An Examination of Morphological Characteristics and Surgical Outcomes in Type I Chiari Malformation: A Comparative Study

Introduction: When patients with Type I Chiari malformation (CMI) require surgical intervention to address their symptoms, understanding these symptoms can sometimes be less than straightforward. A crucial factor influencing the decision-making process is comprehending the unique characteristics of the posterior fossa in CMI patients. Considering this, our study aims to compare individuals diagnosed with CMI to the general population, seeking to uncover and delineate any discernible differences. Additionally, we explore how the presentation of CMI changes before and after surgical treatment.

Method: After the institutional review board approval, we conducted a retrospective imaging review of surgically treated CMI patients at a single institution from January 2010 to May 2022. Our methodology involved measuring parameters such as cerebellar width, 4th ventricle dimensions, cerebellar-to-Pons distance, cerebellar height, tentorial angle, and McRae line. We compared these measurements in a 2:1 ratio with individuals from the normal population and assessed differences between preoperative and postoperative Chiari patients ([Fig. 1]).

Fig. 1

Results:

Table 1

Among the 95 patients analyzed, significant morphological differences were found between CMI patients and the normal population in several aspects, including cerebellar width (CMI: 31.2 ± 3.96 mm vs. Control: 27.5 ± 3.79 mm; p < 0.001), 4th ventricle dimensions (CMI: 9.91 ± 2.96 mm vs. Control: 11.6 ± 1.56 mm; p < 0.001), cerebellar-to-Pons distance (CMI: 63.89 ± 4.95 mm vs. Control: 60.9 ± 4.89 mm; p < 0.001), cerebellar height (CMI: 64.89 ± 5.38 mm vs. Control: 47.6 ± 6.72 mm; p < 0.001), Tentorial angle (CMI: 47.35 ± 7.03 mm vs. Control: 41.0 ± 5.57 mm; p < 0.001), and McRae line width (CMI: 33.9 ± 2.79 mm vs. Control: 36.9 ± 3.18 mm; p < 0.001) in both preoperative and postoperative CMI patients. Notably, differences were observed in 4th ventricle dimensions (Preop: 9.91 ± 2.96 mm vs. Postop: 10.6 ± 2.2 mm; p = 0.007), cerebellar-to-Pons distance (Preop: 63.9 ± 4.95 mm vs. Postop: 64.8 ± 4.21 mm; p = 0.002), and cerebellar height (Preop: 64.9 ± 5.38 mm vs. Postop: 62.1 ± 4.89 mm; p < 0.001). No significant differences were observed in cerebellar width and Tentorial angle between preoperative and postoperative cases.

Table 2

Conclusion: This study found significant differences in various morphological aspects between CMI patients and controls. Postoperatively, some improvements in measurement were observed, but not in all parameters. For patients with CMI experiencing ambiguous symptoms, these parameters can aid in making more informed surgical decisions.

Publication History

Article published online:
05 February 2024