During surgery for meningioma, the left paracentral lobule was injured. It would lead to paresis of:
## Core Concept
The paracentral lobule is a region in the brain located near the central sulcus and is crucial for motor and sensory functions, particularly of the lower limbs. It is supplied by the anterior cerebral artery and its branches. The paracentral lobule includes parts of the primary motor cortex and primary somatosensory cortex.
## Why the Correct Answer is Right
The paracentral lobule, especially when referring to the left side, is involved in controlling the right lower limb. This area is responsible for the motor functions of the leg and foot. Injury to this region during surgery for a meningioma would likely result in weakness or paresis of the right lower limb.
## Why Each Wrong Option is Incorrect
- **Option A:** This option is incorrect because the injury described would not primarily affect the left upper limb. The motor and sensory areas for the upper limb are generally located more laterally in the brain, in regions such as the precentral and postcentral gyri, which are not specified here.
- **Option B:** This option suggests bilateral lower limb involvement, which is not typical for a unilateral lesion in the paracentral lobule. A unilateral lesion would affect the contralateral side of the body, in this case, the right lower limb.
- **Option D:** This option implies involvement of the right upper limb, which is not consistent with the function of the paracentral lobule. The paracentral lobule's role is more closely associated with lower limb function.
## Clinical Pearl / High-Yield Fact
A key point to remember is that the motor and sensory homunculi are organized in a specific way: the lower limbs are represented near the midline (medially) in the brain, particularly in areas like the paracentral lobule, while the upper limbs are represented more laterally. Therefore, a lesion in the paracentral lobule can lead to contralateral lower limb weakness.
## Correct Answer: C.