Rupture of a previously unruptured giant middle cerebral artery aneurysm after extracranial-intracranial bypass surgery.

The fatal rupture of a previously unruptured giant middle cerebral artery aneurysm occurred 13 days after an extracranial-intracranial bypass had been carried out, before definitive aneurysm surgery. Alterations in blood flow adjacent to the aneurysm after the bypass may have led to the fatal hemorrhage. After a preliminary extracranial-intracranial bypass procedure, there should be no undue delay in the direct attack on a giant aneurysm, regardless of its mode of presentation.