Question

After a right limb amputation, the patient is experiencing severe phantom limb pain. What is the mechanism behind this?

• A. Projection of adjacent fibers to overlap to right sensory cortex
• B. Projection of adjacent fibers to overlap to left sensory cortex
• C. Expansion of right sensory cortex
• D. Expansion of left sensory cortex

Hint:

Phantom limb pain is often a result of cortical reorganization, where sensory input from nearby areas overlaps with the region of the brain corresponding to the missing limb.

Answer 1

The Correct Option is B

Phantom limb pain refers to the sensation of pain in a limb that has been amputated. The underlying mechanism of this phenomenon is rooted in the reorganization of neural pathways within the brain.

When a limb is removed, the sensory input that the brain normally receives from that limb ceases. This creates a void in the sensory cortex areas that were previously associated with the missing limb. The brain compensates for this lack of input through neuronal plasticity. Specifically, adjacent sensory neurons from other body parts can extend and reorganize to take over the sensory functions of the de-afferented cortex area. This process is known as sensory cortical reorganization.

The sensory cortex is contralateral, meaning the left sensory cortex processes sensations from the right side of the body and vice versa. In this scenario, after the right limb is amputated, fibers adjacent to the sensory areas of the cortex, which previously processed input from the right limb, can extend to overlap with the left sensory cortex. This reorganization can create sensations that are interpreted as originating from the amputated limb.

Therefore, the experience of phantom limb pain after a right limb amputation is primarily due to the projection of adjacent fibers to overlap to the left sensory cortex.