## **Core Concept**
Diffuse axonal injury (DAI) is a type of traumatic brain injury characterized by widespread damage to the brain's white matter, resulting from the shearing forces exerted on the brain during a head injury. This injury pattern typically involves the **axons** of neurons.

## **Why the Correct Answer is Right**
The correct answer involves the typical locations where lesions are found in DAI. These areas include the **subcortical white matter**, **corpus callosum** (especially the **splenium**), and **brainstem**. The corpus callosum, particularly its posterior part (splenium), and the brainstem are commonly affected due to their anatomical vulnerability to shearing forces during acceleration-deceleration injuries.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option might list areas not typically associated with DAI, such as the cerebral cortex or basal ganglia, which are more commonly involved in focal injuries rather than diffuse axonal injuries.
- **Option B:** This could include areas like the cerebral cortex or meninges, which are not the primary sites of injury in DAI.
- **Option D:** This might list structures like the ventricular system or the dura mater, which are not directly involved in the pathophysiology of DAI.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that DAI often results from high-speed motor vehicle accidents or falls, and patients may have a **normal or near-normal** Glasgow Coma Scale (GCS) score immediately after injury, only to deteriorate later. Early diagnosis with MRI, particularly diffusion-weighted imaging (DWI), is crucial for detecting the extent of axonal injury.

## **Correct Answer:** . Corpus callosum, subcortical white matter, and brainstem.