<prompt> Ptosis is due to:3rd CN palsy4th CN palsy5th CN palsy6th CN palsy  <response>: Ans. a 3rd CN palsy oculomotorRef.:BDC 6th ed. Vol-III361-62 Ptosis is drooping of eyelid. Eyelid is comprised of 4 muscles:Muscles, their innervation and functionMuscleCN innervationFunction LPSIIIOpens the eyelid Mullers muscleT1 NOT a CN; sympathetic nerveOpens eyelid when LPS tired FrontalisVIICloses the eyelid Orbicularis oculiVIICloses the eyelid CN III palsy leads to drooping of eyelid Ptosis. CN VII palsy may also cause ptosis.Also KnowAll the extraocular muscles are supplied by CN III except lateral rectus and superior oblique. Lateral rectus supplied by- CN VI Superior oblique supplied by- CN IVRemember- LR6; So4 