Question:easy
Muscle responsible for ptosis in Horner syndrome:- 
Muscle responsible for ptosis in Horner syndrome:-
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Horner = sympathetic loss; the only sympathetically-supplied lid elevator is Müller's (superior tarsal) muscle, giving partial ptosis.
Updated On: Jun 22, 2026
- Orbicularis oculi
- Levator palpebrae
- Horner muscle
- Mullers muscle
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The Correct Option is D
Solution and Explanation
Trace the innervation, then the muscle follows. Horner syndrome is fundamentally a sympathetic denervation of the eye. So the muscle responsible for any feature of Horner syndrome must be a sympathetically-supplied muscle.
Apply this to the eyelid. The lid is held up by two elevators:
• The big skeletal elevator, Levator Palpebrae Superioris, runs on the oculomotor nerve (CN III) - not sympathetic, so it is spared in Horner syndrome.
• The small smooth-muscle elevator, the superior tarsal muscle = Müller's muscle, runs on sympathetic fibres.
When sympathetic input is cut, only Müller's muscle weakens. Because it contributes just a few millimetres of lift, its loss gives the characteristic mild/partial ptosis of Horner syndrome (in contrast to the severe, complete ptosis of a CN III palsy that takes out the levator).
The remaining options fail on function or nerve supply: orbicularis oculi closes the lid (facial nerve); the so-called Horner muscle is the tear-pump part of orbicularis, unrelated to elevation. Therefore the muscle producing the ptosis is Müller's muscle (Option D).
Apply this to the eyelid. The lid is held up by two elevators:
• The big skeletal elevator, Levator Palpebrae Superioris, runs on the oculomotor nerve (CN III) - not sympathetic, so it is spared in Horner syndrome.
• The small smooth-muscle elevator, the superior tarsal muscle = Müller's muscle, runs on sympathetic fibres.
When sympathetic input is cut, only Müller's muscle weakens. Because it contributes just a few millimetres of lift, its loss gives the characteristic mild/partial ptosis of Horner syndrome (in contrast to the severe, complete ptosis of a CN III palsy that takes out the levator).
The remaining options fail on function or nerve supply: orbicularis oculi closes the lid (facial nerve); the so-called Horner muscle is the tear-pump part of orbicularis, unrelated to elevation. Therefore the muscle producing the ptosis is Müller's muscle (Option D).
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