Botulinum toxin treatment of the sixth nerve palsy: an experience of 5-year duration in Thailand.

Forty-five patients (48 eyes) with sixth nerve palsy were treated with botulinum toxin injection to antagonist medial rectus muscle at Siriraj Hospital from October 1995 to September 2000. The common causes of palsy were ischemia, trauma and inflammation. Thirty-eight patients (group I) had an interval to treatment of less than 24 weeks (average, 8.7 weeks) and seven patients (group II), longer than 24 weeks. The mean pre-injection esodeviation and extent of abduction in group I were 28.1 prism diopters (PD) and 28.4 per cent, and in group II were 38 PD and 8.1 per cent respectively. After a mean follow-up of 12.2 months, twenty-seven (71.1%) patients in group I recovered completely after the first injection and three (7.9%), after the second injection with a mean interval to recovery of 8.1 weeks. One (14.3%) of 7 patients of group II obtained complete recovery without fusion. Twenty-six (83.9%) of 31 patients with complete resolution achieved binocular function. We conclude that botulinum toxin treatment is a safe and effective alternative to traditional surgery of acute onset sixth nerve palsy.