It remains unclear which subgroups of scoliotic patients with CMI and syringomyelia are more likely to undergo unplanned neurosurgery after spinal deformity correction. The purpose of this study is to explore risk factors of unplanned neurosurgery for scoliotic patients with CMI and syringomyelia after spinal deformity correction.
This cohort consisted of 62 scoliotic patients with CMI and syringomyelia who underwent spinal deformity surgery with a mean follow-up of 4.3 year. 14 of them underwent unplanned neurosurgery (the NN group), and the other 48 patient underwent single spinal correction surgery (the SS group). The radiological parameters were compared between the two groups, and multivariate logistic regression analysis and Kaplan-Meyer survival curves were used to identify potential risk factors of unplanned neurosurgery.
The incidence of unplanned neurosurgery after spinal deformity surgery was 22.28 % (14/62), and delayed headache was the most common reason for unplanned neurosurgery with five patients (36 %) and follow by neck pain with three patients (21 %). Significantly increased tonsil ectopia (9.7 ± 3.8 vs. 6.9 ± 2.9; P = 0.021), syrinx/cord width ratio (0.62±0.11 vs. 0.45±0.13; P＜0.001), and syrinx/cord area ratio (0.45 ± 0.11 vs. 0.26 ± 0.15; P＜0.001) were found in the NN group. While, there were no significant differents in pBC2 line, clivus canal angle, and syrinx length between the two groups. The logistic regression analysis indicated that tonsil ectopia≥10 mm (P = 0.019; OR=6.440; 95 %CI = 1.361 to 30.467) and syrinx/cord area ratio ≥ 0.4 (P = 0.006; OR=7.664; 95 %CI = 1.819 to 32.291) were independent risk factors of unplanned neurosurgery. Kaplan-Meyer survival curves showed cumulative unplanned neurosurgery for patients with tonsil ectopia ≥ 10 mm (P < 0.001) and syrinx/cord area ratio ≥ 0.4 (P = 0.001) after spinal deformity correction.
After spinal deformity correction, 78 % of the patients did not require later neurosurgery and those that needed it had a delay of more than nine months. Tonsil ectopia ≥ 10 mm and syrinx/cord area ratio ≥ 0.4 were independent risk factor of unplanned neurosurgery after spinal deformity correction. It is reasonable to perform spinal corrective surgery in patients with minimal symptoms and signs without the need for prior neurosurgical intervention.

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