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Excluding head trauma, the most common cause of subarachnoid hemorrhage (SAH) is rupture of an intracranial (saccular) aneurysm; other etiologies include bleeding from a vascular malformation (arteriovenous malformation or dural arterial-venous fistula), infective (mycotic) aneurysms, and extension into the subarachnoid space from a primary intracerebral hemorrhage. Approximately 2% of the population harbor aneurysms, and 25,000–30,000 cases of aneurysmal rupture producing SAH occur each year in the United States; rupture risk for aneurysms <10 mm in size is 0.1% per year; for unruptured aneurysms, the surgical morbidity risk far exceeds the percentage.


Sudden, severe headache, often with transient loss of consciousness at onset; vomiting is common. Bleeding may injure adjacent brain tissue and produce focal neurologic deficits. A progressive third nerve palsy, usually involving the pupil, along with headache suggests posterior communicating artery aneurysm. In addition to dramatic presentations, aneurysms can undergo small ruptures with leaks of blood into the subarachnoid space (sentinel bleeds). The initial clinical manifestations of SAH can be graded using established scales (Table 19-1); prognosis for good outcome falls as the grade increases.



  • Noncontrast CT is the initial study of choice and usually demonstrates the hemorrhage if obtained within 72 h. LP is required for diagnosis of suspected SAH if the CT is nondiagnostic; xanthochromia of the spinal fluid is seen within 6–12 h after rupture and lasts for 1–4 weeks.

  • Cerebral angiography is necessary to localize and define the anatomic details of the aneurysm and to determine if other unruptured aneurysms exist; angiography should be performed as soon as possible after the diagnosis of SAH is made.

  • ECG may reveal ST-segment and T-wave changes similar to those associated with cardiac ischemia; caused by circulating catecholamines and excessive discharge of sympathetic neurons. A reversible cardiomyopathy producing shock or congestive heart failure may result.

  • Studies of coagulation and platelet count should be obtained, and rapid correction should ensue if SAH is documented.


  • Early aneurysm repair prevents rerupture.

  • The International Subarachnoid Aneurysm Trial (ISAT) demonstrated improved outcomes with endovascular therapy compared to surgery; however, some aneurysms have a morphology not amenable to endovascular treatment, and therefore surgery is still ...

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