## **Core Concept**
A subdural hematoma is a type of intracranial hemorrhage that occurs in the space between the brain and the dura mater, typically resulting from the tearing of bridging veins. This condition is often associated with head trauma. Understanding the pathophysiology and common causes of subdural hematomas is crucial for managing patients with head injuries.

## **Why the Correct Answer is Right**
The correct answer, **C. Trauma**, is the most common cause of subdural hematoma. This is because subdural hematomas often result from the shearing forces that occur during head trauma, leading to the rupture of bridging veins. These hematomas can be acute or chronic, with the acute form being more immediately life-threatening. The mechanism involves the tearing of small veins that bridge the cerebral cortex to the dura mater, leading to bleeding into the subdural space.

## **Why Each Wrong Option is Incorrect**
- **Option A:** While certain **infections** can lead to intracranial hemorrhages, they are not the most common cause of subdural hematomas. Infections might cause bleeding through mechanisms like vasculitis or septic thrombosis, but this is less common compared to traumatic causes.
- **Option B:** **Hypertension** is a significant risk factor for intracerebral hemorrhages and some types of intracranial bleeding, but it is not the most direct or common cause of subdural hematomas. Hypertension can contribute to the formation of cerebral microaneurysms and increase the risk of bleeding, but the primary cause of subdural hematomas is trauma.
- **Option D:** **Arteriovenous malformations (AVMs)** can cause intracranial hemorrhages due to the rupture of abnormal blood vessels. However, AVMs are a less common cause of subdural hematomas compared to traumatic injuries.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that **chronic subdural hematomas** often present in the elderly population after a minor head trauma, sometimes without a clear history of significant injury. This condition can mimic dementia or other neurological disorders, making it a critical diagnosis to consider in the differential diagnosis of altered mental status in elderly patients.

## **Correct Answer:** **C. Trauma**