An 8-year-old male is admitted to the hospital with a drooping right eyelid (ptosis). The initial diagnosis is Horner’s syndrome. Which of the following additional signs on the right side would confirm the diagnosis?
**Core Concept**
Horner's syndrome is a neurological disorder characterized by the disruption of the sympathetic nervous system pathways that control the eye, leading to ptosis (drooping eyelid), miosis (pupil constriction), and anhidrosis (lack of sweating). The diagnosis is confirmed by identifying additional signs of sympathetic nervous system dysfunction.
**Why the Correct Answer is Right**
The correct answer is enophthalmos, which is the posterior displacement of the globe of the eye within the orbit. This occurs due to the loss of sympathetic tone to the orbit, leading to a decrease in the volume of the orbital contents. Enophthalmos is a characteristic feature of Horner's syndrome and is often associated with ptosis and miosis. The sympathetic nervous system normally maintains the forward position of the globe by contracting the superior and inferior rectus muscles. In Horner's syndrome, the absence of sympathetic tone leads to a decrease in muscle contraction, resulting in enophthalmos.
**Why Each Wrong Option is Incorrect**
* **Option A:** Ipsilateral lacrimation is not a characteristic feature of Horner's syndrome. In fact, patients with Horner's syndrome often experience decreased tearing (hypolarcrimation) due to the loss of sympathetic tone to the lacrimal gland.
* **Option B:** Elevation of the right eyebrow ( brow elevation) is not a typical feature of Horner's syndrome. Horner's syndrome is associated with ptosis and miosis, but not with brow elevation.
* **Option C:** Enlargement of the pupil (mydriasis) is not a feature of Horner's syndrome. In fact, Horner's syndrome is characterized by miosis, which is the constriction of the pupil.
**Clinical Pearl / High-Yield Fact**
Enophthalmos is a key feature of Horner's syndrome and can be used to confirm the diagnosis. Remember that Horner's syndrome is a complex disorder that affects multiple systems, including the sympathetic nervous system, and its diagnosis requires a thorough understanding of the underlying anatomy and physiology.
**Correct Answer:** C. Enophthalmos.