## **Core Concept**
Lateral medullary syndrome, also known as Wallenberg's syndrome, is a neurological condition caused by a lesion in the lateral part of the medulla oblongata. This region is supplied by the vertebral and posterior inferior cerebellar arteries. The syndrome results from damage to the lateral medulla and affects various cranial nerves and tracts.

## **Why the Correct Answer is Right**
The correct answer involves understanding the structures affected in lateral medullary syndrome. The syndrome characteristically presents with:
- **Ipsilateral Horner's syndrome** due to disruption of the descending sympathetic fibers.
- **Dysphagia and hoarseness** due to involvement of the 9th and 10th cranial nerves.
- **Ataxia** and **numbness** on the ipsilateral side of the face due to involvement of the spinal trigeminal tract and nucleus.
- **Contralateral loss of pain and temperature sensation** in the body due to the spinothalamic tract involvement.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Ipsilateral numbness of arm, trunk - Incorrect because the numbness in lateral medullary syndrome typically affects the face (due to involvement of the spinal trigeminal nucleus and tract) and contralateral body (spinothalamic tract).
- **Option B:** Ipsilateral 12th nerve palsy - Incorrect because the 12th cranial nerve (hypoglossal nerve) is not typically involved in lateral medullary syndrome; it's more commonly associated with medial medullary syndrome.
- **Option D:** Contralateral pyramidal tract sign - Incorrect in the context of lateral medullary syndrome. The pyramidal tracts are generally affected in medial medullary syndrome, leading to contralateral hemiparesis.

## **Clinical Pearl / High-Yield Fact**
A classic clinical pearl for lateral medullary syndrome (Wallenberg's syndrome) is the combination of **ipsilateral** symptoms (e.g., Horner's syndrome, ataxia, and facial numbness) and **contralateral** symptoms (e.g., loss of pain and temperature sensation in the body). This crossed pattern is a hallmark of lateral medullary lesions.

## **Correct Answer:** C.