Assessment of the topographic relationship between the inion and the sinus confluence using 3D-CTA

The inion is one of the landmarks for craniotomy around the sinus confluence. However, the distance between these structures varies among individuals. We assessed the relationship between the inion and the sinus confluence. Three dimensional-computed tomographic angiography (3D-CTA) in 25 cases were evaluated using following 3 assessments. One was the difference of height between the inion and the sinus confluence. The second was the deviation of the sinus confluence from the inion. The last was the side dominance of the transverse sinus. The inion was under the sinus confluence in all cases. The difference of the height between the inion and the sinus confluence was 13.6±7.2 mm (0-28 mm). The sinus confluence was not deviated from the inion in 9/25 (36%), deviated to right in 14/25 (56%), deviated to left in 2/25 (8%). The sinus confluence was symmetric in 18/25 (72%), right dominant in 7/25 (28%), left dominant in none. The distance between the inion and the sinus confluence varies widely among individuals. For craniotomies around the sinus confluence, assessment of the topographic relationship between the inion and the sinus confluence preoperatively using 3D-CTA makes surgery much safe and more accurate. (author)