We searched the Cochrane Library, MEDLINE, and Embase and used a library of downloaded citations on subarachnoid haemorrhage that was updated every few months and spanned all time on MEDLINE. We used the search term “subarachnoid hemorrhage”. Publications in the past 5 years were preferentially selected, but older highly cited papers or classically important publications were also included. The reference lists of articles from the last 5 years that were identified by this search strategy were
SeminarSpontaneous subarachnoid haemorrhage
Introduction
This Seminar reviews spontaneous subarachnoid haemorrhage, which accounts for 5% of strokes (range 1–6).1 Despite subarachnoid haemorrhage being less common than ischaemic stroke and intracerebral haemorrhage, the young age of those affected and the high morbidity and mortality makes its effect on years of life lost similar to that of the more common types of stroke.2 Diagnosis and management involves emergency and general physicians, specialists in neurology, neurocritical care, interventional neuroradiology, and neurosurgery, and thus requires multidisciplinary collaboration to achieve the best patient outcome.
Section snippets
Epidemiology
The incidence of subarachnoid haemorrhage in population-based studies, including out-of-hospital deaths, is 9·1 cases per 100 000 people per year (95% CI 8·8–9·5), with some regional variation.3 Finland (19·7 cases per 100 000 people per year, 18·1–21·3) and Japan (22·7 cases per 100 000 people per year, 21·9–23·5) have the highest reported incidences. Controversy exists as to whether these variations in incidence are real or are due to differences in case ascertainment.3 The incidence of
Risk factors
The occurrence of subarachnoid haemorrhage peaks between age 50 and 60 years.3 The condition is 1·6 times more common in women than in men, but this difference becomes evident only after the fifth decade.3 Oestrogen and, less commonly, progesterone, have been postulated to have protective effects and thus to contribute to the increased incidence in postmenopausal women.4 However, a meta-analysis4 showed that these hormones might affect the risk of subarachnoid haemorrhage but the data were
Family history and genetics
Family history of subarachnoid haemorrhage, defined as two first-degree relatives with the condition, accounts for 11% of events whereas ADPKD accounts for 0·3% of cases.19 Screening of 548 relatives who were smokers or who had hypertension in families with two affected siblings or three or more affected first-degree or second-degree relatives showed that 21% had unruptured aneurysms.12 The aneurysms of two patients subsequently ruptured, resulting in a familial risk of 1·2% per year (95% CI
Pathophysiology
Saccular cerebral aneurysms are acquired lesions that develop at branch points of major arteries of the circle of Willis. They develop in response to haemodynamic stress-induced degeneration of the internal elastic lamina with secondary thinning and loss of the tunica media. Multiple pathophysiological mechanisms have been proposed (appendix). The average size of a ruptured aneurysm is 6–7 mm.23
Aneurysmal subarachnoid haemorrhage injects blood into the subarachnoid space in almost all cases (
Diagnosis
Sudden onset of the “most severe headache of a person's life” is the cardinal symptom of subarachnoid haemorrhage.28 About 70% of patients present with headache, which is of sudden onset (thunderclap headache, defined as reaching maximum severity within 1 min of onset) in 50% of these patients. Sudden onset is a more important feature for diagnosis than severity.29 Headache is the only symptom in about half of cases; in the remainder there is nausea, vomiting, transient or ongoing loss of
Management
Once initial emergency support has been administered and diagnosis made, treatable causes of ongoing primary brain injury need to be addressed. The first procedure is surgical evacuation of space-occupying acute subdural and intracerebral haemorrhages, which is best accompanied by clipping the ruptured aneurysm (figure 4).51, 52, 53 Second, insertion of a ventricular catheter can be life saving in patients with acute hydrocephalus.
The main causes of early death include brain damage from the
Prognosis
Regarding short-term outcome, a meta-analysis103 of 33 studies found a case fatality of 8·3–66·7% in patients with subarachnoid haemorrhage. The median of patients who died before arrival to hospital was 8·3%. In another meta-analysis,104 there was an absolute annual reduction rate in 30 day mortality of 0·9% (95% CI 0·3–1·5) between 1980 and 2005, for an overall 50% reduction. Data for functional outcome in population-based studies are scarce. It is estimated that 55% of patients regain
Prevention
Subarachnoid haemorrhage could be prevented by repairing aneurysms before they rupture or by reducing aneurysm formation. Unruptured aneurysms had a prevalence of 3·2% in 83 study populations.11 No randomised trials exist on which to base the decision to repair an unruptured aneurysm, and the risks of rupture have to be weighed against the risks of repair.11 Several systems have been developed to aid the clinician in decision making. A systematic review8 pooled analysis of 8382 patients who had
Search strategy
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