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In the Danish Aneurysm Study 1,076 patients were admitted with an aneurysmal subarachnoid haemorrhage in the 5-year period 1978-83. Pre-existing arterial hypertension, defined by the necessity for antihypertensive treatment at the time of admission was identified in 155 patients (15%). Nine hundred and two (85%) were normotensive. Nineteen patients were excluded because of inadequate information. Comparisons between the hypertensive and normotensive groups of patients showed no significant differences in sex-distribution, onset and course of the initial insult, results of primary CT-scan, location, size and numbers of aneurysms, number of rebleedings, and also in neurological symptoms, mental status, accommodation and occupation at a 2-year follow-up examination. The hypertensive group differed significantly in the following variables from the normotensive group. The median age was 8 years older (55 and 47 years of age respectively); a fewer number of patients fell into Hunt grade I-II on admission (34% and 43% respectively); an increased frequency of extracranial (23% and 13% respectively) and intracranial (35% and 18%, respectively) atherosclerosis was seen on angiography; a fewer number of patients underwent operation (48% and 66%, respectively); and at the 2-year follow-up examination an increased rate of overall mortality was evident (59% and 42%, respectively). There was an increased rate of mortality in patients in Hunt grade I-II on admission (52% and 22%, respectively) and an increased rate of mortality in patients who rebled (100% and 75%, respectively). Pre-existing arterial hypertension is an unfavourable prognostic factor after an aneurysmal subarachnoid haemorrhage.

During a 5-year period (1978-1983) the clinical features and operative morbidity/mortality were registered prospectively for all patients in Denmark with an unruptured symptomatic (27 patients) or incidental (21 patients) intracranial saccular aneurysm. A follow-up examination was performed 2 years after diagnosis of the aneurysm. Thirty symptomatic aneurysms in 27 patients most frequently involved the visual pathways or ocular motility (66%). The median diagnostic delay for patients with impaired visual acuity was 7 months but only 14 days for patients with impaired ocular motility. The localisation of the 30 symptomatic and 23 incidental aneurysms were: internal carotid artery (73%±35%), anterior communicating artery (3%±26%) and middle cerebral artery (7%±35%). The diameters of 73% of the symptomatic aneurysms were greater than 10 mm, while the diameter of 74% of the incidental aneurysms were below 10 mm. The total operative morbidity and mortality were 15% and 4%, respectively. The mortality rate in the follow-up period was 10-11% mainly due to fatal bleeding from unoccluded aneurysms. In 21 survivors, a normal mental status was found in 43% and mild dementia was found in another 43%. The impaired visual acuity was unchanged in 67% of patients, while the ocular motility had normalised in 75%. A normal daily functional capacity was enjoyed by 57% while 43% had a moderate reduction, mostly due to visual disturbances.

In a well-defined area, The Kingdom of Denmark, 1076 patients with ruptured intracranial aneurysms were admitted to the six Danish neurosurgical departments in a prospective consecutive study in the 5-year period 1978-1983. Follow-up examinations were accomplished 3 months and 2 years after the admission. A total of 674 women and 402 men with a median age of 49 years were included in the study. The localisation of the ruptured aneurysms were: internal carotid artery 285, anterior communicating artery and horizontal part of anterior cerebral artery 383, middle cerebral artery 291, basilar and vertebral arteries 83 and peripheral or other localisation 34. A significantly better outcome was seen in cases with internal carotid aneurysms compared to other localisations. 670 patients underwent operation. A highly significantly better outcome was found in operated versus non-operated patients in comparable clinical conditions. The advantage of microneurosurgery was well documented. Patients with vasospasm had a significantly worse outcome. Within the first 2 weeks a daily rebleeding rate from 0.2% to 2.1% was observed, and patients who rebled had a significantly worse outcome compared to patients, who did not rebleed. The overall outcome at 2-year follow-up was: normal 27.5%, mild dementia 15.8%, severe dementia 9.9%, vegetative 1.3% and mortality 45.5%.

In a prospective consecutive non-randomised study including 1076 patients with ruptured intracranial aneurysms 205 patients received epsilon aminocraproic acid (EACA) and 871 did not. No significant differences between the two groups concerning clinical condition on admission, sex, age, localisation and size of the aneurysms were seen. No cases of rebleeding (RB) were observed within the first 4 days in the EACA treated patients, but within the first 48 hours, which is the optimal period recommended for operation of patients in good clinical condition, this difference of the rates of RB between EACA treated and not treated patients is not significant. A significantly lower rate of RB was observed in the EACA group within the first 2 weeks, but no significant differences in morbidity and mortality were found at the 2-year follow-up examination.

1,076 patients with ruptured aneurysms admitted to neurosurgical units in Denmark over a period of 5 years were followed up for 2 years. The outcome as regards survival and normality of mental state was assessed in relation to age, clinical grade, and whether or not surgery was performed. For all ages and grades operated patients did better than those not operated on. Age seemed to have no bearing on outcome except for operated on good condition patients (grades 1-3) under the age of 40 years, who were significantly more likely to have a normal mental outcome than other groups.

A theoretical evaluation of the lifetime probabilities of different outcomes in patients with unruptured intracranial aneurysms (UA) has been made using a life table method. The calculations were performed for aneurysm presenting ages from 20 to 70 years of age for men and women assuming an annual risk of aneurysm rupture of 1 %, 2% and 3% and a rate of mortality after rupture of 50%. At 10, 20, 30, 40, 50 and 60 years after the diagnosis of an UA the probability of survival without bleeing is reduced below the expected probability of survival according to the life tables by the following percentages (assuming an annual risk of bleeding of 2%): 19%, 34%, 46%, 56%, 64% and 72%, respectively. A survey of the lifetime probabilities of four different outcomes for patients with an UA indicates a substantial reduction in life expectancy after the diagnosis of an UA. In most ages the surgical risks are more than balanced by the risks associated with an untreated unruptured aneurysm

From autopsy and neuroradiological studies a maximum prevalence of unruptured intracranial aneurysms (UA) of 0.5% in the general population is revealed. Studies concerning the incidence of aneurysmal subarachnoid haemorrhage (SAH) revealed 10 cases per 100,000 inhabitants per year. From these epidemiological parameters a minimum annual risk of 2% of rupture of an UA is calculated. It is in accordance with clinical studies, which also demonstrated an annual risk of UA rupture of at least 2%. No critical size of the UA predisposing to rupture has been found. Operation on diagnosed UA is recommended because of the serious prognosis after aneurysmal SAH (morbidity 20%-25% and mortality 50%-60%) and because the morbidity (4%) and the mortality (0%) after operative treatment of UA are very low.