Immediate features of paralysis

The acute features of oculomotor nerve palsy may include:

• divergent strabismus:
  • the paralysed eye is rotated outwards and downwards when the normal eye fixates - due to intact actions of lateral rectus and superior oblique muscles
  • concurrent trochlear nerve palsy is indicated by absence of intorsion on attempted down-gaze
    
    
• only lateral movement is possible
  
  
• pupil may be fixed and dilated, and accommodation lost:
  • however the pupil is spared in 75% of cases due to diabetes since the inner pupillary fibres are more affected than the outer ones
    
    
• ptosis of the upper eyelid - may cover the pupil due to loss of action of levator palpebrae superioris
  
  
• ipsilateral oculomotor nerve palsy may feature as part of Benedikt or Weber syndromes
  
  
• there may be a mild proptosis arising from loss of tone of three of the four recti muscles

Reference

1. Libreros-Jiménez HM, Manzo J, Rojas-Durán F, et al. On the cranial nerves. NeuroSci. 2024 Mar;5(1):8-38.