Question

The characteristic feature of Horner's syndrome is

• A. Dilated pupil
• B. Ptosis
• C. Increased sweating
• D. Abducted eye

Hint:

Horner's syndrome is a loss of sympathetic tone, so its features are the opposite of pupil dilation and increased sweating.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
We need to identify the classic feature of Horner's syndrome, which results from disruption of the sympathetic nerve supply to the eye and face.

Step 2: Key Formula or Approach:
Horner's syndrome results from loss of sympathetic tone, so its features are the opposite of what sympathetic stimulation would normally produce, all appearing on the same side as the lesion.

Step 3: Detailed Explanation:
Sympathetic fibers normally keep the pupil dilated and the eyelid raised, so loss of sympathetic tone in Horner's syndrome causes a small, constricted pupil (miosis), not a dilated one, ruling out that option.
Ptosis, a partial drooping of the upper eyelid, occurs because the sympathetically innervated Muller's muscle, which normally provides a small amount of extra eyelid elevation, loses its tone, causing this classic mild ptosis.
Sweating over the face is driven by sympathetic fibers as well, so Horner's syndrome causes decreased sweating (anhidrosis) on the affected side, not increased sweating.
Horner's syndrome does not cause any abnormal deviation of the eye itself, such as an abducted position, since the muscles controlling eye position are not affected by loss of sympathetic tone.

Step 4: Final Answer:
So the characteristic feature of Horner's syndrome is ptosis, alongside miosis and anhidrosis, all on the affected side.