Chiari I malformation has been shown to present different cerebrospinal fluid (CSF) flow patterns at the cranial-vertebral junction (CVJ). Posterior fossa decompression is the first-line treatment for symptomatic Chiari I malformation. However, there is still controversy on the indication and selection of decompression procedures. This research aims to investigate the clinical indications, outcomes, and complications of the decompression procedures as alternative treatments for Chiari I malformation, based on the different CSF flow patterns at the cranial-vertebral junction. In this study, 126 Chiari I malformation patients treated with the two decompression procedures were analyzed. According to the preoperative findings obtained by using cine phase-contrast MRI (cine PC-MRI), the abnormal CSF flow dynamics at the CVJ in Chiari I malformation was classified into three patterns. After a preoperative evaluation and an intraoperative ultrasound after craniectomy, the two procedures were alternatively selected to treat the Chiari I malformation. The indication and selection of the two surgical procedures, as well as their outcomes and complications, are reported in detail in this work. Forty-eight patients underwent subdural decompression (SDD), and 78 received subarachnoid manipulation (SAM). Ninety patients were diagnosed as having Chiari I malformation with a syrinx. Two weeks after the operation, the modified Japanese Orthopedic Association (mJOA) scores increased from the preoperative value of 10.67 ± 1.61 to 12.74 ± 2.01 (P < 0.01). The mean duration of follow-up was 24.8 months; the mJOA scores increased from the postoperative value of 12.74 ± 2.01 to 12.79 ± 1.91 at the end of follow-up (P = 0.48). More complications occurred in the patients who underwent SAM than in those who received SDD (SAM 11 of 78 (9.5%) vs SDD 2 of 48 (3.5%)). The abnormal CSF flow dynamics at the CVJ in Chiari I malformation can be classified into three patterns. A SAM procedure is more feasible in Chiari I malformation (CM1) patients with pattern III CSF flow dynamics, whereas a SDD procedure is more suitable for CM1 patients with pattern I CSF flow dynamics. In CM1 patients with pattern II CSF flow dynamics, an intraoperative ultrasound after craniectomy could play an important role in the selection of an effective decompression procedure.

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Objective To describe the different pathological characteristics of congenital basilar invaginations and discuss the surgical treatment of such cases. Methods A total of 139 patients diagnosed with basilar invaginations underwent surgical treatment from 2008 to 2015. Based on Atul Goel's classification and simultaneous consideration of atlantoaxial dislocation or syringomyelia, the cases were subdivided into four groups. Individualized posterior surgical decompression and/or atlantoaxial reset procedures were performed to correct atlantoaxial dislocation, decompress the brain stem, or resolve syringomyelia. The indications and critical points of each procedure were documented. Results All 139 patients were surgically treated; 27 patients (19.4%) had underwent at least one decompression surgery previously. On an average, there was gratifying clinical improvement based on the Japanese Orthopaedic Association score analysis. One patient exhibited severe postoperative infection, and the fusion instrument was removed. One patient experienced fracture of internal fixation. Two patients exhibited persistent respiratory symptoms at early stages after the surgery. Four patients felt worse at the latest follow-up. There was no surgical mortality. The poor outcome/ morbidity in this series was 5.8% (8/139). Conclusion The different pathological image characteristics of congenital basilar invaginations based on the presence or absence of syringomyelia and/or atlantoaxial dislocation, reflected the pathological features of complicated basilar invaginations more accurately. Based on these features, different posterior decompression and/or reset procedures, combined with occipitocervical fusion and C1-2 fusion, could be tailored to different patients. These individualized surgeries could reduce surgical complications, decrease morbidity and mortality, and further promote positive outcomes.

The findings of this study demonstrate that using conventional instruments to perform SSLS is technically feasible and safe in children. Although SSLS appendectomy does increase the operative time, it does not increase the complication rate and hospital cost.