Which potential space lies between the dura mater and the arachnoid mater and is seen when filled with blood, usually from trauma?

• A. Subarachnoid space
• B. Subdural space
• C. Epidural space
• D. Arachnoid mater

Answer: (B)

The space described is the subdural space. It lies between the dura mater and the arachnoid mater and is a potential space that can become real when trauma causes blood to collect there, producing a subdural hematoma. This bleeding typically involves tearing of bridging veins that run from the brain surface to the dural sinuses, allowing blood to accumulate in that space.

This differs from the subarachnoid space, which sits between the arachnoid and the pia and is normally filled with cerebrospinal fluid; the epidural space is between the skull and the dura; and the arachnoid mater is the membrane itself, not a space.