Changes in CSF flow after one-stage posterior vertebral column resection in scoliosis patients with syringomyelia and Chiari malformation Type I

Clinical article

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Object

Phase contrast–cine MRI (PC-cine MRI) studies in patients with syringomyelia and Chiari malformation Type I (CM-I) have demonstrated abnormal CSF flow across the foramen magnum, which can revert to normal after craniocervical decompression with syrinx shrinkage. In order to investigate the mechanisms leading to postoperative syringomyelia shrinkage, the authors studied the hydrodynamic changes of CSF flow in the craniocervical junction and spinal canal in patients with scoliosis associated with syringomyelia after one-stage deformity correction by posterior vertebral column resection.

Methods

Preoperative and postoperative CSF flow dynamics at the levels of the foramen magnum, C-7, T-7 (or apex), and L-1 were assessed by electrocardiogram-synchronized cardiac-gated PC-cine MRI in 8 adolescent patients suffering from severe scoliosis with syringomyelia and CM-I (scoliosis group) and undergoing posterior vertebral column resection. An additional 8 patients with syringomyelia and CM-I without spinal deformity (syrinx group) and 8 healthy volunteers (control group) were also enrolled. Mean values were obtained for the following parameters: the duration of a CSF cycle, the duration of caudad CSF flow (CSF downflow [DF]) and cephalad CSF flow (CSF upflow [UF]), the ratio of DF duration to CSF cycle duration (DF%), and the ratio of UF duration to CSF cycle duration (UF%). The ratio of the stationary phase (SP) duration to CSF cycle duration was calculated (SP%). The maximum downflow velocities (VDmax) and maximum upflow velocities (VUmax) were measured. SPSS (version 14.0) was used for all statistical analysis.

Results

Patients in the scoliosis group underwent one-stage posterior vertebral column resection for deformity correction without suboccipital decompression. The mean preoperative coronal Cobb angle was 102.4° (range 76°–138°). The mean postoperative Cobb angle was 41.7° (range 12°–75°), with an average correction rate of 59.3%. During the follow-up, 1 patient with hypermyotonia experienced a significant decrease of muscle tension and 1 patient with reduced anal sphincter tone manifested recovery. A total of 5 patients demonstrated a significant decrease (> 30%) in syrinx size. With respect to changes in CSF flow dynamics, the syrinx group was characterized by slower and shorter downflow than the control group, and the difference was more significant at the foramen magnum and C-7 levels. In patients with scoliosis, CSF downflow at the foramen magnum level was significantly restricted, and a prolonged stationary phase indicated increased obstruction of CSF flow. After posterior vertebral column resection, the peak velocity of CSF flow at the foramen magnum increased, and the downflow phase duration was markedly prolonged. The parameters showed a return to almost normal CSF dynamics at the craniocervical region, and this improvement was maintained for 6–12 months of follow-up.

Conclusions

There were distinct abnormalities of CSF flow at the craniocervical junction in patients with syringomyelia. Abnormal dynamics of downflow could be aggravated by associated severe spinal deformity and improved by correction via posterior vertebral column resection.

Abbreviations used in this paper:AP = anterior-posterior; CM-I = Chiari malformation Type I; DF = downflow; PC-cine MRI = phase contrast–cine MRI; SP = stationary phase; UF = upflow; VDmax = maximum downflow velocities; VUmax = maximum upflow velocities.

Article Information

Address correspondence to: Jingming Xie, M.D., Department of Orthopaedics, 2nd Affiliated Hospital of Kunming Medical University, Kunming, Yunnan Province 650101, China. email: xiejingming@vip.163.com.

Please include this information when citing this paper: published online March 1, 2013; DOI: 10.3171/2013.1.SPINE12366.

© AANS, except where prohibited by US copyright law.

Headings

Figures

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    The peak velocity–time curve in healthy adolescents, shown during a CSF flow cycle that corresponded to a cardiac cycle, including stationary phase (SP), craniad flow (upflow) phase, and caudad CSF flow (downflow) phase. The start point of downflow (DS), the maximum downflow velocities (VDmax), and maximum upflow velocities (VUmax) were noted.

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    Images obtained in a 17-year-old boy with CM-I and syringomyelia and severe kyphoscoliosis, who underwent one-stage posterior vertebral column resection. A and B: Preoperative photographs. C and D: Radiographs showing severe deformity in both the coronal plane and the sagittal plane. E and F: Sagittal and axial MR images showing cervical syringomyelia that was not only confined to the cervical region of the spinal cord, but also extended to the thoracic portion. G and H: Photographs obtained 3 months after posterior vertebral column resection with posterior pedicle screw fixation. I and J: Radiographs showing deformity correction. K and L: Follow-up MR images obtained 3 months postoperatively. There were no significant differences in the range of syringomyelia compared with before surgery, but the maximum AP diameter of the syrinx was significantly reduced.

  • View in gallery

    Representative example of phase-contrast MRI studies in a patient with cervical syringomyelia. A: Sagittal MR image showing cervical syringomyelia. Axial PC-cine MRI was performed at the level of the foramen magnum, indicated on the sagittal image. B and C: Curves of peak velocity versus time (B) and net flow versus time (C) were obtained for CSF flow at the level of the foramen magnum after CSF flow analysis by means of the Argus postprocessing program. The 4 curves in different colors represent the results of 4 regions of interest on the level of the foramen magnum.

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