November 2020 — Forensic & Neuropathology

The correct answer is natural.

This case demonstrates the classical pattern of subarachnoid hemorrhage seen with a saccular aneurysm rupture. When looking at the base of the brain picture, an aneurysm is visible around the anterior communicating artery.

Subarachnoid hemorrhages (SAH) may arise from many etiologies, both traumatic and natural, and are simultaneously the most common indicator of traumatic brain injury and the classic presentation of a number of natural neurological vascular diseases. Accurate forensic evaluation of these findings should include assessment of scene along with autopsy findings.

Non-traumatic subarachnoid hemorrhages are most commonly associated with ruptured saccular aneurysms, which account for 80% of cases. A differential diagnosis should include arteriovenous malformations, cavernous angiomas mycotic aneurysms, neoplasm, blood dyscrasias and central venous thrombosis. In aneurysm rupture cases, the subarachnoid hemorrhage is typically limited or most predominantly focused near the base of the brain, posterior fossa, and the circle of Willis.

Most saccular aneurysms occur near the anterior portion of the circle of Willis with 38% being located along the anterior communicating artery. Search for a ruptured aneurysm should be conducted while the brain is in the unfixed state as formalin fixation with lead to hardening of the subarachnoid hemorrhage making it challenging to evaluate the vessels wound the Circle of willis.

Usually, ruptured aneurysms will bleed directly into the subarachnoid space, but occasionally, as seen in this case, a jet of blood from the strong arterial bleed can dissect through the brain parenchyma and reach the ventricular system, leading to concurrent intraventricular hemorrhages (in 63% of cases). These cases will result in sudden death in up to 60% of the time, usually unwitnessed and during sleep.

Traumatic subarachnoid hemorrhages will generally also be present over the convexity of the brain, extending along the Sylvian Fissures, and are usually seen in addition to contusions and lacerations along the brain parenchyma. Another etiology to consider when ruling out traumatic causes of subarachnoid hemorrhages is vertebral artery dissections, which are seen with severe hyperextension injuries of the head and neck. Common mechanisms include blows to the head or severe twisting of the neck. On gross exam, these cases show subarachnoid hemorrhages more centralized around the posterior cranial fossa, with tears in the ventral aspect of the brainstem being common.

After review of autopsy and scene findings on this case, cause of death is most consistent with a non-traumatic subarachnoid hemorrhage due to ruptured saccular aneurysm, and manner of death is determined to be natural (due solely to disease and aging process).

There are no findings that indicate a manner of death consistent with accident (an injury or poisoning resulting in an unintentional fatal outcome), suicide (self-infected injury with intent of self-harm) or homicide (injury by volitional act of another person with intent to cause harm). Classification of manner of death as undetermined, should only be used when information pointing to one manner of death is no more compelling than one or more other competing manners of death, which is not the applicable in this case.

References
1. Dolinak D, Matshes E, Lew E. Forensic Pathology. Amsterdam: Elsevier/Academic Press; 2012.
2. Ross J, Sandberg G, Powell S. Forensic Evaluation of Subarachnoid Hemorrhage. Acad Forensic Pathol. 2012;2(1):30-35. doi:10.23907/2012.004.
3. Troncoso J, Rubio A, Fowler D. Essential Forensic Neuropathology. Philadelphia: Wolters Kluwer Health; 2015.
4. Black M, Graham D. Sudden unexplained death in adults caused by intracranial pathology. J Clin Pathol. 2002;55(1):44-50. doi:10.1136/jcp.55.1.44.