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 arteriovenous fistula) 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 rate 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 18-1); prognosis for good outcome falls as the grade increases.
TABLE 18-1GRADING SCALES FOR SUBARACHNOID HEMORRHAGE |Favorite Table|Download (.pdf) TABLE 18-1GRADING SCALES FOR SUBARACHNOID HEMORRHAGE
|Grade ||Hunt-Hess Scale ||WFNS Scale |
|1 ||Mild headache, normal mental status, no cranial nerve or motor findings ||GCSa score 15, no motor deficits |
|2 ||Severe headache, normal mental status, may have cranial nerve deficit ||GCS score 13–14, no motor deficits |
|3 ||Somnolent, confused, may have cranial nerve or mild motor deficit ||GCS score 13–14, with motor deficits |
|4 ||Stupor, moderate to severe motor deficit, may have intermittent reflex posturing ||GCS score 7–12, with or without motor deficits |
|5 ||Coma, reflex posturing or flaccid ||GCS score 3–6, with or without motor deficits |
Noncontrast CT is initial study of choice and usually demonstrates hemorrhage if obtained within 72 h. LP is required for diagnosis of suspected SAH if 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 diagnosis of SAH.
ECG may reveal ST-segment and T-wave changes similar to 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, with rapid correction indicated if SAH is documented.
TREATMENT: SUBARACHNOID HEMORRHAGE ANEURYSM REPAIR
Early aneurysm repair prevents rerupture.
The International Subarachnoid Aneurysm Trial (ISAT) demonstrated improved outcomes with endovascular therapy compared to surgery; however, some aneurysms have morphology not amenable to ...