Understanding skew deviation and a new clinical test to differentiate it from trochlear nerve palsy

J AAPOS. 2010 Feb;14(1):61-7. doi: 10.1016/j.jaapos.2009.11.019.


Skew deviation is a vertical strabismus caused by a supranuclear lesion in the posterior fossa. Because skew deviation may clinically mimic trochlear nerve palsy, it is sometimes difficult to differentiate the 2 conditions. In this review we compare the clinical presentations of skew deviation and trochlear nerve palsy and examine the pathophysiology that underlies skew deviation. We then describe a novel clinical test-the upright-supine test-to differentiate skew deviation from trochlear nerve palsy: a vertical deviation that decreases by > or =50% from the upright to supine position suggests skew deviation and warrants investigation for a lesion in the posterior fossa as the cause of vertical diplopia.

Publication types

  • Research Support, Non-U.S. Gov't
  • Review

MeSH terms

  • Child
  • Diagnosis, Differential
  • Diagnostic Techniques, Ophthalmological*
  • Humans
  • Strabismus / diagnosis*
  • Strabismus / etiology
  • Strabismus / physiopathology*
  • Trochlear Nerve Diseases / complications
  • Trochlear Nerve Diseases / diagnosis*
  • Trochlear Nerve Diseases / physiopathology*