In the authors' experience, emergency EC-IC bypass in patients with acute ischemic injury was both safe and effective. This population was characterized by relatively young patients with severely limited collateral circulation. In this series of 13 carefully selected patients, bypass was successful in arresting progression of stroke, and in some cases resulted in rapid neurological improvement.

The use of HBO in TBI remains controversial. Growing evidence, however, shows that HBO may be a potential treatment for patients with severe brain injury. Further investigations, including a multicenter prospective randomized clinical trial, will be required to definitively define the role of HBO in severe TBI.

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T he risk of intracranial aneurysm formation and subarachnoid hemorrhage (SAH) is higher in postmenopausal women compared with premenopausal women. 8,13,18,19,28 Reduced levels of estrogen in postmenopausal women may increase the risk of aneurysm formation and rupture by reduction in collagen and elastin content and reduced elasticity of arterial walls. 3 In an experimental intracranial aneurysm mouse model, estrogen prevented aneurysmal rupture in ovariectomized mice. 30The protective effect of estrogen seemed to occur through activation of estrogen receptor-b, a predominant subtype of estrogen receptor in human intracranial aneurysms and cerebral arteries. Hormone replacement therapy (HRT) was associated with reduced risk of spontaneous SAH in postmenopausal women in most 19,22 but not all case control studies. 25 The Women's Health Initiative (WHI) randomized trial 33 assessed the effect of estrogen plus progestin on ischemic and hemorrhagic stroke in 608 women 50-79 years of age with an average follow-up of 5.6 years. There was a nonsignificant protective effect on hemorrhagic stroke (HR 0.82, 95% CI 0.43-1.56). However, the study was underpowered because there were only 10 SAH events among the randomized patients. A meta-analysis 24 found a small nonsignificant protective effect of HRT on risk of SAH (HR 0.8, 95% CI 0.57-1.04).We performed this study to determine the effect of abbreviatioNs HRT = hormone replacement therapy; RR = relative risk; SAH = subarachnoid hemorrhage; SE = standard error; WHI = Women's Health Initiative. obJective The incidence of subarachnoid hemorrhage (SAH) increases after menopause. Anecdotal data suggest that hormone replacement therapy (HRT) may reduce the rate of SAH and aneurysm formation in women. The goal of this study was to determine the effect of HRT on occurrence of SAH in a large prospective cohort of postmenopausal women. methods The data were analyzed for 93,676 women 50-79 years of age who were enrolled in the observational arm of the Women's Health Initiative Study. The effect of HRT on risk of SAH was determined over a period of 12 ± 1 years (mean ± SD) using Cox proportional hazards analysis after adjusting for potential confounders. Additional analysis was performed to identify the risk associated with "estrogen only" and "estrogen and progesterone" HRT among women. results Of the 93,676 participants, 114 (0.1%) developed SAH during the follow-up period. The rate of SAH was higher among women on active HRT compared with those without HRT used (0.14% vs 0.11%, absolute difference 0.03%, p < 0.0001). In unadjusted analysis, participants who reported active use of HRT were 60% more likely to suffer an SAH (RR 1.6, 95% CI 1.1-2.3). Compared with women without HRT use, the risk of SAH continued to be higher among women reporting active use of HRT (RR 1.5, 95% CI 1.0-2.2) after adjusting for age, systolic blood pressure, cigarette smoking, alcohol consumption, body mass index, race/ethnicity, diabetes, and cardiovascular disease. The risk of SAH was nonsignificantly h...