Anatomical Variations in Pneumatization of the Anterior Clinoid Process

Object: An anterior clinoidectomy can provide enormous benefits, facilitating the management of paraclinoid and upper basilar artery lesions, but it also carries the potential risk of cerebrospinal fluid leaks. The aim of this study was to assess the variation in the pneumatization of the anterior clinoid process (ACP) in an attempt to reduce the complications associated with an anterior clinoidectomy.

Methods: The authors analyzed the anatomical variations in the pneumatization of the ACP and optical strut (OS) in 600 sides of 300 consecutive patients by using multidetector-row computed tomography (CT). Computed tomography scans with a 0.5-mm thickness were obtained, and coronal and sagittal reconstructions of the images were displayed in all cases. Pneumatization of the ACP was found in 9.2% of all sides. The origin of pneumatization was the sphenoid sinus in 81.8% of all the sides, the ethmoid sinus in 10.9%, and both of these sinuses in 7.3%. Pneumatized patterns were divided into three groups according to the route: 74.5% were Type I, in which pneumatization occurred via the OS; 14.5% were Type II, pneumatization via the anterior root (AR); and 10.9% were Type III, pneumatization via both the OS and the AR. The origin of pneumatization and the pneumatization pattern showed statistical dependence (p < 0.001). Pneumatization of the OS beyond its narrowest point was found in 6.8% of all sides.

Conclusions: An awareness of the different variations in pneumatization can prevent destruction of the mucous membrane and facilitate orientation during reconstruction with cranialization. During an anterior clinoidectomy, preoperative CT assessments are necessary to evaluate pneumatization of the ACP.