A Simple, Practical, and Novel Approach to Evaluate the Radiological Outcomes of Adult Chiari Malformation 1

Author(s): Asifur Rahman, Nazmin Ahmed, Abu Saleh Mohammad Abu Obaida, Abu Naim Wakil Uddin, Bipin Chaurasia, Md Atikur Rahman, Md Shamsul Alam, Md Moududul Haque

Objective: Surgical techniques and outcomes of the enigmatic entity of Chiari malformation 1 (CM1) in the adult, which is often accompanied by syringomyelia (SM) vary widely and both the clinical and radiological outcomes are perplexing. The aims of this study were to assess the radiological outcomes of 2 surgical procedures namely the stealth cranioplasty (SC) and the posterior fossa decompression with or without duraplasty (PFD±DP) with the application of our novel approach to measure some radiological parameters.

Methods: This comparative cross-sectional study was conducted on adult CM1 patients with or without SM undergoing surgery by PFD±DP and SC from June 2019 to May 2021. Radiological outcomes of changes in pre and postoperative diameter of the foramen magnum (FM), the diameter of the SM, tonsillar position, and status of cisterna magna from computed tomography (CT) and/or magnetic resonance imaging (MRI) were evaluated and analyzed. The postoperative measurements of the FM diameter and tonsillar ectopia were measured by a new technique that we devised which has not been applied before.

Results: The study population comprised 37 male and 16 female (total of 53) symptomatic adult Chiari 1 malformation patients with or without SM ranging from 18 to 47 years of age (average 30.35 ± 7.49 years), where 30 (56.6%) underwent PFD±DP and 23 (43.4%) underwent SC. The postoperative change of the foramen magnum diameter was significantly better in the SC group (p 0.002) when an increase in the postoperative diameter was categorized as mild, moderate, and marked. And, while comparing the changes in millimeters, changes in the SC group were even better (p <0.001)

The postoperative tonsillar ascent was found to be significant (P <0.001) on both occasions when categorized into groups of mild, moderate, and marked, and when measured in millimeters. Postoperative SM size reduction was not significant when categorized as mild, moderate, and marked (p 0.085). However, when the changes were measured in millimeters, a significant reduction was observed in the SC groups (p 0.007). The postoperative appearance of Cisterna magna was found to be significant (p <0.001) in the SC group.

Conclusion: From this study, results of SC as a technique were found encouragingly to have better radiological outcomes in terms of postoperative changes in the diameter of the foramen magnum, tonsillar ascent, resolution of the SM, and postoperative appearance of cisterna magna. However, further multicenter studies on a larger population are recommended.

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