## **Core Concept**
The posterior columns of the spinal cord are responsible for transmitting sensations of **proprioception** (position and movement sense), **vibration**, and **fine touch**. Damage to these pathways can lead to loss of these sensations.

## **Why the Correct Answer is Right**
The correct answer, **B. Tabes dorsalis**, is a condition associated with tertiary syphilis that specifically affects the posterior columns of the spinal cord, leading to loss of proprioception, vibration, and fine touch sensations. This condition results in **ataxia** (loss of coordination) and **Romberg's sign** (loss of balance when standing with eyes closed). The posterior column involvement in tabes dorsalis explains the loss of posterior column sensations in the lower limbs.

## **Why Each Wrong Option is Incorrect**
* **Option A:** This option is blank and does not provide a condition; therefore, it cannot be considered a valid choice for causing loss of posterior column sensations.
* **Option C:** This option is also blank and does not offer a specific condition related to the loss of posterior column sensations.
* **Option D:** Similarly, this option is blank and lacks a condition that could lead to the specified sensory loss.

## **Clinical Pearl / High-Yield Fact**
A key clinical feature of tabes dorsalis is the presence of **Argyll Robertson pupils**, which are bilaterally small pupils that constrict when the patient focuses on a near object (accommodate) but do not react to light. This is a classic sign that can help in diagnosing tabes dorsalis.

## **Correct Answer: B. Tabes dorsalis**