Paralytic strabismus: the role of botulinum toxin

The Use of Botulinum Toxin in Strabismus Treatment

There is a long and extensive experience with the use of Botulinum Toxin type A (BoNT-A) injection in the treatment of different types of strabismus and oculomotor palsies. The frequency of its use varies depending on the country and institution. It is a short procedure, may reduce general anesthesia exposure, causes minimal scarring compared to surgery, and can be proposed as an early treatment in unstable strabismus. Over many years, the experience of using BoNT-A indications has been refined and new applications have been reported. The use of BoNT-A in the postoperative period, after strabismus surgery or during surgery, can also be beneficial.

Botulinum toxin as an initial therapy for management of sixth nerve palsies caused by nasopharyngeal carcinomas

PurposeThe purpose of this study is to evaluate the efficacy and safety of botulinum toxin injection as a primary treatment for strabismus in a cohort of patients with nasopharyngeal carcinoma (NPC)-related chronic sixth nerve palsy.Patients and methodsWe retrospectively reviewed all cases of NPC-related sixth nerve palsy receiving botulinum toxin injection in the Hong Kong Eye Hospital between January 2009 and January 2016. Only cases with diplopia for at least 6 months; and failed a trial of Fresnel prism therapy were recruited. We excluded cases with prior strabismus surgery and multiple cranial nerve palsies. Patients were offered botulinum toxin injection as primary treatment for their strabismus and were given further injections or offered surgery if diplopia persisted. Success with botulinum toxin was defined as a final distant orthophoria of <15 PD in primary gaze, no diplopia in primary position, and no head turn, as measured 6 months after the last injection, without requiring a second treatment.ResultsA total of 25 patients were included in the study. All patients received concurrent chemo-radiotherapy for NPC. There was a statistically significant reduction in the mean deviation at distant after the last injection compared to that at presentation (P<0.001, Wilcoxin signed rank test). Overall, 7 patients (28%) achieved clinical success and 15 patients (64%) remained diplopia-free by repeated botulinum toxin injections alone. Nine patients went on to receive definitive surgery and all achieved good ocular alignment after surgery. Transient ptosis or vertical deviation was seen in 7 patients, which resolved within 3 months and no serious complications arose from the treatment in our series.ConclusionsBotulinum toxin injection is a relatively less-invasive alternative to surgery that can be done under a topical anesthesia setting, which improves patient's quality of life via reduction in diplopia. It is a recommendable initial option in patients with chronic nerve palsies who may have higher risks associated with strabismus surgery.

Botulinum toxin for treatment of restrictive strabismus

PURPOSE

To study the types of acquired restrictive strabismus treated in a tertiary hospital and the outcome of treatment with botulinum toxin.

METHODS

We performed a 10-year retrospective study of patients with restrictive strabismus aged ≥18 years who were treated with botulinum toxin. Treatment was considered successful if the final vertical deviation was ≤5 PD, horizontal deviation ≤10 PD, with no head turn or diplopia.

RESULTS

We included 27 cases (mean age, 61.9 years). Horizontal strabismus was diagnosed in 11.1%, vertical in 51.9%, and mixed in 37%. Strabismus was secondary to cataract surgery in 6 cases, high myopia in 6, orbital fractures in 5, retinal surgery in 5, Graves ophthalmopathy in 4, and repair of conjunctival injury in 1 case. Diplopia was diagnosed in all patients, head turn in 33.3%. The initial deviation was 14 PD (range, 2-40), the mean number of injections per patient was 1.6 (range, 1-3), and the mean dose was 9.5 IU (range, 2.5-22.5). At the end of follow-up, diplopia was recorded in 59.3%, head turn in 18.5%, surgical treatment in 51.9%, and need for prism glasses in 14.8%. Outcome was successful in 37% of patients (4 high myopia, 3 orbital fractures, 2 post-surgical retinal detachment, and 1 post-cataract surgery). Mean follow-up was 3±1.8 years.

CONCLUSION

Vertical deviation was observed in half of the sample. The most frequent deviation was secondary to cataract surgery and high myopia. Treatment with botulinum toxin was successful in one-third of the patients at the end of follow-up.

Predictive factors underlying the restoration of macular binocular vision in adults with acquired strabismus

PURPOSE

To investigate whether macular binocular vision can be permanently lost following acquired strabismus and to identify predictive factors underlying its restoration.

SUBJECTS AND METHODS

Twenty-three patients with strabismus acquired after binocular vision maturation were enrolled. Factors studied included duration of eye misalignment, age at treatment, pre-surgical strabismus type, pre-surgical diplopia, and pre-surgical capacity for binocularity. The restoration of macular binocular vision was evaluated between 1 and 3 years following successful eye re-alignment and was defined as 60 seconds of arc stereopsis or better on the Titmus circles and/or the Preschool Randot Stereoacuity test.

RESULTS

Sixteen of 23 (70%) or 7/23 (30%) of patients achieved macular binocular vision following successful surgical eye realignment using the Titmus circles versus the Preschool Randot Stereoacuity test. Patients with < or =12 months constant eye misalignment were more likely to achieve macular binocular vision following treatment than patients with >12 months constant eye misalignment.

CONCLUSIONS

Macular binocular vision continues to be susceptible to permanent loss in adult patients. Factors that are predictive of the restoration of macular binocular vision include duration of constant eye misalignment and the pre-surgical capacity for binocularity.

Botulinum toxin and the eye

Botulinum toxin in ophthalmology is used to reduce the function of the eyelid muscles in spasms or therapeutically. Therapeutic and diagnostic use in strabismus is also discussed, along with the controversial treatment of nystagmus.

Dissociated effects of botulinum toxin chemodenervation on ocular deviation and saccade dynamics in chronic lateral rectus palsy

AIM

Changes in saccade velocity/amplitude characteristics (main sequence) and attenuation of distance esotropia in response to botulinum toxin (BTX-A) chemodenervation of the antagonist medial rectus were studied in a group of nine patients with chronic lateral rectus palsy.

METHODS

Serial measurements of ocular deviation and infrared oculograms of saccadic eye movements to targets at 5 degrees-20 degrees of lateral gaze were made before injection and at 2, 4, 8, 16, and 20 weeks after injection.

RESULTS

At 2 weeks after injection, the ocular deviation changed by a mean of 34.5 prism dioptres and the 5 degrees and 10 degrees adduction saccades were significantly slowed (p < 0.02 Wilcoxon signed rank test). By the second examination, however, the adducting saccade peak velocity had returned to normal while the mean ocular deviation remained significantly changed (p = 0.01 Wilcoxon matched pairs). By 20 weeks the mean ocular deviation was not significantly different from that before injection (p = 0.14 matched pairs).

CONCLUSIONS

The ocular realignment caused by BTX-A may persist after saccadic function has been restored. This may be because toxin may have a more profound and long lasting effect on the orbital singly innervated fibres which are active tonically at rest to hold gaze whereas there is relative sparing of the additional motor units recruited during fast eye movements.

The long-term use of botulinum toxin for adult strabismus

PURPOSE

To characterize patients choosing repeated botulinum toxin injection as a treatment for their strabismus, and assess their demand for it over time (up to 8 years).

METHOD

Patients who had undergone at least eight injections were identified and their clinical records analyzed for diagnosis, demographic details, and demand for toxin injections with time. To establish any predictive variables, the details for these cases were compared with those of matched controls who had undergone fewer injections. Lastly, a questionnaire was mailed to research patients' views as to the indications and preferences for regular toxin injection as a method of treatment.

RESULTS

Ninety-five patients were identified (34 men, 61 women; median age 37 years), of whom 35 had consecutive exotropia and 16 had secondary exotropia. Other diagnoses represented were residual and primary deviations, restrictive exotropias, and oscillopsias. A trend of fewer injections over the attendance period was seen, and the only complication observed was upper lid ptosis in 1% of injections. Cases exhibited similar demographic composition to matched controls, but were more likely to have consecutive exotropia or secondary esotropia as a diagnosis. Univariate analysis showed evidence (p < 0.001) of an association between the number of previous operations and the odds of being a case. No evidence was found that cases and controls lived at differing distances from our hospital. The questionnaire found that 71% of patients stated appearance as the prime reason for seeking treatment, and 37% stated simplicity of toxin therapy as their reason for reattendance. Twenty-six percent of the patients were disillusioned with the results of previous surgery and preferred toxin therapy as a means of controlling their symptoms.

CONCLUSION

Botulinum toxin injection is an appropriate long-term treatment for some strabismus patients who choose not to undergo further surgery. A trend toward fewer injections with time was observed, and no adverse effects were associated with long-term treatment.

Results of a prospective randomized trial of botulinum toxin therapy in acute unilateral sixth nerve palsy

Forty-seven patients entered a prospective randomized trial to assess the effect of early botulinum neurotoxin A treatment to the ipsilateral antagonist medial rectus on the ultimate recovery rate of acute unilateral sixth nerve palsy. Twenty-two patients received injections and 25 acted as controls. The overall etiologies were microvascular (72.3%), unknown (17%), multiple sclerosis (6%), and one case each of central nervous system (CNS) sarcoidosis and basilar artery ectasia. Eighty-three percent of the patients entered the trial within 2 weeks of the onset of symptoms and 95.7% within 3 weeks. The controls had a final recovery rate of 20/25 (80%), and the injected group had a final recovery rate of 19/22 (86%). No serious side effects were encountered. We conclude that there is no evidence for a prophylactic effect of botulinum toxin in the group that we have studied.

Modern management of sixth nerve palsy

Between November 1982 and September 1991, 179 patients with unilateral or bilateral sixth nerve palsy were treated in the Botulinum Toxin Strabismus Clinic at Moorfields Eye Hospital. Indications for treatment included prophylaxis (as part of a prospective treatment trial), maintenance therapy, diagnosis and adjunct to surgical therapy. A management plan for established sixth nerve palsy based on the rational use of toxin and surgery is suggested.

Treatment of unilateral acute sixth-nerve palsy with botulinum toxin

We studied 29 consecutive patients with acute unilateral sixth-nerve palsy, who received botulinum toxin injection to the antagonist medial rectus muscle. The average interval between onset of palsy and treatment was 40 days and the mean follow-up from the last injection was 14 months. Before treatment, esotropia in the primary position ranged from 12 to 45 prism diopters and limitation to abduction in the affected eye ranged from -2 (approximately 15 degrees lateral to midline) to -6 (15 degrees nasal to midline). After treatment, 22 of 29 patients (76%) had complete recovery of motility as determined by version testing. Of the seven patients with a residual abduction deficit, two had fusion in the primary position, three had fusion with prismatic correction, and two patients required subsequent surgery. Botulinum toxin injection seems to be an effective treatment option in cases of acute unilateral sixth-nerve palsy.

Use of botulinum toxin in strabismus after retinal detachment surgery

Botulinum toxin was used to treat 20 patients with strabismus after retinal detachment surgery. Preinjection motility deviations ranged from 10 to 60 prism diopters (D). Postinjection deviations ranged from 0 to 20 prism D, with 75% being 10 D or less. Eighty-five percent achieved fusion that persisted, with 73% requiring only one or two injections. Only muscles in the eye that had undergone retinal reattachment surgery were injected. The average period of follow-up was 12 months. Complications were rare and all resolved spontaneously. Botulinum toxin appears to be useful as a primary treatment modality for persistent strabismus following retinal detachment surgery, possibly obviating the need for complicated strabismus surgery.

Early botulinum toxin treatment of acute sixth nerve palsy

Eight patients with total sixth nerve palsy were treated with botulinum toxin injection to the antagonist non-paretic medical rectus, within eight weeks of the onset of the palsy. Within a few days seven of the eight gained fusion without the necessity of a marked head turn, and none complained of confusing reversal of diplopia. The same seven recovered full function. The mean follow-up period after the last injection was 20 months. Seven palsies were the result of head trauma and one was due to cerebro-vascular disease. This preliminary report suggests that early botulinum toxin injection of patients with recent onset sixth nerve palsy is beneficial. Although all of the patients may possibly have recovered full lateral rectus function without treatment, the aetiologies of their palsies were of the type that frequently do no resolve. A randomised double-blind study is necessary more precisely to determine the effectiveness of this form of therapy.

Early and late botulinum toxin treatment of acute sixth nerve palsy

Ten patients with sixth nerve palsy were treated with botulinum toxin injection to the antagonist nonparetic medial rectus. All patients were followed for a minimum of 14 months after the last injection. Six patients were treated within eight weeks of the onset of the palsy. Within a few days five of the six gained fusion, without the necessity of a marked head turn and none complained of confusing reversal of diplopia. The same five recovered full function. Four patients with no medial rectus contracture on forced duction testing were treated six months or longer after the onset of the palsy and none recovered full function. One of the four patients was permanently over-corrected despite persistent weakness of the lateral rectus. This preliminary report suggests that early botulinum toxin injection of patients with recent onset (acute) sixth nerve palsy is beneficial. Since some patients may recover spontaneously a randomised double-blind study is necessary to more precisely determine the effectiveness of this form of therapy. Botulinum toxin does not appear to be effective in facilitating recovery in those cases with poor lateral rectus function six months or longer after the onset of the palsy, even when there is no contracture of the medial rectus.

The role of botulinum toxin in the management of sixth nerve palsy

Fifty-five patients with sixth nerve palsy have been treated with Botulinum toxin injection to the antagonist medial rectus, either in isolation or in combination with rectus muscle surgery. Forty of these patients (72 per cent) obtained significant benefit from injection at some stage in their management. Botulinum toxin has a major role in conjunction with transposition muscle surgery for the treatment of complete unrecovered sixth nerve palsy. In less severe paresis, a functional cure may be obtained in a significant number of cases with the use of Botulinum toxin alone, 37 per cent in this series. No serious complications were observed. In view of the safety of this procedure it is reasonable to consider an injection of Botulinum toxin in any adult patient with a persisting sixth nerve palsy.

Long-term results: botulinum for sixth nerve palsy

Eight patients with intracranial malignancies or vascular lesions and sixth nerve palsies were treated with botulinum toxin chemodenervation of the antagonist medial rectus muscle. Primary deviation ranged from 20 to 75 prism diopters (pd) of esotropia. Six were treated acutely (within 3 months of onset) and two, which demonstrated partial recovery of lateral rectus function but with residual esotropia and diplopia, were treated after 6 months. After a mean follow-up of 20.6 months, seven were diplopia-free with excellent rotations. Five had complete resolution of the esotropia and diplopia, with near complete recovery of abduction. One had 6 pd residual esotropia, while another, whose sixth nerve had been resected, required a modified Jensen procedure, resulting in full rotations. The single case of bilateral sixth nerve palsy had a functional improvement but was lost to follow-up. One patient had a vertical strabismus induced with the injection and had a gradual return of the esotropia.

Treatment of sixth nerve palsy in adults with combined botulinum toxin chemodenervation and surgery

This study reports the results of treating unrecovered sixth nerve palsy in adults with a combination of botulinum toxin and surgery. Twenty-two adults, 11 with unilateral and 11 with bilateral unrecovered sixth nerve palsy, were treated with injections of botulinum toxin to the contracted medial rectus followed by transposition surgery to the vertical rectus muscles. This management technique produced a satisfactory reduction in esotropia, averaging 46 prism diopters (PD), comparable with that achieved by conventional surgery in other series. The advantages of this form of treatment are discussed.

Treatment of anismus in intractable constipation with botulinum A toxin

In seven patients with anismus the striated sphincter muscle complex was selectively weakened by local injection of Clostridium botulinum type A toxin. Symptom scores improved significantly and correlated with a significant reduction in the maximum voluntary and canal squeeze pressure and a significant increase in the anorectal angle on straining. Botulinum A toxin seems to be promising treatment for some patients with anismus.

Botulinum toxin treatment of acute sixth and third nerve palsy

Thirty-four patients with acute sixth nerve palsy and nine patients with acute third nerve palsy were treated with botulinum toxin injection to the antagonist, nonparalytic horizontal rectus muscle. In a control group of 52 patients with acute sixth nerve palsy not treated with botulinum in the acute stage, only 16 (31%) recovered spontaneously and did not require surgery. Twenty-two of the 31 surviving patients who could be followed with acute sixth nerve palsy had lateral rectus recovery and surgery was avoided. Four required prisms in their glasses to obtain fusion. Nine patients developed chronic sixth nerve palsy and required surgery. In this group of acute sixth nerve palsy patients, eleven were bilateral. Seven of these eleven developed chronic sixth nerve paralysis, and required strabismus surgery. This suggests the prognosis for recovery following botulinum treatment in cases of acute bilateral sixth nerve palsy is not as good as in the unilateral cases. Botulinum toxin treatment does not appear to be effective in chronic sixth nerve palsy, as judged by results of treatment in one patient known to have a chronic palsy. Nine of nine patients with acute third nerve palsy had medial rectus recovery with fusion horizontally in primary gaze. None have required surgery. Only four of nine showed improvement in vertical rotations. The remaining five patients avoid vertical diplopia by a compensatory chin position. Botulinum toxin treatment of patients with acute sixth and third nerve palsy appears beneficial. However, since some in this group of patients may recover spontaneously, a randomized, double-blind study may be necessary to more definitively determine the effectiveness of this therapy.

Botulinum toxin therapy for squint

Four hundred and five patients have been treated with injections of Botulinum neurotoxin A to extraocular muscles in the Botulinum Toxin Clinic at Moorfields Eye Hospital from November 1982 until the present. The indications and outcome of therapy are described and discussed.