**Brown-Séquard Syndrome Explanation**

1. **Core Concept:** Brown-Séquard Syndrome is a neurological condition characterized by deficits along the lateral funiculus of the spinal cord following injury or disease. It is named after Chevalier Jackson and Édouard Brown-Séquard, who independently described the syndrome.

2. **Why the Correct Answer is Right:** Brown-Séquard Syndrome results from the partial or complete section of the spinal cord, specifically affecting the lateral funiculus. The lateral funiculus contains the spinothalamic tract, which is responsible for transmitting sensory information from the dermatomes on one side of the body. Therefore, the syndrome is characterized by the absence of pain and temperature sensation on one side of the body, while sparing proprioception and vibration.

3. **Why Each Wrong Option is Incorrect:**
A. **Option A (Proprioception)** - Proprioception is the ability to sense one's body position and movements. It is mediated by the posterior funiculus, which is not affected in Brown-Séquard Syndrome.
B. **Option B (Vibration)** - Vibration sense is also preserved in Brown-Séquard Syndrome, as it is conveyed by the spinothalamic tract in the lateral funiculus, which is deficient in the syndrome.
C. **Option C (Spinal cord)** - The syndrome is caused by a spinal cord injury affecting the lateral funiculus, not the entire spinal cord.
D. **Option D (Both sides)** - Brown-Séquard Syndrome affects only one side of the body, not both.

4. **Clinical Pearl (High-Yield Fact):** In Brown-Séquard Syndrome, the sensory deficits are usually not symmetrical. This is due to the asymmetrical distribution of sensory fibers in the lateral funiculus. For example, pain and temperature sensation fibers are concentrated in the dorsal column, while proprioception and vibration fibers are more densely packed in the ventral column.

5. **Correct Answer:** **Option D (One side)** - Brown-Séquard Syndrome results from a spinal cord injury affecting the lateral funiculus on one side, leading to deficits in pain and temperature sensation on that side.

6. **Core Concept (Anatomical Structure):** The lateral funiculus carries sensory fibers for pain and temperature sensation, while the ventral and dorsal funiculi carry proprioception and fine touch fibers, respectively. In Brown-Séquard Syndrome, the injury involves the lateral funiculus, which leads to the loss of pain and temperature sensation on one side of the body.

7. **Core Concept (Physiology):** Spinal cord injuries affecting the lateral funiculus can result in a sensory deficit along with motor deficits, as the lateral funiculus is also responsible for motor function in the contralateral limb.