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

Botulinum Toxin Injection for the Treatment of Third, Fourth, and Sixth Nerve Palsy: A Meta-Analysis

The efficacy of botulinum toxin injection for the treatment of third, fourth, and sixth nerve palsy was evaluated. PubMed, Scopus, EMBASE, Web of Science, and Google Scholar databases were searched. Data about the duration of palsy (acute vs chronic), cause of the palsy, type of toxin used, mean dose, and other background characteristics were collected. Outcome variables were success rate (defined by alleviation of diplopia or reduction in eye deviation) and standardized mean difference of prism diopter and abduction deficit before and after injection. The Joanna Briggs Institute checklist was implemented for the risk of bias assessment. The analysis included 38 articles, comprising 643 patients. The overall treatment success rate in acute and chronic nerve palsy was 79% and 33%, respectively. The success rate was not significantly different between different subgroups of age, type of botulinum toxin, pre-injection prism diopter, etiology of the palsy, duration of follow-up, and mean dose of botulinum toxin injection. However, in both acute and chronic palsy, diabetes etiology was accompanied by the highest success rate. Overall symptomatic response to botulinum injection was 84% (95% CI: 67% to 96%), whereas functional response was observed in 64% (95% CI: 47% to 79%) of the patients. The odds ratio for the success rate of treatment of palsies with botulinum toxin versus expectant management was 2.67 (95% CI: 1.12 to 6.36) for acute palsy and 0.87 (95% CI: 0.17 to 4.42) for chronic palsy. Botulinum toxin can be used for the treatment of acute third, fourth, and sixth nerve palsy, especially in patients with acute palsy and more severe tropia. [J Pediatr Ophthalmol Strabismus. 2024;61(3):160-171.].

Therapy for nystagmus

Pathological forms of nystagmus and their visual consequences can be treated using pharmacological, optical, and surgical approaches. Acquired periodic alternating nystagmus improves following treatment with baclofen, and downbeat nystagmus may improve following treatment with aminopyridines. Gabapentin and memantine are helpful in reducing acquired pendular nystagmus due to multiple sclerosis. Ocular oscillations in oculopalatal tremor may also improve following treatment with memantine or gabapentin. The infantile nystagmus syndrome (INS) may have only a minor impact on vision if "foveation periods" are well developed, but symptomatic patients may benefit from treatment with gabapentin, memantine, or base-out prisms to induce convergence. Several surgical therapies are also reported to improve INS, but selection of the optimal treatment depends on careful evaluation of visual acuity and nystagmus intensity in various gaze positions. Electro-optical devices are a promising and novel approach for treating the visual consequences of acquired forms of nystagmus.

Nystagmus and saccadic intrusions

We review current concepts of nystagmus and saccadic oscillations, applying a pathophysiological approach. We begin by discussing how nystagmus may arise when the mechanisms that normally hold gaze steady are impaired. We then describe the clinical and laboratory evaluation of patients with ocular oscillations. Next, we systematically review the features of nystagmus arising from peripheral and central vestibular disorders, nystagmus due to an abnormal gaze-holding mechanism (neural integrator), and nystagmus occurring when vision is compromised. We then discuss forms of nystagmus for which the pathogenesis is not well understood, including acquired pendular nystagmus and congenital forms of nystagmus. We then summarize the spectrum of saccadic disorders that disrupt steady gaze, from intrusions to flutter and opsoclonus. Finally, we review current treatment options for nystagmus and saccadic oscillations, including drugs, surgery, and optical methods. Examples of each type of nystagmus are provided in the form of figures.

Unaugmented Vertical Muscle Transposition Surgery for Chronic Sixth Nerve Paralysis

INTRODUCTION

Chronic sixth nerve palsy can cause incapacitating diplopia requiring vertical muscle transposition surgery. Augmentation of surgery, with lateral fixation sutures, medial rectus recession or botulinum toxin injection, is associated with an increased risk of complications.

PURPOSE

Our aim was to evaluate the efficacy and safety of unaugmented full-tendon vertical rectus transposition in chronic sixth nerve paralysis.

METHODS

Longitudinal study of 21 patients with chronic sixth nerve paralysis of longer than 6 months duration, who underwent superior and inferior recti transposition surgery without medial rectus recession or botulinum toxin injection. Details of surgery, preoperative and postoperative examinations including full orthoptic examination were obtained from an electronic database. Outcomes included the change in angle of deviation, the requirement for further surgery to the medial rectus and postoperative improvement in diplopia. SPSS software (Version 12.0.1, SPSS Inc. Chicago, IL) was used to summarize baseline characteristics and outcomes and to compare preoperative and postoperative deviation (paired t-test).

RESULTS

Twenty-one patients (10 (47.6%) men and 11 (52.4%) women) with a mean age of 41 years (range 4 to 74 years) were operated in the period between April 1998 and November 2000. Eighteen patients had unilateral and three had bilateral acquired sixth nerve palsy. Nineteen patients required unilateral surgery and two had bilateral transposition procedures. In patients with unilateral sixth nerve palsy, mean esotropia in primary position before surgery was 46.7 prism-diopters (PD) (95% CI 35.9-57.4 PD) and improved to 14.6 PD after surgery (95% CI 6.4-22.7 PD). The angle of deviation was significantly reduced by an average of 32.1 PD (p < 0.001, paired t-test; 95% CI 22.6-41.6 PD). Over all, 10 patients (55.6%) had a well-controlled esophoria with a postoperative alignment of within 10 PD of orthophoria without diplopia in the primary position, for distance and near. A further six patients (28.6%) required additional medial rectus recessions to achieve success. The only complication observed was slippage of the inferior rectus in one patient (4.2%), who consequently required further surgery.

CONCLUSION

Botulinum toxin infiltration of the medial rectus in vertical rectus transposition surgery may be unnecessary, incurring cost, additional attendances and interventions for patients. Less than a third of all patients in our series required additional medial rectus recession later.

Botulinum Toxin a Therapy for Medial Rectus Injury during Endoscopic Sinus Surgery

Background

Although the use of endoscopes and image guidance provide some safeguards, motility complications from orbital injury during endoscopic sinus surgery still pose a significant concern and can provide a therapeutic challenge.

Methods

We present the case of a 40-year-old woman with strabismus secondary to an iatrogenic injury to the medial rectus muscle during endoscopic sinus surgery.

Results

Permanent resolution of diplopia was achieved with botulinum toxin A injection into the lateral rectus muscle without the need for surgical intervention.

Conclusion

Botulinum toxin A should be considered as a first-line early therapeutic option for cases of iatrogenically induced strabismus after endoscopic sinus surgery when complete transection or entrapment is not present.

Delayed lateral rectus palsy following resection of a pineal cyst in sitting position: direct or indirect compressive phenomenon?

A rare case of delayed lateral rectus palsy in a patient following resection of a pineal lesion in the sitting position is presented. Postoperative pneumocephalus is common following craniospinal surgical intervention in the sitting position. The sixth cranial nerve is frequently injured because of its prolonged intracranial course. A 13-year-old girl was evaluated for unremitting headaches. No focal deficits were demonstrated on neurological examination. Magnetic resonance imaging revealed a cystlike pineal region mass with peripheral enhancement following intravenous contrast administration. A supracerebellar infratentorial craniotomy was performed in the sitting position, and complete resection of the lesion was achieved. Her postoperative course was complicated by sixth nerve palsy on the third postoperative day. Her symptoms improved with conservative management. The occurrence of sixth cranial nerve palsy secondary to pneumocephalus is a rare entity. Even rarer is the report of this anomaly following craniotomy in the sitting position. This patient's symptoms manifested in a delayed fashion. Although uncommon, this complication should be considered in patients undergoing cranial or spinal surgical interventions in this position.

Basic immunological aspects of botulinum toxin therapy

Previous studies in this laboratory had mapped the immune recognition profile of the regions recognized antibodies (Abs) and by T cells on the protective H(C) domain (C-terminal fragment corresponding to residues 855-1296 of the heavy chain) of botulinum neurotoxin serotype A (BoNT/A). The localization of these regions has several potential applications and has provided a basis for the understanding of immunoresistance to treatment. We briefly outline these localized regions and discuss the impact of these findings on the immunotherapeutic applications of BoNT/A. Immunoresistance to toxin therapy can appear in some patients after a few injections with the toxin. Our epitope mapping studies have shown that several factors can influence the immune response to the toxin. These factors include dose, duration of treatment, frequency of immunization, and quality of the toxin. The immune response to the whole toxin is under genetic control, and the response to each epitope is under separate genetic control. Therefore, the appearance of blocking Abs (i.e., immunoresistance) in patients might be controlled by the major histocompatability of the host. Once a patient becomes immunoresistant to one toxin then switching to another toxin will most often be of limited and short-lived benefit, because the patient becomes rapidly immunoresistant to the second toxin. Finally, because of the considerable structural homology between tetanus neurotoxin (TeNT) and BoNTs, it is possible, although not certain, that a prior active immune response to TeNT might play some role in the early appearance on anti-BoNT Abs in some patients.

Paralytic strabismus

In the past 12 months there have been many interesting publications on paralytic strabismus. Many investigators have reported on various imaging techniques helping both the clinician and the basic scientist better evaluate the causes and effects of paralytic strabismus on the extraocular muscle environment. Some interesting cases of neurologic and systemic associations have also been reported, including a unilateral pupil-sparing third nerve paralysis developing after the use of sildenafil citrate (Viagra; Pfizer, New York, New York). Advances in genetics are now helping us further understand complex entities such as progressive external ophthalmoparesis and congenital fibrosis syndrome. At the other end of the spectrum, colleagues are reporting clinical findings to help specify the diagnosis of conditions as diverse as degenerative ataxic disorders and masked bilateral superior oblique muscle paresis. Unfortunately, there were very few papers on proven new effective surgical techniques for the treatment of paralytic strabismus this year. Finally, to help clarify terminology, and when at all possible depending on the reports reviewed, the following nomenclature will be used in this paper: paralysis--complete loss of function of a muscle or group of muscles innervated by a specified (when applicable) cranial nerve or branch; paresis--incomplete loss of function; and palsy--when the authors failed to specify the degree of weakness.