**Core Concept**
Subdural hemorrhage is a type of intracranial hemorrhage characterized by bleeding into the space between the dura mater and the arachnoid mater, which surrounds the brain. The most common cause of subdural hemorrhage is trauma, and the affected vessel is usually a branch of the middle meningeal artery, but this is not the most common vessel affected.

**Why the Correct Answer is Right**
The most common vessel affected in subdural hemorrhage is actually a branch of the middle cerebral artery, specifically the lenticulostriate arteries or the anterior cerebral artery's pericallosal artery's branches. These arteries are prone to injury due to their location and the forces exerted during head trauma. The bleeding from these vessels can lead to the accumulation of blood in the subdural space, causing increased intracranial pressure and potentially life-threatening complications.

**Why Each Wrong Option is Incorrect**
* **Option A:** The middle meningeal artery is more commonly associated with epidural hemorrhage.
* **Option B:** The anterior cerebral artery's pericallosal artery is indeed involved, but it's not the most common vessel affected.
* **Option D:** The posterior cerebral artery is not typically involved in subdural hemorrhage.

**Clinical Pearl / High-Yield Fact**
In subdural hemorrhage, the patient's level of consciousness and pupillary response can be used to estimate the severity of the hemorrhage. A patient with a large subdural hemorrhage may present with decreased level of consciousness, pupillary dilation, and possibly even herniation.

**Correct Answer: C.**