## **Core Concept**
The "delta sign" is a radiological finding seen on computed tomography (CT) scans of the head. It refers to a triangular or delta-shaped appearance that is typically associated with a specific type of intracranial hemorrhage or calcification. This sign is particularly relevant in the context of diagnosing and managing patients with head injuries or cerebral pathology.

## **Why the Correct Answer is Right**
The delta sign on CT head is characteristically seen in **epidural hematoma**. This appearance is due to the collection of blood between the dura mater and the skull, which can form a biconvex or lens-shaped hematoma. When the hematoma is large enough and the blood starts to clot, it can retract and form a central area of low density (due to the serum separating from the clot) surrounded by a higher density periphery, resembling a delta or triangle. The mechanism involves the rupture of a meningeal artery, often due to a temporal bone fracture.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Subdural hematoma typically presents as a crescent-shaped collection of blood beneath the dura mater and does not usually form a delta sign.
- **Option B:** Subarachnoid hemorrhage involves bleeding into the space surrounding the brain (the subarachnoid space) and does not characteristically produce a delta sign on CT.
- **Option C:** Intracerebral hemorrhage refers to bleeding within the brain parenchyma itself and, while it can have various appearances on CT, the delta sign is not typically associated with this condition.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that the delta sign is highly suggestive of an **epidural hematoma**, which is a medical emergency requiring prompt neurosurgical intervention. Early recognition of this sign on CT scans can significantly impact patient outcomes by facilitating timely surgical decompression.

## **Correct Answer:** D. Epidural hematoma