CT findings that indicate mass effect in traumatic brain injury include which of the following?

• A. Epidural hematoma with focal mass effect
• B. Small contusion without edema
• C. Linear skull fracture without edema
• D. Isolated subarachnoid hemorrhage without edema

Answer: (A)

Mass effect happens when a space-occupying lesion or swelling pushes brain tissue, causing displacement such as a midline shift or compression of the ventricles. On CT, an epidural hematoma is a classic cause of mass effect because it rapidly accumulates between the skull and dura, expanding enough to push adjacent brain structures. The typical CT appearance is a lens-shaped (biconvex) hyperdense collection that often accompanies a skull fracture and is associated with shifts of the midline structures and compression of the basilar cisterns or ventricles. That displacement is the hallmark of mass effect.

The other findings described do not show this displacement. A small contusion without edema lacks the swelling and wide area of compression needed to push brain tissue aside. A linear skull fracture without edema is just a fracture line, with no space-occupying lesion. An isolated subarachnoid hemorrhage without edema involves blood in the spaces around the brain but not a lesion large enough to distort or push brain structures.