The "warning leak" in spontaneous subarachnoid haemorrhage.

A clear history of a warning leak was obtained in 28% of patients with ruptured intracranial aneurysms admitted to a Department of Neurosurgery. The ultimate outcome in these patients was worse than in other patients who were in good condition after initial haemorrhage. There are also cases in which symptoms suggesting a warning leak are found not to be due to haemorrhage, and CT scanning cannot be relied upon to determine accurately whether a warning leak has actually occurred in patients with suggestive symptoms. The frequency and significance of the warning leak should be recognized. Such recognition would improve the outcome after the rupture of an intracranial aneurysm.