Assessment of the Anterior Clinoid Process and Optic Strut in Chiari Malformation Type I: A Computed Tomography Study.

Objective  This study aimed to evaluate morphological features of the anterior clinoid process (ACP) and the optic strut (OS) in Chiari malformation Type I (CM-I). Methods  The study universe consisted of computed tomography images of 41 CM-I patients and 45 normal subjects. Comparison of the parameters for CM-I and the control group was performed with the Student's t -test. A " p  < 0.05" was accepted as the significance level. Results  ACP length was smaller in CM-I than the control group ( p  < 0.001). In contrast to ACP length, ACP angle ( p  < 0.001), OS length ( p  = 0.022), and the distance between ACP and OS ( p  = 0.020) were found greater in CM-I in comparison to the control group ( p  < 0.05). ACP width ( p  = 0.233) and OS width ( p  = 0.376) were similar in both groups. ACP pneumatization in CM-I group was found as 12.20%, whereas in the control group as 8.90%. Two different types about the pneumatization were identified in CM-I group (Type 1: 4.9% and Type 2: 7.3%), whereas three different types in the control group (Type 1: 3.3%, Type 2: 4.4%, and Type 3: 1.1%). Relative to ACP, three different types about OS position were identified in CM-I group (Type C: 31.70%, Type D: 64.60%, and Type E: 3.70%) and the control group (Type C: 7.80%, Type D: 64.40%, and Type E: 27.80%). Conclusion  Shorter ACP, wide-angled ACP, longer OS, and more anteriorly located OS were found in CM-I group compared with the normal group. Our findings showed that the pneumatization of ACP was not affected by CM-I.