Initial treatment outcomes in chronic sixth nerve palsy

We conducted a prospective multi-center, nonrandomized, data-collection study of patients with chronic sixth cranial nerve palsy. We evaluated success rates with conservative nonsurgical management, botulinum toxin (botox) treatment, strabismus surgery, and a combination of botox treatment and surgery.

All members of the American Association for Pediatric Ophthalmology and Strabismus and the North American Neuro-Ophthalmology Society were invited to enroll patients with sixth nerve palsy or paresis of more than 6 months duration over a 2-year period (between March 1998 and February 2000). The botox and surgical groups received intervention within 3 months of enrollment. Success at 6 months from enrollment was defined as absence of diplopia in primary position and no more than 10 prism diopters (pd) distance esotropia in primary position. Patients with no follow-up were excluded.

Fifty-six eligible patients were enrolled by 33 investigators. Eighteen (32%) were traumatic in etiology, 15 (27%) were unknown (including presumed hypertensive), 14 (25%) were neoplastic, 2 (4%) were diabetic, and 7 (13%) were other. Twenty (35%) were managed conservatively without surgery, 10 (18%) with botox treatment, 19 (33%) with surgery, and 8 (14%) with a combination of botox treatment and surgery. Success at 6 months from enrollment was 15% in the conservatively managed cases, 10% with botox alone, 39% with surgery alone, and 25% with a combination of botox and surgery.

This study demonstrates that management of chronic sixth nerve palsy and paresis remains challenging. Spontaneous recovery occurs but is uncommon. Botox treatment alone was rarely successful, and a single surgical procedure had a lower-than-expected success rate. Care should be taken in directly comparing success rates between treatment groups because of bias in patient selection.