What is the prevalence of trochlear nerve palsy (fourth nerve palsy)?

Updated: Oct 08, 2019
  • Author: Zafar A Sheik, MD, MD; Chief Editor: Andrew G Lee, MD  more...
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Answer

Most cases of isolated fourth nerve palsy are believed to be congenital. [4] However, estimating the true frequency of congenital fourth nerve palsy is difficult. Many patients compensate with use of head-tilt or large fusional amplitudes; therefore, it may not present to an ophthalmologist until adulthood, when their fusional control begins to deteriorate.

Some of the best information regarding the incidence of acquired fourth nerve palsy can be found in the Mayo Clinic series. Several studies, performed over the last 4 decades, reported the incidence and etiology of acquired cranial nerve palsies in adult and pediatric patients. Trochlear nerve palsy was less common than abducens or oculomotor palsies. Of 4,373 acquired cases of extraocular muscle palsy in adults, there were only 657 cases of isolated fourth nerve disease. [5] Fourth nerve palsy was also the least frequent in pediatric population. In a similar Mayo Clinic study of 160 children, 19 of them had isolated fourth nerve palsy. [6, 7]


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