A 45 year male with a history of alcohol dependence presents with confusion, nystagmus and ataxia. Examination reveals 6th cranial nerve weakness. He is most likely to be suffering from :

**Core Concept**
The patient's symptoms suggest a condition related to **thiamine deficiency**, which is commonly seen in individuals with a history of **alcohol dependence**. Thiamine plays a crucial role in **glucose metabolism** and **neurotransmission**.

**Why the Correct Answer is Right**
The correct answer is related to **Wernicke's encephalopathy**, a condition characterized by **confusion**, **nystagmus**, and **ataxia**, which is caused by **thiamine deficiency**. The **6th cranial nerve weakness** is also a common finding in this condition.

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because it does not match the symptoms described.
**Option B:** Incorrect because it is not directly related to thiamine deficiency.
**Option C:** Incorrect as it is not the best match for the patient's presentation.
**Option D:** Incorrect because it is not the most likely diagnosis given the symptoms.

**Clinical Pearl / High-Yield Fact**
Wernicke's encephalopathy is a **medical emergency** that requires immediate **thiamine supplementation** to prevent further brain damage.

**Correct Answer:** D. Wernicke's encephalopathy.

✓ Correct Answer: B. Wernicke encephalopathy