**Core Concept**
The "panda sign" is a radiological finding that refers to the bilateral hyperdensity of the substantia nigra on non-contrast computed tomography (CT) scans of the brain, resembling the markings on a panda's face. This sign is often associated with the presence of hemorrhage in the brain, particularly in the context of intracerebral hemorrhage.

**Why the Correct Answer is Right**
The panda sign is a result of the high density of blood products within the substantia nigra, which appears as a hyperdensity on non-contrast CT scans. This is due to the presence of red blood cells and hemoglobin breakdown products, such as hemosiderin and ferritin, which accumulate in the brain tissue and cause the characteristic appearance. The substantia nigra is a region of the midbrain that is particularly susceptible to hemorrhage due to its rich blood supply and delicate vascular structure.

**Why Each Wrong Option is Incorrect**
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**Clinical Pearl / High-Yield Fact**
The panda sign is a valuable radiological clue that can help differentiate intracerebral hemorrhage from other causes of stroke, such as ischemic infarction. However, it is essential to note that the panda sign can also be seen in other conditions, such as vasculitis, trauma, and malignancy, so a thorough clinical evaluation and imaging workup are necessary to establish a definitive diagnosis.

**Correct Answer:**
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