Clivo-axial Angle Research Articles

Occipitocervical fusion with relief of odontoid invagination: atlantoaxial distraction method using cylindrical titanium cage for basilar invagination—case report

A 65-year-old woman presented with basilar invagination manifesting as neck pain, dysesthesia around the lips, and truncal ataxia. The radiological findings demonstrated invagination of the odontoid process into the medulla oblongata and vertical atlantoaxial subluxation with C1 assimilation. The clivo-axial angle was 88° and the cervicomedullary angle was 115°, indicating severe basilar invagination. We planned occipitocervical fusion with atlantoaxial distraction using a cylindrical titanium cage. C2 pedicle screws were inserted, and the atlantoaxial joint was opened to translocate the odontoid process downward. A cylindrical titanium cage packed with local bone graft was inserted into the opened facet joint space. Occipital-C2 fusion was completed by fastening the occipital bone plates with pedicle screws using titanium rods. Postoperatively, the apex of the odontoid process descended by 7 mm, and the clivo-axial and cervicomedullary angles opened to 112° and 125°, respectively. Invagination of the odontoid process into the medulla oblongata was relieved. The preoperative symptoms improved, and she remained symptom-free without requiring anterior decompression over 2 years. Bone fusion of the atlantoaxial joints was completed with sustained facet distraction 12 months after the surgery, and adequate relief of the basilar invagination was maintained. The atlantoaxial distraction method using a cylindrical titanium cage can be a useful option in posterior fusion surgery for basilar invagination.

Effect of a reduction of the atlanto-axial angle on the cranio-cervical and subaxial angles following atlanto-axial arthrodesis in rheumatoid arthritis

We retrospectively investigated the radiographic findings in patients with atlanto-axial subluxation (AAS) due to rheumatoid arthritis, and clarified the effect of reduction of the atlanto-axial angle (AAA) on the cranio-cervical and subaxial angles. Forty-one patients, consisting of 29 females and 12 males, with AAS treated by surgery were reviewed. The average patient age at surgery was 61.0years, and the average follow-up period was 4.0years. We investigated the AAA at the neutral position in lateral cervical radiographs before surgery and at the last follow-up. In addition, we also investigated the clivo-axial angle (CAA) and the subaxial angle (SAA) at the neutral position before and after surgery. Due to pre-operative AAA, the patients were classified into three groups as follows: (1) the kyphotic group (K group), (2) the neutral group (N group), and (3) the lordotic group (L group). The average AAA values at the neutral position in the K group before and after surgery were 6.0° and 18.1°, respectively (P<0.001). In the N group 19.7° and 21.7°, respectively (P<0.05), and in the L group 31.6° and 27.0°, respectively (P<0.01). However, no significant differences in the average CAA values were found before and after surgery in all groups. Furthermore, no significant differences in the SAA values were seen before and after surgery in all groups. A proper reduction of the AAA did not affect the cranial angles or induce kyphotic malalignment of the subaxial region after atlanto-axial arthrodesis. However, if we can obtain a significant and large reduction of AAA in patients showing kyphosis before surgery, then this reduction will be offset in the atlanto-occipital joint and we should therefore pay special attention to its morphology after surgery.

Complex Chiari malformations in children: an analysis of preoperative risk factors for occipitocervical fusion

Chiari malformation Type I (CM-I) is a congenital anomaly often treated by decompressive surgery. Patients who fail to respond to standard surgical management often have complex anomalies of the craniovertebral junction and brainstem compression, requiring reduction and occipitocervical fusion. The authors hypothesized that a subgroup of "complex" patients defined by specific radiographic risk factors may have a higher rate of requiring occipitocervical fusion. A retrospective review was conducted of clinical and radiographic data in pediatric patients undergoing surgery for CM-I between 1995 and 2010. The following radiographic criteria were identified: scoliosis, syringomyelia, CM Type 1.5, medullary kinking, basilar invagination, tonsillar descent, craniocervical angulation (clivoaxial angle [CXA] < 125°), and ventral brainstem compression (pB-C2 ≥ 9 mm). A multivariate Cox regression analysis was used to determine the independent association between occipitocervical fusion and each variable. Of the 206 patients who underwent CM decompression with or without occipitocervical fusion during the study period, 101 had preoperative imaging available for review and formed the study population. Mean age at surgery was 9.1 years, and mean follow-up was 2.3 years. Eighty-two patients underwent suboccipital decompression alone (mean age 8.7 years). Nineteen patients underwent occipitocervical fusion (mean age 11.1 years), either as part of the initial surgical procedure or in a delayed fashion. Factors demonstrating a significantly increased risk of requiring fusion were basilar invagination (HR 9.8, 95% CI 2.2-44.2), CM 1.5 (HR 14.7, 95% CI 1.8-122.5), and CXA < 125° (HR 3.9, 95% CI 1.2-12.6). Patients presenting with basilar invagination, CM 1.5, and CXA < 125° are at increased risk of requiring an occipitocervical fusion procedure either as an adjunct to initial surgical decompression or in a delayed fashion. Patients and their families should be counseled in regard to these findings as part of a preoperative CM evaluation.

Deformative stress associated with an abnormal clivo-axial angle: A finite element analysis

Background:Chiari malformation, functional cranial settling and subtle forms of basilar invagination result in biomechanical neuraxial stress, manifested by bulbar symptoms, myelopathy and headache or neck pain. Finite element analysis is a means of predicting stress due to load, deformity and strain. The authors postulate linkage between finite element analysis (FEA)-predicted biomechanical neuraxial stress and metrics of neurological function.Methods:A prospective, Internal Review Board (IRB)-approved study examined a cohort of 5 children with Chiari I malformation or basilar invagination. Standardized outcome metrics were used. Patients underwent suboccipital decompression where indicated, open reduction of the abnormal clivo-axial angle or basilar invagination to correct ventral brainstem deformity, and stabilization/ fusion. FEA predictions of neuraxial preoperative and postoperative stress were correlated with clinical metrics.Results:Mean follow-up was 32 months (range, 7-64). There were no operative complications. Paired t tests/ Wilcoxon signed-rank tests comparing preoperative and postoperative status were statistically significant for pain, bulbar symptoms, quality of life, function but not sensorimotor status. Clinical improvement paralleled reduction in predicted biomechanical neuraxial stress within the corticospinal tract, dorsal columns and nucleus solitarius.Conclusion:The results are concurrent with others, that normalization of the clivo-axial angle, fusion-stabilization is associated with clinical improvement. FEA computations are consistent with the notion that reduction of deformative stress results in clinical improvement. This pilot study supports further investigation in the relationship between biomechanical stress and central nervous system (CNS) function.

Surgical Results of Foramen Magnum Decompression for Chiari Type 1 Malformation associated with Syringomyelia:

To evaluate neuroradiological characters affecting postoperative shrinkage of syringes associated with Chiari type 1 malformation, we assessed 56 patients who underwent foramen magnum decompression (FMD) and were followed-up at least one year. In 48 cases (85.4%), the postoperative courses were quite satisfactory. The cerebellar tonsils have moved upward during surgery and the syringes have decreased in size on MRI taken one or three months after surgery (the prompt group). In eight of 56 patients (14.3%), however, the syringes were slow to shrink and remained over one year after surgery (the delayed group). Basilar impression was more common in the delayed group (p=0.026). These patients had a wider basal angle (142.6 degrees for the delayed group compared with 135.4 degrees for the prompt group), narrower clivo-axial angle (CAA; 121.7 and 142.8 degrees, respectively) and severely lordotic cervical spine (8.0mm and 4.5mm, respectively) on plain X ray films. Those with CAA narrower than 130 degrees showed significant delay in shrinking of the syringes. The CAA might be a good indicator to predict the time course of syrinx shrinkage after FMD.

Clinical and neuroimaging features of Chiari type I malformations with and without associated syringomyelia.

The clinical and neuroimaging characteristics of 22 consecutive patients with Chiari type I malformations were evaluated to investigate the pathogenesis of syrinx formation. All patients underwent magnetic resonance imaging and x-ray tomography before surgery. The electric manometric Queckenstedt test was performed on 16 patients pre- and postoperatively. Syringomyelia was present in 17 patients and absent in five patients. All patients without syringomyelia suffered from foramen magnum compression syndrome, with a wider basal angle, more acute clivo-axial angle, shorter clivus, and more prominent tonsillar ectopia than patients with syringomyelia. Low brain stem position, basilar impression, and beaking of the cervicomedullary junction were also more prominent in patients without syringomyelia. Marked to complete block with the neck in flexed position by Queckenstedt test was present in all patients except one. Patients with Chiari malformation not associated with syringomyelia have more pronounced compression of the brain stem at the foramen magnum. Therefore, despite a block of the cerebrospinal fluid pathway at the foramen magnum, syrinx formation may be prevented by severe compression.

Foramen Magnum Decompression for Syringomyelia Associated with Basilar Impression and Chiari I Malformation

Anterior or posterior decompression of the foramen magnum was performed in three patients with syringomyelia associated with basilar impression and Chiari I malformation. The operative results were evaluated using the pre- and postoperative magnetic resonance (MR) images. Two patients with combined anterior and posterior cervicomedullary compression due to basilar impression and tonsillar descent received suboccipital craniectomy, upper cervical laminectomy, and dural plasty without any intradural manipulations via the posterior approach. One patient with prominent anterior cervicomedullary compression due to basilar impression and a sharp clivoaxial angle was operated on by the transoral anterior approach. Postoperatively, all patients showed a sustained shrinkage of the syrinx and rounding of the flattened cerebellar tonsils. Two patients showed upward movement of the herniated tonsils. All patients had improved symptoms during 2-4 years follow-up. Treatment of syringomyelia associated with basilar impression and Chiari I malformation requires more efficient decompressive procedures at the foramen magnum based on neurological and MR findings.

Successful treatment of adult arnold-chiari malformation associated with basilar impression and syringomyelia by the transoral anterior approach

A case of adult type I Arnold-Chiari malformation associated with basilar impression, syringomyelia, atlantoaxial dislocation, and occipitalization of the atlas is reported. Preoperative magnetic resonance imaging clearly revealed evidence of severe anterior compression of the cervicomedullary junction due to basilar impression and a sharp clivoaxial angle. Therefore, transoral anterior decompression and fusion were performed, resulting in an improvement of the patient's neurologic signs and symptoms. Postoperative magnetic resonance imaging showed an obvious reduction of the tonsillar herniation and syringomyelia, as well as an improvement of the cervicomedullary compression.

Surgical Treatment for Chiari Malformations associated with Congenital Anomalies

Chiari malformations are often associated with congenital anomalies. The authors evaluated several surgical procedures for Chiari malformations associated with basilar impression and/or syringomyelia. Twenty patients with Chiari malformations with and without congenital anomalies were treated by various surgical procedures. Associated anomalies were atlantoaxial dislocation in one, basilar impression in eight, and syringomyelia in 11. There were 11 males and nine females, ranging in age from 6 to 63 years. Nine patients were treated by foramen magnum decompression (suboccipital craniectomy and upper cervical laminectomy), one by foramen magnum decompression combined with terminal syringostomy, one by anterior decompression via the transoral approach, and nine by syringosubarachnoid shunting. The period of follow-up ranged from 5 months to 21 years (mean, 7 years). Seventeen of the 20 patients showed neurological improvement, one was unchanged, and two deteriorated. One of the patients who deteriorated had undergone syringosubarachnoid shunting, and the shunt malfunctioned because of arachnoiditis. A patient with basilar impression died of respiratory failure after suboccipital craniectomy and upper cervical laminectomy. On the basis of their results, the authors recommend posterior decompression for patients with Chiari malformations alone. If a foramen magnum lesion is responsible for the neurological manifestations and the clivoaxial angle is narrow in Chiari malformations associated with basilar impression and/or syringomyelia, anterior decompression with fusion should be performed. If the clivoaxial angle is within normal limits, the authors perform posterior decompression. Syringosubarachnoid shunting appears effective in patients in whom syringomyelia is the main cause of neurological symptoms.

'Sneeze syncope', basilar invagination and Arnold-Chiari type I malformation.

Syncope precipitated by sneezing in an adult male associated with an Arnold-Chiari type I malformation and basilar invagination presents a clinical problem in the differential diagnosis and pathological anatomy of Valsalva-related syncope. An abnormally acute clivoaxial angle, small foramen magnum, and type I Arnold-Chiari malformation appear to be a combination of features intolerant of Valsalva-induced changes in cerebral volume, brain-stem position, CSF fluid dynamics, or blood vessel relationships. Proposed mechanisms of pressure transmission to the area of intracranial pathology are discussed.