Elsevier

Surgical Neurology

Volume 53, Issue 6, 1 June 2000, Pages 530-542
Surgical Neurology

Original article
Intracranial aneurysms and arterial hypertension: a review and hypothesis

https://doi.org/10.1016/S0090-3019(00)00244-5Get rights and content

Abstract

BACKGROUND

Intracranial aneurysms and systemic arterial hypertension coexist in a high percentage of patients. The relationship between intracranial aneurysms and hypertension is poorly defined.

METHODS

Therefore, we reviewed the role of hypertension in the pathogenesis of saccular aneurysms as previously reported in clinical, experimental, and autopsy studies.

RESULTS

Among 24 relevant clinical and/or autopsy studies, the mean incidence of pre-existing hypertension was 43.5% in aneurysm patients compared to 24.4% in the normal population. Although definitive evidence is lacking, data from multiple types of investigations indicate that systemic arterial hypertension creates a greater risk for the development of intracranial aneurysms than previously believed. The underlying pathophysiological mechanism(s) are also poorly defined.

CONCLUSIONS

We propose a unifying hypothesis: Endothelial injury, occlusion of the vasa vasorum, and disruption of the synthesis of collagen and elastin are likely the most important factors in initiating the development of aneurysms. Chronic hypertension potentially affects all of these factors. Consequently, chronic hypertension may cause intimal thickening, necrosis of the tunica media, changes in the compositional matrix, and degeneration of the internal elastic lamina to develop in the arterial wall. These structural changes could cause a focal weakening in the arterial wall with resultant bulging. This theory accounts for the high incidence of intracranial aneurysms in the absence of any known associated hereditary or connective-tissue disease. Nor does it exclude the possibility of other etiological factors. From the perspective of prevention, however, it offers clear opportunities for prophylaxis.

Section snippets

Clinical studies

Only clinical series with more than 50 patients with aneurysms that also stated the incidence of premorbid (preexisting) hypertension were included in this study 13, 23, 34, 44, 46, 52, 53, 54, 57, 64, 73, 85, 87, 101, 109, 114.

In 1979, Andrews and Spiegel [2] examined the relationship between blood pressure and aneurysms in 212 unselected patients. Hypertension was not significantly more prevalent in patients with aneurysms than in an age-matched general control group. Juvela [44] and Ohman

Experimental studies

Experimental studies 36, 38, 39, 48, 51, 66, 97, 111 confirmed the findings of these clinical studies. Several authors demonstrated that hypertension and hemodynamic stress play an important role in the formation of aneurysms. For example, Hashimoto et al 38, 39 induced cerebral aneurysms in the presence of hypertension in rats and monkeys using carotid ligation and β-aminoproprionitrile, which is a lathyrogen. Lathyrogens cause connective tissue abnormalities and fragility. Nagata et al [67]

Autopsy studies

Only autopsy studies 3, 14, 19, 21, 70, 93, 116, 120 with more than 25 cases were included in this review. Although some autopsy studies failed to find an association between hypertension and aneurysm formation [63], most have documented a close correlation. In these autopsy studies, blood pressure was determined from the patient’s medical record preceding admission and/or myocardial (left ventricular) hypertrophy.

In 1954, Wilson et al [120] performed an autopsy study of patients with ruptured

A proposed hypothesis

Although definitive studies on the role of hypertension in aneurysmal formation are lacking, the combined data from clinical, experimental, and autopsy studies strongly suggest that systemic arterial hypertension is a more important risk factor in the development of intracranial aneurysms than previously suspected. However, what is the pathophysiological mechanism(s) underlying this increased incidence of aneurysmal formation associated with hypertension? We propose that three processes are

Conclusions

Chronic hypertension causes intimal thickening, medial necrosis, changes in the matrix composition, and degeneration of the internal elastic lamina to develop in the arterial wall. Weakening of the arterial wall by these structural changes would likely lead to focal dilatation and the initial bulging of the arterial walls. Eventually, an aneurysm would develop (Figure 1). Endothelial injury, degeneration of the internal elastic lamina, and thinning of the media smooth muscle cells are early

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