A pathological study of intracranial aneurysms particularly of aneurysms other than saccular ones

The author has investigated grossly and microscopically 90 intracranial aneurysms among 63 individuals, autopsied at the Tokyo-to Medical Examiner Office and partly at the 2nd Department of Pathology, Showa University School of Medicine. These aneurysms consisted of 74 of the saccular type, 5 of the arteriosclerotic type, 6 of the spindle-shaped aneurysm of the vertebrals and 5 of the dolichoectatic type, respectively. In this paper, the author has discussed the differences of pathogenesis of the above mentioned four types of aneurysms. The saccular aneurysm is thought to occur from turbulence of blood stream by intimal thickening developing from "Verzweigungspolster" (VP) of Rotter at the neck of the aneurysm, and the arteriosclerotic aneurysm to occur by the same manner as the saccular one, superimposed on severe atherosclerosis during a long time. The spindle-shaped aneurysm of the vertebral arteries is thought to be of inflammatory nature, relating to slowness of blood stream in the vertebral arteries, and the dolichoectatic aneurysm to be due to hemodynamic disturbance of the vertebro-basilar artery system by means of atherosclerosis of the arterial walls neighboring to the top of the basilar artery.