When patient is asked to look down, his upper eyelid fails to follow the rotation of the eyeball and thus lags behind, this eye sign is known as:
**Core Concept**
The question is testing the understanding of a specific clinical sign related to the movement of the upper eyelid and its coordination with the rotation of the eyeball. This sign is associated with the innervation of the muscles involved in eyelid movement and eye rotation.
**Why the Correct Answer is Right**
The correct answer is related to the Marcus Gunn jaw-winking phenomenon, which is a condition where the eyelid is abnormally innervated by the trigeminal nerve, causing it to wink or move upward when the patient moves their jaw. However, in the context of the question, the correct answer is actually the Marcus Gunn phenomenon, which is a different condition where the eyelid fails to follow the rotation of the eyeball due to aberrant regeneration of the oculomotor nerve. This results in the eyelid lagging behind when the patient looks down.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not describe the specific clinical sign related to the movement of the upper eyelid and eye rotation.
* **Option B:** This option is incorrect because it does not accurately describe the phenomenon of the eyelid lagging behind when the patient looks down.
* **Option D:** This option is incorrect because it is unrelated to the clinical sign described in the question.
**Clinical Pearl / High-Yield Fact**
The Marcus Gunn phenomenon is an important clinical sign that can be associated with third cranial nerve (oculomotor nerve) palsy or other conditions affecting the innervation of the eyelid muscles.
**Correct Answer:** C.