Role of inferior rectus botulinum toxin injection in vertical strabismus resulting from orbital pathology.

INTRODUCTION

We describe the uses and efficacy of botulinum toxin injection to the inferior rectus muscle in vertical strabismus resulting from orbital pathology.

METHODS

A retrospective review of patients undergoing inferior rectus botulinum toxin injection between 1982 and 2006 for vertical strabismus due to orbital pathology.

RESULTS

There were 13 patients identified; 6 with idiopathic orbital inflammatory syndrome (IOIS) including myositis, 3 with previous orbital wall fractures, 1 post-optic nerve sheath Schwannoma resection, 1 with lymphoma, 1 with metastasis, and 1 post-superior ophthalmic vein hemorrhage. A beneficial effect with inferior rectus botulinum toxin was obtained in 9/13 (69%) patients (mean follow-up 14 months). Resolution or improvement occurred in 4/6 (67%) patients with IOIS. Resolution was also obtained in the patient with previous optic nerve sheath Schwannoma resection, and the patient who sustained the superior ophthalmic vein hemorrhage. Improvement was noted in both the patient with lymphoma and in the patient with a metastasis. However, in patients with orbital wall fractures, only 1 of 3 patients obtained improvement. Benefit appeared independent of the size of vertical deviation, with 4/6 (67%) showing improvement with a pre-toxin angle 4-12 PD, and 5/7 (71%) improving with a pre-toxin angle 16-25 PD. Eleven patients received only 1 injection, one patient received 2, and another had an ongoing course of 8 injections.

DISCUSSION: Vertical strabismus secondary to a range of orbital conditions, particularly inflammatory, often can be successfully managed by inferior rectus botulinum toxin injections.