Subarachnoid hemorrhage is defined as bleeding into which space?

• A. The subarachnoid space
• B. The subdural space
• C. Between the skull and dura mater
• D. Within the brain tissue

Answer: (A)

Subarachnoid hemorrhage means bleeding into the subarachnoid space—the gap between the arachnoid mater and the pia mater that normally contains cerebrospinal fluid and the cerebral vessels. This is different from the subdural space (between dura and arachnoid), the epidural space (between skull and dura), or bleeding contained within brain tissue (intraparenchymal hemorrhage). So the defining location is the subarachnoid space.