Nontraumatic Subarachnoid Hemorrhage: Clinical Outcome

Nontraumatic subarachnoid hemorrhage (SAH) represents 3%–6% of all cases of cerebrovascular disease, which translates to an annual incidence of 8–10 cases/100,000 population. The most common cause is a rupture of a cerebral aneurysm, which occurs with a frequency of approximately 90%. However, in some cases, the exact cause cannot be determined. Although many theories have been formulated, uncertainty currently exists regarding the exact mechanism by which a cerebral aneurysm forms or ruptures. It is highly probable that the problem is multifactorial, with involvement of structural elements of the arteries, angiogenic factors, and vasoactive substances. Some theories have been postulated to explain the cause of bleeding in cases of spontaneous SAH without aneurysm. Arterial hypertension is one of the most accepted theories; another is the presence of a small thrombosed aneurysm, which is impossible to visualize in initial imaging studies.