Forensic Evaluation of Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) may occur with natural, accidental, homicidal, suicidal, and/or undetermined events. The forensic autopsy and death scene investigation are useful in reconstructing the mechanism of death, as well as the dynamics of the event. Therefore, an accurate forensic evaluation of SAH is crucial. The annual incidence of subarachnoid hemorrhage in the United States is estimated at 1 per 10,000 persons with a median age of 50 years, and a high mortality rate. SAH is the most common indicator of traumatic brain injury (TBI). The majority (80%) of nontraumatic SAH is due to a ruptured saccular aneurysm. Other causes of nontraumatic SAH include arteriovenous malformations, cavernous angiomas, mycotic aneurysms, neoplasms, blood dyscrasias, perimesencephalic hemorrhage and central venous thrombosis. Risk factors for nontraumatic SAH include cigarette smoking, hypertension, cocaine use, heavy alcohol use, and a first-degree relative with subarachnoid hemorrhage. The rate and amount of hemorrhage determine the morbidity and mortality of the lesion. Computed tomography (CT) is considered the study of choice for ante-mortem identification of SAH. In rare circumstances, however, a similar CT appearance may occur in the absence of blood in the subarachnoid space. Such “pseudo-subarachnoid hemorrhage” is confirmed when autopsy shows no subarachnoid hemorrhage in those carrying the premortem CT diagnosis. However, when true SAH is present, dating of the hemorrhage, by both gross and microscopic examination, may aid in the forensic evaluation.