In which type of injury would you expect to see a crescent-shaped fluid collection on a CT scan?

• A. Aneurysmal subarachnoid hemorrhage
• B. Subdural hematoma
• C. Intracerebral hemorrhage
• D. Extradural hematoma

Answer: (B)

In cases of a subdural hematoma, a crescent-shaped fluid collection is expected to appear on a CT scan. This is due to the location and nature of the injury: a subdural hematoma occurs when there is tearing of the bridging veins beneath the dura mater, often resulting from trauma. The blood collects between the dura and the brain, leading to a crescentic shape that conforms to the surface of the brain, distinguishing it from other types of hematomas.

The crescent shape arises because the hematoma spreads more diffusely along the inner surface of the skull, rather than forming a more localized, rounded mass like other types of hematomas. This distinct morphology is a key characteristic seen in imaging, particularly on CT scans, making it a critical diagnostic feature for clinicians assessing traumatic brain injury.