Question

What is the classic triad of Horner Syndrome?

• A. \(Ptosis + Miosis + Anhidrosis\)
• B. \(Ptosis + Mydriasis + Hyperhidrosis\)
• C. \(Proptosis + Miosis + Anhidrosis\)
• D. \(Ptosis + Diplopia + Mydriasis\)

Hint:

Use the mnemonic "MAP" to remember the triad: Miosis, Anhidrosis, and Ptosis. The symptoms occur on the same side (ipsilateral) as the nerve damage.

Answer 1

The Correct Option is A

Concept:

• Horner syndrome, also known as oculosympathetic paresis, is a clinical condition resulting from a lesion or interruption of the sympathetic nerve supply to the eye and face.

• The sympathetic pathway is a three-neuron chain: first-order (central), second-order (preganglionic), and third-order (postganglionic) neurons.
Step 1: Understanding the sympathetic innervation loss
The sympathetic nervous system is responsible for maintaining pupil dilation, elevating the eyelid (via Müller’s muscle), and regulating sweat production on the face.
When this pathway is interrupted, the characteristic triad of symptoms appears.

Step 2: Identifying Ptosis
Ptosis refers to the drooping of the upper eyelid.
In Horner syndrome, this is caused by paralysis of the superior tarsal muscle (Müller’s muscle), which is smooth muscle innervated by the sympathetic system.
The ptosis is typically mild (1–2 mm).

Step 3: Identifying Miosis
Miosis is the constriction of the pupil.
It occurs because the dilator pupillae muscle (which normally dilates the pupil via sympathetic stimulation) is paralyzed.
This leaves the sphincter pupillae muscle (innervated by the parasympathetic system) unopposed, leading to a smaller pupil on the affected side.

Step 4: Identifying Anhidrosis
Anhidrosis is the absence or decrease of sweating on the affected side of the face.
The sweat glands receive sympathetic innervation.
Note that the presence or location of anhidrosis can often help localize whether the lesion is preganglionic or postganglionic.