## Core Concept
The third cranial nerve, also known as the oculomotor nerve, controls several eye muscles, including the medial rectus, superior rectus, inferior rectus, and inferior oblique, as well as the levator palpebrae superioris muscle, which is involved in eyelid elevation. A nuclear injury to this nerve affects its nucleus in the midbrain, leading to specific patterns of weakness due to the involvement of the nerve fibers and the surrounding structures.

## Why the Correct Answer is Right
In a unilateral 3rd cranial nerve nuclear injury, the affected muscles are typically the ipsilateral medial rectus, superior rectus, inferior rectus, and inferior oblique, along with the levator palpebrae superioris. However, because the nerve fibers for the superior rectus muscle cross over at the level of the nucleus, a unilateral nuclear lesion can cause weakness of the contralateral superior rectus muscle in addition to the ipsilateral muscles. This results in a characteristic pattern of ophthalmoplegia (weakness of eye movements) and ptosis (drooping eyelid). The correct answer likely relates to a feature that does not fit this pattern.

## Why Each Wrong Option is Incorrect
Without the specific options provided, we can still discuss general incorrect features:
- **Option A:** If it describes a feature consistent with the expected pattern of weakness and ptosis from a unilateral 3rd nerve nuclear lesion, it would be incorrect to say it's not a feature.
- **Option B:** Similarly, if it aligns with known effects such as ipsilateral ptosis, inability to move the eye medially, upwards, or downwards, it would be a feature and thus incorrect to exclude.
- **Option C:** If this option also describes a recognized consequence of such an injury, it would not be the correct answer to the question.
- **Option D:** This would be the correct choice if it describes a feature not typically associated with a unilateral 3rd cranial nerve nuclear injury.

## Clinical Pearl / High-Yield Fact
A key point to remember is that in a unilateral 3rd nerve nuclear lesion, the **superior rectus muscle weakness is bilateral**, but more pronounced on the contralateral side due to the decussation of the nerve fibers controlling this muscle. This pattern helps differentiate nuclear from peripheral 3rd nerve lesions.

## Correct Answer: D.