What are the features of 3rd nerve palsy?

 What are the features of 3rd nerve palsy???

  

  Let see,

      First of all keep in mind that 3rd nerve or oculomotor nerve has #motor part which supplies the most of the extraocular muscles except lateral rectus and superior oblique.So if 3rd nerve lesion occur then all of the muscles of eyeball except these two will be paralysed.So action of these two muscles will be intact.

Now as lateral rectus causes #Abduction of eyeball and Superior oblique causes #Depression or #downward_movement  of eyeball,so eye will remain #Abducted_downward in other words #Outward & #downward (For details of movement of eyeball and actions of extraocular muscle please see the video:https://youtu.be/1ublA29kZdg)

Now,3rd nerve also supplies #levator_palpebre_superioris muscle which is the main elevator of upper eyelid,as the lesion of 3rd nerve causes paralysis of this muscle so upper eyelid will be remain dropped which we call #Ptosis.

Another thing is that oculomotor nerve also contains parasympathetic fibres around it's periphery.And these fibres supply the circular muscle of Iris and contraction of this causes constriction of the pupil.And around this circular mucle there is radial muscles which are supplied by #Sympathetic nerve and contraction of these causes dilation of pupil.

Now as 3rd nerve palsy,so the parasympathetic supply to the circular muscle of pupil will be impaired,but nerve supply to the radial muscle is intact.So Radial muscle will take upper hand and there will be #dilatation of pupil.

Another thing is, oculomotor nerve also gives nerve supply to cilliary muscles of eyeball which play role in accommodation for near vision.So #Accommodation of near vision will also be impaired.

And finally as the most of muscles of eyeball is paralysed so for binocular vision the axis will be not the same so there will #Diplopia