Vertical rectus muscle transposition and botulinum toxin for complete sixth nerve palsy

Background: Effective surgical treatment of complete unrecovered sixth nerv e palsy must include the transfer of abducting power to the temporal aspect of the globe with release of medial rectus contracture nasally, We describ e our experience in the treatment of five such patients who underwent full vertical rectus transposition combined with botulinum toxin chemodenervatio n of the ipsilateral medial rectus muscle. Methods: The five patients all had primarily unilateral complete unrecovere d sixth nerve palsy. They all underwent a complete preoperative and postope rative eye examination and an orthoptic assessment. Excursion into abductio n was graded from -8 (globe immobilized in extreme adduction) to -4 (abduct ion as far as primary position) to 0 (full abduction). Abduction saccades a nd a forced muscle generation test confirmed the presence of complete unrec overed sixth nerve palsy, and forced duction testing measured the degree of medial rectus contracture. All patients received ipsilateral medial rectus injection of botulinum toxin in the preoperative (8 to 2 months before sur gery) and perioperative periods, and underwent complete superior rectus-inf erior rectus transposition temporally. Results: The average length of follow-up was 21 (range 6 to 48) months, The average preoperative distance alignment was 52 (range 25 to 80) prism diop tres (PD). Vertical rectus transposition combined with botulinum toxin inje ction resulted in an average distance alignment change of 66 PD (range 50 P D to 82 PD) of exoshift. The average final deviation was 1 PD of esotropia (range 4 PD of esotropia to 6 PD of exotropia). Average abduction improved from -6 (range -3 to -8) preoperatively to -1.7 (range -1 to -2) postoperat ively, Saccades averaged -4 preoperatively and improved to -2 postoperative ly, Normal vertical eye movements were preserved in all patients. A total f ield of single binocular vision was created in all patients, which averaged 55 degrees (range 30 degrees to 75 degrees) in the horizontal meridian. Th e field of single binocular vision from primary position into abduction ave raged 23 degrees (range 18 degrees to 28 degrees). Interpretation: Temporal transposition of the vertical rectus muscles combi ned with perioperative botulinum toxin injection of the ipsilateral medial rectus muscle is a reliable and effective way of restoring functional binoc ular vision in patients with complete unrecovered sixth nerve palsy.