Bleeding into the subarachnoid space due to trauma or ruptured aneurysm describes which condition?

• A. Cerebral contusion
• B. Subarachnoid hemorrhage
• C. Epidural hematoma
• D. Anterograde amnesia

Answer: (B)

Bleeding into the subarachnoid space is subarachnoid hemorrhage, which occurs when blood enters the CSF-filled space between the arachnoid and pia mater due to trauma or rupture of a cerebral aneurysm. The blood irritates the meninges and often presents with a sudden, severe “thunderclap” headache, neck stiffness, photophobia, nausea, or loss of consciousness. On imaging, blood will be seen in the subarachnoid spaces such as the basal cisterns and sulci. This differs from cerebral contusion, which is bruising within the brain tissue itself; an epidural hematoma, which is bleeding between the skull and dura with a typical lens-shaped hematoma and sometimes a lucid interval; and anterograde amnesia, which is a memory impairment rather than a bleeding disorder.