxial realignment after posterior reduction and fixation in basilar invagination (BI)-atlantoaxial dislocation (AAD) patients with syringomyelia. METHODS: A continuous series of 32 patients with BI-AAD and syringomyelia who received direct posterior reduction met the inclusion criteria of this study. Their clinical and imaging data were analyzed retrospectively. Before surgery and at the last follow-up, we used the Japanese Orthopedic Association (JOA) score and the Neck Disability Index (NDI) to assess the neurological status, respectively. The Pearson correlation coefficient and multiple stepwise regression analysis were used to explore the relevant factors that may affect surgical outcomes. RESULTS: There were significant differences in atlantodental interval, clivus-axial angle, occiput-C2 angle (Oc-C2A), cervicomedullary angle (CMA), subarachnoid space (SAS) at the foramen magnum (FM), syrinx size, NDI, and JOA score after surgery compared with those before surgery. ΔCMA and the resolution rate of syrinx/cord as relevant factors were correlated with the recovery rate of JOA (R 2 = 0.578, P < .001) and NDI (R 2 = 0.369, P < .01). What's more, ΔSAS/FMD (SAS/FM diameter) and ΔOc-C2A were positively correlated with the resolution rate of syrinx/cord (R 2 = 0.643, P < .001). CONCLUSION: With medulla decompression and occipital-cervical sagittal realignment after posterior reduction and fusion for BI-AAD patients with syringomyelia, the structural remodeling of the craniovertebral junction and occipitoaxial realignment could contribute to syringomyelia resolution.

Association between Brachycephaly, Chiari Malformation, and Basilar Invagination.

BACKGROUND: There is evidence that Chiari malformation (CM) and basilar invagination (BI) are largely due to disproportion between the content and volume of the posterior fossa. A recent study identified an increased association between brachycephaly and BI. In several types of craniosynostosis, the posterior fossa volume is smaller than normal, and this is more pronounced in coronal synostosis. The aim of this study is to evaluate the association between CM and BI. METHODS: The cephalic index (CI) measured on magnetic resonance imaging (MRI) from a sample of patients with craniocervical malformation was compared with that of normal subjects. RESULTS: The average CI in the craniovertebral junction malformation (CVJM) group was significantly higher in BI patients than in normal subjects. The BI patients also had the highest CI among the whole sample of patients (p = 0.009). CONCLUSIONS: In this study, BI patients had the highest CI among patients with CVJM and a significantly higher CI than those in the control group. Our data confirm the association between BI and brachycephaly.

Indirect Ventral Brainstem Decompression by Posterior C1-C2 Distraction and Fixation for Basilar Invagination.

OBJECTIVE: Basilar invagination usually shows a decrease of clivus axis angle (CAA), which could give rise to progressive neural compression. Exploring a safe and effective fixation technique to achieve atlantoaxial stability and neural decompression remains necessary. In this study, we introduce a modified posterior C1-C2 distraction and fixation technique by which we obtained indirect ventral neural decompression and atlantoaxial stability in a series of patients with decreased CAA. METHODS: Thirty patients of basilar invagination were enrolled in our series. All patients underwent thin-slice computed tomography (CT) scan, magnetic resonance imaging, and dynamic plain radiography examinations before surgery, at discharge and during the follow-ups. Posterior C1-C2 facet joint release and intraoperative reduction by fastening rods were performed in all patients. The CAA was measured on midsagittal CT scans. Patients' neurologic status was evaluated by the Japanese Orthopaedic Association score. RESULTS: No neurovascular injury and serious postoperative complication occurred in all patients. Complete ventral brainstem decompression was achieved in 20 patients and partial in 10 patients. The mean postoperative CAA significantly improved to 132.6 degrees compared with the preoperative 123.6 degrees (P < 0.01). The bone fusion was confirmed in all patients on the basis of the last follow-up spine CT scans. CONCLUSIONS: Indirect ventral brainstem decompression by posterior C1-C2 distraction and fixation is a safe and effective technique for treatment of basilar invagination.

Anterior Distraction and Reduction with Posterior Stabilization for Basilar Invagination: A Novel Technique.

BACKGROUND: Introduction of a posterior spacer for atlantoaxial joint distraction followed by posterior stabilization is a commonly performed procedure for irreducible atlantoaxial dislocation. We present a unique case in which posterior distraction was associated with increased risk of injury to the vertebral artery (VA) owing to its anomalous course, and hence a novel anterior distraction technique was used. CASE DESCRIPTION: A 45-year-old woman presented with severe neck pain for 1 month with gait imbalance and history of occipital headache for 1 year. Clinical examination revealed upper motor neuron-type findings. Hoffmann sign was positive bilaterally. Clinically, the patient had Nurick grade 4 cervical myelopathy. Magnetic resonance imaging showed basilar invagination along with Arnold-Chiari malformation and syrinx formation at C3-C4 vertebral levels. CT angiography revealed anomalous VAs directly overlying the atlanto-occipital joint. Owing to the anomalous route of the VA and unfavorable slope of facet joints, a 2-step anterior reduction followed by posterior stabilization surgery was planned. We achieved complete reduction using a 10-mm titanium cage inserted via a retropharyngeal approach. Following anterior reduction, instrumented in situ occipitocervical fusion was performed using a plate and screw construct. At 2-year follow-up, the patient is ambulating independently without gait imbalance and with successful radiologic fusion. CONCLUSIONS: The craniovertebral junction has a unique pathoanatomy, and the course of the vertebral artery is variable. Appropriate investigations, including computed tomography angiography, with adequate surgical planning will provide a desirable long-term outcome. Our novel technique has the potential to add a new dimension to the management of irreducible atlantoaxial dislocation.

Outcome of Surgery for Congenital Craniovertebral Junction Anomalies with Atlantoaxial Dislocation/Basilar Invagination: A Retrospective Study of 94 Patients.

OBJECTIVE: To evaluate the results of surgery for congenital craniovertebral junction (CVJ) anomalies with atlantoaxial dislocation (AAD)/basilar invagination (BI) and compare the results of transoral odontoidectomy and posterior fusion (TOO+PF) with only posterior fusion (PF) in patients with irreducible AAD/BI. METHODS AND RESULTS: All 94 patients with congenital CVJ anomalies with AAD/BI operated on during the 3-year study period (June 2013-May 2016) were included. Of these patients, 55 had irreducible AAD/BI and the remaining 39 had reducible AAD/BI. TOO+PF was restricted to patients (34/94; 36.2%) with irreducible AAD/BI when reduction and realignment by intraoperative C1-C2 facet joint manipulation were considered technically difficult and risky. The remaining patients with irreducible AAD/BI and all the patients with reducible AAD/BI (60/94; 63.8%) were managed with only posterior fusion. Poor preoperative Nurick grade, preoperative dyspnea/lower cranial nerve deficits, and syringomyelia were associated with significantly higher incidence of postoperative pulmonary complications. Follow-up ≥3 months (final follow-up) was available for 87 patients. Good outcome (Nurick grade 0-3) at final follow-up was noted in 90% (45/50) of the patients with irreducible AAD/BI and 91.9% (34/37) of the patients with reducible AAD/BI. Preoperative poor Nurick grade (4-5) was the only factor associated with poor outcome. No significant difference in perioperative complications, outcome, and fusion was noted between patients who underwent TOO+PF or only PF for irreducible AAD/BI. CONCLUSIONS: Many of the patients with congenital AAD/BI showed remarkable recovery after surgery. Preoperative poor Nurick grade (4-5) is associated with poor outcome. TOO+PF is a safe alternative treatment option for irreducible AAD/BI when only PF techniques are technically difficult/risky.

A Safe and Effective Posterior Intra-Articular Distraction Technique to Treat Congenital Atlantoaxial Dislocation Associated With Basilar Invagination: Case Series and Technical Nuances.

BACKGROUND: The management of atlantoaxial dislocation (AAD) associated with basilar invagination (BI) is challenging, and traditional posterior-only approaches lack the ability to release the anterior soft tissue resulting in unsatisfactory reduction. Furthermore, vertebral artery anomalies and deformed anatomy increase surgical risks. OBJECTIVE: To introduce a safe and efficient technique to reduce congenital AAD and BI through a single-stage posterior-only approach. METHODS: A total of 65 patients with AAD and concomitant BI who had congenital osseous abnormalities were retrospectively analyzed. All patients had anterior soft tissue released through a posterior-only approach, followed by intra-facet cages implantation, cantilever correction, and instrumentation. Clinical results were measured using the Japanese Orthopedic Association (JOA) scale, and radiographic measurements included the atlanto-dental interval, the distance of odontoid tip above Chamberlain's line, clivus-canal angle (CCA), and syrinx length. Paired t-tests were used to compare preoperative and postoperative measurements. RESULTS: The mean JOA score increased from 10.98 to 14.40 at 1-yr follow-up. Complete reduction of AAD and BI was achieved in 48 patients (73.8%). The mean CCA improved from 115° preoperatively to 129° postoperatively. Reduction of syrinx size was observed in 14 patients at 1 wk and in 35 patients 1 yr after surgery. All patients achieved bony fusion. CONCLUSION: Posterior intra-articular distraction followed by cage implantation and cantilever correction can achieve complete reduction in most cases of congenitally anomalous AAD associated with BI.

Determination of Normal Values of the Basal Angle in the Era of Magnetic Resonance Imaging.

BACKGROUND: The flexion of the skull base (basal angle [BA]) is the inclination between the anterior fossae and the basilar ramp of the occipital and sphenoid bones. An increased BA, termed platybasia, is usually associated with basilar invagination. BA reference values in the magnetic resonance imaging (MRI) era and the diagnosis of platybasia are of clinical importance. The transnasal approach has been the surgical technique of choice to remove the odontoid process in cases of ventral brainstem compression in patients with platybasia. The knowledge of normal BA values has been influenced by technological image acquisitions. The aim of this study was to determine the normal BA values in normal subjects in the MRI era. METHODS: For the determination of normal BA values, the literature reporting these values in normal individuals was reviewed and a meta-analysis of pertinent studies was performed. RESULTS: A total of 8 articles were included in this study, evaluating a total of 667 individuals. A summary measure of the results was obtained. The data obtained in this analysis provided a final basal angle value of 116.5 degrees (95% confidence interval, 104.39-128.7). The normal basal angle ranges between 104 and 129 degrees. CONCLUSION: Platybasia can be defined as a value >129 from the basal angle.

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.

Does Additional Bone Grafting of Atlantoaxial Joint Increase Bone Fusion Rate of Iliac Crest Autograft in Posterior Occipitocervical Fusion? Retrospective, Controlled Study with 2-Year Follow-up.

OBJECTIVE: We sought to explore whether additional bone grafting of the atlantoaxial joint increases the bone fusion rate of iliac crest autograft in posterior occipitocervical fusion surgery. METHODS: From January 2012 to January 2016, a total of 78 patients who had basilar invagination with occipitalization of the atlas came to our tertiary spine center. Except for those lost to follow-up (10 cases) or who had a follow-up time <2 years (20 cases), there were 48 patients retrospectively included in this study. In the control group, a piece of autogenous iliac corticocancellous bone was placed between the occipital and C2 vertebral lamina for fusion. In the hybrid fusion group, besides posterior occipitocervical autograft, some granular bone harvested from the iliac crest was packed into the bilateral atlantoaxial joint. X-ray imaging and cervical computed tomography (CT) were performed during follow-up. RESULTS: The operations were completed successfully in all patients without intraoperative complications. Only 21 (87.5%) patients in the control group had confirmed posterior bony fusion on CT, while 24 (100%) patients in the hybrid fusion group had confirmed posterior bony fusion. There were postoperative implant-related complications in 2 patients. Both cases belonged to the control group (8.3%). Three patients (12.5%) complained of transient numbness in the posterior occipital region: 2 patients in the hybrid group and 1 patient in the control group. The mean duration to posterior occipitocervical fusion was 5.5 months in the hybrid fusion group versus 6.1 months in the control group (P = 0.757). Of note, in the hybrid fusion group, the process of atlantoaxial joint fusion was faster than that of posterior occipitocervical fusion (5.1 months vs. 5.5 months, P = 0.823). CONCLUSIONS: Additional bone grafting of the atlantoaxial joint could increase the bone fusion rate of iliac crest autograft in posterior occipitocervical fusion.

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.

Revision surgery after rod breakage in a patient with occipitocervical fusion: A case report.

RATIONALE: Rod breakage after occipitocervical fusion (OCF) has never been described in a patient who has undergone surgery for basilar invagination (BI) and atlantoaxial dislocation (AAD). Here, we present an unusual but significant case of revision surgery to correct this complication. PATIENT CONCERNS: A 32-year-old female presented with neck pain, unstable leg motion in walking, and also BI with AAD. Her first surgery was planned to correct these conditions and for fusion at the occipital junction (C3-4) using a screw-rod system. At the 31-month follow-up after her first operation, the patient complained of severe neck pain and limitation of motion, suggesting rod breakage. DIAGNOSES: Rod breakage after occipitocervical fusion for BI and AAD. INTERVENTIONS: The patient underwent reoperation for replacement of the broken rods, adjustment of the occipitocervical angle, maintenance of the bone graft bed, and fusion. OUTCOMES: At follow-up, the hardware was found to be in good condition, with no significant loss of cervical lordosis. At the 37-month follow-up after her second operation, the patient was doing better and continuing to recover. LESSONS: We concluded that nonideal choice of occipitocervical angle may play an important role in rod breakage; however, an inadequate bone graft and poor postoperative fusion may also contribute to implant failure.

Cranio-vertebral transition assessment by magnetic resonance imaging in a sample of a northeast Brazilian population / Avaliação da transição crânio-vertebral por ressonância magnética em uma amostra da população do nordeste brasileiro

ABSTRACT Platybasia and basilar invagination are important alterations of the cranial-vertebral transition. Neuroimaging-based platybasia parameters include the Welcker basal angle, distance between the apex of the odontoid and Chamberlain's line, and the clivus-canal angle. This study aimed to measure and correlate these parameters in a sample from northeast Brazil. Methods Cross-sectional analysis of craniometric parameters from individuals submitted to magnetic resonance at an outpatient imaging center between 2011 and 2012. Results Of 181 analyzed cases, the Welcker basal angle averaged 128.96º (SD 6.51), median distance between apex of the odontoid and Chamberlain's line was 2.27 mm (IQR -1.23-4.47) and the median clivus-canal angle was 150.5º (IQR 143.2-157.3). The Welcker basal angle was inversely correlated to the clivus-canal angle, and correlated to the distance between the apex of the odontoid and Chamberlain's line. Conclusion There was a tendency to platibasia, basilar invagination and narrowing of the cranio-vertebral transition.

RESUMO Platibasia e invaginação basilar são importantes alterações da transição craniovertebral. Existem parâmetros importantes obtidos pela neuroimagem, como o ângulo basal de Welcker, distância do ápice do odontoide à linha de Chamberlain e o ângulo clivo-canal. Este estudo procurou medir e correlacioná-los em uma amostra do Nordeste Brasileiro. Métodos Estudo transversal com medidas de indivíduos submetidos a ressonância magnética craniana em um centro de diagnóstico por imagem entre 2011 e 2012. Resultados Dos 181 casos analisados, o ângulo basal de Welcker teve média 128.96º (DP 6.51), a distância do ápice do odontoide à linha de Chamberlain obteve mediana 2.27 mm (IIQ -1.23-4.47) e o ângulo clivo-canal mediano foi 150.5º (IIQ 143.2-157.3). O ângulo basal de Welcker foi inversamente correlacionado com o ângulo clivo-canal e diretamente correlacionado com a distância do ápice do odontoide à linha de Chamberlain. Conclusão Houve uma tendência a platibasia, invaginação basilar e estreitamento da transição craniovertebral, que poderiam ser influenciados pela natureza multirracial e por fatores antropológicos da população estudada.

3-D simulation of posterior fossa reduction in Chiari I / Simulação em 3D da redução da fossa posterior no Chiari do tipo I

ABSTRACT We proposed a 3D model to evaluate the role of platybasia and clivus length in the development of Chiari I (CI). Using a computer aided design software, two DICOM files of a normal CT scan and MR were used to simulate different clivus lengths (CL) and also different basal angles (BA). The final posterior fossa volume (PFV) was obtained for each variation and the percentage of the volumetric change was acquired with the same method. The initial normal values of CL and BA were 35.65 mm and 112.66º respectively, with a total PFV of 209 ml. Ranging the CL from 34.65 to 29.65 – 24.65 – 19.65, there was a PFV decrease of 0.47% – 1.12% – 1.69%, respectively. Ranging the BA from 122.66º to 127.66º – 142.66º, the PFV decreased 0.69% – 3.23%, respectively. Our model highlights the importance of the basal angle and clivus length to the development of CI.

RESUMO No presente estudo, propusemos a criação de um modelo computacional em 3D com elaboração de software onde dois arquivos em formato DICOM com uma TC e RNM de crânio foram usados para simular diferentes mensurações na extensão do clivus (EC) e no ângulo basal (AB). O volume final da fossa posterior (VFP) foi obtido em cada variação, bem como a percentagem de volume alterada. O tamanho inicial da EC era de 35,65 mm e o do AB era de 112.66º, com um VFP de 209 ml. Variando a EC de 34,65 para 29,65 – 24.65 e 19.65, houve uma diminuição do VFP de 0.47%, 1.12% e 1.69%, respectivamente. Variando o AB de 122,66º para 127,66º e 142,66º, o VFP diminui para 0.69% e 3.23%, respectivamente. Nosso modelo enfatiza a importância da patogênese do aumento do AB e do encurtamento do clivus no desenvolvimento do Chiari I.

Posterior C1-C2 screw and rod instrument for reduction and fixation of basilar invagination with atlantoaxial dislocation.

PURPOSE: To report the surgical technique and preliminary clinical results for the treatment of basilar invagination (BI) with atlantoaxial dislocation (AAD) by posterior C1-C2 pedicle screw and rod instrument. METHODS: Between July 2012 and August 2013, 33 patients who had BI with AAD underwent surgery at our institution. Pre and postoperative three-dimensional computed tomographic (CT) scans were performed to assess the degree of dislocation. Magnetic resonance (MR) imaging was used to evaluate the compression of the medulla oblongata. For all patients, reduction of the AAD was conducted by two steps: fastening nuts and rods was performed to achieve the horizontal reduction. Distraction between C1 and C2 screws was performed to obtain the vertical reduction. RESULTS: No neurovascular injury occurred during surgery. Follow-up ranged from 6 to 15 months (mean 10.38 months) in 32 patients. Post-operative three-dimensional CT showed that complete horizontal reduction was obtained in 30/33 (90.9%), and complete vertical reduction was obtained in 31/33 (93.9%). The repeated three-dimensional CT and MR image demonstrated that bony fusion and the decompression of the medulla oblongata were obtained in all patients. Clinical symptoms improved significantly 3 months after surgery. CONCLUSIONS: This C1-C2 pedicle screw and rod instrument is a promising technique for the treatment of BI with AAD.

Treatment of basilar invagination with atlantoaxial dislocation: atlantoaxial joint distraction and fixation with transoral atlantoaxial reduction plate (TARP) without odontoidectomy.

PURPOSE: Although direct transoral decompression and one-stage posterior instrumentation can obtain satisfactory cord decompression for the treatment of basilar invagination with atlantoaxial dislocation, surgical injuries run high as combinative anterior-posterior approaches were necessary. Furthermore, the complications will rise notably when involvement of dens and/or clivus in the decompression necessitates relatively complicated surgical techniques. First initiated in 2005, transoral atlantoaxial reduction plate (TARP) works as an internal fixation for the treatment of basilar invagination with irreducible atlantoaxial dislocation. Therefore, this article aimed to describe several operative experiences about this approach, which has delivered successful decompression, fixation and fusion. METHODS: 21 consecutive patients with basilar invagination underwent the TARP operation. The pre- and postoperative medulla-cervical angles were measured and compared. The JOA scores of spinal cord function were calculated pre- and post-operatively. 20 cases (20/21) were followed up to average 12.5 months. RESULTS: Symptoms of all the 20 cases were relieved in different degrees. The postoperative imaging showed the odontoid processes obtained ideal reduction and the internal fixators were all in good position. The medulla-cervical angle was correctd from an average (± standard deviation) 128.7° + 11.9° (n = 20) before surgery to 156.5° + 8.1° (n = 20) after surgery (P < 0.01). The average preoperative and postoperative Japaneses Orthopedic Association scores were 11.25 (n = 20) and 15.9 (n = 20), respectively, indicating 76 % improvement. Screw-loosening was observed in one patient due to severe osteoporosis. After a revised operation with a TARP in another size, the neurological symptoms showed no obvious improvements. Then the treatment was terminated. CONCLUSIONS: The TARP operation and intra-operative traction could reduce the odontoid process superiorly migrating into the foramen magnum, directly ease the ventral compression of spinal cord, and fix the reduced atlantoaxial joints through a single transoral approach without the need of a posterior operation. In this stury, 21 patients were evaluated and 20 did well with TARP operation. The preliminary clinical result was satisfactory.

Endoscopic transnasal odontoidectomy to treat basilar invagination with congenital osseous malformations.

PURPOSE: Transoral resection of the odontoid has been accepted as a standard procedure to decompress the cervicomedullary junction during the past several decades. The endoscopic transnasal odontoidectomy is emerging as a feasible surgical alternative to conventional microscopic transoral approach. In this article, we describe several operative nuances and pearls from our experience about this approach, which provided successful decompression. METHODS: From September 2009 to April 2010, three consecutive patients with basilar invagination, of which the etiology was congenital osseous malformations, underwent endoscopic transnasal odontoidectomy. All patients presented with myelopathy. The last two cases also received occipitocervical fixation and bone fusion during the same surgical episode to ensure stability. RESULTS: All the patients were extubated after recovery from anesthesia and allowed oral food intake the next day. Cerebrospinal fluid rhinorrhea was found in the second case and cured by continuous lumber drainage of cerebrospinal fluid. No infection was noted. The average follow-up time was more than 24 months. Remarkable neurological recovery was observed postoperative in all patients. CONCLUSION: The endoscopic transnasal odontoidectomy is a feasible approach for anterior decompression of pathology at the cervicomedullary junction. The advantages over the standard transoral odontoidectomy include elimination of risk of tongue swelling and teeth damaging, improvement of visualization, alleviation of prolonged intubation, reduction of need for enteral tube feeding and less risk of affecting phonation. The minimally invasive access and faster recovery associated with this technique make it a valid alternative for decompression of the ventral side of the cervicomedullary junction.

The importance of platybasia and the palatine line in patient selection for endonasal surgery of the craniocervical junction: a radiographic study of 12 patients.

OBJECTIVE: Ventral decompressive surgery of the craniocervical junction is performed to manage a variety of conditions, including basilar invagination, which can be associated with platybasia. We have noted that the anatomic changes of platybasia could affect the height of the odontoid over a line drawn along the nasal cavity floor, the palatine line (PL). This anatomic change may influence the use of nasal endoscopic surgery for patients with platybasia who also have basilar invagination. We investigated whether the height of the craniocervical junction is elevated over the PL in patients with and without platybasia. METHODS: We conducted a retrospective review of consecutive craniovertebral junction surgical cases during a 14-month period. During that time we treated 12 patients, including 4 with platybasia and 8 without. The average age was 50 years (range, 18-64 years). Preoperative and postoperative radiographic images were evaluated and charts reviewed. RESULTS: The mean height of the odontoid over the PL without platybasia was 3.5 mm (range, 0-19.0 mm). In those with platybasia, it was 15.5 mm (range, 7-26.0 mm; P=.021). There was a statistically significant increase in the height of the clival tip and C1 ring in patient with platybasia as well. CONCLUSIONS: Platybasia is associated with an increase in the odontoid and craniocervical junction over the PL. This increase in height has implications for endoscopic approach selection in patients with platybasia. Platybasia patients with basilar invagination may be better suited to a transnasal approach.

Treatment of primary basilar invagination by cervical traction and posterior instrumented reduction together with occipitocervical fusion.

STUDY DESIGN: This retrospective study was conducted to analyze the radiographic and clinical results in seven patients with primary basilar invagination who accepted a combination of continuous cervical traction before operation and posterior screw/rod system reduction together with occipitocervical fusion. OBJECTIVE: To evaluate the radiographic and clinical outcomes of this treatment regimen in combination of continuous cervical traction and posterior instrumented reduction with pedicle screw/rod system. SUMMARY OF BACKGROUND DATA: Primary basilar invagination poses considerable difficulties in the surgical management regarding surgical approach, reduction, and decompression. A variety of methods have been described to treat primary basilar invagination and all methods existed limits. METHODS: There were four male and three female patients, and the ages ranged from 12 to 40 years (average age, 22.3 yr). Six patients presented neurologic deficits. The Nurick scale was from 1 grade to 4 grades (average, 2.7 grades). The distance of the odontoid tip in relation to Wackenheim line, atlantodental interval, Klaus height index, craniospinal angle, modified Omega angle, and cervicomedullary angle were measured pretreated and after surgery. When the tip of odontoid process was inferior or approximate to Wackenheim line and McRae line after cervical traction, the operation of reduction and fixation should be accepted. RESULTS: After surgery, the mean Wackenheim value and atlantodental distance were reduced 9.3 mm and 2.0 mm, respectively. The mean Klaus height index, craniospinal angle, Omega angle, and cervicomedullary angle improved 6.5 mm, 17.0°, 11.6°, and 27.4°, respectively. All postoperative data had a significance compared with pretreatment data (P < 0.05). There was a tendency that younger patients were able to obtain more ideal reduction than adults. Of six patients with neurologic symptoms, five patients were normal or nearly normal. All patients achieved solid fusion. CONCLUSION: This case series demonstrates a safe, easy, and effective treatment regimen for the patients with primary basilar invagination.

Reversal of longstanding musculoskeletal changes in basilar invagination after surgical decompression and stabilization.

OBJECT: The authors investigated the changes in the bone architecture and the characteristics of the neck and craniovertebral region in selected cases of basilar invagination. The reversal in these changes that occurred after decompression and fixation are analyzed. The implications of such an analysis in understanding the pathogenesis of a number of features that are characteristically associated with basilar invagination are evaluated. METHODS: One hundred and seventy selected patients with basilar invagination who underwent atlantoaxial joint distraction-fixation surgery at the authors' institution between 1999 and April 2008 were reviewed. The study was prospective after June 2006. A variety of parameters were used for radiological and physical assessments. The evaluation was done on the basis of pre- and postoperative imaging studies and clinical photographs. In the 41 prospective cases, additional direct physical measurements of the neck were performed. RESULTS: Prior to surgery there were several physical changes such as reduced neck length, torticollis, exaggerated lordosis of the cervical spine, and reduced craniospinal angulation. Other findings included reduced discspace height, significant posterior cervical osteophyte formation, assimilation of atlas (72%), single-level (29%) or multiple-level (3%) cervical fusions, and an increase in the spinal subarachnoid space both above and below the level of maximum neural compression at the tip of the odontoid process. After surgical decompression of the region, there was remarkable recovery in craniovertebral alignments, and an increase in neck length (maximum up to 42 mm) was obvious on physical and radiological examination in 85% of patients. The disc-space height increased and there was a reversal of altered cervical lordosis, craniospinal angulation (maximum up to 36 degrees ), and torticollis. CONCLUSIONS: It appears that a number of physical spinal changes characteristically associated with basilar invagination such as a short neck, exaggerated neck lordosis, torticollis, cervical spondylotic changes and fusions are potentially reversible after decompression and stabilization of the craniovertebral junction.