High success rate in the long term with sixth nerve palsy
Surgeons found that patients who had incomplete or unilaterial sixth nerve palsy also achieved a more successful outcome after surgery.
SEATTLE — Chronic sixth nerve palsy can be managed in most patients, although multiple surgeries and other interventions may be needed, according to a study presented here.
“We found that more than one surgical procedure and a prism are often necessary in the management of chronic sixth nerve palsy,” Jonathan M. Holmes, MD, said here at the American Association for Pediatric Ophthalmology and Strabismus meeting.
Sixth nerve palsy is a pathological condition that causes partial or total loss of function of the lateral rectus.
In his study, Dr. Holmes compared the short-term results of patients who underwent treatment for their sixth nerve palsy to the long-term results of the same group of patients.
“We found that long-term results showed a better outcome. In the long-term study, patients were allowed additional treatments and the aid of prisms. This was not allowed in the short-term study,” Dr. Holmes said.
Researchers found that success — no diplopia in primary position — was achieved in 36% more patients in the long-term study of surgical outcome than in the short-term study, which defined success as single vision after one procedure not allowing prism.
Patients and methods
The long-term results of the study were documented for up to 18 months. The short-term study had a follow-up period of 6 months. Children and adults, 31 in total, were monitored for their chronic sixth nerve palsy, which recurred for more than a 6-month period.
The majority of these patients, 75%, were affected unilaterally by sixth nerve palsy and 25% were affected bilaterally. Half of the patients had a complete lateral rectus weakness, while the other half had an incomplete weakness, or partial paresis of the lateral rectus.
“There were eight patients who underwent strabismus surgery and botulinum toxin A, and 23 patients who had strabismus surgery with no botulinum toxin,” Dr. Holmes said.
Botulinum toxin A is a drug that is injected into an eye muscle to produce temporary paralysis. It can be used as the sole treatment for sixth nerve palsy, or in addition to a surgical treatment. The operations performed in this study were either transpositions or recess-resect procedures.
Criteria for successful outcomes
“In the previous study, we reported that 39% of patients treated with strabismus surgery alone achieved success. We defined success as absence of diplopia in primary position at distance fixation with less than 10 prism diopters of tropia,” Dr. Holmes said.
In the long-term study, the success rate was still based on these qualifications. However, patients were allowed to have multiple interventions, he added.
“Additionally, for this long-term study we defined partial success as allowing a face turn and prism if deviation was less than 10 prism diopters,” he noted.
Better long-term results
“Only about 40% of our patients had follow-up visits just to 12 months,” Dr. Holmes said.
However, he noted, most of these patients who did not have complete follow-up were already defined as successes or partial successes in the previous study.
Regarding choice of surgical procedure, 86% of those with a complete palsy were managed with transpositions. In contrast, 88% of incomplete, or partial palsy patients were managed with recess-resect procedures. For this long-term study, 32% of patients required reoperations to achieve success.
“Allowing reoperations, prism or face turn increased the success rate in the long-term study,” Dr. Holmes said.
The overall surgical success rate reached 75% of patients, he said.
Fully successful eye alignment without prism or face turn was achieved by half of the patients who were managed with surgery and no botulinum toxin A, and by half of the patients who underwent surgery in addition to botulinum toxin A treatments.
“For the remainder of patients in both groups, 25% achieved partial success, according to our criteria, and the other 25% qualified as failure,” he explained.
Success for partial, unilateral patients
When analyzing patterns in the rate of success, Dr. Holmes and colleagues found there was a higher success rate in patients who had incomplete palsies and/or palsy affecting just one eye.
“It seems as though laterality and completeness helped predict success or failure,” Dr. Holmes said.
“These data are useful for us to tell patients what outcomes to expect after treatment for their sixth nerve palsy,” he added.
For Your Information:
- Jonathan M. Holmes, MD, can be reached at the Mayo Clinic, 200 First St. SW, Rochester, MN 55905; (507) 284-3760; fax: (507) 284-4612.