**Question:** All of the following are seen in the Horner's syndrome, Except

A. Ptosis (drooping of the eyelid)
B. Anhidrosis (inability to sweat)
C. Miosis (narrowing of the pupil)
D. Enophthalmos (eye sinking)

**Core Concept:**
Horner's syndrome is a clinical condition characterized by a decrease in pupil size (miosis), lack of sweating (anhidrosis), and drooping of the eyelid (ptosis). The syndrome is caused by a disruption in the sympathetic innervation to the affected eye, typically resulting from a lesion in the cervical spinal cord, brainstem, or sympathetic trunk.

**Why the Correct Answer is Right:**
Option D, Enophthalmos, is not a core feature of Horner's syndrome. Enophthalmos, which is characterized by sinking of the eye, is a consequence of orbital bone fractures or orbital tumors involving the zygomatic arch, thereby disrupting the normal anatomy and function of the eye. In contrast, Horner's syndrome primarily affects the oculomotor functions and autonomic responses, such as pupillary changes and sweating.

**Why Each Wrong Option is Incorrect:**
Option A, Ptosis (drooping of the eyelid), is a key feature of Horner's syndrome, indicating impaired sympathetic innervation to the eye.
Option B, Anhidrosis (inability to sweat), is another essential feature of Horner's syndrome, reflecting the loss of autonomic control over sweat glands.
Option C, Miosis (narrowing of the pupil), is a primary symptom of Horner's syndrome, resulting from the disruption of the sympathetic innervation to the pupil.

**Clinical Pearl:**
Horner's syndrome is a valuable clinical clue for the identification of a cervical spinal cord, brainstem, or sympathetic trunk lesion. It helps in differentiating the syndrome from other conditions with similar signs and symptoms, such as a decrease in pupil size and drooping eyelid. A thorough clinical examination, including the assessment of pupillary reactions and sweating, is essential for accurate diagnosis and management of patients presenting with these symptoms.