Division of Neurosurgery, Institute of Brain Diseases, Tohoku University School of Medicine, Sendai 982

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1 Tohoku J. exp. Med., 1979, 128, The Correlation between Hypertension in Past History and the Incidence of Cerebral Aneurysms RYUNGCHAN KWAK, KAZUO Mizoi, IRO SUZUKI RYUICHI KATAKURA and J Division of Neurosurgery, Institute of Brain Diseases, Tohoku University School of Medicine, Sendai 982 KWAK, R., Mizoi, K., KATAKURA, R. and Suzuki, J. The Coorelation b etween Hypertension in Past History and the Incidence of Cerebral A neurysms. T ohoku J. exp. Med., 1979, 128 (3), The incidence of hypertension i n past history was investigated in 811 cases of cerebral aneurysm. These cases were compiled from 1,000 cases of saccular aneurysm in which direct surgical operations for aneurysm were performed at our clinic during the period from June 1961 to September Of the 811 cases, 365 (45.0%) had hypertension in their past history; 185 (42.7%) out of 433 males and 180 (47.6%) out of 378 females. In the 5th decade of age, the incidence was significantly higher in the females than in the males, but no difference by sex was noted in other age groups. In the males from the 3rd to the 7th decade, the number of h ypertensives increased significantly with advancing age, whereas in the females a signfiicant difference was observed only between the 4th and 7th decades, the l atter including more hypertensives. The incidence of hypertensives in the aneurysm cases was compared with that in the Japanese population reported by Sasaki. This comparison revealed that in both sexes between the 4th and 6th decades, the incidence was significantly higher in the former, whereas no significant difference was noted between the two in the 7th decade. As to the location of aneurysms, only the multiple aneurysms group had a significantly greater number of hypertensives than single aneurysm group. These results agree with previous reports that cerebral aneurysm may occur more frequently in the hypertensives than in the normotensives. intracranial saccular aneurysm; hypertension in past history. Although various hypotheses concerning the mechanism of development of cerebral aneurysms have been proposed (Forbus 1930; Bremer 1943; Dandy 1944; Walker and Allergre 1954), no definitive theory has yet been established. We believe that the most reasonable explanation for the development of the commonly seen saccular aneurysm is that, at the defect in the media at an arterial bifurcation, an aneurysm arises as the blood pressure becomes too great a burden (Kwak and Suzuki 1974). Because it is thought that many hypertensives develop aneurysms (Takeshita et al. 1972; Murakami 1975), we have undertaken a study of the correlation between cerebral aneurysm and hypertension in past history in a large number of cases of cerebral aneurysm. Received for publication, August 11,

2 268 R. Kwak et al. SUBJECTS AND METHODS From 1,000 cases of cerebral aneurysm in which direct operations were performed at our clinic from June 1961 to September 1975, 811 cases were selected for the present study. They all had a well documented record of blood pressure. In the record, either a systolic pressure higher than 150 mmhg or a diastolic pressure higher than 90 mmhg was regarded as hypertension. Since the documentation of symptom of hypertension or treatment for it was not always complete in our cases, these points were left out of con airl.ration in the present study. Among the 811 cases of cerebral aneurysm, 433 were male (53.4%) and 387 were female (46.6%). The sex and age distributions of these cases are shown in Table 1. TABLE 1. Incidence of hypertension in past history in 811 cases of saccular aneurysm * Numbers in parentheses represent the percentages With regard to the location of the aneurysms, 274 (33.8%) were on the anterior communicating artery, 195 (24.0%) on the internal carotid artery, 146 (18.0%) on the middle cerebral artery, 40 (4.9%) on the anterior cerebral artery, 20 (2.5%) on the vertebral and basilar arteries, and 136 (16.8%) were cases of multiple aneurysms (Table 2). Finally, of the total 811 cases, 794 (97.9%) were of ruptured aneurysm and 17 (2.1%) were of unruptured one. The incidence of hypertension in histories of the 811 cases was investigated statistically. The chi-square test was used for the statistical examination. RESULTS Of the 811 cases, 365 (45.0%) had a history of hypertension; 185 (42.7%) of the 433 male cases, and 180 (47.6%) of the 378 female cases. No significant difference by sex was found. Comparing the numbers and percentages of hypertensive cases in males and females in each decade of age, a significant difference by sex was found only in the 5th decade. Here the incidence of hypertension was higher in females than in males (p<0.05) (Table 1).

3 Hypertension and Cerebral Aneurysms 269 TABLE 2. Incidence of hypertension in past history by location of aneurysm * Denominator, number of patients with aneurysm; numerator, number of aneurysm patients with hypertension in past history. Numbers in parentheses represent the percentages. A com, anterior communicating artery; IC, internal carotid artery; MC, middle cerebral artery; AC, anterior cerebral artery; V-B, vertebro-basilar artery; Mult, multiple aneurysm. Making a comparison between age groups of the male cases, no significant difference in the incidence was found between the 3rd and 4th, or the 4th and 5th decades. The 2nd and 8th decade groups consisted of too small a number of cases for comparison. There was, however, a significant difference between any two of other age groups; the incidence was always higher in the older age groups (p<0.05). On the whole, the incidence of hypertension rose with advancing age. On the other hand, in the female cases (with the exception of the 2nd, 3rd and 8th decades) a significant difference was found only between the 4th and 7th decades (p<0.05). Considering the male and female cases from the 3rd to the 7th decade together, there was no significant difference between the 4th and 5th or between the 5th and 6th decades, but significant differences were found between the 3rd and 4th decades (p<0.01), the 4th and 6th decades (p<0.05), and the 6th and 7th decades (v<0.05) (Table 1). With regard to the location of aneurysms, only the cases of multiple aneurysms showed a significantly high incidence of hypertension in the case history as compared with the cases of other locations (p<0.05); there were no significant differences among the cases of any other locations. In the analysis of our data, we attempted to answer a question whether or not cerebral aneurysm is apt to be associated with a history of hypertension. For comparison, we used Sasaki's (1975) calculations of the incidence of hyperten sion at each age bracket in the Japanese population based upon National Nutrition Surveys until Since Sasaki calculated the incidence of systolic pressures higher than 150 mmhg and diastolic pressures higher than 90 mmhg in 5 year age brackets, we used the average value for each decade of age for the comparison with our data. The numbers of our cases in the 2nd and 8th decades were so small that we excluded these age groups from this study. In the male, the incidence of hypertension in the cases of cerebral aneurysm was higher than that of either systolic or diastolic hypertension in the Japanese population in each

4 270 R. Kwak et al. decade of age from the 3rd to the 7th (Table 3). As compared with systolic hypertension in the Japanese population, this high incidence of hypertension in the cases of cerebral aneurysm was statistically significant at a level of p<0.01 in the 3rd through the 6th decades, whereas it was not significant in the 7th decade. As compared with diastolic hypertension, this high incidence was significant at a level of p<0.05 in the 3rd and 6th decades, and at a level of p<0.01 in the 4th and 5th decades, whereas it was not significant in the 7th decade. In the female, the incidence of hypertension in the cases of aneurysm was significantly high, as compared with systolic hypertension in the Japanese population, at a level of p< 0.01 in the 4th and 5th decades and p<0.05 in the 6th decade, whereas it was not significant in the 3rd or 7th decade. Similarly, as compared with diastolic hypertension, it was significant at a level of p<0.01 in the 4th, 5th, and 6th decades, whereas it was not significant in the 3rd or 7th decade (Table 4). Thus, the incidence of hypertension was higher in the cases of cerebral aneurysm than in the general Japanese population in most decades of age and in both sexes. TABLE 3. Incidence of aneurysm patients with hypertension in past history and of Japanese with hypertension in male * Numbers represent the percentages. TABLE 4. Incidence of aneurysm patients with hypertension in past history and of Japanese with hypertension in female * Numbers represent the perc entages.

5 Hypertension and Cerebral Aneurysms 271 DISCUSSION The present investigation revealed that patients with cerebral aneurysm have a history of hypertension more often than the general Japanese population. There have been numerous reports (Takeshita et al. 1972; Murakami 1975) that hypertensives often have a fit of cerebral apoplexy. Takeshita et al. (1972) have reported a 7-year study of 1,621 cases at Hisayama Town, Fukuoka prefecture, in which 70 to 410 hypertensives (17%), 20 of 344 cases of borderline hypertension (5.8%), and 14 of 867 normotensives (1.6%) developed cerebral apoplexy. This report clearly shows a correlation between cerebral apoplexy and hypertension. Furthermore, a 3-year study by Takeshita et al. (1972) showed that, out of 407 hypertensives, 19 (4.6%) had cerebral infarction, 5 (1.2%) had intra cerebral hemorrhage, and 4 (1.0%) had subarachnoid hemorrhage; of 269 borderline hypertensives, 7 (2.6%) had cerebral infarction, 1 (0.4%) had intracerebral hemor rhage, and 2 (0.7%) had subarachnoid hemorrhage; and that, of 654 normotensives, only 1 (0.2%) had intracerebral hemorrhage, but none had cerebral infarction or subarachnoid hemorrhage. This clearly indicates that even subarachnoid hemorrhage occurs more often in the hypertensives and borderline hypertensives than in the normotensives. A correlation of the development of cerebral aneurysm and its rupture with hypertension is evident. References 1) Bremer, J.L. (1943) Congenital aneurysms of the cerebral arteries. An embryologic study. Arch. Path., 35, ) Dandy, W.E. (1944) Intracranial Arterial Aneurysms. Comstock Publishing Company, Ithaca, N.Y. 3) Forbus, W.D. (1930) On the origin of miliary aneurysm of the superficial cerebral aertiers. Bull. Johns Hopk. Hosp., 47, ) Kwak, R. & Suzuki, J. (1974) Correlation of anterior communicating artery aneurysms with blood circulation at the anterior part of the cricle of Willis and its vascular anomalies. Phronesis, 11, ) Murakami, M. (1975) Complications of hypertension. In: Hypertension, edited by H. Ueda, Nankodo, Tokyo, pp (Japanese) 6) Sasaki, N. (1975) Epidemiology of Hypertension. In: Hypertension. edited by H. Ueda, Nankodo, Tokyo, pp (Japanese) 7) Takeshita, S., Hirota, Y., Katsuki, S., Nakano, M., Tanaka, S., Ikeda, H., Hiyoshi, U. & Ueda, K. (1972) Epidemiologic study of hypertension. Jap. J. clin. exp. Med., 149, (Japanese) 8) Walker, A.E. & Allergre, G.W. (1954) The pathology and pathogenesis of cerebral aneurysms. J. Neuropath.. exp. Neural., 13,

Hemodynamics in the Anterior Part of the Circle of Willis in Patients with Intracranial Aneurysms : A Study by Cerebral Angiography

Tohoku J. exp. Med., 1980, 132, 69-73 Hemodynamics in the Anterior Part of the Circle of Willis in Patients with Intracranial Aneurysms : A Study by Cerebral Angiography RYUNGCHAN KWAK, HIROSHI NIIZUMA