To investigate the clinical efficacy of minimally invasive subpial tonsillectomy (MIST) in the treatment of Chiari malformation (type I) with syringomyelia.

A total of 209 Chiari malformation (type I) patients with syringomyelia were studied. The patients were grouped based on the syrinx diameter changes: complete disappearance group (48 patients), obvious shrinkage group (147 patients), and non-obvious shrinkage group (14 patients). The Chicago Chiari Outcome Scale (CCOS) was used to compare clinical data of the three groups of patients before treatment. The correlations between disease duration and syrinx diameter changes as well as post-treatment clinical symptoms were analyzed. The related factors of efficacy were analyzed.

Age and disease duration were the oldest/longest in the non-obvious shrinkage group, and the youngest/shortest in the complete disappearance group (P < 0.05). The maximum diameter reduction of syrinx was the greatest in the complete disappearance group, and the smallest in the non-obvious shrinkage group (P < 0.05). The proportions of patients with hypoesthesia, limb weakness, and muscle atrophy were the largest in the non-obvious shrinkage group, and the smallest in the complete disappearance group (P < 0.05). The CCOS score were the highest in the complete disappearance group, and the lowest in the non-obvious shrinkage group (P < 0.05). There were statistically significant (P < 0.05) negative correlations between disease duration and maximum diameter reduction of syrinx, CCOS pain score, CCOS non-pain score, CCOS functionality score, and CCOS complication score, disease duration and hypoesthesia, limb weakness, muscle atrophy, and sleep apnea. Result of multivariate stepwise regression analysis indicated that age, disease duration, and preoperative syrinx diameter were the risk factors for efficacy (P < 0.05).

For patients with Chiari malformation complicated by syringomyelia, the longer the disease duration, the more difficult it is to achieve syrinx reduction and improve the clinical symptoms. "Minimally invasive subpial tonsillectomy (MIST) and cisterna magna reconstruction" is an improved surgical approach to treat Chiari malformation (cerebellar tonsil herniation). It has the advantages of small incision, less postoperative reaction, and fewer complications, and it emphasizes the reshaping and repair of cerebellar tonsils, reconstruction of cisterna magna, and restoration of cerebrospinal fluid circulation.