Three Dimensional Computed Tomographic Angiographyで診断した破裂動脈瘤の大きさと局在について

Size and Location of Ruptured Cerebral Aneurysms Diagnosed by Three Dimensional Computed Tomographic Angiography

I．はじめに

　Magnetic resonance angiography（以下MRA）やthree dimensional computed tomographic an-giography（以下3D-CTA）による動脈瘤診断の進歩^8,9,12）と，脳ドックの普及や外来でのMRAスクリーニングにより多くの未破裂動脈瘤が容易に見つかるようになり，脳血管撮影やdigital sub-traction angiography（以下DSA）でも見逃しそうな小さな動脈瘤までもが診断可能となった^14,15）．一方，これらの動脈瘤を手術するにあたり，小さな動脈瘤をどうするか，高齢者や難しい部位の未破裂動脈瘤の手術適応^11,13）をいかにするべきかについて議論されている．

　われわれは，最近2.0mm程度の小さな破裂動脈瘤を多く経験し，従来より報告されている破裂動脈瘤の大きさには疑問があり，未破裂動脈瘤の手術適応11,13）を考える上でも破裂する大きさの詳細な検討が必要と考えている．

The purpose of this study is to confirm the correct size and the location of ruptured cerebral aneurysmsdiagnosed and measured using three dimensional computed tomographic angiography. The size and thelocation were investigated in 136 ruptured cerebral aneurysms encountered in our hospital during 3 yearsand 10 months.

As regards the location of 136 ruptured cerebral aneurysms, 40 were anterior communicating arteryaneurysms, 35 were middle cerebral artery aneurysms, 33 were internal carotid artery aneurysms, 12 weredistal anterior cerebral artery aneurysms and 16 were posterior circulatory aneurysms. Twenty-seven aneu-rysms (19.9%) were smaller than 3.0 mm, and 74 aneurysms (54.4%) were less than 5.0mm in maximumdiameter. The maximum diameter of aneurysms located on the anterior communicating artery was 4.8mm.On the middle cerebral artery it was 6.7 mm, and on the internal carotid artery it was 7.4mm. We concluded that the rate of small aneurysmal rupture was comparatively more frequent than is report-ed. The results led to the speculation that the aneurysmal rupture occurred more often in smaller size, andthe rate of occurrence may be also related to the aneurysmal location.