## **Core Concept**
Poliomyelitis, also known as polio, is a highly infectious disease caused by the poliovirus. The virus primarily affects the **motor neurons** of the spinal cord, leading to muscle weakness and paralysis. The specific part of the spinal cord involved in poliomyelitis is crucial for understanding the clinical manifestations of the disease.

## **Why the Correct Answer is Right**
The correct answer, **Anterior horn**, is right because poliomyelitis specifically targets the **anterior horn cells** of the spinal cord. The anterior horn of the spinal cord contains the **cell bodies of motor neurons** that transmit signals to skeletal muscles, controlling voluntary movements. The poliovirus invades these motor neurons, leading to their destruction, which results in muscle weakness or paralysis.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Posterior horn - This part of the spinal cord is involved in sensory processing and is not primarily affected by poliomyelitis.
- **Option B:** Lateral horn - This region is involved in the autonomic nervous system and is not the primary site of poliovirus infection.
- **Option D:** Posterior column - This area is responsible for transmitting sensory information, including vibration and proprioception, and is not directly affected by poliomyelitis.

## **Clinical Pearl / High-Yield Fact**
A key clinical correlation to remember is that poliomyelitis leads to **flaccid paralysis** due to the destruction of motor neurons in the anterior horn of the spinal cord. This is in contrast to **spastic paralysis**, which results from lesions in the central nervous system affecting the pyramidal tracts.

## **Correct Answer:** . Anterior horn.