[Presurgical evaluaton for lateral suboccipital craniotomy using contrast-enhanced CT volumetric imaging]

To safely and precisely accomplish lateral suboccipital craniotomy (LSOC), we have presurgically evaluated the three-dimensional (3-D) relationships of various vascular structures and cranial landmarks in the occipito-cervical region by volumetric imaging of 3-D contrast enhanced computed tomography (CECT). The 3-D anatomies visualized by adjusting the window width, window level, and opacity level of the specific CT value for each structure were an occpital artery (OA), mastoid and posterior condylar emissary veins (MEV and PCEV), which were useful in dissecting muscles and exposing the cranial surface, and the relationship of the transverse-sigmoid sinus CTSS) and the asterion, which was necessary and decisive for making a key burr hole to perform craniotomy. The morphologic analysis for our 48 cases with cerebello-pontine angle tumor or neurovascular compression syndrome showed running patterns of OA, varieties of MEV and PCEV in their sizes and connections, right dominance of TSS, and the various relationship between the TSS and the asterion. Especially, the exact location of the TSS compared to the astenon was found to be inferior in 56%, right below in 38%, and superior in 6%. In conclusion, presurgical evaluation using volumetric imaging of 3-D CECT is a convenient and valuable method for obtaining the anatomic information required for performing LSOC safely and precisely in individual patients.