midbrain signs

Last reviewed 07/2021

Ocular abnormalities are a prominent feature of space- occupying lesions in the midbrain. Presentation includes:

  • lesions of the upper midbrain - weakness of conjugate deviation upwards and ptosis
  • lesions of the lower midbrain - weakness of conjugate deviation downwards - often accompanied by ptosis and weakness of convergence
  • pupils unequal and dilated
  • reactions to light and to convergence-accommodation may be both lost, or just the former may be absent
  • nuclear ophthalmoplegia may be asymmetrical
  • headache, papilloedema, vomiting from hydrocephalus
  • nystagmus and ataxia may result from injury to cerebellar pathways
  • compression of lateral lemniscus may cause unilateral or bilateral deafness
  • tremors, tonic convulsions, loss of consciousness may occur