Enophthalmos is an uncommon feature of Horner’s syndrome. Enophthalmos is due to palsy of?
**Core Concept**
Enophthalmos is a posterior displacement of the globe of the eye within the orbit, giving the appearance of a sunken eye. This condition is often associated with Horner's syndrome, a disorder of the autonomic nervous system that affects the eye and face. The pathophysiology of enophthalmos involves the loss of sympathetic tone to the orbit, leading to relaxation of the orbital smooth muscles.
**Why the Correct Answer is Right**
The correct answer is related to the sympathetic nervous system, which plays a crucial role in maintaining the tone of the orbital smooth muscles. Specifically, the sympathetic nerves that innervate the superior tarsal muscle (also known as Müller's muscle) and the levator palpebrae superioris muscle are involved in enophthalmos. The palsy of these sympathetic nerves leads to a decrease in the tone of these muscles, resulting in enophthalmos. The sympathetic nerves are part of the superior cervical ganglion, which is the primary source of sympathetic innervation to the head and neck.
**Why Each Wrong Option is Incorrect**
* **Option A:** The oculomotor nerve (cranial nerve III) is responsible for controlling the movement of the eye, but it is not directly involved in the pathophysiology of enophthalmos.
* **Option B:** The trigeminal nerve (cranial nerve V) has a role in facial sensation and motor function, but it is not directly related to enophthalmos.
* **Option D:** The facial nerve (cranial nerve VII) controls the muscles of facial expression, but it is not involved in the pathophysiology of enophthalmos.
**Clinical Pearl / High-Yield Fact**
Remember that enophthalmos is a subtle sign of Horner's syndrome, and it may be difficult to detect clinically. The presence of ptosis (drooping of the eyelid) and miosis (constricted pupil) are more common and characteristic features of Horner's syndrome.
**Correct Answer: C. The superior cervical ganglion is responsible for the sympathetic innervation to the head and neck, including the orbital smooth muscles.