How is surgery performed for the treatment 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

Patients with congenital superior oblique palsy often have abnormally lax superior oblique tendon. Exaggerated, forced duction test described by Guyton can be performed intraoperatively to determine if there is any degree of tendon laxity relative to normal eye, as follows: [37]

  • This test is performed by grasping the eye obliquely at 2- and 8-o'clock positions for the left eye and at 4- and 10-o'clock positions for the right eye.

  • Eye is rotated superiorly and medially while simultaneously depressing the eye into the orbit. This places superior oblique tendon on maximal tension.

  • Eye is rolled back and forth over the tendon to ascertain its tension.

  • Performing this test prior to the start of case will guide the surgeon to determine eyes that will benefit from a superior oblique tendon tuck.

  • Of equal importance is that it will identify those patients who are at risk for developing a postoperative Brown syndrome.

  • Tendon tucks should be performed only for markedly lax tendons. Tuck should be enough to match tension of the normal eye's tendon.

Any surgeon who performs oblique muscle surgery should be familiar with anatomy, landmarks, and appropriate approaches to these muscles.

Visualization is more difficult than with rectus muscle surgery, and injury to adjacent nerves, blood vessels, and other extraocular muscles may occur. Use of headlight can improve visualization.


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