Question
Ptosis in Horner syndrome is due to paralysis of which muscle?
| A. |
Superior tarsal muscle |
| B. |
Orbitalis |
| C. |
Orbicularis oculi |
| D. |
Sphincter pupillae |
Show Answer
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Correct Answer � A Explanation |
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– Horner syndrome: ptosis, miosis & anhidrosis on affected side.
– Superior tarsal muscle: smooth muscle in upper eyelid, innervated by sympathetic nerves. Paralysis → mild ptosis.
– Orbitalis: smooth muscle with minimal role in humans.
– Orbicularis oculi: skeletal muscle for eyelid closure; innervated by facial nerve, unaffected in Horner syndrome.
– Sphincter pupillae: controls pupil constriction; parasympathetic innervation, unaffected in Horner syndrome.