Intracranial aneurysms and arterial hypertension: A review and hypothesis

BACKGROUND Intracranial aneurysms and systemic arterial hypertension coexist in a high percentage of patients. The relationship between intracranial aneurysms an d hypertension is poorly defined. METHODS Therefore, we reviewed the role of hypertension in the pathogenesis of sacc ular aneurysms as previously reported in clinical, experimental, and autops y studies. RESULTS Among 24 relevant clinical and/or autopsy studies, the mean incidence of pr e-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 hypertensi on creates a greater risk for the development of intracranial aneurysms tha n previously believed. The underlying pathophysiological mechanism(s) are a lso 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 likel y the most important factors in initiating the development of aneurysms. Ch ronic hypertension potentially affects all of these factors. Consequently, chronic hypertension may cause intimal thickening, necrosis of the tunica m edia, changes in the compositional matrix, and degeneration of the internal elastic lamina to develop in the arterial wall. These structural changes c ould cause a focal weakening in the arterial wall with resultant bulging. T his theory accounts for the high incidence of intracranial aneurysms in the absence of any known associated hereditary or connective-tissue disease. N or does it exclude the possibility of other etiological factors. From the p erspective of prevention, however, it offers clear opportunities for prophy laxis. (C) 2000 by Elsevier Science Inc.