MedSchool: Ace Your OSCEsThe Medical Company
GET - On the App Store
Cranial Nerves

CN IV: Trochlear Nerve

February 15th, 2021


  • Role

  • Somatic motor - eye intorsion and depression (through contraction of the contralateral superior oblique).

Trochlear Nerve Palsy

  • Abnormalities

  • Eye deviation upward and rotation outward
  • Vertical diplopia
  • Inability to look down and in - difficulty descending stairs
  • Head tilting away from the side of the lesion
  • Causes of Trochlear Nerve Palsy

  • Congenital absence
  • Closed head injury

Motor Pathway

Cortical Centre
Primary motor cortex (frontal lobe)
Trochlear Nucleus
Tegmentum (midbrain)
Upper medulla
Superior orbital fissure
Superior oblique


The trochlear nerve is the longest intracranial nerve in the body and has the least axons, making it the most susceptible to stretch damage in the case of closed head trauma.
Next Page
Want more info like this?
  • Your electronic clinical medicine handbook
  • Guides to help pass your exams
  • Tools every medical student needs
  • Quick diagrams to have the answers, fast
  • Quizzes to test your knowledge
Sign Up Now

Snapshot: Initialising...