Fourth nerve palsy

(Redirected from Trochlear nerve palsy)


Right eye
Eye movements by extra-ocular muscles and cranial nerve innervation
  • Also called CN IV or trochlear nerve palsy
  • Trochlea innervates superior oblique muscle
    • Intorts, depresses and abducts the globe
  • Trochlear nerve palsy causes an inability to move the eye in inward rotation, downward, and laterally. [1]
  • Most common cause of vertical diplopia [2]


Clinical Features

  • Vertical, torsional, or oblique diplopia.
    • Worse on downward gaze and gaze away from affected muscle [2]
  • Head-tilt
    • Tilt typically away from affected side (~70%) to overcome inward rotation of affected eye to create wider separation of images. Can be paradoxical, where patient tilts head toward affected side (~3%) [1] [4]
    • Bielschowsky phenomenon - head tilt to affected side reveals inability to intort, diplopia
Trochlear nerve palsy.jpg

Differential Diagnosis


Labs and Tests


  • Head CT if traumatic, suspect stroke, or subarachnoid hemorrhage (rare).
  • MRI is study of choice, although there no increased yield from MRI vs CT scan. [2] [4]


  • Address underlying acute pathology
  • May require surgical correction
  • +/- Neurology consult


  • Vasculopathic: Observation for improvement over 6-8 weeks. Often resolve spontaneously in 4-6 months.
  • Traumatic: Observation for improvement over 6-8 weeks. Often resolves spontaneously. If progressing or lack of improvement – neuroimaging with MRI
  • Isolated, idiopathic cases very rarely have an underlying etiology after prolonged follow-up, and most resolve spontaneously in weeks to months. If no improvement in 2 months, consider neuroimaging. [4]

See Also

External Links


  1. 1.0 1.1 Marx JA, Hockberger RS, Walls RM, et al., eds. Rosen's Emergency Medicine: Concepts and Clinical Practice. Philadelphia, PA: Mosby/Elsevier; 2013
  2. 2.0 2.1 2.2 2.3 Sheik Z. Trochlear Nerve Palsy Treatment and Management on Accessed on 8/29/2015
  3. Disorders of Ocular Movement and Pupillary Function In: Adams and Victor's Principles of Neurology. 10th ed. Accessed on on 8/29/2015. Chapter 14
  4. 4.0 4.1 4.2 4.3 4.4 Brazis, PW. Isolated palsies of cranial nerves III, IV, and VI. Seminars in neurology. 2009 Feb. 29(1):14