Twenty percent of strokes are hemorrhagic, with subarachnoid hemorrhage (SAH) and intracerebral hemorrhage each accounting for 10 percent. Most SAHs are caused by ruptured saccular aneurysms. This is often a devastating clinical event with mortality rates that approach 50 percent, as well as substantial neurologic morbidity in survivors.
Mortality rates due to SAH appear to be decreasing over time in Western populations [1-4]. Improvements in rates of smoking, treatment of hypertension, and management of SAH are plausible but unproven reasons for the reduction in mortality. Improved diagnostic accuracy over time, including exclusion of SAH mimics, as well as therapeutic advances may also be playing a role
The epidemiology, etiology, clinical manifestations, and diagnosis of aneurysmal SAH are reviewed here. The treatment of this disorder and the epidemiology and pathogenesis of intracranial aneurysms and management of unruptured aneurysms are discussed separately. Mycotic aneurysms and nonaneurysmal subarachnoid hemorrhage are also discussed separately. (See "Aneurysmal subarachnoid hemorrhage: Epidemiology, risk factors, and pathogenesis" and "Treatment of aneurysmal subarachnoid hemorrhage" and "Unruptured intracranial aneurysms" and "Overview of infected (mycotic) arterial aneurysm" and "Nonaneurysmal subarachnoid hemorrhage" and "Perimesencephalic nonaneurysmal subarachnoid hemorrhage".)
The primary symptom of aneurysmal SAH is a sudden, severe headache (97 percent of cases) classically described as the "worst headache of my life" . The headache is lateralized in 30 percent of patients, predominantly to the side of the aneurysm. Consistent with the rapid spread of blood, the symptoms of SAH typically begin abruptly.
The onset of the headache may or may not be associated with a brief loss of consciousness, nausea or vomiting, and meningismus . In one series, these occurred in 53, 77, and 35 percent of patients respectively . Meningismus and often lower back pain may not develop until several hours after the bleed since it is caused by the breakdown of blood products within the CSF, which lead to an aseptic meningitis . While many patients have an altered level of consciousness, coma is unusual. Seizures occur during the first 24 hours in less than 10 percent of patients, but are a predictor of poor outcome . SAH may also present as sudden death; at least 10 to 15 percent of patients die before reaching the hospital.