Three-dimensional CT Angiography（3D-CTA）の頭蓋底静脈描出能の検討—subtemporal approachへの利用

Detection of the Venous System of the Skull Base Using Three-dimensional CT Angiography (3D-CTA) : utility of the subtemporal approach

I．はじめに

　近年脳動脈瘤の診断などを中心に頭蓋内動脈系の検索にthree-dimensional computed tomogra-phy angiography（3D-CTA）が広く用いられるようになった^11-13）．それに伴い同時に描出される静脈系の判読のための知識も必要となっているが，正常の静脈とそのバリエーションに関して述べた報告はほとんどない^5）．一方，頭蓋内の手術を行う場合，頭蓋内静脈系のバリエーションを充分理解し，各症例でその走行を正確に把握しておくことはきわめて重要である．今回われわれはinfe-rior temporal veinの検索に3D-CTAを用い，その描出能とバリエーションをdigital subtractionangiography（DSA）と比較し検討した．subtem-poral approachに関係する静脈系検索への3D-CTAの利用について考察し報告する．

Three-dimensional computed tomography angiography (3D-CTA) was compared with digital subtractionangiography (DSA) for the delineation of the skull base venous system in presurgical planning of the sub-temporal approach in 201 sides of 109 patients. The axial stereoscopic images and multi-projection imageswere used in 3D-CTA, and the anteroposterior views and lateral views were used in DSA. DSA showedthat the vein of Labbé (VL) was the most common venous flow on the lateral or basal surface of thetemporal lobe, whereas 3D-CTA demonstrated that the involvement of the temporo-basal vein (TBV) wasequal to that of VL in frequency. 3D-CTA showed that the VI. flowed into the transverse sinus (TS) on132 sides, the sigmoid sinus-TS junction on 29 sides, and the lateral tentorial sinus (LTS) on 40 sides. DSAshowed that the VI. flowed into the TS on 157 sides and into the LTS only on 5 sides. DSA showed thatthe TBV flowed into the TS on 37 sides but axial 3D-CTA showed that the TI3V flowed into the LTS on48 sides. This inconsistency reflects the difficulty in confirming and identifying these veins on the antero-posterior view of DSA, clue to the overlapping of veins and poor delineation. Axial stereo and multi-pro-jection images of 3D-CTA provided practical images of the deep veins of the skull base venous system andshowed the relative anatomical relationships of the arteries and bony structures. This information can spe-cify the venous inflow point, and help to determine the direction of approach and working space, and alsohelp to identify intraoperative landmarks for the subtemporal approach. Presurgical examination of thedeep venous system with 3D-CTA may help to minimize unexpected injury to veins and venous infarction.